What is the best way to check for gonococci

Gonococcal infection can easily cause some reproductive diseases, so attention should be paid to some examinations of gonococci. The examination methods include secretion smear examination, isolation and culture of gonococci, and oxidase test.

1. Smear examination of secretions

Mainly suitable for men.

(1) Clean the urethral opening with sterile saline.

(2) After wearing sterilized gloves, use your fingers to squeeze out pus from the base of the penis toward the urethral opening. Use an inoculation loop or cotton swab to pick up the pus and gently apply it on a glass slide. After it dries naturally, heat and fix it, perform Gram staining, and then examine it under a microscope.

(3) The diagnosis can be confirmed when Gram-negative Nephroticoccus is found in polymorphonuclear leukocytes.

2. Isolation and culture of gonococci

(1) Collection of materials.

① When taking samples from the urethra of male patients, a small cotton swab can be inserted into the urethra 2 to 4 cm, and the secretions (which should be slightly mucous) can be removed after gently rotating.

② When sampling from female patients, first use a vaginal speculum to expose the cervical os, wipe off the secretions on the surface of the cervical os with a sterile cotton swab, and then take another cotton swab and insert it 1 to 2 cm into the cervical os, rotate it and stay for 10 to 20 seconds before taking it out.

③ When taking samples from the rectum, the cotton swab should be inserted 2 to 3 cm into the anus.

④ When examining gonococcal pharyngitis, samples should be taken from the tonsils and tonsillar fossa.

⑤ Vaginal secretion samples can be collected from pre-pubertal girls.

(2) After the specimen is taken out, it is immediately inoculated into the culture medium. Currently, blood agar or chocolate agar medium with polymyxin added is commonly used.

(3) For the initial separation, a 5% to 10% CO2 candle jar should be used, the culture temperature should be 36°C, the relative humidity should be above 80%, and the culture should be kept for 24 to 48 hours to observe the results.

(4) After 24 to 48 hours of culture on polymyxin B blood agar, gonococci can form round, raised, moist, smooth, translucent or grayish white colonies with petal-shaped edges and a diameter of 0.5 to 1.0 cm. They are sticky when touched with an inoculation loop. If the culture is continued, the colony volume will increase, the surface will be rough, and the edges will shrink.

3. Identification of Neisseria gonorrhoeae - Oxidase test

(1) Preparation of oxidase reagent: 0.5% to 1% dimethyl-p-phenylenediamine hydrochloride aqueous solution.

(2) Add the solution dropwise onto the suspected bacterial colony and observe the color change. You can also drop the reagent on a small piece of filter paper first, then pick up suspicious colonies to contact it and observe the color change.

(3) The colonies turn red within 15 to 20 seconds of contact with the oxidase reagent, remain red for more than 30 seconds, then gradually turn purple and finally black. This indicates a positive oxidase test, confirming that the colonies are gonococci.