항생제 내성과 IS256유전자를 지닌 임상분리 균주 Staphylococcus aureus 에서의 균막 형성의 증가

Abstract

The formation of biofilms is a major contributing factor to nosocomial infections, which are often associated with the colonization of Staphylococcus aureus on the surfaces of medical devices. In order to elucidate the correlation between the antibiotic resistance, which is determined by a standard antibiotic susceptibility test to planktonic cells, and the formation of biofilm with sessile growth, we performed a biofilm assay on 96-well polystyrene plate, coupled with an antibiotic susceptibility test of 30 antibiotics, using a Vitek II automatic system for 101 clinical isolates S. aureus. In addition, the presence of IS256 element, which is involved in antibiotic resistance as well as phase variation in S. aureus biofilm formation, was determinated by PCR. Of the 101 isolates tested, the frequency of biofilm positivity was 29.7%, and that of IS256 presence was 67.3%. The statistical analysis indicated that the strain that were either individual resistance against 18 antibiotic or multiresistance displayed a significantly higher prevalence of biofilm formation and of IS256 presence than those susceptible. Moreover, the IS256-harboring strains exhibited a significantly higher prevalence of biofilm formation than those without IS256. Also, the MRSA strains shower a higher frequency of biofilm positivity than the MSSA strains. In conclusion, we noted triangular correlations between the presence of IS256, the antibiotic resistance and the formation of biofilm. This suggests that antibiotic-resistant S. aureus strain are more probable to develop biofilms on medical devices, which renders them more difficult to eradicate by conventional chemotherapy.