''Streptococcus bovis'' (''S. bovis'') is a species of

Gram-positive bacteria In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bact ...

that in humans is associated with urinary tract infections,

endocarditis Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the ...

sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...

, Ryan K.J. and C.G. Ray CG (editors). 2004. ''Sherris Medical Microbiology'' (4th ed.). McGraw Hill. . and

colorectal cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel m ...

. ''S. gallolyticus'' is commonly found in the alimentary tract of cattle, sheep, and other

ruminant Ruminants (suborder Ruminantia) are ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, principally ...

s, and may cause ruminal acidosis or feedlot bloat. It is also associated with

spontaneous bacterial peritonitis Spontaneous bacterial peritonitis (SBP) is the development of a bacterial infection in the peritoneum, despite the absence of an obvious source for the infection. It is specifically an infection of the ascitic fluid – an increased volume of pe ...

, a frequent complication occurring in patients affected by cirrhosis. Equivalence with ''

Streptococcus equinus ''Streptococcus equinus'' is a Gram-positive, nonhemolytic, non pathogenic, lactic acid bacterium of the genus ''Streptococcus''. It is the principal ''Streptococcus'' found in the alimentary canal of a horse, and makes up the majority of the b ...

'' has been contested.

''S. bovis'' group

The ''S. bovis'' group includes ''S. equinus'', ''S. gallolyticus'', ''S. infantarius'', and other closely related species; they are the nonenterococcal group D streptococci. Members of this group are esculin positive, 6.5% salt negative, sorbitol negative and produce acetoin. Isolates from the ''S. bovis'' group are most frequently encountered in blood cultures from patients with colon cancer. However, ''S. bovis'' group organisms (especially ''S. gallolyticus'' subsp. ''gallolyticus'' and ''S. infantarius'' subsp. ''coli'') have been associated with endocarditis (3). Although infection with S. bovis group organisms occurs with higher frequency in adults than in pediatric patients, these organisms have been reported to cause neonatal sepsis and meningitis (20).

Classification

''S. bovis'' is a catalase-negative and

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 ...

-negative, nonmotile, non-

sporulating In biology, a spore is a unit of sexual reproduction, sexual or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of ...

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...

lactic acid bacterium Lactobacillales are an order of gram-positive, low-GC, acid-tolerant, generally nonsporulating, nonrespiring, either rod-shaped (bacilli) or spherical (cocci) bacteria that share common metabolic and physiological characteristics. These bact ...

that grows as pairs or chains of

cocci A coccus (plural cocci) is any bacterium or archaeon that has a spherical, ovoid, or generally round shape. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spiral ( of whi ...

. It is a member of the Lancefield group D streptococci. Most strains are gamma-hemolytic (non-hemolytic), but some also display

alpha-hemolytic Hemolysis (from Greek αιμόλυση, meaning 'blood breakdown') is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particular ...

activity on

sheep Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus ''Ovis'', in everyday usage it almost always refers to domesticated s ...

blood agar plate An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics. Individual microorganisms placed on the plate wil ...

s. Strep bovis is a non-enterococci. Biochemical Tests mannitol salt: negative bile esculin: negative MR/VP: positive/negative nutrient gelatin: negative starch: positive DNase: negative

Human infection

Entry

The main portal of entry for human infection of ''S. bovis'' bacteremia is the

gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...

, but in some cases, entry is through the urinary tract, the hepatobiliary tree, or the oropharynx.

Role in disease

''S. bovis'' is a human pathogen that has been implicated as a causative agent of

urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...

s, and more rarely,

and neonatal

meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...

. ''S. bovis'' has long been associated with

; however, not all genospecies are associated equally. A 2011 meta-analysis on the association between ''S. bovis'' biotypes and colonic adenomas/carcinomas revealed that patients with ''S. bovis'' biotype I infection had a strongly increased risk of having colorectal cancer (pooled odds ratio: 7.26; 95% confidence interval: 3.94–13.36), compared to ''S. bovis'' biotype II-infected patients. This analysis suggests ''S. bovis'' should no longer be regarded as a single bacterial entity in clinical practice. Only ''Streptococcus gallolyticus'' (''S. bovis'' biotype I) infection has an unambiguous association with colonic adenomas/carcinomas (prevalence range: 33–71%) that markedly exceeds the prevalence of colonic (pre-)malignancies in the general population (10–25%). Nevertheless, research has not yet determined that ''S. gallolyticus'' is a causative agent of colorectal cancer, or if pre-existing cancer makes the lumen of the large intestine more hospitable to its outgrowth.

Ruminal effects

When ruminants consume diets high in

starch Starch or amylum is a polymeric carbohydrate consisting of numerous glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants for energy storage. Worldwide, it is the most common carbohydrate in human diets ...

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose, fructose, and galactose. Compound sugars, also called disaccharides or double ...

, these easily fermentable carbohydrates promote the proliferation of ''S. bovis'' in the rumen. Because ''S. bovis'' is a lactic acid bacterium, fermentation of these carbohydrates to

lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natu ...

can cause a dramatic decline in ruminal pH, and subsequent development of adverse conditions such as ruminal acidosis or feedlot bloat.

References

External links

* * {{DEFAULTSORT:Streptococcus Gallolyticus Streptococcaceae Gram-positive bacteria Infectious causes of cancer Bacteria described in 1919