Ntuli V, Njage P M K, Buys E M
Department of Food Science, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa.
Department of Food Science, University of Pretoria, Private Bag X20, Hatfield, Pretoria 0028, South Africa.
J Dairy Sci. 2016 Dec;99(12):9534-9549. doi: 10.3168/jds.2016-11403. Epub 2016 Oct 5.
The current study was undertaken to characterize Escherichia coli and other Enterobacteriaceae in raw and pasteurized producer-distributor bulk milk (PDBM). A total of 258 samples were collected from purchase points in 8 provinces in South Africa. The samples were tested for antibiotic residues, phosphatase, total aerobic bacteria, coliforms, and E. coli counts. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used for identification of isolates. Escherichia coli isolates were characterized for virulence factors, antimicrobial resistance, serotypes, and presumptive E. coli O157:H7. Antibiotic residues and alkaline phosphatase were detected in 2% of both raw and pasteurized PDBM (n=258) and 21% pasteurized PDBM (n=104) samples, respectively. A total of 729 isolates belonging to 21 genera and 59 species were identified. Escherichia coli, Enterobacter cloacae, Klebsiella oxytoca, and Raoultella ornithinolytica were the most abundant species. Spoilage Enterobacteriaceae species exceeded 50% of the total isolates. Escherichia coli was detected and isolated from 36% of the milk samples. Thirty-one E. coli isolates harbored virulence genes stx1/stx2 and 38% (n=121) were presumptive O157:H7. The prevalence of samples with presumptive shigatoxin producing E. coli was 10%. Antimicrobial-resistant E. coli isolates were detected in 70% of the milk samples with 36% of stx1/stx2 positive E. coli showing multi-drug resistance. Information obtained from the study will be used for modeling the public health risk posed by milkborne pathogens in PDBM, which in many cases is consumed by poor and vulnerable members of the population.
本研究旨在对生鲜和巴氏杀菌的生产商-经销商散装牛奶（PDBM）中的大肠杆菌及其他肠杆菌科细菌进行特性分析。从南非8个省份的采购点共采集了258份样本。对这些样本进行了抗生素残留、磷酸酶、需氧菌总数、大肠菌群和大肠杆菌计数检测。采用基质辅助激光解吸/电离飞行时间质谱法对分离株进行鉴定。对大肠杆菌分离株的毒力因子、抗菌药物耐药性、血清型以及推定的大肠杆菌O157:H7进行了特性分析。生鲜和巴氏杀菌PDBM（n = 258）样本中分别有2%检测出抗生素残留和碱性磷酸酶，巴氏杀菌PDBM（n = 104）样本中有21%检测出碱性磷酸酶。共鉴定出729株分离株，分属于21个属和59个种。大肠杆菌、阴沟肠杆菌、产酸克雷伯菌和解鸟氨酸拉乌尔菌是最常见的菌种。腐败性肠杆菌科菌种超过分离株总数的50%。从36%的牛奶样本中检测到并分离出了大肠杆菌。31株大肠杆菌分离株携带stx1/stx2毒力基因，38%（n = 121）为推定的O157:H7。推定产志贺毒素大肠杆菌样本的患病率为10%。在70%的牛奶样本中检测到了耐抗菌药物的大肠杆菌分离株，其中36%的stx1/stx2阳性大肠杆菌表现出多重耐药性。本研究获得的信息将用于模拟PDBM中食源性病原菌所带来的公共卫生风险，在许多情况下，PDBM是贫困和弱势群体所消费的。
