MOLECULAR EPIDEMIOLOGY OF COMMUNITY-ASSOCIATED METHICILLIN-RESISTANT STAPHYLOCOCCCUS AUREUS (CA-MRSA) INFECTIONS IN ISRAEL

Background+aim: Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) causes significant morbidity+mortality in the USA; infections are caused almost exclusively by a single clone-USA300. MRSA are defined by the mecA gene carried by the Staphylococcal chromosome cassette mec (SCCmec); USA300 are typically SCCmecIV and Panton-Valentine-leukocidin (PVL) toxin+. We aimed to study the epidemiology of CA-MRSA in Israel, where data are scarce.

Methods: During 4/2011-10/2013, all community-onset MRSA clinical isolates from Maccabi Healthcare Services (representing~30% of Israeli population), were collected prospectively. Demographic+clinical data were recorded, antibiotic susceptibility determined, and PCR performed for mecA, SCCmec, and PVL. PCR for additional toxins and spa type were performed for SCCmecIV/V isolates.

Results: MRSA were detected in 280 patients: SCCmecI-III, IV and V in 133(47%), 120(43%), and 27(10%) patients, respectively. Skin and soft tissue infections (SSTI`s) were the major source of culture. Rates of hospitalizations were higher for patients with SCCmecI-III isolates compared with SCCmecIV/V (61% vs. 40%, p=0.0007). SCCmecIV patients were younger (p<0.0001, 77% of all children). Almost all isolates were trimethoprim-sulfamethoxazole susceptible (98%). Clindamycin resistance rates were lower in SCCmecIV/V isolates compared with SCCmecI-III (35% and 26% vs. 95%, respectively, p<0.0001). The 3 major SCCmecIV clones were EMRSA15(13%), USA300(13%), and t991(10%); all were distributed throughout Israel. Strain t991 was eta+ and isolated mostly from children (75%). PVL+ strains (n=31) included mainly USA300 (52%) and ST30 (14%).

Conclusions: In this first large-scale nationwide study, multiple genetic lineages are evident among community-onset MRSA. Approximately 20% are typical CA-MRSA clones emphasizing the importance of the CA-MRSA phenomenon in Israel. CA-MRSA isolates, mainly USA300 and t991, were detected throughout Israel, particularly from SSTI`s. Urgent interventions to stop the spread of CA-MRSA in Israel are needed.