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Here is an essay on ‘Bacteria and Human Disease’ for class 11 and 12. Find paragraphs, long and short essays on ‘Bacteria and Human Disease’ especially written for school and college students.
Essay on Bacteria and Human Disease
Essay # 1. Brucella Abortus:
Cells short ellipsoidal rods, occurring singly, in pairs, and occasionally in chains, measuring 0.3 to 0.4 μ in length. Organism requires 10 per cent carbon dioxide for isolation; becomes aerobic after several transfers. Non-motile. Gram-negative.
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Disease Produced – The cause of contagious abortion in cattle. The same effects are produced in mares, sheep, rabbits, and guinea pigs. Causes undulant fever or brucellosis in man.
Brucellosis is a general infection with gradual or insidious onset and is characterized by irregular fever usually of prolonged duration, headache, sweating, chills, pain in the joints and muscles. The usual case follows a long febrile period, returning to normal by lysis. In this country febrile lapses are not common. Recovery is usual but disability may be pronounced.
Diagnosis – Since brucellosis is generally accompanied by a septicemia, a diagnosis can usually be made on the basis of a blood culture.
Agglutinins and complement-fixing antibodies are present in the serum of patients suffering from the disease. In the event the blood culture is negative, it is generally desirable to test the patient’s serum for the presence of agglutinins. An agglutination titer of 1:100 or above is positive evidence of undulant fever.
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Source of Infection – Tissues, blood, milk, and urine of infected animals, especially goats, swine, and cattle. Laboratory infections are quite common.
Mode of Transmission – Drinking milk from infected animals and by direct contact with infected animals or animal products.
Incubation Period – From 6 to 30 days or more, usually 14 days.
Susceptibility and Immunity – Most persons have some natural immunity or have acquired partial immunity by ingestion of small doses of the organism. Duration of immunity not known. One attack of undulant fever usually protects against a second attack.
Prevalence – More prevalent in males than in females, particularly in persons handling milk, cows, hogs, goats, and in those consuming raw milk of cows or goats. Occurs throughout the United States and Canada, affecting persons of all races. Brucella suis infections of greater occurrence in Middle West. Disease more prevalent from May to October.
Prevention and Control – Source of infection should be ascertained. Pasteurization of all milk supplies from cows and goats. Boiling of milk may be more practicable. Animals should be tested by agglutination technique and positive reactors segregated or slaughtered.
Education of public and meat handlers on nature of disease and mode of transmission. Vaccination of calves. Care in handling and disposal of discharges and fetus from an aborting animal. Inspection of all meats, especially pork and pork products.
Early recognition of disease. Disinfection of body discharges. The tetracycline antibiotics generally produce rapid subsidence of fever and symptoms within several days. Relapse may occur. More satisfactory results obtained from a combination of Aureomycin and dihydrostre-ptomycin over a period of at least 3 weeks. Blood transfusion may be necessary where acute anemia exists. Disease seldom fatal.
Essay # 2. Brucella Melitensis:
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Rods ellipsoidal, measuring 0.3 to 0.4 μ in length, occurring singly and in pairs, rarely in short chains. Non-motile. Gram-negative. Non-acid-fast.
Disease Produced – The cause of undulant fever (brucellosis) in man and abortion in goats. May infect cows and hogs and be excreted in their milk. Infectious for all domestic animals. Undulant fever is a general infection with gradual or insidious onset and characterized by irregular fever usually of prolonged duration, sweating, chills, pain in the joints and muscles.
Diagnosis – Since brucellosis is generally accompanied by a septicemia, a diagnosis can usually be made on the basis of a blood culture. Blood cultures are positive in about 80 per cent of the cases after the second day and the infection may continue in the septicemic form for a number of months.
Agglutinins and complement-fixing antibodies are present in the serum of patients suffering from the disease. In the event the blood culture is negative, it is generally desirable to test the patient’s serum for the presence of agglutinins. Agglutinins generally occur in the serum about the tenth day of the fever.
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An agglutination titer of 1:100, or above, is positive evidence of undulant fever. Since antiserum for B. melitensis will cross-agglutinate with B. abortus and B. suis, agglutinin-absorption tests are necessary for diagnosis.
Source of Infection – Tissues, blood, milk, and urine of infected goats. Disease spread to man through the milk of such animals. The disease in both goats and man is a septicemia. Laboratory infections are quite common.
Mode of Transmission – Drinking milk from infected animals and by direct contact with infected animals or animal products.
Incubation Period – From 6 to 30 days or more, usually 14 days.
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Susceptibility and Immunity – Most persons have some natural immunity or have acquire partial immunity by ingestion of small doses of the organism. Duration of immunity not known. One attack of undulant fever protects against a second attack.
Prevalence – More prevalent in males than in females, particularly in persons handling milk, cows, hogs, goats, and in those consuming raw milk of cows or goats. Occurs throughout the United States and Canada, affecting persons of all races. Disease more prevalent from May to October.
Prevention and Control – Source of infection should be ascertained. Pasteurization of all milk supplies from cows and goats. Boiling of milk may be more practicable. Animals should be tested by agglutination technique and positive reactors segregated or slaughtered. Education of public and meat handlers on nature of disease and mode of transmission. Vaccination of animals. Care in handling and disposal of discharges and fetus from an aborting animal. Inspection of all meats, especially pork and pork products.
Early Recognition of Disease – Disinfection of body discharges. The tetracycline antibiotics generally produce rapid subsidence of fever and symptoms within several days. Relapse may occur. More satisfactory results obtained from a combination of Aureomycin and dihydrostrep-tomycin over a period of at least 3 weeks. Blood transfusion may be necessary where acute anemia exists. Disease seldom fatal.
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Essay # 3. Brucella Suis:
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Rods ellipsoidal, measuring 0.3 to 0.4 n in length, occurring singly and in pairs, rarely in short chains. Non-motile, non-acid-fast. Gram-negative.
Disease Produced – The cause of undulant fever (brucellosis) in man and abortion in hogs. May infect cows and goats and be excreted in their milk. Infectious for all domestic animals. Undulant fever is a general infection with gradual or insidious onset and characterized by irregular fever usually of prolonged duration, sweating, chills, pain in the joints and muscles.
Diagnosis – Since brucellosis is generally accompanied by a septicemia, a diagnosis can usually be made on the basis of a blood culture. Blood cultures are positive in about 80 per cent of the cases after the second day and the infection may continue in the septicemic form for a number of months.
Agglutinins and complement-fixing antibodies are present in the serum of patients suffering from the disease. In the event the blood culture is negative, it is generally desirable to test the patient’s serum for the presence of agglutinins. Agglutinins generally occur in the serum about the tenth day of the fever.
An agglutination titer of 1:100, or above, is positive evidence of undulant fever. Since antiserum for B. suis will cross-agglutinate with B. melitensis and B. abortus, agglutinin-absorption tests are necessary for diagnosis.
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Source of Infection – Tissues, blood, milk, and urine of infected animals. Disease spread to man through the milk of such animals. The disease in both hogs and man is a septicemia. Laboratory infections are quite common.
Mode of Transmission – Drinking milk from infected animals and by direct contact with infected animals or animal products.
Incubation Period – From 6 to 30 days or more, usually 14 days.
Susceptibility and Immunity – Most persons have some natural immunity or have acquired partial immunity by ingestion of small doses of the organism. Duration of immunity not known. One attack of undulant fever usually protects against a second attack.
Prevalence – More prevalent in males than in females, particularly in persons handling milk, cows, hogs, goats, and in those consuming raw milk of cows or goats. Occurs throughout the United States and Canada, affecting persons of all races. Disease more prevalent from May to October.
Prevention and Control – Source of infection should be ascertained. Pasteurization of all milk supplies. Boiling of milk may be more practicable. Animals should be tested by agglutination technique and positive reactors segregated or slaughtered. Education of public and meat handlers on nature of disease and mode of transmission. Vaccination of animals. Care in handling and disposal of discharges and fetus from an aborting animal. Inspection of all meats, especially pork and pork products.
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Early Recognition of Disease – Disinfection of body discharges. The tetracycline antibiotics generally produce rapid subsidence of fever and symptoms within several days. Relapse may occur. More satisfactory results obtained from a combination of Aureomycin and dihydrostrept-omycin over a period of at least 3 weeks. Blood transfusion may be necessary where acute anemia exists. Disease seldom fatal.
Essay # 4. Clostridium Botulinum, Types B, C, D, E:
CI. botulinum comprises a large number of toxic species conveniently divided into a non-ovolytic (CI. botulinum) and an ovolytic (CI. parabotulinum) group. Authorities are not yet in agreement on fermentation and on variant subtypes, and the present groups are only tentative and are subject to revision.
Cells rod-shaped with rounded ends, occurring singly, in pairs, and in short to occasionally long chains, measuring 0.5 to 0.8 by 3 to 8 μ. Motile with peritrichous flagella. Spores oval-shaped and located centrally, terminally, or sub-terminally. Gram-positive.
Disease Produced – The cause of botulism in man and limberneck in chickens. Pathogenic for monkeys, rabbits, guinea pigs, cats, and other animals. Produces a powerful exotoxin that is neurotoxic both on injection and on feeding.
Symptoms develop suddenly with gastrointestinal pain, headache, diarrhea or constipation, prostration, and several types of paralysis of the central nervous system, which are produced by the extracellular neurotropic toxin. Death occurs by cardiac or respiratory paralysis, usually in 3 to 7 days. Severity of symptoms depends upon the amount of toxin ingested in relation to body weight.
Diagnosis – Biological or toxicological tests may confirm presence of the organism or its toxin in suspected food.
Source of Infection – Contaminated smoked, pickled, or canned foods improperly processed. Toxin produced only under anaerobic conditions. Toxin easily destroyed by boiling, but spores inactivated only at temperature of autoclave.
Mode of Transmission – Consumption of smoked, pickled, or canned foods containing the exotoxin from containers improperly processed. Most intoxications caused by consuming home-canned foods.
Incubation Period – Usually within 18 hr. after partaking of contaminated food, possibly longer, depending upon amount of food consumed and its toxin content.
Susceptibility and Immunity – Susceptibility to toxin is general. Passive immunity with specific antitoxin of value before symptoms have appeared.
Prevalence – Sporadic cases occur in all countries, usually from home-canned food.
Prevention and Control – Inspection of commercial processing of canned and preserved foods. Education of housewives in methods for the safe processing of home-canned foods. Since the toxin is destroyed on boiling, all home-canned foods should be boiled before serving.
Specific polyvalent antitoxin will neutralize the toxin and is of value before symptoms of disease have developed.
Essay # 5. Clostridium Histolyticum:
Cells rod-shaped, occurring singly and in pairs, measuring 0.5 to 0.7 by 3 to 5 μ. Spores ovoid, sub-terminal, and cause a bulging of the rods. Motile with peritrichous flagella. Anaerobic, aerotolerant. Gram-positive.
Disease Produced – Originally isolated from war wounds. Apparently widely but sparsely dispersed in soil. Produces at least three antigenic components in toxic culture filtrates – (i) alpha, lethal and necrotizing toxin; (ii) beta, collagenase; and (iii) cysteine-activated proteinase which attacks altered collagen but not native collagen.
Intramuscular injection of small amount of culture into guinea pig produces rapid digestion of muscle tissue. Not toxic on feeding. Pathogenic for small laboratory animals.
Source of Infection – Organism found in soil.
Mode of Transmission – Disease produced by entrance of organism into the broken skin, where it multiplies and produces an extracellular cytolytic toxin.
Susceptibility and Immunity – Susceptibility to toxin is general. Exotoxin may be neutralized by injection of homologous antitoxin.
Essay # 6. Clostridium Perfringens:
Cells rod-shaped short and plump, occurring singly, in pairs, less frequently in short chains. Measuring 1 to 1.5 by 4 to 8 μ. Spores ovoid, central to excentric, and do not cause a bulging of the rods. Capsules produced. Anaerobic. Non-motile. Gram-positive.
At least 6 types have been established on the basis of variety and nature of toxins per, smear of the exudate from a present in culture filtrates. Type A is classic human gas gangrene organism; Type F, hemolytic enteritis and enteritis necroticans of humans. Antitoxin from any one type will neutralize the toxin from the other types.
Disease Produced – Isolated from wounds. This anaerobe is the most frequent cause of gas gangrene in man. The organism produces extensive necrosis and considerable gas in tissues. The gas bubbles cause an expansion in the tissues accompanied by pressure, which results in cutting off the blood supply. This causes the tissues to die. Organisms may be recovered from liver and heart blood.
CI. perfringens produces a powerful exotoxin which may be obtained in crude form by filtering a culture of the organisms. The exotoxin aids in weakening the patient. The injection of animals with culture filtrates results in the development of a potent antitoxin.
Source of Infection Soil, street dust, milk, human and animal feces.
Mode of Transmission – Disease due to entrance of organism into the broken skin or wound, where it multiplies and secretes a potent exotoxin.
Susceptibility and Immunity – Susceptibility to infection general. Passive immunity by means of antitoxin may be used for prophylaxis.
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Prevention and Control – Antitoxic serums have been used both for prophylaxis and therapeutic administration, and beneficial results have been reported.
Essay # 7. Clostridium Tetani:
Cells rod-shaped with rounded ends, occurring singly, in pairs, often in long chains and filaments, measuring 0.4 to 0.6 by 4 to 8 μ. Motile with peritrichous flagella. Spores spherical, terminal, and cause a bulging of the rod. Anaerobic. Gram-positive.
Disease Produced – The cause of tetanus in man. Disease characterized by headache, difficulty in swallowing and opening of the mouth, owing to spasms of the masseter muscles. This is accompanied by a slight stiffness of the neck and spasm of the cheek muscles. Spasms tray spread to trunk and back. Swallowing becomes increasingly difficult.
Organisms only rarely invade tissues but remain localized in the wound, where they secrete a powerful toxin. The inoculation of horses and other animals with culture filtrates results in development of a powerful antitoxin.
Diagnosis – Disease diagnosed by preparing smears from infected materials, staining by Gram’s method, and examining under the microscope for typical cells with spores.
Source of Infection – Soil, street dust, human and animal feces, especially the latter.
Mode of Transmission – Disease produced by entrance of organism into the broken skin or wound, where it multiplies and secretes a powerful exotoxin. Toxin intensely toxic on injection but not on feeding.
Incubation Period – Symptoms develop after the toxin reaches the central nervous system. This may vary from 4 days to 5 weeks, depending upon the character, extent, and location of wound.
Susceptibility and Immunity – Susceptibility is general. Active artificial immunity may be produced by use of tetanus toxoid. Three doses of 1 ml. each at intervals of 3 weeks are generally given and
are considered capable of producing a high concentration of antitoxic antibodies.
Immunity said to last for about 5 years. Toxoid precipitated by alum and given in two injections of 1 ml. each at intervals of 2 to 4 weeks has been reported to produce a greater and more rapid immunity than toxoid.
Prevalence – World-wide in distribution. Most frequent in North America among young males, and in summer months. Prevalent especially in wounds contaminated with fertile or manured soil.
Prevention and Control – Active immunization with tetanus toxoid desirable for those likely to be exposed to infection. Active immunization with toxoid advisable in infancy or early childhood.
The use of tetanus antitoxin is an effective protection against the disease. The injection of about 1500 U.S.A. units of antitoxin in slight injuries and about 2000 to 3000 U.S.A. units in more severe injuries will prevent tetanus. Since antitoxin tends to disappear, an additional injection should be given within 10 days.
After disease has developed, large doses of antitoxin are injected by spinal puncture. At the same time, an intravenous injection of about 10,000 units should be administered. The intra-spinal injection should be repeated every 24 hr. until three doses have been given. If intra-spinal doses cannot be given, larger intravenous injections should be administered.
