Corynebacterium species nasopharyngeal carriage in asymptomatic individuals aged ≥ 65 years in Germany
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The prevalence of protective anti-diphtheria toxin antibodies decreases with age. Therefore, the elderly might serve as reservoir for potentially toxigenic Corynebacterium (C.) species (C. diphtheriae, C. ulcerans, and C. pseudotuberculosis). This study aimed to examine the colonization rate of the nasopharynx with corynebacteria of individuals aged 65 years and older.
In the period from October 2012 to June 2013, nasal and throat swabs were taken from 714 asymptomatic subjects aged 65–106 years (average age 77.2) at three regions in Germany and investigated for Corynebacterium species.
A total of 402 strains of Corynebacterium species were isolated from 388 out of 714 asymptomatic subjects (carriage rate 54.3%). The carriage rate was significantly higher in study participants living in retirement homes (68.4%) compared to those living autonomously at home (51.1%). Strains were isolated mostly from the nose (99%). Corynebacterium accolens was the most often isolated species (39.8%), followed by C. propinquum (24.1%), C. pseudodiphtheriticum (19.4%), and C. tuberculostearicum (10.2%). No C. diphtheriae, C. ulcerans, and C. pseudotuberculosis strains were isolated. A subsample of 74 subjects was tested serologically for anti-diphtheria antibodies. Protective anti-diphtheria toxin antibodies were found in 29.7% of the subjects; 70.3% showed no protective immunity.
These results suggest that carriage of potentially toxigenic corynebacteria is very rare among people aged 65 and older in Germany. However, the low prevalence of protective anti-diphtheria toxin antibodies might pose a risk for acquiring diphtheria especially for the elderly.
KeywordsDiphtheria Corynebacterium species Nasopharyngeal carriage Age Anti-diphtheria toxin antibodies
We would like to thank the elderly people who volunteered to participate in this study and the institutions of the elderly for their support. We thank Wolfgang Schmidt, Turgut-Cengiz Dedeoglu, Annegret Mahl and Jasmin Fräßdorf for excellent technical and Dr. Angelika Torka for expert medical support. The study was supported by the German Federal Ministry of Health via the Robert Koch Institute and its National Reference Laboratories Network (FKZ 415).
Compliance with ethical standards
The study has been approved by the responsible human subjects’ research ethical review board at the University of Würzburg (no. 150/11). All participants gave their informed consent prior to their inclusion in this study.
Conflict of interest
On behalf of all authors, the corresponding author states that there is no conflict of interest.
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