Sunday, November 27, 2022

NEISSERIA GONORRHEAE (GONORRHEA)


MORPHOLOGY AND CULTURE: Gonococci are Gram-negative, coffee-bean-shaped cocci that are usually paired. Attachment pili on the bacterial cell surface are responsible for their adhesion to mucosal cells. Gonococci can be grown on moist culture mediums enriched with protein (blood). The atmosphere for primary culturing must contain 5–10% CO2.

PATHOGENESIS AND CLINICAL PICTURE: Gonorrhea is a sexually transmitted disease. The pathogens penetrate into the urogenital mucosa, causing a local purulent infection. In men, the prostate and epididymis can also become infected. In women, the gonococci can also cause salpingitis, oophoritis, or even peritonitis. Gonococci reaching the conjunctival membrane may cause a purulent conjunctivitis, seen mainly in newborn children. Gonococci can also infect the rectal or pharyngeal mucosa. Hematogenously disseminated gonococci may also cause arthritis or even endocarditis.


DETERMINANTS OF THE PATHOGENICITY OF GONOCOCCI: Attachment pili on the surface and the outer membrane protein are responsible for adhesion to cells of the urogenital tract. It also directs the invasion process by means of endocytosis. Immune defenses against granulocytes are based on the outer membrane porin that prevents the phagosome from fusing with lysosomes, resulting in the survival, and proliferation of phagocytosed gonococci in granulocytes. 

The lipo-oligosaccharide (LOS) in the outer membrane is responsible for resistance to complement (serum resistance) as well as for the inflammatory tissue reaction in a manner analogous to the more complexly structured LPS of enterobacteria.

Gonococci can capture iron from the siderophilic proteins lactoferrin and transferrin, accumulating it inside the bacterial cells to facilitate their rapid proliferation.

An IgA1 protease produced by the gonococci hydrolyzes secretory antibodies in the mucosal secretions. The pronounced antigen variability of the attachment pili and the Opa protein make it possible for gonococci to thwart specific immune defense mechanisms repeatedly.


DIAGNOSIS: The method of choice is detection of the pathogens by means of methylene blue and gram staining and culturing. Gonococci are sensitive in cultures and the material must be used immediately after they are obtained to inoculate. Thayer-Martin blood agar with antibiotics added to eliminate accompanying flora, on which medium the cultures are then transported to the laboratory. The identification procedure involves both morphology and biochemical characteristics. Techniques developed recently utilize immunofluorescence or coagglutination methods utilizing monoclonal antibodies to the main protein of the outer membrane, Por. Direct detection in pus and secretion samples is possible using an enzymatic immunosorbence test or detection of gonococcus-specific DNA sequences coding for rRNA using a gene probe.


THERAPY: The agent of choice used to be penicillin G. In recent years, however, the percentage of penicillinase-producing strains has increased considerably all over the world. For this reason, third-generation cephalosporins are now used to treat uncomplicated cases of gonorrhea. They are applied in a single dose (e.g., ceftriaxone, 250–500 mg I.M.). Good results have also been reported with single-dose oral application of fluorinated 4-quinolones (e.g., 0.5 g ciprofloxacin or 0.4 g ofloxacin).


RELATED;

1. Neisseria

2. Antimicrobial drug resistance

3. Penicillin

4. Cephalosporins

5. Medical microbiology

6. Pharmacology and therapeutics

References

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