Biofilm formation of two genetically diverse Staphylococcus aureus isolates under beta-lactam antibiotics
Jinglong Liang, Teng Yi Huang, Yuzhu Mao, Xuejie Li
Abstract
Purpose Our aim was to evaluate the biofilm formation of 2 genetically diverse Staphylococcus aureus 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 mec 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 icaD , icaBC , and MRSA genes, not the icaA , atl , app , and agr genes, and MLST and SCC mec typing was ST45 and IV, respectively. Strain 121940 carried the icaA , icaD , icaBC , atl , and agr genes, not the aap gene, and MLST and SCC mec typed as ST546 and IV, respectively. This suggested that strains 10379 and 121940 were genotypically very different. Two S. aureus 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 S. aureus 10379 and 121940, some sub-inhibitory concentrations of beta-lactam antibiotics are able to promote biomass and biofilm viability of both two isolates.