Abstract
This study was undertaken to evaluate the prevalence of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae in selected shrimp aquaculture farms (n = 37) in Kerala, South India and to characterize the isolates using molecular tools. Overall, a low prevalence of ESBL-producers was found in the farms, most likely due to the reduced antibiotic usage in the shrimp farming sector. Out of the 261 samples (77 shrimp and 92 each of water and sediment), 14 (5.4%) tested positive for ESBL-E. coli or ESBL-K. pneumoniae. A total of 32 ESBL-E. coli and 15 ESBL- K. pneumoniae were recovered from these samples. All ESBL isolates were cefotaxime-resistant with minimal inhibitory concentration (MIC) ≥32 μg/ml. Of all isolates, 9 (28.1%) E. coli and 13 (86.7%) K. pneumoniae showed simultaneous resistance to tetracycline, ciprofloxacin, and trimethoprim-sulfamethoxazole. PCR analysis identified CTX-M group 1 (blaCTX–M–15) as the predominant ESBL genotype in both E. coli (23, 71.9%) and K. pneumoniae (15, 100%). Other beta-lactamase genes detected were as follows: blaTEM and blaSHV (11 K. pneumoniae), blaCTX–M group 9 (9 E. coli), and blaCMY–2 (2 E. coli). Further screening for AMR genes identified tetA and tetB (13, 40.6%), sul1 (11, 34.4%), sul2 (9, 28.1%), catA and cmlA (11, 34.4%), qepA and aac(6′)-Ib-cr (9, 28.1%) and strAB and aadA1 (2, 6.3%) in E. coli, and qnrB (13, 86.7%), qnrS (3, 20%), oqxB (13, 86.7%), tetA (13, 86.7%), and sul2 (13, 86.7%) in K. pneumoniae isolates. Phylogenetic groups identified among E. coli isolates included B1 (4, 12.5%), B2 (6, 18.8%), C (10, 31.3%), D (3, 9.4%), and E (9, 28.1%). PCR-based replicon typing (PBRT) showed the predominance of IncFIA and IncFIB plasmids in E. coli; however, in K. pneumoniae, the major replicon type detected was IncHI1. Invariably, all isolates of K. pneumoniae harbored virulence-associated genes viz., iutA, entB, and mrkD. Epidemiological typing by pulsed-field gel electrophoresis (PFGE) revealed that E. coli isolates recovered from different farms were genetically unrelated, whereas isolates of K. pneumoniae showed considerable genetic relatedness. In conclusion, our findings provide evidence that shrimp aquaculture environments can act as reservoirs of multi-drug resistant E. coli and K. pneumoniae.
Highlights
Antimicrobial resistance (AMR) is undoubtedly a huge public health crisis across the globe
Infections caused by white spot syndrome virus (WSSV), a microsporidian parasite namely Enterocytozoon Hepatopenaei (EHP), and Vibrio bacteria were the most common
It is noteworthy that natural remedies such as garlic paste and jaggery were cited by many farmers as supporting the health of their stock
Summary
Antimicrobial resistance (AMR) is undoubtedly a huge public health crisis across the globe. AMR had long been regarded as an issue of human health alone, but recent years have witnessed a growing recognition of the imprudent use of antibiotics in multiple sectors (agriculture, food animals, aquaculture, and environment) as important drivers of resistance. India was the top exporter of farmed shrimps in 2018 with the United States, Vietnam, and EU countries as the leading markets for Indian shrimps (FAO, 2019). This sector faces many challenges, the most important being the high disease burden caused by various viruses, bacteria, fungi, and parasites. The decision to use antibiotics in farms is often influenced by the advice given by neighboring farmers, drug suppliers, feed companies, private veterinarians and others
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