Urethritis is a common disorder, classified according to the causative pathogens as gonococcal (GU) or non-gonococcal (NGU). Chlamydia trachomatis remains the most common NGU pathogen, however the relative pathogenicity of other bacteria in causing NGU is not well understood. A recent retrospective study was performed to clarify the role of Haemophilus influenzae in causing NGU, and its response to antimicrobial therapy.

68 men diagnosed with acute urethritis were confirmed to also have H. influenzae infection. Patients also reported coinfections with Neisseria gonorrhea, Chlamydia trachomatis, and/or genital mycoplasmas. Patients had been treated with a number of different antibiotics, including ceftriaxone, levofloxacin, sitafloxacin and extended-release azithromycin (azithromycin-SR), and MIC values determined from pre-treatment isolates. Microbiological data for 54 men and clinical data for 46 men, all with H. influenzae-positive monomicrobial NGU was analyzed.

Levofloxacin, sitafloxacin and ceftriaxone successfully eradicated 100% of H. influenzae in men with NGU, while eradication was lower with azithromycin-SR (85.3%). The eradication of the pathogen was associated with clinical improvement and alleviation of symptoms, as well as improvement in laboratory markers.

The H. influenzae MICs for the individual antibiotics were as follows:   ceftriaxone ≤0.008-0.25, levofloxacin 0.008-0.5, sitafloxacin 0.001-0.008, azithromycin 0.12-1, tetracycline 0.25-16, and doxycycline 0.25-2 μg/mL. Researchers drew attention to the fact that following treatment with azithromycin-SR, 3 of 4 isolates had MICs of 1 μg/mL, and that this may indicate reduced future efficacy for azithromycin in these infections.

This study is important in adding to the limited data available on H. influenzae in NGU, with researchers concluding that the clear association between bacterial eradication and symptomatic improvement supports the understanding that H. influenzae needs to be considered when treating NGU.

PMID: 28282645

Sex Transm Dis. 2017 Apr;44(4):205-210. doi: 10.1097/OLQ.0000000000000573.

Source: https://www.ncbi.nlm.nih.gov/pubmed/28282645?dopt=Abstract