Abstract
World Health Organization classified Listeria monocytogenes as a major notable foodborne pathogen associated with high mortality and hospitalization. The study reports the prevalence, antibiogram, virulence determination and genetic characterization of L. monocytogenes 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. L. monocytogenes 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 L. monocytogenes 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 L. monocytogenes isolates were multidrug-resistant. The multiplex PCR successfully amplified L. monocytogenes in all tested isolates. Screening of the five virulence-related genes revealed the hlyA and iap as the most prevalent genes followed by actA gene, however, the inlA and prfA genes were not detected in any of the studied isolates. The partial 16S rRNA gene sequencing of three L. monocytogenes isolates showed a high nucleotide similarity (99.1–99.8%) between the study isolates and various global clones, and phylogenetic analysis clustered these L. monocytogenes strains with other Listeria species including L. welshimeri, L. seeligeri and L. innocua. This study demonstrates the impact of L. monocytogenes as a major contaminant of various food products and suggests more attention to the awareness and hygienic measures in the food industry.
Highlights
Listeria monocytogenes is a ubiquitous foodborne pathogen associated with high hospitalization and outbreaks of food-borne illness worldwide [1]
This study describes the virulence and antibiotic resistance profiles of L. monocytogenes detected in various readyto-eat food products from Egypt
The overall prevalence rate of L. monocytogenes from 250 different food products was 6.8%, while other Listeria species, L. innoca, L. grayi, L. ivanovii and L. welshimeri were detected in 3.2%, 2.4%, 0.4% and 0.8% of the samples, respectively
Summary
Listeria monocytogenes is a ubiquitous foodborne pathogen associated with high hospitalization and outbreaks of food-borne illness worldwide [1]. L. monocytogenes causes listeriosis in humans and animals and can be found in varieties of foods and dairy products [2]. The pathogenicity of L. monocytogenes is largely determined by a group of virulence genes. L. monocytogenes strains from dairy herds carried a number of virulence markers including the Listeria pathogenicity islands (LIPI) 3 and LIPI-4 that were associated with severe human infections [4]. The hlyA, plcB and prfA virulence genes have been found in L. monocytogenes strains recovered from blood and milk isolates [2]. The prfA virulence gene is a transcriptional activator identified among pathogenic L. monocytogenes [8]. Biofilm activity is commonly associated with L. monocytogenes of milk origin that carry a variety of virulence and antibiotics resistance genes [2]. Listeria diagnosis is primarily based on isolation and biochemical characterization, which is time consuming
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