Antimicrobial resistance genotypes and phenotypes from multidrug-resistant bacterial wound infection isolates in Cambodia

• 31 human wound isolates were analysed for >230 antimicrobial resistance determinants.
• The macrolide resistance gene erm(B) was observed in 70% of staphylococci, whilst erm(A) was not detected.
• Genes encoding TEM and CTX-M-1 β-lactamases were detected in >75% of the Enterobacteriaceae isolates.
• An Enterobacter cloacae isolate was positive for the presence of lnu(F)/lin(F) and lnu(G)/lin(G) which, while not clinically relevant, may facilitate epidemiological mapping.
• Quinolone resistance determinants (qnrB, qnrS) were detected in 22% of Enterobacteriaceae isolates.

This study aimed to identify the molecular determinants responsible for antibiotic resistance among human wound isolates in Cambodia. Staphylococcus spp. (n = 10) and a variety of Gram-negative isolates (n = 21) were taken from a larger collection of wound isolates collected during 2011–2013 and were analysed for the presence of >230 resistance determinants using a broad-spectrum DNA microarray. These isolates were chosen to represent the species most commonly found in wound isolates referred during this time and to include some of the most resistant strains. Resistance determinants detected among the staphylococci included blaZ (90%), mecA (100%), erm(B) (70%), erm(C) (20%), tet(38) (90%), tet(K) (40%), tet(Lp) (10%), tet(M) (20%), lnu(A)/lin(A) and lnu(B)/lin(B) (10% each), msr(A)/msr(B)/msr(SA) (10%), norA (80%) and dfrA (10%). Eleven different β-lactamase genes were detected among the Gram-negative bacteria, including genes encoding the TEM (48%), CTX-M-1 (48%), CTX-M-9 (5%), SHV (5%) and VEB (10%) families of broad-spectrum and extended-spectrum β-lactamase enzymes, as well as the carbapenemase gene blaOXA-23. Forty additional genes were also detected in the Gram-negative isolates conferring resistance to aminoglycosides (11 genes), phenicols (5 genes), macrolides [4 genes, including mph(A)/mph(K) (10%)], lincosamides [lnu(F)/lin(F), lnu(G)/lin(G)], tetracycline (4 genes), rifampicin [arr (29%)], quaternary amines [qacEΔ1 (43%)], quinolones [qnrS (14%) and qnrB (5%)], sulfonamides [sul1 (29%), sul2 (38%) and sul3 (10%)], streptothricin (sat2) and trimethoprim (6 genes). The results obtained here provide a snapshot of the broad variety of resistance determinants currently circulating within Cambodia.