Bacterial Diseases Archives

1. An important cause of tooth decay by the bacterium Streptococcus mutan

An important cause of tooth decay by the bacterium Streptococcus mutans is because of their ability to attach to teeth surface by producing slime layer from

Sugar

Alcohol

Saliva

Teichoic acid

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This question was previously asked in

UPSC NDA-2 – 2023

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Streptococcus mutans metabolizes dietary sugars, particularly sucrose, to produce acids that demineralize tooth enamel (causing decay) and to synthesize extracellular polysaccharides (glucans and fructans). These sticky polysaccharides form a ‘slime layer’ or matrix which allows the bacteria to adhere firmly to the tooth surface and form dental plaque (biofilm).

Streptococcus mutans is a key bacterium in the initiation of dental caries (tooth decay). It produces both acid and a sticky matrix from fermentable carbohydrates, primarily sugars.

While saliva plays a role in buffering acids and clearing food debris, it is not used by the bacteria to produce the sticky layer. Teichoic acid is a component of the bacterial cell wall, contributing to cell shape and adhesion, but the bulk of the slime layer is composed of polysaccharides synthesized from dietary sugars. Alcohol is generally not relevant to this process in the context of dietary intake leading to decay.

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2. Which one of the following is a bacterium that causes disease in the h

Which one of the following is a bacterium that causes disease in the human body ?

Varicella zoster

Trypanosoma gambiense

Salmonella typhi

Plasmodium falciparum

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This question was previously asked in

UPSC NDA-2 – 2019

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The correct option is C) Salmonella typhi.

The question asks to identify a bacterium from the given options that causes disease in humans.

Salmonella typhi is a rod-shaped, Gram-negative bacterium that causes typhoid fever in humans. Varicella zoster is a virus (causes chickenpox and shingles). Trypanosoma gambiense is a protozoan (causes African sleeping sickness). Plasmodium falciparum is a protozoan (causes malaria).

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3. Which one of the following is caused by a bacterial pathogen?

Which one of the following is caused by a bacterial pathogen?

AIDS

Dengue fever

COVID-19

Typhoid fever

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This question was previously asked in

UPSC NDA-1 – 2022

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Typhoid fever is caused by the bacterium *Salmonella Typhi*. AIDS is caused by the Human Immunodeficiency Virus (HIV). Dengue fever is caused by the Dengue virus. COVID-19 is caused by the SARS-CoV-2 virus. Therefore, Typhoid fever is the only disease among the options caused by a bacterial pathogen.

Pathogens can be viruses, bacteria, fungi, or parasites. It is important to know the type of pathogen causing common diseases.

Typhoid fever is typically spread through contaminated food or water. It is a serious illness characterized by high fever, fatigue, abdominal pain, and sometimes a rash. Antibiotics are used to treat bacterial infections like typhoid fever.

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4. Which one of the following statements regarding Cholera is correct ?

Which one of the following statements regarding Cholera is correct ?

Cholera is a disease that causes loss of memory

Cholera is a disease of muscles due to consumption of alcohol

Cholera is a disease due to consumption of contaminated food or water

Cholera is a genetic disease

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This question was previously asked in

UPSC NDA-1 – 2019

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Cholera is a disease due to consumption of contaminated food or water.

Cholera is caused by the bacterium Vibrio cholerae, which is transmitted through the fecal-oral route.

Ingestion of water or food contaminated with the feces of an infected person is the primary mode of transmission. The bacterium produces a toxin that causes severe watery diarrhea, leading to rapid dehydration. It is not a genetic disease, nor primarily related to alcohol consumption or causing loss of memory.

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5. Which one of the following statements regarding Penicillin is correct

Which one of the following statements regarding Penicillin is correct ?

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Penicillin resistant bacteria can store this antibiotic in vacuole

Penicillin resistant bacteria can degrade this antibiotic by an enzyme called β-lactamase

Penicillin resistant bacteria can degrade this antibiotic by an enzyme called lactic acid dehydrogenase

Penicillin is not absorbed by bacteria, so most bacteria are resistant

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UPSC NDA-1 – 2019

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Penicillin resistant bacteria can degrade this antibiotic by an enzyme called β-lactamase.

Beta-lactamase enzymes break the beta-lactam ring structure, which is essential for the activity of penicillin and related antibiotics.

Bacterial resistance to antibiotics, including penicillin, is a significant public health challenge. Different bacteria have evolved various mechanisms to resist antibiotics, with beta-lactamase production being one of the most common for resistance to penicillin.

6. Antibiotic such as penicillin blocks

Antibiotic such as penicillin blocks

cell wall formation in bacteria

RNA synthesis in bacteria

DNA synthesis in bacteria

division in bacteria

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This question was previously asked in

UPSC CDS-2 – 2020

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Antibiotics such as penicillin work by interfering with the synthesis of the bacterial cell wall, specifically the peptidoglycan layer.

Penicillin inhibits the transpeptidase enzymes (also known as penicillin-binding proteins or PBPs) that cross-link the peptidoglycan chains, which are essential for the structural integrity of the bacterial cell wall. This weakens the wall, leading to cell lysis (bursting) due to osmotic pressure.

Different classes of antibiotics target different processes in bacteria, such as protein synthesis (e.g., tetracyclines, erythromycin), DNA synthesis (e.g., quinolones), RNA synthesis (e.g., rifampicin), or metabolic pathways (e.g., sulfonamides).

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7. Apart from hyper acid secretion, peptic ulcers are also developed due

Apart from hyper acid secretion, peptic ulcers are also developed due to bacterial infection. The causative agent is

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Helicobacter pylori

E. coli

Streptococcus pneumoniae

Salmonella typhimurium

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UPSC CDS-2 – 2020

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The causative agent for peptic ulcers apart from hyper acid secretion is Helicobacter pylori.

For a long time, peptic ulcers (ulcers in the lining of the stomach or duodenum) were primarily attributed to lifestyle factors like stress and diet leading to excessive acid production. However, research by Barry Marshall and Robin Warren in the 1980s revolutionized the understanding of peptic ulcers by demonstrating that the bacterium *Helicobacter pylori* is a major cause. This bacterium can survive in the acidic environment of the stomach and colonize the gastric lining, causing inflammation and making the tissue vulnerable to acid damage, leading to ulcer formation.

The discovery of *H. pylori*’s role in peptic ulcers was initially met with skepticism but was eventually accepted, leading to new treatment regimens involving antibiotics to eradicate the bacterium. Marshall and Warren were awarded the Nobel Prize in Physiology or Medicine in 2005 for this discovery. While *H. pylori* is a primary cause, hyper acid secretion, NSAID use, smoking, and stress can also contribute to ulcer development or exacerbate existing ones.

8. Statement I : A person may suffer from tuberculosis if she/he frequent

Statement I :
A person may suffer from tuberculosis if she/he frequently visits crowded place.
Statement II :
Bacteria of tuberculosis spread through droplets by sneezing or coughing.

Option text is missing in the image.

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This question was previously asked in

UPSC CDS-1 – 2018

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Statement I is true. Tuberculosis (TB) is a contagious disease that spreads through the air. Spending time in crowded places increases the likelihood of being exposed to airborne pathogens from infected individuals. Statement II is also true. The bacteria that cause TB, *Mycobacterium tuberculosis*, are primarily transmitted from person to person through tiny droplets released into the air when a person with active pulmonary TB coughs, sneezes, speaks, or sings. Statement II provides the mechanism (airborne droplet spread) that explains why being in crowded places (where people are in close proximity and may be infectious) increases the risk of contracting TB, as stated in Statement I. Therefore, Statement II is the correct explanation for Statement I.

Tuberculosis is an airborne infectious disease. Transmission occurs through inhaling infectious droplets.

Factors that increase the risk of TB infection and disease include close contact with an infectious person, crowded living conditions, poor ventilation, malnutrition, and weakened immune systems (e.g., due to HIV, diabetes).

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