Academic literature on the topic 'Bacteriocins. Staphylococcus aureus'

Enterococcus gallinarum strains isolated from some Nigerian fermented foods were found to produce bacteriocins. The bacteriocins had a broad spectrum of activity against both Gram-positive and negative bacteria. The effects of the bacteriocins and bacteriocinogenic organ- isms on Staphylococcus aureus infections in rats were evaluated. Sprague-Dawley rats were infected with S. aureus MTCC 737 and treated with E. gallinarum T71 and different concentrations of the bacteriocins from E. gallinarum W211 and T71. Staphylococcus aureus infection caused significant upregulation of aspartate aminotransferase and alanine aminotransferase levels in sera of the infected rats. Moreover, gelatin zymography revealed that infected gastric tissues showed elevated matrix metalloproteinase-9 activity. Bacteriocin treatments reduced the MMP-9 activity and inhibited the expressions of both Tumour Necrosis Factor Alpha (TNF-α) and Interleukin-1 Beta (IL-1β) dose dependently, pointing to a potential role of the bacteriocins in attenuating inflammatory responses to Staphylococcus aureus infec- tion. Gastric and GIT damage caused by staphylococcal infection were reduced in the Enterococcus gallinarum T71 and bacteriocin-treated groups also dose dependently. We conclude that these bacteriocins may have useful biomedical applications.

ABSTRACT Staphylococcus aureus is an important pathogen implicated in various diseases, including staphylococcal food poisoning. Bacteriocins are considered safe and effective antimicrobial substances for the prevention of the growth of pathogenic bacteria. In this article, we describe the purification and characterization of pasteuricin, a novel bacteriocin produced by Staphylococcus pasteuri RSP-1. A cell-free supernatant of S. pasteuri RSP-1 exerted strong antimicrobial activity against staphylococci, including methicillin-resistant S. aureus (MRSA), and gram-positive bacteria. The loss of antimicrobial activity upon treatment with proteolytic enzymes confirmed the proteinaceous nature of pasteuricin. A rapid and pronounced bactericidal effect of pasteuricin was confirmed by a live-dead bacterial viability assay. To our knowledge, pasteuricin is the first reported S. pasteuri bacteriocin that inhibits S. aureus. Because pasteuricin is characterized by strong antimicrobial activity and high stability, it has potential as an alternative antimicrobial agent to antibiotics.

Staphylococcus aureus (S. aureus) is one of the well-known agents causing atopic dermatitis (AD) in susceptible individuals, and Staphylococcus epidermidis (S. epidermidis) produces class I thermostable bacteriocins that can selectively kill S. aureus, suggesting protective roles against AD. There is a large need for developing precise therapies only to target S. aureus and not to harm the beneficial microbiome. On the agar well diffusion assay, live planktonic S. epidermidis showed clear zones of inhibition of S. aureus growth, but heat-killed cells and cell-free supernatants did not show this. These results would lead us to hypothesize that cytoplasmic bacteriocin from S. epidermidis will be a promising agent to inhibit S. aureus growth. Therefore, we have extracted a novel thermolabile cytoplasmic bacteriocin from S. epidermidis using trichloroactic acid (TCA)/acetone precipitation method after cell lysis with a SDS-containing buffer. These bacteriocin selectively exhibited antimicrobial activity against S. aureus and methicillin-resistance Staphylococcus aureus (MRSA), presenting no active actions against S. epidermidis, E. coli, and Salmonella Typhimurium. The extracted cytoplasmic bacteriocin compounds revealed several diffuse bands of approximately 40–70 kDa by SDS-PAGE. These findings suggest that these cytoplasmic bacteriocin compounds would be a great potential means for S. aureus growth inhibition and topical AD treatment.

Staphylococcus aureus is an important pathogen of both humans and animals, implicated in a wide range of infections. The emergence of antibiotic resistance has resulted in S. aureus strains that are resistant to almost all available antibiotics, making treatment a clinical challenge. Development of novel antimicrobial approaches is now a priority worldwide. Bacteria produce a range of antimicrobial peptides; the most diverse of these being bacteriocins. Bacteriocins are ribosomally synthesised peptides, displaying potent antimicrobial activity usually against bacteria phylogenetically related to the producer strain. Several bacteriocins have been isolated from commensal coagulase-negative staphylococci, many of which display inhibitory activity against S. aureus in vitro and in vivo. The ability of these bacteriocins to target biofilm formation and their novel mechanisms of action with efficacy against antibiotic-resistant bacteria make them strong candidates as novel therapeutic antimicrobials. The use of genome-mining tools will help to advance identification and classification of bacteriocins. This review discusses the staphylococcal-derived antimicrobial peptides displaying promise as novel treatments for S. aureus infections.

Seventeen staphylococci isolated from 54 Slovak local lump cheeses made from ewes’ milk were taxonomically allotted to five species and three clusters/groups involving the following species: Staphylococcus aureus (5 strains), Staphylococcus xylosus (3 strains), Staphylococcus equorum (one strain) Staphylococcus succinus (5 strains) and Staphylococcus simulans (3 strains). Five different species were determined. The aim of the study follows two lines: basic research in connection with staphylococci, and further possible application of the bacteriocins. Identified staphylococci were mostly susceptible to antibiotics (10 out of 14 antibiotics). Strains showed γ-hemolysis (meaning they did not form hemolysis) except for S. aureus SAOS1/1 strain, which formed β-hemolysis. S. aureus SAOS1/1 strain was also DNase positive as did S. aureus SAOS5/2 and SAOS51/3. The other staphylococci were DNase negative. S. aureus SAOS1/1 and SAOS51/3 showed biofilm formation on Congo red agar. However, using quantitative plate assay, 12 strains out of 17 showed low-grade biofilm formation (0.1 ≤ A570 < 1), while five strains did not form biofilm (A570 < 0.1). The growth of all strains, including those strains resistant to enterocins, was inhibited by nisin and gallidermin, with high inhibition activity resulting in the inhibition zone in size from 1600 up to 102,400 AU/mL (arbitrary unit per milliliter). This study contributes to microbiota colonization associated with raw ewe’s milk lump cheeses; it also indicates bacteriocin treatment benefit, which can be used in prevention and/or elimination of staphylococci.

Bacteriocins are ribosomally synthesized antibacterial peptides which have the potential to be used as natural food preservatives as well as alternative to antibiotics. Here, we report the production of bacteriocin-like inhibitory substances (BLIS) from the indigenous strains of Bacillus thuringiensis. Deferred antagonism bacteriocin assay and agar well diffusion methods suggested that several of the tested strains have high levels of bacteriocin-like activity against the common food-borne pathogens, Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus. These bacteriocins are generally produced at the mid-logarithmic phase of growth with optimum temperature of 37 ºC, pH-7.0 and 24 h of incubation. Heat stability assay demonstrated that the bacteriocins produced from the strains are highly heat stable and can retain activity up to 100 ºC. Our study suggests that these bacteriocins may be potential candidates for use as biodegradable natural food preservatives and alternative antimicrobial agents to solve the increasing trends of problems of antibiotic resistance.Bangladesh Pharmaceutical Journal 18(2): 149-156, 2015

Staphylococcus aureus 4185 was previously shown to produce at least two bacteriocins. One of them is encoded by pRJ101. To detect the bacteriocin-encoding gene cluster, an ~9160 kb region of pRJ101 was sequenced. In silico analyses identified 10 genes (aclX, aclB, aclI, aclT, aclC, aclD, aclA, aclF, aclG and aclH) that might be involved in the production of a novel cyclic bacteriocin named aureocyclicin 4185. The organization of these genes was quite similar to that of the gene cluster responsible for carnocyclin A production and immunity. Four putative proteins encoded by these genes (AclT, AclC, AclD and AclA) also exhibited similarity to proteins encoded by cyclic bacteriocin gene clusters. Mutants derived from insertion of Tn917-lac into aclC, aclF, aclH and aclX were affected in bacteriocin production and growth. AclX is a 205 aa putative protein not encoded by the gene clusters of other cyclic bacteriocins. AclX exhibits 50 % similarity to a permease and has five putative membrane-spanning domains. Transcription analyses suggested that aclX is part of the aureocyclicin 4185 gene cluster, encoding a protein required for bacteriocin production. The aclA gene is the structural gene of aureocyclicin 4185, which shows 65 % similarity to garvicin ML. AclA is proposed to be cleaved off, generating a mature peptide with a predicted M r of 5607 Da (60 aa). By homology modelling, AclA presents four α-helices, like carnocyclin A. AclA could not be found at detectable levels in the culture supernatant of a strain carrying only pRJ101. To our knowledge, this is the first report of a cyclic bacteriocin gene cluster in the genus Staphylococcus.

Biofilms are microbial communities that cause serious chronic infections in the environment by enhancing antimicrobial resistance. Bacteria in the biofilm can be up to a thousand times more resistant to antibiotics than the same bacteria circulating in a planktonic state. The emergence of antibiotic-resistant microorganism has led to the exploration of different therapeutic agents like ribosomally synthesized microorganism peptides referred to as bacteriocins. In this study, bacteriocin producing bacteria Pseudomonas aeruginosa isolated from a soil sample. It was found to be effective against Methicillin-resistant Staphylococcus aureus (MRSA). Furthermore the bacteriocin was partial purified by ammonium sulfate, the precipitate has highly effective against MRSA (400AU/mL). MRSA cells were treated with precipitated culture supernatant of P. aeruginosa TA6 was analyzed by FT-IR. The treated and untreated MRSA showed band variations at 682.59 and 3442.15cm-1 corresponding to the alkyl and amide group respectively. Bacteriocin showed marked inhibition activity against the biofilm of MRSA. About 0.05% and 0.02% attachment of biofilm was observed in the presence of 1X MIC (10 μg/mL) and 2X MIC (20 g/mL) respectively. Our results recommend that bacteriocins that make stable pores on biofilm cells are extremely potent for the treatment of MRSA biofilm infections.

Lactobacillus spp. are known to have many health benefits and are mostly used as probiotics. They can cause inhibition of certain micro-organisms by the reduction of pH due to production of lactic acid, hydrogen peroxide and antimicrobial compounds such as bacteriocins. The antibacterial; activity of Lactobacillus spp. Against Staphylococcus aureus was evaluated using agar well diffusion method. Three raw goat milk samples were pooled together, serially diluted, cultured on MRS (De Man, Rogosa, Sharpe) Agar, and purified. Four Lactobacillus species were isolated and identified by biochemical tests as L. lactis, L. plantarum, L. Casei and L. Fermentum. Antibacterial activity of the four isolates against the test organism, Staphylococcus aureus, was determined by agar well diffusion method following the extraction of crude and precipitated bacteriocin from the isolates. All the isolates produced antagonistic effects against the test organism with maximum zones of growth inhibition produced by precipitated bacteriocin [14.0mm (L. casei) to 16.0mm (L. lactis)] whereas minimum zones of growth inhibition was produced by crude bacteriocin [8.0mm (L. casei) to 11.0mm (L. lactis)]. The results obtained confirmed that the four Lactobacilli isolated have growth inhibitory effects against Staphylococcus aureus and can therefore serve as important probiotic organism. It also goes further to show the importance of Lactobacillus bacteriocins as food bio-preservatives. This therefore justifies an in-depth investigation for the identification and application of these organisms in generating alternative antibacterial therapies for human and animal diseases to counter the problem of bacteria antibiotic resistance in recent years.

Fundação de Apoio a Pesquisa e à Inovação Tecnológica do Estado de Sergipe - FAPITEC/SE
Staphylococcus aureus has been considered a major public health problem worldwide due mainly to the ability to develop resistance to antibiotics. The prevalence of methicillin resistant strains of S. aureus (MRSA) in both hospital and community settings has been increasing, with cases of infections and deaths reported in healthy children and adults. Bacteriocins have been identified as promising alternatives for the control of this pathogen. However, besides the therapeutic use of these peptides still not approved, some studies indicate the possibility of selection of resistant strains. Therefore, prior to the therapeutic use of bacteriocins, studies must be carried out to understand the effect that bacteriocin may have on the selection of resistant strains to avoid the current problem with lineages resistant to traditional antibiotics. In view of the above, the objective of this study was to verify the antimicrobial activity of nisin against strains of MRSA and MSSA isolated from the oropharynx of health professionals and verify the selection of strains resistant to bacteriocin. For the genotypic characterization of the MRSA and MSSA strains, the nucA, LuckPV, mecA and mecC genes were tested. The MSSA lines were positive for amplification of the nucA gene only, confirming the identification of genus and species of these strains. For MRSA strains, the only gene that was not detected was mecC, confirming the methicillin resistance phenotype and that these strains are of human origin and of community environments. The results obtained by the agar diffusion test demonstrated that 80% of the MSSA strains (n = 30) were inhibited by nisin and only one MRSA line (n = 6) showed no sensitivity to bacteriocin. The MIC of MSSA strains ranged from 97.7 to 1250 IU / mL and from MRSA strains of 937.50 to 5000 IU / mL. The DBM for MSSA strains varied from 97.7 IU / mL to values greater than 50,000 IU / mL, and for MRSA, this variation was between 5000 IU / mL at values greater than 10,000 IU / mL depending on the lineage. For most lineages DBM was higher than MIC, showing that the effect of bacteriocin depends on bacteriocin concentration: low concentrations exert bacteriostatic effect and high concentrations bactericidal effect. The addition of increasing concentrations of the bacteriocin to the BHI medium generally resulted in the increase in the lag phase and decrease in the specific growth rate and maximal DO reached by the MSSA and MRSA cultures. MSSA and MRSA strains were transferred for approximately 30 generations in the presence of bacteriocin and a decrease in sensitivity was observed with a consequent increase in nisin MIC for all strains tested. The bacteriocin resistance phenotype has been shown to be a stable trait for these strains and may be associated with a genetic factor. It has also been observed that the use of nisin may trigger cross-resistance to some antibiotics. The results obtained demonstrated that nisin is efficient in controlling the growth of MSSA and MRSA. However, the fact that these lines demonstrate resistance to bacteriocin after transfer in the presence of the same indicates the need to develop strategies to avoid in the future the current problem of resistance to antibiotics. The best way to use bacteriocins therapeutically is to suggest that it is in combination with traditional antibiotics.
Staphylococcus aureus têm sido considerado um dos maiores problemas de saúde pública a nível mundial devido, principalmente, a habilidade de desenvolver resistência a antibióticos. A prevalência de linhagens de S. aureus resistentes a meticilina (MRSA) tanto em ambiente hospitalar quanto em ambientes comunitários têm aumentado, sendo descritos casos de infecções e relatos de mortes em crianças e adultos saudáveis. Bacteriocinas tem sido apontadas como alternativas promissoras para o controle deste patógeno. Entretanto, além do uso terapêutico destes peptídeos ainda não ser aprovado, alguns estudos indicam a possibilidade de seleção de linhagens resistentes. Portanto, antes do uso terapêutico de bacteriocinas, estudos precisam ser realizados para o entendimento do efeito que a bacteriocina possa ter na seleção de linhagens resistentes para evitar o problema da atualidade com linhagens resistentes aos antibióticos tradicionais. Diante do exposto, o objetivo deste trabalho foi verificar a atividade antimicrobiana da nisina contra cepas de MRSA e MSSA isoladas da orofaringe de profissionais da área de saúde e verificar a seleção de linhagens resistentes à bacteriocina. Para a caracterização genotípica das linhagens MRSA e MSSA, foram testados os genes nucA, LuckPV, mecA e mecC. As linhagens MSSA foram positivas para amplificação apenas do gene nucA, confirmando a identificação de gênero e espécie destas linhagens. Para as linhagens MRSA, o único gene que não foi detectado foi o meC, confirmando o fenótipo de resistência a meticilina e que estas linhagens são de origem humana e de ambientes comunitários. Os resultados obtidos pelo teste de difusão em ágar demonstraram que 80% das linhagens MSSA (n=30) foram inibidas pela nisina e apenas uma linhagem MRSA (n=6) não apresentou sensibilidade à bacteriocina. A CIM das linhagens de MSSA variou de 97,7 a 1250UI/mL e das linhagens MRSA de 937,50 a 5000 UI/mL. A DBM para as linhagens de MSSA variou de 97,7 UI/mL a valores superiores a 50000 UI/mL, e para MRSA esta variação ficou entre 5000 UI/mL a valores maiores que 10000 UI/mL dependendo da linhagem. Para a maioria das linhagens a DBM foi maior que a CIM, mostrando que o efeito da bacteriocina depende da concentração da mesma: baixas concentrações exercem efeito bacteriostático e altas concentrações efeito bactericida. A adição de concentrações crescentes da bacteriocina ao meio BHI resultaram, de maneira geral, no aumento da fase lag e diminuição da velocidade específica de crescimento e DO máxima atingida pelas culturas MSSA e MRSA. Linhagens de MSSA e MRSA foram transferidas por aproximadamente 30 gerações na presença da bacteriocina e foi observada diminuição na sensibilidade com consequente aumento da CIM da nisina para todas as linhagens testadas. O fenótipo de resistência à bacteriocina demonstrou ser uma característica estável para estas linhagens, podendo estar associado a um fator genético. Foi observado também que a utilização da nisina pode desencadear resistência cruzada a alguns antibióticos. Os resultados obtidos demonstraram que a nisina é eficiente em controlar o crescimento de MSSA e MRSA. Entretanto, o fato destas linhagens demonstrarem resistência a bacteriocina após transferência na presença da mesma indica a necessidade de desenvolver estratégias para evitar no futuro o problema atual de resistência a antibióticos. A melhor maneira de usar bacteriocinas terapeuticamente sugere-se que seja em combinação com antibióticos tradicionais.
São Cristóvão, SE

Orientador: Ary Fernandes Júnior
Banca: Maria de Lourdes Ribeiro da Cunha
Banca: Rosemeire Cristina Lianhri Rodrigues Pietro
Resumo: A pesquisa por novas drogas antimicrobianas tem aumentado, seja na indústria farmacêutica e também na indústria de alimentos. Isso acontece devido ao aumento no número de bactérias resistentes aos antimicrobianos, e a busca por conservantes alimentares que possibilitem o aumento na vida de prateleira dos alimentos. O interesse por alimentos mais saudáveis, especialmente aqueles sem adição ou com quantidades reduzidas de aditivos químicos, vem aumentando constantemente. Os produtos naturais, especialmente os de origem microbiana e de espécies vegetais são considerados fontes importantes para o desenvolvimento de novos antimicrobianos. O trabalho teve como objetivo avaliar a ação antibacteriana de óleos essenciais de plantas, seus compostos majoritários, a ação antibacteriana da nisina (bacteriocina produzida por Lactococcus lactis) e a ação antibacteriana da combinação desses compostos majoritários com a nisina em meio de cultura e no leite. Inicialmente foi avaliado o potencial antibacteriano com a determinação da concentração inibitória mínima (CIM) dos óleos essenciais de orégano (Origanum vulgare), tomilho (Tymus vulgaris), cravo da índia (Syzygium aromaticum) e canela (Cinnamomun zeylanicum) e respectivos compostos majoritários carvacrol, timol, eugenol e cinamaldeído, e da nisina sobre cepas padrões ATCC de bactérias de importância na área de alimentos: Staphylococcus aureus ATCC 25923, Escherichia coli O157 ATCC 43895, Salmonella Enteritidis ATCC 13076, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 10100, Listeria monocytogenes ATCC 15313, Aeromonas hydrophila ATCC 7966 e Lactobacillus rhamnosus ATCC 9595 utilizando a metodologia da microdiluição em meio de Mueller Hinton Caldo (MHC). Em alguns casos a atividade inibidora dos óleos essenciais foi maior que a atividade do seu respectivo composto isolado, e em outros a atividade inibidora do composto isolado foi maior que ...
Abstract: The research for new antimicrobial drugs has increased in a pharmaceutical industry as well as in the food industry. This happens due to the increase in the number of bacteria resistant to antimicrobial agents, and the search for food preservatives which make possible the increase in the shelf life of foods. The interest in healthier foods, especially those without addition or with reduced amounts of chemical additives is increasing constantly. The natural products, especially of microbial origin and plant species are considered important sources for the development of new antimicrobial. This study purpose to evaluate the antibacterial activity of essential oils from plants, their major compounds, the antibacterial action of nisin (bacteriocin produced by Lactococcus lactis) and the antibacterial activity of the combination of these major compounds with nisin in culture medium and in milk. First was evaluated antimicrobial activity with determination of minimum inhibitory concentration (MIC) of the essential oils of oregano (Origanum vulgare), thyme (Tymus vulgaris), clove (Syzygium aromaticum) and cinnamon (Cinnamomun zeylanicum) and their major compounds carvacrol , thymol, eugenol and cinnamaldehyde, and nisin on ATCC strains of bacteria of importance in the food industry: Staphylococcus aureus ATCC 25923, Escherichia coli O157 ATCC 43895, Salmonella Enteritidis ATCC 13076, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 10100, Listeria monocytogenes ATCC 15313, Aeromonas hydrophila ATCC 7966 and Lactobacillus rhamnosus ATCC 9595 using the microdilution method in Mueller Hinton Broth medium (MHC). In some cases the inhibitory activity of essential oils has been higher than the activity of the respective isolated compound, and in others the inhibitory activity of the compound isolate was greater than that of the respective essential oils, whereas nisin was active against Gram-positive bacteria and a lower inhibitory ...
Mestre

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A pesquisa por novas drogas antimicrobianas tem aumentado, seja na indústria farmacêutica e também na indústria de alimentos. Isso acontece devido ao aumento no número de bactérias resistentes aos antimicrobianos, e a busca por conservantes alimentares que possibilitem o aumento na vida de prateleira dos alimentos. O interesse por alimentos mais saudáveis, especialmente aqueles sem adição ou com quantidades reduzidas de aditivos químicos, vem aumentando constantemente. Os produtos naturais, especialmente os de origem microbiana e de espécies vegetais são considerados fontes importantes para o desenvolvimento de novos antimicrobianos. O trabalho teve como objetivo avaliar a ação antibacteriana de óleos essenciais de plantas, seus compostos majoritários, a ação antibacteriana da nisina (bacteriocina produzida por Lactococcus lactis) e a ação antibacteriana da combinação desses compostos majoritários com a nisina em meio de cultura e no leite. Inicialmente foi avaliado o potencial antibacteriano com a determinação da concentração inibitória mínima (CIM) dos óleos essenciais de orégano (Origanum vulgare), tomilho (Tymus vulgaris), cravo da índia (Syzygium aromaticum) e canela (Cinnamomun zeylanicum) e respectivos compostos majoritários carvacrol, timol, eugenol e cinamaldeído, e da nisina sobre cepas padrões ATCC de bactérias de importância na área de alimentos: Staphylococcus aureus ATCC 25923, Escherichia coli O157 ATCC 43895, Salmonella Enteritidis ATCC 13076, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 10100, Listeria monocytogenes ATCC 15313, Aeromonas hydrophila ATCC 7966 e Lactobacillus rhamnosus ATCC 9595 utilizando a metodologia da microdiluição em meio de Mueller Hinton Caldo (MHC). Em alguns casos a atividade inibidora dos óleos essenciais foi maior que a atividade do seu respectivo composto isolado, e em outros a atividade inibidora do composto isolado foi maior que ...
The research for new antimicrobial drugs has increased in a pharmaceutical industry as well as in the food industry. This happens due to the increase in the number of bacteria resistant to antimicrobial agents, and the search for food preservatives which make possible the increase in the shelf life of foods. The interest in healthier foods, especially those without addition or with reduced amounts of chemical additives is increasing constantly. The natural products, especially of microbial origin and plant species are considered important sources for the development of new antimicrobial. This study purpose to evaluate the antibacterial activity of essential oils from plants, their major compounds, the antibacterial action of nisin (bacteriocin produced by Lactococcus lactis) and the antibacterial activity of the combination of these major compounds with nisin in culture medium and in milk. First was evaluated antimicrobial activity with determination of minimum inhibitory concentration (MIC) of the essential oils of oregano (Origanum vulgare), thyme (Tymus vulgaris), clove (Syzygium aromaticum) and cinnamon (Cinnamomun zeylanicum) and their major compounds carvacrol , thymol, eugenol and cinnamaldehyde, and nisin on ATCC strains of bacteria of importance in the food industry: Staphylococcus aureus ATCC 25923, Escherichia coli O157 ATCC 43895, Salmonella Enteritidis ATCC 13076, Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 10100, Listeria monocytogenes ATCC 15313, Aeromonas hydrophila ATCC 7966 and Lactobacillus rhamnosus ATCC 9595 using the microdilution method in Mueller Hinton Broth medium (MHC). In some cases the inhibitory activity of essential oils has been higher than the activity of the respective isolated compound, and in others the inhibitory activity of the compound isolate was greater than that of the respective essential oils, whereas nisin was active against Gram-positive bacteria and a lower inhibitory ...

Orientadores: Arnaldo Yoshiteru Kuaye, Izildinha Moreno
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: A biopreservação é uma técnica utilizada para estender a vida útil e aumentar a segurança dos alimentos por meio do emprego de microbiota protetora e/ou seus peptídeos antimicrobianos. O objetivo deste trabalho foi avaliar a atividade antimicrobiana de culturas produtoras de bacteriocinas sobre alguns patógenos Gram-positivos de ocorrência comum em produtos lácteos. As culturas bacteriocinogênicas Lactococcus lactis subsp. Lactis ATCC 11454, Lactobacillus plantarum ALC 01 e Enterococcus faecium FAIR-E 198 apresentaram comportamento distinto em relação à produção de bacteriocinas quando inoculadas em caldo MRS e em leite desnatado reconstituído (LDR) a 10%. Na avaliação do espectro de ação antimicrobiano pelo método de difusão em ágar por inoculação em poços, as bacteriocinas produzidas por Lb. plantarum ALC 01 e E. faecium FAIR-E 198 apresentaram atividade inibitória apenas sobre as linhagens de Listeria monocytogenes, já a nisina produzida por Lc. lactis subsp. lactis ATCC 11454 demonstrou espectro de ação mais amplo, porém com menor atividade que as demais culturas bacteriocinogênicas. Na avaliação da compatibilidade de desenvolvimento associativo com fermentos lácticos comerciais, somente Lc. lactis subsp. lactis ATCC 11454 apresentou atividade (halo de 6mm) sobre as linhagens constituintes de ambos os fermentos lácticos avaliados. A determinação da atividade acidificante foi realizada em LDR 10% após 8 e 24h de incubação a 35ºC; a adição de 0,1% e de 0,5% das culturas bacteriocinogênicas não afetou significativamente a capacidade de acidificação dos fermentos lácticos. Além disso, observou-se que o desenvolvimento associativo dos fermentos lácticos com Lb. Plantarum ALC 01 e E. faecium FAIR-E 198, em ambas as concentrações, proporcionou significativo aumento da atividade das bacteriocinas destas culturas, enquanto que a atividade da nisina de Lc. lactis subsp. lactis ATCC 11454 foi suprimida. A atividade de aminopeptidases foi determinada após desenvolvimento das culturas lácticas em caldo MRS, Lb. Plantarum ALC 01 apresentou as maiores atividades. Também foi analisado o comportamento de patógenos Gram-positivos durante desenvolvimento associativo com as culturas produtoras de bacteriocinas e fermento láctico em LDR 10% a 35ºC por 48h. Lb. plantarum ALC 01 e E. faecium FAIR-E 198 não influenciaram significativamente o desenvolvimento de Bacillus cereus K1-B041 e de Staphylococcus aureus ATCC 27154 durante as primeiras 24h de incubação a 35ºC, contudo apresentaram forte ação inibitória sobre L monocytogenes Scott A. Já Lc. lactis subsp. lactis ATCC 11454 afetou o desenvolvimento de todos os patógenos apenas durante as primeiras 12h de incubação. O fermento láctico demonstrou significativa ação inibitória sobre B. cereus K1-B041 (>7,37 log UFC/ml) e L monocytogenes Scott A (>6,26 log UFC/ml). Em queijo Minas Frescal, não foi observada diferença significativa entre a ação das culturas bacteriocinogênicas e o fermento láctico sobre L. monocytogenes Scott A e S. aureus ATCC 27154. B. cereus K1-B041 demonstrou susceptibilidade a Lb. plantarum ALC 01 e E. faecium FAIR-E 198 após 7 dias. Pelo método de diluição crítica não foi detectada atividade de bacteriocina nos queijos durante os 21 dias de estocagem a 8 ± 1ºC. A adição das culturas produtoras de bacteriocinas como adjuntas ao queijo Minas Frescal não promoveu alteração no pH e na acidez, contudo Lb. plantarum ALC 01 e E. faecium FAIR-E 198 promoveram aumento da proteólise primária e secundária. Embora os resultados obtidos demonstrem que as culturas bacteriocinogênicas avaliadas não possam ser empregadas como único método de conservação, estas podem atuar em sinergia com outros fatores para aumentar a eficiência no controle de patógenos Gram-positivos, especialmente L. monocytogenes, em produtos lácteos fermentados
Abstract: The biopreservation system, such as bacteriocinogenic lactic bacteria cultures and/or their bacteriocins, have received increasing attention and new approaches to control pathogenic and spoilage microorganisms have been developed. The purpose of this study was to evaluate the action of bacteriocin-producing cultures (Lactococcus lactis subsp. lactis ATCC 11454, Lactobacillus plantarum ALC 01 and Enterococcus faecium FAIR-E 198) on some Gram-positive pathogens in different culture media and dairy products. The bacteriocin production was influenced by the media. The antimicrobial activity of these cultures was evaluated by agar-well diffusion assay. The bacteriocins produced by Lb. plantarum ALC 01 and E. faecium FAIR-E 198 presented inhibitory activity on Listeria monocytogenes alone, on the other hand, the nisin produced by Lc. lactis subsp. Lactis ATCC 11454 demonstrated wide action spectrum, albeit with lower activity. In compatibility of associative development evaluation with the commercial starter culture, only Lc. lactis subsp. lactis ATCC 11454 presented activity on the starter culture. The acidifier activity determination was carried out in skimmed milk after 8h and 24h of incubation at 35ºC. The addition of 0.1% and 0.5% of the bacteriocinogenic cultures did not affect the production of lactic acid by the starter culture. The associative development of the starter culture with Lb. plantarum ALC 01 and E. faecium FAIR-E 198 provided significant increase in bacteriocin activity of these cultures, while the activity of Lc. Lactis subsp. lactis ATCC 11454 nisin was suppressed. The aminopeptidase activity was determined after cellular lise of the lactic cultures previously grown in MRS broth. Lb plantarum ALC 01 presented the largest activity. Moreover, the behavior of Gram-positive pathogens was analyzed during co-culture with the bacteriocin-producing bacteria and with the starter culture in skimmed milk. Lb. plantarum ALC 01 and E. faecium FAIR-E 198 did not influence the development of Bacillus cereus K1-B041 and of Staphylococcus aureus ATCC 27154 during the first 24h of incubation at 35ºC. They presented strong inhibition on L. monocytogenes Scott A. Lc. lactis subsp. lactis ATCC 11454 affected the development of the pathogens studied during the first 12h of incubation. The starter culture demonstrated good inhibition of B. cereus K1-B041 (>7.37 log UFC/ml) and L monocytogenes Scott A (>6.26 log UFC/ml). In Minas Frescal cheese, significant difference was not observed between the action of the bacteriocinogenic cultures and the starter culture on L. monocytogenes Scott A and S. aureus ATCC 27154. B. cereus K1- B041 demonstrated susceptibility to Lb. plantarum ALC 01 and E. faecium FAIR-E 198 after 7 days. Bacteriocin activity was not detected in the cheeses during 21 days at 8 ± 1ºC. The addition of the bacteriocin-producing bacteria as an adjunct culture to the Minas Frescal cheese did not promote alteration in the pH and in the acidity, however Lb. plantarum ALC 01 and E. faecium FAIR-E 198 promoted an increase of the cheese proteolysis. Although the obtained results demonstrated that bacteriocinogenic cultures cannot be used as only method of conservation, these can be used as an additional barrier to optimize the control of Gram-positive pathogens, especially L. monocytogenes, in dairy products
Doutorado
Doutor em Tecnologia de Alimentos

Thesis (PhD (Microbiology))--University of Stellenbosch, 2009.
Multidrug resistant strains of Staphylococcus aureus is presenting an increasing threat, especially immune compromised individuals. Many of these strains have developed resistance to newly approved drugs such as quinupristin-dalfopristin, linezolid and daptomycin. The search for alternative treatment, including bacteriocins (ribosomally synthesized antimicrobial peptides) of lactic acid bacteria is increasing . Lactococcus lactis subsp. lactis F10, isolated from freshwater catfish, produced a new nisin variant active against clinical strains of S. aureus. The operon encoding nisin F is located on a plasmid and the structural gene has been sequenced. The lantibiotic is closely related to nisin Z, except at position 30 where valine replaced isoleucine. The antimicrobial activity of nisin F against S. aureus was tested in the respiratory tract of Wistar rats. Non-immunosuppressed and immunosuppressed rats were intranasally infected with S. aureus K and then treated with either nisin F or sterile physiological saline. Nisin F protected immunosuppressed rats against S. aureus, as symptoms of an infection were only detected in the trachea and lungs of immunosuppressed rats treated with saline. The safety of intranasally administered nisin F was also evaluated and proved to have no adverse side effects. The potential of nisin F as an antimicrobial agent to treat subcutaneous skin infections was evaluated by infecting C57BL/6 mice with a bioluminescent strain of S. aureus (Xen 36). Immunosuppressed mice were treated with either nisin F or sterile physiological saline 24 h and 48 h after infection with subcutaneously injected S. aureus Xen 36. Histology and bioluminescence flux measurements revealed that nisin F was ineffective in the treatment of deep dermal staphylococcal infections. Non-infected and infected mice treated with nisin F had an influx of polymorphonuclear cells in the deep stroma of the skin tissue. This suggested that nisin F, when injected subcutaneously, may have modulated the immune system. Nisin F proved an effective antimicrobial agent against S. aureus-related infections in the respiratory tract, but not against subcutaneous infections. The outcome of nisin F treatment thus depends on the route of administration and site of infection.

Staphylococcus spp. é uma das principais causas da mastite bovina, onde o uso de antimicrobianos tem sido comprometido por mecanismos de resistência bacteriana e geração de resíduos que alteram a qualidade e segurança alimentar do leite e derivados. Foi avaliada a atividade in vitro da nisina (NS), do brometo de dioctadecildimetilamônio (DDA) e do complexo NS/DDA contra Staphylococcus spp. resistentes isolados de mastite bovina. A CBM50 da nisina e DDA foi 50 e 4μg/mL, respectivamente, enquanto que a CBM50 do complexo NS/DDA foi 3/2μg/mL, com efeito parcialmente sinérgico. O estudo de time-kill revelou redução de 3 log10 UFC/mL após uma hora de interação entre NS/DDA e a bactéria. A microscopia de fluorescência confirmou uma perda da viabilidade após 6 horas de interação. A interação NS/DDA resultou na formação de nanopartículas (148,5 nm) catiônicas (+8,84 mV) cuja interação com a superfície bacteriana negativa (-27,32 mV) resultou em ação bactericida. NS/DDA pode ser uma alternativa promissora contra Staphylococcus spp. resistentes isolados de mastite bovina.
Staphylococcus spp. is a major cause of bovine mastitis, where the use of antimicrobials has been compromised by bacterial resistance mechanisms and waste generation that change the food quality and safety of milk and dairy products. The in vitro activity antibacterial was evaluated of the nisin (NS), of the dioctadecyldimethylammonium bromide (DDA) and of the NS/DDA complex against drug-resistant Staphylococcus spp. isolated from bovine mastitis. The CBM50 of nisin and DDA were 50 and 4μg/ml, respectively, while the CBM50 NS/DDA complex was 3/2mg/mL, with partially synergistic effect. The time-kill study showed reduction of 3log10 CFU/mL after an hour of interaction between NS/DDA and bacteria. Fluorescence microscopy confirmed a loss of viability after 6h of interaction. NS/DDA interaction resulted in formation of nanoparticles (148.5 nm) cationic (+8.84 mV) which interact with negative bacterial surface (-27.32 mV) resulted in bactericidal activity. NS/DDA may be a promising alternative against drug-resistant Staphylococcus spp. isolated from bovine mastitis.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
O queijo Minas frescal é um dos produtos mais populares do Brasil e suas características nutricionais não são limitantes para o crescimento de micro-organismos deterioradores e patogênicos. Surtos de intoxicação alimentar envolvendo queijos Minas frescal contaminados com Staphylococcus aureus são frequentes e, por esse motivo, torna-se necessário o desenvolvimento de novas estratégias que controlem o crescimento desse patógeno no produto. Em razão disso, o objetivo desse trabalho foi o de avaliar o efeito das bacteriocinas bovicina HC5, nisina e de bactérias lácticas sobre o crescimento e produção de enterotoxinas por S. aureus. O crescimento das estirpes de S. aureus ATCC 6538, EMBRAPA 4018 e FRI 722 foi acompanhado em caldo tripticase e soja (TSB) e em leite em pó desnatado reconstituído a 10 % (LDR 10%), a 37 oC, em presença de bovicina HC5 e, ou nisina e Lactococcus lactis ATCC 19435. Amostras de queijo Minas frescal produzido com cultura starter (Lactococcus lactis subsp. lactis e L. lactis subsp. cremoris) foram inoculadas com, aproximadamente, 106 UFC.g-1 das estirpes de S. aureus e adicionadas de 1200 UA.g-1 das bacteriocinas. A presença das bacteriocinas aumentou a fase lag e este efeito foi mais acentuado na presença de nisina. Embora as bacteriocinas tenham apresentado efeito inibidor inicial, S. aureus reassumiu o crescimento e alcançou população final similar ao do tratamento controle, sem bacteriocinas, após 24 h de incubação. A produção de enterotoxina pelas estirpes de S. aureus avaliadas neste estudo foi detectada no meio TSB tanto na ausência como na v presença de bacteriocinas adicionadas ao meio de cultura. O cocultivo de S. aureus e L. lactis não interferiu no crescimento do patógeno, porém foi suficiente para inibir a produção de enterotoxinas. Em LDR 10 %, as bacteriocinas combinadas a 1200 UA.mL- exerceram efeito bactericida sobre as estirpes avaliadas de S. aureus e não foi possível recuperar sobreviventes pela técnica de contagem em placas após 96 h de incubação. A adição das bacteriocinas combinadas em queijo Minas frescal reduziu a população inicial de S. aureus, bactérias starter e da microbiota contaminante do queijo. A presença de enterotoxinas não foi detectada nos queijos produzidos com culturas starter, adicionados ou não das bacteriocinas nisina e bovicina HC5.
The Minas fresh cheese is one of Brazil's most popular products and their nutritional characteristics are not limiting to the growth of pathogenic and spoilage microorganisms. Outbreaks of food poisoning involving Minas fresh cheese contaminated with Staphylococcus aureus are frequent and, therefore, it becomes necessary to develop new strategies to control the growth of this pathogen in the product. For this reason, the aim of this study was to evaluate the effect of bovicin HC5, nisin and lactic bacteria on the growth and production of enterotoxins by S. aureus. The growth of strains of S. aureus ATCC 6538, EMBRAPA 4018, FRI 722 was conducted in tryptic soy broth (TSB) and reconstituted skimmed milk powder 10% (RSM 10%), at 37 °C, in the presence of bovicin HC5 and, or nisin and Lactococcus lactis ATCC 19435. Minas fresh cheese samples produced with starter culture (Lactococcus lactis subsp. lactis and L. lactis subsp. Cremoris) were inoculated with approximately 106 UFC.g-1 of strains of S. aureus and were containing added of 1200 UA.g-1 of bacteriocins. The presence of bacteriocins increased lag phase and nisin showed this effect more pronounced. Although the bacteriocins have shown initial inhibitory effect, S. aureus started to grow again and achieved the final population similar to the control treatment, without bacteriocins, after 24 h incubation. The enterotoxin production by strains of S. aureus evaluated in this study was detected in TSB medium both in the vii absence or presence of bacteriocins added to the culture medium. The coculture of S. aureus and L. lactis did not affect the growth of the pathogen, but it was sufficient to inhibit the production of enterotoxins. In RSM 10%, bacteriocins combined to 1200 UA.mL-1 exerted bactericidal effect on the strains of S. aureus and it was not possible to recover survivors by plate count technique after 96 h incubation. The addition of bacteriocins combined in Minas fresh cheese reduced the initial population of S. aureus, starter bacteria and contaminant microbiota of the cheese. The presence of enterotoxins was not detected in cheeses produced with starter cultures, added or not of bacteriocins nisin and bovicin HC5.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The Minas frescal cheese is one of the most appreciated dairy products in Brazil. Their chemical characteristics constitute a suitable medium for the growth of spoilage and pathogens microorganisms. This study aims to evaluate the effect of bovicin HC5 and nisin on the growth of both Listeria monocytogenes and Staphylococcus aureus in the Minas frescal cheese. Growth of strains of L. monocytogenes, L. innocua and S. aureus was carried out in tryptic soy broth (TSB) and in whole milk commercially sterilized (UHT) at 37 ºC in the presence of bovicin HC5 and nisin either added individually or in combination. Minas frescal cheese was manufactured and inoculated with an initial population of 104 CFU.g-1 of both L. monocytogenes and S. aureus, 600 AU.mL-1 of both bovicin HC5 and nisin were then added. The increase in the lag phase and the reduction of the specific growth rate of the strains of L. monocytogenes, L. innocua and S. aureus was verified at the concentrations of 10, 20 and 50 AU.mL-1 of bovicin HC5 in TSB broth. Growth was completely inhibited when bovicin HC5 was added at concentrations of 100 and 150 AU.mL-1 and at nisin concentrations above 10 AU.mL-1. L. innocua isolated from Minas cheese was sensitive to low concentrations of both bacteriocins while L. innocua LMA83 had an increase in 10 h in the lag phase when 10 and 20 AU.mL-1 of nisin were added to the TSB broth. In nisin and bovicin HC5 concentrations above 50 AU.mL-1, no growth of such strains was observed. The presence of the bacteriocins at concentrations up to 50 AU.mL-1 increased the lag phase but did not prevent the growth of S. aureus. On the other hand, concentrations of 100 or 150 AU.mL-1 of bovicin HC5 inhibited the bacterial multiplication. The combination of the two bacteriocins bovicin HC5 and nisin in TSB broth inhibited the growth of L. monocytogenes, S. aureus EMBRAPA 4018 and L. innocua at lower concentrations. However when used separately, higher concentrations of each bacteriocin should be applied. In milk, concentrations of bovicin HC5 above 400 AU.mL-1 reduced the number of viable cells of L. monocytogenes Scott A in one log cycle. However, nisin wasbactericidal just when used at 1200 AU.mL-1, being the growth resumed after 3 h of incubation. L. innocua LMA83 was sensitive to all bovicin HC5 concentrations added to milk while no reduction in the number of viable cells was observed after adding nisin. S. aureus ATCC 6538 in milk would still grow in the presence of 400 or 800 AU.mL-1 of bovicin HC5, being the bacteriostatic effect observed at the concentration 1200 AU.mL-1. Bactericidal effect on S. aureus cells was showed by nisin at 1200 AU.mL-1. In Minas frescal cheese, the number of initial viable cells was reduced from 104 CFU.g-1 of L. monocytogenes Scott A to values below 1 CFU.25 g-1 by additions of the bacteriocins combined at the concentration of 600 AU.mL-1 after nine days of storage at 4 ºC. After adding the combined bacteriocins in cheese for 15 days of storage at 4 ºC, bactericidal effect on S. aureus ATCC 6538 was observed. However, growth was resumed after that period. The presence of the combined bacteriocins at 600 AU.mL-1 did not prevent the production of staphylococcal enterotoxin C by S. aureus EMBRAPA 4018 in cheeses stored under 15 ºC. The present results demonstrate that bovicin HC5 and nisin are indeed effective in the control of pathogens assessed in milk and Minas frescal cheese, especially when associated.
O queijo Minas frescal é um dos produtos lácteos mais consumidos no Brasil e suas características químicas tornam-o um meio apropriado para o crescimento de micro-organismos deterioradores e patogênicos. O objetivo deste estudo foi avaliar o efeito de bovicina HC5 e nisina sobre o crescimento de Listeria monocytogenes e Staphylococcus aureus em queijo Minas frescal. O crescimento de estirpes de L. monocytogenes, L. innocua e S. aureus foi acompanhado em caldo tripticase de soja (TSB) e em leite integral comercialmente esterilizado (UAT), a 37 ºC em presença de bovicina HC5 e nisina adicionadas isoladas ou combinadas. Queijo Minas frescal foi produzido e inoculado com população inicial de 104 UFC.g-1 de L. monocytogenes e S. aureus e adicionado de 600 UA.mL-1 de bovicina HC5 e nisina. Na presença de concentrações de 10, 20 e 50 UA.mL-1 de bovicina HC5 em caldo TSB houve aumento da fase lag e redução da velocidade específica de crescimento das estirpes de L. monocytogenes, L. innocua e S. aureus. O crescimento foi completamente inibido quando bovicina HC5 foi adicionada nas concentrações 100 e 150 UA.mL-1 e em concentrações de nisinaacima de 10 UA.mL-1. L. innocua isolado de queijo Minas foi sensível a baixas concentrações das bacteriocinas enquanto L. innocua LMA83 apresentou um aumento de 10 h na fase lag quando 10 e 20 UA.mL-1 de nisina foram acrescentadas ao caldo TSB. Em concentrações de nisina e bovicina HC5 acima de 50 UA.mL-1, nenhum crescimento de L. innocua foi observado. A presença das bacteriocinas em concentrações de até 50 UA.mL-1 aumentou a fase lag mas, não impediu o crescimento de S. aureus enquanto as concentrações 100 ou 150 UA.mL-1 de bovicina HC5 inibiram a multiplicação bacteriana. A combinação das bacteriocinas bovicina HC5 e nisina em caldo TSB inibiu o crescimento de L. monocytogenes, S. aureus EMBRAPA 4018 e L. innocua em concentrações inferiores do que quando usadas isoladamente. Em leite UAT, concentrações de bovicina HC5 acima de 400 UA.mL-1 reduziram o número de células viáveis de L. monocytogenes Scott A em um ciclo log. Entretanto, nisina foi bactericida apenas quando foi usada na concentração de 1200 UA.mL-1, sendo o crescimento reassumido após 3 h de incubação. L. innocua LMA83 foi sensível a todas as concentrações de bovicina HC5 adicionadas ao leite enquanto nenhuma redução no número de células viáveis foi observada após adição de nisina. S. aureus ATCC 6538 cresceu em leite mesmo na presença de 400 ou 800 UA.mL-1 de bovicina HC5 e efeito bacteriostático foi observado na concentração 1200 UA.mL-1. A concentração 1200 UA.mL-1 de nisina exerceu efeito bactericida sobre células de S. aureus. Em queijo Minas frescal, a adição das bacteriocinas bovicina HC5 e nisina combinadas na concentração 600 UA.g-1 reduziu o número de células viáveis inicial de 104 UFC.g-1 de L. monocytogenes Scott A para valores abaixo de 1 UFC.25 g-1, após nove dias de estocagem a 4 ºC. Efeito bactericida sobre S. aureus ATCC 6538 foi observado nos queijos adicionados das bacteriocinas combinadas durante 15 dias de estocagem a 4 ºC. Entretanto, após esse período, a multiplicação de S. aureus foi retomada. A presença das bacteriocinas combinadas na concentração 600 UA.g-1 não impediu a produção de enterotoxinas estafilocócica C por S. aureus EMBRAPA 4018 em queijos mantidos sob temperatura de 15 ºC de estocagem. Estes resultados demonstraram que bovicina HC5 e nisina foram efetivas no controle dos patógenos avaliados em leite e queijo Minas frescal, em especial quando usadas associadas.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
This study aimed to isolate strains of Staphylococcus aureus in ricotta cheeses and to characterize them respecting phenotypic markers of lipolytic activity, and bacteriocin typing and resistance typing. For isolation, were acquired 11 samples of different brands of ricotta cheese sold in supermarkets in João Pessoa - Paraíba. Among the 41 strains, 82.9% proved positive lipase (Lip+) and 17.1%, negative lipase (Lip-). In relation to bacteriocin typing, 9.76% showed bacteriocin producing against a strain of Staphylococcus aureus isolated from surfaces processing food and 55% were susceptible to a strain of Staphylococcus aureus isolated from ricotta cheese. For resistance typing, 87.8% of strains were resistant to streptomycin, 26.59% to penicillin and 19.51% to erythromycin. None of the strains were resistant to tetracycline. Variability was observed between the minimal inhibitory concentrations (MIC), both in resistant strains as sensitive ones, so the variability showed more prevalent with penicillin (ranging from 0.015625 to 16 mg / mL) and the variability between strains of the same cheese. Only erythromycin-resistant strains were subjected to "D-test" to determine the type of resistance, of which all presented inductive resistant. From this results obtained, can conclude that although the phenotypes show an adaptive answer on related to the peculiarities of local environmental pressures, it is clear the importance of these genetic markers to discern new strains of S. aureus for those endemic, as well as to investigate possible epidemiological impacts and on food safety.
Este estudo teve como objetivo isolar cepas de Staphylococcus aureus de queijos ricota e caracterizá-las com relação a marcadores fenotípicos de atividade lipolítica, bacteriocinotipagem e resistotipagem. Para o isolamento, foram adquiridas 11 amostras de queijo ricota de diferentes marcas comercializadas em supermercados da cidade de João Pessoa-PB. Entre as 41 cepas isoladas, 82,9% revelaram-se lipase positiva (Lip+) e 17,1%, lipase negativa (Lip-). Com relação à bacteriocinotipagem, 9,76% mostraram-se produtoras de bacteriocinas frente a uma cepa de Staphylococcus aureus isolada de superfícies de processamento de alimentos e 55% mostraram-se sensíveis a uma cepa de Staphylococcus aureus isolada de queijo ricota. Para resistotipagem, 87,8% das cepas apresentaram-se resistentes a estreptomicina, 26,59% a penicilina e 19,51% a eritromicina. Nenhuma das cepas foi resistente a tetraciclina. Observou-se a variabilidade entre as Concentrações Inibitórias Mínimas, tanto em cepas resistentes como sensíveis, sendo tal variabilidade mais predominante com penicilina (variação de 0,015625 a 16 μg/mL), bem como a variabilidade entre cepas do mesmo queijo. Apenas cepas resistentes a eritromicina foram submetidas ao D-teste a fim de determinar o tipo de resistência, das quais todas as cepas mostraram-se com resistência indutiva. A partir dos resultados obtidos, pode-se concluir que embora os fenótipos revelem uma resposta adaptativa relacionada às peculiaridades das pressões ambientais locais, é evidente a importância destes marcadores genéticos a fim de se distinguir novas linhagens de S. aureus daquelas endêmicas, bem como investigar possíveis impactos epidemiológicos e na segurança alimentar.