Nontoxigenic Corynebacterium diphtheriae Isolated from Intravenous Drug Users

During a prospective study 117 intravenous drug users were screened for infection with Corynebacterium diphtheriae. Nontoxigenic C. diphtheriae was found in 5 of 132 throat swab specimens and in 5 of 28 skin ulcer specimens taken from July 1991 to April 1992. When phenotypic and molecular typing methods were used, these 10 strains were shown to belong to a single clone. During the same period no strain was isolated from 200 controls. Clinical manifestations of infection were not clearly attributable to C. diphtheriae—no typical membranous pharyngitis was present. The presence of a single clone among homeless intravenous drug users in Zurich indicates the presence of C. diphtheriae in parts of the population with poor standards of hygiene and low socioeconomic status.