RESUMO
OBJECTIVES: Detection and comparison of metallo-ß-lactamase (MBL) production in clinical isolates by phenotypic and genotypic measures. The objective of this study is to evaluate clinical characteristics and risk factors in patients infected with MBLs. MATERIALS AND METHODS: Study was conducted by the Department of Microbiology, Jawaharlal Nehru Medical College from February 2014 to December 2015. Bacterial culture, identification, and antibiotic susceptibility were carried out according to standard guidelines. MBL production was detected both phenotypically (Modified Hodge test [MHT], imipenem-ethylene diamine tetraacetic acid double disk potentiation test [IMP-EDTA DDPT], IMP-EDTA combined disk synergy test [IMP-EDTA CDST]), and genotypically (blaNDM-1, blaVIM and blaIMP). RESULTS: Among 116 carbapenem-resistant Gram-negative Bacilli (CRGNB), Citrobacter species 28 (24.1%) was the most common pathogen. Phenotypically, MHT, IMP-EDTA DDPT, and IMP-EDTA CDST detected MBL production in 105 (90.5%), 96 (81%), and 87 (75%) CRGNB, respectively. BlaNDM-1 genes were detected in 6 6 (56.8%) isolates, however, very few blaVIM (16, 15.2%) and blaIMP (1, 1.2%) were identified. Considering polymerase chain reaction (PCR) as the gold standard, it was observed that IMP-EDTA CDST was most specific (78.3%) while MHT was most sensitive (97.4%). Results of blaNDM-1 gene by PCR were further confirmed by sequencing (Triyat genomics, Nagpur). All the 11 representative strains were confirmed to be NDM-1 gene. Major risk factors in patients infected with MBLs were in-dwelling devices (68%), prolonged hospital stay (72%) and prior antibiotic treatment (86%). However, on tracing their outcome, it was interesting to note that mortality was relatively low 5 (4.3%). CONCLUSION: The present study shows a rising trend of blaNDM-1 in CRGNB, an ominous sign heralding the post antibiotic era. It is essential to assess the prevalence of various MBLs so that infection control measures can be reinforced. We recommend three phenotypic tests in tandem for the detection of MBL. While phenotypic tests are easy and cost-effective to perform, quick, effective molecular diagnostic techniques can tailor treatment guidelines to optimize patient's management.
RESUMO
INTRODUCTION: This study was conducted to assess the prevalence of metallo-beta-lactamases (MBLs) in general and blaNDM-1 in particular. It also aimed at evaluating clinical characteristics and outcome in patients infected with MBLs. MATERIALS AND METHODS: A total of 116 carbapenem-resistant Gram-negative bacilli (CRGNB) were evaluated in the study. These CRGNB were tested for MBL production both phenotypically for MBLs and genotypically for blaNDM-1 gene by polymerase chain reaction (PCR). Representative stains of NDM-1 isolates were further sequenced by Triyat Scientific Co., (Nagpur, India). RESULTS: Among 116 CRGNB Citrobacter species 28 (24.13%) was the most common pathogen. Phenotypically, MHT, imipenem-EDTA (IPM-EDTA) double-disk synergy test and IPM-EDTA combined disk synergy test (CDST) detected MBL production in 105 (90.51%), 96 (81.03%), and 87 (75%) CRGNB, respectively. However, blaNDM-1 genes were detected in 66 (56.89%) isolates. The prevalence of blaNDM-1 gene was highest among Escherichia coli 26 (100%). Considering PCR as gold standard, it was observed that IMP-EDTA CDST was most specific (78.38%) while MHT was most sensitive (97.47%). Results of blaNDM-1 gene by PCR were further confirmed by sequencing (Triyat genomics, Nagpur). All the 11 representative strains were confirmed to be an NDM-1 gene. The presence of MBLs in our group of patients (non-Intensive Care Unit patients) is a cause for concern. However, on tracing their outcome, it was interesting to note that while the duration of stay lengthened in a large number of patients 112 (96.5%), mortality was relatively low 5 (4.31%). CONCLUSION: The results of this study provide insight into the prevalence of MBLs, including blaNDM-1, in a tertiary care hospital. Antibiotic stewardship implemented in all seriousness may to a great extent stave off the impending pan-drug resistance. The surprising outcome of our patients suggests either that the bacteria trade off virulence for drug resistance or the relatively robust immune response of non ICU patients fights back.
