No abstract

Campylobacter coli strains from clinical and other sources were examined in terms of O (heat-stabile; HS) serotype and by several molecular typing techniques. Restriction fragment length polymorphism (RFLP) around the three 16S rRNA genes revealed 10 variants, none found in Campylobacter jejuni. RFLP analysis of a polymerase chain reaction amplicon generated from the flagellin gene (flaA) yielded 11 polymorphism groups, some of them linked to HS serotypes. Enlarged flaA genes, contributing three further polymorphisms, were detected in strains isolated from fresh water. Restriction of the genome with SmaI and pulsed-field gel electrophoresis was the most discriminatory typing method, detecting 33 macrorestriction profiles that subtyped within HS serotypes. The coincidence of HS serotype and the three genotypic markers identified clonal lines of evolutionary and epidemiologic significance.

In Salmonella heidelberg the copy number of the Salmonella-specific insertion element IS200 was found to vary from four to six. All strains tested contained at least one common insertion site which was serovar specific, and most strains contained three common sites. Concurrent analysis of plasmids indicated that all insertion sequence copies were chromosomally located, and also supported the equivalence of an IS200 fingerprint and clonality. Seven intra-serovar clonal lines were thereby identified. One of these was associated with human infections, including septicaemias. Another was associated with chicken as a host: all these strains also carried a unique plasmid of 23 MDa, which was typed as a member of the IncX group. The chromosomal fingerprint of a third clone showed it to be a descendant of the chicken line marked by a single IS200 transposition. One or two representatives of four other clonal lines were identified. These lines of S. heidelberg could be related by divergent evolution, and the most recent relatives conformed to a continuous branching process model of IS200 transposition. This insertion sequence provided a highly discriminatory molecular marker of the S. heidelberg chromosome, and two of the seven clonal lines so identified were associated with distinct clinical/epidemiological contexts.

Salmonella paratyphi B and Salmonella java are biovars of common serotype 1,4,[5],12 : b: 1,2 which respectively cause human paratyphoid fever and gastroenteritis. In order to define genotypes and phylogenetic relationships in this group, we examined representative strains for restriction fragment length polymorphisms (RFLPs) in and around the 16s ribosomal RNA (rrn) genes, and the five to eleven insertion sites of the Salmonella-specific DNA insertion sequence IS2UU. One of four 16s rrn profiles was predominant, and was shared by the majority of strains, irrespective of their designation as S. paratyphi B or S. java. On the other hand, thirteen unique IS200 profiles were found and this technique was able to distinguish, for the first time, distinct genotypes for S. paratyphi B and S. java. One of the S. paratyphi B profiles, Spj-IPl . 0, represented a globally-distributed clone. Greater diversity was detected within IS200 profiles of S. java than within those of S. paratyphi B. IS200 profiles described a phylogenetic complex in which strains of both biovars could be placed. They constituted reproducible molecular fingerprints, which could be compared in a band-matching database suitable for molecular epidemiological typing.

In order to provide a profile of the plasmid gene pool in Sdmoneffa prior to the clinical use of antibiotics, a molecular genetic analysis was made of plasmids in strains collected by E. D. G . Murray between 1917 and 1954. These pre-antibiotic era (PAE) salmonellae contain conjugative plasmids of the same incompatibility groups as contemporary enterobacterial plasmids. Upon analysis of total plasmid content, 42 plasmids, sized between 23 and 72 MDa, were found. We defined and investigated six groups of these PAE Sdmoneffa plasmids in terms of three groups of genes; those involved in plasmid maintenance and incompatibility, DNA repair and virulence. Of the five groups, three were replicon-typed to groups IncI1, IncX and IncFII; one group exhibited no homology to contemporary InclRep probes, and one group represented virulence plasmids containing a common plasmidpartitioning locus. The results indicated that most of the PAE groups were progenitors of contemporary Rplasmids, except for the virulence plasmids, which have generally not evolved as vectors of antibiotic resistance.