Relationships among superantigen toxin gene profiles, genotypes, and pathogenic characteristics of Staphylococcus aureus isolates from bovine mastitis

Abstract

Staphylococcus aureus is one of the major etiological agents of bovine mastitis, harboring a wide variety of staphylococcal superantigen (SAg) toxin genes. The SAg toxin genes are reported to be closely associated with the pathogenicity of the Staph. aureus causing the bovine mastitis. This study was conducted to investigate SAg toxin gene profiles and to assess the relationships among SAg toxin genes, genotypes of Staph. aureus, and their pathogenic properties. A total of 327 quarter milk samples were collected from bovine mastitis cases for isolation and identification of pathogens. In total, 35 isolates were identified as Staph. aureus, and the prevalence of Staph. aureus in milk samples was 13.6% (35/256). Polymerase chain reaction (PCR) and randomly amplified polymorphic DNA (RAPD) assays were used to detect the SAg toxin genes and to genotype Staph. aureus strains isolated from milk samples of bovine mastitis in 10 dairy herds located in Ningxia, China, respectively. The results showed that among the Staph. aureus isolates (n = 35), 71.4% (n = 25) of isolates carried at least one SAg toxin gene. In total, 18 SAg genes and 21 different gene combination patterns were detected among these isolates. The most common SAg genes in Staph. aureus isolates were sei, sen, and seu (44.0% each), followed by seo, tst, and etB (28.0% each), etA (24.0%), sem and sep (16.0% each), seb, sec, sed, and sek (12.0% each), and sea and seh genes (8.0% each); the seg, sej, and ser genes were present in 4.0% of the isolates. Three gene combinations were found to be related to mobile genetic elements that carried 2 or more genes. The egc-cluster of the seg-sei-sem-sen-seo genes, located on the pathogenicity island Type I υSaβ, was detected in 16% of isolates. Interestingly, we observed 6 RAPD genotypes (I to VI) in Staph. aureus isolates, and 2 of these genotypes were strongly associated with the severity of bovine mastitis; there was a close relationship between the RAPD genotypes and SAg genes. Isolates of RAPD type III were more frequently associated with clinical and subclinical mastitis, whereas strains of type VI were mostly related to subclinical mastitis. In addition, SAg genes were related to severity of bovine mastitis. We conclude that an obvious relationship exists among RAPD genotypes, SAg toxin genes, and severity of bovine mastitis.

Prevalence, antimicrobial resistance and staphylococcal toxin gene of blaTEM-1a-producing Staphylococcus aureus isolated from animals in Chongqing, China

“…However, some studies reported that sec gene was the most prevalent and widespread in SEs [34,37,38], especially in Europe [34,37,38]. Though we did not detect sep gene, it could be found in other provinces in China [1,39,40], ever much higher.…”

Staphylococcus aureus Exotoxins and Their Detection in the Dairy Industry and Mastitis

“…SAgs display two major domains, an oligosaccharide/oligonucleotide binding (OB) fold at the N-terminal domain, and a C-terminal domain with a β-grasp topology. SAgs binding to MHC-II induce activation, in a T cell receptor (TCR) Vβ-specific manner, cellular proliferation, and production of large amounts of cytokines [2]. The association of SAgs, MHC class II, and the TCR β-chain constitute an unconventional T cell activation complex provoking a massive T cell response [3] (Figure 1).…”

“…This study reached the expected conclusion that, although S. aureus isolates from goat and sheep milk were closely related, both were different from the bacteria present in bovine milk [ 1 ]. Different pathogenic properties require different detection methods, both for disease treatment and for gene identification [ 2 ]. To successfully treat this pathogen, it is essential to identify and characterize the virulence gene profiles and the clonal diversity present in S. aureus isolates [ 24 ].…”

“…It is a non-spore-forming, oxidase-negative, nonmotile, cluster-forming, and facultatively anaerobic microorganism that grows at a wide range of temperatures and pHs. In humans, S. aureus colonizes the nasal mucosa and skin in an estimated 50% of the healthy population, but it can also cause hematological infections [2]. S. aureus was firstly identified in 1884 and the mortality rate for patients with S. aureus bacteremia was 82%.…”

Resistencia plasmídica a linezolid en Staphylococcus aureus y estafilococos no productores de coagulasa

“…que los genes sei, sen y seu aparecen en un 44% de los aislados, seo en un 28% y sem y sep en un 16%(Wang et al, 2017).En cepas clínicas se encuentran entre los genes de patogenicidad más frecuentes. Un estudio reciente sobre cepas aisladas de infecciones osteoarticulares detectó la presencia del cluster egc en un 52% de los aislamientos.…”