Prevalence of adhesin and toxin genes among isolates of Staphylococcus aureus obtained from mastitic cattle

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.

Investigation of the antibiotic resistance and biofilm-forming ability of Staphylococcus aureus from subclinical bovine mastitis cases

A total of 112 Staphylococcus aureus isolates obtained from subclinical bovine mastitis cases were examined for antibiotic susceptibility and biofilm-forming ability as well as genes responsible for antibiotic resistance, biofilm-forming ability, and adhesin. Antimicrobial susceptibility of the isolates were determined by disk diffusion method. Biofilm forming ability of the isolates were investigated by Congo red agar method, standard tube method, and microplate method. The genes responsible for antibiotic resistance, biofilm-forming ability, and adhesion were examined by PCR. Five isolates (4.5%) were identified as methicillin-resistant Staph. aureus by antibiotic susceptibility testing and confirmed by mecA detection. The resistance rates to penicillin, ampicillin, tetracycline, erythromycin, trimethoprim-sulfamethoxazole, enrofloxacin, and amoxicillin-clavulanic acid were 45.5, 39.3, 33, 26.8, 5.4, 0.9, and 0.9%, respectively. All isolates were susceptible against vancomycin and gentamicin. The blaZ (100%), tetK (67.6%), and ermA (70%) genes were the most common antibiotic-resistance genes. Using Congo red agar, microplate, and standard tube methods, 70.5, 67, and 62.5% of the isolates were found to be biofilm producers, respectively. The percentage rate of icaA, icaD, and bap genes in Staph. aureus isolates were 86.6, 86.6, and 13.4%, respectively. The adhesion molecules fnbA, can, and clfA were detected in 87 (77.7%), 98 (87.5%), and 75 (70%) isolates, respectively. The results indicated that Staph. aureus from sublinical bovine mastitis cases were mainly resistant to β-lactams and, to a lesser extent, to tetracycline and erythromycin. Also, biofilm- and adhesion-related genes, which are increasingly accepted as an important virulence factor in the pathogenesis of Staph. aureus infections, were detected at a high rate.

Occurrence of genes coding for MSCRAMM and biofilm-associated protein Bap in Staphylococcus spp. isolated from bovine subclinical mastitis and relationship with somatic cell counts

This study aimed to elucidate aspects of the epidemiology of bovine subclinical mastitis through the assessment of genes encoding MSCRAMM (microbial surface components recognizing adhesive matrix molecules - a group of adhesins) and protein Bap (implicated in biofilm formation), in coagulase-positive (CPS) and coagulase-negative (CNS) Staphylococcus isolated from subclinical mastitis. Milk samples were collected for microbiological exams, somatic cell count (SCC) and a survey of the genes coding for MSCRAMM (cna, eno, ebpS, fnbA, fnbB and fib) and biofilm-associated protein Bap (bap) in 106 Staphylococcus spp. isolates using PCR. The frequencies of occurrence of eno (82.1%), fnbA (72.6%), fib (71.7%) and bap (56.6%) were higher (P < 0.0001) compared with the other assessed genes (cna, ebpS and fnbB). The higher frequency of occurrence (P < 0.005) of the bap gene in CNS compared with CPS suggests that in these species biofilm formation is an important mechanism for the persistence of the infection. The medians of the SCCs in the samples where eno, fnbA, fib and bap genes were detected were higher compared with Staphylococcus without the assessed genes (P < 0.05) and negative samples (P < 0.01), which indicated that the presence of these MSCRAMM may be related to a higher intensity of the inflammatory process.

Virulence factors genes of Staphylococcus spp. isolated from caprine subclinical mastitis

The aim of this study was to investigate genes involved in adhesion expression, biofilm formation, and enterotoxin production in isolates of Staphylococcus spp. from goats with subclinical mastitis and associate these results with the staphylococcal species. One hundred and twenty-four isolates were identified and polymerase chain reaction (PCR) was performed to detect the following genes: cna, ebpS, eno, fib, fnbA, fnbB, bap, sea, seb, sec, sed and see. The most commonly Staphylococcus species included S. epidermidis, S. lugdunensis, S. chromogenes, S. capitis ss capitis and S. intermedius. With the exception of fnbB, the genes were detected in different frequencies of occurrence in 86.3% of the Staphylococcus spp. isolates. Eno (73.2%) and bap (94.8%) were more frequently detected in coagulase-negative staphylococci (CNS); ebpS (76%), fib (90.9%) and fnbA (87%) were the most frequent genes in coagulase-positive staphylococci (CPS). Regarding enterotoxins, genes sed (28.2%) and see (24.2%) had a higher frequency of occurrence; sec gene was more frequently detected in CPS (58.8%). There was no association between the presence of the genes and the Staphylococcus species. Different virulence factors genes can be detected in caprine subclinical mastitis caused by CNS and CPS. The knowledge of the occurrence of these virulence factors is important for the development of effective control and prevention measures of subclinical mastitis caused by CNS and CPS in goats.

Genetic variations in immunoglobulin G3 and association with staphylococcal intra-mammary infections in cattle and buffaloes

Animals (n = 152) suffering with mastitis were used to study association between immunoglobulin G3 (IgG3) genotypes and staphylococcal mastitis. Thus, animals (affected and unaffected) were evaluated using PCR-RFLP. Restriction digestion of amplicons of IgG3 using BstYI showed allele A and, genotypes AC, AB and AA predominated in Karan Fries, Sahiwal and Murrah, respectively. HphI digestion revealed allele A and, genotypes AC and AB in higher frequency in animals of first group of all the breeds. Additionally, genotypes associated with mastitic infection showed predominance of AB (BstYI) in unaffected animals of Sahiwal and Murrah; whereas AC and AA were observed in affected group only. Genotype AB (HphI) was prevalent in unaffected and AC in affected animals of Karan Fries and Sahiwal. In Murrah, AC was common in affected and unaffected animal; while AB remained in affected category. Identified genotypes associated with determinants of SpA gene of S. aureus strains revealed the significant outcome. For example AB (BstYI) was found to be correalted with SpA ≤ 7R; whereas with SpA > 7R in Karan Fries. Genotypes AA and AB were more favorably associated with SpA ≤ 7R and AB with the SpA > 7R in Sahiwal cattle. The genotype AB seemed influenced (100%) with SpA > 7R and AC in SpA ≤ 7R in cases of Murrah. Similarly, AA (HphI) in Karan Fries was more likely to be correlated with SpA ≤ 7R, while AC with SpA > 7R. Overall, the molecular analysis revealed that IgG3 gene could be use for selection of animals against mastitis. However, further investigations on IgG3 needed to aid in identify disease- resistant animal.