Virulence genes of bovineStaphylococcus aureusfrom persistent and nonpersistent intramammary infections with different clinical characteristics

Abstract

Aims: To screen putative virulence genes in Staphylococcus aureus causing persistent and nonpersistent bovine intramammary infections (IMI) with different clinical characteristics. To examine, whether a possible relationship exists between genetic profile and infection persistence, clinical signs of infection, clonal type determined by pulsed‐field gel electrophoresis (PFGE), and antimicrobial resistance. Methods and Results: One‐hundred and sixty‐one S. aureus isolates derived from bovine IMI, consisting of 17 different PFGE types, were screened by conventional and multiplex‐polymerase chain reaction (PCR) for 24 virulence genes for haemolysins (hla‐hlg), leukocidins (lukED, lukM), exfoliative toxins (eta, etb), enterotoxins (sea‐seo, seu), toxic‐shock syndrome toxin (tst), and genes encoding penicillin (blaZ) and methicillin resistance (mecA). The majority of S. aureus isolated at the onset of mastitis carried haemolysin genes (76·7–97·4%), lukED (96·6%), and at least one gene for pyrogenic toxin superantigen (PTSAg) (69·0%). Strains carrying PTSAg‐encoding genes were more common among predominant PFGE types and in persistent IMI. Strains concomitantly possessing sed, sej, and blaZ, putatively plasmid‐encoded, were typically found in connection with persistent IMI. Conclusions: Our results suggest that certain genetic elements are over‐representative in S. aureus isolates especially from persistent bovine mastitis. This phenomenon seems to be in connection with clonal type and is often concomitant with penicillin resistance. Significance and Impact of the Study: This is the first study to investigate associations between a large number of bacterial factors and outcome of S. aureus mastitis. The finding that widespread clonal types of S. aureus causing bovine mastitis of low treatment response may harbour characteristic genes could be improved for strain‐specific diagnostic purposes.

Characterization of virulence and antibiotic profile and agr typing of Staphylococcus aureus from milk of subclinical mastitis bovine in State of Rio de Janeiro

“…The high frequency of haemolysins genes show that these genes play an important role in pathogenesis of bovine mastitis. Previous studies report that hemolysin production may be unnecessary to cause mastitis, once strains that tested negative for both genes were detected in cattle affected by mastitis (Haveri et al, 2007).…”

“…The α-and β-haemolysins produced by S. aureus are pore-forming exotoxins that induce proinflammatory changes in mammalian cells, inactivate the immune system by their direct cytotoxic effect, and degrade tissues, providing bacteria with nutrients and facilitating spreading to new sites (Haveri et al, 2007). The α-haemolysin, encoded by hla gene, has been suggested to be involved in peracute, gangrenous bovine mastitis.…”

“…In this study, 83.6% (46/ 55) of the tested isolates were resistant to penicillin, similar to data reported from Silva et al (2012), who found 95% of penicillin resistance in S. aureus from subclinical mastitis in Pernambuco, Brazil. Moreover, penicillin resistance of S. aureus has been associated with chronic mastitis due to the low cure rate of mastitis caused by S. aureus resistant to penicillins which makes these animals to be reservoirs of penicillin-resistant S. aureus causing the spread to other animals (Haveri et al, 2007). Silva et al (2012) emphasizes the zoonotic risk of the presence of S. aureus strains resistant to penicillin from bovine mastitis due to the potential risk of transmission to humans of resistance in order to limit or prevent use for treatment.…”

“…Genotypic characterization of S. aureus was performed by amplification of coagulase (coa) (Hookey et al, 1998) and species specific (nuc) (Ciftci et al, 2009) genes. The analysis of virulence factors comprised the detection of the following genes: icaA and icaD (Vasudevan et al, 2003) implicated in the production of slime; fnbA and fnbB that codifies fibronectin binding proteins; cap5 and cap8 related to the expression of capsule (El-Sayed et al, 2006) and the hemolysin genes hlA and hlB (Nilsson et al, 1999).…”

A 3-year long study of Staphylococcus aureus isolates from subclinical mastitis in three Azawak zebu herds at the Sahelian experimental farm of Toukounous, Niger

“…Still, to our knowledge, none of these results can actually explain, from the one hand, the higher prevalence of these three pulsotypes, or, from the other hand, the difference of their isolation rates between years and herds. Indeed if some of the hundreds of the spa gene variants and if the seg and sei genes are more frequently present in S. aureus associated with persistent infections and subclinical mastitis (Haveri et al 2007;Mitra et al 2013;Spa Server Database 2015), no pulsotype association has been described to our knowledge. As already reported, the vast majority of the 75 S. aureus (96 %) test positive for the cap5H or cap8H capsule-encoding genes and are not at random distributed between the different pulsotypes (Ikawaty et al 2010), but the reason for this is unknown.…”