Adaptation of group A Streptococcus to human amniotic fluid.
BACKGROUND
For more than 100 years, group A Streptococcus has been identified as a cause of severe and, in many cases, fatal infections of the female urogenital tract. Due to advances in hospital hygiene and the advent of antibiotics, this type of infection has been virtually eradicated. However, within the last three decades there has been an increase in severe intra- and post-partum infections attributed to GAS.


METHODS
We hypothesized that GAS alters its transcriptome to survive in human amniotic fluid (AF) and cause disease. To identify genes that were up or down regulated in response to growth in AF, GAS was grown in human AF or standard laboratory media (THY) and samples for expression microarray analysis were collected during mid-logarithmic, late-logarithmic, and stationary growth phases. Microarray analysis was performed using a custom Affymetrix chip and normalized hybridization values derived from three biological replicates were collected at each growth point. Ratios of AF/THY above a 2-fold change and P-value <0.05 were considered significant.


RESULTS
The majority of changes in the GAS transcriptome involved down regulation of multiple adhesins and virulence factors and activation of the stress response. We observed significant changes in genes involved in the arginine deiminase pathway and in the nucleotide de novo synthesis pathway.


CONCLUSIONS
Our work provides new insight into how pathogenic bacteria respond to their environment to establish infection and cause disease.
Sitkiewicz
Izabela
I
Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America.
Green
Nicole M
NM
Guo
Nina
N
Bongiovanni
Ann M
AM
Witkin
Steven S
SS
Musser
James M
JM
D018829:Adhesins, Bacterial / Q000378:metabolism; D000653:Amniotic Fluid / Q000382:microbiology*; D002241:Carbohydrates / Q000737:chemistry; D015536:Down-Regulation; D005260:Female; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D020411:Oligonucleotide Array Sequence Analysis; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000382:microbiology; D012329:RNA, Bacterial / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000378:metabolism*; D037521:Virulence Factors
D018829:Adhesins, Bacterial; D002241:Carbohydrates; D012329:RNA, Bacterial; D037521:Virulence Factors