Dataset Information

Haemophilus ducreyi Cutaneous Ulcer Strains Diverged from Both Class I and Class II Genital Ulcer Strains: Implications for Epidemiological Studies.

ABSTRACT:

Background

Haemophilus ducreyi has emerged as a major cause of cutaneous ulcers (CU) in yaws-endemic regions of the tropics in the South Pacific, South East Asia and Africa. H. ducreyi was once thought only to cause the genital ulcer (GU) disease chancroid; GU strains belong to 2 distinct classes, class I and class II. Using whole-genome sequencing of 4 CU strains from Samoa, 1 from Vanuatu and 1 from Papua New Guinea, we showed that CU strains diverged from the class I strain 35000HP and that one CU strain expressed β-lactamase. Recently, the Center for Disease Control and Prevention released the genomes of 11 additional CU strains from Vanuatu and Ghana; however, the evolutionary relationship of these CU strains to previously-characterized CU and GU strains is unknown.

Methodology/principal findings

We performed phylogenetic analysis of 17 CU and 10 GU strains. Class I and class II GU strains formed two distinct clades. The class I strains formed two subclades, one containing 35000HP and HD183 and the other containing the remainder of the class I strains. Twelve of the CU strains formed a subclone under the class I 35000HP subclade, while 2 CU strains formed a subclone under the other class I subclade. Unexpectedly, 3 of the CU strains formed a subclone under the class II clade. Phylogenetic analysis of dsrA-hgbA-ncaA sequences yielded a tree similar to that of whole-genome phylogenetic tree.

Conclusions/significance

CU strains diverged from multiple lineages within both class I and class II GU strains. Multilocus sequence typing of dsrA-hgbA-ncaA could be reliably used for epidemiological investigation of CU and GU strains. As class II strains grow relatively poorly and are relatively more susceptible to vancomycin than class I strains, these findings have implications for methods to recover CU strains. Comparison of contemporary CU and GU isolates would help clarify the relationship between these entities.

SUBMITTER: Gangaiah D

PROVIDER: S-EPMC5222509 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:We analyzed the LKP fimbrial gene clusters of six piliated strains of a cryptic genospecies of Haemophilus isolated from the genital tracts of adult patients (five strains) and from an infected neonate. In a group of 19 genital strains, LKP-like genes have been found in only these 6 strains. In addition to the ghfA, ghfD, and ghfE genes previously described, we characterized two genes, designated ghfB and ghfC, encoding the putative chaperone and assembly platform proteins. All six strains had a complete and unique LKP-like gene cluster consisting of the five genes ghfA to ghfE, homologous to genes hifA to hifE of Haemophilus influenzae. The sequences of the coding and intergenic regions of the ghf clusters of the six strains were remarkably homologous. Unlike hif clusters, which are inserted between purE and pepN, the ghf cluster was inserted between purK and pepN on the chromosome. Analysis of the flanking regions of the ghf cluster identified a large deletion, identical in the 5' end regions of all strains, including the whole purE gene and much of the purK gene. Ultrastructural observations, an attempt at enriching LKP fimbriae, and hemagglutination experiments demonstrated that none of the strains had LKP-type fimbriae. Nevertheless, reverse transcription (RT)-PCR showed that ghf genes were transcribed in four of the six strains. Sequencing of the intergenic ghfA-ghfB regions, including the ghf gene promoters, showed that the absence of transcripts in the remaining two strains was due to a decrease in the number of TA repeats (4 or 9 repeats rather than 10) between the -10 and -35 boxes of the two overlapping and divergent promoters. The other four strains, which had ghf transcripts, had the optimal 10 TA repeats (one strain) or 5 repeats associated with putative alternative -35 boxes (three strains). The absence of 10 repeated palindromic sequences of 44 or 45 nucleotides upstream of ghfB induces an increased instability of mRNA, as quantified by real-time RT-PCR, and may explain why the LKP fimbrial gene cluster is not expressed in these strains.