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Expression of Bacteroides fragilis hemolysins in vivo and role of HlyBA in an intra-abdominal infection model.

Abstract
Bacteroides fragilis is the most frequent opportunistic pathogen isolated from anaerobic infections. However, there is a paucity of information regarding the genetic and molecular aspects of gene expression of its virulence factors during extra-intestinal infections. A potential virulence factor that has received little attention is the ability of B. fragilis to produce hemolysins. In this study, an implanted perforated table tennis "ping-pong" ball was used as an intra-abdominal artificial abscess model in the rat. This procedure provided sufficient infected exudate for gene expression studies in vivo. Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to quantify the relative expression of hlyA, hlyB, hlyC, hlyD, hlyE, hlyF, hlyG, and hlyIII mRNAs. The hlyA mRNA was induced approximately sixfold after 4 days postinfection compared with the mRNA levels in the inoculum culture prior to infection. The hlyB mRNA increased approximately sixfold after 4 days and 12-fold after 8 days postinfection. Expression of hlyC mRNA increased sixfold after 1 day, 45-fold after 4 days, and 16-fold after 8 days postinfection, respectively. The hlyD and hlyE mRNAs were induced approximately 40-fold and 30-fold, respectively, after 4-days postinfection. The hlyF expression increased approximately threefold after 4-days postinfection. hlyG was induced approximately fivefold after 4 and 8 days postinfection. The hlyIII mRNA levels had a steady increase of approximately four-, eight-, and 12-fold following 1, 4, and 8 days postinfection, respectively. These findings suggest that B. fragilis hemolysins are induced and differentially regulated in vivo. Both parent and hlyBA mutant strains reached levels of approximately 3-8 × 10(9) cfu/mL after 1 day postinfection. However, the hlyBA mutant strain lost 2 logs in viable cell counts compared with the parent strain after 8 days postinfection. This is the first study showing HlyBA is a virulence factor which plays a role in B. fragilis survival in an intra-abdominal abscess model.
AuthorsLeandro A Lobo, Audrey L Jenkins, C Jeffrey Smith, Edson R Rocha
JournalMicrobiologyOpen (Microbiologyopen) Vol. 2 Issue 2 Pg. 326-37 (Apr 2013) ISSN: 2045-8827 [Electronic] England
PMID23441096 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)
Copyright© 2013 The Authors. Published by Blackwell Publishing Ltd.
Chemical References
  • Bacterial Proteins
  • Carrier Proteins
  • Hemolysin Proteins
  • Hlyb protein, Bacteria
  • RNA, Bacterial
  • RNA, Messenger
Topics
  • Abdominal Abscess (microbiology, pathology)
  • Animals
  • Bacterial Load
  • Bacterial Proteins (genetics, metabolism)
  • Bacteroides fragilis (genetics, pathogenicity)
  • Carrier Proteins (genetics, metabolism)
  • Disease Models, Animal
  • Enzyme-Linked Immunosorbent Assay
  • Hemolysin Proteins (genetics, metabolism)
  • Intraabdominal Infections (microbiology, pathology)
  • Male
  • Microbial Viability
  • RNA, Bacterial (genetics)
  • RNA, Messenger (genetics, metabolism)
  • Rats
  • Rats, Sprague-Dawley
  • Real-Time Polymerase Chain Reaction
  • Transcription, Genetic

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