Molecular characterization and antibiotic resistance profile of ESBL-producing Escherichia coli isolated from healthy cow raw milk in smallholder dairy farms in Bangladesh

Research (Published online: 13-06-2023)

21. Molecular characterization and antibiotic resistance profile of ESBL-producing Escherichia coli isolated from healthy cow raw milk in smallholder dairy farms in Bangladesh

Azimun Nahar, A. K. M. Azharul Islam, Md. Nazimul Islam, Mohammad Kamruzzaman Khan, Md. Shahed Khan, A. K. M. Anisur Rahman, and Md. Mahbub Alam

Veterinary World, 16(6): 1333-1339

Azimun Nahar: Department of Medicine, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

A. K. M. Azharul Islam: Department of livestock services, Ministry of Fisheries and Livestock, Krishi Khamar Sarak, Farmgate, Dhaka 1215, Bangladesh.

Md. Nazimul Islam: Department of livestock services, Ministry of Fisheries and Livestock, Krishi Khamar Sarak, Farmgate, Dhaka 1215, Bangladesh.

Mohammad Kamruzzaman Khan: Department of Community Medicine, Mymensingh Medical College, Mymensingh 2206, Bangladesh.

Md. Shahed Khan: Department of Medicine, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

A. K. M. Anisur Rahman: Department of Medicine, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

Md. Mahbub Alam: Department of Medicine, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.

doi: 10.14202/vetworld.2023.1333-1339

Article history: Received: 15-03-2023, Accepted: 22-05-2023, Published online: 13-06-2023

Corresponding author: Md. Mahbub Alam

E-mail: asamahbub2003@yahoo.com

Citation: Nahar A, Islam AKMA, Islam MN, Khan MK, Khan MS, Rahman AKMA, and Alam MM (2023) Molecular characterization and antibiotic resistance profile of ESBL-producing Escherichia coli isolated from healthy cow raw milk in smallholder dairy farms in Bangladesh, Veterinary World, 16(6): 1333-1339.

Abstract

Background and Aim: The emergence of antimicrobial-resistant bacteria, such as Escherichia coli in milk, is a serious public health concern as milk is considered a complete food and an important part of daily human diet worldwide, including in Bangladesh. However, there have been no reports on the molecular characterization and antibiotic resistance profile of extended-spectrum beta-lactamase (ESBL)-producing E. coli from milk of healthy cows in Bangladesh. Therefore, this study aimed to detect and characterize ESBL-producing E. coli (ESBL-Ec) in milk samples from healthy cows in smallholder dairy farms in Mymensingh district, Bangladesh, and assess the potential risk of consuming this milk.

Materials and Methods: A total of 100 milk samples were collected from apparently healthy cows on smallholder dairy farms. Escherichia coli was isolated from the collected samples using standard methods. The detection of ESBL-Ec was performed phenotypically using cultural methods and genotypically by ESBL genetic determinants using multiplex polymerase chain reaction. Antimicrobial susceptibility testing of the ESBL-Ec isolates was performed using the disk diffusion method with 15 common antimicrobials.

Results: In this study, out of the 100 samples tested, 70 (70%) were found to be positive for E. coli. Among these, 41 (58.6%) strains were identified as ESBL-producing, both phenotypically and genotypically, with the presence of blaCTX-M, blaTEM, and blaSHV individually or combined (blaCTX-M plus blaTEM plus blaSHV). The antibiogram of these ESBL-positive isolates revealed high resistance against commonly used antibiotics, such as ampicillin, cefotaxime, and gentamicin (100%), azithromycin (88%), oxytetracycline (27%), nalidixic acid, cotrimoxazole/trimethoprim (24%), and streptomycin (22%). In addition, one isolate showed resistance to 4th generation of cephalosporin (cefepime). Most importantly, extensive multidrug resistance was found in many ESBL-Ec isolates. However, the isolates were highly sensitive to drugs such as ceftriaxone (100%) and imipenem (100%). This is the first study to detect ESBL-Ec in raw milk from healthy cows on smallholder dairy farms in Bangladesh.

Conclusion: More than 58% of the E. coli isolated from raw milk of healthy cows tested positive for ESBL production and showed resistance to most commonly used antimicrobials which may be alarming for human health. A limitation of our study is that we had a small size of sample collected from one district in Bangladesh. Therefore, a larger sample size covering a wider geographic area, and using multi-locus sequence typing and whole genome sequencing could provide a more comprehensive understanding of the prevalence and characteristics of ESBL-Ec in Bangladesh.

Keywords: ampicillin, antibiogram, blaCTX-M, cefotaxime, multiplex PCR, multidrug resistance.