The Important Questions of Microbiology for NEET PG exam:
1. Rose-Waaler test is a?
A. Co-agglutination test
B. Latex agglutination test
C. Slide agglutination test
D. Haemagglutination test
Correct answer : D. Haemagglutination test
- Rose-Waaler test is a passive haemagglutination test.
- It is done in rheumatoid arthritis.
- Autoantibody (RA factor) in the serum acts as antibody to gamma globulin.
- RA factor can agglutinate red cells coated with globulins.
2. The vaccine for Japanese Encephalitis is?
A. Live (mutant) vaccine
B. Killed vaccine
C. Live (attenuated) vaccine
D. Live (recombinant) vaccine
Correct answer : B. Killed vaccine
- The vaccine for Japanese Encephalitis is a killed vaccine.
- The virus is grown in mouse brain and is inactivated by formalin.
- Influenza vaccine can be of various types – Live (mutant), Live (attenuated) and Live (recombinant) forms.
3. Which of the following is a human RNA virus?
Correct answer : B. Picornavirus
Electron micrograph of Hepatitis A virus virions. (Hepatitis A virus is a Picornavirus.)
The important human RNA viruses are :
4. All are true regarding superantigens except?
A. Activate very large numbers of B cells
B. Bind outside the antibody binding groove
C. Are medium sized proteins
D. Cause release of cytokines
Correct answer : A. Activate very large numbers of B cells
Molecular structure of Streptococcal superantigen Spe-H
- Superantigens activate very large number of T cells.
- They are medium sized proteins which bind outside the antibody binding groove.
- They have high resistance to proteases.
- They cause release of cytokines resulting in massive proliferation of T lymphocytes.
5. Which of the following is an intermediate level disinfectant?
B. Quaternary ammonium compound
C. Hydrogen peroxide
Correct answer : D. Iodophors
- Intermediate level disinfectants are chemicals which can kill microbial pathogens including mycobacteria and non enveloped virus, but not the spores.
- Examples include alcohol, phenolic compounds and iodophors.
- Glutaraldehyde and hydrogen peroxide are high level disinfectants.
- Quaternary ammonium compounds are low level disinfectants.
6. The best culture medium for primary isolation of H. influenzae is?
A. Chocolate agar
B. Fildes’ agar
C. Levinthal’s medium
D. Nutrient agar
Correct answer : B. Fildes’ agar
Haemophilus influenzae colonies in chocolate agar
- Fildes’ agar is made by adding peptic digest of blood to nutrient agar.
- It gives copious growth of H. influenzae and it is the best culture medium for the primary isolation of H. influenzae.
- The other media used for the isolation of H. influenzae are chocolate agar, blood agar, nutrient agar and Levinthal’s medium.
7. Which of the following is true regarding anthracoid bacilli?
A. No growth in penicillin agar
B. Growth inhibited by chloral hydrate
C. Not susceptible to gamma phage
D. No growth at 45 degree celsius
Correct answer: C. Not susceptible to gamma phage
- Anthracoid bacilli usually grow in penicillin agar.
- Their growth is not inhibited by chloral hydrate.
- They usually grow at 45 degree celsius.
- They are not susceptible to gamma phage.
- They are motile, non capsulated bacilli which grow in short chains.
8. Endemic relapsing fever is caused by all except?
A. Borrelia duttonii
B. Borrelia hermsii
C. Borrelia parkeri
D. Borrelia recurrentis
Correct answer : D. Borrelia recurrentis
Characteristic corkscrew shaped appearance of Borrelia
- Endemic relapsing fever is caused by Borreliae which normally live in their natural host rodents, or in other mammals which the vector takes feed.
- Human infection is an accidental event.
- Borrelia recurrentis causes epidemic relapsing fever.
- It was first observed by Obermeyer in the blood of patients during an epidemic in Berlin.
- It is transmitted by body lice from person to person.
- It is also called louse borne relapsing fever.
9. Brazilian purpuric fever is caused by?
A. Haemophilus haemolyticus
B. Haemophilus aphrophilus
C. Haemophilus aegyptius
D. Haemophilus parainfluenzae
Correct answer : C. Haemophilus aegyptius
Haemophilus colonies on blood agar
- Brazilian purpuric fever is caused by Haemophilus aegyptius.
- It is characterised by conjunctivitis which proceeds to fulminant septicemia in infants and children.
- There is high fatality.
- It was first recognized in Brazil in 1984.
10. Which of the following gastroenteritis viruses can spread by air?
Correct answer : C. Norovirus
Norwalk virus (classified under Norovirus genus) electron micrograph.
- Noroviruses are single stranded RNA viruses.
- They belong to the Caliciviridae family.
- They are responsible for 50% of the gastroenteritis outbreaks worldwide.
- It usually spread via faecal-oral route.
- But aerosols of the virus if inhaled, settle in the pharynx and is later swallowed.
- Researchers at the Université Laval, Québec, Canada have found out that the aerosolized virus preserved its infectivity and integrity during in vitro aerosol studies.
11. Fildes technique is used for the culture of?
A. Clostridium perfringens
B. Clostridium tetani
C. Clostridium botulinum
D. Clostridium difficile
Correct answer : B. Clostridium tetani
Tennis racket appearance of Clostridium tetani
- Clostridium tetani grows on ordinary media.
- Growth can be improved by blood and serum.
- Because of marked tendency to swarm over the surface of the agar, surface colonies are difficult to obtain.
- After incubating anaerobically for 24 hours, if the water of condensation at the bottom of a slope of nutrient agar is inoculated with a mixed cell culture, subcultures from the top of the tube will yield a pure growth of tetanus bacillus.
- This is called Fildes technique.
12. Aflatoxin is produced by the fungus?
A. Aspergillus flavus
B. Aspergillus niger
C. Penicillium marneffei
D. Candida albicans
Correct answer : A. Aspergillus flavus
Conidiophore of Aspergillus flavus
- Aflatoxin is a mycotoxin that is produced by the fungi Aspergillus flavus and Aspergillus parasiticus.
- Exposure to aflatoxin can cause hepatic necrosis later progressing to cirrhosis.
- It also acts as a carcinogen and can produce hepatocellular carcinoma.
Structure of aflatoxin B1
13. Most common fungal infection in immunocompetent individuals is?
Correct answer : C. Candidiasis
- Candidiasis is the most common fungal infection in immunocompetent individuals.
- All of the infections mentioned above are usually seen in immunocompromised patients, but they are also seen in immunocompetent persons.
- Candida is part of the normal flora of skin and mucous membranes.
- When the normal flora is altered by the use of antibiotics / other factors, candida can cause infection.
Candida albicans – SABHI agar plate culture
14. All of the following are non photochromogens except?
A. Mycobacterium ulcerans
B. Mycobacterium xenopi
C. Mycobacterium avium
D. Mycobacterium marinum
Correct answer : D. Mycobacterium marinum
CLASSIFICATION OF NON TUBERCULOUS MYCOBACTERIA:
- Photochromogens – produce pigment when exposed to light. eg: M. kansasii, M. marinum.
- Scotochromogens – produce pigment in the dark. eg: M. scrofulaceum, M. gordonae.
- Non photochromogens – do not produce pigment even when exposed to light. eg: M. ulcerans, M. xenopi, M. avium.
- Rapid growers – growth within seven days. eg: M. fortuitum, M. chelonae.
15. Which of the following is an enrichment medium?
A. Alkaline peptone water
B. Loeffler serum slope
C. Deoxycholate citrate agar
D. MacConkey’s agar
Correct answer : A. Alkaline peptone water
- Enrichment medium is a liquid medium which selectively favours the growth of certain pathogenic bacteria and inhibits commensal bacteria.
- Loeffler’s serum slope is an enriched medium.
- Deoxycholate citrate agar is a selective medium.
- MacConkey’s agar is a differential medium.
16. A seven year old boy presented to the OPD with complaints of pain and discharge from left ear. On examination the patient was febrile with neck rigidity and positive Kernig’s sign. Gram positive cocci were visualised in the gram stained specimen of the discharge. Most likely pathogen is?
A. Streptococcus pneumoniae
B. Staphylococcus aureus
C. Haemophilus influenzae
D. Staphylococcus epidermidis
Correct answer : A. Streptococcus pneumoniae
Scanning Electron Micrograph of Streptococcus pneumoniae
(colour added for illustrative purposes)
- The history and clinical features are suggestive of otitis media with meningitis.
- Pneumococci are the most common cause of otitis media in children.
Exclusion of the other options:
- Haemophilus influenzae is a gram negative bacilli
- Streptococcus pneumoniae and Staphylococcus epidermidis are not commonly implicated in the causation of otitis media
17. In ‘C Reactive Protein’, the letter ‘C’ is short for?
C. Capsular polysaccharide of pneumococcus
D. Concanavalin A
Correct answer : C. Capsular polysaccharide of pneumococcus
Structure of C Reactive Protein
C REACTIVE PROTEIN (CRP)
- It is an annular pentameric protein seen in blood plasma.
- It was given its name because it was first identified in the serum of patients which reacted with capsular polysaccharide of pneumococcus.
- The levels of CRP increases in inflammatory states (acute phase protein).
- It activates the complement system by binding to phosphocholine expressed on the surface of some bacteria and dead cells.
- It is synthesised in the liver.
18. Which of the following does not have polysaccharide capsule related antigen antibody response?
A. Haemophilus influenzae
B. Neisseria meningitidis
C. Streptococcus pneumoniae
D. Bordetella pertussis
Correct answer : D. Bordetella pertussis
Scanning Electron Micrograph of Streptococcus pneumoniae showing polysaccharide capsule
POLYSACCHARIDE CAPSULE RELATED ANTIGEN ANTIBODY RESPONSE
- Polysaccharide capsule in an important virulence factor in many organisms like:
- Haemophilus influenzae
- Neisseria meningitidis
- Streptococcus pneumoniae
- Klebsiella pneumoniae
- Salmonella typhi
- Antibodies against the capsule protect against infection
- The capsule can be used for producing conjugate polysaccharide vaccines (for H. influenzae, N. meningitidis and S. pneumoniae)
- Patients with B cell dysfunction, asplenia (as in sickle cell disease / after splenectomy) and complement defects are highly susceptible to infection with encapsulated organisms
19. Erythema chronicum migrans is caused by?
A. Borrelia japonica
B. Borrelia burgdorferi
C. Borrelia andersonii
D. Borrelia recurrentis
Correct answer : B. Borrelia burgdorferi
ERYTHEMA CHRONICUM MIGRANS
- Erythema chronicum migrans is a rash often seen in the early stages of Lyme disease.
- It is caused by the spirochete Borrelia burgdorferi.
- Lyme disease is a zoonosis which is spread to humans by tick bite
- The rash appears a few days after the tick bite
20. Latent varicella zoster infection is found in?
A. T cells
B. B cells
D. Trigeminal ganglion
Correct answer : D. Trigeminal ganglion
Latent varicella zoster virus is found in sensory ganglia.
21. Which of the following parasites can cause biliary obstruction?
A. Clonorchis sinensis
B. Enterobius ( Pin worm)
C. Strongyloides stercoralis
D. Ancylostoma duodenale
Correct answer : A. Clonorchis sinensis
Parasites which can cause biliary obstruction:
- Cestodes – Echinococcus granulosus
- Trematodes – Fasciola hepatica, Opisthorchis, Clonorchis sinensis
- Nematodes – Ascaris lumbricoides
22. Draughtsman appearance is seen with colonies of:
D. None of the above
Correct answer: A. Pneumococcus
Appearance of pneumococcus colonies after prolonged incubation in blood agar – with concentric rings and central umbonation – also called carrom coin appearance.
23. False statement about streptococcus:
A. Cell division occurs along a single axis
B. Part of normal flora in human beings
C. Causes localized infections which do not spread along tissue planes
D. Daughter cells after cell division form a string
Correct answer: C. Causes localiszed infections which do not spread along tissue planes.
Streptococci are gram positive bacteria that are arranged in chains. Cell division takes place along a single axis without separation of daughter cells. Hence they get arranged in chains. They are part of the normal flora of humans. But some of them are pathogens. Most important among them is Streptococcus pyogenes causing pyogenic infections that tend to spread along the tissue planes. (This is in contrast to Staphylococcus infections that tend to be localised.)
24. All are true regarding Campylobacter jejuni except?
A. It is the commonest cause of campylobacteriosis
B. Humans act as important reservoirs
C. It is associated with Guillian Barre syndrome
D. Poultry is a common source of infection
Correct answer :B. Humans act as important reservoirs
- Humans do not act as reservoirs for Campylobacter jejuni
- Important reservoirs are poultry, cattle, swine and household pets
25. All of the following statements regarding Corynebacterium diphtheriae are true, except?
A. It can be identified by using tests for toxigenicity
B. The toxin inhibits protein synthesis
C. Toxin has adverse effects on cardiovascular and nervous systems
D. Native chromosome is responsible for toxin production
Correct answer : D. Native chromosome is responsible for toxin production
Toxin production is mediated by toxigenic bacteriophages. The gene is transmitted via transduction.
26. False regarding Methicillin Resistant Staphylococcus aures (MRSA) ?
A. Resistance may be produced by increased production of beta lactamase enzyme
B. Resistance is primarily plasmid mediated
C. Resistance is due to altered Penicillin Binding Proteins
D. Resistance may be missed at incubation temperature of 37°C during susceptibility testing
Correct answer : B. Resistance is primarily plasmid mediated
Resistance is mediated by the MeC-A gene which codes for altered Penicillin Binding Proteins. MeC-A gene is part of nuclear chromosomes.
27. False regarding Pneumococcus is?
A. Causes mild form of meningitis
B. Respiratory tract of carriers is the most important source of infection
C. Commonest cause of otitis media
D. Capsule is important in virulence
Correct answer : A. Causes mild form of meningitis
Pneumococcal meningitis is very severe and is fatal if untreated.
28. A patient presented to the OPD with clinical features of pneumonia. Sputum examination of the patient revealed a gram positive cocci with alpha hemolysis on sheep agar. Which test will you do to confirm the diagnosis?
A. Coagulase test
B. Bacitracin sensitivity
C. CAMP test
D. Bile solubility
Correct answer : D. Bile solubility
- The clinical features and microbiological characteristics are suggestive of pneumococcal pneumonia
- The diagnosis can be confirmed by Bile solubility and Optochin sensitivity
29. False about pneumococcus is?
A. Capsule aids in virulence
B. Commonest cause of otitis media and pneumonia
C. Meningitis caused by it is milder than by other organisms
D. Bile sensitive
Correct answer : C. Meningitis caused by it is milder than by other organisms
Pneumococcal meningitis is a very serious condition.
30. Which of the following statements is true regarding ARBO viruses :
A. Yellow fever is endemic in India
B. Dengue virus has only one serotype
C. Kyasanur Forest disease (KFD) is transmitted by ticks
D. Mosquito of culex vishnui complex is the vector of Dengue fever
Correct answer : C. Kyasanur Forest disease (KFD) is transmitted by ticks
Yellow fever is not present in India
Dengue virus has 4 serotypes.
Dengue fever is transmitted by aedes mosquito
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