Molecular epidemiology of Community-Acquired MRSA causing invasive disease in Argentina in 2010 and 2011

FERNÁNDEZ S; GARDELLA N; DI GREGORIO S; LOPEZ FURST MJ; DE VEDIA L; STRYJEWSKI ME; GANAHA MC; PRIETO S; CARBONE E; LISTA N; ROTRYING F; MOLLERACH M

San Francisco

Conferencia; 52nd Interscience Conference on Antimicrobial Agentes and Chemotherapy; 2012

American Society for Microbiology

Background Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) has become a major concern worldwide. We conducted a prospective multicenter study of invasive CA-MRSA infections to evaluate genotypecharacteristicsof strains causing such infections in Argentina. Methods Patients ≥14 years-oldwithout significant healthcare contact presenting with invasive CA-MRSA infections defined by positive culture recovered from normally sterile body sites between March 2010 and December 2011 were included. Antimicrobial susceptibility testing was performed according to CLSI. Detection of mecA, agr, Panton-Valentine (PVL) gene and SCCmec typing were done by PCR. Isolates were genotyped by spa typing, PFGE and MLST. Results Fifty five patients with CA-MRSA invasive infections were enrolled at 11 centers. Mean age was 34 (±15) years; 36% of patients received antibacterials within the last 6 months. MRSA isolates were more commonly obtained from blood (n=32), skin structures (n=14), lower respiratory tract (n=9) and muscles (n=9).Overall 42% of patients required ICU and 16% died. Most isolates were usually susceptible to erythromycin (91 %), clindamycin (94 %), gentamicin (89 %), quinolones (96 %), and all were susceptible to vancomycin, linezolid and trimethoprim/sulfamethoxazol . Among 28 clinical isolates available for molecular studies, 19 belonged to clone ST30, SCCmec type IVc, t019, agr III, PVL positive, and 2 to clone ST5, SCCmecIVa, t311, PVL positive, agr II. The lineage ST 72, agrI (2/28) was associated with t1346 (SCCmec IV, PVL positive) and t148 (SCCmec IV variant harboring tnp20 integrated between ΔmecR1 and IS1272, PVL negative). Conclusions This study revealed that ST30 CA-MRSA clone has replaced ST5 clone previously described as the most prevalent in Argentina. This is also the first report of SCCmec IV variant containing tnp20 in our country.