Fred C. Tenover

Survey of plasmids and resistance factors in Campylobacter jejuni and Campylobacter coli.

A total of 688 isolates of Campylobacter jejuni and Campylobacter coli were screened for the presence of plasmid DNA by agarose gel electrophoresis and were tested for susceptibility to ampicillin, chloramphenicol, erythromycin, streptomycin, and tetracycline. Of the isolates examined, 32% were noted to harbor plasmid DNA, ranging in size from 2.0 to 162 kilobases. Only tetracycline resistance was noted to correlate with the presence of plasmids. Plasmids capable of transferring tetracycline resistance via conjugation ranged in size from 42 to 100 kilobases. The Bg/II and Bc/I restriction endonuclease profiles of 31 plasmids examined showed marked diversity in their banding patterns. Although a high degree of DNA-DNA homology was noted among the Campylobacter spp. plasmids, no homology was noted between these plasmids and tetracycline R factors commonly found in the family Enterobacteriaceae. Images

The Genera Campylobacter and Helicobacter

The genus Campylobacter encompasses a diverse group of organisms that are either cornmensals for pathogens for both humans and animals. Thirteen species are currently included in the genus (Table 1). The new genus Helicobacter contains two species previously classified as Campylobacter (Table 1). All of these organisms are Gram-negative, nonsporeforming, oxidase positive, indole negative, asaccharolytic organisms that neither ferment nor oxidize carbohydrates (Smibert 1978, 1984; Penner, 1988). Energy is produced through respiration and the metabolism of amino acids. The GC content for members of the genus falls between 29–39 mol% (Fox et al., 1989; Owen, 1983; Owen and Leaper, 1981; Harvey and Greenwood, 1983b; Ursing et al., 1983). All these organisms are slender, helically curved Gram-negative rods that are 0.2–0.5 μm wide and 0.5–8.0 μm long (Fig. 1). Pairs of cells have an S-shaped or gull-wing morphology while longer chains of cells form spirals. The shorter campylobacter forms move in a rapid, darting manner while spiral forms rotate along the long axis like corkscrews. The wavelength, amplitude, and length of the spirals vary among species. With the exceptions of Helicobacter pylori and H. mustelae,the organisms are motile by means of a long single, polar flagellum found at one or both ends of the cell (Smibert 1984). H. pylori has multiple flagella located at only one end of the cell while H. mustelae has both polar and lateral flagella (Fox et al., 1989).

Isolation of Plasmids Encoding Tetracycline Resistance from Campylobacter jejuni Strains Isolated from Simians

Fifteen isolates of tetracycline-resistant Campylobacter jejuni were recovered from stool samples of cynomologous monkeys (Macaca fascicularis) housed at the University of Washington Primate Research Center, Seattle. Resistance was associated with carriage of a 38-megadalton plasmid which was transmissible to other strains of C. jejuni but not to Escherichia coli. Seven isolates also contained a 2.6-megadalton plasmid which was phenotypically cryptic. Images