A study of the epidemiology, phenotypic and genotypic characteristics of Guillain Barre syndrome associated campylobacteriosis

Guillain-Barre syndrome (GBS) is a neurological disease characterised by ascending paralysis that can lead to respiratory muscle compromise and death. Although the exact trigger of GBS is unknown, case control studies have shown that it often follows an acute infectious illness. In recent years, serological and cultural studies have suggested that Campylobacterjejuni is the infectious agent most commonly associated with the development of GBS. Culture confirmation of C. jejuni infections has been achieved in up to 50% of GBS patients, in spite of the fact that many GBS patients with antecedent Campylobacter infection are likely to have already cleared their stools of the organism by the time neurological symptoms begin. Campylobacter infection is now classified as the most common cause of bacterial food poisoning in the Western world. In Tasmania, over 400 cases are notified each year. Given this prevalence it is not clear why only a small number of patients with C. jejuni enteritis develop GBS whilst the majority do not. Two possibilities exist; the first being that susceptibility is determined by host-specific factors; the second is that bacterial strain-specific factors determine whether patients develop GBS. The aim of this investigation is to determine the importance of the second factor. The specific objectives being to define specific bacterial markers that might be used to determine those strains of Campylobacter associated with the development of GBS. The way in which infection with C. jejuni leads to GBS is unknown, however, there is evidence suggesting that Gml ganglioside in the core of the lipopolysaccharide of certain strains of C. jejuni may stimulate an immune response to this epitope in infected patients. It is hypothesized that this immune response may then lead to an autoimmune peripheral neuropathy because the Gml in the bacteria is identical to that in the nerve cell. This study investigated the epidemiology of Campylobacter infection within the Tasmanian community by collecting isolates from patients notified to the Department of Health in Tasmania. This culture collection was then used to develop a robust method for speciation of isolates. This included development of a multiplex PCR for the hippurate gene/16S rRNA gene with subsequent dot blot hybridisation using labeled probes. Using this system, 237 enteritis strains were identified as C. jejuni, 10 C. co/i, 2 C. lari and 1 C. upsaliensis. C. jejuni serotype 0:19 appears to be over-represented in most published studies of GBS but campylobacters of this serotype do not account for all Campylobacter isolates from GBS patients. Potential markers of GBS-associated campylobacters investigated in the present study included the use of a Cholera Toxin Binding Assay for Gml -like epitopes in bacteria cell walls, a PCR for serotype 0:19 strains and Pulsed Field Gel Electrophoresis (PFGE). While 33% of all Tasmanian strains were found to be Gml positive, no isolates were found to belong to the serotype 0:19. Further, computer-assisted analysis of PFGE profiles showed no similarity between GBS strains of C. jejuni and Tasmanian strains of Campylobacter. Subtractive hybridisation was used to produce a DNA library containing sequences that are over-represented in GBS-associated strains of C. jejuni. This library has been used to screen GBS and non-GBS-associated strains of C. jejuni. A unique DNA sequence, present only in the GBS-associated strains, has been identified and a PCR-based assay developed to detect this gene (Veh). The gene has homology to a sequence (Cj1013c), determined as part of the recently completed C. jejuni genome sequencing project, which is a gene of unknown function. Further studies to define gene function have been hampered by the lack of a suitable mutagenesis system for C. jejuni. Veh has been cloned in a shuttle vector to enable its mobilisation into other transfer systems. It is hoped that in the future, identification of Campylobacter strains containing the Veh gene will lead to prompt treatment of patients infected with these strains thereby decreasing the incidence of GBS and its associated morbidity and mortality.