Highly Pathogenic Clone of

Twenty-five cases of nontoxigenic Corynebacte-rium diphtheriae infection were recorded in Poland during 2004–2012, of which 18 were invasive. Alcoholism, home-lessness, hepatic cirrhosis, and dental caries were predis-posing factors for infection. However, for 17 % of cases, no concomitant diseases or predisposing factors were found. Corynebacterium diphtheriae is the causative agent of diphtheria. Its toxin is considered the major virulence factor. Since introduction of vaccine against the diphtheria toxin in the 1940s, infections caused by toxigenic coryne-bacteria have been well controlled in industrialized coun-tries that have high coverage rates of childhood vaccination with 3 doses of diphtheria-tetanus-pertussis vaccine (1). Nevertheless, emergence of nontoxigenic C. diphtheriae infections has been reported in some of these countries. In line with other European countries, Poland routinel