Gardnerella
Encyclopedia
Gardnerella is a genus
of gram-variable-staining facultative anaerobic bacteria
of which G. vaginalis is the only species
.
Once classified as Haemophilus vaginalis
and afterwards as Corynebacterium vaginalis
, Gardnerella vaginalis grows as small, circular, convex, gray colonies on chocolate agar
; it also grows on HBT agar
. A selective medium for G. vaginalis is colistin
-oxolinic acid
blood agar.
in some women as a result of a disruption in the normal vagina
l microflora
. The resident anaerobic lactobacillus
population in the vagina are responsible for the acidic environment. Once the anaerobes
have supplanted the normal vaginal bacteria, prescription antibiotic
s with anaerobic coverage may have to be given to eliminate the G. vaginalis and allow the balance to be restored.
While typically isolated in genital
cultures, it may also be detected in other samples from blood
, urine
, and pharynx
. G. vaginalis is sexually transmitted. Although G. vaginalis is a major species present in bacterial vaginosis, it can also be isolated from women without any signs or symptoms of infection.
It has a gram-positive cell wall, but because the cell wall is so thin it can appear either gram-positive or gram-negative under the microscope. It is associated microscopically with clue cell
s, which are epithelial cells covered in bacteria. G. vaginalis produces a pore-forming toxin, vaginolysin, which affects only human cells.
Protease
and sialidase enzyme activities frequently accompany G. vaginalis.
.
The effectiveness of treating bacterial vaginosis with antibiotics is well-documented.
, whose symtoms include vaginal discharge, vaginal irritation, and a "fish like" odor. In the "amine whiff test" 10% KOH is added to the discharge, a positive result indicated if a fishy smell is produced. This and other tests can be used to distinguish between vaginal symptoms related to G. vaginalis from those caused by other organisms, such as trichomonas and C. albicans, which require different treatment.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of gram-variable-staining facultative anaerobic bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
of which G. vaginalis is the only species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
.
Once classified as Haemophilus vaginalis
Haemophilus
Not to be confused with Haemophilia.Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria belonging to the Pasteurellaceae family. While Haemophilus bacteria are typically small coccobacilli, they are categorized as pleomorphic bacteria because of the wide range of shapes they...
and afterwards as Corynebacterium vaginalis
Corynebacterium
Corynebacterium is a genus of Gram-positive rod-shaped bacteria. They are widely distributed in nature and are mostly innocuous. Some are useful in industrial settings such as C. glutamicum. Others can cause human disease. C...
, Gardnerella vaginalis grows as small, circular, convex, gray colonies on chocolate agar
Chocolate agar
Chocolate agar - is a non-selective, enriched growth medium. It is a variant of the blood agar plate. It contains red blood cells, which have been lysed by heating very slowly to 56 °C. Chocolate agar is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae...
; it also grows on HBT agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
. A selective medium for G. vaginalis is colistin
Colistin
Colistin is a polymyxin antibiotic produced by certain strains of Bacillus polymyxa var. colistinus. Colistin is a mixture of cyclic polypeptides colistin A and B. Colistin is effective against most Gram-negative bacilli and is used as a lingerdoodle. It is one of the last-resort antibiotics for...
-oxolinic acid
Oxolinic acid
Oxolinic acid is a quinolone antibiotic developed in Japan in the 1970s. Dosages 12-20mg/kg orally administered for five to ten days. The antibiotic works by inhibiting the enzyme DNA gyrase. It also acts as a dopamine reuptake inhibitor and has stimulant effects in mice....
blood agar.
Clinical significance
Gardnerella vaginalis is a facultatively anaerobic gram-variable rod that can cause bacterial vaginosisBacterial vaginosis
Bacterial vaginosis or less commonly vaginal bacteriosis is a disease of the vagina caused by bacteria. The U.S. Centers for Disease Control and Prevention states it is not clear what role sexual activity plays in the development. However, it is known that BV is associated with having a new sex...
in some women as a result of a disruption in the normal vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
l microflora
Flora (microbiology)
In microbiology, flora refers to the collective bacteria and other microorganisms in an ecosystem . While the term microflora is widely used, it is technically a misnomer since the word root flora pertains to the kingdom plantae...
. The resident anaerobic lactobacillus
Lactobacillus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic rod-shaped bacteria. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign...
population in the vagina are responsible for the acidic environment. Once the anaerobes
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
have supplanted the normal vaginal bacteria, prescription antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
s with anaerobic coverage may have to be given to eliminate the G. vaginalis and allow the balance to be restored.
While typically isolated in genital
Sex organ
A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive...
cultures, it may also be detected in other samples from blood
Blood
Blood is a specialized bodily fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells....
, urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
, and pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
. G. vaginalis is sexually transmitted. Although G. vaginalis is a major species present in bacterial vaginosis, it can also be isolated from women without any signs or symptoms of infection.
It has a gram-positive cell wall, but because the cell wall is so thin it can appear either gram-positive or gram-negative under the microscope. It is associated microscopically with clue cell
Clue cell
Clue cells are epithelial cells of the vagina that get their distinctive stippled appearance by being covered with bacteria.They are a medical sign of bacterial vaginosis, particularly that caused by Gardnerella vaginalis, a group of Gram-variable bacteria...
s, which are epithelial cells covered in bacteria. G. vaginalis produces a pore-forming toxin, vaginolysin, which affects only human cells.
Protease
Protease
A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein....
and sialidase enzyme activities frequently accompany G. vaginalis.
Treatment
One method of antibiotic treatment is metronidazoleMetronidazole
Metronidazole is a nitroimidazole antibiotic medication used particularly for anaerobic bacteria and protozoa. Metronidazole is an antibiotic, amebicide, and antiprotozoal....
.
The effectiveness of treating bacterial vaginosis with antibiotics is well-documented.
Symptoms
Gardnerella vaginalis may be associated with a condition called bacterial vaginosisBacterial vaginosis
Bacterial vaginosis or less commonly vaginal bacteriosis is a disease of the vagina caused by bacteria. The U.S. Centers for Disease Control and Prevention states it is not clear what role sexual activity plays in the development. However, it is known that BV is associated with having a new sex...
, whose symtoms include vaginal discharge, vaginal irritation, and a "fish like" odor. In the "amine whiff test" 10% KOH is added to the discharge, a positive result indicated if a fishy smell is produced. This and other tests can be used to distinguish between vaginal symptoms related to G. vaginalis from those caused by other organisms, such as trichomonas and C. albicans, which require different treatment.