Genotypic identification of methicillin resistance and virulence factors in Staphylococcus spp. from bovine mastitis milk

Virulence and antimicrobial resistance gene profiles of Staphylococcus aureus associated with clinical mastitis in cattle

Staphylococcus aureus (S. aureus) is the most prevalent microorganism associated with mastitis in cattle, which harbours several virulence factors and antibiotic resistance genes. The present study aimed to characterize S. aureus isolated from mastitic milk of the cattle for antibiotic resistance (blaZ and mecA), haemolysins (hla and hlb) and enterotoxins (sea, seb, sec, and sed) genes. A total of 69 staphylococci were isolated and phenotypically characterized for haemolytic properties on 5% sheep blood agar medium. Out of 69 isolates, 55 (79.71%) were identified as S. aureus by polymerase chain reaction assay. Among S. aureus, the majority of the isolates harboured the gene blaZ (92.73%), followed by coa (89.09%), hlb (60%) and hla (49.09%). Gene mecA responsible for methicillin resistance was detected in 23.64% of S. aureus isolates. Enterotoxin genes seb (9.09%), sec (1.82%) and sed (7.27%) responsible for food poisoning were detected at a comparatively lower rate and none of the S. aureus strain was found positive for sea. Additionally, antimicrobial susceptibility study of S. aureus against 18 antimicrobial discs showed maximum resistance to oxytetracycline, penicillin, and fluoroquinolone groups, contrarily, we observed maximum sensitivity to methicillin and cefuroxime antimicrobials. The high occurrence rate of S. aureus harbouring genes for virulence factors and antimicrobial resistance needs appropriate strategies to control the pathogen spread to the human population.

A meta-analysis of the global prevalence of methicillin-resistant Staphylococcus aureus (MRSA) isolated from clinical and subclinical bovine mastitis

AIMS

This meta-analysis aims to assess the point prevalence of methicillin-resistant Staphylococcus aureus (MRSA) isolated from bovine mastitis cases at the global level.

METHODS AND RESULTS

Several electronic databases were searched for relevant publications (PubMed, EMBASE, Web of Knowledge and Cochrane Library). Heterogeneity between studies was assessed using the Cochrane Q test and I² test statistics based on the random-effect model. The potential sources of between-study heterogeneity were evaluated using subgroup analysis and meta-regression. Sensitivity and publication bias analyses were performed. Sixty-six studies with a total of 77,644 mastitis cases were eligible and included in the analysis. The overall pooled prevalence of MRSA was 4·30% (95% CI: 3·24-5·50) with a significant heterogeneity (I²  = 97·48%, p < 0·001). In the subgroup analysis by region, the highest prevalence was found in Asia (6·47%, 95% CI: 4·33-8·97), and the lowest prevalence was reported in Europe (1·18%, 95% CI: 0·18-2·83). The pooled prevalence was significantly higher in clinical mastitis and cases published during 2016-2020.

CONCLUSIONS

The results of this study suggest that there is a lower prevalence of MRSA in bovine mastitis. However, its prevalence increased in the past 4 years. Therefore, continuous surveillance is urgently required for monitoring the dissemination of these clinically important bacteria.

SIGNIFICANCE OF THE STUDY

To our knowledge, this is the first meta-analysis to estimate the global prevalence of MRSA isolated from bovine mastitis cases.