Haemophilus influenzae as a single isolate in male patients with acute urethritis: a clinical and microbiological case series analysis

BACKGROUND: Studies evaluating the role of Haemophilus influenzae (H. influenzae) in acute urethritis are scarce ; therefore more studies are needed to define its true propensity for causing inflammation of the urethra. AIMS: To describe clinical characteristics of men with H. influenzae-positive urethritis and to correlate it with biotypes and microbiological specificities of different strains. METHODS: This retrospective case series analysis included clinical, microbiological and behavioral data of men with H. influenzae-positive acute urethritis. Other potential causative agents of urethritis were excluded by classic and molecular laboratory techniques. Identification of H. influenzae and strain biotyping (based upon the ability to produce indole, urease and ornithine decarboxylase) was done by using API NH strip (bioMerieux, France). Kirby-Bauer disk-diffusion method and nitrocefin (a chromogenic cephalosporin) were used to assess antimicrobial profile. RESULTS: From a total of 376 patients presenting to the STD outpatient clinic with acute urethritis symptoms, 11 of them (2.9%) harboured H. influenzae as a sole isolate. Six of those isolates belonged to the biotype IV and were closely correlated with mucopurulent urethral discharge mimicking gonorrhoea ; the others belonged to the biotype II and III. Beta-lactamase activity and ampicillin resistance was found in 27.2% of those isolates. CONCLUSIONS: Due to an increasing trend of variable human sexual behaviour and ensuing STDs, the importance of H. influenzae as a potential cause of acute (and often purulent) urethritis should be taken into account. From a microbiological perspective, adequate microbiological techniques should be used to maximize the yield of this pathogen and guide appropriate treatment.