Comparison of the performance of Disk diffusion, Agar screening and E-test methods with Real- time PCR for the detection of methicillin resistant coagulase negative Staphylococcus strains isolated from clinical samples of Shahrekord university hospitals, 2008

摘要

Backgroundud: Coagulase Negative staphylococci (CoNS) are nosocomial pathogens. The main objectiveudof the study was to compare the performance of disk diffusion, E-test and agar screening methods withudReal-time PCR technique for detection of methicillin resistance in coagulase negative staphylococciud(MRCoNS), using Taqman® Real-time PCR for mecA DV WKH ³ JROG VWDQ GDUG´ FRP SDULVRQ DVVD � udMethodsud: 88 coagulase negative Staphylococcus isolates were identified out of 284 Staphylococcus isolatesudcollected from Hajar and Kashani hospitals-shahrekod, Iran. Methicillin resistance strains were identified byudseveral methods: Disk diffusion, Agar screening, E-test and Real-time PCR. The results of the tested methodsudZHUH FRP SDUHG ZLWK WKRVH RI WKH 5 HDO� WLP H 3& 5 E & KL VTX DUH RU ) LVKHU¶ V H[ DFW WHVWV� udResultsud: Of the 88 coagulase negative Staphylococcus isolates tested, 46 isolates (52.3%) were mecAud-udpositive and 42 isolates (47.7%) were mecA-negative. The results of all the tested methods had a statisticallyudsignificant agreement with those of Real-time PCR. The E-test was 100% sensitive and specific for mecAudpresence. The sensitivity and specificity of oxacillin agar screen (6.0 µg/ml) method were 96% and 98%,udrespectively and the sensitivity and specificity of oxacillin Disk diffusion method were 91% and 90%,udrespectively.udConclusion: In the present study, E-test is proposed as the best phenotypic method. In case economicudissue matters, the oxacillin agar screening method (6.0 µg/ml), which is suitable for the detection ofudMRCoNS due to its accuracy and low cost, is recommended.udKeywordsud: methicilli