Staphylococcus aureus, a common cause of bovine mastitis, is known for its ability to acquire to antimicrobial resistance and to secrete numerous virulence factors that can exacerbate inflammation. In addition, alpha-hemolysin has an important role in S. aureus infections, diversity of the hla gene (that produces alpha-hmolysin) in S. aureus isolated from bovine mastitis has not been well characterized. The objective was, therefore, to determine diversity of virulence genes, hla gene sequences, and clonal profiles of S. aureus from bovine mastitis in Chinese dairy herds, and to evaluate inter-relationships. The antimicrobials resistance varies from as low as 1.9% (2/103) for CTX to as high as 76.7% (79/103) for penicilin in the 103 isolates and 46 (44.7%) S. aureus were determined as multi-resistant isolates with diverse resistance patterns. Thirty-eight virulence gene patterns (with variable frequencies) were identified in the 103 isolates and correlated with MLST types, indicating a great diversity. Although the hla gene also had great diversity (14 genotypes), Hla peptides were relatively more conserved. With 7 clonal complexes identified from 24 spa types and 7 MLST types. Regarding the letter, ST 97 was the dominant type in S. aureus from bovine mastitis in China. Furthermore, based on phylogenetic analysis, there was a distinct evolutionary relationship between the hla gene and MLST. Multi-resistant S. aureus occurred in bovine mastitis with diverse resistance patterns. The diversity of virulence gene profiles, especially the hla gene and, their relationship with molecular types were reported for the first time in S. aureus from bovine mastitis, which will be useful for future studies on immunogenicity and vaccine development. In addition, based on the distinct evolutionary relationship between the hla gene and MLST types, we inferred that the hla gene has potential role for molecular typing of S. aureus.

Streptococcus agalactiae (Strep. agalactiae) is bovine mastitis pathogen and has thus became a matter of concern to dairy farms worldwide in terms of economic loss. The aims of this study were to (a) determine virulence genes, and (b) characterize the antimicrobial resistance (AMR) profiles and AMR genes and (c) figure out the relationship between AMR phenotypes and genotypes of Strep. agalactiae isolated from dairy cows in north China. A total of 20 virulence genes and 23 AMR genes of 140 isolates collected from 12 farms in six provinces were studied. The antimicrobial susceptibility of 10 veterinary commonly used antimicrobials were tested using the broth microdilution method. Results showed that all the isolates harbored the virulence genes lacIV, gapC, and dltA. The isolates that harbored the genes lacIII, fbsA, hylB, and cfb exhibited the high prevalence (99.29%), followed by isolates that harbored lacI (98.57%), bibA (97.86%), cylE (97.14%), lacII (92.14%), cspA (52.14%), pavA (25%), bca (2.14%), and scpB (0.71%). The fbsB, lmb, spbI, bac, and rib genes were not detected. The virulence patterns of B (fbsA_cfb_cylE_ hylB_bibA_cspA_ gapC_dltA_lacIII/IV) and C (fbsA_cfb_ bibA _ gapC_ dltA_lacIV) were dominant, accounting for 97.86% of the isolates. The following AMR genes were prevalent: pbp1A (97.14%), tet(M) (95.00%), lnu (A) (80.71%), erm (B) (75.00%), tet(O) (72.14%), blaZ (49.29%), tet(S) (29.29%), blaTEM (25.71%), erm (A) (17.14%), erm (C) (13.57%), tet (L) (10.71%), linB (2.86%), and erm (TR) (2.86%). The pbp2b, mecA1, mecC, lnu (D), erm (F/G/Q), and mef (A) genes were not detected. Eighty percent of the isolates harbored AMR genes and were highly resistant to tetracycline, followed by macrolides (10.71%), lincosamides (9.29%) and β-lactams (4.29%). In conclusion, isolates only exhibited well correlation between tetracyclines resistance phenotype and genotype, and almost all isolates harbored intact combination of virulence genes.

The toxic heavy metal cadmium (Cd) has a significant impact on kidney health. Documents manifested that non-toxic flavonoid quercetin can reduce Cd-induced kidney damage by reducing oxidative stress and inhibiting apoptosis, while the effect of quercetin on Cd-induced renal cell pyroptosis has not been elucidated. In this study, we established a model of Cd poisoning treated with quercetin both in vitro and in vivo. Results revealed that quercetin effectively reversed the decrease in Cd-induced cell viability. Furthermore, Cd increased blood urea nitrogen while reducing GPX and SOD levels, caused histopathological injuries in kidney with a significantly elevated cell pyroptosis characterized by enhanced levels of proteins representing assembly (NLRP3) and activation (pro IL-1β, cleaved IL-1β, and IL-18) of NLRP3 inflammasome as well as pyroptosis executor (pro caspase-1, cleaved caspase-1). However, quercetin administration alleviated kidney injuries above by decreasing cell pyroptosis. Overall, it suggests that kidney cells are susceptible to pyroptotic cell death due to Cd exposure; while quercetin exhibits protective effects through cell pyroptosis inhibition.