Nayak Deepti N, Savalia C V, Kalyani I H, Kumar Rajeev, Kshirsagar D P
Department of Veterinary Public Health and Epidemiology, Vanbandhu College of Veterinary Science and Animal Husbandry, Navsari Agricultural University, Navsari - 396 450, Gujarat, India.
Department of Veterinary Microbiology, Vanbandhu College of Veterinary Science and Animal Husbandry, Navsari Agricultural University, Navsari - 396 450, Gujarat, India.
Vet World. 2015 Jun;8(6):695-701. doi: 10.14202/vetworld.2015.695-701. Epub 2015 Jun 6.
The present study was undertaken with the prime objective of isolating and identifying Listeria spp. from various foods of animal origin sold at retail market outlets in the city of Navsari, Gujarat.
Total 200 samples comprising of milk, milk products, meat, and fish (50 each) collected aseptically from local market which were subjected first to pre-enrichment in half strength Fraser broth followed by enrichment in full strength Fraser broth and subsequent plating on PALCAM agar. The growth with the typical colony characteristics were further identified up to species level on the basis of their morphological and biochemical characteristics. Cultures identified as Listeria monocytogenes were further subjected to in vitro pathogenicity tests and detection of different virulence-associated genes viz. actA, hlyA, and iap using polymerase chain reaction.
Of the total 200 food samples of animal origin; 18 (9%) were found positive for Listeria spp. which were identified as Listeria seeligeri (6, 33.3%), Listeria innocua (5, 27.7%), Listeria welshimeri (4, 22.2%), and L. monocytogenes (3, 16.6%). The highest prevalence was observed in milk samples (8). Species wise, 6 isolates of L. seeligeri which included two each from cow milk, buffalo milk, and meat samples; 5 L. innocua isolates included four recovered from fish and one from meat sample; 4 L. welshimeri comprised of two isolates from ice cream and one each from buffalo milk and meat sample; and 3 isolates of L. monocytogenes recovered from milk (1 cow and 2 buffalo milk). All 3 L. monocytogenes isolates screened for the presence of virulence genes viz. actA, hlyA, and iap using the specific primers revealed the presence of all the genes suggesting the possibility of danger of foodborne listeriosis among raw milk consumers.
Listeria spp. was isolated from 9% (18/200) of the animal origin food samples viz.; milk, milk products, meat, and fish with the highest prevalence in the milk samples. L. monocytogenes was isolated from 3 milk samples only. L. seeligeri was the predominant species isolated followed by L. innocua, L. welshimeri, and L. monocytogenes in this study. L. monocytogenes were found to carry virulence genes like actA, hly A, and iap genes suggesting the pathogenic potential of these isolates.
本研究的主要目的是从古吉拉特邦纳夫萨里市零售市场销售的各种动物源性食品中分离和鉴定李斯特菌属。
从当地市场无菌采集200份样本，包括牛奶、奶制品、肉类和鱼类（各50份），首先在半强度弗雷泽肉汤中进行预富集，然后在全强度弗雷泽肉汤中富集，随后接种于PALCAM琼脂平板上。根据其形态和生化特征，将具有典型菌落特征的生长物进一步鉴定到种水平。对鉴定为产单核细胞李斯特菌的培养物进一步进行体外致病性试验，并使用聚合酶链反应检测不同的毒力相关基因，即actA、hlyA和iap。
在总共200份动物源性食品样本中，18份（9%）被发现李斯特菌属呈阳性，鉴定为斯氏李斯特菌（6份，33.3%）、无害李斯特菌（5份，27.7%）、威氏李斯特菌（4份，22.2%）和产单核细胞李斯特菌（3份，16.6%）。牛奶样本中的患病率最高（8份）。按菌种分类，6株斯氏李斯特菌中，分别有2株来自牛奶、水牛奶和肉类样本；5株无害李斯特菌中，4株从鱼类中分离得到，1株从肉类样本中分离得到；4株威氏李斯特菌中，2株从冰淇淋中分离得到，1株分别从水牛奶和肉类样本中分离得到；3株产单核细胞李斯特菌从牛奶中分离得到（1份牛奶来自奶牛，2份来自水牛）。使用特异性引物对所有3株产单核细胞李斯特菌分离株进行毒力基因actA、hlyA和iap的筛选，结果显示所有基因均存在，这表明生牛奶消费者中存在食源性李斯特菌病的危险可能性。
从9%（18/200）的动物源性食品样本，即牛奶、奶制品、肉类和鱼类中分离出了李斯特菌属，其中牛奶样本中的患病率最高。仅从3份牛奶样本中分离出了产单核细胞李斯特菌。在本研究中，斯氏李斯特菌是分离出的主要菌种，其次是无害李斯特菌、威氏李斯特菌和产单核细胞李斯特菌。发现产单核细胞李斯特菌携带actA、hlyA和iap等毒力基因，表明这些分离株具有致病潜力。
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