Molecular and Epidemiological Review of Toxigenic Diphtheria Infections in England between 2007 and 2013

Abstract

Human infections caused by toxigenic corynebacteria occur sporadically across Europe. In this report, we undertook the epidemiological and molecular characterization of all toxigenic corynebacterium strains isolated in England between January 2007 and December 2013. Epidemiological aspects include case demographics, risk factors, clinical presentation, treatment, and outcome. Molecular characterization was performed using multilocus sequence typing (MLST) alongside traditional phenotypic methods. In total, there were 20 cases of toxigenic corynebacteria; 12 (60.0%) were caused byCorynebacterium ulcerans, where animal contact was the predominant risk factor. The remaining eight (40.0%) were caused byCorynebacterium diphtheriaestrains; six were biovar mitis, which were associated with recent travel abroad. Adults 45 years and older were particularly affected (55.0%; 11/20), and typical symptoms included sore throat and fever. Respiratory diphtheria with the absence of a pharyngeal membrane was the most common presentation (50.0%; 10/20). None of the eightC. diphtheriaecases were fully immunized. Diphtheria antitoxin was issued in two (9.5%) cases; both survived. Two (9.5%) cases died, one due to aC. diphtheriaeinfection and one due toC. ulcerans. MLST demonstrated that the majority (87.5%; 7/8) ofC. diphtheriaestrains represented new sequence types (STs). By adapting several primer sequences, the MLST genes inC. ulceranswere also amplified, thereby providing the basis for extension of the MLST scheme, which is currently restricted toC. diphtheriae. Despite high population immunity, occasional toxigenic corynebacterium strains are identified in England and continued surveillance is required.