Prevalence, Serotypes And Antimicrobial Resistance Of Salmonella Isolated From Beef And Animal Feed In Namibia

ABSTRACT

The occurrence of Salmonella is a global challenge in the public health and food production sectors. Contaminated beef and animal feed with Salmonella may lead to infections of humans through food chain. The present study investigated the prevalence, serovar and antimicrobial resistance of strains of Salmonella serovars isolated from beef (meat cuts, meat fluid and carcass swabs) and animal feed (meat-and-bone, and blood meal) samples from the abattoirs in Namibia. Beef (9508) and animal feed (827) samples were examined for the presence of Salmonella. The data showed that 0.85 % (n= 81) of beef were positive for Salmonella. In animal feed, 11.73 % (n = 97) were positive for Salmonella. The prevalence was higher in carcass swab samples than meat cuts and meat fluid but did not differ significantly (p > 0.05) between the products. However, there was a significant difference (p < 0.05) on the prevalence of Salmonella in blood meal as compared to meat-and-bone meal. Forty-four different types of Salmonella serovars were isolated and identified in this study. However, 23 isolated Salmonella serovars could not be identified conclusively. Of the Salmonella serovars isolated, S.Chester was the most common isolated serovar (18.54 %) followed by S. Schwarzengrund (7.30 %), S. Anatum (5.06 %), S. Typhimurium (4.49 %), S. Braenderup (4.49 %) and S. Reading (4.49 %). From 19 Salmonella serovars which exhibited resistance to one or more types of antimicrobials, 15 different Salmonella serovars exhibited resistance to at least two antimicrobials. Most Salmonella were resistant to sulfisoxazole followed by trimethoprim-sulfamethoxazole and tetracycline

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whereas, 80.3% (n= 57) were susceptible to all 16 antimicrobials tested. Resistance to sulfisoxazole and the trimethroprim-suflamethoxazole combination were the most common. Of all Salmonella isolated, 29.21 % (n = 178) exhibited resistance to the antimicrobials used. The resistant isolates belonged to 19 different Salmonella serovars of which 15 different types of serovars showed multidrug resistance (MDR). From the study it was found that the prevalence of Salmonella in Namibia is comparable to some studies in other countries. Few or no similar studies are available in the Southern African region for comparison. The susceptibility of Salmonella to the antimicrobials tested indicated that antimicrobial resistance is not as common and extensive in Namibia as has been reported in many other countries. It also appears that there is a range of antimicrobials available that are effective in managing Salmonella infections in Namibia. However, there is some evidence that resistance is developing and this will need further monitoring to ensure it does not escalate to a problem. This study has helped to understand the prevalence of Salmonella serovars in Namibia and how their antimicrobial resistance pattern may influence on the selection of drugs and the treatment of salmonellosis in humans and animals. It is recommended that continuous studies to be done to monitor the link between the Salmonella serovars and their resistance pattern between food animals and humans.