First Isolation of SCCmec IV- and Panton-Valentine Leukocidin-Positive, Sequence Type 8, Community-Associated Methicillin-Resistant Staphylococcus aureus in Israel

In the past decade, the perception of methicillin-resistant Staphylococcus aureus (MRSA) has changed. No longer confined to hospital environments or isolated only from patients with identifiable risk factors, MRSA strains now circulate in the community among previously healthy patients. In large areas of the United States, these community-associated MRSA (CA-MRSA) strains have become endemic and surpassed the prevalence of methicillin-susceptible Staphylococcus aureus infections (2, 3). USA300 is currently the predominant CA-MRSA strain in the United States, responsible for a large disease burden and for severe manifestations of infections such as severe sepsis, necrotizing pneumonia, and necrotizing fasciitis (2, 3, 9). Infections caused by CA-MRSA strains were reported from other areas of the world as well (8).

As opposed to the large disease burden caused by CA-MRSA in the United States, there is a paucity of data about CA-MRSA disease and molecular characteristics in Israel and, specifically, in the pediatric Israeli population. The common belief is that CA-MRSA disease is rare. The first report about CA-MRSA disease in children in Israel was recently published (5). We now report what we believe is the first CA-MRSA isolate in Israel with molecular characteristics similar to those of the widely disseminated USA300 clone in the United States.

In 2007 to 2008, we conducted a 1-year prospective surveillance study for infections caused by S. aureus strains among hospitalized children in the Western Galilee region in northern Israel (5). Of the 59 pediatric patients with S. aureus skin and soft tissue infections, 5 cases were found to be caused by CA-MRSA isolates, defined as non-multidrug-resistant MRSA isolates cultured within 72 h of admission. The calculated prevalence of CA-MRSA infections within the study period was 76 cases for 100,000 admissions. One of these patients, a previously healthy, 9-month-old child was hospitalized due to two small skin abscesses in the neck and upper back after varicella. The abscesses were drained, and the culture grew S. aureus resistant only to β-lactam antimicrobials and erythromycin. Clindamycin susceptibility was determined by the VITEK2 automated system (bioMérieux Vitek, Inc., Durham, NC) and by the D-zone test. The isolate was found to harbor staphylococcal cassette chromosome mec type IV (SCCmec IV) and carry the genes for the Panton-Valentine leukocidin toxin (pvl positive [pvl⁺]). Multilocus sequence typing (MLST) identified this isolate as sequence type 8 (ST8). The laboratory methods were performed as described elsewhere (4, 6, 10). The child and his family members were previously healthy, without recurrent skin infections, and did not travel outside Israel.

There are only a few reports regarding CA-MRSA carriage and disease in Israel. Two pediatric CA-MRSA isolates found in a nasal carriage study in central Israel in 2002 were typed as SCCmec IV, ST45, pvl negative (7). A recent report about MRSA nasal colonization conducted in the south of Israel found 45 of 659 infants to be colonized with CA-MRSA strains; colonization predominated among Bedouin infants (1). A new clonal complex (CC), CC-913, was found among 64% of the infants; the isolates carried SCCmec IV but not the PVL genes and belonged to ST types ST912, ST913, and ST914. None of the colonizing isolates belonged to ST8. The study also included 4 CA-MRSA isolates from pediatric patients with MRSA infections. Two were ST913, and 2 were ST80, SCCmec IV, pvl⁺.

Our finding of a significant rate of infections caused by CA-MRSA, combined with molecular characteristics similar to those of the virulent and successful USA300 lineage, highlights the need for urgent multicenter and community surveillance studies in Israel. Awareness and recognition by culturing are the crucial steps in the process of investigating the problem of CA-MRSA. The old-school thinking of MRSA being solely a hospital-based pathogen, in patients with modifying conditions or frequent exposure to the health care system, is no longer valid in Israel.