Fifty eight strains of Staphylococcus auresu(S. aureus) isolated from Yeungnam University Hospital and 143 strains preserved in department of microbiology, Yeungnam University, College of Medicine were used for methichilin resistant. S
aureus(MRSA)
isolation by the in vitro susceptibility test.
Multiple resistant patterns to 6 antimicrobial agents (methicillin, kanamycin, erythormycin, cephalothin, chrolamphenicol, vancomycin) for the isolated MRSA, Minimal Inhibitory Concentration (MIC) to methicillin and the identification of MRSA by
polymerase chain reaction(PCR) were tested.
The coagulase test result was affected by both the incubation time and the human plasma dilution ratio. Coagulation was observed more clearly in 24 hours than 4 hours of incubation(P<0.01) and tin the 1:3 and 1:5 dilutions over than 1:1 dilution.
In the susceptibility test, all of the test strains were susceptible to vancomycin. However, 55.7% of strains were found to be resistant to methicillin. The MIC50 and MIC90 to methicillin of these Mrsa Strains were over 64μl/ml and 128μl/ml,
reespectivelyl One hudred two(91.1%) MRSA strains out of one hundred twelve strains shosed multiple resistant patterns more than two antimicrobial agents.
Results obatined by PCR was compared with those obtained by susceptibility test. Thirteon strains of MRSA obtained by susceptibility test were tested by PCR. All 13 strains showed 528bp DNA amplification by PCR. Eight strains among 19 strains of
methicillin susceptible S. aureus obtaind by susceptibility test also showed 528bp Dna amplification. The 528dp DNA was confirmed, by Nde I digestion, which showed 404fdp and 124dp DNA. This result showed that the 528dp DNA is a part of mecA
gene.
Our result showes that the identification of MRSA by PCR offers a very sensitive alternative tool to traditional susceptibility tests. As a guide for treatment of infection caused by Staphylococcus aureus.
|