High level antibiotic resistance and relatedness of Staphylococcus aureus in raw cow milk and soft cheese in Abeokuta, Nigeria.

Abstract

Prevalence of pathogenic S. aureus with multiple antibiotic resistance in raw milk and soft cheese in Abeokuta, kept rising and is now becoming a serious public health concern. Therefore, the S. aureus resistance profiles and their resistance relatedness in raw cow milk and soft cheese were studied.A total of 100 raw cow milk samples were randomly collected from boarded and free ranged cattle in different herds in Abeokuta, Nigeria while same number of samples of soft cheese were randomly purchased from various hawkers in different popular markets (Ologborugburu, Alabata, Kotopo, Ita-Oshin, and Lafenwa) in Abeokuta. S. aureus and other bacteria were isolated and biochemically characterized while coagulase S. aureus were tested for their antimicrobial resistance pattern and their resistance relatedness was determined using Dendro-UPGMA construction software.High occurrence rate of E.coli (22.1%), Citrobacter freundii (18.3%) and Pseudomonas fluorescens (16.4%) were found in milk and Pseudomonas fluorescens and Klebsilella specie (14.0%) in soft cheese. A significant rate of coagulase positive Staphylococcus aureus of 9.6% and 5.3% was found in milk and soft cheese samples respectively. Antibiotic resistant pattern show significant 100% resistance of S. aureus strains to Tetracycline, Penicillin and 50% to Amoxicillin while 100% and 92.9% show MIC > 16ug/ml to Amoxicillin, Tetracycline and Penicillin respectively. Similarly, 100% resistance to Tetracycline and Penicillin was shown by the S. aureus obtained in Soft cheese while only 50% show resistance to cefotaxime. All the 24 coagulase S. aureus isolates were divided into two major clusters Sa and Sb with 31% resistance relatedness. The Sa clusters were further divided into two sub-clusters sa1 and sa2 with 34% antibiogram resistance relatedness while sa2 was further divided into two major clades sa2v and sa2i having 46% resistance relatedness. Of 14 S. aureus strains found to belong to clade sa2v, 4 strains were found in milk sold in Ologborugburu, 2 in Alabata and1 in Kotopo. S. aureus strains with same antibiogram profile were found in 4 samples of Soft cheese sold in Kotopo, 3 in Ita-oshi and 3 in Lafenwa. Only 1 S. aurues strain was found to belong to sb cluster. Rapid dissemination of resistant S. aureus across Abeokuta with similar antibiotic resistant profile call for urgent surveillance and practical preventive action against retailing and consumption of raw milk and soft cheese in Abeokuta, Nigeria.

Keywords: S. aureus, antibiotics, resistance, milk, soft cheese