Abstract
The aim of the present study was to estimate the prevalence of Salmonella and investigate the dominant serovars distribution in raw beef and to screen the isolated serovars for the prescense of beta-lactamases and virulence genes. A total of 150 samples of raw beef sold at butcher shops (n = 75) and supermarkets (n = 75) in Karachi city were collected (50 samples each from muscles, lymph nodes, and minced beef). The samples were cultured according to the ISO-6579-1guidlines. The overall prevalence of Salmonella strains was found to be 21.34%. A total of 56 isolates of Salmonella belonging to four serogroups (Salmonella Pullorum, Salmonella Enteritidis, Salmonella Typhimurium and Salmonella Choleraesuis) were isolated from beef muscles (12%), lymph nodes (24%) and minced beef (28%) samples collected from butcher shops (av. 21.34%). No Salmonella was detected in beef samples collected from supermarkets. S. Enteritidis contamination was highest (37.5%), followed by S. Choleraesuis (30.4%), S. Pullorum (19.6%) and S. Typhimurium (12.5 %). Antibiotic susceptibility testing revealed that Salmonella isolates were highly resistant to Oxytetracycline (90%), Ampicillin (90.5%), Amoxicillin (81.1%), Tetracycline (76%), Neomycin, (79.8%) and Ciprofloxacin (61.4%). The Salmonella isolates examined were more susceptible to the Cephalosporin antibiotics such as Cefixime (43.2%), Cefepime (48.2) and Cefoxitin (49.8%). PCR based screening of blaTEM, blaCTX-M and blaSHV revealed that blaCTX-M and blaTEM were the dominant resistant genes in S. Enteritidis and S. Typhimurium followed by S. Pullorum and S. Choleraesuis whereas blaSHV was the least detected beta-lactamase in Salmonella isolates. Virulence genes screening revealed that at least five genes were present in all the serovars, highest being present in S. Enteritidis (12/17) and S. Typhimurium (12/17). S. Cholerasuis (5/17) carried the least number of virulence genes followed by S. Pullorum (6/17). The present data suggest that beef samples from butcher shops of Karachi city are heavily contaminated with MDR Salmonella. The presence of resistance and virulence genes in MDR strains of Salmonella may play a significant role in transmission and development of Salmonella infection in humans.
Highlights
Foodborne diseases pose a significant threat to global health
Out of 75 different beef samples from butcher shops, 16 (21.3%) tested positive for Salmonella, while no sample was tested positive for Salmonella collected from supermarkets in Karachi city
To the best of our knowledge, this isisthe of prevalence and characterization of Salmonella isolates detected in raw beef in Karachi city, Pakistan
Summary
According to recent epidemiological data, 94 million cases of salmonellosis are reported globally, of Antibiotics 2020, 9, 73; doi:10.3390/antibiotics9020073 www.mdpi.com/journal/antibiotics. Antibiotics 2020, 9, 73 which 83.3 million cases are due to the consumption of contaminated food [2]. In USA, 40,000 cases of non-typhoidal salmonellosis are reported annually [3]. The prevalence rate of salmonellosis in European Union was 23.4 cases per 100,000 population in 2014 [4]. The prevalence rate of salmonellosis and its underlying causes may vary significantly with geographical boundaries. Foods of animal origin have been considered a significant cause of salmonellosis in humans. In the USA, salmonellosis is caused by the consumption of contaminated eggs, poultry and beef, and minced beef [7]
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