Staphylococcus aureus (SA) is a commensal bacterium and opportunistic pathogen commonly associated with humans and is capable of causing serious disease and death including sepsis, pneumonia, and meningitis. Methicillin-resistant SA (MRSA) isolates are typically resistant to many available antibiotics with the common exception of vancomycin. The presence of vancomycin resistance in some SA isolates combined with the current heavy use of vancomycin to treat MRSA infections indicates that MRSA may achieve broad resistance to vancomycin in the near future. New MRSA treatments are clearly needed. Bacteriophages (phages) are viruses that infect bacteria, commonly resulting in death of the host bacterial cell. Phage therapy entails the use of phage to treat or prevent bacterial infections. In this study, 12 phages were isolated that can replicate in human SA and/or MRSA isolates as a potential way to control these infections. 5 phage were discovered through mitomycin C induction of prophage and 7 others as extracellular viruses. Primary SA strains were also isolated from environmental sources to be used as tools for phage discovery and isolation as well as to examine the target cell host range of the phage isolates by spot testing. Primary isolates were tested for susceptibility to oxacillin in order to determine which were MRSA. Experiments were performed to assess the host range and killing potential of newly discovered phage, and significant reductions in bacterial load were detected. We explored the utility of some phage to decontaminate fomites (glass and cloth) and found a significant reduction in colony forming units of MRSA following phage treatment, including tests of a phage cocktail against a cocktail of MRSA isolates. Our findings suggest that phage treatment can be used as an effective tool to decontaminate human MRSA from both hard surfaces and fabrics.

The frequent use of antibiotics contributes to antibiotic resistance in bacteria, resulting in an increase in infections that are difficult to treat. Livestock are commonly administered antibiotics in their feed, but there is current interest in raising animals that are only administered antibiotics during active infections. Staphylococcus aureus (SA) is a common pathogen of both humans and livestock raised for human consumption. SA has achieved high levels of antibiotic resistance, but the origins and locations of resistance selection are poorly understood. We determined the prevalence of SA and MRSA in conventional and antibiotic-free (AF) meat products, and also measured rates of antibiotic resistance in these isolates. We isolated SA from raw conventional turkey, chicken, beef, and pork samples and also from AF chicken and turkey samples. We found that SA contamination was common, with an overall prevalence of 22.6% (range of 2.8–30.8%) in conventional meats and 13.0% (range of 12.5–13.2%) in AF poultry meats. MRSA was isolated from 15.7% of conventional raw meats (range of 2.8–20.4%) but not from AF-free meats. The degree of antibiotic resistance in conventional poultry products was significantly higher vs AF poultry products for a number of different antibiotics, and while multi-drug resistant strains were relatively common in conventional meats none were detected in AF meats. The use of antibiotics in livestock contributes to high levels of antibiotic resistance in SA found in meat products. Our results support the use of AF conditions for livestock in order to prevent antibiotic resistance development in SA.

Staphylococcus aureus (SA) is an important human pathogen, causing potentially lethal infections of the blood, skin, and lungs. SA is becoming increasingly difficult to treat due to high levels of antibiotic resistance, and new treatments are needed. SA is able to evade antibiotics and immune surveillance through biofilm development. Biofilms are communities of microorganisms that are able to prevent the entry of antimicrobials and immune cells. Biofilms are also involved in SA transmission because biofilms can form on medical devices. In this study, we tested silver nanoparticles and vancomycin for their anti-biofilm effects on SA. We used 10 different SA isolates, representing a spectrum of biofilm-forming ability, and a crystal violet assay to measure biofilm mass. 2μg/mL vancomycin treatment resulted in a significant reduction in established SA biofilms in 7/10 isolates, including 4/5 methicillin susceptible SA (MSSA) and 3/5 methicillin-resistant (MRSA) isolates (mean reduction in crystal violet stain of 13.0%; high of 26.5% and low of 0%). Silver nanoparticle treatment of SA biofilms resulted in a significant reduction in 6/10 isolates, including 4/5 MSSA and 2/5 MRSA (mean reduction of 8.7%; high of 21.2% and low of 0%). A combinatorial treatment with silver nanoparticles and vancomycin resulted in significant reductions in 9/10 isolates (mean reduction of 20.8%; high of 39.3% and low of 0%). We conclude that both vancomycin and silver nanoparticle treatment of established tissue culture-based SA biofilms result in significant reductions in biofilm mass, with a combinatorial treatment even more effective than either treatment alone.

The frequent use of antibiotics contributes to antibiotic resistance in bacteria, resulting in an increase in infections that are difficult to treat. Livestock are commonly administered antibiotics in their feed, but there is current interest in raising animals that are only administered antibiotics during active infections. Staphylococcus aureus (SA) is a common pathogen of both humans and livestock raised for human consumption. SA has achieved high levels of antibiotic resistance, but the origins and locations of resistance selection are poorly understood. We determined the prevalence of SA and MRSA in conventional and antibiotic-free (AF) meat products, and also measured rates of antibiotic resistance in these isolates. We isolated SA from raw conventional turkey, chicken, beef, and pork samples and also from AF chicken and turkey samples. We found that SA contamination was common, with an overall prevalence of 22.64% (range of 2.78-30.77%) in conventional meats and 13.0% (range of 12.5-13.2%) in AF poultry meats. MRSA was isolated from 15.72% of conventional raw meats (range of 2.78-20.41%) but not from AF-free meats. The degree of antibiotic resistance in conventional poultry products was significantly higher vs AF poultry products for a number of different antibiotics, and while multi-drug resistant strains were relatively common in conventional meats none were detected in AF meats. The use of antibiotics in livestock contributes to high levels of antibiotic resistance in SA found in meat products. Our results support the use of AF conditions for livestock in order to prevent antibiotic resistance development in SA.