The prevalence, genetic diversity and antibiotic resistance of staphylococcus aureus associated with subclinical bovine mastitis in Balikesir, Turkey

Abstract

Subclinical mastitis caused by Staphylococcus aureus is very common in dairy cows and creates serious problems on dairy farms. In this study, we investigated the prevalence, genetic diversity and antimicrobial resistance of S. aureus from subclinical bovine mastitis on 12 dairy herds in Balikesir province of Turkey, by SCCmec and spa typing. Ninety-five isolates of S. aureus were isolated from 725 subclinical mastitic milk samples that exceeded the somatic cell count (SCC) limit of 4 x 10(5) cell/mL. The frequency of MRSA (methicillin-resistant Staphylococcus aureus) and MSSA (methicillin-sensitive S. aureus) was 6.3% (6 isolates) and 93.68% (89 isolates) respectively. SCCmec types of MRSA isolates were community-associated CA-MRSA type IVb (4 isolates) and type IVd (two isolates), while the spa types were T 005 and T 5163 (three isolates from each). The resistance rate of MRSA isolates was 100% for oxacillin and cefoxitin, 83% for penicillin, ampicillin, clindamycin, erythromycin and 66% for gentamicin and trimethoprim/sulfamethoxazole. However, compared to MRSA, the resistance of MSSA isolates was relatively lower. This study supported the scientific data on the occurrence of MRSA and MSSA in subclinical mastitis, and highlighted the need for preventive measures to eliminate or decrease S. aureus contamination of milk in dairy herds.

Supklinički mastitis uzrokovan bakterijom Staphylococcus aureus čest je u mliječnih krava i to izaziva znatne poteškoće u proizvodnji mlijeka. U ovom je radu istražena prevalencija, genetska raznolikost i antimikrobna rezistencija bakterije S. aureus u životinja sa supkliničkim mastitisom. Uključene su krave iz 12 mliječnih stada u pokrajini Balikesir (Turska). Ukupno 95 izolata bakterije S. aureus dobiveno je od 725 uzoraka mlijeka sa supkliničkim mastitisom, pri čemu je broj somatskih stanica (SCC) bio veći od 4 x 105 stanica/mL. Genetska raznolikost izolata je analizirana primjenom SCCmec i spa tipizacije. Učestalost MRSA-e (Staphylococcus aureus rezistentan na meticilin) bila je 6,3 % (6 izolata), a MSSA-e (S. aureus osjetljiv na meticilin) 93,68 % (89 izolata). SCCmec tipovi MRSA izolata bili su iz zajednice CA-MRSA tip IVb (četiri izolata) i tip IVd (dva izolata), dok su tipovi spa bili T005 i T 5163 (po tri izolata od svakoga). Stopa rezistencije MRSA izolata bila je 100 % za oksacilin i cefoksitin, 83 % za penicilin, ampicilin, klindamicin, eritromicin i 66 % za gentamicin i trimetoprim-sulfametoksazol. U usporedbi s MRSA-om, rezistencija MSSA izolata bila je relativno niža. Ovo istraživanje potkrijepljuje znanstvene podatke o pojavnosti MRSA-e i MSSA-e kod supkliničkog mastitisa, te naglašava potrebu za preventivnim mjerama kojima bi se u stadima mliječnih krava spriječila ili smanjila kontaminacija mlijeka bakterijom S. aureus.