''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of
Gram-negative diplococci
A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the form of two joined cells.
Types
Examples of gram-negative diplococci are '' Neisseria spp.'' and ''Moraxella catarrhalis
''Moraxella catarrhal ...
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
isolated by
Albert Neisser
Albert Ludwig Sigesmund Neisser (22 January 1855, Schweidnitz – 30 July 1916, Breslau) was a German physician who discovered the causative agent ( pathogen) of gonorrhea, a strain of bacteria that was named in his honour (''Neisseria gonorrh ...
in 1879.
It causes the
sexually transmitted
Sexually transmitted infections (STIs), also referred to as sexually transmitted diseases (STDs) and the older term venereal diseases, are infections that are spread by sexual activity, especially vaginal intercourse, anal sex, and oral ...
genitourinary infection
gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia,
septic arthritis, and gonococcal ophthalmia neonatorum.
It is
oxidase positive and aerobic, and it survives
phagocytosis and grows inside
neutrophil
Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying ...
s.
Culturing it requires carbon dioxide supplementation and enriched agar (
chocolate agar) with various antibiotics (
Thayer–Martin). It exhibits
antigenic variation through
genetic recombination of its
pili Pili may refer to:
Common names of plants
* '' Canarium ovatum'', a Philippine tree that is a source of the pili nut
* ''Heteropogon contortus'', a Hawaiian grass used to thatch structures
Places
* Pili, Camarines Sur, is a municipality in the ...
and surface proteins that interact with the
immune system
The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...
.
Sexual transmission is through vaginal, anal, or oral sex.
Sexual transmission may be prevented through the use of barrier protection.
Perinatal transmission may occur during childbirth, and may be prevented by antibiotic treatment of the mother before birth and the application of antibiotic eye gel on the eyes of the newborn.
After an episode of gonococcal infection, infected persons do not develop immunity to future infections. Reinfection is possible due to ''N. gonorrhoeae's'' ability to evade the immune system by varying its surface proteins.
''N. gonorrhoeae'' can cause infection of the genitals, throat, and eyes.
Asymptomatic infection is common in males and females.
Untreated infection may spread to the rest of the body (disseminated gonorrhea infection), especially the joints (septic arthritis). Untreated infection in women may cause
pelvic inflammatory disease and possible infertility due to the resulting scarring.
Diagnosis is through
culture,
Gram stain, or
nucleic acid tests, such as
polymerase chain reaction
The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...
, of a urine sample, urethral swab, or cervical swab.
Chlamydia co-testing and testing for other STIs is recommended due to high rates of co-infection.
Microbiology
''
Neisseria'' species are
fastidious, Gram-negative cocci that require nutrient supplementation to grow in laboratory cultures. ''Neisseria'' spp. are facultatively intracellular and typically appear in pairs (diplococci), resembling the shape of coffee beans. ''Neisseria'' is non-spore-forming, capable of moving using
twitching motility, and an
obligate aerobe
An obligate aerobe is an organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to metabolise substances, like sugars or fats, to obtain energy. In this type of respiration, oxygen serves as the terminal ...
(requires oxygen to grow). Of the 11 species of ''Neisseria'' that colonize humans, only two are pathogens. ''N. gonorrhoeae'' is the causative agent of
gonorrhea and ''
N. meningitidis'' is one cause of bacterial meningitis.
Culture and identification
''N. gonorrhoeae'' is usually isolated on
Thayer–Martin agar
Thayer–Martin agar (or Thayer–Martin medium, or VPN agar) is a Mueller–Hinton agar with 5% chocolate sheep blood and antibiotics. It is used for culturing and primarily isolating pathogenic ''Neisseria'' bacteria, including ''Neisseria gonor ...
(or VPN) agar in an atmosphere enriched with 3-7% carbon dioxide.
Thayer–Martin agar is a chocolate
agar plate (heated blood agar) containing nutrients and
antimicrobials (
vancomycin
Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infection ...
,
colistin,
nystatin, and
trimethoprim). This agar preparation facilitates the growth of ''Neisseria'' species while inhibiting the growth of contaminating bacteria and fungi. Martin Lewis and
New York City agar are other types of selective chocolate agar commonly used for ''Neisseria'' growth.
''N. gonorrhoeae'' is
oxidase positive (possessing cytochrome c oxidase) and
catalase positive (able to convert hydrogen peroxide to oxygen).
When incubated with the carbohydrates lactose,
maltose,
sucrose, and
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
, ''N. gonorrhoeae'' will oxidize only the glucose.
Surface molecules
On its surface, ''N. gonorrhoeae'' bears hair-like
pili Pili may refer to:
Common names of plants
* '' Canarium ovatum'', a Philippine tree that is a source of the pili nut
* ''Heteropogon contortus'', a Hawaiian grass used to thatch structures
Places
* Pili, Camarines Sur, is a municipality in the ...
, surface proteins with various functions, and sugars called
lipooligosaccharides. The pili mediate adherence, movement, and DNA exchange. The Opa proteins interact with the immune system, as do the
porins. Lipooligosaccharide (LOS) is an
endotoxin that provokes an immune response. All are
antigen
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respon ...
ic and all exhibit
antigenic variation (see below). The pili exhibit the most variation. The pili, Opa proteins, porins, and even the LOS have mechanisms to inhibit the immune response, making asymptomatic infection possible.
Dynamic
polymer
A polymer (; Greek '' poly-'', "many" + '' -mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
ic protein filaments called
type IV pili allow ''N. gonorrhoeae'' to adhere to and move along surfaces. To enter the host the bacteria uses the pili to adhere to and penetrate mucosal surfaces.
The pili are a necessary virulence factor for ''N. gonorrhoeae''; without them, the bacterium is unable to cause infection.
To move, individual bacteria use their pili like a grappling hook: first, they are extended from the cell surface and attach to a
substrate. Subsequent pilus retraction drags the cell forward. The resulting movement is referred to as twitching motility. ''N. gonorrhoeae'' is able to pull 100,000 times its own weight, and the pili used to do so are amongst the strongest biological motors known to date, exerting one
nanonewton. The PilF and PilT
ATPase proteins are responsible for powering the extension and retraction of the type IV pilus, respectively. The adhesive functions of the gonococcal pilus play a role in