''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of
Gram-negative
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...
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.'' Examples of gram-positiv ...
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 among ...
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 gonorrhoe ...
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 sex ...
genitourinary infection
gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia,
septic arthritis, and gonococcal ophthalmia neonatorum.
It is
oxidase
In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...
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 in ...
s.
Culturing it requires carbon dioxide supplementation and enriched agar (
chocolate agar) with various antibiotics (
Thayer–Martin). It exhibits
antigenic variation
Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of t ...
through
genetic recombination
Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...
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
Pelvic inflammatory disease, also known as pelvic inflammatory disorder (PID), is an infection of the upper part of the female reproductive system, namely the uterus, fallopian tubes, and ovaries, and inside of the pelvis. Often, there may be no ...
and possible infertility due to the resulting scarring.
Diagnosis is through
culture
Culture () is an umbrella term which encompasses the social behavior, institutions, and norms found in human societies, as well as the knowledge, beliefs, arts, laws, customs, capabilities, and habits of the individuals in these groups.Tyl ...
,
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) t ...
, 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 gonorrhoeae with pus cells](https://upload.wikimedia.org/wikipedia/commons/f/ff/Neisseria_gonorrhoeae_with_pus_cells.jpg)
''
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 e ...
(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
''Neisseria meningitidis'', often referred to as meningococcus, is a Gram-negative bacterium that can cause meningitis and other forms of meningococcal disease such as meningococcemia, a life-threatening sepsis. The bacterium is referred to as a ...
'' is one cause of bacterial meningitis.
Culture and identification
![Neisseria gonorrhoeae 01](https://upload.wikimedia.org/wikipedia/commons/f/f5/Neisseria_gonorrhoeae_01.png)
''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 gono ...
(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 infections, ...
,
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 The NYC (New York City) medium or GC ('' Neisseria gonorrhoeae'') medium agar is used for isolating Gonococci.Fauer, Weisburd, Wilson and May, 1973, Health Lab. Sci., 10: 44.
Composition
The agar base is composed of:
''Final pH ( at 25°C) 7 ...
are other types of selective chocolate agar commonly used for ''Neisseria'' growth.
''N. gonorrhoeae'' is
oxidase
In biochemistry, an oxidase is an enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...
positive (possessing cytochrome c oxidase) and
catalase
Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting t ...
positive (able to convert hydrogen peroxide to oxygen).
When incubated with the carbohydrates lactose,
maltose
}
Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two- ...
,
sucrose
Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula .
For human consumption, sucrose is extracted and refined ...
, 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, using ...
, ''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
Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels tha ...
. 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 response. ...
ic and all exhibit
antigenic variation
Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of t ...
(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
ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, SV40 T-antigen, ATP hydrolase, complex V (mitochondrial electron transport), (Ca2+ + Mg2+)-ATPase, HCO3−-ATPase, adenosine triphosphatase) are ...
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