Coagulase-negative Staphylococci from Bovine Milk: Virulent gene detection, and Antibiogram Profiles

Abstract

Background Coagulase-negative Staphylococcus species are an emerging cause of intramammary infection, posing a significant economic and public health threat. The cross-sectional study was conducted to isolate and assess virulence factors and antibiogram profiles of coagulase-negative Staphylococcus species in 290 milk samples collected from February to August 2022. Species isolation and identification were performed by plate culturing and biochemical tests and single-plex PCR was used for the detection of virulent genes. The antimicrobial susceptibility profile of each coagulase-negative Staphylococcus species isolate was determined by the Kirby-Bauer disc diffusion test. Results Coagulase-negative Staphylococcus species were isolated in 28.6%, (83/290) of the samples. Of these, the S. epidermidis, S. sciuri, S. warneri, S. haemolyticus, S. simulans, S. chromogens, S. cohnii, and S. captis species were isolated at the rates of 11, 5.2, 3.4, 3.1, 3.1, 1, 1, and 0.7% respectively. Coagulase-negative Staphylococcus species carried 26.5, 22.1, 21.7, 9.6, 9.6 and 8.4% of the ica D, Pvl, Mec A, hlb, Sec, and hla virulent genes respectively. All the isolates showed a high percentage (100%) of resistance to Amoxicillin, Ampicillin, and Cefotetan and 37.5% of resistance to Oxacillin. The majority (54.2%) of coagulase-negative isolates also showed multidrug resistance. Conclusion The present study revealed that coagulase-negative Staphylococcus species isolates were found carriage of one or more virulent and enterotoxin genes responsible for intramammary and food poisoning infections. The majority of the isolates (54.2%) were also found multidrug resistant. Thus, urgent disease control and prevention measures are warranted to reduce the deleterious impact of coagulase-negative species. This study is the first to document the detection of virulent and food poisoning genes in coagulase-negative Staphylococcus species from milk in Ethiopia.