Molecular characterization of invasive and noninvasive Campylobacter jejuni and Campylobacter coli isolates

Campylobacter jejuni is one of the most common causes of bacterial diarrhea worldwide and is the primary bacterial cause of food-borne illness. Adherence to and invasion of epithelial cells are the most important pathogenic mechanisms of Campylobacter diarrhea. Molecular characterization of invasive and noninvasive Campylobacter isolates from children with diarrhea and symptom-free children was performed by random amplified polymorphic DNA techniques (RAPD). A distinct RAPD profile with a DNA band of 1.6 kb was observed significantly more frequently among invasive (63%) than among noninvasive (16%) Campylobacter isolates (P = 0.000005). The 1.6-kb band was named the invasion-associated marker (IAM). Using specifically designed primers, a fragment of 518 bp of the iam locus was amplified in 85% of invasive and 20% of noninvasive strains (P = 0.0000000). Molecular typing with a PCR-restriction fragment length polymorphism assay which amplified the entire iam locus showed a HindIII restriction fragment polymorphism pattern associated mainly with invasive strains. Although cluster analysis of the RAPD fingerprinting showed genetic diversity among strains, two main clusters were identified. Cluster I comprised significantly more pathogenic and invasive isolates, while cluster II grouped the majority of nonpathogenic, noninvasive isolates. These data indicate that most of the invasive Campylobacter strains could be differentiated from noninvasive isolates by RAPD analysis and PCR using specific primers that amplify a fragment of the iam locus.

Hospital-acquired diarrhea in adults: a prospective case-controlled study in Mexico

OBJECTIVE

To know the incidence, etiology, risk factors, morbidity, and mortality of nosocomial diarrhea in adults.

DESIGN

Nested case-control study, matched by service, length of stay, date of admission, and presence of leukopenia and/or the acquired immunodeficiency syndrome (AIDS). Cases were those who developed nosocomial diarrhea. Controls were those who did not develop nosocomial diarrhea during a comparative period nor during the next ten days. Stool samples were processed in search for parasites, yeasts, bacteria, and rotavirus.

SETTING

Third-level referral center, in Mexico City, Mexico, for general internal medicine and surgical problems.

PATIENTS

Eligible subjects were all new admissions to the hospital from November 1987 to September 1988. Reasons for exclusion were presence of chronic diarrheal disease or melena. There were 115 cases and 111 controls.

RESULTS

Overall risk of acquiring nosocomial diarrhea was 5.5%, or 1.8 episodes per 100 patient-weeks. A potential pathogen was found in 59%. Yeasts and Entamoeba histolytica were the most frequently isolated pathogens. Mortality in cases was 18%, as compared with 5% in controls (p less than .01). Multivariate analysis showed enteral feeding, recent enemas, presence of Candida species, use of antacids/H2-blockers, and presence of nasogastric tubes as significant risk factors for nosocomial diarrhea.

CONCLUSIONS

Diarrhea is a common complication in hospitalized patients. It occurs more often than previously suspected and is linked with a substantial mortality. The spectrum of etiologic agents is different from that reported in pediatric hospitals. Given that nosocomial diarrhea may constitute, at least, a marker of severity of illness, it should receive more attention in general hospitals.

Adherence, enterotoxigenicity, invasiveness and serogroups in Campylobacter jejuni and Campylobacter coli strains from adult humans with acute enterocolitis

Two hundred Campylobacter jejuni and Campylobacter coli strains from the same number of adult Swedish patients with acute enterocolitis were tested regarding adherence to and invasiveness in HEp-2 cells and for enterotoxigenicity by the CHO-cell assay. The serogroup characteristics, heat-stable and heat-labile, for each strain were also investigated. Eighty-four percent of the strains were classified as C. jejuni and 16 percent as C. coli. All of the strains were adherent to HEp-2 cells, 39% were invasive and 31.5% enterotoxigenic. We found significantly more invasive strains in the non-enterotoxigenic group than in the enterotoxigenic one. There would seem to be no correlation between enterotoxigenicity or invasiveness and serogroup. The results of this study suggest the existence of multiple mechanisms for C. jejuni- and C. coli-induced diarrhoea and that the mechanisms may differ from one strain to another.