Clinical and microbiological characteristics of patients with bacteremia caused by Campylobacter species with an emphasis on the subspecies of C. fetus

Abstract

Objectives: This study was intended to investigate the clinical and microbiological characteristics of patients with bacteremia caused by Campylobacter species.

Methods: From April 1998 to May 2014, 56 adults with bacteremia caused by Campylobacter species were evaluated. These Campylobacter species isolates were confirmed to the species level using 16S rRNA gene sequencing (all isolates) and multiplex PCR analysis (for C. fetus only). The performance of identification for Campylobacter species by the Bruker Biotyper MALDI-TOF MS was evaluated. The genetic relatedness of C. fetus isolates was analyzed by multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE).

Results: The leading underlying medical conditions of these patients were malignancy (46.4%), hypertension (35.7%), and liver cirrhosis (23.2%). The overall 30-day mortality rate was 5.4%. Using 16S rRNA sequencing analysis, 26 isolates of C. coli, 11 of C. jejuni, and 19 of C. fetus, including 15 C. fetus subsp. fetus and five C. fetus subsp. venerealis, were identified. Among the five C. fetus subsp. venerealis isolates recognized by 16S rRNA gene sequencing, only two isolates were C. fetus subsp. venerealis by multiplex PCR method. The Bruker Biotyper MALDI-TOF MS failed to correctly identify C. fetus subsp. venerealis isolates. MLST analysis of C. fetus isolates revealed three STs: ST20 (n = 12), ST11 (n = 5), and ST57 (n = 2), which were compatible with three major PFGE clusters.

Conclusion: Database expansion of MALDI-TOF MS for the correct identification of C. fetus to subspecies levels is needed. A novel clone of ST57-PFGE Cluster C of C. fetus subsp. venerealis was noted.

Keywords: 16S RNA gene sequencing; API Campy system; Bruker Biotyper MALDI-TOF MS; Campylobacter; Campylobacter fetus; Multiplex PCR.