Abstract
BackgroundMultidrug-resistant (MDR) Gram-negative bacterial species are an increasingly dangerous public health threat, and are now endemic in many areas of South Asia. However, there are a lack of comprehensive data from many countries in this region determining historic and current MDR prevalence. Enterotoxigenic Escherichia coli (ETEC) is a leading cause of both acute infant diarrhea and traveler’s diarrhea in Nepal. The MDR prevalence and associated resistance mechanisms of ETEC isolates responsible for enteric infections in Nepal are largely unknown.MethodsA total of 265 ETEC isolates were obtained from acute diarrheal samples (263/265) or patient control samples (2/265) at traveler’s clinics or regional hospitals in Nepal from 2001 to 2016. Isolates were screened for antibiotic resistance, to include extended spectrum beta-lactamase (ESBL) production, via the Microscan Automated Microbiology System. ETEC virulence factors, specifically enterotoxins and colonization factors (CFs), were detected using multiplex PCR, and prevalence in the total isolate population was compared to ESBL-positive isolates. ESBL-positive isolates were assessed using multiplex PCR for genetic markers potentially responsible for observed resistance.ResultsA total of 118/265 (44.5%) ETEC isolates demonstrated resistance to ≥2 antibiotics. ESBL-positive phenotypes were detected in 40/265 isolates, with isolates from 2008, 2013, 2014, and 2016 demonstrating ESBL prevalence rates of 1.5, 34.5, 31.2, and 35.0% respectively. No difference was observed in overall enterotoxin characterization between the total ETEC and ESBL-positive populations. The CFs CS2 (13.6%), CS3 (25.3%), CS6 (30.2%), and CS21 (62.6%) were the most prevalent in the total ETEC population. The ESBL-positive ETEC isolates exhibited a higher association trend with the CFs CS2 (37.5%), CS3 (35%), CS6 (42.5%), and CS21 (67.5%). The primary ESBL gene identified was blaCTX-M-15 (80%), followed by blaSHV-12 (20%) and blaCTX-M-14 (2.5%). The beta-lactamase genes blaTEM-1 (40%) and blaCMY-2 (2.5%) were also identified. It was determined that 42.5% of the ESBL-positive isolates carried multiple resistance genes.ConclusionOver 30% of ETEC isolates collected post-2013 and evaluated in this study demonstrated ESBL resistance. Persistent surveillance and characterization of enteric ETEC isolates are vital for tracking the community presence of MDR bacterial species in order to recommend effective treatment strategies and help mitigate the spread of resistant pathogens.
Highlights
Multidrug-resistant (MDR) Gram-negative bacterial species are an increasingly dangerous public health threat, and are endemic in many areas of South Asia
extended spectrum beta-lactamase (ESBL)-production in all positive Enterotoxigenic Escherichia coli (ETEC) isolates was confirmed through a disk diffusion test
Of the ESBL-positive ETEC isolates, the majority were recovered from acute diarrheal samples (39/40, 97.5%), 1/40 (2.5%) was recovered from a patient control sample
Summary
Multidrug-resistant (MDR) Gram-negative bacterial species are an increasingly dangerous public health threat, and are endemic in many areas of South Asia. A lack of comprehensive surveillance programs may result in the unchecked spread of MDR Gram-negative bacterial species and their associated resistance mechanisms. Developing countries with an established national surveillance network, such as Nepal, do not have the resources to perform in-depth isolate characterization to comprehensively identify resistance mechanisms carried by MDR bacterial isolates [5,6,7]. After the establishment of intestinal colonization, the bacterial cells produce heat-labile enterotoxins (LT) and/or heat-stable enterotoxins (STh or STp) that target vital cellular processes [8, 17, 18] The production of these enterotoxins most commonly results in abdominal cramping and watery diarrhea, with more severe cases presenting with fever and nausea. ETEC virulence factors, such as enterotoxins and CFs, are potential targets for vaccines or therapeutic candidates, and determination of regional prevalence rates and specific virulence factors may serve to inform the development of globally effective vaccines [15, 18,19,20,21]
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