![]() ![]() The representative USA300 strains were spa type t008 (YHGFMBQBLO), and USA400 strains were spa type t128 (UJJFKBPE). The first isolate and a randomly selected second isolate of USA300 and USA400 clonal groups were determined to be sequence type (ST) 8 and ST1, respectively. PFGE analysis grouped these isolates into 2 clonal groups, USA400 (n = 7, 47%) and USA300 (n = 8, 53%) ( Figure 2). MLST, multilocus sequence typing SCC mec, staphylococcal cassette chromosome mec NA, not available ND, not determined. Strain numbers, clone identification, site of infection, and demographic information are included along each PFGE lane. A genetic similarity index scale is shown above the dendrogram. Pulsed-field gel electrophoresis (PFGE)–based dendrogram of methicillin-resistant Staphylococcus aureus strains isolated during the outbreak. All 15 isolates were resistant to β-lactams but sensitive to ciprofloxacin, gentamicin, rifampicin, tetracycline, trimethoprim-sulfamethoxazole, and vancomycin. Dates of incarceration for 2 inmates could not be determined. All patients, except for inmate Y08, who entered the facility in the seventh month of the outbreak ( Figure 1), were incarcerated for 3 to 56 months before the outbreak. Only the first isolate of each PFGE-based clonal group and 1 additional isolate from the same clone were analyzed with spa and multilocus sequence typing.Īll 15 patients were men (average age 39 years) and had SSTIs at various body sites ( Figure 2). ![]() Codes below months represent patients.Īll strains were typed by pulsed-field gel electrophoresis (PFGE) and staphylococcal cassette chromosome mec (SCC mec) and tested for virulence genes. Month 0 and month numbers with – and + symbols represent the respective months of incarceration before and after onset of the outbreak, respectively. Bottom panel: horizontal line shows duration in which patients were incarcerated in relation to the outbreak period. Top panel: baseline shows months in which a particular isolate was recovered and patient was identified as infected y-axis shows number of patients in each clonal group per month during the outbreak period. Timeline of incarceration and isolation of methicillin-resistant Staphylococcus aureus isolates from different patients. This outbreak was caused by USA400 strains but appeared to be displaced by USA300 clonal group after it was introduced into the facility. In this retrospective study, we report an outbreak of CA-MRSA–associated skin and soft tissue infections (SSTIs) among inmates of a medium-size correctional facility in Wisconsin. Molecular typing of strains from these recent outbreaks showed that most differed from the predominant clone of the 1990s and belonged to a new CA-MRSA clone, USA300 ( 9). More recently, CA-MRSA outbreaks were seen in unsuspected groups such as military personnel ( 6, 7), athletes ( 8, 9), and inmates at large correctional facilities ( 10, 11). In the 1990s, outbreaks of CA-MRSA–related infections occurred primarily in certain groups, such as Native Americans, before disseminating into the general population ( 1 – 5). These risk factors have enabled CA-MRSA to infect persons who meet >1 of these criteria. Also, risk factors for acquiring CA-MRSA infections differ from those for acquiring HA-MRSA and include crowding, close contact, lack of cleanliness, compromised skin, and contaminated fomites. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is phenotypically and genotypically different from healthcare-associated MRSA (HA-MRSA). ![]()
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