The role of staphylococci in subclinical mastitis of cows and lytic phage isolation against to Staphylococcus aureus.

AIM: This study was conducted to determine the role of Staphylococcus in the formation of subclinical mastitis in cows and to isolate the phage against isolated Staphylococcus aureus strains. MATERIALS AND METHODS: In this study, 400 milk cows were screened by California Mastitis Test (CMT) for subclinical mastitis and 235 udders of 96 cows, which were determined to be positive, were evaluated for Staphylococcus. Milk samples were evaluated using conventional and molecular methods. In addition, phage isolation studies were performed against S. aureus strains causing mastitis. RESULTS: At the result of cultural examination, of 235 milk samples that were found as positive for mastitis by CMT, a total of 117 (49.7%) Staphylococcus spp. were isolated as a distribution of 74 (63.24%) coagulase-positive staphylococci and 43 (36.75%) coagulase-negative staphylococci. Of these isolates, 76 (64.95%) were characterized as S. aureus both conventional and molecular techniques. Lytic bacteriophages against two S. aureus strains which were isolated from mastitic milk samples were obtained from wastewater samples. CONCLUSION: The results of this study show that a significant portion of subclinical mastitis was formed by staphylococci. In addition, phage isolation against S. aureus strains isolated can be considered as one of the steps to be applied in the prophylaxis and treatment of such infections.

Virulence plasmid stability in environmentally occurring Bacillus anthracis from North East Turkey.

The Bacillus anthracis virulence plasmid pXO2, which encodes for a polypeptide capsule, can be lost during long term laboratory storage. To determine if pXO2 is lost in nature we screened B. anthracis isolates obtained from B. anthracis spores from contaminated animal burial sites in Turkey for their ability to express a capsule upon primary culture. A total of 672 B. anthracis colonies were examined of which ten produced a mixed mucoid (capsule +ve)/non-mucoid (capsule -ve) phenotype and a further one colony yielded non-mucoid colonies upon repeated culture. Screening by PCR using pXO2 specific primers revealed that seven of these isolates had eliminated the plasmid. Of the four colonies which were positive by PCR, one regained the ability to express a capsule upon repeated culture suggesting that the defect was reversible. This is an important observation as capsule expression is a principal marker of virulence and in the absence of PCR serves as a key diagnostic marker. The results of this preliminary study suggest that pXO2 is lost in nature and that further studies are need to determine the mechanisms by which this occurs.

The effect of prolonged storage on the virulence of isolates of Bacillus anthracis obtained from environmental and animal sources in the Kars Region of Turkey.

The stability of the plasmid-mediated virulence factors of Bacillus anthracis, a tripartite toxin located on pXO1 and an antiphagocytic capsule encoded by genes located on pXO2, following long-term storage was investigated. A collection of 159 isolates of B. anthracis were collected from the Kars region of Turkey between 2000 and 2013 and stored at -20°C in Brucella broth supplemented with 20% glycerine. A total of 142 isolates were recovered of which one failed to express a capsule upon primary culture. A further 35 isolates yielded a mixture of mucoid and non-mucoid colonies; the majority of which had lost the pXO2 plasmid as determined by PCR analysis. Results would suggest that pXO2 is more unstable than pXO1 and that this instability increases with the length of storage. It is possible that the pXO2-deficient isolates of B. anthracis described here could be developed into a vaccine to treat at risk animals in the Kars region as many animal vaccines are based upon pXO2 deficiency.