Assessment of antibiotic susceptibilities, genotypic characteristics and biofilm-forming abilities of Staphylococcus aureus and Salmonella Typhimurium

초록

This study was designed to evaluate the antibiotic susceptibilities, genotypic characteristics and biofilm formation abilities of antibiotic-sensitive Staphylococcus aureus KACC 13236 (SA(S)), multiple antibiotic-resistant S. aureus CCARM 3080 (SA(R)), antibiotic-sensitive Salmonella Typhimurium KCCM 40253 (STS) and multiple antibiotic-resistant Salmonella Typhimurium CCARM 8009 (STR) cultured in various levels of pHs (4.0, 5.5 and 7.3) and temperatures (4, 20 and 37 degrees C). The SA(S) biofilm cells were highly resistant to ampicillin, cephalothin, oxacillin and piperacillin (MIC90 > 256 mu g/ml) compared with the SA(S) planktonic cells. The STR strain was less susceptible to cephalothin, oxacillin and piperacillin than the STS. The SA(R) strain was positive for the staphylococcal enterotoxin genes (sec, seg, sei, sel, sem, sen and seo). The highest biofilm formation index (BFI) was 2.07 for the SA(R) biofilm cells cultured at 37 degrees C and pH 5.5. The antibiotic-resistant pathogens showed multiple antibiotic resistance, genotypic heterogeneity and cross-protective responses to low pH in the form of biofilms. This study provides useful information for the comparison of antibiotic resistance patterns and biofilm formation abilities between antibiotic-sensitive and resistant pathogens in planktonic and biofilm cells.

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