Expression of Bacteroides fragilis hemolysins in vivo and role of HlyBA in an intra‐abdominal infection model. Issue 2 (26th February 2013)

• Record Type: Journal Article
• Authors: Lobo, Leandro A.; Jenkins, Audrey L.; Jeffrey Smith, C.; Rocha, Edson R.
• Is Part Of: MicrobiologyOpen. Volume 2:Issue 2(2013:Apr.)
• Page Start: 326
• Page End: 337
• Publication Date: 2013-02-26
• Subjects: Microbiology -- Periodicals; 579
• DOI: 10.1002/mbo3.76
• Languages: English
• ISSNs: 2045-8827

Abstract

<abstract abstract-type="main" xml:lang="en" id="mbo376-abs-0001"> <title>Abstract</title> <p> <italic>Bacteroides fragilis</italic> 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 <italic>B. fragilis</italic> 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 <italic>hlyA</italic>, <italic>hlyB</italic>, <italic>hlyC</italic>, <italic>hlyD</italic>, <italic>hlyE</italic>, <italic>hlyF</italic>, <italic>hlyG</italic>, and <italic>hlyIII</italic> mRNAs. The <italic>hlyA</italic> mRNA was induced approximately sixfold after 4 days postinfection compared with the mRNA levels in the inoculum culture prior to infection. The <italic>hlyB</italic> mRNA increased approximately sixfold after 4 days and 12‐fold after 8 days postinfection. Expression of <italic>hlyC</italic> mRNA increased sixfold after 1 day, 45‐fold after 4 days, and 16‐fold after 8 days postinfection, respectively. The <italic>hlyD</italic> and <italic>hlyE</italic> mRNAs were induced approximately 40‐fold and 30‐fold, respectively, after 4‐days postinfection. The <italic>hlyF</italic> expression increased approximately threefold after 4‐days postinfection. <italic>hlyG</italic> was induced approximately fivefold after 4 and 8 days postinfection. The <italic>hlyIII</italic> 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 <italic>B. fragilis</italic> hemolysins are induced and differentially regulated in vivo. Both parent and <italic>hlyBA</italic> mutant strains reached levels of approximately 3–8 × 10<sup>9</sup> cfu/mL after 1 day postinfection. However, the <italic>hlyBA</italic> 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 <italic>B. fragilis</italic> survival in an intra‐abdominal abscess model.</p> </abstract>