Molecular Detection of Listeria Species Isolated From Raw Milk with Special Reference to Virulence Determinants and Antimicrobial Resistance in Listeria monocytogenes
Molecular Detection of Listeria Species Isolated From Raw Milk with Special Reference to Virulence Determinants and Antimicrobial Resistance in Listeria monocytogenes
Hams M.A. Mohamed1*, Katreen K.G.2, M.W. Abd Al-Azeem1, Faysal A. Wasel2, Ahmed M. Abd-Eldayem3
ABSTRACT
Listeria monocytogenes is classified as a major foodborne pathogen associated with high mortalities due to severe invasive listeriosis, meningitis and abortion in humans. With particular emphasis on Listeria monocytogenes’ capacity to form biofilms, antimicrobial resistance profile and virulence determinants, the purpose of this study is to discuss the presence of Listeria species in raw milk. In total, 150 samples of raw milk from vendors and nearby dairy farms in Sohag, Egypt, were collected. The samples underwent a bacteriological investigation. The results showed that 22 out of 150 samples had Listeria spp. contamination. Polymerase chain reaction (PCR) using the Listeria iap gene identified 13 of the 22 isolates that were reported as biochemically positive Listeria spp. Eight isolates of Listeria monocytogenes were molecularly confirmed, while the remaining five were subjected to 16S rRNA sequence analysis and identified as L. innocua (three isolates) and L. welshimeri (two isolates). The antibiotic susceptibility profiling revealed multidrug resistance of L. monocytogenes strains against several antimicrobials in addition, they harbored antibiotic resistance genes, including. ampC, aad6, tetM each present in 100% of our isolates and mefA (37.5%). Furthermore, different virulence genes, including the most often found virulence-associated genes hlyA and inlB (100% for each), inlA (50%) were present in our isolates. Interestingly, all of the isolates demonstrated varying degrees of biofilm forming capability. The pathogenicity of L. monocytogenes, particularly virulent, drug-resistant and biofilm-forming strains, is highlighted in this study and can result in a public health danger when present in raw milk. Therefore, it is essential to keep an eye on bacterial resistance in the setting of food production.
Keywords | Listeria spp., L. monocytogenes, Virulence genes, Biofilm, antimicrobial resistance
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