Comparison of disc and MIC reduction methods with polymerase chain reaction for the detection of metallo-β-lactamase in Pseudomonas aeruginosa.
OBJECTIVE
The present study was undertaken to evaluate the screening antibiotic, confirmatory phenotypic test and agent against PCR as gold standard and to detect the prevalent MBL gene.


METHODS
Three hundred and twenty-six Pseudomonas aeruginosa isolates were screened for resistance to Imipenem (IPM), Meropemem (MEM) and Ceftazidime (CAZ) by disc diffusion. Isolates resistant to any of these were considered screen test-positive for MBL and were subjected to Double disc synergy test (DDST) and Disc potentiation test (DPT: Using IPM, MEM and CAZ alone and with EDTA), Minimum inhibitory concentration (MIC) reduction [four-fold or more reduction in MIC of IPM and MEM in presence of chelators: EDTA and 1,10-phenanthroline (EPI/EPM: EDTA-phenanthroline- Imipenem/Meropenem Broth Microdilution method)] and polymerase chain reaction (PCR) for blaIMP and blaVIM .


RESULTS
Screen test-positives by MEM and CAZ were 19.3% as against 17.8% by IPM. MEMDDST, DPT and EPM confirmed 100% screen-test positives as against 93.7% by CAZ DDST and DPT-2, 76.2% by CAZ DPT-1, 88.9% by IPM DDST, 85.7% by IPM DPT-1 and 92.1% by EPI. IPMand CAZ DDST together confirmed 100% while IPM and CAZ DPT-2 confirmed 96.8%. All 63 screen-test positives showed the presence of blaVIM .


CONCLUSIONS
MEM was found to be the best screening and confirmatory agent for MBL detection and blaVIM was found to be the prevalent MBL gene in this part of the country.
Department of Microbiology, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha, Maharashtra, India.
S
S
Buchunde
D K
DK
Mendiratta
V
V
Deotale
P
P
Narang
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D016133:Polymerase Chain Reaction / Q000379:methods*; D011552:Pseudomonas Infections / Q000382:microbiology; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics* / Q000302:isolation & purification; D012680:Sensitivity and Specificity; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases