Nahar Azimun, Islam A K M Azharul, Islam Md Nazimul, Khan Mohammad Kamruzzaman, Khan Md Shahed, Rahman A K M Anisur, Alam Md Mahbub
Department of Medicine, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
Department of livestock services, Ministry of Fisheries and Livestock, Krishi Khamar Sarak, Farmgate, Dhaka 1215, Bangladesh.
Vet World. 2023 Jun;16(6):1333-1339. doi: 10.14202/vetworld.2023.1333-1339. Epub 2023 Jun 13.
The emergence of antimicrobial-resistant bacteria, such as 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 from milk of healthy cows in Bangladesh. Therefore, this study aimed to detect and characterize ESBL-producing (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.
A total of 100 milk samples were collected from apparently healthy cows on smallholder dairy farms. 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.
In this study, out of the 100 samples tested, 70 (70%) were found to be positive for . Among these, 41 (58.6%) strains were identified as ESBL-producing, both phenotypically and genotypically, with the presence of CTX-M, TEM, and SHV individually or combined (CTX-M plus TEM plus SHV). 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 4 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.
More than 58% of the 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.
抗菌药物耐药性细菌的出现，比如牛奶中的此类细菌，是一个严重的公共卫生问题，因为牛奶被视为一种完整的食物，并且是全球人类日常饮食的重要组成部分，在孟加拉国亦是如此。然而，关于孟加拉国健康奶牛所产牛奶中产生超广谱β-内酰胺酶（ESBL）的大肠杆菌的分子特征及抗生素耐药谱，尚无相关报道。因此，本研究旨在检测并鉴定孟加拉国迈门辛希区小农户奶牛场健康奶牛牛奶样本中产生ESBL的大肠杆菌（ESBL-Ec），并评估饮用此类牛奶的潜在风险。
从小农户奶牛场明显健康的奶牛身上共采集了100份牛奶样本。使用标准方法从采集的样本中分离出大肠杆菌。采用培养方法对ESBL-Ec进行表型检测，通过多重聚合酶链反应利用ESBL基因决定簇进行基因型检测。采用纸片扩散法，使用15种常用抗菌药物对ESBL-Ec分离株进行药敏试验。
在本研究中，在所检测的100个样本中，70个（70%）被发现大肠杆菌呈阳性。其中，41个（58.6%）菌株在表型和基因型上均被鉴定为产生ESBL，分别或联合存在CTX-M、TEM和SHV（CTX-M加TEM加SHV）。这些ESBL阳性分离株的抗菌谱显示，它们对常用抗生素具有高度耐药性，如氨苄西林、头孢噻肟和庆大霉素（100%）、阿奇霉素（88%）、土霉素（27%）、萘啶酸、复方新诺明/甲氧苄啶（24%）和链霉素（22%）。此外，一株分离株对第四代头孢菌素（头孢吡肟）耐药。最重要的是，在许多ESBL-Ec分离株中发现了广泛的多重耐药性。然而，这些分离株对头孢曲松（100%）和亚胺培南（100%）等药物高度敏感。这是首次在孟加拉国小农户奶牛场健康奶牛的生牛奶中检测到ESBL-Ec的研究。
从健康奶牛生牛奶中分离出的大肠杆菌中，超过58%检测出产生ESBL呈阳性，并对大多数常用抗菌药物耐药，这可能对人类健康构成警示。我们研究的一个局限性在于，我们从孟加拉国的一个地区采集的样本量较小。因此，扩大样本量、覆盖更广泛的地理区域，并采用多位点序列分型和全基因组测序，可能会更全面地了解孟加拉国ESBL-Ec的流行情况和特征。
