Here is a list of some bacteria and its etiological agents which causes diseases in man. Also learn about its prevention and control.
The Actinomyces are members of the order Actinomycetales, which have characteristics intermediate between the true bacteria and the molds. They produce a true mycelium. The vegetative mycelium fragments into elements of irregular size and may exhibit angular branching. Conidia are not produced. Not acid-fast. Anaerobic to microaerophilic.
Erect aerial hyphae produced under reduced oxygen tension. Hyphae occasionally septate but no spores formed. Measure 1 μ or more in diameter. Large club-shaped forms greater than 5 g in diameter seen in morbid tissues. Substrate mycelium initially unicellular, and branches may extend into the medium in long filaments or may exhibit fragmentation and characteristic angular branching. Non-motile. Not acid-fast. Gram-positive.
Disease Produced – Organism produces a granulomatous process, generally localized in the jaw, lungs, or abdomen, and, characterized by swellings, at first firm but later breaking down to form multiple draining sinuses. Course of disease long and recovery seldom occurs.
Source of Infection – Oral cavity of man where organism lives around normal carious teeth and in tonsillar crypts without producing an apparent infection.
Mode of Transmission – From the mouth, organism may be swallowed, inhaled, or introduced into jaw tissues by injury. Not known to be transmissible from man to man or from animal to animal.
Incubation Period – Unknown.
Susceptibility and Immunity – Natural susceptibility is low. No immunity following an attack.
Prevalence – Occurs infrequently in man. All races may be affected. More common in males than in females. Disease primarily of domestic animals.
Prevention and Control – Hygiene of oral cavity. Inspection of meat and condemnation of infected carcasses. Destruction of sources of infection.
Disinfection of Discharges from Lesions – Care should be taken to prevent contact with lesions.
Treatment – Prolonged administration of sulfonamide drugs, penicillin, Aureomycin, or chloramphenicol.
The anthrax organism belongs to the genus Bacillus, the members of which are capable of forming heat-resistant spores. Almost all the species are Gram-positive. With the exception of the anthrax bacillus, all members are saprophytic and usually not pathogenic. B. subtilis has been known to become pathogenic at times, but this is the exception rather than the rule. The members are typically aerobic, but some can grow in the almost complete absence of oxygen.
Spores are not produced under anaerobic conditions. On the other hand, the anaerobic spore- producing species do form spores under anaerobic conditions. This fact offers a means for the separation of the aerobic from the anaerobic spore formers. By the application of heat to a mixed culture, the vegetative cells are destroyed and leave only the anaerobic spores, which are capable of germinating into vegetative cells under favourable conditions.
Members of the genus Bacillus are universally distributed in soil and water. Spores and vegetative cells of such species are easily carried into the air by gentle air currents. This explains why viable spores of such organisms are universally present in air and are responsible for many laboratory contaminations of culture media and cultures.
Cells rod-shaped, measuring 1 to 1.3 by 3 to 10 μ, with square or concave ends, and occurring in long chains. Spores ellipsoidal, measuring 0.8 to 1 by 1.3 to 1.5 μ, central or paracentral, often in chains, do not cause a bulging of the cell, and are produced only under aerobic conditions. They are not formed in the animal body. Germination polar. Non-motile, Gram-positive.
Disease Produced – The cause of anthrax, an acute specific disease of cattle, sheep, and swine, sometimes occurring in workers handling wool and hides of animals affected with the disease. Usually occurs as a febrile disease of animals that runs a rapid course and terminates in a septicemia. Mortality rate may run as high as 80 per cent. The infection causes a marked enlargement of the spleen, in which may be found enormous numbers of bacilli.
Two forms occur in man: cutaneous (malignant pustule) and internal anthrax. Cutaneous anthrax is produced by direct inoculation through a cut or abrasion in the skin. This type occurs most frequently in persons working with livestock. It is characterized by the appearance of a small furuncle within 12 to 24 hr. after entrance of the organisms.
The furuncle ulcerates and discharges a seropurulent exudate, which may heal and disappear, or gangrene may set in followed by a septicemia. This usually terminates fatally in about 5 days.
The internal or pulmonary type is contracted by inhalation or by swallowing spores of B. anthracis. The disease is characterized by a pneumonia that generally terminates fatally. Before death, it is possible to isolate the organism from the sputum. The organism may also be recovered from the blood and spinal fluid.
Diagnosis – In the skin type, smears may be prepared from the seropurulent exudate and stained by Gram’s method. The presence of large, Gram-positive, encapsulated organisms without spores is strong evidence for the presence of B. anthracis. The organism may be confirmed by guinea-pig inoculation. The animals usually die in 12 hr. to 3 days with a septicemia.
In the pneumonic type, sputum and blood are examined by the Gram technique. Cultures may be prepared by inoculating blood into broth and examining for characteristic organisms after an incubation period of 24 hr. A confirmation test may be made by guinea-pig inoculation as given above.
Source of Infection – Hair, hides, wool, flesh, and feces of infected animals and their manufactured products.
Mode of Transmission – Inhalation of spores, ingestion of insufficiently cooked food, mechanically by flies, accidental inoculation by wounds or scratch.
Incubation Period – Not over 7 days, usually less than 4. In pulmonary cases may be within 24 hr.
Susceptibility and Immunity – Man is less susceptible to the disease than the herbivora but more so than the carnivora. Immunity may develop after recovery from the disease. Active artificial immunity produced in animals by the use of a vaccine. This is not practiced in human beings.
Prevalence – Rarely in humans, and associated with occurrence of disease in animals or from handling hides, hair, and other products from infected animals. Epizootics occur in cattle and sheep.
Prevention and Control – Destruction of animals known to have the disease. Exposed animals should be immunized with vaccine. Milk from infected animal should not be used. Disinfection of discharges from lesions and of articles soiled by such discharges. All hair, wool, and bristles from sources not known to be free of anthrax should be disinfected.
Human beings handling hides, wool, and hair should report immediately any skin abrasion. Infection has occurred from the use of shaving brushes and tooth brushes made from unsterilized bristles. Spores very resistant, being destroyed in the autoclave at temperatures above 120°C.
Isolation of infected human beings until lesions have healed. Disinfection of discharges from lesions and articles soiled by such discharges.
Treatment – Penicillin, tetracycline antibiotics, sulfadiazine, or anthrax antiserum.
Genus includes three species of very small coccobacilli. Motile and non-motile. On primary isolation, some species dependent upon complex media; all are hemolytic. Carbohydrates not fermented. A dermonecrotic toxin is produced. All are parasitic.
Minute coccobacilli, measuring 0.2 to 0.3 by 1 μ, occurring singly, in pairs, and occasionally in short chains, Capsules may be demonstrated. Show tendency to bipolar staining. Non-motile. Gram-negative.
Blood medium excellent for isolation and maintenance. Charcoal may be used instead of blood in certain agar media.
Various forms of the organism have been isolated, including smooth, rough, and intermediate types. The smooth forms are pathogenic, whereas the rough and intermediate forms are not. The organisms may exist in four phases on the basis of serological reactions.
Freshly isolated or phase I strains are encapsulated, virulent for laboratory animals, hemolytic, and require the presence of the X and V factors. The phase I properties are lost on artificial cultivation, the organisms changing to phases II, III, or IV. Only virulent organisms in phase I are suitable for the production of vaccines.
Disease Produced – Believed to be the cause of whooping cough. The organism is sometimes referred to as the Bordet-Gengou bacillus after the names of its discoverers. Whooping cough is an acute, specific, infectious disease of the trachea and bronchi. It is characterized by a cough typical of the disease and lasts 1 to 2 months.
The disease starts as a catarrhal condition followed by an irritating cough. The cough becomes paroxysmal after a period of 1 to 2 weeks. The paroxysms consist of a repeated series of violent coughs often followed by a characteristic long-drawn whoop during inhalation. Paroxysms are sometimes followed by vomiting. The period of communicability probably does not last longer than 3 weeks after the cough appears.
Whooping cough shows its greatest incidence in children under five years of age, and the death rate is highest in those under one year of age. Children suffering from the disease show a predisposition to infections by micrococci, streptococci, pneumococci, and tubercle bacilli.
Diagnosis – The organism may be recovered by the cough-plate method. This consists of exposing a Petri dish, containing an appropriate medium, before a patient’s mouth during a cough in the early paroxysmal stage of the infection. The plate is then incubated, and characteristic colonies are isolated.
Source of Infection – Discharges from mucous membranes of larynx and bronchi of infected persons.
Mode of Transmission – Direct contact with an infected person or with the discharges from an infected person. Disease easily spread among children by personal contact. There is no evidence of a carrier state.
Incubation Period – Usually 7 days, almost always within 10 days, and not exceeding 21 days.
Susceptibility and Immunity – Susceptibility to disease general; no natural immunity. Children under seven most susceptible to infection. Children under two most susceptible to fatal attack. One attack confers a definite immunity but not for life; second attacks are known to occur. Passive immunity may be conferred by the use of immune or convalescent serum.
Prevalence – Common among children everywhere regardless of race or climate. About 15 per cent of cases occur in children under two years of age.
Prevention and Control – Vaccination of all children under five years of age. Especially advisable in infants two months old.
Isolation of infected individuals, especially from children. Disinfection of discharges from nose and throat of patient and articles soiled with such discharges. Brief passive immunity may be conveyed to young children by injection of appropriate amounts of hyper-immune or convalescent serum. The tetracycline antibiotics and chloramphenicol tend to abort the infection, but not the symptoms, although minor improvement may follow.
Members of this genus are classified under the order Spirochaetales, which have characteristics intermediate between the true bacteria and the protozoa. Cells measure 8 to 16 μ in length, with coarse, shallow, irregular spirals, a few of which may be obtuse-angled. Generally taper terminally into fine filaments.
Parasitic upon many forms of animal life. Some are pathogenic for man, other mammals, or birds. Generally hematophytic or are found on mucous membranes. Some are transmitted by the bites of arthropods.
Cells spiral-shaped, measuring 0.35 to 0.5 by 8 to 16 μ, with pointed ends. Spiral amplitude 1.5 μ. Spirals large, wavy, inconstant, about five in number. Terminal finely spiral filaments present. Motility by active corkscrew motion without polarity. Gram-negative.
Disease Produced – The cause of Central and South African relapsing fever. Pathogenic for mice and rats. Disease characterized by short febrile paroxysms lasting 2 or 3 days, alternating with afebrile periods of 3 or 4 days. General eruption on the body. Relapses average 6 or 7.
Diagnosis – Diagnosis made by demonstrating the organisms in blood smears at time of second febrile attack, or from blood of mice or rats previously inoculated with the patient’s blood.
Source of Infection – An infection of wild rodents transmitted by ticks of the genus.
Ornithodorus – In Texas and Kansas vector is O. turicata; in California, Colorado, and Idaho vector is O. hermsi; in Montana it is O. parkeri; in Panama and Central and South America it is O. talaje; and in tropical Africa it is O. moubata.
Mode of Transmission – Disease transmitted by bite of a tick.
Incubation Period – From 3 to 6 days, sometimes as short as 2 or as long as 12 days.
Susceptibility and Immunity – Susceptibility is general. Active immunity produced during course of disease which overcomes the blood infection, resulting in disappearance of spirochetes from the circulation. Duration of immunity after recovery probably not more than 2 years.
Prevalence – Widespread throughout tropical Africa. Also observed in Spain, North Africa, Arabia, Iran, India, and other parts of central Asia, North and South America. In the United States cases have been reported from 13 widely distributed states.
Prevention and Control – Avoidance of tick-infested areas. Ticks are able to live and remain infective for years without feeding. Use of a tick repellent on trousers and hose.
Treatment – Penicillin, the tetracyclines, and chloramphenicol are effective.
Organisms cylindrical or slightly flattened, measuring 0.35 to 0.5 by 8 to 16 n with pointed ends. Spiral amplitude 1.5 μ. Spirals large, wavy, inconstant, about five in number. Terminal finely spiral filaments present. Motility by active corkscrew motion without polarity. Gram-negative.
Disease Produced – The cause of European relapsing fever. Transmissible to monkeys, mice, and rats.
Disease characterized by short febrile paroxysms lasting 2 or 3 days, alternating with afebrile periods of 3 or 4 days. General eruption on the body. Relapses vary from 1 to 10, usually not more than 2. Duration of disease 13 to 16 days.
Diagnosis – Diagnosis made by demonstrating the organisms in dark- field preparations of fresh blood or by inoculating rats with 15 to 25 ml. of patient’s blood.
Source of Infection – Natural reservoir of infection not known. Lice become infective in about 16 days after biting an infected person and remain so for life.
Mode of Transmission – Probably by the bite of a louse and the rubbing of its feces into the abrasion in the skin.
Incubation Period – Usually 7 and as long as 12 days.
Susceptibility and Immunity – Susceptibility is general. Active immunity produced during course of disease. Duration of immunity after recovery probably not more than 2 years.
Prevalence – Disease prevalent among louse-infested primitive people. Found in parts of Europe, Asia, North and South Africa, and Central America. Has not been observed in the United States.
Prevention and Control – Application of insecticide at appropriate intervals to people living under poor, unhygienic conditions. Improvement of living conditions, including frequent bathing and washing of clothing.
Debusing of patient’s clothing and bedroom. Application of insecticide to patient’s clothing and body. Application of insecticide to all persons in contact with infected individuals.
Organisms measure 0.3 by 8 to 12 μ, with 3 to 8 irregular shallow spirals. Motile with a rapid, progressive, vibratory motion. Gram-negative.
Cells Cultivated under Anaerobic Conditions – Cultures may show long forms with only a writhing motion.
Disease Produced – B. vincentii occurs in association with Fusobacterium fusiforme in Vincent’s angina, and in acute infection of the tonsils or neighbouring parts, and is characterized by the appearance of a pseudomembranous inflamation followed by ulceration.
Disease sometimes called trench mouth. The lungs may also become involved. When this occurs, the patient may present the clinical and anatomical picture of pulmonary gangrene, pulmonary abscess, or bronchiectasis.
Cells of F. fusiforme are straight or slightly curved rods, 0.5 to 1 by 8 to 16 μ, occurring in pairs with blunt ends together and outer ends pointed, sometimes in short, curved chains or long spirillum-like threads. Granules present. Non-motile. Anaerobic. Gram-negative.
Diagnosis – Disease diagnosed by preparing smears direct from the deeper ulcerated areas, staining by Gram technique, and examining under oil-immersion objective. Characteristic smear shows presence of spirochetes and bacilli in large numbers.
Source of Infection – From deposit on teeth; the oral cavity.
Mode of Transmission – Disease not ordinarily communicable. Under unusual conditions of crowding, such as may prevail among soldiers, the infection may become transmissible. Disease appears to be associated with a state of lowered resistance. The tonsillar ulceration occurs often in individuals whose resistance has been lowered by such diseases as measles, tuberculosis, diabetes, and scarlet fever.
Susceptibility and Immunity – Susceptibility to infection general. Acquired immunity does not follow recovery from the disease.
Prevention and Control – Local lesions usually controlled by treatment with arsenicals or penicillin. Neoarsphenamine, sulfarsphenamine, or bismarsen is effective in curing the pulmonary infection if administered during the first few days of the disease before the beginning of necrosis. Primary tropical ulcers which are caused by these symbiotic organisms also respond to treatment with penicillin.
Klebsiella pneumoniae was first isolated by Friedlander and is usually referred to as Friedlander’s bacillus. It is not infrequently found associated with upper respiratory infections in man. In most instances the organism appears to be present as a secondary invader. Less than 1 per cent of pneumonias are caused by this organism.
Rods’ measuring 0.3 to 0.5 by 5 μ, with rounded ends, occurring singly and in pairs. Encapsulated. Non-motile. Gram-negative.
Disease Produced – Associated with infections of the respiratory, intestinal, and genitourinary tracts of man. Isolated from the lungs in lobar pneumonia. Associated with pneumonia and other inflammations of the respiratory tract. May also produce otitis media, empyema, pericarditis, meningitis, and septicemia.
Source of Infection – Buccal and nasal discharges of infected persons or carriers: articles contaminated with such discharges.
Mode of Transmission – By droplet spread; direct contact with infected person or carrier articles soiled with discharges from nose and throat of such person.
Susceptibility and Immunity – Organism carried in nasopharynx of 1 per cent of normal individuals. Susceptibility of low grade, highest in infants and young children and in the aged. Immunity relatively slight and of short duration.
Prevention and Control – Isolation of infected persons; concurrent disinfection of discharges from mouth, nose, and contaminated articles. Treatment consists in the use of streptomycin during the acute phase, then of tetracyclines and chloramphenicol.