Molecular characterization of isolated from milk samples with regard to virulence factors and antibiotic resistance.

BACKGROUND AND AIM

Raw milk is considered an essential source of nutrition during all stages of human life because it offers a valuable supply of protein and minerals. Importantly, milk is considered a good media for the growth and contamination of many pathogenic bacteria, especially food-borne pathogens such as . Thus, the objective of this study was to characterize and detect its virulence factors and antibiotic resistance from raw milk samples.

MATERIALS AND METHODS

Raw milk samples (n=100) were collected from different localities in Qena, Egypt, and investigated for the presence of using different biochemical tests, IMViC tests, serotyping to detect somatic antigen type, and molecularly by polymerase chain reaction (PCR) tests. The presence of different virulence and antimicrobial genes (, , , , , and genes) in isolates was evaluated using PCR.

RESULTS

The results demonstrated that 10 out of 100 milk samples were contaminated with . Depending on serology, the isolates were classified as O114 (one isolate), O27 (two isolates), O111 (one isolate), O125 (two isolates), and untypeable (five isolates) . The sequencing of partially amplified 16S rRNA of the untypeable isolates resulted in one isolate, which was initially misidentified as untypeable but later proved as . Moreover, antibacterial susceptibility analysis revealed that nearly all isolates were resistant to more than 3 families of antibiotics, particularly to b-lactams, clindamycin, and rifampin. PCR results demonstrated that all isolates showed an accurate amplicon for the and genes, four isolates harbored gene, other four harbored gene, and only one isolate exhibited a positive gene.

CONCLUSION

Our study explored vital methods for identifying as a harmful pathogen of raw milk using 16S rRNA sequencing, phylogenetic analysis, and detection of virulence factors and antibiotic-resistant genes.