Sequence provides insights into pathogen's virulence mechanism.(Brief Article)

2002 SEP 18 - (NewsRx.com & NewsRx.net) -- Scientists have analyzed the complete genome sequence of an emerging human pathogen, Streptococcus agalactiae (also known as group B streptococcus or "strep B"), which is a leading cause of pneumonia and meningitis in newborns and the source of life-threatening illnesses in a growing number of adults with deficient immune systems.

The study, published in the online version of the Proceedings of the National Academy of Sciences USA, not only determined the pathogen's genetic makeup but also compared it to other isolates of the same microbe. That analysis shed light onto why S. agalactiae - which is found in the digestive or genital tracts of many healthy people - has emerged in recent years as a more widespread and virulent cause of illness in certain adults.

"We were surprised to find so many differences among the isolates of this important pathogen," said Herve Tettelin, an associate investigator at the Institute for Genomic Research (TIGR) who led the sequencing project. "Those differences could help explain why some strains of S. agalactiae are much more virulent than others."

Tettelin and other TIGR scientists did the comparative genomics analysis in cooperation with a research group led by Dennis L. Kasper at Harvard Medical School and a team led by Guido Grandi at the vaccine research division of Chiron, SpA, a biomedical company that funded the research project. The research was supported by Chiron and by grants from the National Institutes of Health.

"Completion of the genome sequence represents an important milestone in the study of this organism," said Kasper. "We anticipate that many investigators will take advantage of the S. agalactiae genome sequence to identify new virulence determinants and potential targets for vaccine development."

"We wanted the genome information to identify proteins which can be used in a vaccine," said Guido Grandi, head of biochemistry and molecular biology at Chiron vaccine research. "We have used this new genomic approach already to make a type B meningococcal meningitis vaccine which is now being tested in people. So we know that the strategy works."

To find out more about the molecular reasons for the virulence of what is known as the "serotype V" isolate of S. agalactiae, the authors of the study compared that genome to the genetic makeup of other S. agalactiae strains and also with two different species of streptococci that cause human diseases: S. pneumoniae, which causes pneumonia, meningitis and septicemia, and S. pyogenes, which among other illnesses causes the "strep throat" that can lead to acute rheumatic fever.