Outbreak of Corynebacterium pseudodiphtheriticum Infection in Cystic Fibrosis Patients, France - EID - CDC Volume 16, Number 8–August 2010

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Volume 16, Number 8–August 2010
Research
Outbreak of Corynebacterium pseudodiphtheriticum Infection in Cystic Fibrosis Patients, France
Fadi Bittar,1 Carole Cassagne,1 Emmanuelle Bosdure, Nathalie Stremler, Jean-Christophe Dubus, Jacques Sarles, Martine Reynaud-Gaubert, Didier Raoult, and Jean-Marc Rolain
Author affiliations: Université de la Méditerranée, Marseille, France (F. Bittar, C. Cassagne, D. Raoult, J.-M. Rolain); Hôpital Timone, Marseille (E. Bosdure, N. Stremler, J.-C. Dubus, J. Sarles); and Hôpital Sainte-Marguerite, Marseille (M. Reynaud-Gaubert)

Suggested citation for this article

Abstract
An increasing body of evidence indicates that nondiphtheria corynebacteria may be responsible for respiratory tract infections. We report an outbreak of Corynebacterium pseudodiphtheriticum infection in children with cystic fibrosis (CF). To identify 18 C. pseudodiphtheriticum strains isolated from 13 French children with CF, we used molecular methods (partial rpoB gene sequencing) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry. Clinical symptoms were exhibited by 10 children (76.9%), including cough, rhinitis, and lung exacerbations. The results of MALDI-TOF identification matched perfectly with those obtained from molecular identification. Retrospective analysis of sputum specimens by using specific real-time PCR showed that ≈20% of children with CF were colonized with these bacteria, whereas children who did not have CF had negative test results. Our study reemphasizes the conclusion that correctly identifying bacteria at the species level facilitates detection of an outbreak of new or emerging infections in humans.

Cystic fibrosis (CF) is an autosomal recessive disease characterized by defective ion channels, resulting in multiorgan dysfunction, most notably affecting the respiratory tract. The alteration in pulmonary environment is associated with increased susceptibility to bacterial infections (1,2). These bacterial infections and the ensuing inflammation damage the airway epithelium and cause recurrent episodes of acute exacerbations, leading ultimately to respiratory failure. Respiratory infections account for 80%–90% of deaths of patients with CF (2). Recent advances in bacterial taxonomy and improved microbial identification methods have led to increasing recognition of the complexity of microbial ecology of the CF lung (3–5). Thus, infections of the lung in patients with CF are now considered as polymicrobial infections. In addition to well recognized CF pathogens(e.g., Staphylococcus aureus,Pseudomonas aeruginosa,Haemophilus influenzae, and Burkholderia cepacia complex) numerous other opportunistic bacteria have been recently reported, such as Stenotrophomonas maltophila,Achromobacter xylosoxydans, and Inquilinus limosus and methicillin-resistant S. aureus and mucoid P. aeruginosa (1,2,6–8).

The first difficulty in studying infections in the lungs of patients with CF is that many bacteria present in the lung cannot be isolated from sputum samples either because of their fastidious growth requirements or because of the presence of other more common CF-related pathogens, including P. aeruginosa,S. aureus,H. influenzae, and Branhamella catarrhalis, that might ordinarily overgrow other bacteria in culture. Second, correct identification of bacteria in patients with CF remains challenging because phenotype variation is a common feature during chronic infection of the lung (4,9). Consequently, the list of bacteria that can be recovered from sputum specimens of patients with CF may be underestimated, and new or emerging bacteria that could be responsible for outbreaks in this population are not easily detected. Correct identification of these bacteria is not easily achieved.

Several studies have reported the use of matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry as a powerful tool with good and reproducible results for rapid identification of clinical isolates in the microbiology laboratory (10) as well as for identifying nonfermenting gram-negative bacteria in patients with CF (11–13). This method is simple, rapid, easy to perform, inexpensive, and may ultimately replace routine phenotypic assays (10).

We report the clinical and microbiologic features of patients with CF who were infected or colonized by C. pseudodiphtheriticum. The index case-patient was a 9-year-old girl with fever and cough; a coryneform bacterium was isolated in pure culture from her sputum. After this first case, several other children with CF were found to be infected by coryneform bacteria; thus, we decided to investigate the possibility of an endemic transmission in this population. Isolated strains were identified by using existing phenotypic and molecular methods (14) as well as MALDI-TOF to decipher the relationship between these strains. Finally, a new real-time PCR with TaqMan probe (Applied Biosystems, Courtaboeuf, France) was developed and used in a retrospective analysis to detect these coryneform bacteria in our population with CF.

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Suggested Citation for this Article
Bittar F, Cassange C, Bosdure E, Stremler N, Dubs J-C, Sarles J, et al. Outbreak of Corynebacterium pseudodiphtheriticum infection in cystic fibrosis patients, France. Emerg Infect Dis [serial on the Internet]. 2010 Aug [date cited]. http://www.cdc.gov/EID/content/16/8/1231.htm

DOI: 10.3201/eid1608.100193

1These authors contributed equally to this article.