Identification and methicillin resistance of coagulase-negative staphylococci isolated from nasal cavity of healthy horses.

The aim of this study was an analysis of the staphylococcal flora of the nasal cavity of 42 healthy horses from 4 farms, along with species identification of CoNS isolates and determination of resistance to 18 antimicrobial agents, particularly phenotypic and genotypic methicillin resistance. From the 81 swabs, 87 staphylococci were isolated. All isolates possessed the gap gene but the coa gene was not detected in any of these isolates. Using PCR-RFLP of the gap gene, 82.8% of CoNS were identified: S. equorum (14.9%), S. warneri (14.9%), S. sciuri (12.6%), S. vitulinus (12.6%), S. xylosus (11.5%), S. felis (5.7%), S. haemolyticus (3.4%), S. simulans (3.4%), S. capitis (1.1%), S. chromogenes (1.1%), and S. cohnii subsp. urealyticus (1.1%). To our knowledge, this was the first isolation of S. felis from a horse. The species identity of the remaining Staphylococcus spp. isolates (17.2%) could not be determined from the gap gene PCR-RFLP analysis and 16S rRNA gene sequencing data. Based on 16S-23S intergenic transcribed spacer PCR, 11 different ITS-PCR profiles were identified for the 87 analyzed isolates. Results of API Staph were consistent with molecular identification of 17 (19.5%) isolates. Resistance was detected to only 1 or 2 of the 18 antimicrobial agents tested in the 17.2% CoNS isolates, including 6.9% MRCoNS. The mecA gene was detected in each of the 5 (5.7%) phenotypically cefoxitin-resistant isolates and in 12 (13.8%) isolates susceptible to cefoxitin. In total, from 12 horses (28.6%), 17 (19.5%) MRCoNS were isolated. The highest percentage of MRCoNS was noted among S. sciuri isolates (100%).

The effect of auto-vaccination therapy on the phenotypic variation of one clonal type of Staphylococcus aureus isolated from cows with mastitis.

The aim of this study was to demonstrate the effect of auto-vaccine therapy on selected properties of Staphylococcus aureus strains, isolated from milk of cows with subclinical mastitis. The experiment was based on auto-vaccines which were prepared from S. aureus strains isolated from 16 cows. S. aureus strains isolated from cows on the 7th, 21st and 35th day following auto-vaccination, were analyzed phenotypically and genotypically. The isolated strains represented 17 biotypes all belonging to one clonal type. Increases of new biotypes of S. aureus were detected on the 35th day of therapy. Among 48 re-isolated strains, 18.75% (9/48) revealed single and 12.50% (6/48) multiple phenotypical changes. The present study demonstrated that during auto-vaccine therapy, S. aureus strains can change phenotypically, pointing out the necessity for using precise diagnostic methods, that would make possible a better assessment of the used therapy.

Secretory virulence factors produced by Staphylococcus aureus isolates obtained from mastitic bovine milk--effect on bovine polymorphonuclear neutrophils.

The aim of the research was to test whether exogenic virulence factors secreted by Staphylococcus aureus isolates are involved in mechanisms that allow the bacteria to modulate and evade phagocytosis by bovine polymorphonuclear neutrophils. The research was based on the comparison of the effects of supernatants, prepared from cultures of 30 S. aureus isolates, on the functional properties of bovine neutrophils in vitro. S. aureus isolates were collected from milk samples from cows with clinical mastitis. Supernatants, which were used to treat leukocytes, were prepared from 18 h S. aureus cultures. Exogenic virulence factors secreted by S. aureus isolates significantly influenced the phagocytosis parameters evaluated. Depending on their leukotoxic or superantigenic properties, supernatants could affect the ingestion process, and also showed an influence on the digestion efficiency and phagocytosis carried out by bovine polymorphonuclear neutrophils in vitro.