Bonyadian Mojtaba, Moshtaghi Hamdallah, Akhavan Taheri Mariam
Department of Health and Food Quality Control, Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran;
Graduated in Veterinary Medicine, Faculty of Veterinary Medicine, Shahrekord University, Shahrekord, Iran.
Vet Res Forum. 2014 Winter;5(1):29-34.
The aim of this study was to determine the occurrence of enterotoxigenic and enteroaggregative Escherichia coli strains and antibiotic resistance of the isolates in raw milk and unpasteurized cheese. Out of 200 samples of raw milk and 50 samples of unpasteurized cheeses, 96 and 24 strains of E. coli were isolated, respectively. Polymerase chain reaction (PCR) was used to detect the genes encoding heat-stable enterotoxin a (STa), heat-stable enterotoxin b (STb), heat labile toxin (LT) and enteroaggregative heat-stable toxin1 (EAST1). Twelve out of 120 (10.00%) isolates harbored the gene for EAST1, 2(1.66%) isolates were detected as producing STb and LT toxins and 12 (10.00%) strains contained STb and EAST1 genes. None of the strains contain the STa gene. All of the strains were tested for antibiotic resistance by disk diffusion method. Disks included: ciprofloxacin (CFN), trimetoprim-sulfamethoxazole (TSX), oxytetracycline (OTC), gentamicin (GMN), cephalexin (CPN), nalidixic acid (NDA) and nitrofurantoin (NFN), ampicillin (AMP), neomycin (NEO) and streptomycin (STM). Among 120 isolated strains of E. coli, the resistance to each antibiotics were as follows: OTC100%, CPN 86.00%, NDA 56.00%, NFN 42.00%, GMN 30.00%, TSX 28.00%, CFN 20%, AM 23.40% and STM 4.25%. None of the isolates were resistant to NEO. The present data indicate that different resistant E. coli pathogens may be found in raw milk and unpasteurized cheese. It poses an infection risk for human and transferring the resistant factors to microflora of the consumers gut.
本研究的目的是确定生牛奶和未巴氏杀菌奶酪中产肠毒素和肠聚集性大肠杆菌菌株的发生率以及分离株的抗生素耐药性。在200份生牛奶样本和50份未巴氏杀菌奶酪样本中，分别分离出96株和24株大肠杆菌。采用聚合酶链反应（PCR）检测编码热稳定肠毒素a（STa）、热稳定肠毒素b（STb）、热不稳定毒素（LT）和肠聚集性热稳定毒素1（EAST1）的基因。120株分离株中有12株（10.00%）携带EAST1基因，2株（1.66%）被检测出产生STb和LT毒素，12株（10.00%）菌株含有STb和EAST1基因。所有菌株均未含有STa基因。采用纸片扩散法对所有菌株进行抗生素耐药性检测。纸片包括：环丙沙星（CFN）、甲氧苄啶-磺胺甲恶唑（TSX）、土霉素（OTC）、庆大霉素（GMN）、头孢氨苄（CPN）、萘啶酸（NDA）、呋喃妥因（NFN）、氨苄西林（AMP）、新霉素（NEO）和链霉素（STM）。在120株分离出的大肠杆菌菌株中，对每种抗生素的耐药情况如下：OTC为100%，CPN为86.00%，NDA为56.00%，NFN为42.00%，GMN为30.00%，TSX为28.00%，CFN为20%，AM为23.40%，STM为4.25%。所有分离株均对NEO不耐药。目前的数据表明，生牛奶和未巴氏杀菌奶酪中可能存在不同耐药性的大肠杆菌病原体。这对人类构成感染风险，并将耐药因子转移至消费者肠道微生物群。
