Biofilm formation of two genetically diverse isolates under beta-lactam antibiotics.

PURPOSE

Our aim was to evaluate the biofilm formation of 2 genetically diverse isolates, 10379 and 121940, under different concentrations of beta-lactam antibiotics on biomass content and biofilm viability.

METHODS

Biofilm formation and methicillin resistance genes were tested using PCR and multiplex PCR. PCR was combined with bioinformatics analysis to detect multilocal sequence typing (MLST) and SCC types, to study the genetical correlation between the tested strains. Then, the crystal violet (CV) test and XTT were used to detect biomass content and biofilm activity. Antibiotic susceptibility was tested using a broth dilution method. According to their specific MIC, different concentrations of beta-lactam antibiotics were used to study its effect on biomass content and biofilm viability.

RESULTS

Strain 10379 carried the , , and MRSA genes, not the , , , and genes, and MLST and SCC typing was ST45 and IV, respectively. Strain 121940 carried the , , , , and genes, not the gene, and MLST and SCC typed as ST546 and IV, respectively. This suggested that strains 10379 and 121940 were genotypically very different. Two isolates, 10379 and 121940, showed resistance to beta-lactam antibiotics, penicillin, ampicillin, meropenem, streptomycin and kanamycin, some of which promoted the formation of biofilm and biofilm viability at low concentrations.

CONCLUSION

Despite the large differences in the genetic background of 10379 and 121940, some sub-inhibitory concentrations of beta-lactam antibiotics are able to promote biomass and biofilm viability of both two isolates.