Peptostreptococcus is a genus of anaerobic, Gram-positive, non-spore forming bacteria. The cells are small, spherical, and can occur in short chains, in pairs or individually. They typically move using cilia.[2]Peptostreptococcus are slow-growing bacteria with increasing resistance to antimicrobial drugs.[3]Peptostreptococcus is a normal inhabitant of the healthy lower reproductive tract of women.[4][5]
Pathogenesis
Peptostreptococcus species are commensal organisms in humans, living predominantly in the mouth, skin, gastrointestinal, vagina and urinary tracts, and are members of the gut microbiota. Under immunosuppressed or traumatic conditions these organisms can become pathogenic, as well as septicemic, harming their host. Peptostreptococcus can cause brain, liver, breast, and lung abscesses, as well as generalized necrotizing soft tissue infections. They participate in mixed anaerobic infections, a term which is used to describe infections that are caused by multiple bacteria that do not require or may even be harmed by oxygen.[6]
They are isolated with high frequency from all specimen sources. Anaerobic gram-positive cocci such as Peptostreptococcus are the second most frequently recovered anaerobes and account for approximately one quarter of anaerobic isolates found. Most often Anaerobic gram-positive cocci are usually recovered mixed in with other anaerobic or aerobic bacteria from various infections at different sites of the human body. This contributes to the difficulty of isolating Peptostreptococcus organisms.[8]
Infections
Peptostreptococcus species that are found in clinical infections were once part of the genus formerly known as Peptococcus. Peptostreptococcus is the only genus among anaerobic gram-positive cocci that is encountered in clinical infections. As such, Peptostreptococcus species are viewed as being clinically significant anaerobic cocci. Other similar clinically significant anaerobic cocci include Veillonella species (gram-negative cocci), and microaerophilic streptococci (aerotolerant). Anaerobic gram-positive cocci include various clinically significant species of the genus Peptostreptococcus.[9]
The species of anaerobic gram-positive cocci isolated most commonly include Peptostreptococcus magnus, Peptostreptococcus asaccharolyticus, Peptostreptococcus anaerobius, Peptostreptococcus prevotii, and Peptostreptococcus micros.[citation needed]
Anaerobic gram-positive cocci that produce large amounts of lactic acid during the process of carbohydrate fermentation were reclassified as Streptococcus parvulus and Streptococcus morbillorum from Peptococcus or Peptostreptococcus. Most of these organisms are anaerobic, but some are microaerophilic.[citation needed]
Due to a large amount of new research done on the human microbe and more information on bacteria, many species of bacteria have been renamed and re-classified. Based on DNA homology and whole-cell polypeptide-pattern study findings supported by phenotypic characteristics, the DNA homology group of microaerobic streptococci that was formerly known as Streptococcus anginosus or Streptococcus milleri is now composed of three distinct species: S anginosus, Streptococcus constellatus, and Streptococcus intermedius. The microaerobic species S morbillorum was transferred into the genus Gemella. A new species within the genus Peptostreptococcus is Peptostreptococcus hydrogenalis; it contains the indole-positive, saccharolytic strains of the genus.[10]
Peptostreptococcus infections occur in/on all body sites, including the CNS, head, neck, chest, abdomen, pelvis, skin, bone, joint, and soft tissues. Adequate therapy must be taken against infections, or it could result in clinical failures. Peptostreptoccocci are often overlooked and they are very difficult to isolate, appropriate specimen collection is required. Peptostreptococci grow slowly which makes them increasingly resistant to antimicrobrials.[9]
The most common Peptostreptococcus species found in infections are P. magnus (18% of all anaerobic gram-positive cocci and microaerophilic streptococci), P asaccharolyticus (17%), P anaerobius (16%), P prevotii (13%), P micros (4%), Peptostreptococcus saccharolyticus (3%), and Peptostreptococcus intermedius (2%).[11]
P magnus were highly recovered in bone and chest infections. P asaccharolyticus and P anaerobius and the highest recovery rate in obstetrical/gynecological and respiratory tract infections and wounds. When anaerobic and facultative cocci were recovered most of the infection were polymicrobial. Most patients from whom microaerophilic streptococci were recovered in pure culture had abscesses (e.g., dental, intracranial, pulmonary), bacteremia, meningitis, or conjunctivitis. P. Magnus is the most commonly isolated anaerobic cocci and is often recovered in pure culture. Other common Peptostreptococci in the different infectious sites are P anaerobius which occurs in oral infections; P micros in respiratory tract infection.s, P magnus, P micros, P asaccharolyticus, Peptostreptococcus vaginalis, and P anaerobius in skin and soft tissue infections; P magnus and P micros in deep organ abscesses; P magnus, P micros, and P anaerobius in gastrointestinal tract–associated infections; P magnus, P micros, P asaccharolyticus, P vaginalis, P tetradius, and P anaerobius in female genitourinary infections; and P magnus, P asaccharolyticus, P vaginalis, and P anaerobius in bone and joint infections and leg and foot ulcers.[12]
Many infections caused by peptostreptococcus bacteria are synergistic. Bacterial synergy, the presence of which is determined by mutual induction of sepsis enhancement, increased mortality, increased abscess inducement, and enhancement of the growth of the bacterial components in mixed infections, is found between anaerobic gram-positive cocci and their aerobic and anaerobic counterparts. The ability of anaerobic gram-positive cocci and microaerophilic streptococci to produce capsular material is an important virulence mechanism, but other factors may also influence the interaction of these organisms in mixed infections.[13]
Although anaerobic cocci can be isolated from infections at all body sites, a predisposition for certain sites has been observed. In general, Peptostreptococcus species, particularly P magnus, have been recovered more often from subcutaneous and soft tissue abscesses and diabetes-related foot ulcers than from intra-abdominal infections. Peptostreptococcus infections occur more often in chronic infections.[9]
Frequency of infections
It is difficult to determine the exact frequency of peptostreptococcus infections because of inappropriate collection methods, transportation, and specimen cultivation. Peptostreptococcus infections are most commonly found in patients who have had or have chronic infections. Patients who have predisposing conditions are shown to have 5% higher recovery rate of the bacteria in blood cultures.[14]
Of all anaerobic bacteria recovered at hospitals from 1973 to 1985, anaerobic gram-positive cocci accounted for 26% of it. The infected sited where these organisms were found in the greatest abundance were obstetrical and gynecological sites (35%), bones (39%) cysts (40%), and ears (53%). Occasionally found in other places such as abdomen, lymph nodes, bile, and eyes.[14]
Frequency of infections is greater in developing countries because treatment is often slow, or it is impossible to get the adequate treatment, but mortality due to peptostreptococcus infections have decreased in the last 30 years and will continue to do so due to better treatment.[citation needed]
All ages are susceptible to peptostreptococcus infections, however children are more likely to get head and neck infections.[citation needed]
Infection types
Skin and soft tissue infections
Anaerobic gram-positive cocci and microaerophilic streptococci are often recovered in polymicrobial skin and soft tissue infections, such as gangrene, fasciitis, ulcers, diabetes-related foot infections, burns, human or animal bites, infected cysts, abscesses of the breast, rectum, and anus. Anaerobic gram-positive cocci and microaerophilic streptococci are generally found mixed with other aerobic and anaerobic bacteria that originate from the mucosal surface adjacent to the infected site or that have been inoculated into the infected site.[citation needed]
Peptostreptococcus spp. can cause infections such as gluteal decubitus ulcers, diabetes-related foot infections, and rectal abscesses. Anaerobic gram-positive cocci and microaerophilic streptococci are part of the normal skin microbiota, so it is hard to avoid contamination by these bacteria when obtaining specimens.[8][9]
CNS infections
CNS infections can be isolated from subdural empyema and brain abscesses which are a result of chronic infections. Also isolated from sinuses, teeth and mastoid. 46% of 39 brain abscesses in one study showed anaerobic gram-positive cocci and microaerophilic streptococci.[8][9]
Upper respiratory tract and dental infections
There is a high rate of anaerobic cocci colonization which accounts for the organisms significance in these infections. Anaerboci gram-positive cocci and micraerophilic streptococci are often recovered in these infections. They have been recovered in 15% of patients with chronic mastoiditis. When Peptostreptococci and other anaerobes predominate, aggressive treatment of acute infection can prevent chronic infection. When the risk of anaerobic infection is high, as with intra-abdominal and post-surgical infections, proper antimicrobial prophylaxis may reduce the risk 90% of the time, other organisms were mixed in with the anaerobic gram-positive cocci and microaerophilic streptococci. This includes streptococcus species, and staphylococcus aureus.[8][9] Peptostreptococcus micros has a moderate association with periodontal disease.[citation needed]
Bacteremia and endocarditis
Peptostreptococci can cause fatal endocarditis, paravalvular abscess, and pericarditis. The most frequent source of bacteremia due to Peptostreptococcus are infections of the oropharynx, lower respiratory tract, female genital tract, abdomen, skin, and soft tissues. Recent gynecological surgery, immunosuppression, dental procedures, infections of the female genital tract, abdominal and soft tissue along with gastrointestinal surgery are predisposing factors for bacteremia due to peptostreptococcus.[citation needed]
Microaerophilic streptococci typically account for 5-10% of cases of endocarditis; however, Peptostreptococci have only rarely been isolated.[8][9]
Anaerobic pleuropulmonary infections
Anaerobic gram-positive cocci and microaerophilic streptococci are most frequently found in aspiration pneumonia, empyema, lung abscesses, and mediastinitis. These bacteria account for 10-20% of anaerobic isolated recovered from pulmonary infections. It is difficult to obtain appropriate culture specimens. It requires a direct lung puncture, or the use of trans-tracheal aspiration.[8][9]
Abdominal infections
Anaerobic gram-positive cocci are part of the normal gastrointestinal microbiota. They are isolated in approximately 20% of specimens from intra-abdominal infections, such as peritonitis. Found in abscesses of the liver, spleen, and abdomen. Like in upper respiratory tract and dental infections, anaerobic gram-positive cocci are recovered mixed with other bacteria. In this case they are mixed with organisms of intestinal origin such as E coli, bacteroides fragilis group, and clostridium species.[8][9]
Female pelvic infections
Anaerobic gram-positive cocci are frequently isolated from anaerobically infected bones and joints., they accounted for 40% of anaerobic isolates of osteomyelitis caused by anaerobic bacteria and 20% of anaerobic isolates of arthritis caused by anaerobic bacteria. P magnus and P prevotii are the predominant bone and joint isolates. Management of these infections requires prolonged courses of antimicrobials and is enhanced by removal of the foreign material.[8][9]
When Peptostreptococci and other anaerobes predominate, aggressive treatment of acute infection can prevent chronic infection. When the risk of anaerobic infection is high, as with intra-abdominal and post-surgical infections, proper antimicrobial prophylaxis may reduce the risk. Therapy with antimicrobials (e.g., aminoglycosides, trimethoprim-sulfamethoxazole, older quinolones) often does not eradicate anaerobes.[citation needed]
Taxonomy
As of 2022, there are 5 species validly published in the genus Peptostreptococcus, with several species formerly being described, that have been moved to a more accurate genus.
Brain abscess is an abscess caused by inflammation and collection of infected material, coming from local or remote infectious sources, within the brain tissue. The infection may also be introduced through a skull fracture following a head trauma or surgical procedures. Brain abscess is usually associated with congenital heart disease in young children. It may occur at any age but is most frequent in the third decade of life.
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 symptoms. Signs and symptoms, when present, may include lower abdominal pain, vaginal discharge, fever, burning with urination, pain with sex, bleeding after sex, or irregular menstruation. Untreated PID can result in long-term complications including infertility, ectopic pregnancy, chronic pelvic pain, and cancer.
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Bacillota. Cell division in streptococci occurs along a single axis, so as they grow, they tend to form pairs or chains that may appear bent or twisted. This differs from staphylococci, which divide along multiple axes, thereby generating irregular, grape-like clusters of cells. Most streptococci are oxidase-negative and catalase-negative, and many are facultative anaerobes.
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic or beta-hemolytic, aerotolerant anaerobic member of the genus Streptococcus. They are usually found in pairs (diplococci) and do not form spores and are non motile. As a significant human pathogenic bacterium S. pneumoniae was recognized as a major cause of pneumonia in the late 19th century, and is the subject of many humoral immunity studies.
A coccus 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. Coccus refers to the shape of the bacteria, and can contain multiple genera, such as staphylococci or streptococci. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile.
The viridans streptococci are a large group of commensal streptococcal Gram-positive bacteria species that are α-hemolytic, producing a green coloration on blood agar plates, although some species in this group are actually γ-hemolytic, meaning they produce no change on blood agar. The pseudo-taxonomic term "Streptococcus viridans" is often used to refer to this group of species, but writers who do not like to use the pseudotaxonomic term prefer the terms viridans streptococci, viridans group streptococci (VGS), or viridans streptococcal species.
Mastoiditis is the result of an infection that extends to the air cells of the skull behind the ear. Specifically, it is an inflammation of the mucosal lining of the mastoid antrum and mastoid air cell system inside the mastoid process. The mastoid process is the portion of the temporal bone of the skull that is behind the ear. The mastoid process contains open, air-containing spaces. Mastoiditis is usually caused by untreated acute otitis media and used to be a leading cause of child mortality. With the development of antibiotics, however, mastoiditis has become quite rare in developed countries where surgical treatment is now much less frequent and more conservative, unlike former times.
Lung abscess is a type of liquefactive necrosis of the lung tissue and formation of cavities containing necrotic debris or fluid caused by microbial infection.
Streptococcus bovis is a species of Gram-positive bacteria that in humans is associated with urinary tract infections, endocarditis, sepsis, and colorectal cancer. S. gallolyticus is commonly found in the alimentary tract of cattle, sheep, and other ruminants, and may cause ruminal acidosis or feedlot bloat. It is also associated with spontaneous bacterial peritonitis, a frequent complication occurring in patients affected by cirrhosis. Equivalence with Streptococcus equinus has been contested.
Gemella morbillorum is a species of bacteria within the genus Gemella. It is a facultative anaerobic Gram positive coccus usually preferring capnophilic or microaerophilic environments. From its discovery in 1917 until 1988, it was known as Streptococcus morbillorum. The name change followed closer examination with DNA filter hybridization which found it was very close to the species Gemella haemolysans.
Alcaligenes is a genus of Gram-negative, aerobic, rod-shaped bacteria. The species are motile with amphitrichous flagella and rarely nonmotile. It is a genus of non-fermenting bacteria. Additionally, some strains of Alcaligenes are capable of anaerobic respiration, but they must be in the presence of nitrate or nitrite; otherwise, their metabolism is respiratory and never fermentative; The genus does not use carbohydrates. Strains of Alcaligenes are found mostly in the intestinal tracts of vertebrates, decaying materials, dairy products, water, and soil; they can be isolated from human respiratory and gastrointestinal tracts and wounds in hospitalized patients with compromised immune systems. They are occasionally the cause of opportunistic infections, including nosocomial sepsis.
Bacteroides fragilis is an anaerobic, Gram-negative, pleomorphic to rod-shaped bacterium. It is part of the normal microbiota of the human colon and is generally commensal, but can cause infection if displaced into the bloodstream or surrounding tissue following surgery, disease, or trauma.
Arcanobacterium haemolyticum is a species of bacteria classified as a gram-positive bacillus. It is catalase-negative, aerobic, beta-hemolytic, and not motile. It has been known to cause head and neck infections, pharyngitis, and sinusitis.
Vaginal flora, vaginal microbiota or vaginal microbiome are the microorganisms that colonize the vagina. They were discovered by the German gynecologist Albert Döderlein in 1892 and are part of the overall human flora. The amount and type of bacteria present have significant implications for an individual's overall health. The primary colonizing bacteria of a healthy individual are of the genus Lactobacillus, such as L. crispatus, and the lactic acid they produce is thought to protect against infection by pathogenic species.
Anaerobic infections are caused by anaerobic bacteria. Obligately anaerobic bacteria do not grow on solid media in room air ; facultatively anaerobic bacteria can grow in the presence or absence of air. Microaerophilic bacteria do not grow at all aerobically or grow poorly, but grow better under 10% carbon dioxide or anaerobically. Anaerobic bacteria can be divided into strict anaerobes that can not grow in the presence of more than 0.5% oxygen and moderate anaerobic bacteria that are able of growing between 2 and 8% oxygen. Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen.
Peptococcus is a Gram-positive bacterium genus in the family Peptococcaceae.
Peptostreptococcus anaerobius is a species of bacteria belonging to the Peptostreptococcus genus of anaerobic, Gram-positive, non-spore forming bacteria. The cells are small, spherical, and can occur in short chains, in pairs or individually. Peptostreptococcus are slow-growing bacteria sometimes resistance to antimicrobial drugs.
Peptoniphilus is a genus of bacteria in the phylum Bacillota (Bacteria).
Finegoldia is a genus of Gram-positive bacteria. They are anaerobic cocci of the class Clostridia, with Finegoldia magna being the type species. F. magna was formerly known, along with several other Gram-positive anaerobic cocci (GPACs), as Peptostreptococcus magnus, but was moved into its own genus in 1999. The name is in honor of Sydney M. Finegold, an American microbiologist, while magna is Latin for large. It is an opportunistic human pathogen that normally colonizes skin and mucous membranes. It is often seen in biofilms on chronic ulcers such as in diabetic foot or decubitus ulcers. Most surveys have found it to be susceptible to penicillins, carbapenems and metronidazole, though resistant strains have been identified. Resistance to clindamycin is common and has been seen in over 10% of isolates in the US. One review stated that "the combination of diminished antimicrobial susceptibility, its prevalence, and the described virulence factors gives F. magna a special position among the GPAC."
Anaerococcus is a genus of bacteria. Its type species is Anaerococcus prevotii. These bacteria are Gram-positive and strictly anaerobic. The genus Anaerococcus was proposed in 2001. Its genome was sequenced in August 2009. The genus Anaerococcus is one of six genera classified within the group GPAC. These six genera are found in the human body as part of the commensal human microbiota.
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