Efficacy of different brands of penicillin-streptomycin against Staphylococcus aureus: the clinicians’ myths and the realities
Abstract Background Antibiotics must be safe, effective and have acceptable quality to use in both human and veterinary medicine. A cross-sectional study was conducted with the aim of evaluating in vitro efficacy of three brands of penicillin-streptomycin (penstrep) against Staphylococcus aureus isolated from dairy cow milk in Sebeta and Bishoftu, Ethiopia. A standardized questionnaire was also used to assess the knowledge, attitudes and practices (KAP) of veterinarians about brand antibiotics prescribing in dairy farms in the study area. Results A total of 43 S. aureus were isolated from 23 dairy farms. Thirty-three (81.4%) and 10 (23.3%) isolates were susceptible to brand A and intermediate susceptible to brand B, respectively, whereas only one isolate (2.3%) was intermediate susceptible to brand C. The isolates were also tested against the standard discs of penicillin and streptomycin, and the results showed that 42 (97.7%) and 27 (62.8%) of S. aureus were resistant, respectively. The KAP assessment showed penstrep was the most prescribed antibiotic in the dairy farms in the study area, followed by oxytetracycline and sulfa drugs. All veterinarians (100%, 30) agreed that antibiotics imported from Western countries perceived as having higher efficacy than those imported from eastern countries. Similarly, they preferred to use brand A, claiming better clinical improvements compared to the other two brands. The majority (86.7%) and more than half (53.3%) of the respondents agreed on the perception of overuse of antibiotics in veterinary clinics and dairy farms, respectively. Conclusions Penstrep Brand A has had better in vitro efficacy, while brands B and C have not been effective against S. aureus isolates. Moreover, this study revealed that a fixed combination dosage form of penicillin and streptomycin in brand A showed better efficacy towards S. aureus isolates compared to penicillin or streptomycin alone. The perception of the veterinarian about these brands agrees with the in-vitro antibacterial efficacy evaluation. The findings suggest that ineffective brands of penstrep are circulating in the local market, which constitute a potential danger to both human and animal health. Our findings warrant the need for stringent regulation and quality assessment criteria for imported veterinary antimicrobials.