Serotyping and antibiotic resistance of Listeria monocytogenes isolated from raw water buffalo milk and milk products.

This study was aimed to investigate the presence ofListeria monocytogenesin raw water buffalo milk and milk products, besides determining its serotype and the extent of its resistance against various antibiotics. A total of 188 samples of raw water buffalo milk and milk products were collected from Samsun Province, Turkey between November 2012 and May 2013. The classical culture technique was used to isolate and identifyL. monocytogenes, as described in EN ISO 11290-1. The isolates were confirmed asL. monocytogenesby using PCR with (hylA) primers specific for the hemolysin gene. The antimicrobial susceptibility test was achieved by using the VITEK 2 compact system and VITEK 2 AST-P640 card.L. monocytogeneswas found in 7 (3.7%) of the 188 samples. Four of them were obtained from cheese and three from milk samples. Whereas,L. monocytogeneswas not detected in any of the clotted cream samples. A total of 13 isolates were confirmed by PCR asL. monocytogenes. Among these isolates, one was 1/2c (or 3c) (7.6%), three were 4b (or 4d, 4e) (23%), four were 1/2b (or 3b) (30.7%), and the other five isolates were serotype 1/2a (or 3a) (38.4%). The highest antimicrobial resistance was recorded against fosfomycine (100%) followed by oxacillin (92%), penicillin (84%), and erythromycin (69%). However, no resistance was determined against ciprofloxacin, gentamicin, and tigecycline. Practical Application This study showed that some samples of raw buffalo milk and the milk products were contaminated withListeria monocytogenes. The serotype with the highest prevalence was determined asL. monocytogenes1/2a. This study also demonstrated that most of theL. monocytogenesisolates had developed multiresistance to many frequently used medical antimicrobial agents.