Occurance, distribution, serotypes and antimicrobial resistance among Salmonella isolated from cattle and environmental samples in Vhembe District, South Africa

Abstract

Salmonella species is the etiologic agent of salmonellosis, which is a zoonotic infection that is characterized by diarrhea and systemic infection. Contaminated foods are usually the vehicles of Salmonella transmission along the food supply chain. Asymptomatic food production animals and effluents also contribute to contamination of meat. Antimicrobials have contributed significantly to treatment of salmonellosis. However, uncontrolled antimicrobial use is among the causes of antibiotic resistance, which results in treatment failure. The aim of this research study was to determine the extent of Salmonella spp contamination during the cattle slaughtering process in South African rural abattoirs (n = 23), water and cattle feaces. In addition, the aim was to determine antimicrobial resistance profiles of the Salmonella spp isolates. The specific objectives were: i) to establish the occurrence and distribution of Salmonella spp on cattle carcasses, hides, and intestinal contents and environmental samples using classical microbiology and molecular techniques; ii) to determine the Salmonella serovars using serotyping; and iii) to determine antimicrobial resistance patterns and multidrug resistance among the Salmonella isolates using the Kirby-Bauer disc diffusion method. Materials and Classical microbiology techniques were used to analyze cattle faeces (n = 400), hides (n = 67), intestinal contents (n = 62), carcass sponges (n = 100), and water from the abattoirs (n = 75) for the presence of Salmonella spp. Further confirmation of the Salmonella isolates was done using Polymerase Chain Reaction whereby the invA gene was targeted. A total of 92 Salmonella spp isolates were recuperated. The 92 Salmonella were serotyped as described in the White-Kauffmann-Le Minor scheme. The 92 Salmonella spp isolates were further subjected to antimicrobial susceptibility examination towards the following antimicrobials: ampicillin (10μg), cefotaxine (30μg), kanamycin (30μg), oxytetracycline (30μg), and enrofloxacin (5μg) by using the Kirby-Bauer disk diffusion procedure. All the isolates carried the invA genes. The average Salmonella spp occurrence on carcasses, hides, and intestinal contents was 35.37% (n = 81). Eleven of the faecal samples (2.75%) tested positive for Salmonella spp. The Salmonella serovar that occurred more frequently was S. Enteritidis. Different serovars that were recognized on carcasses were not automatically found on the hides and intestinal contents. The incompatible frequency of the different Salmonella serovars on carcasses, intestinal contents and hides means that in addition to carriage on hides and in intestinal contents, new external causes that did not form part of this study also play a vital role concerning carcass contamination. Most Salmonella spp (n = 66; 71.7%) isolates were resistant to a minimum of one antimicrobial with main resistance detected towards oxytetracycline (51.90%). This emphasizes on the call for wise antimicrobial use at some stage in animal production and strict sanitation for the duration of slaughtering. Briefly, cattle slaughtered in South African rural abattoirs harboured different types of Salmonella serovars that were resistant to antimicrobials, which could be a public health risk and danger. The outcome should support policymakers with determining the effectiveness of existing sanitary measures during cattle slaughtering in rural abattoirs, which is vital from socio-economic, public health, and epidemiological perspectives.