Occurrence and Antimicrobial Susceptibility Patterns of Staphylococcus aureus and Salmonella species in Fresh Milk and Milk Products Sold in Zaria and Environs, Kaduna State, Nigeria

Abstract

Staphylococcal infections and salmonellosis are important food-borne diseases affecting both humans and animals, and the spread of antibiotic  resistant bacteria to humans through the consumption of animal food products remains a challenge. To determine the occurrence and antimicrobial  susceptibility pattern of Staphylococcus aureus and Salmonella in fresh milk and milk products sold in Zaria and environs, Kaduna  State, Nigeria, ninety samples were purchased comprising of 49 pasteurized milk, 20 ghee (Clarified butter) and 21 fresh milk samples in Zaria. The  Samples were pre-enriched before plating on a suitable selective media. Biochemical and Sugar fermentation tests were used to detect S. aureus  and Salmonella isolates; also, antimicrobial susceptibility test was carried out on positive isolates. The overall prevalence of S. aureus and  Salmonella spp. in fresh milk and milk products (pasteurized milk and ghee) were 31.1% (28/90) and 6.7% (6/90), respectively. Higher prevalence of  S. aureus was found in fresh milk (38.1%) than in ghee (35%) and pasteurized milk (26.5%). Also, a higher prevalence of Salmonella organism was  found in fresh milk (9.5%) than in pasteurized milk (6.1%) and ghee (5%). Positive isolates of S. aureus showed the highest percentage of antibiotic  resistance to oxacillin (100%), then tetracycline (64%) and vancomycin (57.1%), while positive isolates of Salmonella showed oxacillin (100%) and  vancomycin (100%), followed by tetracycline (33.3%). Most of the isolates displayed resistance to more than three (3) different classes of  antimicrobials, indicating multidrug resistance. Therefore, there is a need for education and public awareness regarding hygienic processing,  handling and storage of fresh milk and milk products; thus, the abuse and indiscriminate use of antibiotics in animals should be discouraged.