COMMON SOMATIC-O AND HEAT-LABILE SEROTYPES AMONG CAMPYLOBACTER STRAINS FROM SPORADIC INFECTIONS IN THE UNITED-STATES

Somatic O (formerly heat-stable) and heat-labile (HL) serotyping metho ds are commonly used to type Campylobacter jejuni and Campylobacter co li isolates. Although both systems are effective, the labor and time r equired for each have limited their application. These systems can be simplified by reducing the number of antisera used. To find an appropr iate panel of antisera, we determined the distribution of common serot ypes in the United States among a representative sample of 298 Campylo bacter isolates. The strains, obtained between July 1989 and June 1990 from persons with sporadic cases of diarrhea, were collected from 19 randomly chosen counties in all geographic (census) regions of the Uni ted States. All strains were serotyped by the O and HL systems. By phe notypic methods, 288 C. jejuni, 9 hippurate-negative C. jejuni/C. coli , and 1 Campylobacter lari were identified. Of 57 O antisera, 24 typed 252 (84.6%) strains. Of the 55 HL antisera, 23 serotyped 253 (84.9%) strains. All strains were typeable in the unabsorbed O antisera. In th e absorbed HL antisera, four strains were nontypeable and 14 were roug h and untypeable. In each geographic region, 9 or more O and HL seroty pes were found. Serotypes O:1, O:4, and O:13,16,43,50 and HL 1 were id entified in all regions. The combination of both schemes gave greater discrimination than either system alone, but the maintenance of both r equires a large resource investment. A serotyping scheme incorporating the 24 most prevalent O and 23 most prevalent HL serotypes could be u seful for outbreak support and for surveillance. In the near future, w e anticipate using a molecular subtyping method in combination with li mited serotyping to distinguish Campylobacter strains.