Epidemiological study on Listeria monocytogenes in Egyptian dairy cattle farms’ insights into genetic diversity of multi-antibiotic-resistant strains by ERIC-PCR

Abstract

Listeria monocytogenes (L. monocytogenes) is frequently detected in ruminants, especially dairy cattle, and associated with the sporadic and epidemic outbreak of listeriosis in farms. In this epidemiological study, the prevalence, virulence, antibiotic resistance profiles, and genetic diversity of L. monocytogenes in three Egyptian dairy cattle farms were investigated. The risk factors associated with the fecal shedding of L. monocytogenes were analyzed. The L. monocytogenes strains from the three farms were categorized into distinct genotypes based on sampling site and sample type through enterobacterial repetitive intergenic consensus polymerase chain reaction (ERIC-PCR). A total of 1896 samples were collected from animals, environments, and milking equipment in the three farms. Results revealed that 137 (7.23%) of these samples were L. monocytogenes positive. The prevalence of L. monocytogenes in the animal samples was high (32.1%), and the main environmental source of prevalent genotypes in the three farms was silage. For all sample types, L. monocytogenes was more prevalent in farm I than in farms II and III. Risk factor analysis showed seasonal variation in production hygiene. For all sample types, L. monocytogenes was significantly more prevalent in winter than in spring and summer. The level of L. monocytogenes fecal shedding was high likely because of increasing age, number of parities, and milk yield in dairy cattle. Two virulence genes, namely, hlyA & prfA, were also detected in 93 strains, whereas only one of these genes was found in 44 residual strains. Conversely, iap was completely absent in all strains. The strains exhibited phenotypic resistance to most of the tested antibiotics, but none of them was resistant to netilmicin or vancomycin. According to sample type, the strains from the animal samples were extremely resistant to amoxicillin (95.2%, 80/84) and cloxacillin (92.9%, 78/84). By comparison, the strains from the environmental samples were highly resistant to cefotaxime (86.95%, 20/23). Furthermore, 25 multi-antibiotic resistance (MAR) patterns were observed in L. monocytogenes strains. All strains had a MAR index of 0.22–0.78 and harbored antibiotic resistance genes, including extended-spectrum β-lactamase (blaCTX-M [92.7%] and blaDHA-1 [66.4%]), quinolones (qnrS [91.2%], qnrA [58.4%], parC [58.4%], and qnrB [51%]), macrolides (erm[B] [76.6%], erm(C) [1.5%], and msr(A) [27%]), trimethoprim (dfrD [65.7%]), and tetracyclines (tet(M) [41.6%], tet(S) [8%], and int-Tn [26.3%]). ERIC-PCR confirmed that the strains were genetically diverse and heterogeneous. A total of 137 isolated L. monocytogenes strains were classified into 22 distinct ERIC-PCR groups (A–V). Among them, ERIC E (10.2%) was the most prevalent group. These results indicated that environment and milking equipment served as reservoirs and potential transmission ways of virulent and multidrug-resistant L. monocytogenes to dairy animals, consequently posing threats to public health. Silage is the main environmental source of prevalent genotypes on all three farms. Therefore, hygienic measures at the farm level should be developed and implemented to reduce L. monocytogenes transmission inside dairy cattle farms.

Prevalence and Antimicrobial Resistance of Virulent Listeria monocytogenes and Cronobacter sakazakii in Dairy Cattle, the Environment, and Dried Milk with the In Vitro Application of Natural Alternative Control

“…L. monocytogenes is more commonly detected in fecal samples than in milk samples, as described in our study and other studies agreeing with our results [ 2 ] (6.8% and 5.9%, respectively). Regarding the prevalence of L. monocytogenes in milk in Egypt, there were variations recorded by [ 1 , 23 ] by36.7 %, 6%.…”

“…Regarding the presence of L. monocytogenes in feces, milk, and environmental samples collected from dairy, the findings of Kim and his colleagues [ 18 ] were consistent with ours, indicating that bovine feces, environmental dairy farm samples, and raw milk can hold a varied set of strains of L. monocytogenes. In Egypt, lower and higher prevalence rates of L. monocytogenes than ours were detected at 7.23% and 28.1% in dairy farms in studies conducted by Elsayed et al and Mohammed and Abdel Aziz, and, respectively [ 2 , 19 ]. These differences in results could be the result of the difference in hygiene level of the farms, varying farming practices, and different weather conditions where the sampling and research study were performed.…”

“…These findings did not match the findings of Mohammed and Abdel Aziz [ 19 ], who detected environmental prevalence (30%) to be higher than animal prevalence (26.30%). Elsayed et al [ 2 ] also detected environmental prevalence (8.3%) to be higher than animal prevalence (6.8%). In the current study, L. monocytogenes was identified in 20% of the examined dairy cow fecal samples.…”

“…Food-producing animals and food products of animal origin are the main reservoirs and vehicles of most zoonotic foodborne pathogens such as Listeria monocytogenes [ 1 , 2 ], or contributed in the infection cycle of Cronobacter sakazakii [ 3 ]. L. monocytogenes is an intracellular Gram-positive bacterium that is widely distributed in different natural environments, such as agricultural, aquacultural, and food-processing environments [ 4 ].…”

“…L. monocytogenes is an intracellular Gram-positive bacterium that is widely distributed in different natural environments, such as agricultural, aquacultural, and food-processing environments [ 4 ]. Infections by L. monocytogenes in humans and animals are characterized by eye infections, keratitis, encephalitis, septicemia, uterine infections resulting in abortions and still births, and subclinical mastitis [ 2 ]. L. monocytogenes pathogenicity is attached to its endurance to a variety of environmental stressors, such as osmotic, thermal, and chilling stressors.…”