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.

Background Streptococcus pneumoniae and Staphylococcus aureus are important pathogens causing bacterial infections in children worldwide. At least 93 different serotypes have been identified and recognized in Streptococcus pneumoniae. In Hong Kong, the 7-valent-pneumococcal vaccine (PCV7) has been introduced into the childhood immunisation programme since September 2009, but widespread use of this vaccination may bring about epidemiological changes in the bacteria commonly carried by children. Objectives (i) To examine the changes in carriage, serotype distribution and antibiotic resistance of nasopharyngeal pneumococcal isolates in children before and after the introduction of PCV7 in Hong Kong. (ii) To analyse the association between S. pneumoniae and S. aureus colonisation among young children in Hong Kong following the use of pneumococcal conjugate vaccine. Methods Nasopharyngeal swabs were collected from 1978 and 2211 children aged 2 to 6 years attending day care centres (DCCs) and kindergartens (KGs) in all 18 school districts in Hong Kong in period 1 (1999-2000) and period 2 (2009-2010), respectively. Nasal samples were also collected from the participants in period 2 for detection of S. aureus. E-test and disc diffusion method were used to determine the antibiotic susceptibility. Sequential multiplex PCR and/or the quellung reactions were used for serotyping. A standardized questionnaire was also used to obtain information from children’s parents so as to study the variables associated with the carriage of these two bacteria. Results In the first part of our study, the PCV7 vaccine penetration (at least one dose) in period 2 was 28.1% (622/2211). The nasopharyngeal carriage rate of PCV7 isolates decreased from 12.8% in period 1 to 8.6% in period 2 (P < 0.001). Vaccine serotypes 14 and 18C had decreased significantly while non-vaccine serotypes 19A, 6A, 6C 23A and 15B had increased significantly from period 1 to period 2. Dual penicillin/erythromycin non-susceptibility rates for 19F, 14, 6A and 23A has also been found to increase over the two time periods. In the second part of our study, 27.6% of the children were found to carry S. aureus and the nasal MRSA carriage rate was 1.3%. Molecular typing including staphylococcal cassette chromosome mec (SCCmec), sequence type (ST) and clonal cluster (CC) showed that all the 28 MRSA isolates belonged to SCCmec IV (n = 13) or V (n = 15). Twelve of these isolates had community-associated MRSA genotypes (ST59/SCCmec IV, ST30/SCCmec IV, ST88/SCCmec V), ten isolates had healthcare-associated MRSA genotypes (ST45/SCCmec IV/V, CC5/SCCmec IV and ST630/SCCmec V) and six isolates had novel genotypes (ST10/SCCmec V, CC1/SCCmec IV). spa typing results also indicated an intra- and inter-school transmission of certain MRSA and methicillin-sensitive S. aureus strains. Significant association between S. pneumoniae and S. aureus carriage was not found in this study. Conclusion Our study found that carriage, serotype distribution and antibiotic resistance of nasopharyngeal pneumococcal isolates in children have changed after the use of PCV7 in Hong Kong while association between S. pneumoniae and S. aureus colonisation among young children in Hong Kong was not found. Further studies investigating the five increasing non-PCV7 serotypes are warranted to guide future vaccine policy. / published_or_final_version / Microbiology / Master / Master of Philosophy

Sepsis is a systemic inflammatory response that causes, increased heart rate, respirations, fever, and inadequate blood flow to organs. One of the most prevalent causes of sepsis is Staphylococcus aureus (S. aureus). With increasing numbers of strains of bacteria becoming antibiotic resistant, new methods for the treatment and clearance of sepsis are needed. Studies have shown that the lipid lowering drug simvastatin is protective for incidence of sepsis, having immunomodulatory effects and anti-inflammatory properties, specifically. Thus, it may be an alternative way to prevent sepsis due to S. aureus infections. Studies in our laboratory have shown that simvastatin pretreatment increases survival of mice infected with S. aureus and alters the adaptive immune response such that levels of IgG2c are reduced to the level of uninfected controls. Our studies have demonstrated that while simvastatin does not enhance bacterial clearance, or affect serum C5a levels, it does decrease serum levels of TNF. / Department of Biology

Access to abstract permanently restricted. / Aldol condensation to synthesize substituted chalcones -- Synthesis and testing of substituted 4,5-dihydropyrazoles -- Biological testing of synthesized 4,5-dihydropyrazoles. / Access to thesis permanently restricted. / Department of Chemistry

Staphylococcus aureus are Gram-positive bacteria that adhere to the extracellular matrix of susceptible host cells to initiate infection and induce a signal transduction pathway that includes PI3K causing the disruption of cytoskeletal elements within the cytosol. Confocal microscopy was applied to visualize actin within human umbilical vein endothelial cells (HUVEC) to discern behavior during infection. HUVEC lysates were analyzed through immunoprecipitation and Western blot analysis to determine the isoforms of PI3K present in HUVECs. Infection experiments and confocal microscopy reveal a time dependent disruption of actin and a dose dependent decrease in infection when HUVECs are treated with the PI3K inhibitor LY294002. Results of Western blot analysis reveal a distinct band corresponding to the pl l0a isoform of PI3K in HUVECs. These studies taken together suggest that PI3K is involved in the signal transduction pathway induced by the infection of HUVECs by S. aureus, and that infection causes the disruption of cytoskeletal actin fibers. / Department of Biology

Access to abstract restricted until May 2016. / Access to thesis restricted until May 2016 / Department of Biology

Thesis (Ph. D.)--University of Missouri--Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves: [89]-98). Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. "December 2008" Includes bibliographical references.

Staphylococcus aureus is a Gram-positive bacterium predominantly found on human skin and in nasal passages with 20 to 40 percent of the population carrying this organism. Although S. aureus is an unspectacular, non-motile coccoid bacterium, it is a perilous human pathogen associated with both nosocomial and community-acquired infections and it is increasingly becoming virulent and resistant to most antibiotics. It is responsible for several infections such as osteomyelitis, toxin-mediated diseases and bacteraemia, with severe infections arising from strains harbouring antibiotic resistance genes together with virulence genes. S. aureus has been largely confined to hospitals and long-term care facilities, but it is now emerging in the community in places such as recreational beach waters, and occurring in healthy individuals with no associated risk factors. This organism has been reported to be released by swimmers in beaches, suggesting that recreational waters are a potential source of community-acquired S. aureus infections. It is possibly the pathogen of greatest concern due to its intrinsic virulence, its capacity to cause various life-threatening infections, and its ability to adapt to varying environmental conditions. This study was aimed at characterizing S. aureus and methicillin-resistant S. aureus (MRSA) in Port Elizabeth, Port Alfred, Kenton-on-sea and East London beaches of the Eastern Cape Province of South Africa. This was done by investigating the occurrence, antibiotic susceptibilities, antibiotic-resistant genes and virulence genes profiles of S. aureus in the selected beaches. To achieve this aim, 249 beach sand and water samples were obtained from the beaches during the period of April 2015 to April 2016. Physico-chemical parameters of beach water was investigated on site using a multi-parameter ion specific meter during sample collection. Samples were filtered and inoculated on m-Endo agar, m-FC agar and bile aesculin azide agar for total and faecal coliform as well as Enterococci respectively. For isolation of S. aureus and MRSA, samples were cultured on Mannitol salt agar and Staph 24 agar. S. aureus was identified using morphological, Gram staining and molecular (PCR) methods. The isolates were further characterized by determining their antimicrobial resistance profiles, antibiotic resistant genes (mecA, rpoB, blaZ, ermB and tetK genes) and detection of virulent genes encoding intracellular adhesion (icaA), enterotoxin (seaA) and cytolytic toxins (PVL). The majority of study sites passed the directives of physico-chemical standards levels set by WHO during the study period. A total of 143 presumptive isolates were obtained of which 30 (30 percent) were confirmed as S. aureus with 22 (73.3 percent) of these confirmed isolates from marine water and 8 (26.7 percent) from marine sand. Upon culturing on MRSA 2 agar, 15 (50 percent) of isolates showed phonotypic resistance to methicillin. Based on Antimicrobial susceptibility tests, (22/30) 73.3 percent of the isolates showed phonotypic resistance to oxacillin. Out of the 30 isolates, 16 (53.3 percent) were mecA positive and were considered methicillin-resistant S. aureus. S. aureus showed high susceptibility to gentamycin, cefoxithin, levofloxacin, ciprofloxacin, imipenem, and chloramphenicol. A large proportion (36.67 percent to 96.7 percent) of the S. aureus isolates was resistant to penicillin G, ampicillin, oxacillin, tetracycline, clindamycin, rifampicin, vancomycin, sulfamethoxazole-Trimethoprim and erythromycin. Multiple antibiotic resistance (MAR) phenotypes were generated from 7 S. aureus isolates showing resistance to three or more antibiotics. The mecA, rpoB, blaZ, ermB and tetM genes coding for methicillin, rifampicin, βeta-lactam, erythromycin and tetracycline antibiotics resistance was detected in 5 (22.7 percent), 11 (45.8 percent), 16 (55.2 percent), 15 (71.4 percent) and 8 (72.7 percent) respectively. The PVL, icaA and seaA genes coding for virulent determinants were detected in 50, 20 and 13.3 percent of the confirmed isolates respectively. Physico-chemical and faecal indicator bacteria results obtained from this study can assist municipal authorities in developing appropriate management strategies for beaches in the study area. The findings of this study showed that the investigated beaches were contaminated with toxigenic and multi-drug resistant S. aureus strains. This emphasizes the need for the implementation of better control measures to reduce the occurrence of antibiotic resistant S. aureus and of virulent S. aureus strains in recreational waters. In our study it was established that the potential of recreational waters to be reservoirs of S. aureus should not be taken for granted, and it is important that beach goers be educated about this organism as well as other related pathogens that could affect human health, especially immuno-compromised individuals. The community should be educated on antibiotic stewardship and the detrimental effects of antibiotics abuse.

Staphylococcus aureus is a pulmonary pathogen associated with substantial morbidity and mortality. It is a common complication of influenza and SARS CoV2 infection, chronic obstructive pulmonary disease, cystic fibrosis and is a major cause of ventilator associated pneumonia. The prevalence of this specific organism as a respiratory pathogen has been attributed to its many gene products that thwart innate immunity. However, vaccines targeting virulence determinants have failed to be protective in humans, suggesting that other bacterial or host factors are also critical in pathogenesis. We postulated that S. aureus that are able to persist in the lung must adapt to substrates that are especially abundant. Here we show that among the many potential carbon sources in the infected airway, S. aureus is directed by carbon catabolite repression (CCR) to utilize proline. By following transcriptomic and metabolomic changes over the initial course of infection by human clinical isolates of S. aureus, we established that CcpA and CcpE upregulate expression of the S. aureus collagenase (scpA) and proline transporter (putP). In response to infection, airway fibroblasts synthesize collagen, of which proline is a major component. Host-adapted S. aureus is thus poised to ingest and metabolize newly available proline which fuels oxidative metabolism via the TCA cycle, outcompeting strains that have not made this metabolic transition. Thus, clinical settings characterized by airway repair processes and fibrosis provide a milieu that is intrinsically supportive of S. aureus infection.