title: 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.
authors: Department of Microbiology and Immunology, East Carolina University Brody School of Medicine, Greenville, North Carolina 27834, USA.
authors: Leandro A
authors: LA
authors: Lobo
authors: Audrey L
authors: AL
authors: Jenkins
authors: C
authors: C
authors: Jeffrey Smith
authors: Edson R
authors: ER
authors: Rocha
mesh_terms: D018784:Abdominal Abscess / Q000382:microbiology / Q000473:pathology; D000818:Animals; D058491:Bacterial Load; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001441:Bacteroides fragilis / Q000235:genetics* / Q000472:pathogenicity; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism*; D059413:Intraabdominal Infections / Q000382:microbiology* / Q000473:pathology; D008297:Male; D050296:Microbial Viability; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D006460:Hemolysin Proteins; C050837:Hlyb protein, Bacteria; D012329:RNA, Bacterial; D012333:RNA, Messenger