Academic literature on the topic 'Staphylococcus aureus – Dissertations universitaires'

Abstract Background Commensal flora colonization during hospitalization by bacteria is the first step for nosocomial infections while antibiotic resistance reduces therapeutic options. In aim to control this phenomenon, we initiated this study to describe the impact of hospitalization on colonization by methicillin-resistant Staphylococcus aureus in the surgical department of 03 health facilities in the Ndé division, West-Cameroon. Methods This study was carried out on patients admitted for surgery in 03 health facilities of the Ndé division, West-Cameroon (District Hospital of Bangangté, Protestant Hospital of Bangwa and Cliniques Universitaires des Montagnes). After obtaining ethical clearance and authorizations, nasal swabs were performed at admission and discharge, with the aim of isolating bacteria and performing their antibiotic susceptibility tests. Informations on each participant's antibiotic therapy were recorded. Laboratory investigations were carried out according to standard protocols (CASFM, 2019). Results The most commonly used antibiotics were β-lactams. A total of 104 nasal swabs were performed on 52 patients who agreed to participate to the study. From the analysis, 110 (57 at admission versus 53 at discharge) Staphylococcus isolates were obtained. Overall, susceptibility testing showed that antibiotic resistance rates were higher at discharge than at admission; with significant differences between the susceptibility profiles obtained at admission and discharge for β-lactams and not significant for fluoroquinolones and aminoglycosides. Globally, frequency of nasal carriage of methicillin-resistant Staphylococcus aureus at discharge 16 (30.77%) was significantly higher than at admission 07 (13.46%) with Chi-2 = 4.52 and p = 0.0335. Conclusion The high rates of antibiotic resistance of bacteria isolated at discharge compared to those isolated at admission obtained in the present investigation, highlights the important role that hospitalization plays in the selection and dissemination of methicillin-resistant Staphylococcus aureus and colonization by these bacteria in health structures of Ndé division. As a result, further investigations to find the factors that promote this phenomenon should be carried out.

Abstract Background A bacteremia diagnosis with speeded-up identification and antimicrobial susceptibility testing (AST) is mandatory to adjust empirical broad-spectrum antibiotherapy and avoid the emergence of multi-resistant bacteria. Alfred 60AST (Alifax, Polverara, PD, Italy) is an innovative automated system based on light scattering measurements allowing direct AST from positive blood cultures with rapid results. In this study we aimed to evaluate the system’s performances and turnaround time (TAT) compared to routine AST. Methods The study was conducted during 2 non-consecutive 3-month periods at the microbiology laboratory of the Cliniques universitaires Saint-Luc. All blood cultures detected positive in the 0 AM–10 AM time frame with a pure Gram-positive cocci or Gram-negative bacilli stain were included for Alfred 60AST testing. Two customized EUCAST antibiotic panels were set up composed of 1) a “Gram-negative” panel including cefuroxime, ceftazidime Enterobacteriaceae, piperacillin-tazobactam Enterobacteriaceae, ciprofloxacine, and ceftazidime Pseudomonas 2) a “Gram-positive” panel including cefoxitin Staphylococcus aureus, cefoxitin coagulase-negative (CNS) Staphylococci and ampicillin Enterococci. Categorical agreement (CA), very major errors (VME), major errors (ME), minor errors (mE) and TAT to Alfred 60AST results were calculated in comparison with AST results obtained from direct testing on positive blood cultures with the Phoenix system (Becton Dickinson, Franklin Lakes, NJ, USA). Results Five hundred seventy and one hundred nine antibiotics were evaluated on respectively 166 Gram-negative bacilli and 109 Gram-positive cocci included in the studied population. During the first study period regarding Gram-negative strains a CA of 89.5% was obtained with a high rate of VME (19 and 15.4% respectively) for cefuroxime and piperacillin-tazobactam Enterobacteriaceae. Considering this, Alifax reviewed these antibiotics’ formulations improving Gram-negative bacilli total CA to 92.2% with no VME during the second study period. For Gram-positive cocci, total CA was 88.1% with 2.3% VME, 13.8% ME (mainly cefoxitin CNS) and 12% mE rates both study periods combined. Median TAT to AST results was 5 h with Alfred versus 12 h34 with Phoenix. Conclusion The Alfred 60AST system shows correct yet improvable microbiological performances and a major TAT reduction compared to direct automated AST testing. Clinical studies measuring the impact of the approach on antibiotic management of patients with bacteremia are recommended.

<p><span style="white-space: pre;"> </span>The UIC RESEARCH JOURNAL (International Edition) Volume 18 Number 2 October 2012 issue contains 17 articles written by faculty researchers not only from the University of the Immaculate Conception but also from other universities and colleges of Davao City. It provides three sections for the publishable versions of research papers, theses, or dissertations recently completed by these scholars from various fields.</p><p><span style="white-space: pre;"> </span>Section One - Engineering, Mathematics and Technology, reveals the studies done by Alberto G. Forones Jr., Eric John G. Emberda et. al, Exander T. Barrios et. al, and Mary Jane G. Barluado. This part highlights relevant information about graduates’ achievements in engineering board examinations--- a retrospective study, applications of information technology knowledge, and creation of a cosmetic product for sun protection.</p><p><span style="white-space: pre;"> </span>Section Two - Health and Health Profession, presents the papers written by Elizabeth M. Malonzo (Brokenshire College), Fe Frauline C. Magdaluyo (Davao Doctors College), Jason O. Molina, S. Ma. Remegia M. Cirujales and Letty G. Kuan (University of Santo Tomas). This section showcases studies that deal with important issues concerning health and health profession, such as the following: MSM’s decision to indulge in unprotected anal intercourse (bareback sex) in relation to his awareness of HIV/AIDS risk; the behavior of nursing students in the clinical area and the manifestation of the ideal nursing roles; the relationships between food safety knowledge and practices of hospital food handlers in Davao City and also between their attitudes and practices regarding food safety; and governance in nurse migration.</p><p><span style="white-space: pre;"> </span>Section Three - Philosophy and Education, tackles specifically the following papers: Asisclo M. Abonado’s Being-for-Itself as Freedom: A Preliminary Inquiry on Jean-Paul Sartre’s Philosophy of the Human Person, Porferia S. Poralan, Rene M. Babiera, and Rebecca P. Habla’s Strengthening and Preserving Practices of Philippine Folk Dances in Relation to Cultural Awareness of Secondary Students of Davao City, Camfel V. Balaud-Tabboga’s Institutional Leadership, Teacher’s Competence on Curricular Trends and Student’s Performance in Science, Cromwell M. Castillo’s Faculty Behavioral Intention to Adopt Web 2.0 Technologies: A Path Analysis, and Renan P. Limjuco and Juvie Pauline L. Relacion’s Stakeholder’s Program Evaluation and Review: Leading to the Enhancement of Computer Engineering Curricular Program. This portion focuses on topics of pure academic nature; their relevance to curriculum and instruction defines their significance as journal entries for this particular issue.</p><p><span style="white-space: pre;"> </span>Section Four – Pharmacy/Chemistry, presents studies that deals on quality and safety evaluation of commercial mangosteen capsule, toxicological and antimicrobial evaluations of formulated ointment from eskwater leaf extract against MRSA, bronchodilating activity of formulated syrup of jackfruit root extract in albino rats, and bacteriological, toxicological and mutagenic evaluations of the formulated ointment of knobweed (Hyptis capitata Jacq.) leaf extract against methicillin-resistant Staphylococcus aureus. The researchers for these studies are Judee N. Nogodula, Kathleen G. Bersabal, and Ma. Eva C. San Juan.</p><p> </p><p>Dr. Renan P. Limjuco</p><p>Editor in Chief</p><p>UIC Research Journal</p><p>International Edition</p>

Les infections ostéo-articulaires à Staphylococcus aureus sont des pathologies fréquentes dont les conséquences peuvent aller de la simple altération cellulaire à un retard de la réparation osseuse ou une réponse inflammatoire excessive. Afin d’étudier ce phénomène, nous avons, dans un premier temps, développé deux modèles d’infections in vitro faisant interagir Staphylococcus aureus et des cellules osseuses primaires issues d’explants chirurgicaux humains. Ces cellules ont été préalablement cultivées dans un milieu standard ou un milieu ostéogénique afin d’obtenir 2 populations à des stades de maturation différents. L’étude de l’internalisation de Staphylococcus aureus, de la mortalité cellulaire et de la production de médiateurs inflammatoires pour ces 2 populations a permis d’établir si l’impact de Staphylococcus aureus variait en fonction de la maturation cellulaire. Dans un second temps, nous avons étudié l’impact de Staphylococcus aureus sur des cellules souches mésenchymateuses dérivées du cordon ombilical. En effet, dans le cadre d’une régénération osseuse en site infecté, les cellules souches mésenchymateuses pourraient être amenées à interagir avec Staphylococcus aureus. Nous avons donc caractérisé la capacité de ces cellules à internaliser Staphylococcus aureus, à survivre face à l’infection et à produire des médiateurs inflammatoires dans notre modèle in vitro d’infection aiguë. Ce projet nous a permis de valider nos modèles d’infection in vitro et de caractériser l’impact de Staphylococcus aureus sur différentes cellules du microenvironnement osseux, donnant ainsi de nouvelles pistes pour le développement de stratégies pour la lutte antibactérienne et l’ingénierie tissulaire osseuse
Staphylococcus aureus-related bone and joint infections are common diseases whose consequences can range from simple cell damage to delayed bone repair or excessive inflammatory response. To study this phenomenon, we have developed two models of in vitro infection with Staphylococcus aureus and primary bone-forming cells derived from human surgical explants. These cells have been previously cultured in a standard medium or osteogenic medium to obtain two populations at different stages of maturation. The study of Staphylococcus aureus internalization, cell death and production of inflammatory mediators in these 2 populations allowed us to establish whether the impact of Staphylococcus aureus varied depending on cell maturation. We also studied the impact of Staphylococcus aureus on mesenchymal stem cells derived from umbilical cord. In case of bone regeneration in infected site, mesenchymal stem cells may have to interact with Staphylococcus aureus. Therefore, we characterized the ability of these cells to internalize Staphylococcus aureus, to survive against the infection and to produce inflammatory mediators in our in vitro model of acute infection. This project allowed us to validate our in vitro infection models and to characterize the impact of Staphylococcus aureus on different cells in the bone microenvironment, providing new approaches for the development of antibacterial strategies and bone tissue engineering

Staphylococcus aureus est une bactérie à Gram positif responsable d'un nombre croissant de pathologies humaines. Notre étude a comme objectif d'étudier la production de cytokines par les cellules mononucléées phagocytaires (monocytes, macrophages péritonéaux et alvéolaires) en réponse à S. Aureus. Nous avons confirmé que la présence de TLR2 n'était pas indispensable pour la reconnaissance de S. Aureus par les macrophages péritonéaux. En revanche, l'activation du TLR2 et la phagocytose de la bactérie étaient requises simultanément pour les monocytes et les macrophages alvéolaires, afin d'obtenir une production optimale de cytokines. De plus, à l'aide d'inhibiteurs spécifiques, nous avons observé que p38 et la Pi3K avaient un rôle central dans ces deux voies d'activauon. Au contraire, Racl et ERK étaient important spécifiquement pour l'activation de la voie intracellulaire chez les macrophages péritonéaux ou alvéolaires. Nous avons cherché à identifier le récepteur intracellulaire permettant la détection de S. Aureus après phagocytose. La transfection d'un dominant-négatif de NOD2 dans la lignée macrophagique RAW 264. 7 inhibait fortement l'activation de NF-KB en réponse à S. Aureus. Mais en utilisant des cellules primaires ne possédant pas NOD2, nous avons observé que l'absence de ce récepteur n'avait pas d'incidence sur la production de cytokines. Enfin, l'injection en intra-nasal d'une souche de S. Aureus, n'a pas montré de différence entre les souris NOD2 déficientes et leurs congénères sauvages. Toutefois, les souris NOD2 déficientes semblaient se remettre plus rapidement de l'infection, que ce soit au niveau de la perte du poids que des lésions pulmonaires. En conclusion, nos travaux mettent en évidence une voie d'activauon des macrophages autre que le TLR2 et dépendante de la phagocytose. NOD2 ne semble pas jouer un rôle critique, lors de la réponse à S. Aureus, que ce soit in vitro ou in vivo. Enfin, nous avons pu observer qu'au sein même de la population mononucléée phagocytaire, il existe de grandes différences quant au rôle de la phagocytose dans la réponse à S. Aureus. Ceci souligne l'hétérogénéité de la réponse de ces phagocytes professionnels selon le compartiment dont ils proviennent
Staphylococcus aureus is a Gram positive bacteria leading to an increasing number of human pathologies. The goal of our work was to study the S. Aureus-induced cytokine production by phagocytic mononuclear cells (i. E monocytes, peritoneal and alveolar macrophages). We confirmed that TLR2 was dispensable for peritoneal macrophage response to S. Aureus. In contrast, TLR2 activation and phagocytosis were both required to obtain a full cytokine production in monocytes and alveolar macrophages. Furthermore, with specific inhibitors, we observed that p38 and Pi3K had a key role in both activation pathways. On the contrary, Racl and ERK were important for macrophages intracellular pathway. We then investigated which receptor was detecting S. Aureus after phagocytosis. Transfection of a dominant-negative form of NOD2 in RAW 264. 7 macrophagic cell line inhibited strongly NF-KB activation in response to S. Aureus. However, using NOD2-deficient primary cells, we observed that the absence of NOD2 did not alter cytokine production. Finally, NOD2-/- animals responses were comparable to wild-type after intra-nasal injection of S. Aureus. Nevertheless, NOD2-/- mice recovered faster than wild-type (weigh gain and pulmonary lesions). In conclusion, our work shows the existence of a TLR2-independant activation pathway that relies on phagocytosis. NOD2 does not play a critical role in S. Aureus response, both in vivo and in vitro. Finally, we show that, in phagocytic mononuclear cells, there is a great discrepancy in the role of phagocytosis in the response to S. Aureus. This work underlines the heterogeneity in the phagocytic cells response depending on the compartment they are derived from

@On appelle infections nosocomiales, les maladies infectieuses contractées au cours d'une hospitalisation qui n'étaient ni en incubation ni présentes à l'admission du patient. Elles peuvent être d'origine endogène ou exogène : le patients lui-même, le personnel, le matériel, les surfaces et l'environnement. Cette contamination peut résulter d'un manque d'efficacité des procédures de nettoyage-désinfection, déficience souvent attribuée à l'état dans lequel se trouve ces germes indésirables (biofilms). Pour réduire ces risques de contamination deux axes ont été abordés : d'une part les prédictions d'adhésion entre le support en acier inoxydable AISI 304 (constituant majeur du matériel en bloc opératoire) et quatre souches responsables d'infections nosocomiales (E. Coli, S. Aureus, P. Aeruginosa et E. Hirae) et d'autres parts, l'évaluation de l'efficacité ainsi que les conditions d'utilisation d'un nouveau désinfectant OXSILÒ 320N sur des cellules planctoniques et des biofilms. L'étude physicochimique a montré toute la complexité des interactions impliquées dans la phase initiale d'adhésion. Si en théorie, il est possible d'enrayer l'adhésion bactérienne à un support en modifiant ses caractéristiques de surface, notre étude montre qu'il est impossible de limiter l'adhésion simultanée des 4 souches bactériennes étudiées au support AISI 304. Face à une telle situation, il est donc impératif d'optimiser les procédures de nettoyage-désinfection. OXSILÒ320N possède une activité de spectre 4 selon la norme AFNOR NF T 72-150 sur des cellules planctoniques à la concentration de 3,13%. Par contre les biofilms sont plus résistants que leurs homologues planctoniques. Ceci serait dû à la présence de mécanismes de défense connus. Selon les recommandations d'utilisation de SODIFRA les conditions optimales pour obtenir un niveau "zéro" de contamination sont : 12,52% d'OXSILÒ320N et un temps de contact de 10 min évitant tout risque infectieux entre deux opérations de courtes ou de longues durées en blocs opératoires. Ces résultats ont mis en évidence la nécessité d'utiliser ce désinfectant à une concentration appropriée et de ne pas négliger les conséquences d'une utilisation en infradose même si celle-ci autorise selon les normes AFNOR une activité bactéricide
@Nosocomial infections are hospital acquired infections. They are not present or incubating when the patient is admitted to the hospital, and are either endogenous or exogenous. Endogenous ones are caused by organisms present in the patient own flora and exogenous infections are caused by organisms originating from medical devices, hospital staff, or environment. This contamination might be the result of a lack of efficiency in cleaning and disinfection procedures, those deficiencies being often attributed to the state in which these harmful microorganisms are found (biofilms). To reduce the risks of contamination, two parts have been developed in this thesis: at first, predictions of adhesion between stainless steel AISI 304 (major component of equipment in operating room) and four nosocomial strains (E. Coli, S. Aureus, P. Aeruginosa et E. Hirae), and in the second part, we determine, the efficient concentration of a new disinfectant OXSILÒ 320N in order to eliminate biofilms. Physico-schemical studies demonstrated the complexity of interactions involved in the initial phase of adhesion. We suggest that a change of the stainless steel surface properties could theoretically limit bacterial adhesion. However it was nearly impossible to limit adhesion between the four studied bacterial strains and the support AISI 304. It is then necessary to optimise preventive hygienic conditions. The bactericidal concentration of OXSILÒ 320N against planktonic cells, according to AFNOR Norm NF T 72-150, was 3,13%. Furthermore, biofilms were commonly more resistant than their planktonic counterparts due to the presence of known resistance mechanisms. According to the SODIFRA recommendations, the optimal conditions, required to avoid any contamination, were a concentration 12,52% and 10 min contact. These conditions can eliminate infection risks during short or long laps between two interventions in an operating room. These results revealed the necessity to use this disinfectant at appropriate concentration and but also the consequences of using it in infradose, although this concentration is considered as an efficient concentration by AFNOR Norm

Since 1999, Methicillin-resistant Staphylococcus aureus (MRSA) outbreaks have occurred in many correctional facilities. Even after the Federal Bureau of Prisons developed clinical practice guidelines on the management of MRSA within correctional facilities, the prevalence of MRSA decreased only insignificantly. Other researchers suggested infection control compliance was equally as important as developing clinical practice guidelines in reducing the incidence of MRSA. Several studies identified the healthcare professionals' nonadherence and inconsistencies to clinical practice guidelines as contributors to MRSA transmission. Accordingly, this project was designed to develop evidence-based recommendations for improving nurse professionals' adherence to MRSA practice guidelines in correctional settings. Using the health belief model as the theoretical framework, this project examined the nurse professionals' perceptions as well as their level of knowledge regarding MRSA by using an original instrument, Knowledge and Health Beliefs Regarding MRSA Questionnaire. The study employed a quantitative design with a purposeful sample of 36 participants using social media. Through descriptive statistical analysis, it was determined that MRSA training and education were the greatest barriers among the nurse professionals in taking MRSA preventive action (64%, n = 23). Based on the findings, assessing the educational needs of the nurse professionals must become the priority when designing infection control programs. This study contributes to social change by recognizing the potential health impact of MRSA and cautions that if public health officials do not control MRSA within correctional settings, such behavior can affect the transmission of MRSA both nationally and globally.

Chiropractic training involves many hours of skin contact, and chiropractors have manual contact with millions of patients annually, but chiropractic has only had professional clinical hygiene guidance since 2010. Methicillin-resistant Staphylococcus aureus (MRSA) is the most common cause of cultured skin and soft tissue infection (SSTI) in the United States. Using the epidemiologic triad of person, place, and time as a framework, this quantitative, cross-sectional study obtained the first assessment of MRSA SSTI incidence among chiropractic students and its association with infection control behaviors (hand and table hygiene, sharing gowns, and sharing lotion) and initiation of patient care. The study obtained surveys from 312 students attending half (9/18) of U.S. chiropractic campuses. Associations were assessed by Ï?2 and Fisher's exact test. Stratum specific effects were assessed. Two logistic regression models were produced. The results were that attendance at Campus 6 was associated with postmatriculation MRSA SSTI in univariate analysis, p = 0.010. There was an interaction between campus attended, sharing lotion, and postmatriculation MRSA SSTI, with the Mantel-Haenszel pooled estimate varying significantly from unity, Ï?2 (1) = 6.75, p = 0.009. No other association between any assessed factor and MRSA SSTI was detected. Logistic regression models were significant (p < 0.05), but the composing variables were not. For social change, chiropractic colleges should instruct students and chiropractic associations could encourage members not to share massage lotions and emollients during the practice of manual therapy to help prevent MRSA SSTI.

Methicillin-resistant Staphylococcus aureus (MRSA) strains have spread in Saudi Arabia, increasing morbidity, mortality, and financial burdens. Recent studies have suggested the phenotyping methods typically used to classify MRSA as either health care MRSA (HA-MRSA) or community-associated MRSA (CA-MRSA) cases are unreliable, because they lack concordance with the results of genotyping. Yet the expense associated with genotyping precludes its use in the Saudi Aramco population in Saudi Arabia. The absence of a standardized and affordable method to classify MRSA into CA-MRSA and HA-MRSA has been a challenge for infection control programs in Saudi Arabia. The objective of this quantitative, secondary data analysis was to determine the most reliable phenotyping approach to strain identification using John Hopkins Aramco hospital data. The ecological and antibiotics selection pressure theories framed this research. The results of concordance, and sensitivity and specificity tests, suggested hospital admission profiles and susceptibility pattern were the most reliable phenotypic predictors of genotype-based classifications. Multiple logistic regression for susceptibility pattern (OR = 15.47, p < .001) and hospital admission profile (OR = 2.87, p = .008) confirmed those results, whereas all other variables were not found to be statistically significant. These results can be used to clarify the epidemiological and molecular factors that affect the transition of MRSA from health care facilities to the Saudi Aramco community. Implications for positive social change include faster and more reliable classification of MRSA to aid in disease surveillance and the selection of appropriate treatments to reduce MRSA-related morbidity and mortality.

Staphylococcus is a significant cause of human infection and mortality, worldwide. Currently, there are greater than 60 taxa within Staphylococcus, and nearly all are pathogenic. The collective potential for virulence among species of Staphylococcus heightens the overall clinical significance of this genus and argues for a thorough understanding of the evolutionary relationships among species. Within Staphylococcus, aureus is the most common cause of human infection, where nasal carriage of this bacterium is a known risk factor for autoinfection. The predisposition to infection by nasal carriers of S. aureus, and the ease with which strains are transferred between individuals, suggests that nasal carriage is a major vector for the transmission of virulent strains throughout the community. This hypothesis, however, has not been assessed in any great detail to identify the genetic relationships between clinical isolates of S. aureus and those strains being carried asymptomatically throughout the community. Also lacking within this field is a unified and robust estimate of phylogeny among species of Staphylococcus. Here, we report on a highly unified species phylogeny for Staphylococcus that has been derived using multilocus nucleotide data under multiple Bayesian and maximum likelihood approaches. Our findings are in general agreement with previous reports of the staphylococcal phylogeny, although we identify multiple previously unreported relationships. Regardless of methodology, strong nodal support and high topological agreement was observed with only minor variations in results between methods. Based on our phylogenetic estimates, we propose that Staphylococcus species can be evolutionarily clustered into 15 groups, and six species groups. In addition, our more defined phylogenetic analyses of S. aureus revealed strong genetic associations between both nasal carriage strains and clinical isolates. Genetic analyses of hypervariable regions from virulence genes revealed that not only do clinically relevant strains belong to identical genetic lineages as the nasal carriage isolates, but they also exhibited 100% sequence similarity within these regions. Our findings indicate that strains of S. aureus being carried asymptomatically throughout the community via nasal colonization are genetically related to those responsible for high levels of infection and mortality. Due to nasal carriage of S. aureus being a risk factor for autoinfection, standardized preoperative decolonization has become a major consideration for the prevention of nosocomial infection. Toward this end, we have identified the macrocyclic ?-defensin analogue RC-101 as a promising anti-S. aureus agent for nasal decolonization. RC-101 exhibited bactericidal effects against S. aureus in both epithelium-free systems, and ex vivo models containing human airway epithelia. Importantly, RC-101 exhibited potent anti-S. aureus activities against all strains tested, including USA300. Moreover, RC-101 significantly reduced the adherence, survival, and proliferation of S. aureus on human airway epithelia without any noted cellular toxicity or the induction of a proinflammatory response. Collectively, our findings identify RC-101 as a potential preventative of S. aureus nasal colonization.
ID: 030646199; System requirements: World Wide Web browser and PDF reader.; Mode of access: World Wide Web.; Thesis (Ph.D.)--University of Central Florida, 2011.; Includes bibliographical references (p. 140-159).
Ph.D.
Doctorate
Molecular Biology and Microbiology
Medicine
Biomedical Sciences

Methicillin-resistant staphylococcus aureus (MRSA) has become resistant to antibiotics. The purpose of this quantitative, retrospective cohort study was to examine the relationship between length of hospitalization and invasive MRSA infection rates among different racial and ethnic groups in the 8 service planning areas (SPAs) of Los Angeles County. Cane, O'Connor, and Michie's theoretical domain framework was used. Secondary data from the Healthcare-Associated (HA) Infections Program of the California Department of Public Health were analyzed. For the first research question, a Pearson correlation analysis was conducted to assess the relationships between length of hospitalization and invasive HA-MRSA infection rates and counts. Length of hospital stay was not correlatedwith HA-MRSA infection rates; however, it was strongly and positively correlated with HA-MRSA infection counts. For the second research question, a one-way ANOVA was conducted on the infection count rate data, with SPA as the between-subjects factor. The results were statistically significant, indicating that HA-MRSA infection counts varied among the 8 SPAs. The findings might help medical professionals better understand the risk factors associated with MRSA infections. In doing so, findings may relieve some of the burden on the U.S. health care system and improve the overall quality of life of the patients involved.

The major research interest of our laboratory is focused on the replication-specific DNA polymerase III (pol III) family in Gram+ bacteria, and has used Bacillus subtilis (BS) as the primary model enzyme for study. The long range objective of the work of the laboratory is to gain a deeper understanding of the structure and function of Gram+ bacterial DNA polymerase IIIs, a structurally unique class of DNA-dependent DNA polymerase which are uniquely susceptible to inhibition by a specific class of dGTP analogs. The project described in this thesis dissertation deals specifically with the pol III of the Gram+ organism Staphylococcus aureus, and involves the isolation and characterization of DNA pol III from this clinically relevant pathogenic bacterium. A homology-based strategy was devised to clone the structural gene specifying DNA polymerase III of Staphylococcus aureus, SA polC. SA polC was found to contain a 4305-bp open reading frame (ORF) encoding a 162.4 kDa polypeptide, and mapped between Ω1074[Tn551] and recA/ngr on the genome map of S. aureus NCTC 8325. The 1435 codon ORF was engineered into the E. coli expression plasmid pBS(KS) under the control of the lac promoter and its repressor. The translational signals of SA polC were reengineered using expression cassette PCR (ECPCR) to optimize the in vitro expression of SA polC in E. coli. Derepression of E. coli transformants carrying the recombinant vector generated high level expression of active recombinant pol III. The recombinant SA pol III was purified to greater than 98% homogeneity and was shown by N-terminal amino acid analysis to be the bona fide product of the 4305-bp SA polC ORF. The physical and catalytic properties of recombinant SA pol III and its responsiveness to inhibitors of the HPUra type were similar to those of Bacillus subtilis (BS) pol III. Comparative structural analysis of the primary structure of SA pol III and the pol IIIs of B. subtilis and the Gram+ relative Mycoplasma pulmonis indicated strong conservation of essential catalytic domains and a novel zinc-finger motif. Comparison of the primary structures of E. coli pol III and these three Gram+ enzymes suggested a specific evolutionary relationship between the pol IIIs of Gram+ and Gram- bacteria.