Phage typing, an accessible and useful method in the epidemiological surveillance of diphtheria.

Within the framework of the measures for diphtheria prevention and control, phage typing of isolates is useful for epidemiological investigations in a disease focus and in general population. The identification of asymptomatic carriers of toxigenic C.diphtheriae and its eradication decrease the transmission rate of the disease. The study of the circulating phage types (6058) enabled us to demonstrate the frequency and distribution of the different phage types, toxigenic and nontoxigenic in Romania. With the current knowledge of the circulating phage types it can be concluded that imported cases of diphtheria have not occurred so far. The Romanian phage typing schemes are able to type isolates from overseas, sometimes through phage adaptation methods. Our phage typing schemes are also able to demonstrate any modifications in the phage sensitivity patterns of diphtheria.