Phenotypic and molecular detection of multi-drug resistant Salmonella Enteritidis, Salmonella Typhimurium and Salmonella species in retail raw beef and chicken

Abstract

Globally, Salmonella is a major cause of foodborne diseases[1,2]. The incidence of non-typhoidal Salmonella is estimated at 1.3 billion cases with annual death rate of 3 million[3]. It results in morbidity, mortality and great economic loss[4,5]. Human salmonellosis is most frequently caused by Salmonella Typhimurium (S. Typhimurium) and Salmonella Enteritidis (S. Enteritidis)[6]. Among the over 2 500 serovars identified within Salmonella enterica subspecies enterica, S. Typhimurium continues to be one of the most frequently recovered from food animals worldwide[7]. Due to its broad host range, S. Typhimurium is also one of the most common serotype isolated from human clinical cases of food-borne salmonellosis. Poor sanitary conditions have been identified to be responsible for the transmission of Salmonella spp., S. Typhimurium (group D) and S. Enteritidis (group B) in developing countries. In sub-Saharan Africa, they have been reported to be the cause of 79%–95% of all bacteriaemic non-typhoidal Salmonella infections or foodborne outbreaks[8,9], and are associated with case fatality rate of 20%– 25%[10]. Salmonella can be transmitted to humans from animals and by consuming foods from animal sources such as milk, egg, poultry meat and beef which serve as reservoirs[11,12]. During the production of meat, the major source of Salmonella contamination of carcasses is the evisceration stage in slaughter house[13]. In order to ensure food safety and for the purpose of food borne disease surveillance, foods should be examined routinely for the presence of Salmonella. Conventional typing methods such as, biotyping, serotyping and phage typing which are based on phenotypic characteristics have been used extensively for this purpose[14]. However, they are less discriminative. Molecular typing methods offer higher discrimination[14] and have been employed for identification of Salmonella spp.[9]. Studies on the molecular typing of microbial isolates have ARTICLE INFO ABSTRACT