Neisseria gonorrhoeae




neisseria_gonorrhoeae_pic.jpg

Bacterial identification


Gram staining....................... G-
Shape.................................. diplococcus (in pairs)
Aerobic growth....................... +
Anaerobic growth................... -
Endospores........................... -
Motility.................................. -
Catalase reaction.................. +
Benzidine reaction................. +
Oxidase reaction................... +
Glucose oxidative medium...... +
Glucose fermentative medium.. -


................................................................................................................................................................Electron micrograph of N. gonorrhoeae, magnification x100 000
................................................................................................................................................................Diagram taken from public domain at http://www.eol.org/pages/3335


Properties of an organism



-Gonococci are highly susceptible to physiscal and chemical agents and therefore are rapidly destroyed in the environment.
-Diplococcus arrangement resembles kidney bean or coffee bean because of the flattened sides being attached to one another.
-The organisms are strictly aerobic growing best on chocolate agar at 35-37˚C in the presence of 3-10% CO₂.
-T1-T5 colonies can be distingueshed: T1 and T2: small, contain piliated organisms, virulent; T3, T4 and T5: produced by subculture on nonselective medium, larger, nonpiliated, avirulent.
-
-Differentiation of the gonnococcus from other members of Neisseria genus can be done by determining the ability of the species to ferment glucose, maltose, sucrose, and lactose:

Neisseria sp.
Glucose
Maltose
Sucrose
Lactose
meningitidis
+
+
-
-
gonorrhoeae
+
-
-
-
lactamica
+
+
-
+
Other nonpathogens
+/-
+/-
+/-
-



-Organisms are nonencapsulated but piliated. Pilli are antiphagocytic and associated with the virulence of the genital strains. They mediate attachement of the organism to epithelial and mucosal cells. The expression may be turned on or off as according to DNA rearrangement. Antigenic variation (altering of surface proteins in order to evade a host immune response) of the pilus involves intragenic recombination and gene conversion in which each genococcal cell caries different DNA sequences. These represent portions of the pilus and so different possible antigenic types. Immunorecessive domains are critically associated with attachement.
-Outer membrane proteins (OMPs):
1. Protein I: major OMP; functions as a porin in complex with Protein III; those with high molecular weight Protein I are associated with primary disease; those with low molecular weight protein I are associated with disseminated disease.
2. Protein II: opacity protein-presence of opaque gonococcal colonies; mediates attachement to host cells along with pilli; can undergo extensive antigenic variation=ability to evade the immune response but also cause repeated infection.
3. Protein III: does not show the antigenic diversity; appears to be the binding site for IgG blocking antibody-->this prevents the functioning of complement mediated bactericidal antibody and this contributes to dissemination if the disease.
-Lipooligosacharides (LOS): has lower molecular weight than lipopolysacharides (LPS) and is considered as a pottential cause of fallopian tube demage in patients with salpingitis. LOS attracts polymorphonuclear leukocytes to the primary site of infection.
*Primary and invasive disease strains are usually sensitive to killing by normal human serum and relatively resistant to penicillin.
*Disseminated gonococcal infection strains - a high degree of penicillin susceptibility and a serum-resistance are often seen in patients
*Surface-modifying factors and mechanisms of action-contribute to pathogenicity of the organism and the outcome of the disease process.
*Extracellular product - organism produces IgA1 protease which inactivates IgA facilitaing to gonococci adherence (Murray et al. 2009).





Epidemiology


Neisseria gonorrhoeae is a microorganism causing millions of infections worldwide.
It causes local infections as well as bacteraemic disease, which is easily mistaken
for other conditions and therefore recognized and treated late. Unlike other viral
F2_large.jpg
infections of genital tract, gonorrhoea has fallen in many developed countries in
recent years. The decline was observed mainly in patients over 25 years of age. In
younger age groups, mostly homosexual males, the incidence has started to
increase again after a period of decline during the late 1980`s. This suggests
insufficient prevention among adolescents.
The organism has no special predilection for race, color, creed or socioeconomic
class .








............................ .................................................................................................................Diagram taken from http://sti.bmj.com/content/79/2/116/F2.large.jpg



Disease


Neisseria gonorrhoeae causes Gonorrhoeae infection. It is a sexually transmitted diesease spread through contact with the penis, vagina, mouth, or anus.Gonococci adhere and penetrate columnar epithelial cells, and multiply on the basement membrane. Adherence is facilitated through opa proteins and pili. The most common site of infection is the urogenital tract, however anorectal, pharyngeal, and conjunctival areas may also be affected (mouth, throuat, nose, anus). Common infections include urethritis, cervicitis, salpingitis, pelvic inflammatory disease, proctitis, conjunctivitis and pharyngitis. Severe, mostly untreated cases, may lead to disseminated gonococcal infections, endocarditis, and meningitis in both men an women; and in women only, to pelvic inflammatory disease. Gonorrhea can also be spread from mother to baby during delivery. This can cause blindness, joint infection, or a life-threatening blood infection in the infant (Wong, 2009; Murray et al., 2009).






Transmition

-exclusively exogenous by 1. sexual contact or 2. from an infected pregnant female to the newborn because of passing throught the infected birth canal.
-transmission from fomites (toilet seats, doorknobs..) does not occur.


Symptoms

Urogenital infections

Symptoms typically occur within two to six days. Unlike women, 95% of men are symptomantic.

Females
*Odorless vaginal discharge;
*vaginal bleeding, particularly after intercourse;
*dyspareunia

Physical findings include cervicitis with the cervix tendency to bleed easily when rubbed with a cotton-tipped swab.
Salpingitis may occur as a result of ascending infection (10-20% of all cases) - sympoms vary from no symptoms to severe abdominal pain with a high fever.
This can may lead to infertility in 15 percent of patients. 50% of patients who have three or more episodes of salpingitis develop infertility.

Males
*purulent penile discharge;
*dysuria

N.gonorrhoeae may also cause epididymitis, which can present as unilateral testicular pain without discharge or dysuria.
The epididymis is swollen and tender to palpation, fever may occur.

Anorectal infections

If present,
*anal pruritus and mucopurulent discharge, usually with a bowel movement
*rectal pain, tenesmus, and bleeding are more common in man-man relationship;

Pharyngeal infections

Symptoms are mild or absent.
*the pharynx may be erythematous or have exudates.
*anterior cervical lymphadenopathy may be present(Ryan, 2010)



Diagnosis

Urogenital infections


Females
The nucleic acid amplification test detects gonorrhea infection by endocervical or urine sample which has lower sensitivity.

Males
Culture technique - The sample is obtained using a urethral swab, the physician should milk the penis first.
Nonculture technique - Nucleic acid amplification tests using urine samples.
Both provide similar samples.

Anorectal infections

Nucleic acid amplification tests can detect rectal gonorrhea infections - recomended for screening.
Culture technique.

Pharyngeal infections

Cultures techniques ecomended.

Antibiotic resistance

In the United States 8-10% of gonococcal strains isolated exhibit either single or multiple resistance to antibiotics, especially penicillinase-producing N. gonorrhoeae (PPNG).

*Primary and invasive disease strains are usually sensitive to killing by normal human serum and relatively resistant to penicillin.


Treatment

Since N. gonorrhoeae is resistant to the penicillin family of antibiotics, ceftriaxone (a third-generation cephalosporin is often used.
Co infection with Chlamidia is frequent therefore it important to test for it. Sexual partner should also be checked.




References

Microveda, 2009. Urology. Man. Urethritis, Gonorrhea. Neisseria gonorrhoeae. [video online]. Available at: <http://www.youtube.com/watch?v=gOCffj9IEw4&feature=player_embedded>[Accessed 19 March 2011]. Murray, P.R., Rossenthal, K.S., Pfaller, M.A., 2009. Medical Microbiology.London: Elsevier.
Ryan, K.J., Ray, C.G., 2010. Medical Microbiology. 5th ed. London: Mc Graw Hill.
Wong, B., 2009. Gonococcal infections. [online] E-medicine. Available at: <http://emedicine.medscape.com/article/218059-overview> [Accessed 27 February 2011].
Youth Projects, 2010. Should should know Gonorrohoea. [online]. Available at: <http://www.youtube.com/watch?v=yHzhtCJ6KtI&feature=player_embedded> [Accessed 20 March 2011].


Lucia Janicova
09013418