Prevalence, Antibiogram and Genetic Characterization of Listeria monocytogenes from Food Products in Egypt

Abstract

World Health Organization classified <i>Listeria monocytogenes</i> as a major notable foodborne pathogen associated with high mortality and hospitalization. The study reports the prevalence, antibiogram, virulence determination and genetic characterization of <i>L. monocytogenes</i> from different food products. A total of 250 food samples, fifty samples each from raw milk, ice cream, minced meat, fish fillet and sausage were collected from the Menoufiya governorate in Egypt. <i>L. monocytogenes</i> was detected in 17 (6.8%) of the tested food samples including minced meat (14%), fish fillet (8%), sausage (6%) and raw milk (6%). The antimicrobial susceptibility assay of 17 <i>L. monocytogenes</i> isolates against seventeen antibiotics belonging to eight antibiotics classes revealed a high susceptibility to norfloxacin (82.3%), amoxicillin-clavulanic acid (76.4%), cefotaxime (70.5%), erythromycin (64.6%), amoxicillin (64.6%), gentamicin (58.7%) and vancomycin (58.7%). While, high resistance was observed against oxytetracycline (76.4%), trimethoprim-sulfamethoxazole (76.4%), chloramphenicol (70.5%), doxycycline (64.6%), levofloxacin (41.2%) and azithromycin (41.2%). Of note, all <i>L. monocytogenes</i> isolates were multidrug-resistant. The multiplex PCR successfully amplified <i>L. monocytogenes</i> in all tested isolates. Screening of the five virulence-related genes revealed the <i>hlyA</i> and <i>iap</i> as the most prevalent genes followed by <i>actA</i> gene, however, the <i>inlA</i> and <i>prfA</i> genes were not detected in any of the studied isolates. The partial <i>16S rRNA</i> gene sequencing of three <i>L. monocytogenes</i> isolates showed a high nucleotide similarity (99.1-99.8%) between the study isolates and various global clones, and phylogenetic analysis clustered these <i>L. monocytogenes</i> strains with other Listeria species including <i>L. welshimeri</i>, <i>L. seeligeri</i> and <i>L. innocua</i>. This study demonstrates the impact of <i>L. monocytogenes</i> as a major contaminant of various food products and suggests more attention to the awareness and hygienic measures in the food industry.