[In situ hybridization with DNA probe for the diagnosis of Neisseria gonorrhoeae infections].

A comparative study of a DNA probe for the detection of Neisseria gonorrhoeae with Gram stain and modified Thayer-Martin medium was performed. The probe was the 2.6 megadaltons (Mda) cryptic plasmid of N. gonorrhoeae, labeled with a nonradioactive system combining sulphonation of DNA with the antibody detection of sulphonated groups (Organics Chemiprobe). Overall 101 samples were evaluated: 39 urethral exudates, 3 rectal exudates, and 59 cervical exudates, from 42 males and 54 females in whom gonococcal infection was suspected. Simultaneously, Gram stain and culture of the several exudates were carried out. The in vitro sensitivity of the method was evaluated with different dilutions of N. gonorrhoeae, from 1 to 1000 cfu/ml, and a minimum of 50 cfu/ml were detected. In the detection of N. gonorrhoeae in clinical samples, there was a 100% sensitivity and a specificity of 83% (males) and 79% (females), with positive predictive value of 97% in males and 53% in females. The negative predictive value was 100% both for males and females.