Antimicrobial resistance and virulence factors of Listeria monocytogenes isolated from fresh cheese products in Tamaulipas, Mexico

Listeria monocytogenes is a foodborne opportunistic pathogen, that causes outbreaks and fatal cases worldwide. However, only few studies have been published in Mexico reporting the prevalence of this pathogen in food. Therefore, the objective of this current study is to evaluate the prevalence of L. monocytogenes in cheese sold in Tamaulipas, Mexico, and its potential risk to the population. For this purpose, samples were taken in 100 stores during the months of February, June and October 2023, and a total of 300 cheese products in 10 municipalities of Tamaulipas, Mexico were collected. Identification was performed by culture and PCR. Ten virulence factors were also analyzed and susceptibility testing to 14 antibiotics was performed. As a result, a prevalence of L. monocytogenes was detected in 12%. The most frequently detected virulence factors were actA (83.3%, 30/36) and hly (83.3%, 30/36). The strains were resistant to only 9 of the 14 antibiotics tested. The strains showed resistance in higher percentage to sulfamethoxazole/trimethoprim (STX/TMP: 38.8%, 14/36), penicillin (PE: 16.6%, 6/36), tetracycline (TE: 13.8%, 5/36) and amoxicillin/clavulanic acid (AMC: 13.8%, 5/36). The results of the current study show the presence of L. monocytogenes in cheese products sold in Tamaulipas, Mexico. The low prevalence of L. monocytogenes and low resistance to antibiotics could imply a low risk for public health. However, it is necessary to implement monitoring of L. monocytogenes in food, to monitor its potential risk for the consumer.