Clones and toxin gene profiles of methicillin-resistant Staphylococcus aureus causing infections among children and adults

Abstract number: P1578

Drougka E., Koureli O., Petinaki E., Obasuyi O., Foka A., Chini V., Giormezis N., Athanassiadou A., Anastassiou E.D., Spiliopoulou I.

Objective: Methicillin-resistant Staphylococcus aureus (MRSA) infections and especially community-associated (CA-MRSA), including superficial, deep-seated infections and pneumonia, are widespread among adults and children in Greece. CA-MRSA usually carry the genes encoding Panton-Valentine leukocidin (PVL). We have investigated and compared the distribution and clonal evolution of CA-MRSA during 2006–2008 among adults and children in Greece.

Methods: A total of 800 MRSA were isolated from clinical specimens of infected patients from January 2006 till September 2008 in a tertiary teaching and a paediatric hospital in South Greece. Isolates were identified at species level by conventional tests, followed by the determination of MIC of oxacillin by the Etest (AB Biodisk) and their antibiotic resistance patterns to antistaphylococcal agents by the disk diffusion method. PBP2a production was investigated by a Latex agglutination test (bioMerieux). The genes: mecA (encoding PBP2a), lukS and lukF (encoding PVL), tst (encoding toxic shock syndrome toxin), sem/seg (of the enterotoxin gene cluster egc) and agr groups were defined by PCRs with specific primers. Clones were determined by PFGE of chromosomal DNA SmaI digests and MLST. CA-MRSA were isolated from patients without any predisposing risk factors.

Results: Four hundred and seventy-three MRSA were recovered from adults, and 327 from children. The majority were CA-MRSA (80% among adults and 99% from children). Genes encoding PVL were detected in 408 strains (86%) from adults and 312 (95%) from children, belonging to ST80 and ST377 clones. Genes of the superantigens' family (tst and/or egc) were identified among 11% and 7% of adults and children, respectively. PVL-negative strains were classified into ST239, ST30, ST22, ST225, ST585 clones. Multi-resistant strains were identified among adults.

Conclusions: PVL-positive MRSA are widely distributed in Greece, mainly among children and to less extend in the adults, causing soft skin and tissue infections but also osteomyelitis and pneumonia. Most of the cases are community-associated belonging to two clones, reinforcing the aspect of an epidemic that needs application of infection control measures.