Neisseria gonorrhoeae

Neisseria gonorrhoeae (the gonococcus)

Organism

Neisseria gonorrhoeae is a gram-negative diplococcus, typically flattened where the cocci meet.
Aerobic (def).

Habitat

Humans are the only natural host.

Source

Transmitted sexually by contact with an infected individual; may be transmitted from mother to baby during birth.

Clinical Disease

CDC estimates that more than 700,000 persons in the U.S. get new gonorrheal infections each year. Only about half of these infections are reported to CDC. In 2002, 351,852 cases of gonorrhea were reported in thr U.S..
Neisseria gonorrhoeae typically infects the mucous membranes causing infections such as urethritis (def), cervicitis (def), salpingitis (def), pelvic inflammatory disease (def), proctitis (def), conjunctivitis (def), and pharyngitis (def).
In males there is typically a 2-3 day incubation period after which a purulent (def) discharge from the urethra and dysuria (def) develops. Around 95% of infected males are symptomatic. Rare complications include prostatitis (def), epididymitis (def), and periurethral abcesses (def).
The gonococcus primarily infects the cervix in women. Symptoms include vaginal discharge, dysuria (def), and abdominal pain. Complications from an ascending infection include absesses of the ovarian tubes and pelvic inflammatory disease (def). Around 10%-20% of infected women develop these complications.
In 1%-3% of infected women and a lower percentage of infected men the bacterium disseminates via the blood causing bacteremia (def) and arthritis (def).
Congenital gonorrhea typically appears as ophthalmia neonatorum (def) and occurs as a result of the eyes of newborns becoming infected as the baby passes through the birth canal. Antibiotic drops are put in the eyes of newborns to prevent congenital gonorrhea and congenital Chlamydia infection.

Pathogenicity

In the outer membrane of the gram-negative cell wall, the lipooligosaccharide (LOS) functions as an endotoxin . Endotoxin, especially when in the blood, can lead to inflammation, high fever, hypotension, capillary damage, intravascular coagulation, tissue degradation, and irreversible shock. Death is a result of what is called the shock cascade (see Fig. 1).
Various types of pili (def) enable the bacterium to initially adhere to epithelial cells of the mucous membranes. Gonococci are constantly losing and reforming pili as they grow in the body and the same bacterium may switch the adhesive tips of the pili in order to adhere to different types of host cells and evade immune defenses
A variety of cell wall adhesins (def) enable the bacterium to make a more intimate contact with the mucous membranes.
- Por protein (protein I) prevents phagosomes from fusing with lysosomes to promote survival within phagocytes.
- Opa protein (protein II) allows for firm attachment to host cells. Like pili, there are multiple alleles for Opa protein enabling the bacterium to adhere to different host cell types.
- Rmp protein (protein III) protects other surface proteins and LOS from antibody attack.
Transferrin-binding proteins, lactoferrin-binding proteins, and hemoglobin-binding proteins allow the gonococcus to obtain iron bound to human iron-binding proteins.
IgA₁ protease degrades the human antibody IgA₁(def).

Treatment

Uncomplicated gonorrhea can be treated with ceftriaxone, cefixime, ciprofloxacin, or ofloxacin; doxycycline or azrithromycin (see antibiotic table) is added for those infected with both Neisseria gonorrhoeae and Chlamydia trachomatis.*

*Drugs may change with time.

For a more detailed article on Neisseria gonorrhoeae infections, see Gonococcal Infections, by Larry I Lutwick, MD, Director, Division of Infectious Diseases, Veterans Affairs New York Harbor Health Care System, Professor, Department of Internal Medicine, State University of New York at Downstate; Renuka Heddurshetti, MD, Fellow in Infectious Diseases, Department of Internal Medicine, State University of New York at Brooklyn; and Sanda Cebular, MD, Fellow, Department of Medicine, Section of Infectious Diseases, State University of New York at Brooklyn.