Importance of toxin A, toxin B, and CDT in virulence of an epidemic Clostridium difficile strain.

Sarah A Kuehne,Michelle L Kelly,Stephen T Cartman,Mark M Collery,Nigel P Minton,Alan Cockayne

doi:10.1093/infdis/jit426

Abstract

Clostridium difficile infection is the main cause of healthcare-acquired diarrhea in the developed world. In addition to the main virulence factors toxin A and B, epidemic, PCR Ribotype 027 strains, such as R20291, produce a third toxin, CDT. To develop effective medical countermeasures, it is important to understand the importance of each toxin. Accordingly, we created all possible combinations of isogenic toxin mutants of R20291 and assessed their virulence. We demonstrated that either toxin A or toxin B alone can cause fulminant disease in the hamster infection model and present tantalizing data that C. difficile toxin may also contribute to virulence.

Highlights

Clostridium difficile infection is the main cause of healthcareacquired diarrhea in the developed world
2 independent studies have investigated the relative role of toxins A and B in virulence through the creation of isogenic toxin mutants and their analysis in the hamster infection model
It has been suggested that this apparent paradox could be resolved by the examination of other strains [4], polymerase chain reaction (PCR) ribotype 027 epidemic strains, that are associated with more severe disease, higher relapse rates, increased mortality, and greater resistance to fluoroquinolone antibiotics [5]

Summary

Introduction

Clostridium difficile infection is the main cause of healthcareacquired diarrhea in the developed world. With respect to toxin A, conflicting results were obtained: one study demonstrated that toxin A alone could not cause disease in hamsters, whereas the other showed that an equivalent mutant in the same animal model was virulent [2, 3]. In both cases, the mutants were generated in erythromycinsusceptible derivatives of strains 630. By use of in vitro assays, it has been shown that purified binary toxin mediates increased adherence of C. difficile to epithelial cells through the formation of protrusions [8] This suggests a role for binary toxin in adherence and colonization. We focused on the creation and testing of isogenic toxin mutants in the PCR ribotype 027 strain R20291, an isolate epidemic in the United Kingdom that was responsible for 2 outbreaks of CDI at the Stoke Mandeville hospital in 2003 and 2004

Objectives

Methods

Results