Extended Spectrum Β-Lactamase and Metallo Β -Lactamase Producing Multidrug Resistant Gram Negative Bacteria among Patients with Renal Failure

Abstract

Patients with renal failure are at greater risk of infection because of the abnormality in their immune system and the direct exposure of circulatory system to the microorganisms. The infection in such vulnerable population by drug resistant bacteria may lead to life-threatening consequences. The purpose of this study was to isolate and identify the multiple drug resistant Gram negative bacteria (MDRGNB) from kidney patients and hemodialysis patients and to screen those producing Extended-Spectrum β-Lactamases (ESBLs) and Metallo β-Lactamases (MBLs). During the study period (March-August, 2013), 496 samples of urine and 21 samples of blood collected from patients visiting and undergoing hemodialysis at National Kidney Centre (NKC) were processed. The isolates were identified by standard microbiological procdeures and subjected to antimicrobial susceptibility testing by modified Kirby Bauer disc diffusion methods. Production of ESBL and MBL was determined using MASTDISCSTM ID ESBL detection discs and imipenem EDTA combined disc assay respectively. The Minimum Inhibitory Concentration (MIC) of ciprofloxacin against the MDR isolates was also determined using agar dilution method.

Total 103 (19.92%) samples showed significant growth and 85.43% of them were multidrug resistant. The higher rate of growth among female patients was found statistically significant (p<0.05). Imipenem was found to be most effective drug against the isolates whereas ceftazidime, with sensitivity and positive predictive value of 94.2% and 76.7% respectively was found to be more effective in screening ESBL producers among MDR strains than cefotaxime. Of the 59 MDR isolates suspected 35 (66.66%) were confirmed to produce ESBL with at least one Combined Disc (CD) assay used. Ceftazidime-clavulanate combined disc correctly identified all of the ESBL isolates whereas cefotaxime failed to confirm two isolates. Only one of the 11 isolates tested for MBL production was confirmed to produce MBL. The majority of ESBL isolates were Escherichia coli 29 (82.85%), whereas 2/2 (100%) of suspected Pseudomonas aeruginosa isolates were ESBL. None of the Proteus vulgaris were found to produce ESBL. Of note was the co-existence of ESBL and MBL in Pseudomonas aeruginosa. However, the production of MBL and resistance to carbapenems was statistically insignificant (p>0.05). The statistical pattern of resistance of ciprofloxacin, norfloxacin, ceftazidime and cefotaxime and ESBL production was found significant (p<0.05). Most of the isolates showed MIC value of 8µg/ml towards ciprofloxacin.

Use of single screening agent for ESBL screening may result in false positive results, hence use of more than one of the screening agents and combined disk assay improves the sensitivity of detection of ESBL.