PBIDI Research Findings

PBIDI Research Findings

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Community-Associated Methicillin Resistant Staphylococcus aureus in South Florida Hospital and Recreational Environments

ABSTRACT

Strains of methicillin-resistant Staphylococcus aureus (MRSA), a frequent human pathogen, may also be found in the flora of healthy persons and in the environments that they frequent. Strains of MRSA circulating in the community classified as USA300 are now found not only in the community but also the healthcare setting, and have emerged as particularly virulent organisms. We have shown that people colonized with S. aureus and MRSA shed these bacteria in their surrounding environment, specifically recreational marine waters. Since there is an increase of serious infections requiring hospitalization caused by USA300, we reasoned that similar organisms could be detected and would predominate among MRSA found in environments utilized by people.

This study collected 154 MRSA isolates from a South Florida hospital patient population diagnosed with S. aureus infections. Sampled patients were evaluated for type and time of onset of infection, and for other contributing factors including previous S. aureus infections. Isolates were characterized via PCR to determine gene profiles for a set of known virulence factors as well as for staphylococcal protein A (spa) and SCCmec type. A selection of 62 hospital SCCmec type IV isolates were evaluated using pulsed-field gel electrophoresis (PFGE) to determine relatedness to characterized USA types. These results were compared to similar analyses of 53 environmental MRSA isolates from South Florida beaches and marine waters.

Results showed that 74% (46 of 62) of the selected hospital isolates and 51% (27 of 53) of the environmental isolates were identical or closely related (> 90% similar) to USA300. When isolates were analyzed for the genes encoding Panton-Valentine leukocidin (PVL) and arginine catabolic metabolic element (arcA), which are often associated with USA300, 60% (93 of 154) of the total hospital isolates were PVL positive and 62% (96 of 154) were arcA positive, whereas 53% (28 of 53) of the environmental isolates were PVL positive and 66% (35 of 53) were arcA positive.

These data indicate that not only is USA300 the predominant MRSA responsible for infections requiring hospitalization in this South Florida location but that it is present in the waters of local beaches.

AUTHORS

Suzanne Hower(1), Chanchal Newton(5), Charlene R. Jackson(3), John B. Barrett(3), Antonio J. Bustillo(1), Gordon M. Dickinson(2,4,5), Lisa R.W. Plano1(5), Istvan Krisko(5)

(1)Department of Microbiology and Immunology, University of Miami Miller School of Medicine, Miami, FL (2)Division of Infectious Diseases, Department of Medicine, University of Miami Miller School of Medicine, Miami, Florida, (3)Bacterial Epidemiology and Antimicrobial Resistance Research Unit, Richard B. Russell Research Center, Agricultural Research Service, US Department of Agriculture, Athens, GA, (4)Medical Services, Veterans Affairs Medical Center, Miami, Florida, (5)Palm Beach Infectious Disease Institute, Jupiter, FL