OUTBREAK OF AMOXICILLIN-RESISTANT HAEMOPHILUS-INFLUENZAE TYPE-B - VARIABLE NUMBER OF TANDEM REPEATS AS NOVEL MOLECULAR MARKERS

An outbreak caused by amoxicillin-resistant Haemophilus influenzae typ e b was noted among patients suffering from chronic obstructive pulmon ary disease. Since infections were clustered in time and place, an ong oing outbreak was suspected. The spread of the strain and the course o f the outbreak could be followed by random amplification of polymorphi c DNA (RAPD) analysis of the different bacterial isolates. In addition , studies were aimed at the determination of length polymorphism in re gions of repetitive DNA. By PCR-mediated amplification of variable num ber of tandem repeat regions (VNTRs), additional insight into the geno me composition of the epidemic strain was gained. Our results show tha t VNTRs comprising repeat units that are 3, 5, or 6 nucleotides in len gth provided stable genetic markers that can be used for molecular typ ing of H. influenzae type b. VNTRs built from tetranucleotide units, h owever, appear to be hypervariable and not suited for epidemiological studies. The observed variability in this latter class of VNTRs might be reminiscent of the bacterium's capacity to deal with unfavorable ho st factors.