Characterization of listeria monocytogenes strains isolated from slaughtered animals and slaughterhouse wastewater in istanbul

In this study, it was aimed to determine the presence and serotypes of L. monocytogenes, virulence genes, and antimicrobial resistance profiles of L. monocytogenes in carcass swabs and faeces of bovine animals sent for slaughter in slaughterhouses in Istanbul province and in wastewater samples to be taken from the waste water tank of these slaughterhouses. For this purpose, carcass swabs and faecal samples were collected from 138 bovine animals sent for slaughter in slaughterhouses in Istanbul. In addition, 138 separate slaughterhouse wastewater samples were collected from post-slaughter wastewater treatment units (before biological and chemical treatment). The samples brought to the laboratory were inoculated into Listeria Half Fraser Broth Base ISO media for pre-enrichment and incubated at 30℃ for 24 hours. At the end of the incubation period, the cultures were inoculated into Listeria Fraser Broth Base ISO media for enrichment and incubated at 37ºC for 24 hours under aerobic conditions. After the enrichment phase, the cultures were inoculated into ALOA medium, a differential medium for Listeria spp. and incubated at 37°C for 48 hours under aerobic conditions. Isolates with positive catalase and CAMP and negative oxidase tests were considered as suspected Listeria spp. and BD Phoenix automated biochemical identification system was used for identification. The confirmation, serotyping, and virulence gene detection of the isolates identified as L. monocyotogenes were performed by PCR. In addition, antimicrobial susceptibility profiles of the isolates and the presence of antimicrobial resistance genes were determined. As a result of bacteriological culture, 12 isolates from all samples were identified as L. monocytogenes and then confirmed by PCR L. monocytogenes was isolated from 5 of the carcass swabs, only one of the faecal samples and 6 of the wastewater samples. Serotypes 1/2a, 1/2c, 3a, 3c, 1/2b, 3b, 4b, 4d, and 4e were detected in 5 of the samples obtained from carcass swabs, in only one isolate obtained from faecal samples and in L. monocytogenes isolates isolated from 6 of the wastewater samples. InlA, InlC, InlJ, actA, prfA, hylA virulence genes were detected in all isolates. Resistance to aminoglycoside group antimicrobials was determined in 11 isolates (91.67%). Sulbactam resistance was determined in 6 isolates (50%) and lincosamide resistance in 5 isolates (41.6%). Resistance to β-lactam and macrolide antimicrobials was detected in 4 isolates (33.3%) each. Fluoroquinolone resistance was observed in only one isolate (8.33%). Tetracycline and kanamycin resistance was not observed in any isolate. Six (50%) of the isolates were considered to be multi-resistant. The tet(M) gene was detected in all samples obtained from carcass swabs, and the erm(B) gene was detected in all L. monocytogenes isolates isolated from faecal and wastewater samples. As a result, L. monocytogenes in the carcasses and faeces of cattle sent to slaughter and in post-slaughter wastewater treatment units was considered a public health hazard. In addition, the fact that antimicrobial resistance profiles, which are a growing problem, were detected in this study suggested the need for more extensive and comprehensive studies on the subject.