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

Abstract

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 Escherichia coli. Thus, the objective of this study was to characterize E. coli 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 E. coli 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 (hly, eae, stx1, stx2, blaTEM, tetA(A), and tetB genes) in E. coli isolates was evaluated using PCR. Results: The results demonstrated that 10 out of 100 milk samples were contaminated with E. coli. Depending on serology, the isolates were classified as O114 (one isolate), O27 (two isolates), O111 (one isolate), O125 (two isolates), and untypeable (five isolates) E. coli. The sequencing of partially amplified 16S rRNA of the untypeable isolates resulted in one isolate, which was initially misidentified as untypeable E. coli but later proved as Enterobacter hormaechei. Moreover, antibacterial susceptibility analysis revealed that nearly all isolates were resistant to more than 3 families of antibiotics, particularly to β-lactams, clindamycin, and rifampin. PCR results demonstrated that all E. coli isolates showed an accurate amplicon for the blaTEM and tetA(A) genes, four isolates harbored eae gene, other four harbored tetB gene, and only one isolate exhibited a positive stx2 gene. Conclusion: Our study explored vital methods for identifying E. coli as a harmful pathogen of raw milk using 16S rRNA sequencing, phylogenetic analysis, and detection of virulence factors and antibiotic-resistant genes.

Prevalence and bacteriological identification of Escherichia coli isolated from bovine milk and workers’ urine in dairy farms

“…Younis et al (2021) from milk samples, whileHassan et al (2021) detected the O125 serogroup by a higher percentage (16.7%) from milk samples, but the detection rate of E. coli O125 in human urine samples in the present study was 1.7%, which is similar to results recorded byElsayed et al (2021), who detected the O125 strain in a ratio of 1.6% in human urine isolates. In current results, E. coli O157 was present in a lower proportion than other studies, the prevalence rate of this serotype was only (2.9%) in cow milk samples of Ethiopia(Disassa et al, 2017), (2.3%) in marketed raw cow milk samples in Nigeria (Ghali-Mohammed et al, 2023) and (11.33%) in student urine samples in Nigeria(Saidu and Ebiala, 2022).…”

Maltose-Derivatized Fluorescence Turn-On Imaging Probe for Bacteria Detection

“…Raw milk is a good medium for the growth and contamination of many food-borne pathogenic bacteria such as E. coli . We therefore used milk to test whether Mal-Cz could be used to detect bacteria spiked in milk.…”

“…Raw milk is a good medium for the growth and contamination of many food-borne pathogenic bacteria such as E. coli. 55 We therefore used milk to test whether Mal-Cz could be used to detect bacteria spiked in milk. E. coli or S. epidermidis were spiked in three types of milk: half and half, whole milk and 1% low-fat milk.…”

Surveillance of Escherichia coli in different types of chicken and duck hatcheries: one health outlook

“…Furthermore, validation utilizing PCR-based procedures, a specific, rapid, precise, and reliable method for detecting and characterizing as little as 100 E. coli bacteria, is critical for validating the data acquired from serological approaches ( Younis et al, 2021 ; Fanjip et al, 2022 ). In this study, the DNA of E. coli isolates was amplified by PCR using ECO-f and ECO-r primers with the goal of detecting a 585 bp amplicon of the E. coli 16S rRNA gene ( Tonu et al, 2011 ).…”