How to Interpret a Positive Campylobacter PCR Result Using the BD MAXTM System in the Absence of Positive Culture?

Thomas Gueudet,Alice Buissonnière,Francis Mégraud,Lucie Bénéjat,Jean Marc Rousée,Astrid Ducournau,Marie Carole Paolini,Philippe Lehours,Emilie Bessède,Anne Trens,Matthieu Lefranc

doi:10.3390/jcm8122138

Thomas Gueudet, Alice Buissonnière + Show 9 more

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https://doi.org/10.3390/jcm8122138

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Abstract

The aim of this study was to evaluate, using two independent polymerase chain reaction (PCR) formats, the results of Campylobacter detection by the BD MAXTM Enteric Bacterial Panel PCR (Becton Dickinson, Le Pont de Claix, France) in the absence of positive culture. A total of 77 samples found positive for Campylobacter on BD MAXTM but negative by culture were studied. Upon reception, one in-house real-time-PCR for Campylobacter sp. and a PCR with the RIDAGENE Bacterial Stool Panel (r-biopharm, Darmstadt, Germany) were performed. The data obtained using these two PCR formats were evaluated with respect to the cycle threshold (Ct) and fluorescence intensity values (FI) obtained on BD MAXTM. Ct and FI values were also obtained for 80 positive Campylobacter cases by culture. Among the 77 samples, 33 were positive with the two PCRs, and 37 remained negative. For the 33 double-positive PCRs samples, the Ct values obtained on BD MAXTM were lower than 30 in 93.9%, and FI > 2000 for 97% of cases. For the 37 double-negative PCRs samples, the Ct values obtained on BD MAXTM were <30 in only 18.9%, however FI were >2000 for 40.5% of cases. Positive culture cases had Ct values < 30 in 96.2% and FI > 2000 in 98.8%. We showed that the Ct values obtained on BD MAXTM can help to interpret the results. Almost 96% of the Campylobacter sp. cases detected by culture or with the two reference PCRs positive showed a Ct value on BD MAXTM, meaning that stools detected as positive with BD MAXTM and having a Ct > 30 may be false positives.

Highlights

Campylobacters are among the most prevalent bacteria involved in acute diarrhea [1]
The two laboratories sent 77 samples to the National Reference Center for Campylobacters and Helicobacters (NRCCH) (53 Cary Blair transport medium tubes previously inoculated with rectal swabs received from Bio67 and 24 stools from CBM25) that were found positive for Campylobacter sp. on BD MAXTM but negative by culture
During the time periods considered, the ratio of positive Campylobacter sp. to positive polymerase chain reaction (PCR) versus Salmonella sp. was 423/7 and 227/13 for Bio67 and CMB25, respectively. These results confirm the wide prevalence of Campylobacter sp. in acute community infectious diarrhea

Summary

Introduction

Campylobacters are among the most prevalent bacteria involved in acute diarrhea [1]. The culture of Campylobacter sp. can be falsely negative in 10% to 30% of cases [2] due to preanalytical and analytical factors. The French National Reference Center for Campylobacters and Helicobacters (NRCCH) set up a collaboration with two diagnostic laboratories participating in its surveillance network, located in the French departments 25 (Doubs) (Laboratory CBM25) and 67 (Bas-Rhin) (Laboratory Bio67), using the BD MAXTM Enteric Bacterial Panel PCR (Becton Dickinson, Le Pont de Claix, France) as a screening method before culture. These two laboratories perform Campylobacter culture only on stools that are detected positive on the BD MAXTM, leading to a negative culture in a few cases. The objective of the study was to verify the positive Campylobacter sp. status of the stools negative by culture for the period from 4 January to 23 August 2018 and from 18 December 2017 to 30 June 2018 for Laboratories CBM25 and Bio, respectively

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