Pathogenic bacteria | |
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Neisseria gonorrhoeae (small red dots) in pus from a man with a urethral discharge (Gram stain) |
Pathogenic bacteria are bacteria that can cause disease. [1] This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and many are beneficial but others can cause infectious diseases. The number of these pathogenic species in humans is estimated to be fewer than a hundred. [2] By contrast, several thousand species are part of the gut flora present in the digestive tract.[ citation needed ]
The body is continually exposed to many species of bacteria, including beneficial commensals, which grow on the skin and mucous membranes, and saprophytes, which grow mainly in the soil and in decaying matter. The blood and tissue fluids contain nutrients sufficient to sustain the growth of many bacteria. The body has defence mechanisms that enable it to resist microbial invasion of its tissues and give it a natural immunity or innate resistance against many microorganisms.
Pathogenic bacteria are specially adapted and endowed with mechanisms for overcoming the normal body defences, and can invade parts of the body, such as the blood, where bacteria are not normally found. Some pathogens invade only the surface epithelium, skin or mucous membrane, but many travel more deeply, spreading through the tissues and disseminating by the lymphatic and blood streams. In some rare cases a pathogenic microbe can infect an entirely healthy person, but infection usually occurs only if the body's defence mechanisms are damaged by some local trauma or an underlying debilitating disease, such as wounding, intoxication, chilling, fatigue, and malnutrition. In many cases, it is important to differentiate infection and colonization, which is when the bacteria are causing little or no harm.
Caused by Mycobacterium tuberculosis bacteria, one of the diseases with the highest disease burden is tuberculosis, which killed 1.4 million people in 2019, mostly in sub-Saharan Africa. [4] Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as Staphylococcus , Streptococcus and Pseudomonas , and foodborne illnesses, which can be caused by bacteria such as Shigella , Campylobacter , and Salmonella . Pathogenic bacteria also cause infections such as tetanus, typhoid fever, diphtheria, syphilis, and leprosy.
Pathogenic bacteria are also the cause of high infant mortality rates in developing countries. [5] A GBD study estimated the global death rates from (33) bacterial pathogens, finding such infections contributed to one in 8 deaths (or ~7.7 million deaths), which could make it the second largest cause of death globally in 2019. [6] [3]
Most pathogenic bacteria can be grown in cultures and identified by Gram stain and other methods. Bacteria grown in this way are often tested to find which antibiotics will be an effective treatment for the infection. For hitherto unknown pathogens, Koch's postulates are the standard to establish a causative relationship between a microbe and a disease.
Each species has specific effect and causes symptoms in people who are infected. Some people who are infected with a pathogenic bacteria do not have symptoms. Immunocompromised individuals are more susceptible to pathogenic bacteria. [7]
Some pathogenic bacteria cause disease under certain conditions, such as entry through the skin via a cut, through sexual activity or through compromised immune function.[ citation needed ]
Some species of Streptococcus and Staphylococcus are part of the normal skin microbiota and typically reside on healthy skin or in the nasopharyngeal region. Yet these species can potentially initiate skin infections. Streptococcal infections include sepsis, pneumonia, and meningitis. [8] These infections can become serious creating a systemic inflammatory response resulting in massive vasodilation, shock, and death. [9]
Other bacteria are opportunistic pathogens and cause disease mainly in people with immunosuppression or cystic fibrosis. Examples of these opportunistic pathogens include Pseudomonas aeruginosa , Burkholderia cenocepacia , and Mycobacterium avium . [10] [11]
Obligate intracellular parasites (e.g. Chlamydophila, Ehrlichia, Rickettsia) are only able to grow and replicate inside other cells. Infections due to obligate intracellular bacteria may be asymptomatic, requiring an incubation period. Examples of obligate intracellular bacteria include Rickettsia prowazekii (typhus) and Rickettsia rickettsii, (Rocky Mountain spotted fever).[ citation needed ]
Chlamydia are intracellular parasites. These pathogens can cause pneumonia or urinary tract infection and may be involved in coronary heart disease. [12]
Other groups of intracellular bacterial pathogens include Salmonella , Neisseria , Brucella , Mycobacterium , Nocardia, Listeria , Francisella , Legionella , and Yersinia pestis . These can exist intracellularly, but can exist outside host cells.[ citation needed ]
Bacterial pathogens often cause infection in specific areas of the body. Others are generalists.
The symptoms of disease appear as pathogenic bacteria damage host tissues or interfere with their function. The bacteria can damage host cells directly or indirectly by provoking an immune response that inadvertently damages host cells, [21] or by releasing toxins. [22]
Once pathogens attach to host cells, they can cause direct damage as the pathogens use the host cell for nutrients and produce waste products. [23] For example, Streptococcus mutans , a component of dental plaque, metabolizes dietary sugar and produces acid as a waste product. The acid decalcifies the tooth surface to cause dental caries. [24]
Endotoxins are the lipid portions of lipopolysaccharides that are part of the outer membrane of the cell wall of gram-negative bacteria. Endotoxins are released when the bacteria lyses, which is why after antibiotic treatment, symptoms can worsen at first as the bacteria are killed and they release their endotoxins. Exotoxins are secreted into the surrounding medium or released when the bacteria die and the cell wall breaks apart. [25]
An excessive or inappropriate immune response triggered by an infection may damage host cells. [1]
Iron is required for humans, as well as the growth of most bacteria. To obtain free iron, some pathogens secrete proteins called siderophores, which take the iron away from iron-transport proteins by binding to the iron even more tightly. Once the iron-siderophore complex is formed, it is taken up by siderophore receptors on the bacterial surface and then that iron is brought into the bacterium. [25]
Bacterial pathogens also require access to carbon and energy sources for growth. To avoid competition with host cells for glucose which is the main energy source used by human cells, many pathogens including the respiratory pathogen Haemophilus influenzae specialise in using other carbon sources such as lactate that are abundant in the human body [26]
Typically identification is done by growing the organism in a wide range of cultures which can take up to 48 hours. The growth is then visually or genomically identified. The cultured organism is then subjected to various assays to observe reactions to help further identify species and strain. [27]
Bacterial infections may be treated with antibiotics, which are classified as bacteriocidal if they kill bacteria or bacteriostatic if they just prevent bacterial growth. There are many types of antibiotics and each class inhibits a process that is different in the pathogen from that found in the host. For example, the antibiotics chloramphenicol and tetracyclin inhibit the bacterial ribosome but not the structurally different eukaryotic ribosome, so they exhibit selective toxicity. [28] Antibiotics are used both in treating human disease and in intensive farming to promote animal growth. Both uses may be contributing to the rapid development of antibiotic resistance in bacterial populations. [29] Phage therapy, using bacteriophages can also be used to treat certain bacterial infections. [30]
Infections can be prevented by antiseptic measures such as sterilizing the skin prior to piercing it with the needle of a syringe and by proper care of indwelling catheters. Surgical and dental instruments are also sterilized to prevent infection by bacteria. Disinfectants such as bleach are used to kill bacteria or other pathogens on surfaces to prevent contamination and further reduce the risk of infection. Bacteria in food are killed by cooking to temperatures above 73 °C (163 °F).[ citation needed ]
Many genera contain pathogenic bacterial species. They often possess characteristics that help to classify and organize them into groups. The following is a partial listing.
Genus | Species | Gram staining | Shape | Oxygen requirement | Intra/Extracellular |
---|---|---|---|---|---|
Bacillus [31] | Positive | Rods | Facultative anaerobic | Extracellular | |
Bartonella [31] | Negative | Rods | Aerobic | Facultative intracellular | |
Bordetella [31] | Negative | Small coccobacilli | Aerobic | Extracellular | |
Borrelia [31] | Negative, stains poorly | Spirochete | Anaerobic | Extracellular | |
Brucella [31] | Negative | Coccobacilli | Aerobic | Intracellular | |
Campylobacter [31] | Negative | Spiral rods [34] coccoid in older cultures [34] | Microaerophilic [34] | Extracellular | |
Chlamydia and Chlamydophila [31] | (not Gram-stained) | Small, round, ovoid | Facultative or strictly aerobic | Obligate intracellular | |
Clostridium [31] | Positive | Large, blunt-ended rods | Obligate anaerobic | Extracellular | |
Corynebacterium [31] | Positive (unevenly) | Rods | Mostly facultative anaerobic | Extracellular | |
Enterococcus [33] [37] | Positive | Cocci | Facultative Anaerobic | Extracellular | |
Escherichia [5] [33] [38] | Negative | Rods | Facultative anaerobic | Extracellular or Intracellular | |
Francisella [31] | Negative | Coccobacillus | Strictly aerobic | Facultative intracellular | |
Haemophilus | Negative | Coccobacilli to long and slender filaments | Facultative anaerobic 5 - 10% CO2 | Extracellular | |
Helicobacter | Negative | Spiral rod | Microaerophile | Extracellular | |
Legionella [31] | Negative, stains poorly | Cocobacilli | Aerobic | Facultative intracellular | |
Leptospira [33] [41] | Negative, stains poorly | Spirochete | Strictly aerobic | Extracellular | |
Listeria [31] | Positive, darkly | Slender, short rods | Facultative Anaerobic | Facultative intracellular | |
Mycobacterium [31] | (none) | Long, slender rods | Aerobic | Intracellular | |
Mycoplasma [31] | (none) | Indistinct 'fried egg' appearance, no cell wall | Mostly facultative anaerobic; M. pneumoniae strictly aerobic | Extracellular | |
Neisseria [33] [42] | Negative | Kidney bean-shaped | Aerobic | Gonococcus: facultative intracellular N. meningitidis: extracellular | |
Pseudomonas [33] [43] | Negative | Rods | Obligate aerobic | Extracellular | |
Rickettsia [31] | Negative, stains poorly | Small, rod-like coccobacillary | Aerobic | Obligate intracellular | |
Salmonella [31] | Negative | Rods | Facultative anaerobic | Facultative intracellular | |
Shigella [33] [44] | Negative | Rods | Facultative anaerobic | Extracellular | |
Staphylococcus [5] | Positive, darkly | Round cocci | Facultative anaerobic | Extracellular, facultative intracellular | |
Streptococcus [31] | Positive | Ovoid to spherical | Facultative anaerobic | Extracellular | |
Treponema [31] | Negative, stains poorly | Spirochete | Aerobic | Extracellular | |
Ureaplasma [5] | Stains poorly [45] | Indistinct, 'fried egg' appearance, no cell wall | Anaerobic | Extracellular | |
Vibrio [33] [46] | Negative | Spiral with single polar flagellum | Facultative anaerobic | Extracellular | |
Yersinia [33] [47] | Negative, bipolarly | Small rods | Facultative anaerobe | Intracellular | |
This is description of the more common genera and species presented with their clinical characteristics and treatments.
Species | Transmission | Diseases | Treatment | Prevention | ||
---|---|---|---|---|---|---|
Actinomyces israelii | Oral flora [48] | Actinomycosis: [48] painful abscesses and cysts MRSA in the mouth, lungs, [49] [50] or gastrointestinal tract. [35] | Prolonged penicillin G and drainage [48] | |||
Bacillus anthracis | Contact with cattle, sheep, goats and horses [51] | Anthrax: pulmonary, gastrointestinal and/or cutaneous symptoms. [48] | In early infection: [52] | Anthrax vaccine [33] | ||
Bacteroides fragilis | Gut flora [48] | Abscesses in gastrointestinal tract, pelvic cavity and lungs [48] | metronidazole [48] | Wound care [54] | ||
Bordetella pertussis | Contact with respiratory droplets expelled by infected human hosts. [33] | Whooping cough [33] [48] | Macrolides [33] such as erythromycin, [33] [48] before paroxysmal stage [48] | Pertussis vaccine, [33] [48] such as in DPT vaccine [33] [48] | ||
Borrelia | B. burgdorferi [33] [48] | Ixodes hard ticks |
| Doxycycline for adults, amoxicillin for children, ceftriaxone for neurological involvement [56] | Wearing clothing that limits skin exposure to ticks. [33] | |
B. recurrentis [58] and others [note 1] | Pediculus humanus corporis body louse (B. recurrentis only) and Ornithodoros soft ticks [58] | Relapsing fever | Penicillin, tetracycline, doxycycline [59] | Avoid areas where ticks are found [58] Better access to washing facilities [58] | ||
Brucella | B. abortus | Direct contact with infected animal [33] | Brucellosis: mainly fever, muscular pain and night sweats | |||
Campylobacter jejuni | Fecal–oral from animals (mammals and fowl) [33] [48] |
| Treat symptoms [33] | Good hygiene [33] | ||
Chlamydia | C. pneumoniae | Atypical pneumonia [48] | None [33] | |||
C. trachomatis | vaginal sex [33] | Trachoma [33] [48] | Erythromycin [33] [48] | Erythromycin or silver nitrate in newborn's eyes [33] | ||
Chlamydophila psittaci | Inhalation of dust with secretions or feces from birds (e.g. parrots) | Psittacosis, mainly atypical pneumonia | - | |||
Clostridium | C. botulinum | Spores from soil, [33] [48] persevere in canned food, smoked fish and honey [48] | Botulism: Mainly muscle weakness and paralysis [48] | Antitoxin [33] [48] | Proper food preservation techniques | |
C. difficile | Gut flora, [33] [48] overgrowing when other flora is depleted [33] | Discontinuing responsible antibiotic [33] [48] | Fecal bacteriotherapy | |||
C. perfringens | Spores in soil [33] [48] | Anaerobic cellulitis [33] [48] | Gas gangrene: Debridement or amputation [33] [48] | Appropriate food handling [33] | ||
C. tetani | Tetanus immune globulin [33] [48] Sedatives [33] | Tetanus vaccine (such as in the DPT vaccine) [33] | ||||
Corynebacterium diphtheriae | respiratory droplets | Diphtheria: Fever, sore throat and neck swelling, potentially narrowing airways. [61] | Horse serum antitoxin | |||
Ehrlichia | E. canis [48] | Dog tick [48] | Ehrlichiosis: [48] headache, muscle aches, and fatigue | |||
Enterococcus | E. faecalis | Part of gut flora, [48] opportunistic or entering through GI tract or urinary system wounds [33] | Bacterial endocarditis, [48] biliary tract infections, [48] urinary tract infections [48] | Ampicillin (combined with aminoglycoside in endocarditis) [48] Vancomycin [33] | No vaccine Hand washing and other nosocomial prevention | |
Escherichia | E. coli (generally) |
| UTI: [33] (resistance-tests are required first) Meningitis: [33]
Diarrhea: [33]
| (no vaccine or preventive drug) [33]
| ||
Enterotoxigenic E. coli (ETEC) |
| |||||
Enteropathogenic E. coli |
| |||||
Enteroinvasive E.coli (EIEC) |
| |||||
Enterohemorrhagic (EHEC), including E. coli O157:H7 |
| |||||
Francisella tularensis | Tularemia: Fever, ulceration at entry site and/or lymphadenopathy. [63] Can cause severe pneumonia. [63] | |||||
Haemophilus influenzae | Meningitis: [33] (resistance-tests are required first)
|
| ||||
Helicobacter pylori |
|
| (No vaccine or preventive drug) [33] | |||
Klebsiella pneumoniae |
|
| ||||
Legionella pneumophila |
|
| (no vaccine or preventive drug) [33] Heating water [33] | |||
Leptospira species |
|
|
| Vaccine not widely used [33] Prevention of exposure [33] | ||
Listeria monocytogenes | (no vaccine) [33]
| |||||
Mycobacterium | M. leprae |
|
| Tuberculoid form: Lepromatous form: |
| |
M. tuberculosis |
|
| (difficult, see Tuberculosis treatment for more details) [33] Standard "short" course: [33]
| |||
Mycoplasma pneumoniae |
| |||||
Neisseria | N. gonorrhoeae |
|
| Uncomplicated gonorrhea: [33]
Ophthalmia neonatorum: | (No vaccine) [33]
| |
N. meningitidis |
| |||||
Pseudomonas aeruginosa | Opportunistic; [48] Infects damaged tissues or people with immunodeficiency. [33] | Pseudomonas infection: [33]
| (no vaccine) [33]
| |||
Nocardia asteroides | In soil [48] | Nocardiosis: [48] Pneumonia, endocarditis, keratitis, neurological or lymphocutaneous infection | TMP/SMX [48] | |||
Rickettsia rickettsii | (no preventive drug or approved vaccine) [33]
| |||||
Salmonella | S typhi |
|
| |||
Other Salmonella species
|
| (No vaccine or preventive drug) [33] | ||||
Shigella | S. sonnei [33] |
|
| |||
Staphylococcus | aureus | Coagulase-positive staphylococcal infections: |
| (no vaccine or preventive drug)
| ||
epidermidis | Human flora in skin, [33] [48] anterior nares [33] and mucous membranes [48] |
| None [33] | |||
saprophyticus | Part of normal vaginal flora [33] | None [33] | ||||
Streptococcus | agalactiae | Human flora in vagina, [33] [48] urethral mucous membranes, [33] rectum [33]
|
|
| None [33] | |
pneumoniae |
|
| ||||
pyogenes |
| No vaccine [33]
| ||||
viridans | Oral flora, [48] penetration through abrasions |
| Penicillin G [48] | |||
Treponema pallidum subspecies pallidum |
| |||||
Vibrio cholerae |
|
|
| |||
Yersinia pestis | Plague: |
|
|
Of the 59 species listed in the table with their clinical characteristics, 11 species (or 19%) are known to be capable of natural genetic transformation. [81] Natural transformation is a bacterial adaptation for transferring DNA from one cell to another. This process includes the uptake of exogenous DNA from a donor cell by a recipient cell and its incorporation into the recipient cell's genome by recombination. Transformation appears to be an adaptation for repairing damage in the recipient cell's DNA. Among pathogenic bacteria, transformation capability likely serves as an adaptation that facilitates survival and infectivity. [81] The pathogenic bacteria able to carry out natural genetic transformation (of those listed in the table) are Campylobacter jejuni , Enterococcus faecalis , Haemophilus influenzae , Helicobacter pylori , Klebsiella pneumoniae , Legionella pneumophila , Neisseria gonorrhoeae , Neisseria meningitidis , Staphylococcus aureus , Streptococcus pneumoniae and Vibrio cholerae .[ citation needed ]
A human pathogen is a pathogen that causes disease in humans.
Streptococcus is a genus of gram-positive 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, thus when growing they tend to form pairs or chains, which 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.
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.
A biofilm is a syntrophic community of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular polymeric substances (EPSs). The cells within the biofilm produce the EPS components, which are typically a polymeric combination of extracellular polysaccharides, proteins, lipids and DNA. Because they have a three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
Streptococcus pyogenes is a species of Gram-positive, aerotolerant bacteria in the genus Streptococcus. These bacteria are extracellular, and made up of non-motile and non-sporing cocci that tend to link in chains. They are clinically important for humans, as they are an infrequent, but usually pathogenic, part of the skin microbiota that can cause group A streptococcal infection. S. pyogenes is the predominant species harboring the Lancefield group A antigen, and is often called group A Streptococcus (GAS). However, both Streptococcus dysgalactiae and the Streptococcus anginosus group can possess group A antigen as well. Group A streptococci, when grown on blood agar, typically produce small (2–3 mm) zones of beta-hemolysis, a complete destruction of red blood cells. The name group A (beta-hemolytic) Streptococcus is thus also used.
Fusobacterium is a genus of obligate anaerobic, Gram-negative, non-sporeforming bacteria belonging to Gracilicutes. Individual cells are slender, rod-shaped bacilli with pointed ends. Fusobacterium was discovered in 1900 by Courmont and Cade and is common in the flora of humans.
Vibrio is a genus of Gram-negative bacteria, possessing a curved-rod (comma) shape, several species of which can cause foodborne infection or soft-tissue infection called Vibriosis. Infection is commonly associated with eating undercooked seafood. Being highly salt tolerant and unable to survive in freshwater, Vibrio spp. are commonly found in various salt water environments. Vibrio spp. are facultative anaerobes that test positive for oxidase and do not form spores. All members of the genus are motile. They are able to have polar or lateral flagellum with or without sheaths. Vibrio species typically possess two chromosomes, which is unusual for bacteria. Each chromosome has a distinct and independent origin of replication, and are conserved together over time in the genus. Recent phylogenies have been constructed based on a suite of genes.
Bloodstream infections (BSIs) are infections of blood caused by blood-borne pathogens. The detection of microbes in the blood is always abnormal. A bloodstream infection is different from sepsis, which is characterized by severe inflammatory or immune responses of the host organism to pathogens.
Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, spherical bacteria, alpha-hemolytic member of the genus Streptococcus. S. pneumoniae cells 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.
An opportunistic infection is an infection caused by pathogens that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened immune system, an altered microbiome, or breached integumentary barriers. Many of these pathogens do not necessarily cause disease in a healthy host that has a non-compromised immune system, and can, in some cases, act as commensals until the balance of the immune system is disrupted. Opportunistic infections can also be attributed to pathogens which cause mild illness in healthy individuals but lead to more serious illness when given the opportunity to take advantage of an immunocompromised host.
Staphylococcus epidermidis is a Gram-positive bacterium, and one of over 40 species belonging to the genus Staphylococcus. It is part of the normal human microbiota, typically the skin microbiota, and less commonly the mucosal microbiota and also found in marine sponges. It is a facultative anaerobic bacteria. Although S. epidermidis is not usually pathogenic, patients with compromised immune systems are at risk of developing infection. These infections are generally hospital-acquired. S. epidermidis is a particular concern for people with catheters or other surgical implants because it is known to form biofilms that grow on these devices. Being part of the normal skin microbiota, S. epidermidis is a frequent contaminant of specimens sent to the diagnostic laboratory.
Host tropism is the infection specificity of certain pathogens to particular hosts and host tissues. This explains why most pathogens are only capable of infecting a limited range of host organisms.
Medical microbiology, the large subset of microbiology that is applied to medicine, is a branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies various clinical applications of microbes for the improvement of health. There are four kinds of microorganisms that cause infectious disease: bacteria, fungi, parasites and viruses, and one type of infectious protein called prion.
Gerald Domingue is an American medical researcher and academic who served as Professor of Urology, Microbiology and Immunology in the Tulane University School of Medicine and Graduate School for thirty years and also as Director of Research in Urology. He is currently retired and resides in Zürich, Switzerland, where he is engaged in painting and creative writing. At retirement he was honored with the title of Professor Emeritus at Tulane (1967–1997). Prior to Tulane, he was faculty of Saint Louis University School of Medicine); was a lecturer at Washington University School of Dentistry and director of clinical microbiology in St. Louis City Hospital, St. Louis, Missouri.
Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria.
Streptococcus dysgalactiae is a gram positive, beta-haemolytic, coccal bacterium belonging to the family Streptococcaceae. It is capable of infecting both humans and animals, but is most frequently encountered as a commensal of the alimentary tract, genital tract, or less commonly, as a part of the skin flora. The clinical manifestations in human disease range from superficial skin-infections and tonsillitis, to severe necrotising fasciitis and bacteraemia. The incidence of invasive disease has been reported to be rising. Several different animal species are susceptible to infection by S. dysgalactiae, but bovine mastitis and infectious arthritis in lambs have been most frequently reported.
Perianal cellulitis, also known as perianitis or perianal streptococcal dermatitis, is a bacterial infection affecting the lower layers of the skin (cellulitis) around the anus. It presents as bright redness in the skin and can be accompanied by pain, difficulty defecating, itching, and bleeding. This disease is considered a complicated skin and soft tissue infection (cSSTI) because of the involvement of the deeper soft tissues.
In biology, a pathogen, in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.
Staphylococcus pseudintermedius is a gram-positive spherically shaped bacterium of the genus Staphylococcus found worldwide. It is primarily a pathogen for domestic animals, but has been known to affect humans as well. S. pseudintermedius is an opportunistic pathogen that secretes immune-modulating virulence factors, has many adhesion factors, and the potential to create biofilms, all of which help to determine the pathogenicity of the bacterium. Diagnoses of S. pseudintermedius have traditionally been made using cytology, plating, and biochemical tests. More recently, molecular technologies like MALDI-TOF, DNA hybridization and PCR have become preferred over biochemical tests for their more rapid and accurate identifications. This includes the identification and diagnosis of antibiotic resistant strains.
Streptococcosis is an infectious disease caused by bacteria of the genus Steptococcus. This disease is most common among horses, guinea pigs, dogs, cats, and fish with symptoms varying based on the streptococcal species involved. In humans, this disease typically involves a throat infection and is called streptococcal pharyngitis or strep throat.