Gonococci

Gonorrhea (Greek gonos - semen and rhoe - discharge) is an infectious disease of humans caused by gonococcus and characterized by inflammatory lesions mainly of the mucous membranes of the genitourinary organs.

The causative agent of gonorrhea is Neisseria gonorrhoeae, discovered in 1879 by A. Neisser - a bacterium, is a coccus similar to a coffee bean or bud, located in pairs, the concave sides of the cells facing each other. The size is 0.7-0.8, sometimes 1.25-1.60 μm. Cocci divide in one plane. During an electron microscopic examination, a mucous capsule-like formation 0.35-0.40 μm thick is found around the gonococcus, due to which the cocci do not touch each other: a gap is maintained between them. Gonococci are gram-negative, they perceive the main aniline dyes well. Methylene blue is often used to stain preparations from gonorrheal pus, since it better reveals the bean-shaped form of gonococci, and Gram staining is required to distinguish them from other similar diplococci. Phagocytosis of gonococci is incomplete, complete phagocytosis is observed in monocytes and histiocytes. Gonococci do not have flagella, capsules, spores and do not form pigment. The content of G + C in DNA is 49.5-49.6 mol %. They grow poorly on meat-peptone agar, they reproduce better on media containing serum, ascitic fluid or blood. They do not cause hemolysis. For the growth of gonococci, the presence of iron in the medium is necessary. The addition of starch, cholesterol, albumin or coal particles to dense nutrient media promotes growth, and the addition of Ca++ ions increases viability. The optimum temperature for growth is 35-36 "C, but growth occurs in the range of 30-38.5 ° C, the optimum pH is 7.2-7.6. Gonococci are strict aerobes, but during primary sowings they grow better with a slight increase in the CO2 content.

D. Kellogg et al. revealed a relationship between the virulence of gonococci and the nature of the colonies they form. Gonococci that are virulent to humans and isolated from patients with acute gonorrhea have pili and form small, drop-shaped, shiny colonies designated as T1 and T2. Large, flat, and dull colonies (T3 and T4) are formed by non-virulent gonococci that do not contain pili. Of the carbohydrates, gonococci ferment only glucose, producing acid without gas. There are various antigen populations among gonococci. This is confirmed by the lack of immunity to repeated infection in humans. In accordance with this, attempts have been made to develop a universal serological classification of gonococci. In particular, gonococci are divided into 16 serotypes based on the protein antigens of the outer membrane. In addition, gonococci also differ in their lipopolysaccharide antigens. Antigenic kinship of gonococci with other species of Neisseria has been discovered, most closely with meningococci. Gonococci synthesize bacteriocins, which can also be used for their typing.

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Pathogenicity factors of gonococci

Exotoxins have not been detected in gonococci. The main pathogenicity factors are pili, with the help of which gonococci adhere to and colonize epithelial cells of the urogenital mucosa, and endotoxin (lipopolysaccharide) released during the destruction of gonococci.

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Resistance of gonococci

Gonococci have weak resistance to external influences: they quickly die under the influence of direct sunlight, UV light, drying, high temperature (at 40 °C they quickly lose viability). Various chemicals, such as silver salts, mercury, and conventional disinfectants kill them within a short time. Thus, silver nitrate in a dilution of 1:5000 kills gonococci within 1 minute, and in a dilution of 1:10,000 - after 10 minutes.

Post-infectious immunity

Having suffered from gonorrhea does not leave immunity to re-infection, but this circumstance is probably due to the fact that immunity is type-specific, since antibodies are found in the blood of those who have had the disease in fairly high titers.

Epidemiology, pathogenesis and symptoms of gonorrhea

Gonococcus is not pathogenic for animals. The only source of infection is a person infected with gonococci. Infection occurs mainly through sexual intercourse, sometimes through household items. The main habitat of gonococci is the surface of the mucous membrane of the urogenital tract, less often - the rectum and pharynx. The entry point in men is the mucous membrane of the urethra, in women - most often the mucous membrane of the vestibule of the vagina, urethra and cervix. In case of penetration through the epithelial barrier, gonococci can spread to surrounding tissues: to the glands of the urethra and cervix, prostate gland, seminal vesicles, uterus and fallopian (uterine) tubes, enter the blood, penetrate the synovial membranes of the joints, heart and other organs, causing inflammatory processes, and sometimes septicemia. Under certain conditions, gonococci can penetrate the conjunctiva and cause ophthalmia (inflammation of the mucous membrane of the eye - blenorrhea). This is most often observed in children born to mothers infected with gonococci. The incubation period of gonorrhea varies from one day to 2-3 weeks or more, but most often it is 3-4 days. Symptoms of gonorrhea allow us to distinguish two main forms of gonorrhea - acute and chronic. A typical symptom of acute gonorrhea is acute purulent inflammation of the urethra, glands of the lower genital organs and the cervix in women, accompanied by pain, as well as profuse purulent discharge from the urethra. Chronic gonorrhea is typically characterized by a more sluggish manifestation of clinical symptoms associated with the location of the pathogen.

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Diagnosis of gonorrhea

Bacterioscopic - the material for the study is purulent discharge from the urethra, vagina, cervix, prostate gland and other organs affected by gonococcus, as well as sediment and urine threads. As a rule, smears are stained with Gram and methylene blue. Gonococci are detected by three characteristic features: gram-negative staining, bean-shaped diplococci, intracellular location. Direct and indirect immunofluorescence is also used to detect gonococci in a smear. However, under the influence of chemo- and antibiotic therapy, as well as in chronic gonorrhea, the morphology and Gram staining of gonococci may change, in addition, there may be very few of them in the smear. Often, with chronic gonorrhea, Asha-type gonococci are found in smears: diplococcus cells have different sizes and shapes. In such cases, a bacteriological method is used. For this purpose, the material to be examined is seeded on special nutrient media. The isolated culture is identified taking into account the characteristics of gonococci. It should be taken into account that if gonococci were Gram-positive in smears from purulent material, then Gram-negative staining is restored in smears from the grown culture. All gonococci in a 24-hour culture are almost the same size, the shape of diplococci or cocci, but after 72-96 hours the culture becomes polymorphic and the cells are Gram-stained unevenly. In chronic gonorrhea, RSC or an allergic skin test with a special gonococcal allergen can be used for diagnosis.

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Treatment of gonorrhea

Treatment of gonorrhea is carried out with antibiotics and sulfanilamide preparations. Good results are obtained by using various penicillins, tetracycline preparations and other antibiotics. Since gonococci develop resistance to them, it is necessary to determine which antibiotics the gonococci isolated from the patient are sensitive to.

Prevention of gonorrhea

Specific prevention of gonorrhea has not been developed. General prevention is the same as for other venereal diseases, since infection occurs mainly through sexual intercourse. To prevent blenorrhea in newborns, 1-2 drops of a 2% silver nitrate solution or (especially in premature babies) 2 drops of a 3% oil solution of penicillin are injected into the conjunctival sac, to which gonococci are very sensitive and quickly die from it (in 15-30 minutes).