COMPARISON OF ARBITRARILY-PRIMED POLYMERASE CHAIN-REACTION, RESTRICTION ENZYME ANALYSIS AND PULSED-FIELD GEL-ELECTROPHORESIS FOR TYPING CLOSTRIDIUM-DIFFICILE

Three methods of molecular typing of Clostridium difficile [arbitraril y-primed polymerase chain reaction (AP-PCR), restriction enzyme analys is (REA) and pulsed-field gel electrophoresis (PFGE)] were compared us ing 33 isolates collected during a prospective study of Clostridium di fficile transmission. Sixteen isolates (from 13 patients and 3 environ mental sites) represented a cluster of C. difficile diarrhea on 2 ward s, whereas the other 17 isolates were from sporadic cases of C. diffic ile diarrhea or asymptomatically colonized patient contacts. Fourteen of the 16 clustered isolates were nontypable by pulsed-field gel elect rophoresis because of degradation. All 14 of these isolates were a sin gle strain by REA and AP-PCR; 7 of 17 nonclustered isolates also repre sented the same strain. The other 12 isolates (2 clustered; 10 nonclus tered) were subdivided into 9 subgroups by REA, 10 groups by AP-PCR an d 7 subgroups by pulsed-field gel electrophoresis. In one instance, AP -PCR resolved isolates indistinguishable by other methods into differe nt groups. However, the interpretation of AP-PCR patterns was complica ted by variable intensity of bands and lack of reproducibility of mino r bands. In conclusion, these 3 methods of genotyping yielded comparab le results, with AP-PCR showing somewhat greater discriminatory power but lower reproducibility.