15 research outputs found
Variable number of tandem repeats in clinical strains of Haemophilus influenzae
An algorithm capable of identifying short repeat motifs was developed and
used to screen the whole genome sequence available for Haemophilus
influenzae, since some of these repeats have been shown to affect
bacterial virulence. Various di- to hexanucleotide repeats were
identified, confirming and extending previous findings on the existence of
variable-number-of-tandem-repeat loci (VNTRs). Repeats with units of 7 or
8 nucleotides were not encountered. For all of the 3- to 6-nucleotide
repeats in the H. influenzae chromosome, PCR tests capable of detecting
allelic polymorphisms were designed. Fourteen of 18 of the potential VNTRs
were indeed highly polymorphic when different strains were screened. Two
of the potential VNTRs appeared to be short and homogeneous in length;
another one may be specific for the H. influenzae Rd strain only. One of
the primer sets generated fingerprint-type DNA banding patterns. The
various repeat types differed with respect to intrinsic stability as well.
It was noted for separate colonies derived from a single clinical specimen
or strains passaged for several weeks on chocolate agar plates that the
lengths of the VNTRs did not change. When several strains from different
patients infected during an outbreak of lung disease were analyzed,
increased but limited variation was encountered in al