6.7.4 Harmful Bacteria

Introduction

Bacteria are not always beneficial. Many bacteria are harmful and cause diseases in humans, animals, and plants. They also spoil food, decay materials, and produce acids that convert wine to vinegar. This topic discusses the harmful effects of bacteria, including important bacterial diseases in humans and plants.

Definition

Harmful Bacteria: Harmful bacteria are bacteria that cause diseases in humans, animals, and plants, spoil food, cause decay of materials, and produce harmful substances.

In simple words: Harmful bacteria are bacteria that cause damage and disease.

Core Concept

• Bacteria produce acids, which convert wine to vinegar.
• Bacteria cause decay of wood, leather, fabrics, etc.
• Bacteria spoil the food materials by decomposition.
• Parasitic bacteria attack plants and cause various diseases in them.
• Many human diseases are also caused by bacteria.

Detailed Explanation

Harmful Effects of Bacteria

Important Bacterial Diseases in Man

• Pneumonia
• Anthrax
• Tetanus
• Botulism
• Diphtheria
• Meningitis
• Gonorrhea
• Whooping cough
• Plague
• Urinary tract infection
• Typhoid fever
• Gastritis
• Peptic ulcer
• Cholera
• Tuberculosis
• Syphilis

• Cholera
• Typhoid
• Tuberculosis
• Pneumonia

1. Cholera

Symptoms: - The primary symptom of cholera is profuse watery diarrhea.

Causative Agent: - Cholera is caused by the bacteria *Vibrio cholerae*.

• The treatment primarily involves the timely and sufficient replenishment of fluids and electrolytes, either through oral or intravenous means.
• While antibiotics like tetracycline are not mandatory, they can help shorten symptom duration and reduce the time of excretion of the organisms.

• It is achieved mainly by public health measures that ensure a clean water supply.
• The vaccine composed of killed organisms has limited usefulness.
• A live vaccine is available in certain countries.
• The use of tetracycline for prevention is effective.
• Prompt detection of carriers is important in limiting outbreaks.

2. Typhoid

• In typhoid and other enteric (pertaining to intestine) fever, infection begins in the small intestine.
• The onset of illness is slow, with fever and constipation.
• High fever, delirium, tender abdomen, and enlarged spleen occur.
• "Rosy spots" i.e., rose-colored macules on the abdomen, are associated with typhoid fever but occur rarely.

Causative Agent: - It is caused by bacteria *Salmonella typhi*.

Treatment: - Antibiotics should be used in patients who are chronic carriers of S. typhi.

• It is prevented mainly by public health and personal hygiene measures.
• Hand washing prior to food handling, pasteurization of milk, and proper cooking of poultry, eggs, and meat are all important.
• Vaccines are available for the prevention of typhoid.

• Relate the causes of food poisoning and the hygiene conditions in restaurants.
• How can the consumption of contaminated milk potentially contribute to the spread of typhoid?

3. Tuberculosis

• Meningeal TB
• Miliary TB
• Bone TB
• Skin TB
• Abdominal TB

Here we will discuss only pulmonary TB.

• Mild fever lasts for 7–14 days and mild dry cough.
• Bluish-red raised tender cutaneous lesions on the shins and less commonly on the thighs may occur in primary tuberculosis.
• In secondary tuberculosis, there is:
• Low-grade intermittent fever usually in the evening
• Night sweats
• Weight loss
• Anorexia
• Malaise and weakness
• Dry hacking cough with blood-stained sputum
• Dull ache in the chest due to pleurisy

Causative Agent: - *Mycobacterium tuberculosis*.

Treatment: - Multiple-drug therapy is used to prevent the emergence of drug-resistant mutants during the long 6 to 9 month duration of treatment, or DOTS (directly observed treatment short course) of only two months duration.

• Prevention of the spread of the organism depends largely on the prompt identification and adequate treatment of patients who are coughing up the organism.
• The use of masks and other respiratory isolation procedures to prevent spread to medical personnel is also important.
• A vaccine containing a strain of live *Mycobacterium bovis (Bacillus Calmette-Guerin or BCG*) can be used to induce partial resistance to tuberculosis.

4. Pneumonia

• Pneumonia often begins with sudden chills, cough, and pleuritic pain.
• Sputum is red-brown "rusty" color.

Causative Agent: - *Streptococcus pneumoniae*.

Treatment: - Most pneumococci are susceptible to penicillin and erythromycin.

Important Bacterial Diseases in Plants

• Leaf spots
• Blights
• Soft rots
• Wilts
• Galls

1. Leaf Spot

• The most common symptoms of plant diseases are discrete or spreading type lesion on leaf blade.
• It is caused by bacterial pathogens through the action of toxins they produce.

• *Xanthomonas campestris* on tomato and pepper.
• *Pseudomonas syringae* on tobacco.
• *Aplanobacter sepedanium causes ring disease of potato*.

• Prevention of contact between the pathogen and the host.
• Use of disease-free seeds.

2. Blight

• When the necrotic symptoms develop very rapidly, damage the plant cell wall structure, and affect organ or shoot or even the whole plant soon gets killed.
• The symptom is called blight.
• In some cases, blight symptoms appear initially at or near the leaf tip, often at the margin, then spread downwards and inwards, drying up the leaf and the whole plant may get blighted soon, e.g., maize, rice, and oat.

• *Xanthomonas oryzae causes blight disease in rice*.
• *Erwinia amylovora causes fire blight of pears and apples*.

• Disease-free seeds.
• Suitable location.
• Removal of diseased plant by physical method.

3. Soft Rot

• When the cells of plant tissue die because of the action of pathogen, produce pectolytic and cellulolytic, rot type symptoms.
• Rotting may affect any organ of a plant including flowers and fruits.
• When the pathogen produces pectolytic enzyme, plant cell soon separates from one another because of maceration and the affected host tissue loses its coherence and leakage of water takes place from the affected cells, which are killed soon.
• The necrotized tissue becomes wet to touch and soft inconsistency, hence termed soft rot.
• Such rot is of fast-spreading nature and damages plant organs very rapidly.

• *Erwinia atroseptica* in potato.
• *Corynebacterium causes ear rot of wheat*.

Prevention: - Removal of diseased plants by physical method.

4. Wilting

• Interference with the upward transport of water with dissolved nutrients from roots through the stem into the leaves leads to loss of turgidity in the leaf blade, which becomes limp.
• Such loss of turgidity in the leaf blade increases with time and ultimately leads to wilting of leaf and drying.

• *Pseudomonas solanacearum causes wilt disease of potato*.
• *Xanthomonas campestris* causes important wilt diseases.

• Selection of disease-free seeds.
• Selecting proper dates for planting.
• Suitable location.
• Allowing proper spacing between the plants.

5. Galls

Symptoms: - These are localized outgrowth, mostly small but may be very large in some diseases.

• *Rhizobium leguminosarum causes small galls called root nodules in legumes*.
• *Pseudomonas savastonoi causes a small gall in olive plant known as olive knot*.
• *Agrobacterium tumifaciens causes large galls in many plants*.
• *Xanthomonas campestris causes galls on cotton*.

• Crop rotation.
• Removal of disease plants.
• Use of disease-free seeds.

Summary Table of Important Bacterial Diseases in Man

Summary Table of Important Bacterial Diseases in Plants

Intermediate Level

Important Bacterial Diseases in Man

Important Bacterial Diseases in Plants

Important Points

• 1. Bacteria produce acids, which convert wine to vinegar.
• 2. Bacteria cause decay of wood, leather, fabrics, etc.
• 3. Bacteria spoil the food materials by decomposition.
• 4. Parasitic bacteria attack plants and cause various diseases in them.
• 5. Many human diseases are also caused by bacteria.
• 6. Important Bacterial Diseases in Man:
• - Bacteria cause many diseases in man such as pneumonia, anthrax, tetanus, botulism, diphtheria, meningitis, gonorrhea, whooping cough, pneumonia, plague, urinary tract infection, typhoid fever, gastritis, peptic ulcer, cholera, tuberculosis, syphilis, etc.
• - Here we will discuss only cholera, typhoid, tuberculosis and pneumonia.
• 7. Cholera:
• - Symptoms: The primary symptom of cholera is profuse watery diarrhea.
• - Causative Agent: Cholera is caused by the bacteria Vibrio cholerae.
• - Treatment: The treatment primarily involves the timely and sufficient replenishment of fluids and electrolytes, either through oral or intravenous means. While antibiotics like tetracycline are not mandatory, they can help shorten symptom duration and reduce the time of excretion of the organisms.
• - Prevention: It is achieved mainly by public health measures that ensure a clean water supply. The vaccine composed of killed organisms has limited usefulness. A live vaccine is available in certain countries. The use of tetracycline for prevention are effective. Prompt detection of carriers is important in limiting outbreaks.
• 8. Typhoid:
• - Symptoms: In typhoid and other enteric (pertaining to intestine) fever infection begins in the small intestine. The onset of illness is slow, with fever and constipation. High fever, delirium, tender abdomen and enlarged spleen occur. "Rosy spots" i.e., rose colored macules on the abdomen, are associated with typhoid fever but occur rarely.
• - Causative Agent: It is caused by bacteria Salmonella typhi.
• - Treatment: Antibiotics should be used in patients who are chronic carriers of S. typhi.
• - Prevention: It is prevented mainly by public health and personal hygiene measures. Hand washing prior to food handling, pasteurization of milk, and proper cooking of poultry, eggs and meat are all important. Vaccines are available for the prevention of typhoid.
• - Science, Technology and Society Connections: Relate the causes of food poisoning and the hygiene conditions in restaurants. How can the consumption of contaminated milk potentially contribute to the spread of typhoid?
• 9. Tuberculosis:
• - There are different types of tuberculosis e.g., meningeal TB, miliary TB, bone TB, skin TB, abdominal TB etc. Here we will discuss only pulmonary TB.
• - Symptoms: Mild fever lasts for 7–14 days and mild dry cough. Bluish red raised tender cutaneous lesions on the shins and less commonly on the thighs may occur in primary tuberculosis. In secondary tuberculosis there is low-grade intermittent fever usually in the evening, night sweats, weight loss, anorexia, malaise and weakness, dry hacking cough with blood stained sputum, dull ache in the chest due to pleurisy etc.
• - Causative Agent: Mycobacterium tuberculosis.
• - Treatment: Multiple-drug therapy is used to prevent the emergence of drug resistant mutants during the long 6 to 9 month duration of treatment or DOTS (directly observed treatment short course) of only two months duration.
• - Prevention: Prevention of the spread of the organism depends largely on the prompt identification and adequate treatment of patients who are coughing up the organism. The use of masks and other respiratory isolation procedures to prevent spread to medical personnel is also important. A vaccine containing a strain of live Mycobacterium bovis (Bacillus Calmette-Guerin or BCG) can be used to induce partial resistance to tuberculosis.
• 10. Pneumonia:
• - Symptoms: Pneumonia often begins with sudden chills, cough and pleuritic pain. Sputum is red brown "rusty" color.
• - Causative Agent: Streptococcus pneumoniae.
• - Treatment: Most pneumococci are susceptible to penicillin and erythromycin.
• 11. Important Bacterial Diseases in Plants:
• - The important bacterial plant diseases are leaf spots, blights, soft rots, wilts and galls.
• 12. Leaf Spot:
• - Symptoms: The most common symptoms of plant diseases are discrete or spreading type lesion on leaf blade. It is caused by bacterial pathogens through the action of toxins they produce.
• - Cause: It is caused by Xanthomonas campestris on tomato and pepper. Pseudomonas syringae on tobacco, Aplanobacter sepedanium causes ring disease of potato.
• - Prevention: Prevention of contact between the pathogen and the host, use of disease free seeds.
• 13. Blight:
• - Symptoms: When the necrotic symptoms develop very rapidly damage the plant cell wall structure, and effect organ or shoot or even the whole plant soon gets killed. The symptom is called blight. In some cases, blight symptoms appear initially at or near the leaf tip, often at the margin then spread downwards and inwards drying up the leaf and the whole plant may get blighted soon e.g., maize, rice and oat etc.
• - Cause: Xanthomonas oryzae cause blight disease in rice, Eriwinia anylovora causes fire blight of pears and apples.
• - Prevention: Disease free seeds, suitable location and removal of diseased plant by physical method.
• 14. Soft Rot:
• - Symptoms: When the cells of plant tissue die because of the action of pathogen, produce pectolytic and cellulolytic, rot type symptoms. Rotting may affect any organ of a plant including flowers and fruits. When the pathogen produces peptolytic enzyme, plant cell soon separates from one another because of maceration and the affected host tissue loses its coherence and leakage of water takes place from the effected cells, which are killed soon. The necrotized tissue becomes wet to touch and soft inconsistency hence termed soft rot. Such rot is of fast spreading nature and damage plant organs very rapidly.
• - Cause: Eriwinia atroseptica in potato, Corynebacterium causes ear rot of wheat.
• - Prevention: Removal of diseased plants by physical method.
• 15. Wilting:
• - Symptoms: Interference with the upward transport of water with dissolved nutrients from roots through the stem into the leaves leads to loses of turgidity in the leaf blade, which becomes limp. Such loss of turgidity in the leaf blade increased with time and ultimately leads to wilting of leaf and drying.
• - Cause: Pseudomonas solanacearum causes wilt disease of potato. Xanthomonas campestris causes important wilt diseases.
• - Prevention: Selection of disease free seeds, selecting proper dates for planting and suitable location and allowing proper spacing between the plants.
• 16. Galls:
• - Symptoms: These are localised outgrowth mostly small but may be very large in some diseases.
• - Cause: Rhizobium leguminosarum causes small galls called root nodule in legumes. Pseudomonas savastonoi cause a small gall in olive plant known as olive knot. Agrobacterium tumifaciens causes large galls in many plants. Xanthomonas campestris causes galls on cotton.
• - Prevention: Crop rotation, removal of disease plants and use of disease free seeds.

Remember

• - Harmful bacteria = cause damage and disease.
• - Cholera = Vibrio cholerae; watery diarrhea.
• - Typhoid = Salmonella typhi; fever, constipation.
• - Tuberculosis = Mycobacterium tuberculosis; cough, weight loss.
• - Pneumonia = Streptococcus pneumoniae; chills, cough, rusty sputum.
• - Plant diseases = leaf spots, blights, soft rots, wilts, galls.
• - Prevention = clean water, hygiene, vaccines, disease-free seeds.

Common Mistakes

• 1. Thinking all bacteria are harmful – Many bacteria are beneficial.
• 2. Confusing the causative agents – Cholera = Vibrio cholerae; Typhoid = Salmonella typhi; Tuberculosis = Mycobacterium tuberculosis; Pneumonia = Streptococcus pneumoniae.
• 3. Confusing the symptoms – Each disease has specific symptoms.
• 4. Forgetting the treatments – Cholera = fluids and electrolytes; Typhoid = antibiotics; Tuberculosis = multiple-drug therapy/DOTS; Pneumonia = penicillin/erythromycin.
• 5. Confusing the plant diseases – Leaf spots, blights, soft rots, wilts, galls.
• 6. Forgetting the causative agents of plant diseases – Xanthomonas campestris, Pseudomonas syringae, Erwinia amylovora, etc.
• 7. Thinking vaccines are available for all diseases – Vaccines are available for cholera, typhoid, and tuberculosis (BCG).
• 8. Confusing the "rosy spots" of typhoid – They occur rarely.
• 9. Forgetting the role of hygiene – Hygiene is important in preventing cholera and typhoid.
• 10. Thinking tuberculosis only affects the lungs – Tuberculosis can affect other organs (meningeal, miliary, bone, skin, abdominal).
• 11. Confusing the types of plant diseases – Leaf spots, blights, soft rots, wilts, galls.
• 12. Forgetting the prevention methods – Clean water, hygiene, vaccines, disease-free seeds, crop rotation.

Quick Revision

• Bacteria produce acids, which convert wine to vinegar.
• Bacteria cause decay of wood, leather, fabrics etc.
• Bacteria spoil the food materials by decomposition.
• Parasitic bacteria attack plants and cause various diseases in them.
• Many human diseases are also caused by bacteria.
• Important Bacterial Diseases in Man:
• Bacteria cause many diseases in man such as pneumonia, anthrax, tetanus, botulism, diphtheria, meningitis, gonorrhea, whooping cough, pneumonia, plague, urinary tract infection, typhoid fever, gastritis, peptic ulcer, cholera, tuberculosis, syphilis, etc.
• Here we will discuss only cholera, typhoid, tuberculosis and pneumonia.
• Cholera:
• Symptoms: The primary symptom of cholera is profuse watery diarrhea.
• Causative Agent: Cholera is caused by the bacteria Vibrio cholerae.
• Treatment: The treatment primarily involves the timely and sufficient replenishment of fluids and electrolytes, either through oral or intravenous means. While antibiotics like tetracycline are not mandatory, they can help shorten symptom duration and reduce the time of excretion of the organisms.
• Prevention: It is achieved mainly by public health measures that ensure a clean water supply. The vaccine composed of killed organisms has limited usefulness. A live vaccine is available in certain countries. The use of tetracycline for prevention are effective. Prompt detection of carriers is important in limiting outbreaks.
• Typhoid:
• Symptoms: In typhoid and other enteric (pertaining to intestine) fever infection begins in the small intestine. The onset of illness is slow, with fever and constipation. High fever, delirium, tender abdomen and enlarged spleen occur. "Rosy spots" i.e., rose colored macules on the abdomen, are associated with typhoid fever but occur rarely.
• Causative Agent: It is caused by bacteria Salmonella typhi.
• Treatment: Antibiotics should be used in patients who are chronic carriers of S.typhi.
• Prevention: It is prevented mainly by public health and personal hygiene measures. Hand washing prior to food handling, pasteurization of milk, and proper cooking of poultry, eggs and meat are all important. Vaccines are available for the prevention of typhoid.
• Science, Technology and Society Connections: Relate the causes of food poisoning and the hygiene conditions in restaurants. How can the consumption of contaminated milk potentially contribute to the spread of typhoid?
• Tuberculosis:
• There are different types of tuberculosis e.g., meningeal TB, miliary TB, bone TB, skin TB, abdominal TB etc. Here we will discuss only pulmonary TB.
• Symptoms: Mild fever lasts for 7–14 days and mild dry cough. Bluish red raised tender cutaneous lesions on the shins and less commonly on the thighs may occur in primary tuberculosis. In secondary tuberculosis there is low-grade intermittent fever usually in the evening, night sweats, weight loss, anorexia, malaise and weakness, dry hacking cough with blood stained sputum, dull ache in the chest due to pleurisy etc.
• Causative Agent: Mycobacterium tuberculosis.
• Treatment: Multiple-drug therapy is used to prevent the emergence of drug resistant mutants during the long 6 to 9 month duration of treatment or DOTS (directly observed treatment short course) of only two months duration.
• Prevention: Prevention of the spread of the organism depends largely on the prompt identification and adequate treatment of patients who are coughing up the organism. The use of masks and other respiratory isolation procedures to prevent spread to medical personnel is also important. A vaccine containing a strain of live Mycobacterium bovis (Bacillus Calmette-Guerin or BCG) can be used to induce partial resistance to tuberculosis.
• Pneumonia:
• Symptoms: Pneumonia often begins with sudden chills, cough and pleuritic pain. Sputum is red brown "rusty" color.
• Causative Agent: Streptococcus pneumoniae.
• Treatment: Most pneumococci are susceptible to penicillin and erythromycin.
• Important Bacterial Diseases in Plants:
• The important bacterial plant diseases are leaf spots, blights, soft rots, wilts and galls.
• Leaf Spot:
• Symptoms: The most common symptoms of plant diseases are discrete or spreading type lesion on leaf blade. It is caused by bacterial pathogens through the action of toxins they produce.
• Cause: It is caused by Xanthomonas campestris on tomato and pepper. Pseudomonas syringae on tobacco, Aplanobacter sepedanium causes ring disease of potato.
• Prevention: Prevention of contact between the pathogen and the host, use of disease free seeds.
• Blight:
• Symptoms: When the necrotic symptoms develop very rapidly damage the plant cell wall structure, and effect organ or shoot or even the whole plant soon gets killed. The symptom is called blight. In some cases, blight symptoms appear initially at or near the leaf tip, often at the margin then spread downwards and inwards drying up the leaf and the whole plant may get blighted soon e.g., maize, rice and oat etc.
• Cause: Xanthomonas oryzae cause blight disease in rice, Eriwinia anylovora causes fire blight of pears and apples.
• Prevention: Disease free seeds, suitable location and removal of diseased plant by physical method.
• Soft Rot:
• Symptoms: When the cells of plant tissue die because of the action of pathogen, produce pectolytic and cellulolytic, rot type symptoms. Rotting may affect any organ of a plant including flowers and fruits. When the pathogen produces peptolytic enzyme, plant cell soon separates from one another because of maceration and the affected host tissue loses its coherence and leakage of water takes place from the effected cells, which are killed soon. The necrotized tissue becomes wet to touch and soft inconsistency hence termed soft rot. Such rot is of fast spreading nature and damage plant organs very rapidly.
• Cause: Eriwinia atroseptica in potato, Corynebacterium causes ear rot of wheat.
• Prevention: Removal of diseased plants by physical method.
• Wilting:
• Symptoms: Interference with the upward transport of water with dissolved nutrients from roots through the stem into the leaves leads to loses of turgidity in the leaf blade, which becomes limp. Such loss of turgidity in the leaf blade increased with time and ultimately leads to wilting of leaf and drying.
• Cause: Pseudomonas solanacearum causes wilt disease of potato. Xanthomonas campestris causes important wilt diseases.
• Prevention: Selection of disease free seeds, selecting proper dates for planting and suitable location and allowing proper spacing between the plants.
• Galls:
• Symptoms: These are localised outgrowth mostly small but may be very large in some diseases.
• Cause: Rhizobium leguminosarum causes small galls called root nodule in legumes. Pseudomonas savastonoi cause a small gall in olive plant known as olive knot. Agrobacterium tumifaciens causes large galls in many plants. Xanthomonas campestris causes galls on cotton.
• Prevention: Crop rotation, removal of disease plants and use of disease free seeds.

60-Second Revision

• Harmful bacteria = cause damage and disease.
• Cholera = Vibrio cholerae; watery diarrhea.
• Typhoid = Salmonella typhi; fever, constipation.
• Tuberculosis = Mycobacterium tuberculosis; cough, weight loss.
• Pneumonia = Streptococcus pneumoniae; chills, cough, rusty sputum.
• Plant diseases = leaf spots, blights, soft rots, wilts, galls.
• Prevention = clean water, hygiene, vaccines, disease-free seeds.
• Warning: Harmful bacteria cause diseases, food spoilage, and decay. Cholera is caused by Vibrio cholerae; typhoid by Salmonella typhi; tuberculosis by Mycobacterium tuberculosis; pneumonia by Streptococcus pneumoniae. Plant diseases include leaf spots, blights, soft rots, wilts, and galls. Prevention includes clean water, hygiene, vaccines, and disease-free seeds.