Objectives: The incidence of Clostridium difficile infection (CDI) may increase due to dissemination of epidemic strains but may be altered also by changes in the diagnostic practices without actual change in disease's burden. We aimed to examine the combined effect of these factors on the reported incidence of CDI in general hospitals (GH) in Israel.
Methods: The diagnostic practices were studied by a national survey of clinical laboratories, comparing the methodology before and after the application of the national guidelines in 2012. The molecular and microbiological characteristics of C. difficile isolates were studied in two selected centers (A & B) that had an increase in CDI incidence in 2012.
Results: 18 laboratories participated in the survey; half of them have fully implemented the guidelines that require use of PCR in undetermined cases. Overall, there has been an increase in the rate of rejected samples, whereas the rate of positive samples increased only in the group the used PCR. In center A, were the incidence of CDI increased constantly from 2006 to 2012 (prior to diagnostic modification), the epidemic clone BI/NAP1/027 was found in 47/61 (79%) of isolates. In center B, were the incidence declined in 2011 but increased in 2012-3 (following the application of PCR), the epidemic clone was present already in 2011 and was not the dominant strain. In both centers, BI/NAP1/027 isolates exhibited higher MIC of vancomycin and metronidazole, compared with other clones.
Conclusion: The increase in the incidence of CDI is explained in part by the introduction of highly-sensitive assays, but may also reflect local outbreaks caused by epidemic clones.
