TETRAMERIC REPEAT UNITS ASSOCIATED WITH VIRULENCE FACTOR PHASE VARIATION IN HAEMOPHILUS ALSO OCCUR IN NEISSERIA SPP AND MORAXELLA-CATARRHALIS

The tetrameric repeat units 5'-CAAT-3' and 5'-GCAA-3' are associated w ith phase variable expression of lipopolysaccharide biosynthetic genes in Haemophilus influenzae. Four other tetrameric repeat units have al so been reported from H. influenzae strain Rd, 5'-CAAC-3', 5'-GACA-3', 5'-AGCT-3', and 5'-TTTA-3', which are also associated with putative v irulence factors. Using oligonucleotide probes corresponding to five t andem copies of each of these tetramers, we have screened three strain s of Neisseria meningitidis and one each of Neisseria gonorrhoeae, Nei sseria lactamica, Haemophilus parainfluenzae, Bordetella pertussis, Bo rdetella parapertussis, Bordetella bronchiceptica and Moraxella catarr halis for the presence of these motifs. We have demonstrated the prese nce of multiple copies of the 5'-GCAA-3' motif in;all the Neisseria st rains tested, and also the repeated motif 5'-CAAC-3' in M. catarrhalis . We have further demonstrated by Southern blot analysis that the 5'-C AAC-3' repeats detected in M. catarrhalis are probably associated with the same genes as in H. influenzae, but that the 5'-GCAA-3' motifs in N. meningitidis are not. The use of characterised tetrameric DNA sequ ences as hybridisation probes may prove useful in the identification o f novel phase variable virulence determinants in organisms other than H. influenzae.