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PubMed1985

The role of H2O2 and the lactoperoxidase-SCN(-)-H2O2 system on the interaction between two bacteria originating from human dental plaque, Streptococcus rattus (mutans) BHT and Streptococcus mitior LPA-1, grown on human teeth in an artificial mouth.

Teeth were inoculated with either the organisms separately or with a freshly-prepared mixture of both. The apparatus was swept with 5 per cent (v/v) CO2 in either air or N2, and incubated for 90 h. A nutrient supplement containing 1 per cent (w/v) glucose was supplied for 1 h in every 6 h. Both organisms achieved similar numbers when grown aerobically in pure culture, yet in mixed culture there was pronounced inhibition of BHT (p less than 0.001). When the synthetic saliva was supplemented with catalase the strain BHT count in mixed culture was much higher (p less than 0.001). It was concluded, therefore, that the strain LPA-1 produced inhibitory levels of hydrogen peroxide (H2O2) on the tooth surface under aerobic conditions. This was supported by finding that a lower viable count of LPA-1 in pure culture was attained when lactoperoxidase (LPO) was included in the saliva (p less than 0.005), as all components of the LPO-SCN-H2O2 system were presumably present. With the N2-CO2 mixture, conditions were not strictly anaerobic and both catalase and LPO increased all viable counts. Under these conditions, therefore, when H2O2 was limiting, LPO protected bacteria against its bactericidal effect.

Antibiosis↗
PubMed1999

Presence of the Streptococcus suis suilysin gene and expression of MRP and EF correlates with high virulence in Streptococcus suis type 2 isolates.

Nineteen Streptococccus suis type 2 isolates that had been analyzed previously for hemolysin production, ribotype, and virulence in pigs were examined for presence of the gene coding for suilysin by PCR amplification, and southern blot and hybridization techniques. Based on southern blot and hybridization analysis, all isolates tested contained at least a portion of the suilysin gene. PCR amplification of the entire gene resulted in gene fragments from five of the seven highly virulent isolates and none of the moderately virulent or avirulent isolates. Additional PCR analysis showed that mutation or deletions at the 5' end of the suilysin gene in the less virulent isolates prevented amplification of the sly gene fragment from those isolates. The MRP+ (muramidase-released protein) EF+ (extracellular protein) phenotype was also expressed by the same five highly virulent/sly+ isolates.

Animals↗
PubMed2002

Typing of human isolates of Streptococcus agalactiae (group B streptococcus, GBS) strains from Zimbabwe.

Serotyping and genotyping are important tools in epidemiological studies of group B streptococcal (GBS) infections, which are important diseases in man, particularly in newborns. In the present study, 241 GBS isolates from Zimbabwe, comprising 124 carrier isolates from pregnant women and 117 isolates from patients hospitalised for various diseases, were serotyped. Antibodies specific for the capsular polysaccharide antigens (CPAs) Ia, Ib and II-V and antibodies specific for the surface-localised proteins, c(alpha), c(beta), R1, R3 and R4 were used for serotyping. Strains of the CPA types Ia (17%), III (47.7%) and V (23.2%) predominated. Of the various protein antigens, c(alpha) and R4 were expressed with highest frequency, c(alpha) by 100% of the CPA type Ia strains and R4 by 92% of the CPA type III strains. The R3 protein occurred frequently (24%), especially in type V strains (84%). A total of 25 serovariants was detected in the strain collection with the variants Ia/c(alpha) (16%), III/R4 (43.5%) and V/c(alpha), R3 (14.1%) occurring with the highest frequency. Serotype and subtype distribution of the carrier isolates were essentially similar to those of the disease-associated isolates. Genomic heterogeneity was demonstrated by pulsed-field gel electrophoresis of type III/R4 and type V/c(alpha), R3 isolates, but to a much lesser extent than recorded with Norwegian strains. These results demonstrate that many variants of GBS occur in the Zimbabwean population. The data obtained may assist in the formulation of a possible future GBS vaccine for Zimbabwe and perhaps for other African countries.

Adult↗