pVir and bloody diarrhea in Campylobacter jejuni enteritis

Emerging Infectious Diseases, June, 2005 by Dobryan M. Tracz, Monika Keelan, Jasmine Ahmed-Bentley, Amera Gibreel, Kinga Kowalewska-Grochowska, Diane E. Taylor

Plasmid Content

Tetracycline-resistance plasmids were found in 50 (79%) of 63 tetracycline-resistant isolates. DNA-DNA hybridizations for the cjp5 gene on pVir determined that 18 (17%) of 104 C. jejuni isolates contained the pVir plasmid. Stocked frozen clinical isolates had a slightly higher frequency of pVir than fresh clinical isolates (18% vs. 13%, respectively), most likely because of sampling error. Tetracycline-resistance plasmids were found in 17 (94%) of 18 pVir-positive C. jejuni isolates compared with 33 (38%) of 86 pVir-negative isolates. The presence of pVir plasmids was associated with the presence of tetracycline-resistance plasmids (p<0.00001). Alternatively, 33 (66%) of the 50 isolates that contained tetracycline-resistance plasmids did not contain pVir, demonstrating that plasmid-mediated tetracycline resistance does not occur exclusively with pVir.

Relationship of Signs and Symptoms to Plasmid Content

Pain, diarrhea, vomiting, and fever were equally likely to occur in all C. jejuni infections, regardless of the presence of pVir (Table 2). However, 53% of patients infected with pVir-positive C. jejuni strains had bloody stool, as opposed to 21% of patients infected with pVir-negative C. jejuni strains (p = 0.011). pVir was not associated with age, sex, antimicrobial therapy, coexisting conditions, or travel. The patient with campylobacteremia and febrile seizures was infected with a pVir-negative C. jejuni. None of the patients infected with pVir-positive C. jejuni strains had a history of travel outside of Alberta in the week preceding the illness, and all of the patients who traveled outside of Alberta were infected with pVir-negative C. jejuni strains.

Transfer of Plasmids between C. jejuni Strains

Tetracycline-resistant transconjugants contained [approximately equal to] 40-kb plasmids that carried tet(O) but were negative for pVir in DNA-DNA hybridizations with the cjp5 probe (data not shown). This finding confirmed the finding of Bacon et al. (15) that pVir could not be transferred with tetracycline-resistance plasmids in conjugal mating between C. jejuni strains.

Discussion

The role of pVir in human C. jejuni infections has not been investigated previously. Bacon et al. (15,16) presented evidence for the role of pVir in the virulence of C. jejuni based on in vitro cell-culture experiments and limited animal data with the ferret model (15). In our study, symptoms associated with C. jejuni infection were correlated with the presence or absence of pVir plasmids. Symptoms varied from mild discomfort to severe cases with bloody diarrhea. Travel and coexisting medical conditions were not predictors of severity of C. jejuni infections and were not associated with a higher frequency of blood in the stool or pVir-positive C. jejuni infections. Although the pVir virulence plasmid did not correlate with most clinical symptoms, patients infected with a pVir-positive C. jejuni strain were more likely to produce bloody stool than those infected with a pVir-negative strain. The time course of the disease may have affected whether or not blood was observed in the stool sample. The clinical data collected reflect both the observations of the patient as reported to the physician and the physician's records. Accordingly, these conclusions are based upon the necessary limitations of this retrospective study of patients from different unconnected study sites within a region, with perhaps some differences in diagnostic definitions.