Evaluation of contamination of raw milk and traditional butter in Amol city with Listeria monocytogenes and determination of their antibiotic resistance.

Subject Areas : Food Microbial Contamination

Negin Najafi ¹ , Mahdi Sharifi Soltani ² , Atefeh Bozorgi Makerani ³

1 - Department of Veterinary Medicine, Faculty of Veterinary Medicine, Islamic Azad University, Babol Branch, Babol, Iran.
2 - Department of veterinary, Agricultural faculty, Islamic Azad University, Chalous branch, Chalous, Iran
3 - Department of Veterinary Medicine, Faculty of Veterinary Medicine, Islamic Azad University, Babol Branch, Babol, Iran

Received: 2021-12-01 Accepted : 2022-03-07 Published : 2022-12-22

Keywords: Listeria monocytogenes, Antimicrobial susceptibility, raw milk, Amol, Traditional Butter,

Abstract :

Listeria is one of the most important bacteria that contaminates milk and milk products. The main species that causes listeriosis in humans and animals and is transmitted through contaminated food is Listeria monocytogenes. For this purpose, in order to identify Listeria monocytogenes in raw milk and traditional butter, in the spring of 1400, 40 samples of raw milk (20) and traditional butter (20) were collected from traditional dairy stores in Amol city. The samples were immediately transferred to a food microbiology laboratory in cold condition. The samples were first cultured in peptone water enrichment medium and then the enriched samples were transferred to Palkam Listeria selective agar medium with selective Listeria monocytogenes supplementation. Then antimicrobial susceptibility of Listeria monocytogenes isolates was determined by disk diffusion method using the antibiotics ampicillin, gentamicin, erythromycin, chloramphenicol, tetracycline, and ciprofloxacin. From the total samples, the prevalence of Listeria species in raw milk and butter was 35% and 10%, respectively. The results of antibiotic susceptibility and resistance test of raw milk samples showed that they were resistant to ampicillin 85.7% and tetracycline 71.4% and among butter samples only erythromycin was 100% resistant and ampicillin 100% semi-resistant. The mean of the obtained results in the antibiogram test were analyzed with 95% confidence and one-way analysis of variance. The results of the present study indicate the potential risk of infection due to consumption of raw milk and traditional butter to Listeria monocytogenes and raw milk had higher risk than butter.