Antibiotic Resistance and Molecular Profiling of the Clinical Isolates of Staphylococcus aureus Causing Bovine Mastitis from India

Abstract

Staphylococcus aureus is an opportunistic bacterium known to cause severe infections in humans and animals. It is one of the major bacteria causing subclinical and clinical mastitis, leading to significant economic losses in livestock industry. In this study, we have isolated and characterized 80 S. aureus clinical isolates from mastitis-infected animals. The analysis of antimicrobial susceptibility, molecular typing, biofilm production and genetic determinants was performed to understand molecular and phenotypic features of the prevalent pathogen. Our antibiotic susceptibility assays showed the majority (57.5%) of isolates to be multidrug-resistant (MDR), 38.75% resistant and 3.75% sensitive. We found 25% isolates to be methicillin-resistant S. aureus (MRSA) based on oxacillin susceptibility assays. In the MRSA group, maximum isolates (95%) were MDR compared to 45% in MSSA. Multilocus sequence typing (MLST) revealed 15 different STs; ST-97 was the most common ST, followed by ST-2459, ST-1, ST-9 and ST-72. The agr typing showed agr-I as the most common type, followed by type II and III. Most isolates developed biofilms, which ranged in intensity from strong to weak. The presence or absence of lukS, a virulence-related gene, was found to have a substantial relationship with the biofilm phenotype. However, no significant association was found between biofilm formation and antimicrobial resistance or other virulence genes. We also found four MRSA isolates that were mecA negative based on molecular assays. Our findings reveal the prevalence of multidrug-resistant S. aureus clinical isolates in India that are biofilm positive and have critical genetic factors for disease pathogenesis causing bovine mastitis. This study emphasizes the need for the comprehensive surveillance of S. aureus and other mastitis-causing pathogens to control the disease effectively.

Occurrence and Characteristics of Staphylococcus aureus Strains along the Production Chain of Raw Milk Cheeses in Poland

“…There are currently few studies focusing on assessing the whole production chain of cheeses from unpasteurized milk [ 4 , 37 , 38 ]. Most studies have focused on the evaluation of S. aureus strains isolated from raw milk from cows with clinical or subclinical mastitis or only in finished products [ 24 , 29 , 39 , 40 , 41 , 42 ]. Nevertheless, estimation of the prevalence and genetic determinants of S. aureus is always important to facilitate the implementation of rational mitigation strategies and to avoid the dissemination of this pathogen through the food chain [ 43 ].…”

Emerging Approaches for Mitigating Biofilm-Formation-Associated Infections in Farm, Wild, and Companion Animals

“…Moreover, the mammary gland is susceptible to colonization by other pathogens such as Streptococcus spp., E. coli , and coliform species, leading to parenchymal inflammation and disease. Mastitis can manifest in subclinical and clinical forms, impacting milk characteristics, quality, and sanitation, while also contaminating milking instruments, increasing the risk of zoonosis [ 62 , 63 , 64 , 65 , 75 ].…”

Antibiotic-resistant bacteria in bovine milk in India

“…In a study, it was observed that some isolates of S. aureus from mastitis milk samples of cows were resistant to all antibiotics tested viz, ampicillin, amoxicillin-sulbactam, ceftriaxone, enrofloxacin, methicillin, and penicillin [ 55 ]. Additionally, resistance profiling against various antibiotics revealed that most S. aureus isolates were resistant to multiple antibiotics [ 56 ]. Given that the S. aureus isolates were resistant to more than three antibiotics, they were MDR bacteria.…”

“…In a similar study, the resistance pattern of S. aureus to ampicillin, methicillin, oxacillin, ceftriaxone, rifampicin, vancomycin, amoxiclav, oxytetracycline, erythromycin, nitrofurantoin, cefuroxime, gentamicin, norfloxacin, ciprofloxacin, and levofloxacin was observed in milk of cows and buffaloes [ 58 ]. Milk samples of cows suffering from Staphylococcal mastitis showed resistance against gentamicin, clindamycin, erythromycin, rifampicin, tetracycline, oxacillin, cefoxitin, and teicoplanin [ 56 ]. The above resistance patterns indicate the resistance of S. aureus to several antibiotics over the years.…”