Temperate bacteriophages affect pulsed-field gel electrophoresis patterns of Campylobacter jejuni

Abstract

The recently sequenced genome of Campylobacter jejuni RM1221 revealed the presence of three integrated bacteriophage-like elements. In this study, genes from the first element, a Mu-like bacteriophage, were amplified by PCR and used to probe pulsed-field gels of clinical C. jejuni strains obtained from a waterborne outbreak (Ontario, Canada, 2000). These highly similar strains differed only by their pulsed-field gel electrophoresis (PFGE) patterns due to an apparent insertion or deletion of a 40-kb fragment. Bacteriophage probes hybridized to these different bands in Southern blot analysis, indicating that homologues of bacteriophage genes were present in the outbreak strains. Investigation of the bacteriophage insertion sites in these isolates suggested that bacteriophage acquisition, loss, or transposition was responsible for the PFGE pattern variation. The bacteriophage gene sequences were similar, but not identical, in the outbreak strains and RM1221, indicating that differences may exist between the bacteriophages.

FIG. 1.

PFGE gel and Southern hybridization of highly related C. jejuni strains isolated from a waterborne outbreak. PFGE was performed with SmaI-digested DNA, and Southern hybridization was performed with a probe directed toward Cje0270, a gene that encodes a putative bacteriophage DNA transposition protein A in RM1221. The different bands in the PFGE gel are numbered 1 to 5. (A) Results of PFGE and Southern blot analysis for isolates 00-2426 and 00-2425; (B) results of PFGE and Southern blot analysis for isolates 00-2426, 00-2544, and 00-2856.

FIG. 2.

PCR analyses of bacteriophage insertion sites in C. jejuni outbreak isolates. The isolates tested, the primers used, and the amplicon sizes are listed above, to the left, and to the right of the agarose gel images, respectively. Additional primer characteristics are described in Table 2. All amplicons were electrophoresed on 1.5% agarose gels at 100 V. NTC, no-template control.