A survey of foodborne pathogens in bulk tank milk and raw milk consumption among farm families in pennsylvania

A 2-part study was conducted to determine the risk of exposure to human pathogens from raw milk. The first part of the study focused on determining raw milk consumption habits of dairy producers. A total of 248 dairy producers from 16 counties in Pennsylvania were surveyed. Overall, 105 (42.3%) of the 248 dairy producers consumed raw milk and 170 (68.5%) of the 248 dairy producers were aware of foodborne pathogens in raw milk. Dairy producers who were not aware of foodborne pathogens in raw milk were 2-fold more likely to consume raw milk compared with dairy producers who were aware of foodborne pathogens. The majority of dairy producers who consumed raw milk indicated that taste (72%) and convenience (60%) were the primary factors for consuming raw milk. Dairy producers who resided on the dairy farm were nearly 3-fold more likely to consume raw milk compared with those who lived elsewhere. In the second part of the study, bulk tank milk from the 248 participating dairy herds was examined for foodborne pathogens. Campylobacter jejuni (2%), Shiga toxin-producing Escherichia coli (2.4%), Listeria monocytogenes (2.8%), Salmonella (6%), and Yersinia enterocolitica (1.2%) were detected in the milk samples. Salmonella isolates were identified as S. enterica serotype Typhimurium (n = 10) and S. enterica serotype Newport (n = 5). Of the 248 bulk tank milk samples, 32 (13%) contained ≥1 species of bacterial pathogens. The findings of the study could assist in developing farm community-based educational programs on the risks of consuming raw milk.     

实时荧光定量PCR技术在食源性致病菌检测中的应用

实时荧光定量PCR技术作为一种高效的微生物定量检测法,在食品工业中具有广泛的应用前景。本文综述了实时荧光定量PCR技术检测原理,及其在食源性致病菌如金黄色葡萄球菌、大肠杆菌O157∶H7、沙门氏菌和副溶血性弧菌检测中的应用。     

Prevalence,molecular characterization,and antimicrobial resistance profiles of Listeria monocytogenes,Salmonella enterica,and Escherichia coli O157:H7 on dairy cattle farms in Jordan

This study determined the prevalence, pulsed-field gel electrophoresis profiles, and antimicrobial resistance profile of Listeria monocytogenes, Salmonella enterica, and Escherichia coli O157:H7 isolates from dairy cattle farms in Jordan. Samples from bulk tank milk (n = 305), cattle feces (n = 610), and rectoanal mucosal swabs (n = 610) were collected from 61 dairy cattle farms. We confirmed 32 L. monocytogenes, 28 S. enterica, and 24 E. coli O157:H7 isolates from the samples. The farm-level prevalence (at least 1 positive sample per farm) of L. monocytogenes, S. enterica, and E. coli O157:H7 was 27.9, 19.7, and 23.0%, respectively. The prevalence of L. monocytogenes, S. enterica, and E. coli O157:H7 in bulk tank milk was 7.5, 1.6, and 3.3%, respectively. The prevalence of L. monocytogenes and S. enterica in fecal samples was 1.5 and 3.8%, respectively, and the prevalence of E. coli O157:H7 in rectoanal mucosal swabs was 2.3%. Based on disk diffusion testing, all L. monocytogenes, S. enterica, and E. coli O157:H7 isolates exhibited resistance to at least 1 antimicrobial class. Multidrug resistance (resistance to 3 or more classes of antimicrobials) was exhibited by 96.9% of L. monocytogenes, 91.7% of E. coli O157:H7, and 82.1% of S. enterica isolates. Moreover, 93.8, 79.2, and 57.1% of the L. monocytogenes, E. coli O157:H7, and S. enterica isolates, respectively, were resistant to 5 or more antimicrobial classes. More than 50% of L. monocytogenes isolates were resistant to ampicillin, clindamycin, penicillin, erythromycin, quinupristin–dalfopristin, streptomycin, teicoplanin, linezolid, vancomycin, kanamycin, and tetracycline. More than 50% of S. enterica and E. coli O157:H7 isolates were resistant to ampicillin, cephalothin, nalidixic acid, kanamycin, streptomycin, amoxicillin–clavulanic acid, and tetracycline. The prevalence of the studied pathogens this study was comparable to reports from other countries. The isolated pathogens exhibited a high degree of antimicrobial resistance, suggesting that the bacterial flora of dairy cattle in Jordan are under intense antimicrobial selection pressure. Additional research is required to determine the causes and drivers of resistance, and to develop approaches to mitigating antimicrobial resistance.     

Antimicrobial activity of nisin, reuterin, and the lactoperoxidase system on Listeria monocytogenes and Staphylococcus aureus in cuajada, a semisolid dairy product manufactured in Spain

The inhibitory activity of nisin (N), reuterin (R), and the lactoperoxidase system (LPS), added individually or in combination, against Listeria monocytogenes and Staphylococcus aureus was investigated in “cuajada” (curdled milk), a semisolid dairy product manufactured in Spain. Cuajada was manufactured from UHT skim milk separately inoculated with L. monocytogenes and Staph. aureus, each at approximately 4 log cfu/mL, and held under conditions of temperature abuse (10°C). On d 3, a synergistic bactericidal activity was observed for the combinations of biopreservatives assayed, with L. monocytogenes counts of only 0.30 log cfu/mL in cuajada made with N + R + LPS vs. 8.31 log cfu/mL in control cuajada. After 12 d, L. monocytogenes could not be detected in cuajada made with added N + LPS or N + R + LPS. Staphylococcus aureus was more resistant than L. monocytogenes to biopreservatives added individually. On d 3, the synergistic effect of the 3 biopreservatives against Staph. aureus resulted in counts of 3.03 log cfu/mL in cuajada made with N + R + LPS vs. 6.40 in control cuajada. After 12 d, Staph. aureus counts were 2.61 log cfu/mL in cuajada made with N + R + LPS, whereas they ranged from 6.11 to 7.70 log cfu/mL in control cuajada and in cuajada made with other combinations of biopreservatives. The most pronounced decrease in pathogen counts was achieved by the triple combination N + R + LPS, which acted synergistically on the inactivation of L. monocytogenes and Staph. aureus in cuajada over 12 d at 10°C. The treatment combining these 3 natural biopreservatives at low concentrations, within the hurdle concept of food preservation, might be a useful tool to control the growth of pathogenic microorganisms in nonacidified dairy products.     

Caliciviruses: A Major Cause of Foodborne Illness

ABSTRACT: The public health impact of infections by human caliciviruses (HuCVs) is increasingly being recognized. The Norwalk-like viruses (NLV) are the most common cause of outbreaks of nonbacterial gastroenteritis and the most recognized foodborne viral etiologic agents. Factors that contribute to their high burden of infection are low infectious dose, stability in the environment, the diversity of strains, and the lack of long-term immunity to infection or illness. The recent development of sensitive molecular techniques for diagnosis, quantification, and characterization of these agents has led to the recognition of the importance of NLV infection. Future applications of these approaches to understanding modes of transmission and the effectiveness of control measures holds promise for improved understanding of the epidemiology of HuCVs, as well as important control measures for foodborne transmission. This report reviews what is currently known and understood about human caliciviruses regarding foodborne transmission.     

食源性致病细菌检测技术研究进展

对几种常见的食源性致病细菌检测技术进行了综述,对以聚合酶链式反应(PCR)方法为基础的检测技术进行了分析,将PCR检测食源性致病菌所需要用到的靶基因及其引物等进行了归纳,并对食源性致病菌检测技术的发展提出了建议。     

多重PCR同时检测食品中4 种细菌与常见霉菌

建立一种同时检测食品中金黄色葡萄球菌、单核细胞增生李斯特氏菌、沙门氏菌、大肠杆菌O157:H7以及霉菌的多重聚合酶链式反应（polymerase chain reaction,PCR）检测方法。根据金黄色葡萄球菌的耐热核酸酶基因（nuc）、沙门氏菌的侵袭正调节蛋白基因（hilA）、大肠杆菌O157:H7鞭毛基因（flic）、单核细胞增生李斯特氏菌的毒力调控蛋白基因（prfA）及霉菌18S?rRNA基因V5区分别设计5?对特异性引物,并对PCR扩增反应体系和扩增条件进行优化,确定获得特异性良好的PCR扩增产物。而后在37?℃对人工污染致病菌的香肠、面包和豆腐进行增菌培养,5?种致病微生物在20?h内的检出限均可达到100?CFU/25?g。本实验建立的多重PCR检测方法适用于食品中4?种细菌与常见霉菌的同时检测,相较于传统检测方法,具有快速、简便、特异性高的优点。     

2015年分离自中国大陆食品的1 070株沙门菌耐药性分析

目的 了解我国2015年食源性沙门菌的耐药状况及mcr-1基因在硫酸粘菌素(conlistin,CT)耐药菌株中的分布情况。方法 采用微量肉汤稀释法测定1 070株食源性沙门菌对10类16种抗生素的药物敏感性,采用荧光定量聚合酶链式反应(PCR)方法检测196株CT耐药菌株中是否存在mcr-1基因。结果 71.9%(769/1 070)的沙门菌对受试的16种抗生素呈现不同程度的耐药性,其中萘啶酸(NAL)、四环素(TET)、氨苄西林(AMP)、氨苄西林/舒巴坦(SAM)4种抗生素的耐药率较高,均在40%以上,未见碳青霉烯类耐药菌株,47.5%(508/1 070)的沙门菌同时耐受3类或3类以上抗生素,表现为多重耐药,同时耐受抗生素种类最高为9类。共存在141种耐药谱,优势耐药谱型为NAL、AMP-SAM-NAL-CT和TET。196株CT耐药沙门菌检出1株携带mcr-1基因且超广谱β-内酰胺酶(ESBLs)阳性的菌株,该菌株为伦敦血清型,是所有测试菌株中唯一1株九重耐药株。部分省份沙门菌耐药率较高。生禽肉和生畜肉来源沙门菌耐药率较高,分别为80.6%(349/433)和73.5%(283/385)。结论 我国2015年食源性沙门菌整体耐药水平较高,且多重耐药情况严重,生禽畜肉是耐药沙门菌的主要来源,我国食源性沙门菌中存在携带mcr-1基因的严重耐药菌株,应引起关注。     

南京市某食品厂酱卤熟肉制品生产加工过程微生物污染状况分析

目的了解南京市某食品厂酱卤熟肉制品加工过程中微生物污染状况及分布情况。方法 2016—2017年在南京市某食品厂采集生产加工过程中食品样品120份(原辅料60份、中间产品28份、成品24份、终产品8份)、环境样品204份、空气样品58份和生产用水14份,共396份,按照GB 4789食品微生物学检验系列标准和GB/T 16294—2010《医药工业洁净室(区)沉降菌的测试方法》对卫生指示菌和主要食源性致病菌进行检测,并对沙门菌进行血清型鉴定。结果在食品样品和环境样品中,李斯特菌检出率为7.4%(24/324),金黄色葡萄球菌检出率为2.6%(5/196),沙门菌检出率为1.9%(6/324);其中李斯特菌有2株单核细胞增生李斯特菌,其他以格氏李斯特菌和伊氏李斯特菌为主;沙门菌经血清学分型共4种血清型,分别为肠炎沙门菌(2株)、鼠伤寒沙门菌(2株)、依桑吉沙门菌(1株)和亚利桑那沙门菌(1株)。在原辅料、中间产品以及人员、仪器设备、清洁工具中均有致病菌检出,但成品和终产品中未检出致病菌。结论酱卤熟肉制品生产过程原辅料和环境中均存在多种致病菌污染。     

多重PCR技术在食源性致病菌检测中应用的研究进展

食源性致病菌的多重PCR检测技术是指能够同时扩增得到同种或多种致病菌的不同基因片段的技术。因该技术特异、灵敏且分析效率高,现已被广泛应用于食源性致病菌的检测工作中。本文介绍了多重PCR在食源性致病菌检测中应用的研究近况,并对影响因素及存在的问题进行了阐述。