Comparison of molecular typing methods useful for detecting clusters of Campylobacter jejuni and C. coli isolates through routine surveillance

Abstract

Campylobacter spp. may be responsible for unreported outbreaks of food-borne disease. The detection of these outbreaks is made more difficult by the fact that appropriate methods for detecting clusters of Campylobacter have not been well defined. We have compared the characteristics of five molecular typing methods on Campylobacter jejuni and C. coli isolates obtained from human and nonhuman sources during sentinel site surveillance during a 3-year period. Comparative genomic fingerprinting (CGF) appears to be one of the optimal methods for the detection of clusters of cases, and it could be supplemented by the sequencing of the flaA gene short variable region (flaA SVR sequence typing), with or without subsequent multilocus sequence typing (MLST). Different methods may be optimal for uncovering different aspects of source attribution. Finally, the use of several different molecular typing or analysis methods for comparing individuals within a population reveals much more about that population than a single method. Similarly, comparing several different typing methods reveals a great deal about differences in how the methods group individuals within the population.

Fig 1

Comparison of the global congruence (Wallace coefficient [95% confidence interval]) of methods with PFGE included for a subset of 152 isolates. Wi, expected Wallace coefficient value in the case of independence. The first column of the table represents the primary typing method, and the remainder of the row shows the secondary typing methods to which the primary method is compared. Colors were assigned by the program on the Comparing Partitions website as a range through complete congruence (dark blue), high congruence (lighter blue), moderate congruence (green and yellow-green), low congruence (brown and red-brown), and almost no congruence (red).