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Haemophilus influenzae Isolated From Men With Acute Urethritis: Its Pathogenic Roles, Responses to Antimicrobial Chemotherapies, and Antimicrobial Susceptibilities

Ito, Shin MD; Hatazaki, Kyoko MSc; Shimuta, Ken PhD; Kondo, Hiromi MD; Mizutani, Kosuke MD; Yasuda, Mitsuru MD; Nakane, Keita MD; Tsuchiya, Tomohiro MD; Yokoi, Shigeaki MD; Nakano, Masahiro MD; Ohinishi, Makoto MD; Deguchi, Takashi MD

Sexually Transmitted Diseases: April 2017 - Volume 44 - Issue 4 - p 205–210
doi: 10.1097/OLQ.0000000000000573
Original Studies

Background There have been few comprehensive studies on Haemophilus influenza–positive urethritis.

Methods In this retrospective study, we enrolled 68 men with H. influenzae–positive urethritis, including coinfections with Neisseria gonorrhoeae, Chlamydia trachomatis, and/or genital mycoplasmas: 2, 3, 20, and 43 treated with ceftriaxone, levofloxacin, sitafloxacin, and extended-release azithromycin (azithromycin-SR), respectively. We assessed microbiological outcomes in 54 men and clinical outcomes in 46 with H. influenzae–positive monomicrobial nongonococcal urethritis. We determined minimum inhibitory concentrations (MICs) of 6 antimicrobial agents for 59 pretreatment isolates.

Results H. influenzae was eradicated from the men treated with ceftriaxone, levofloxacin, or sitafloxacin. The eradication rate with azithromycin-SR was 85.3%. The disappearance or alleviation of urethritis symptoms and the decreases in leukocyte counts in first-voided urine were significantly associated with the eradication of H. influenzae after treatment. For the isolates, ceftriaxone, levofloxacin, sitafloxacin, azithromycin, tetracycline, and doxycycline MICs were ≤0.008–0.25, 0.008–0.5, 0.001–0.008, 0.12–1, 0.25–16, and 0.25–2 μg/mL, respectively. The azithromycin MICs for 3 of 4 strains persisting after azithromycin-SR administration were 1 μg/mL. H. influenzae with an azithromycin MIC of 1 μg/mL increased chronologically.

Conclusions H. influenzae showed good responses to the chemotherapies for urethritis. The significant associations of the clinical outcomes of the chemotherapies with their microbiological outcomes suggested that H. influenzae could play pathogenic roles in urethritis. All isolates, except for one with decreased susceptibility to tetracyclines, were susceptible to the examined agents. However, the increase in H. influenzae with an azithromycin MIC of 1 μg/mL might threaten efficacies of azithromycin regimens on H. influenzae–positive urethritis.

Haemophilus influenzae could play pathogenic roles in acute urethritis, showed good responses to the antimicrobial chemotherapies for urethritis, and was susceptible to the antimicrobial agents recommended for treatment of urethritis.

From the *iClinic, 5-9-6 Nagamachi, Taihaku-ku, Sendai, Miyagi; †Department of Urology, Graduate School of Medicine, Gifu University, Gifu City, Gifu; and ‡Department of Bacteriology I, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo, Japan

This work was supported in part by the Japan Society for the Promotion of Science (JSPS), Japan (Grant-in-Aid for Scientific Research [C] 25462509 and [C] 26462442).

Conflicts of interest: None declared.

Correspondence: Takashi Deguchi, MD, Department of Urology, Graduate School of Medicine, Gifu University, 1-1 Yanagido, Gifu City, Gifu 501-1194, Japan. E-mail:

Received for publication August 9, 2016, and accepted December 1, 2016.

© Copyright 2017 American Sexually Transmitted Diseases Association