Shahid Ahmad Abbasi

Prevalence of faecal carriage of Enterobacteriaceae with NDM-1 carbapenemase at military hospitals in Pakistan, and evaluation of two chromogenic media

OBJECTIVES To determine the prevalence and antimicrobial susceptibility of carbapenemase-producing Enterobacteriaceae among hospitalized patients and outpatients attending two military hospitals in Rawalpindi, Pakistan, and to compare the performance of two chromogenic culture media for the isolation of these organisms. METHODS Stool samples from 200 distinct patients were cultured on MacConkey agar and subsequently on two chromogenic media-Colorex KPC and a prototype chromogenic medium, ID Carba-designed for the isolation of carbapenemase-producing Enterobacteriaceae. All Gram-negative isolates growing on either chromogenic medium were investigated for carbapenemases by phenotypic and molecular methods. Producers were subjected to susceptibility testing with 40 antimicrobials by VITEK 2 or agar dilution. RESULTS In total, 64 NDM-1-positive isolates of Enterobacteriaceae, belonging to seven distinct species, were recovered from 37 (18.5%) of the stool samples. No other carbapenemase types were confirmed. Nineteen positive samples were identified among 70 from inpatients (prevalence 27.1%) and there were 18 positive samples among 130 from outpatients (prevalence 13.8%). Fifty-six isolates (87.5%) harbouring the NDM-1 enzyme were recovered on ID Carba compared with 41 isolates (64.1%) on Colorex KPC (P = 0.012). Multidrug resistance was prevalent, but no pan-resistant isolates were found, with most isolates susceptible in vitro to colistin (97%), mecillinam (95%), fosfomycin (94%), tigecycline (89%) and nitrofurantoin (78%). CONCLUSIONS This study shows a high prevalence of multidrug-resistant Enterobacteriaceae with the NDM-1 enzyme in Rawalpindi. The new chromogenic medium, ID Carba, was more sensitive than Colorex KPC and has potential as a screening medium for isolation of Enterobacteriaceae harbouring the NDM-1 enzyme.

Molecular Epidemiology of NDM-1-Producing Enterobacteriaceae and Acinetobacter baumannii Isolates from Pakistan

ABSTRACT The molecular epidemiology of 66 NDM-producing isolates from 2 Pakistani hospitals was investigated, with their genetic relatedness determined using repetitive sequence-based PCR (Rep-PCR). PCR-based replicon typing and screening for antibiotic resistance genes encoding carbapenemases, other β-lactamases, and 16S methylases were also performed. Rep-PCR suggested a clonal spread of Enterobacter cloacae and Escherichia coli. A number of plasmid replicon types were identified, with the incompatibility A/C group (IncA/C) being the most common (78%). 16S methylase-encoding genes were coharbored in 81% of NDM-producing Enterobacteriaceae.

In Vitro Efficacy of Cefepime Against Multi-Drug Resistant Pseudomonas aeruginosa – An Alarming Situation in our Setup

Background: Third generation cephalosporins are still most commonly used antibiotics empirically in our setup leading to emergence of resistance in this group. In this environment of increasing resistance, empirical use of this group of antibiotics would be a futile effort. Therefore, this study was conducted to evaluate the in vitro efficacy of fourth generation cephalosporin cefepime against multi-drug resistant isolates of Pseudomonas aeruginosa from various clinical specimens in our setup.

Reverse line probe assay for cheap detection of Single Nucleotide Polymorphisms in Mycobacterium tuberculosis

More and more Single Nucleotide Polymosrphisms of interest among pathogenic organisms are described with the advent of Whole Genome Sequencing but WGS approach is still too expensive, time consuming, and relying on bioinformatical means that are not available in many developing countries. This study presents a low-cost reverse hybridization line probe technique for detecting SNPs in Mycobacterium tuberculosis. The proposed test is able to detect mutations in the RRDR of rpoB gene in M. tuberculosis with specificity and sensitivity of 98% and 100%, respectively and for an average cost of less than €3 per sample. The technique proved efficient not only on pure DNA samples extracted from culture isolates but also on crude extracts from clinical samples. The flexibility of the platform allows to get it transformed to any kind of test detection, hence, building a bridge between rich countries performing SNP discovery and countries with high burden that can target these SNPs on the collected samples.

Pattern of Bacterial Pathogens and Their Antimicrobial Susceptibility from Blood Culture Specimens in a Tertiary Care Setting

The objective of this paper is to find out the pattern of bacterial pathogens and their antimicrobial susceptibility from blood culture specimens received from a tertiary care referral setting. This cross-sectional observational study was carried out at the Department of Microbiology, Armed Forces Institute of Pathology, from July 2011 through June 2012. Blood culture specimens were dealt with brain heart infusion broth based manual method and automated BACTEC system. The specimens yielding positive growth were further analyzed and antimicrobial susceptibility carried out as per CLSI recommendations. Out of 2921 blood culture specimens, 465 (16%) yielded growth. Out of these, 245 (53%) isolates were Gram positive, 209 (45%) Gram negatives while 11 (2%) were yeast. Among Gram positive isolates, 208 (85%) were Staphylococcus spp. and among these 158 (76%) were methicillin resistant. Amongst Gram negative group, 115 (55%) isolates were members of enterobacteriaceae family and E. coli was the leading pathogen, while 94 (45%) were non-fermenters (NF). Among these, Acinetobacter spp. and Pseudomonas aeruginosa were common pathogens. In vitro antimicrobial susceptibility of staphylococci revealed that 100% isolates were susceptible to vancomycin and linezolid. The organisms of family enterobacteriaceae revealed better susceptibility to amikacin (68.7%) and imipenem (64.3%). The NF group showed better in vitro susceptibility to tazobactam/piperacillin (65%). Gram positive organisms were predominantly causing blood stream infections. Vancomycin and linezolid in case of Gram positive and amikacin and tazobactam/piperacillin against Gram negative organisms revealed better in vitro efficacy.