Comparison of SmaI-defined genotypes of Campylobacter jejuni examined by KpnI: a population-based study

Pulsed-field gel electrophoresis (PFGE) was used to analyse 147 isolates co llected in two regions of Quebec province (Estrie and Montreal) between Mar ch 1998 and Feb. 1999, to determine the utility of molecular strain typing for a population-based collection of Campylobacter jejuni and to compare di rectly the discriminatory power of SmaI and KpnI restriction digests. With a combination of epidemiological criteria including space and time plus mol ecular strain typing, 49% of isolates from Estrie and 39% of isolates from Montreal were identified as belonging to a putative cluster. For 41% of the cases, sources were either missing or explicitly unknown; the remaining so urces were subject to recall bias. Thus, the evaluation of sporadic cases o f campylobacter enteritis by descriptive clinical investigation alone is ne ither sensitive nor reliable for identifying sources of infection. In the P FGE analysis, KpnI digests provided appreciably greater discriminatory powe r than SmaI digests. When combining the PFGE analyses with basic epidemiolo gical criteria, 30% of the putative Sinal clusters were inconsistent with t he epidemiological criteria compared with 17% of the KpnI clusters. Among t he 98 isolates assigned to clusters by SmaI, only 65% gave concordant resul ts with KpnI. In contrast, among the 81 isolates assigned to clusters by Kp nI, 92% gave concordant results with Sinal. Finally, clusters that were epi demiologically related to ingestion of raw milk and specific water sources correlated better with the typing results based on KpnI than SmaI. Thus, Kp nI is the enzyme of choice for molecular epidemiology studies of C. jejuni. The combination of continuous epidemiological surveillance and molecular s train typing may be useful for identifying new sources and mechanisms of tr ansmission for community-acquired C jejuni infection and ultimately for dev eloping new approaches to prevention.