POLYMERASE CHAIN-REACTION FOR SCREENING CLINICAL ISOLATES OF CORYNEBACTERIA FOR THE PRODUCTION OF DIPHTHERIA-TOXIN

Aims-To assess the performance of the polymerase chain reaction (PCR) when used to screen rapidly large numbers of corynebacteria for toxin production; and to determine the incidence of false positive PCR results with non-toxigenic Corynebacterium diphtheriae isolates. Methods-Eighty seven recent British isolates of corynebacteria were assayed by PCR. All isolates were assayed from both blood and tellurite agar within a five day period. Thirty three non-toxigenic isolates of C diphtheriae from six countries were also tested by PCR and by the Elek immunodiffusion assay. Results-There was complete concordance between the results of PCR and traditional methods on the recent British isolates, with one exception: an Elek positive ''C ulcerans'' isolate, which was PCR positive from tellurite but not from blood agar. One of the thirty three (3%) nontoxigenic isolates of C diphtheriae was PCR positive. Conclusions-These results suggest that PCR compares favourably with traditional methods for the detection of toxigenic corynebacteria and that it represents a powerful new tool in the diagnosis of an old disease.