Oral sex may be a risk factor for nongonococcal urethritis ( NGU ), one of the most common sexually transmitted diseases affecting both men and women.

The study, by Australian researchers Catriona Bradshaw, and colleagues at the Melbourne Sexual Health Centre, is the first major case-control study to simultaneously address all currently hypothesized causes of nongonococcal urethritis .

Nongonococcal urethritis is caused by a number of different organisms ( most notably, Chlamydia trachomatis ) and may lead to pelvic inflammatory disease, infertility, and chronic pelvic pain.
Though the cause of nongonococcal urethritis is sometimes known, and antibiotics ( Azithromycin or tetracycline ) are generally effective, about half of all cases have no identifiable cause – a fact that makes treatment frustrating and uncertain for physicians and patients.
Results of previous studies show that Chlamydia trachomatis causes between 30 percent to 50 percent of cases of nongonococcal urethritis and Mycoplasma genitalium, 10 percent to 30 percent.

From March 2004 to March 2005, the Melbourne team studied 329 men with nongonococcal urethritis and 307 men without symptoms of urethritis. All subjects were given a sexual practice questionnaire. The men in the study underwent a urethral smear, and provided a first-stream urine specimen, which was tested for pathogens that may have caused nongonococcal urethritis.

Chlamydial infection was common in both heterosexual and homosexual men with nongonococcal urethritis ( 22 percent and 15 percent, respectively ) and was far more common than in control groups.
C. trachomatis and M. genitalium were associated with unprotected vaginal sex. M. genitalium ( 9 percent ), adenoviruses ( 4 percent ), and herpes simplex type 1 ( 2 percent ) were more common in nongonococcal urethritis patients than in controls, after adjusting for age and risk, which suggests that these organisms may be causes of nongonococcal urethritis.

Adenoviruses and herpes simplex type 1 were associated with oral sex and sex between male partners, suggesting that oral-genital contact may be an important mechanism of nongonococcal urethritis pathogen transmission. Additionally, nongonococcal urethritis was associated with history of oral sex with new partners. Together, these findings suggest that fellatio plays a significant role as a cause of the syndrome.

The study provides important insight for both heterosexual and homosexual men, as it indicates that nongonococcal urethritis may be caused by otherwise harmless organisms shared by monogamous partners.
This finding may influence clinical management of partners and counseling of couples.
In addition, oral sex was associated with nongonococcal urethritis in which no pathogen was detected, indicating that there are causes of nongonococcal urethritis that have yet to be identified.
The study also found that type 1 herpes simplex virus ( HSV-1 ), the usual cause of oral herpes, accounted for more nongonococcal urethritis cases than did HSV-2; that herpetic nongonococcal urethritis was most commonly associated with fellatio; and that up to a third of nongonococcal urethritis cases associated with known pathogens were not associated with increased numbers of white blood cells in urethral secretions.

Source: Infectious Diseases Society of America, 2006


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