Prevalence of Streptococcus suis Isolated from Clinically Healthy Sows in China

Streptococcus suis is an important pathogen in pigs. Transmission of this pathogen is generally believed to occur between healthy carrier sows and their offspring, so the carrier status of S. suis in healthy sows is important for the control of S. suis infections in pigs, especially in suckling and growing pigs. In this study, the prevalence of S. suis isolated from clinically healthy sows in China was studied for the first time. A total of 1 043 tonsil samples were collected from clinically healthy sows from 10 regions in China from 2005 to 2007. Among the 421 S. suis isolates, 31 strains were identified as capsular type 2. The results showed that S. suis was widespread in swine herds in China with the carrier rates in different herds ranging from 19.5 to 93.9%. Overall, 40.4 and 3.0% of clinically healthy sows harbored S. suis and capsular type 2 in their palatine tonsils, respectively. Statistically significant differences of carrier rates of S. suis and capsular type 2 between the different farms were observed, which was independent of herd sizes and geographic distributions of different herds.

Identification of a phage-derived depolymerase specific for KL47 capsule of Klebsiella pneumoniae and its therapeutic potential in mice

Klebsiella pneumoniae is one of the major pathogens causing global multidrug-resistant infections.Therefore,strategies for preventing and controlling the infections are urgently needed.Phage depolymerase,often found in the tail fiber protein or the tail spike protein,is reported to have antibiofilm activity.In this study,phage P560isolated from sewage showed specific for capsule locus type KL47 K.pneumoniae,and the enlarged haloes around plaques indicated that P560 encoded a depolymerase.The capsule depolymerase,ORF43,named P560dep,derived from phage P560 was expressed,purified,characterized and evaluated for enzymatic activity as well as specificity.We reported that the capsule depolymerase P560dep,can digest the capsule polysaccharides on the surface of KL47 type K.pneumoniae,and the depolymerization spectrum of P560dep matched to the host range of phage P560,KL47 K.pneumoniae.Crystal violet staining assay showed that P560dep was able to significantly inhibit biofilm formation.Further,a single dose(50μg/mouse)of depolymerase intraperitoneal injection protected 90%–100%of mice from lethal challenge before or after infection by KL47 carbapenem-resistant K.pneumoniae.And pathological changes were alleviated in lung and liver of mice infected by KL47 type K.pneumoniae.It is demonstrated that depolymerase P560dep as an attractive antivirulence agent represents a promising tool for antimicrobial therapy.