Read the given passage and answer the following question:
The term health is very frequently used by everybody. How do we define it? Health does not simply mean ‘absence of disease’ or ‘physical fitness’. It could be defined as a state of complete physical, mental and social well-being. When people are healthy, they are more efficient at work. This increases productivity and brings economic prosperity. Health also increases longevity of people and reduces infant and maternal mortality. When the functioning of one or more organs or systems of the body is adversely affected, characterised by appearance of various signs and symptoms, we say that we are not healthy, i.e., we have a disease. Diseases can be broadly grouped into infectious and non-infectious. A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man. Such disease-causing organisms are called pathogens. Most parasites are therefore pathogens as they cause harm to the host by living in (or on) them. The pathogens can enter our body by various means, multiply and interfere with normal vital activities, resulting in morphological and functional damage. Pathogens have to adapt to life within the environment of the host. For example, the pathogens that enter the gut must know a way of surviving in the stomach at low pH and resisting the various digestive enzymes.
The biological agents causing a disease are called pathogens. Which of the following are causative bacteria?
(i) Salmonella typhi
(ii) Streptococcus pneumoniae
(iii) Entamoeba histolytica
(iv) Wuchereria bancrofti
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (i) and (ii) only
Pathogens belong to many groups: bacteria, viruses, fungi, protozoans and helminths (worms). The question asks which of the four named organisms are bacteria.
(i) Salmonella typhi is a bacterium that causes typhoid fever. It enters the small intestine through contaminated food and water.
(ii) Streptococcus pneumoniae is a bacterium that causes pneumonia, an infection of the alveoli of the lungs.
(iii) Entamoeba histolytica is a protozoan parasite of the large intestine that causes amoebiasis (amoebic dysentery). It is not a bacterium.
(iv) Wuchereria bancrofti is a helminth, the filarial worm that causes filariasis (elephantiasis). It is not a bacterium.
So only (i) and (ii) are bacteria.
NCERT Extract:
Common Diseases in Humans – “… Salmonella typhi is a pathogenic bacterium which causes typhoid fever in human beings.”
Common Diseases in Humans – “… Bacteria like Streptococcus pneumoniae and Haemophilus influenzae are responsible for the disease pneumonia in humans which infects the alveoli (air filled sacs) of the lungs.”
Common Diseases in Humans – “… Entamoeba histolytica is a protozoan parasite in the large intestine of human which causes amoebiasis (amoebic dysentery).”
Common Diseases in Humans – “… Ascaris, the common round worm and Wuchereria, the filarial worm, are some of the helminths which are known to be pathogenic to man.”