[Neisseria meningitidis and the increase of oral sex. A case report].

Urethritis is an entity characterized by dysuria and purulent urethral discharge, generally acquired sexually. Neisseria gonorrhoeae is one of the most frequently responsible microorganisms. Neisseria meningitidis is a gram-negative diplococcus usually isolated in the pharynx, that occasionally causes meningococcal meningitis, being unusual it's isolation in the anogenital area where it could be a genitourinary pathogen. We present the case of a 25-years-old heterosexual male who, after a heterosexual intercourse with an occasional non-professional partner, including oral and vaginal sex, presented with symptoms of urethritis, orienting to a sexually transmitted infection. The bacteriological culture for N. gonorrhoeae was negative and the PCR for Chlamydia trachomatis was positive. Subsequently, the lab reported a positive bacteriological culture for sero-group C N. meningitidis, sensitive to ceftriaxone and a negative PCR for N. gonorrhoeae. N. meningitidis is the main cause of bacterial meningitis, but genomic studies have suggested that alleles of nitrate reductase, factor-H biding protein and capsule are associated with N. meningitidis isolation in genitourinary infections. Transmission from the oropharynx to the urethra through orogenital contact in unprotected oral sex has been widely proven. N. meningitidis prevalence as the cause of the urethritis is low, and the asymptomatic carriers in the urethra are extremely rare. PCR is a method for the N. gonorrhoeae and C.trachomatis diagnoses, but it does not detect N. meningitidis. The gonorrhoea diagnosis is based on an increased number of polymorphonuclear cells, with intracellular gram-negative diplococci in Gram' stain of urethral discharge. In our case, the gram-negative diplococcus seen in the stain was a meningococcus. Urethritis due to N. meningitidis is indistinguishable from the secondary to N. gonorrhoeae, mimicking it even microscopically, only the epidemiology varies. The conventional bacteriological culture continues to be essential for a correct diagnosis.