CLONALITY OF MULTIDRUG-RESISTANT NONTYPABLE STRAINS OF HAEMOPHILUS-INFLUENZAE

The genetic structure of a population of multidrug-resistant nontypeab le (unencapsulated) Haemophilus influenzae strains isolated at a hospi tal in Barcelona, Spain, was investigated by using multilocus enzyme e lectrophoresis to determine the allelic variation in 15 structural loc i. In our study we have also included some antimicrobial agent-suscept ible strains isolated at the same hospital. All enzymes were polymorph ic for two to eight electromorphs, and the analysis revealed 43 distin ct electrophoretic types among the 44 isolates, The mean genetic diver sity of the entire population was 0.55, Multilocus linkage disequilibr ium analysis of the isolates revealed a strong association between all eles, suggesting little possibility of recombination. Furthermore, the dendrogram and the allele mismatch distribution are typical of a popu lation with no extensive genetic mixing.