Sequence typing of Haemophilus ducreyi isolated from patients in the Namatanai region of Papua New Guinea: Infections by Class I and Class II strain types differ in ulcer duration and resurgence of infection after azithromycin treatment.

Haemophilus ducreyi (HD) is an important cause of cutaneous ulcers in several endemic regions, including the Western Pacific Region, especially among children. An HD sequence typing on swab samples taken from 1,081 ulcers in the Namatanai district of Papua New Guinea, during the pilot study for treatment of yaws, has been performed using the Grant typing system. Of the 363 samples that tested positive for the 16S rDNA of HD, the dsrA sequences of 270 samples were determined. Altogether they revealed 8 HD strain types circulating in Namatanai, including seven strain types of Class I (I.3, I.4, I.5, I.9, I.10, I.11, I.12) and one strain of Class II (II.3); four Class I types (I.9, I.10, I.11, I.12) were novel. The southern region of Namatanai (Matalai Rural) was identified as the region with the lowest genotype diversity and with most infections caused by HD Class II. The middle and northern subdistricts were affected mainly by HD Class I. Analysis of patient characteristics revealed that Class II HD infections were more often represented by longer-lasting ulcers than Class I HD infections. An increase in the prevalence of the I.10 strain was found after azithromycin administration compared to the untreated population at baseline likely reflecting higher infectivity of HD Class I, and more specifically strain type I.10. Author summary: Haemophilus ducreyi (HD) is one of the main causative agents of cutaneous ulcers in children across substantial parts of Africa and the Pacific. A yaws eradication study conducted in the Namatanai district of Papua New Guinea revealed that nearly one-third of all patients were infected with HD. Single locus sequence typing (SLST) of the HD dsrA locus revealed presence of multiple HD strains circulating in the human population of Namatanai region. In contrast to Treponema pallidum subsp. pertenue, the pathogen responsible for yaws, the prevalence of HD strains did not significantly decrease following mass drug administration. In addition, HD strains from patients in Namatanai region revealed a higher genetic diversity compared to the yaws agent present in the same area and the HD strain composition changed following antibiotic treatment. Infections caused by at least some different HD strain types appear to differ in reported ulcer duration and also in resurgence of infection after antibiotic treatment. Therefore, important pathophysiological differences among HD strain types were predicted. [ABSTRACT FROM AUTHOR]