Clinico-epidemiological investigation of methicillin resistant Staphylococcus aureus from subclinical mastitis in dairy goats

Abstract

Risk factors association with the prevalence of Subclinical Mastitis (SCM) caused by resistant type of Staphylococcus aureus (S. aureus) also called as Methicillin Resistant Staphylococcus aureus (MRSA) in dairy goats in Pakistan a cross sectional study was planned. Milk samples from 385 goats in two districts of Punjab, namely Mianwali (n=192) and Narowal (n=193) were screened using rapid field diagnostic test known as Surf Field Mastitis Test (SFMT) for the presence of hidden type of subclinical mastitis. Positive samples of milk were further subjected for detection of Staphylococcus aureus (S. aureus) in these samples. Identification of MRSA was confirmed through phenotypic—using disc diffusion test—as well as genotypic method—through amplification of mecA gene. A data capture form was used for recording of various assumed determinants related with SCM. The study revealed that 39.2% (151/385) samples were positive for SCM and among these a majority (80.8%, 122/151) was positive for S. aureus. Prevalence of MRSA based on disc diffusion test was 18.8% (23/122) while PCR based prevalence was recorded to be 6.5% (8/122). All the study isolates showed 99% homology with MRSA isolates from India, Turkey and Japan with accession numbers MH798869, EU790488 and NG047938 respectively, available in NCBI database. Milkers’ care and hygienic measures during milking, milk yield, use of teat dips, presence of ticks, mixed type of grazing and farm-services by professionals were found to be the key determinants associated with the occurrence of SCM in goats. This is first study regarding identification of MRSA by using PCR isolated from goats in Pakistan and the study will be helpful to provide information for developing control strategies against mastitis in goats. In another study, a laboratory trial was conducted to determine the effected of various antibiotics and non-antibiotics (NSAIDs) on MRSA. The isolates of MRSA that were confirmed through PCR were analyzed in in-vitro as well as in-vivo susceptibility trials. Results of in-vitro antibiotic susceptibility trials showed that MRSA was 100% resistance to Cefoxitin, 37.5% to Gentamicin and Amikacin, 25% to Oxytetracycline, 12.5% to Tylosin, Fusidic acid and Vancomycin, while it was sensitive to Ciprofloxacin, Levofloxacin, Moxifloxacin, Trimethoprim + Sulfamethoxazole and Linezolid. Synergistic effect was observed when resistant antibiotics (Oxytetracycline/Gentamicin) were combined with sensitive antibiotics (Ciprofloxacin/Linezolid). Combination of Non-antibiotics (NSAIDs) with resistant antibiotics revealed that Meloxicam showed partial synergism with both Oxytetracycline and Gentamicin, while Flunixin Meglumine presented synergistic effect with Oxytetracycline and partial synergism with Gentamicin. Diclofenac Sodium revealed additive effect with Oxytetracycline while in case of Gentamicin indifferent effect was observed. Results of in-vivo trials showed that combinations of Oxytetracycline with Meloxicam/Flunixin Meglumine and Gentamicin with Meloxicam/Flunixin Meglumine were effective. The study concluded that the resistance against milk borne zoonotic MRSA infections can be successfully addressed by combining resistant antibiotics with NSAIDs. Flunixin Meglumine can be used in combination with oxytetracycline against MRSA infection.