Diseases caused by bacteria

1. Cholera

This is an acute infectious disease caused by Vibrio cholerae.

These may get into a healthy person with contaminated food and water.


The patient starts passing stools frequently, which are white like rice water and gets repeated vomiting.

Since a large quantity of fluid and salts are rapidly lost through stools and vomit, therefore, the most important dore treatment is to replace the lost fluid and salts equally rapidly.

Rapid replacement of fluid and electrolytes is done by oral rehydration therapy.

2. Diphtheria

This disease is caused by Corynebacterium diphtheriae usually affecting children up to five years of age.

It may start as sore throat, chills with mild fever, sometimes vomiting and headache.


The throat and or tonsils show a grey membrane which may spread down and cause hoarseness and difficulty in breathing.

The nose may be affected giving rise to a blood-tinged nasal discharge from one nostril.

If the disease is not treated early and properly, the toxin produced by the germs affects the heart and the nervous system and proves fatal.


The most important preventive measure against this disease is that all babies should be, immunized within the first six weeks of birth using DPTvaccine.

DPT stands for Diphtheria, Pertussis and Tetanus.

3. Whooping Cough (Pertussis)

It is caused by Bordetella pertussis which comes out while coughing from the discharges of the nose and throat of the patient.

It is a highly infectious disease in young children causing inflammation of the respiratory passages with severe attacks of cough. The cough becomes troublesome, especially at night.


It spreads by direct inhalation of droplets from the patient or the carrier, or by the articles freshly soiled by the discharges. The face becomes red during coughing.

These repeated bouts of violent cough end in a whoop.

The Whooping sound is produced due to the rushing in of air during deep inspiration at the end of a bout of cough. The child usually vomits and there is frothy discharge from his mouth and nose.


The disease can be prevented by immunizing all infants with the whooping cough vaccine which is available singly or in combination as a triple vaccine (i.e., DPT).

4. Tetanus (Lock Jaw)

It is caused by Clostridium tetani.

The first indications of this disease are irritability and restlessness, the neck becomes stiff and there is difficulty in chewing and swallowing. Subsequently, spasms of muscles of the jaw and face take place and thus “Lock Jaw” occurs.

There is severe pain. It is often a fatal disease. The toxin affects ‘voluntary muscles’ mainly.

Transmission and Precautions

Tetanus organisms live in the intestine of horses and other animals without doing any harm.

The spores are, therefore, abundant in the soil manufactured with animal dung.

Spores may survive for 60 or more years in contaminated soil.

On entering the body by way of wounds, the spores release active bacteria.

The latter multiply and secrete powerful exotoxin into the tissue and blood.

The exotoxin known as Tetanospasmin brings about tetanus.

Anti-tetanus serum (ATS) injection should be administered in case of an injury.

5. Leprosy (Hansen’s Disease)

This disease is caused by Mycobacterium leprae, which was discovered by Hansen.


Symptoms of leprosy include the appearance of light-colored patches on the skin, thickening of the nerves, and partial or total loss of sensation in the affected parts of the body.

These are accompanied by fever, pain, ulcers and skin eruptions.

Deformities of toes and fingers may also develop.

The bacilli leave the body in nasal discharge, from the throat during coughing, sneezing and even speaking and through broken skin lesions.


The patient is treated with DDS (diamino diphenyl sulphone).

6. Tuberculosis (TB)

It is also called Koch’s disease. It a caused by Mycobacterium tuberculosis.

The bacteria damage the tissues and release a toxin named tuberculin which produces the disease.

It affects the lungs, lymph nodes, bones and joints.

The incubation period is quite variable.


Symptoms of pulmonary (lung) tuberculosis are fever, cough, blood-containing sputum, pain in the chest and loss of weight, excessive fatigue, failure of appetite, rise of temperature in the evening, hoarseness of throat, night sweating and rapid pulse.

BCG vaccine gives considerable protection against tuberculosis.

BCG (Bacille Calmette-Guerin)

7. Pneumonia

This disease is caused by Diplococcus pneumoniae.

Pneumonia is a serious disease of the lungs.

Lymph and mucus collect in the alveoli and bronchioles of the lungs so that the lungs do not get sufficient air.

Therefore, proper exchange of gases does not take place in the alveoli. It usually lowers body resistance.

The infection spreads by the sputum of the patient. Breathing rate increases with high-grade fever. Common in children below the age of 5 years.

8. Plague

This disease is characterized by a high fever and a bubo (painful swelling) in the groin or the armpit.

The plague is caused by Yersinia pestis, a deadly bacterium.

It is primarily a disease of rodents but it accidently affects man.

It goes from rat to rat through the rat fleas.

But when the rats die of the plague, the fleas leave the dead rat and if any man is round about, they bite him and accidentally inject into his blood some plague germs.

In its typical form, the bubonic plague is not transmitted from one man to the other, but always from a rat to one or more men.

9. Typhoid

It is an infectious disease caused by a Gram-negative bacterium called Salmonella typhi which is a non-spore-forming bacillus.


Typhoid germs are contracted from food or drink contaminated with excreta from carriers or patients.

The spread is facilitated by poor environmental hygiene. Immunity following the infection is not sufficient to prevent relapse.

The acid in the stomach destroys Salmonella that is ingested. Hence, patients having achlorhydria (no acid in the stomach) or who take large amounts of antacids to neutralize the acid in the stomach suffer more often from typhoid.

The normal intestinal flora produces short-chain fatty acids which are lethal to Salmonella.

When this is reduced by antibiotics, the patient is more prone to typhoid.

Salmonella that cause enterocolitis after ingestion, invade the mucosal cells and multiply within them.

They do not penetrate beyond lamina propria and multiply in the lymphoid tissues (Peyers patches) of the small intestine.

Inflammatory changes occur with accumulation of leucocytes.

Enterotoxin liberated by the bacteria may form abscess which may burst causing ovoid ulcers.

This may cause haemorrhage and if the ulcer reaches the serosa, perforation occurs leading peritonitis.

The infection is usually localised in the small intestine and colon.

The incubation period is usually 12-72 hours but may be up to 2 weeks.

Nausea, vomiting and an early chill are common initially followed by colicky abdominal pain and diarrhoea of watery, green, offensive stools.

Blood mixed with stool and high fever may occur if there is involvement of colon.


Symptoms may subside within a week or two.

There is a clinical syndrome characterized by fever, headache, cough, splenomegaly and leucopenia.

This is called enteric fever.

The fever is continuous in type which rises in a step-wise manner.

Diagnosis is done by the Widal test which determines the agglutinins against the antigen.

The test is usually positive in the 2nd week of the disease.

The concentration of agglutinins must keep on rising with time to suggest the disease.

The treatment involves use of antibiotics, antipyretics and rest. TAB vaccine is useful against typhoid.

Special care must be taken to ensure that persons who are engaged as cooks or work in eating establishments are not ‘carriers’ of this disease who can keep spreading this disease through food.

A classical example of a typhoid carrier recorded in history was Mary Mallon who was a cook. She was known as typhoid mary.

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