method comparison for enhanced recovery, isolation and qualitative detection of c. jejuni and c. coli from wastewater effluent samples

Seeking a sensitive protocol, culture-dependent methods were compared to detect thermophilic Campylobacter species in untreated urban effluents. We evaluated various combinations of selective media, with and without an enrichment steps, as well as an extra filtration step. Culture-independent real-time quantitative PCR was also included and all detected isolates underwent antimicrobial susceptibility testing. All tested water samples contained Campylobacter DNA, but only 64% were positive after culture. Although enrichment using Preston broth resulted in better recovery of potentially stressed Campylobacter than Bolton or Campyfood broth (CFB), there was no significant increase in efficiency compared to direct plating. The type of selective agar media used, on the other hand, had a significant effect, with CASA plates performing better than mCCDA or CFA ones. Inclusion of an enrichment step increased the ratio of C. coli vs. C. jejuni being isolated. Resistances against all antimicrobials tested were observed in C. coli, but fewer instances of resistance were found in C. jejuni isolates. Whether this difference was the result of selection during the enrichment step could not be determined. The presence of Campylobacter in urban effluents can be considered as a valuable proxy for Campylobacter populations present in urban environments.