Comparison of Campylobacter isolates from poultry and humans: association between in vitro virulence properties, biotypes, and pulsed-field gel electrophoresis clusters

Abstract

The in vitro virulence properties of 197 temporally and geographically related Campylobacter isolates from chicken broilers and humans were compared. Comparisons of the virulence properties associated with genotypes and biotypes were made. All isolates adhered to, and 63% invaded, INT-407 cells, whereas 13% were cytotoxic for CHO cells. CHO cell-cytotoxic extracts were also cytotoxic for INT-407 cells, but the sensitivity for Vero cells was variable. The proportion of isolates demonstrating a high invasiveness potential (>1,000 CFU ml(-1)) or Vero cell cytotoxicity was significantly higher for human than for poultry isolates. Invasiveness was associated with Campylobacter jejuni isolates of biotypes 1 and 2, whereas CHO and INT-407 cell cytotoxicity was associated with C. jejuni isolates of biotypes 3 and 4. Cytotoxic isolates were also clustered according to pulsed-field gel electrophoresis profiles.

FIG. 1.

Representative portions of the PFGE KpnI dendrogram. The scale measured similarity values. Levels of similarity were calculated with the Dice coefficient, and the unweighted pair group method using arithmetical averages was used for cluster analysis. Human Campylobacter isolate numbers are preceded by H, and poultry isolates consist of numbers only. Each isolate number is followed by the biotype (CJ, C. jejuni; CC, C. coli) and, in parentheses, the PFGE KpnI genotype. Circles, isolates with an intracellular numbers >1,000 CFU ml⁻¹; triangles, CHO cell-cytotoxic isolates. Genotypes were delineated with a 90% similarity cutoff level.