Genotypic and serotypic stability of Campylobacter jejuni strains during in vitro and in vivo passage

The stability of four typing methods and the sero- and genotypic stability of three Campylobacter jejuni strains were evaluated after subculturing 50 times in triplicate and after colonising mice for up to 26 days. The employ ed methods were Penner heat-stable serotyping; automated ribotyping (RiboPr inting) using HaeIII restriction enzyme; pulsed-field gel electrophoresis ( PFGE) using SmaI, SalI and KpnI; and random amplified polymorphic DNA analy sis (RAPD) using primers 1254, 1281 and HLWL85. No changes in any of the DN A profiles or in the reactions to heat-stable antigens were identified amon g these strains after the in vitro and in vivo passages. However, one isola te became untypeable with RAPD after passage in one of the mice. In additio n, eleven other C. jejuni strains of four different serotypes were subcultu red ten times to screen for instability. Neither of these showed instabilit y using PFGE and serotyping. Furthermore, three of four strains previously identified as unstable, showed to consist of mixed cultures, which explains the reported profile changes. The results indicate that the applied typing methods are reliable and applicable for typing of Campylobacter isolates f rom different sources over time, and that many C. jejuni strains are geneti cally stable as tested by these methods.