|Clostridium tetani is a pathogenic bacterium that causes tetanus|
Pathogenic bacteria are bacteria that can cause disease.This article deals with human pathogenic bacteria. Although most bacteria are harmless or often beneficial, some are pathogenic, with the number of species estimated as fewer than a hundred that are seen to cause infectious diseases in humans. By contrast, several thousand species exist in the human digestive system.
Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.
A disease is a particular abnormal condition that negatively affects the structure or function of part or all of an organism, and that is not due to any external injury. Diseases are often construed as medical conditions that are associated with specific symptoms and signs. A disease may be caused by external factors such as pathogens or by internal dysfunctions. For example, internal dysfunctions of the immune system can produce a variety of different diseases, including various forms of immunodeficiency, hypersensitivity, allergies and autoimmune disorders.
In biology, a pathogen is also known as an infectious agent, or a germ. In the oldest and broadest sense, a pathogen is anything that can produce disease; the term came into use in the 1880s. Typically the term pathogen is used to describe an infectious microorganism or agent, such as a virus, bacterium, protozoan, prion, viroid, or fungus. Small animals, such as certain kinds of worms and insect larvae, can also produce disease but such animals are usually, in common parlance, referred to as parasites rather than pathogens. The scientific study of microscopic, pathogenic organisms is called microbiology, while the study of disease that may include these pathogens is called pathology. Parasitology, meanwhile, is the scientific study of parasites and the organisms that host them.
One of the bacterial diseases with the highest disease burden is tuberculosis, caused by Mycobacterium tuberculosis bacteria, which kills about 2 million people a year, mostly in sub-Saharan Africa. Pathogenic bacteria contribute to other globally important diseases, such as pneumonia, which can be caused by bacteria such as 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.
Disease burden is the impact of a health problem as measured by financial cost, mortality, morbidity, or other indicators. It is often quantified in terms of quality-adjusted life years (QALYs) or disability-adjusted life years (DALYs), both of which quantify the number of years lost due to disease (YLDs). One DALY can be thought of as one year of healthy life lost, and the overall disease burden can be thought of as a measure of the gap between current health status and the ideal health status. According to an article published in The Lancet in June 2015, low back pain and major depressive disorder were among the top ten causes of YLDs and were the cause of more health loss than diabetes, chronic obstructive pulmonary disease, and asthma combined. The study based on data from 188 countries, considered to be the largest and most detailed analysis to quantify levels, patterns, and trends in ill health and disability, concluded that "the proportion of disability-adjusted life years due to YLDs increased globally from 21.1% in 1990 to 31.2% in 2013." The environmental burden of disease is defined as the number of DALYs that can be attributed to environmental factors. These measures allow for comparison of disease burdens, and have also been used to forecast the possible impacts of health interventions. By 2014 DALYs per head were "40% higher in low-income and middle-income regions."
Tuberculosis (TB) is an infectious disease usually caused by Mycobacterium tuberculosis (MTB) bacteria. Tuberculosis generally affects the lungs, but can also affect other parts of the body. Most infections do not have symptoms, in which case it is known as latent tuberculosis. About 10% of latent infections progress to active disease which, if left untreated, kills about half of those affected. The classic symptoms of active TB are a chronic cough with blood-containing sputum, fever, night sweats, and weight loss. It was historically called "consumption" due to the weight loss. Infection of other organs can cause a wide range of symptoms.
Mycobacterium tuberculosis is a species of pathogenic bacteria in the family Mycobacteriaceae and the causative agent of tuberculosis. First discovered in 1882 by Robert Koch, M. tuberculosis has an unusual, waxy coating on its cell surface primarily due to the presence of mycolic acid. This coating makes the cells impervious to Gram staining, and as a result, M. tuberculosis can appear either Gram-negative or Gram-positive. Acid-fast stains such as Ziehl-Neelsen, or fluorescent stains such as auramine are used instead to identify M. tuberculosis with a microscope. The physiology of M. tuberculosis is highly aerobic and requires high levels of oxygen. Primarily a pathogen of the mammalian respiratory system, it infects the lungs. The most frequently used diagnostic methods for tuberculosis are the tuberculin skin test, acid-fast stain, culture, and polymerase chain reaction.
Koch's postulates are the standard to establish a causative relationship between a microbe and a disease.
Koch's postulates are four criteria designed to establish a causative relationship between a microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884, based on earlier concepts described by Jakob Henle, and refined and published by Koch in 1890. Koch applied the postulates to describe the etiology of cholera and tuberculosis, but they have been controversially generalized to other diseases. These postulates were generated prior to understanding of modern concepts in microbial pathogenesis that cannot be examined using Koch's postulates, including viruses or asymptomatic carriers. They have largely been supplanted by other criteria such as the Bradford Hill criteria for infectious disease causality in modern public health.
Causality is what connects one process with another process or state, where the first is partly responsible for the second, and the second is partly dependent on the first. In general, a process has many causes, which are said to be causal factors for it, and all lie in its past. An effect can in turn be a cause of, or causal factor for, many other effects, which all lie in its future. Multiple philosophers have believed that causality is metaphysically prior to notions of time and space.
Each species has specific effect and causes symptoms in people who are infected. Some, if not most people who are infected with a pathogenic bacteria do not have symptoms. Immuno-compromised individuals are more susceptible to pathogenic bacteria.
Some pathogenic bacteria cause disease under certain conditions, such as entry through the skin via a cut, through sexual activity or through a compromised immune function.
Streptococcus and Staphylococcus are part of the normal skin microbiota and typically reside on healthy skin or in the nasopharangeal region. Yet these species can potentially initiate skin infections. They are also able to cause sepsis, pneumonia or meningitis. These infections can become quite serious creating a systemic inflammatory response resulting in massive vasodilation, shock, and death.
Streptococcus is a genus of gram-positive coccus or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Firmicutes. 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.
Staphylococcus is a genus of Gram-positive bacteria in the family Staphylococcaceae in the order Bacillales. Under the microscope, they appear spherical (cocci), and form in grape-like clusters. Staphylococcus species are facultative anaerobic organisms.
Sepsis is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. Common signs and symptoms include fever, increased heart rate, increased breathing rate, and confusion. There may also be symptoms related to a specific infection, such as a cough with pneumonia, or painful urination with a kidney infection. In the very young, old, and people with a weakened immune system, there may be no symptoms of a specific infection and the body temperature may be low or normal, rather than high. Severe sepsis is sepsis causing poor organ function or insufficient blood flow. Insufficient blood flow may be evident by low blood pressure, high blood lactate, or low urine output. Septic shock is low blood pressure due to sepsis that does not improve after fluid replacement.
Other bacteria are opportunistic pathogens and cause disease mainly in people suffering from immunosuppression or cystic fibrosis. Examples of these opportunistic pathogens include Pseudomonas aeruginosa , Burkholderia cenocepacia , and Mycobacterium avium .
An opportunistic infection is an infection caused by pathogens that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota, or breached integumentary barriers. Many of these pathogens do not cause disease in a healthy host that has a normal immune system. However, a compromised immune system, which is seriously debilitated and has lowered resistance to infection, a penetrating injury, or a lack of competition from normal commensals presents an opportunity for the pathogen to infect.
Immunosuppression is a reduction of the activation or efficacy of the immune system. Some portions of the immune system itself have immunosuppressive effects on other parts of the immune system, and immunosuppression may occur as an adverse reaction to treatment of other conditions.
Cystic fibrosis (CF) is a genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. Other signs and symptoms may include sinus infections, poor growth, fatty stool, clubbing of the fingers and toes, and infertility in most males. Different people may have different degrees of symptoms.
Obligate intracellular parasites (e.g. Chlamydophila, Ehrlichia, Rickettsia) have the ability to only grow and replicate inside other cells. Even these intracellular infections may be asymptomatic, requiring an incubation period. An example of this is Rickettsia which causes typhus. Another causes Rocky Mountain spotted fever.
Chlamydophila is a controversial bacterial genus belonging to the family Chlamydiaceae, order Chlamydiales, class/phylum Chlamydiae.
Ehrlichia is a genus of rickettsiales bacteria that is transmitted to vertebrates by ticks. These bacteria cause the Ehrlichiosis infection, which is considered zoonotic, because the main reservoirs for the disease are animals.
Rickettsia is a genus of nonmotile, Gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci 0.1 μm in diameter, rods 1–4 μm long, or threads of up to about 10 μm long. The term "rickettsia" has nothing to do with rickets, which is a deficiency disease resulting from lack of vitamin D; the bacterial genus Rickettsia was named after Howard Taylor Ricketts, in honour of his pioneering work on tick-borne spotted fever.
Chlamydia is a phylum of intracellular parasites. These pathogens can cause pneumonia or urinary tract infection and may be involved in coronary heart disease.
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 of host cells.
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. They can also cause damage indirectly by provoking an immune response that inadvertently damages host cells.
Once pathogens attach to host cells, they can cause direct damage as the pathogens use the host cell for nutrients and produce waste products.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. However, toxins produced by bacteria cause most of the direct damage to host cells.
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.
An excessive or inappropriate immune response triggered by an infection may damage host cells.
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.
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.
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.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. Phage therapy can also be used to treat certain bacterial infections.
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).
Many genera contain pathogenic bacteria 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|
|Borrelia||Negative, stains poorly||spirochete||Anaerobic||Extracellular|
|Campylobacter||Negative||spiral rods |
coccoid in older cultures
|Chlamydia and Chlamydophila||(not Gram-stained)||Small, round, ovoid||Facultative or strictly aerobic||Obligate intracellular|
|Clostridium||Positive||Large, blunt-ended rods||Obligate anaerobic||extracellular|
|Corynebacterium||Positive (unevenly)||bacilli||Mostly facultative anaerobic||extracellular|
|Escherichia||Negative||Bacillus||Facultative anaerobic||extracellular or intracellular|
|Francisella||Negative||coccobacillus||strictly aerobic||Facultative intracellular|
|Haemophilus||Negative||coccobacilli to long and slender filaments||extracellular|
|Legionella||Negative, stains poorly||cocobacilli||aerobic||facultative intracellular|
|Leptospira||Negative, stains poorly||Spirochete||Strictly aerobic||extracellular|
|Listeria||Positive, darkly||Slender, short rods||Facultative Anaerobic||facultative intracellular|
|Mycobacterium||(none)||Long, slender rods||aerobic||intracellular|
|Mycoplasma||(none)||'fried egg' appearance, no cell wall||Mostly facultative anaerobic; M. pneumoniae strictly aerobic||extracellular|
|Neisseria||Negative||Kidney bean-shaped||aerobic||Gonococcus: facultative intracellular|
N. meningitidis: extracellular
|Rickettsia||Negative, stains poorly||Small, rod-like coccobacillary||Aerobic||Obligate intracellular|
|Salmonella||Negative||Bacillus shape||Facultative anaerobica||Facultative intracellular|
|Staphylococcus||Positive, darkly||Round cocci||Facultative anaerobic||extracellular, facultative intracellular|
|Streptococcus||Positive||ovoid to spherical||Facultative anaerobic||extracellular|
|Treponema||Negative, stains poorly||Spirochete||Aerobic||extracellular|
|Ureaplasma||Stains poorly||indistinct, 'fried egg' appearance, no cell wall||anaerobic||extracellular|
|Vibrio||Negative||Spiral with single polar flagellum||Facultative anaerobic||extracellular|
|Yersinia||Negative, bipolarly||Small rods||Facultative Anaerobe||Intracellular|
This is description of the more common genera and species presented with their clinical characteristics and treatments.
|Actinomyces israelii||Oral flora||Actinomycosis: painful abscesses in the mouth, lungs, or gastrointestinal tract.||Prolonged penicillin G and drainage|
|Bacillus anthracis||In early infection: |
|Bacteroides fragilis||Gut flora||Abscesses in gastrointestinal tract, pelvic cavity and lungs||metronidazole|| Wound care |
|Bordetella pertussis||Macrolides such as erythromycin, before paroxysmal stage|
|Borrelia|| B. burgdorferi |
Ixodes hard ticks
Wearing clothing that limits skin exposure to ticks.
| B. recurrentis ||Pediculus humanus corporis body louse (B. recurrentis only) and Ornithodoros soft ticks||Relapsing fever||Penicillin, tetracycline, doxycycline||Avoid areas where ticks are found |
|Brucella|| B. abortus |
|Chlamydia||C. pneumoniae||Atypical pneumonia||None|
|Chlamydophila psittaci||Inhalation of dust with secretions or feces from birds (e.g. parrots)||Psittacosis, mainly atypical pneumonia||-|
|Clostridium||C. botulinum||Spores from soil, persevere in canned food, smoked fish and honey|
Proper food preservation techniques
Gut flora, overgrowing when other flora is depleted
| Fecal bacteriotherapy |
|C. perfringens||Gas gangrene:||Appropriate food handling|
|Ehrlichia|| E. canis ||Dog tick||Ehrlichiosis: headache, muscle aches, and fatigue|
|Enterococcus|| E. faecalis |
No vaccine Hand washing and other nosocomial prevention
|Escherichia||E. coli (generally)||UTI: |
(resistance-tests are required first)
|(no vaccine or preventive drug) |
|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. Can cause severe pneumonia.|
|Haemophilus influenzae||Meningitis: |
(resistance-tests are required first)
|Helicobacter pylori||(No vaccine or preventive drug)|
|Legionella pneumophila||(no vaccine or preventive drug)|
|Leptospira species||Vaccine not widely used|
|Listeria monocytogenes||(no vaccine)|
|Mycobacterium||M. leprae||Tuberculoid form: |
(difficult, see Tuberculosis treatment for more details)
|Neisseria||N. gonorrhoeae||Uncomplicated gonorrhea: |
|Pseudomonas aeruginosa||Opportunistic; Infects damaged tissues or people with immunodeficiency.||Pseudomonas infection:||(no vaccine) |
|Nocardia asteroides||In soil||Nocardiosis: Pneumonia, endocarditis, keratitis, neurological or lymphocutaneous infection||TMP/SMX|
|Rickettsia rickettsii||(no preventive drug or approved vaccine) |
|Other Salmonella species ||(No vaccine or preventive drug)|
|Staphylococcus||aureus||Coagulase-positive staphylococcal infections:||(no vaccine or preventive drug) |
|epidermidis||Human flora in skin, anterior nares and mucous membranes||None|
|saprophyticus||Part of normal vaginal flora||None|
|Streptococcus||agalactiae||Human flora in vagina, urethral mucous membranes, rectum||None|
|viridans||Oral flora, penetration through abrasions||Penicillin G|
|Treponema pallidum subspecies pallidum|
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.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. 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 meningitides , Staphylococcus aureus , Streptococcus pneumoniae and Vibrio cholerae .
An antibiotic is a type of antimicrobial substance active against bacteria and is the most important type of antibacterial agent for fighting bacterial infections. Antibiotic medications are widely used in the treatment and prevention of such infections. They may either kill or inhibit the growth of bacteria. A limited number of antibiotics also possess antiprotozoal activity. Antibiotics are not effective against viruses such as the common cold or influenza; drugs which inhibit viruses are termed antiviral drugs or antivirals rather than antibiotics.
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 cell wall.
A biofilm comprises any syntrophic consortium 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 (EPS). The cells within the biofilm produce the EPS components, which are typically a polymeric conglomeration of extracellular polysaccharides, proteins, lipids and DNA. Because they have three-dimensional structure and represent a community lifestyle for microorganisms, they have been metaphorically described as "cities for microbes".
Conjunctivitis, also known as pink eye, is inflammation of the outermost layer of the white part of the eye and the inner surface of the eyelid. It makes the eye appear pink or reddish. Pain, burning, scratchiness, or itchiness may occur. The affected eye may have increased tears or be "stuck shut" in the morning. Swelling of the white part of the eye may also occur. Itching is more common in cases due to allergies. Conjunctivitis can affect one or both eyes.
Neisseria gonorrhoeae, also known as gonococcus (singular), or gonococci (plural) is a species of Gram-negative diplococci bacteria isolated by Albert Neisser in 1879. It causes the sexually transmitted genitourinary infection gonorrhea as well as other forms of gonococcal disease including disseminated gonococcemia, septic arthritis, and gonococcal ophthalmia neonatorum.
Streptococcus pyogenes is a species of Gram-positive bacterium in the genus Streptococcus. These bacteria are aerotolerant and an extracellular bacterium, made up of non-motile and non-sporing cocci. It is clinically important for humans. It is an infrequent, but usually pathogenic, part of the skin microbiota. It 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. Group A streptococci when grown on blood agar typically produces small zones of beta-hemolysis, a complete destruction of red blood cells. It is thus also called group A (beta-hemolytic) streptococcus (GABHS), and can make colonies greater than 5 mm in size.
The human microbiota is the aggregate of microorganisms that resides on or within any of a number of human tissues and biofluids, including the skin, mammary glands, placenta, seminal fluid, uterus, ovarian follicles, lung, saliva, oral mucosa, conjunctiva, biliary and gastrointestinal tracts. They include bacteria, archaea, fungi, protists and viruses. Though micro-animals can also live on the human body, they are typically excluded from this definition. The human microbiome refers specifically to the collective genomes of resident microorganisms.
Vibrio is a genus of Gram-negative bacteria, possessing a curved-rod shape, several species of which can cause foodborne infection, usually associated with eating undercooked seafood. Typically found in salt water, Vibrio species are facultative anaerobes that test positive for oxidase and do not form spores. All members of the genus are motile and have polar flagella with 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.
Bacillary dysentery is a type of dysentery, and is a severe form of shigellosis.
Pseudomonas aeruginosa is a common Gram-negative, rod-shaped bacterium that can cause disease in plants and animals, including humans. A species of considerable medical importance, P. aeruginosa is a multidrug resistant pathogen recognized for its ubiquity, its intrinsically advanced antibiotic resistance mechanisms, and its association with serious illnesses – hospital-acquired infections such as ventilator-associated pneumonia and various sepsis syndromes.
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 flora, typically the skin flora, and less commonly the mucosal flora. 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 flora, S. epidermidis is a frequent contaminant of specimens sent to the diagnostic laboratory.
Virulence factors are molecules produced by bacteria, viruses, fungi, and protozoa that add to their effectiveness and enable them to achieve the following:
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 Zurich, 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 served on the faculty of St. Louis University ; was a lecturer at Washington University and director of clinical microbiology in St. Louis City Hospital, St. Louis, Missouri.
Meningitis is an acute inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or altered consciousness, vomiting, and an inability to tolerate light or loud noises. Young children often exhibit only nonspecific symptoms, such as irritability, drowsiness, or poor feeding. If a rash is present, it may indicate a particular cause of meningitis; for instance, meningitis caused by meningococcal bacteria may be accompanied by a characteristic rash.
Streptococcus canis is a group G beta-hemolytic species of Streptococcus. It was first isolated in dogs, giving the bacterium its name. These bacteria are characteristically different from Streptococcus dysgalactiae, which is a human-specific group G species that has a different phenotypic chemical composition. S. canis is important to the skin and mucosal health of cats and dogs, but under certain circumstances, these bacteria can cause opportunistic infections. These infections were known to afflict dogs and cats prior to the formal description of the species in Devriese et al., 1986. However, additional studies revealed cases of infection in other mammal species, including cattle and even humans. Instances of mortality from S. canis in humans are very low with only a few reported cases, while actual instances of infection may be underreported due to mischaracterizations of the bacteria as S. dysgalactiae. This species, in general, is highly susceptible to antibiotics, and plans to develop a vaccine to prevent human infections are currently being considered.
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.
Mycoplasma salivarium is a species of bacteria in the genus Mycoplasma. This genus of bacteria lacks a cell wall around their cell membrane. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis. Mycoplasma are the smallest bacterial cells yet discovered, can survive without oxygen and are typically about 0. 1 µm in diameter. Mycoplasma salivarium is found in the mouths of 97% of the healthy population, and is generally considered to be a commensal organism and part of the normal oral flora.