GENOMIC DNA FINGERPRINTS AND PHENOTYPIC CHARACTERISTICS OF SEROTYPE-BHAEMOPHILUS-INFLUENZAE ISOLATES FROM ITALY

Three different restriction enzymes (PstI, EcoRI, SspI) were used to a nalyze the total genomic DNA fingerprints of 52 Haemophilus influenzae type b (Hib) isolates collected between 1982 and 1992 from patients a nd carriers in central-northern Italy. The same isolates were also cha racterized by biotyping and antimicrobial agent susceptibility typing. In addition, 13 Hib reference strains from Sweden and the Netherlands were subjected to DNA fingerprinting and compared to Italian isolates . Both genotypic and phenotypic analysis revealed low variability amon g the Italian study isolates. Most were biotype I and all study isolat es but one were susceptible to ampicillin, chloramphenicol, rifampin, third-generation cephalosporins and cotrimoxazole. Among the 52 Italia n isolates, 3 distinct DNA patterns were identified, and 88.5% of stud y strains belonged to the same DNA group. There was sharing of the pre dominant DNA profile among isolates cultured in different years from d ifferent geographical areas and different invasive, respiratory and su rface infections. However, another DNA pattern was only found in carri er isolates and in one surface infection isolate. Comparison by DNA fi ngerprinting showed that the majority of Italian isolates were closely related to most of the analyzed Swedish and Dutch reference strains, previously shown by other techniques to be predominant in those areas. This finding provides additional support for the hypothesis that ther e may be a dominant European Hib clone. The results show that DNA fing erprinting is a reliable method for Hib characterization and may be a useful additional epidemiological tool for this microorganism.