COMPARATIVE VIRULENCE ANALYSIS OF COMMUNITY- ASSOCIATED AND HEALTHCARE-ASSOCIATED METHICILLIN-RESISTANT Staphylococcus aureus STRAINS CIRCULATING IN ARGENTINA USING THE Galleria mellonella MODEl

BLANCATO, VÍCTOR S., AND MAGNI, CHRISTIAN

CABA

Congreso; saib 2017; 2018

SAIB

Community-associated MRSA (CA-MRSA) strains are genotypicallydistinct from healthcare associated MRSA (HA-MRSA), andthere is evidence that CA-strains have a more virulent clinical phenotypethan HA-MRSA strains causing infection. Nevertheless, inArgentina the behaviour of the circulating strains remains unclear.We aimed to analyse virulence between a representative collectionof CA- and HA-MRSA strains recovered throughout Argentina since1999 in an in vivo Galleria mellonella killing model. MRSA were studiedby SCCmec and spa-typing, PVL, PFGE and MLST. CA-MRSAisolates [I-ST5-IVa t311 PVL+ (n=2), N-ST30-IVc t019 PVL+ (n=2)and USA300-ST8-IV t008 PVL+ (n=2)] and HA-MRSA isolates[A-ST5-I t149 (n=2) and B-ST239-III t037 (n=2)] were analysed. 8caterpillars were inoculated in triplicate with 5 μl (6x108 CFU/ml) ofeach strain and incubated at 37°C and observed every 24 h for 80 h.Log-rank tests were used to compare Kaplan?Meier survival curvesfor all CA-MRSA vs HA-MRSA strains and for all clonal groups. Statisticalanalysis showed that CA strains killed more larvae than HAstrains (P0.05). Although, the USA300 clone killed G. mellonellalarvae more quickly than N or I strains (mean survival time, 47 hfor USA300 vs 64 h for N and I strains, P=0.051), there were no significantdifferences between the CA strains. We also analysed separatelythe most prevalent CA clones in Argentina (N and I strains),excluding USA300 strains vs. the most prevalent HA clones (A andB strains).This analysis, also showed that CA clones killed morelarvae than HA clones (P