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

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

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 (P<0.001) and there were no significant differences by CA or HA clones (P>0.05). 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<0.018). These results demonstrate that there are differences regarding virulence in the most prevalent CA and HA-MRSA strains circulating in Argentina and suggest that the increased virulence phenotype of these clones could be associated with increased killing in G. mellonella virulence model.