We describe a molecular subtyping scheme for two principal O (heat-stable [HS]) serotypes of Campylobacter jejuni, HS1 and the HS4 complex. A 16S rRNA gene-specific probe confirmed that almost all the C. jejuni strains had three copies of this gene, and strains could be assigned with complete typeability to 1 of 16 combined (PstI and HaeIII) 16S ribotypes. Macrorestriction profiles (mrps) consisting of up to 10 SmaI fragments from ϳ40 to ϳ480 kbp were resolved by pulsed-field gel electrophoresis (PFGE). There were 11 mrps among the HS1 strains and 9 mrps among HS4 strains which corresponded to valid types-they occurred in multiple isolates, hosts, places, and times. There were 14 additional single-strain mrp fingerprints in HS1 and 20 in HS4. PFGE exhibited complete typeability when formaldehyde fixation of cells was employed, and PFGE was generally more differential than ribotyping. The data presented elucidate a high-resolution genotypic subtyping scheme for these common subspecific phenotypes of C. jejuni, which is both coherent and efficient for epidemiological purposes.
Current methods of isolating and purifying bacterial chromosomal DNA in sufficient quantities for base composition estimation and hybridization are relatively laborious and time consuming (1). As part of our work on the use
SU'MMARYFlagellin gene sequence polymorphisms were used to discriminate amongst 77 strains of Carnpylobacter jejuni from sporadic and outbreak-associated human enteric infections, and from chickens, sheep and calves. The results were assessed in relation to Lior biotyping and serotyping (Penner somatic antigens). Eight DNA PCR-RFLP patterns (genotypes) were identified by analysis of HinfI fragment length polymorphisms in flagellin gene (flaA) polymerase chain reaction (PCR) products. One genotype (F-1) was a feature of 55 % of strains. Strains within the genotypes were heterogeneous with respect to somatic antigens with 12 serogroups represented amongst the C. jejuni isolates offla A type F-1. Serogroups Pen 1, 2 and 23 were the commonest (45 %) amongst the 20 different serogroups represented. Several unique clusters of isolates with diverse biotypes were defined, and one cluster (F-7/Pen 23) contained epidemiologically implicated outbreak strains as well as sheep and calf isolates. We conclude that HinfI fia A typing is reproducible and offers high typability, and its combination with serogrouping provides a novel approach to characterizing isolates of C. jejuni with improved discrimination.
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