Investigation of identification methods for Campylobacter spp.

Abstract

Representative species of Campylobacter include Campylobacter jejuni, Campylobacter coli, and Campylobacter fetus. We experience a case that it has been detected C. fetus from culture of diarrhea stool at 42°C in a microaerobic condition. So, to investigate the identification of Campylobacter spp., we performed PCR as golden standard, growth tests at 25°C and 42°C, hippurate hydrolysis tests, and indoxyl acetate hydrolysis tests using 66 strains of Campylobacter spp. In the growth tests, all strains grew at 42°C, and only 6 strains of C. fetus grew at 25°C. The hippurate hydrolysis test was performed at the observation time of 15 minutes (manufacture’s insertion) and 60 minutes, and the sensitivity was 55.6% (20/36) and 88.9% (32/36), respectively. And there were no false positives when the test was extended to 60 minutes. There were no false positives in the indoxyl acetate hydrolysis test, and the sensitivity was 98.3% (59/60). The agreement rate between the PCR method and the biochemical property tests (using observation time 60 min for the hippurate hydrolysis test) was 93.9% (62/66). For the identification of Campylobacter spp., it was shown that many Campylobacter fetus subsp. fetus can grow at 42°C, that the observation time of the hippuric acid hydrolysis test needs to be extended up to at least 60 min, and that the indoxyl acetate hydrolysis test is a useful auxiliary test.