Salmonella Serovars, Antibiotic Resistance, and Virulence Factors Isolated from Intestinal Content of Slaughtered Chickens and Ready-to-Eat Chicken Gizzards in the Ilorin Metropolis, Kwara State, Nigeria

Salmonellosis is one of the most common and widely distributed food-borne diseases, and the presence of antimicrobial-resistant Salmonella in poultry and poultry products is a global public health problem. Therefore, a cross-sectional study was conducted from November 2016 to July 2017 with an aim of determining the isolation rates of Salmonella species from the intestinal contents of slaughtered chickens, the most common serotypes that invade and colonize the tissues of chickens in Ilorin, and the susceptibilities of the isolated species to commonly used antibiotics. Four hundred samples of intestinal contents from apparently healthy slaughtered chickens and one hundred ready-to-eat chicken gizzards in Ilorin, Kwara State, were examined for the presence of Salmonella and their serotypes. Salmonellae were isolated and identified according to the techniques recommended by the World Health Organization: preenrichment, selective plating, biochemical testing, and serotyping. A total number of forty-three (43) Salmonella isolates consisting of 33 from intestinal contents and 10 from ready-to-eat chicken gizzards were isolated and identified. There was an overall Salmonella prevalence rate of 8.6% (43/500), and the isolates were distributed as follows: gizzard, 2% (n=10) and intestinal contents, 6.6% (n=33). The predominant serovars were Salmonella enterica subsp. enterica serovar 45: d: 1, 7 (16) and S. Haifa (5). All ready-to-eat chicken gizzards were associated with Salmonella enterica subsp. enterica serovar 45: d: 1, 7 (5). The Salmonella from intestinal contents belong to Salmonella enterica subsp. enterica serovars 45: d: 1, 7 (11) and S. Haifa (5). Salmonella species isolated were 100% resistant to ciprofloxacin, ampicillin, and ceftazidime. This is followed by cloxacillin (81%), tetracycline (75%), and sulfamethoxazole (67%). The Salmonella isolates were, however, 100% sensitive to enrofloxacin, 74% to streptomycin, and 72% to gentamycin antibiotics. The most common serotype was S. enterica subsp. enterica serovar 45: d: 1, 7. All the twenty five Salmonella serovars consisting of twenty-one serotypes (n=21), two of the Salmonella that could not be cultured after enrichment, and the two that were contaminated with Proteus possessed the virulence genes of invA and stn. The Salmonella enterica subsp. enterica serovar 45: d: 1, 7 and S. Haifa possess virulence genes so they are potentially virulent for humans in this area. The national and local health authorities in Nigeria should improve hygiene measures especially at retail slaughter markets to reduce salmonellosis which is one of the most important food-borne diseases in humans.