The frequency of genes encoding three putative group B streptococcal virulence factors among invasive and colonizing isolates.
BACKGROUND
Group B Streptococcus (GBS) causes severe infections in very young infants and invasive disease in pregnant women and adults with underlying medical conditions. GBS pathogenicity varies between and within serotypes, with considerable variation in genetic content between strains. Three proteins, Rib encoded by rib, and alpha and beta C proteins encoded by bca and bac, respectively, have been suggested as potential vaccine candidates for GBS. It is not known, however, whether these genes occur more frequently in invasive versus colonizing GBS strains.


METHODS
We screened 162 invasive and 338 colonizing GBS strains from different collections using dot blot hybridization to assess the frequency of bca, bac and rib. All strains were defined by serotyping for capsular type, and frequency differences were tested using the Chi square test.


RESULTS
Genes encoding the beta C protein (bac) and Rib (rib) occurred at similar frequencies among invasive and colonizing isolates, bac (20% vs. 23%), and rib (28% vs. 20%), while the alpha (bca) C protein was more frequently found in colonizing strains (46%) vs, invasive (29%). Invasive strains were associated with specific serotype/gene combinations.


CONCLUSIONS
Novel virulence factors must be identified to better understand GBS disease.
Manning
Shannon D
SD
National Food Safety and Toxicology Center and Department of Pediatrics and Human Development, Michigan State University, East Lansing, Michigan, USA. Shannon.Manning@ht.msu.edu
Ki
Moran
M
Marrs
Carl F
CF
Kugeler
Kiersten J
KJ
Borchardt
Stephanie M
SM
Baker
Carol J
CJ
Foxman
Betsy
B
D000293:Adolescent; D000328:Adult; D005260:Female; D005787:Gene Frequency; D005798:Genes, Bacterial; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D013290:Streptococcal Infections / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D037521:Virulence Factors / Q000235:genetics*
D037521:Virulence Factors