Comparative Virulence Analysis of Community-Associated and Healthcare-Associated Methicillin-Resistant Staphylococcus aureus Strains Circulating in Argentina using the Galleria mellonella Model

SOLA C.; MAGNI C.; BARCUDI D.; BLANCATO V.; EGEA A. L.; BOCCO J.L.; MARTINO G.

Buenos Aires

Congreso; Reunión Conjunta de Sociedades de Biociencias 2017; 2017

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Community-associated MRSA (CA-MRSA) strains are genotypically distinct from healthcare associated MRSA (HA-MRSA), and there is evidence that CA-strains have a more virulent clinical phenotype than HA-MRSA strains causing infection. Nevertheless, in Argentina the behaviour of the circulating strains remains unclear. We aimed to analyse virulence between a representative collection of CA- and HA-MRSA strains recovered throughout Argentina since 1999 in an in vivo Galleria mellonella killing model. MRSA were studied by SCCmec and spa-typing, PVL, PFGE and MLST. CA-MRSA isolates [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. 8 caterpillars were inoculated in triplicate with 5 μl (6x108 CFU/ml) of each strain and incubated at 37°C and observed every 24 h for 80 h. Log-rank tests were used to compare Kaplan?Meier survival curves for all CA-MRSA vs HA-MRSA strains and for all clonal groups. Statistical analysis showed that CA strains killed more larvae than HA strains (P0.05). Although, the USA300 clone killed G. mellonella larvae more quickly than N or I strains (mean survival time, 47 h for USA300 vs 64 h for N and I strains, P=0.051), there were no significant differences between the CA strains. We also analysed separately the most prevalent CA clones in Argentina (N and I strains), excluding USA300 strains vs. the most prevalent HA clones (A and B strains).This analysis, also showed that CA clones killed more larvae than HA clones (P