Prevalence, Serotyping, and Antimicrobial Resistance Patterns of Listeria Species Isolated from Some Beef Products

Abstract Background: Listeria monocytogenes remains a significant foodborne pathogen of public health concern, particularly in ready-to-eat and processed meat products, with high mortality rates in vulnerable populations. Aims: This study aimed to determine the prevalence, species distribution, serotypes, and antimicrobial resistance patterns of Listeria species in beef products marketed in Egypt. Methods: A total of 75 beef product samples (burger, sausages, and luncheon; n=25 each) were randomly collected from supermarkets and analyzed following ISO 11290-1:2017 standard protocol. Identification was performed using biochemical tests, followed by serological typing of L. monocytogenes isolates. Antimicrobial susceptibility testing was conducted using the disc diffusion method against ten antibiotics according to CLSI standards (M100, 32nd edition, 2022). Results: Listeria species were detected in 11 samples (14.7%), with burger showing the highest contamination rate (24.0%, 6/25), followed by sausages (12.0%, 3/25) and luncheon (8.0%, 2/25). The chi-square analysis revealed significant differences in contamination rates among product types (p < 0.01). Four Listeria species were identified: L. monocytogenes (n=5, 45.5%), L. ivanovii (n=3, 27.3%), L. innocua (n=2, 18.2%), and L. grayi (n=1, 9.1%). Serotyping of L. monocytogenes isolates revealed four different serotypes: 1/2a (n=2), 4d (n=1), 1/2b (n=1), and 3c (n=1). Antimicrobial resistance was alarmingly high, with 100% resistance to ampicillin and clindamycin, 80% to ciprofloxacin and linezolid, and 60% to cefotaxime and erythromycin. All isolates demonstrated multidrug resistance patterns. Conclusion: The findings reveal considerable contamination of beef products with Listeria species, particularly L. monocytogenes, with concerning antimicrobial resistance profiles. These results emphasize the urgent need for enhanced food safety measures, improved hygiene practices in meat processing facilities, and continuous surveillance programs to protect public health.