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Dr.Niraj Mahajan
Dr.Niraj Mahajan
Dr.Niraj Mahajan


Microbiology MCQ

By AdminPosted On 05-Oct-2016

1. In ‘C Reactive Protein’, the letter ‘C’ stands for?

a) Cellular

b) Cytoplasmic

c) Capsular polysaccharide of pneumococcus

d) Concanavalin A

e) Complement system

Correct Answer: c) Capsular polysaccharide of pneumococcus. CRP was so named because it was first identified as a substance in the serum of patients with acute inflammation that reacted with the C-polysaccharide of Pneumococcus.

2. Characteristic green color to pus is due to?

a) Collagenase

b) Elastase

c) Myeloperoxidase

d) All of the above

Correct Answer: c) Myeloperoxidase is peroxidase enzyme ans is most abundantly expressed in neutrophil granulocytes. It has a heme pigment, which causes its green color in secretions rich in neutrophils, such as pus and some forms of mucus. confers the characteristic green color to pus and may participate in turning off the inflammatory process by inactivating chemoattractants and immobilizing phagocytic cells.

3. Rigid Cell Wall : Microbiology MCQ

Which organisms contain ribosomes, do not have a rigid cell wall but cannot be grown on inanimate culture?

a) Bacteria

b) Chlamydia

c) Mycoplasma

d) Rickettsiae

e) Viruses

Correct Answer: b) Chlamydia. Bacteria and mycoplasma can be grown on culture, rickettsiae have a rigid cell wall and viruses do not have ribosomes.

4. Smallpox : Microbiology MCQ

The first disease to be eradicated from the human population was

a) smallpox.

b) bubonic plague.

c) the black death.

d) measles.

e) chickenpox.

Correct Answer: a) smallpox. After vaccination campaigns throughout the 19th and 20th centuries, the WHO certified the eradication of smallpox in 1979. Smallpox is one of two infectious diseases to have been eradicated, the other being rinderpest, which was declared eradicated in 2011. Black death is another term for plague, which has not been eradicated from the human population.

5. Smallpox Vaccine : Microbiology MCQ

The scientist who introduced a vaccination procedure for smallpox was

a) Hooke.

b) Jenner.

c) Pasteur.

d) Koch.

e) Lister.

Correct answer: b) Jenner. Edward Jenner, was the pioneer of smallpox vaccine, the world's first vaccine. He is often called "the father of immunology". In 1798 he published all his research into smallpox in a book entitled: "An Inquiry into the Causes and Effects of the Variolae Vaccinae". Pasteur did not work on a vaccination for smallpox. He developed pasteurization to destroy unwanted organisms and worked on disproving the theory of spontaneous generation.

6. Virus : Microbiology MCQ

Acellular, non-living agents consisting of a protein coat that surrounds a nucleic acid core are called

a) viruses.

b) prions.

c) prokaryotes.

d) viroids.

e) nucleoproteins.

Correct Answer: a) Viruses. Prokaryotes are cells, meaning they are living agents. Prions consist of protein only. Viroids consist of a short piece of nucleic acid without a protective coat. Nucleoprotein is not the term used for the agent described in the question.

7. Bioremediation : Microbiology MCQ

The process of using microbes to destroy dangerous chemicals and pollution in the environment is called

a) recombinant DNA technology.

b) biotechnology.

c) bioremediation.

d) microbial transformation.

e) microbial transduction.

Correct Answer: c) bioremediation is a waste management technique that involves the use of organisms to remove or neutralize pollutants from a contaminated site. Biotechnology is the use of microbiological and biochemical techniques to solve practical problems and produce more useful products. Bioremediation is the biotechnological process specifically described in the question. Bioremediation may occur on its own (natural attenuation or intrinsic bioremediation) or may only effectively occur through the addition of fertilizers, oxygen, etc., that help encourage the growth of the pollution-eating microbes within the medium (biostimulation). For example, the US Army Corps of Engineers demonstrated that windrowing and aeration of petroleum-contaminated soils enhanced bioremediation using the technique of landfarming.

8. Pasteurization : Microbiology MCQ

A process in which wine, beer, and milk are heated to destroy microorganisms that cause spoilage and increase the shelf life of these products is called

a) centrifugation.

b) sterilization.

c) pasteurization.

d) autoclaving.

e) polymerization.

Correct Answer: c) pasteurization. Pasteurisation, is a process invented by Louis Pasteur during the nineteenth century. Pasteur discovered that heating milk to a high temperature then swiftly cooling it before bottling it, enabled the milk to remain fresher for an extended period of time. Today the process of pasteurizaton is used widely in the drinks and food industry. This process slows spoilage caused by microbial growth.

Unlike sterilisation, pasteurization is not intended to kill all micro-organisms in the food. Instead, it aims to reduce the number of viable pathogens so they are unlikely to cause disease (assuming the pasteurized product is stored as indicated and is consumed before its expiration date).

9. Microscope : Microbiology MCQ

If microscope has a 10X ocular lens and you are using the 40X objective lens, what is the total magnification?

a) 100X

b) 1000X

c) 50X

d) 400X

e) The magnification cannot be determined

Correct answer: d) 400X. Magnification is calculated by multiplying the ocular magnification by the objective lens magnification.

10. Arctic Region : Microbiology MCQ

A microorganism isolated from the Arctic region would most likely be

a) a mesophile.

b) facultative.

c) a psychrophile.

d) extremophilic.

e) a psychrotroph.

Correct Answer: c) a Psychrophile. They are present in alpine and arctic soils, high-latitude and deep ocean waters, polar ice, glaciers, and snowfields. They are of particular interest to astrobiology. Mesophiles live in more moderate temperature and therefore would not likely be found in the Arctic. Facultative alone does not describe a particular microorganism's optimum growth environment. Extremophilic is too general a term. psychrotrophs live in cold temperatures, but not as extreme as in the Arctic.

11. What type of fungus is Candida albicans?

a) Dimorphic fungus

b) Filamentous fungus

c) Trimorphic fungus

d) True yeast

e) Yeast-like fungus

Correct Answer: e) Yeast-like fungus. Unlike true yeasts, Candida forms long-branching filaments and therefore, it is classified as a yeast-like fungus.

12. Gram Stain : Microbiology MCQ

The Gram stain is a valuable procedure because

a) It can be used to distinguish members of the genera Mycobacterium and Nocardia from other bacterial containing


b) It can be employed to divide bacteria into two broad groups

useful as an aid in diagnostic bacteriology

c) It selectively identifies encapsulated organisms

d) It utilizes the single application of an aniline dye to a smear followed by acid-alcohol treatment

e) It differentiates between flagellated and piliated organisms

Correct Answer: b) It can be employed to divide bacteria into two broad groups useful as an aid in diagnostic bacteriology. i.e. gram-positive and gram-negative based on the physical properties of their cell walls. Gram staining has proven as effective a diagnostic tool as PCR, particularly with regards to gonorrhoea diagnosis in Kuwait. The similarity of the results of both Gram stain and PCR for diagnosis of gonorrhea was 99.4% in Kuwait.

13. Bartholin's Abscess : Microbiology MCQ

Commonest organism isolated from Bartholin's abscess

a) Treponema pallidum

b) Trichomonal vaginalis

c) Neisseria gonorrhoea

d) Lymphogranuloma venereum

e) Escherichia coli

f) Bacteroides species

g) Chlamydia trachomatis

Correct Answer: e) Escherichia coli. Bartholin's duct abscess is mainly caused by opportunistic bacteria, and sexually transmitted pathogens are rarely involved in its pathogenesis. E coli is the most commonly isolated organism in all recent studies in last 15 years. Gonococci and chlamydia are being isolated in

14. Chlamydia Proctitis : Microbiology MCQ

Is a single 1 g. dose of azithromycin given orally acceptable treatment for non-LGV (lymphogranuloma venereum) chlamydia proctitis?

a) Yes

b) No

Correct Answer: Probably a) Yes, however, this is a rather theoretical question as the determination of an LGV diagnosis through genotyping will take considerable time (if possible at all) from the time of presentation. When a patient presents with proctitis signs and symptoms, he should be given treatment to cover both gonorrhea and chlamydia if an exudate is present and/or a gram-stained smear shows > 10 PMNL/HPF. The current guidelines suggest a single 250 mg. intramuscularly injected dose of ceftriaxone, accompanied by doxycycline 100 mg. orally twice daily. If painful ulcerations are present perianally or on anoscopy, then treatment for herpes should be considered, in addition to three weeks of doxycycline therapy to cover for LGV while lab tests are pending.

15. Bloody Diarrhoea : Microbiology MCQ

18 weeks pregnant woman presents with bloody diarrhoea. Stool microscopy and culture identifies Gram-negative, facultative anaerobic rods. Which organism is most likely to be responsible?

a) Borrelia

b) Campylobacter

c) Salmonella

d) Staphylococcus

e) Streptococcus

Correct Answer: c) Salmonella. Only Salmonella fits the microscopic findings and the clinical features. Salmonella is a facultative anaerobe, meaning that although it will grow aerobically, it's growth is facilitated if grown under lower O2 concentrations... just like E. coli. It is this property that helps these organisms reside in the gut.

16. What is the incubation period of Rubella?

a) 5–7 days

b) 10–14 days

c) 13–20 days

d) 14–21 days

e) 14–28 days

Correct Answer: c) 13–20 days. Rubella is caused by a single-stranded RNA togavirus. During this incubation period, the patient is contagious typically for about one week before he/she develops a rash and for about one week thereafter.

17. Germ Tube Test : Microbiology MCQ

Germ tube test is used in the diagnosis of which of the following?

a) Candida albicans

b) Fallopian tube patency

c) Pregnancy

d) Ovarian reserve

e) Ovulation

Correct Answer: a) Candida albicans. A germ tube is an outgrowth produced by spores of spore-releasing fungi during germination.

The germ tube differentiates, grows, and develops by mitosis to create somatic hyphae.

A germ tube test is a diagnostic test in which a sample of fungal spores are suspended in serum and examined by microscopy for the detection of any germ tubes. It is particularly indicated for colonies of white or cream color on fungal culture, where a positive germ tube test is strongly indicative of Candida albicans.

18. Ribosomes similar to those of bacteria are found in

a) Plant nuclei

b) Cardiac muscle cytoplasm

c) Pancreatic mitochondria

d) Liver endoplasmic reticulum

e) Neuronal cytoplasm

Correct Answer: c) Pancreatic mitochondria. The ribosome is responsible for the synthesis of proteins in cells. Even though mitochondria possess ribosomes similar to the bacterial ones, mitochondria are not affected by these antibiotics because they are surrounded by a double membrane that does not easily admit these antibiotics into the organelle.

19. Bacteria : Microbiology MCQ

a) Are eukaryotic

b) All have a cytoplasmic membrane

c) All have cell walls

d) All have pili (fimbriae)

e) All have mitochondria

Correct Answer: b) All have a cytoplasmic membrane. Mycoplasmas are unique among bacteria in not having a rigid cell wall. The adjective prokaryotic’ distinguishes the absence of membrane-bound organelles characteristic of bacteria from the ‘eukaryotic’ cell characterized by the presence of a nuclear membrane.

20. Ionizing radiation kills microorganisms by

a) damaging DNA.

b) cytoplasmic membranes.

c) producing reactive oxygen species.

d) All of these choices are correct.

e) None of these choices are correct.

Correct Answer: d) All of these choices are correct. Food irradiation is a technology for controlling spoilage and eliminating food-borne pathogens, such as salmonella. Like pasteurization,

irradiation kills bacteria and other pathogens, that could otherwise

result in spoilage or food poisoning. Bulk or packaged food passes through a radiation chamber on a conveyor belt. The food does not come into contact with radioactive materials, but instead passes through a radiation beam, like a large flashlight.

21. Bacteria Structure : Microbiology MCQ

Which of the following statement about bacteria is FALSE?

a) Bacteria are single-celled.

b) Most bacteria have a rigid cell wall made of cellulose.

c) Bacteria do not contain a true nucleus, that is, they are prokaryotes.

d) Bacteria multiply by binary fission.

e) Many bacteria have flagella for movement.

Correct Answer: b) Most have a rigid cell wall made of cellulose. Rigid cell walls made of cellulose are found in PLANTS not animals. Bacterial cell walls are made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids.

22. Resistance to Bacteria : Microbiology MCQ

Bacteria can acquire resistance to antibiotics by which of the following routes?

a) Transformation

b) Simple mutation

c) Conjugation

d) Plasmid mobilization

e) All of the above

Correct Answer: e. All of the above. A common misconception is that a person can become resistant to certain antibiotics. It is a strain of microorganism that can become resistant, not a person's body. The four main mechanisms by which microorganisms exhibit resistance to antimicrobials are:

1. Drug inactivation or modification: for example, enzymatic deactivation of penicillin G in some penicillin-resistant bacteria through the production of β-lactamases.

2. Alteration of target site: for example, alteration of PBP—the binding target site of penicillins—in MRSA and other penicillin-resistant bacteria

3. Alteration of metabolic pathway: for example, some sulfonamide-resistant bacteria do not require para-aminobenzoic acid (PABA), an important precursor for the synthesis of folic acid and nucleic acids in bacteria inhibited by sulfonamides, instead, like mammalian cells, they turn to using preformed folic acid.

4. Reduced drug accumulation: by decreasing drug permeability or increasing active efflux (pumping out) of the drugs across the cell surface.

23. Penicillin : Microbiology MCQ

The scientist who discovered and characterized the first antibiotic (penicillin) was

a) Koch.

b) Pasteur.

c) Lister.

d) Fleming.

e) Griffith.

Correct Answer: d) Fleming.

Sir Alexander Fleming won Nobel prize for discovering penicillin. Lister developed effective methods to prevent surgical wounds from becoming infected. Pasteur developed pasteurization to destroy unwanted organisms and worked on disproving the theory of spontaneous generation. Griffith discovered genetic transformation in bacteria. Koch worked on anthrax and tuberculosis. None of them work on antibiotics.

24. Facultative Anaerobe : Microbiology MCQ

A bacterium that grows better in the presence of oxygen when it is available, but can also grow if oxygen is absent, is called

a) microaerophilic.

b) aerobic.

c) an aerotolerant anaerobe.

d) a facultative anaerobe.

e) None

Correct answer: d) A facultative anaerobe. Aerobic microorganisms require oxygen for metabolism. An obligate aerobe, by contrast, cannot make ATP in the absence of oxygen, and obligate anaerobes die in the presence of oxygen. Some examples of facultatively anaerobic bacteria are Staphylococcus spp., Streptococcus spp., Escherichia coli.

25. Water Filter : Microbiology MCQ

The water filter is only able to filter out organisms larger than 1 micron. From which of the following organisms would it most likely protect people?

a) All bacteria and protozoa.

b) Almost all viruses and fungi.

c) All viruses and bacteria.

d) Some bacteria and almost all protozoa.

e) Only viruses.

Correct Answer: d) Some bacteria and almost all protozoa. All viruses are small enough to pass through the filter.

26. Which bacteria is Gram-negative aerobic rods?

a) Haemophilus influenzae

b) Neisseria gonorrhoeae

c) Pseudomonas aeruginosa

d) Streptococcus pyogenes

e) Treponema pallidum

Correct Answer: c) Pseudomonas aeruginosa. Gram-negative aerobic rods are rare, with the exception of Pseudomonas.

Haemophilus is a genus of Gram-negative, pleomorphic, coccobacilli bacteria. Neisseria is a genus of Gram-negative diplococcus. Streptococcus is a genus of spherical Gram-positive bacteria. Treponema is a genus of Gram-negative spirochaetes.

27. Urethritis : Microbiology MCQ

The most common cause of non-gonococcal urethritis is

a) Trichomonas vaginalis

b) Chlamydia trachomatis

c) Ureaplasma urealyticum

d) Escherichia Coli

e) Staph Aureus

Correct Answer: b) Chlamydia trachomatis. The most common bacterial cause of non-gonococcal urethritis (NGU) is Chlamydia trachomatis, but it can also be caused by Ureaplasma urealyticum, Haemophilus vaginalis, and Mycoplasma genitalium. Chlamydia is responsible for nearly half of all male cases. In women, about 4 in 10 cases of NGU may be caused by chlamydia.

28. Probiotics : Microbiology MCQ

The W.H.O. definition of probiotics is; live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host. They exhibit all BUT the following characteristics....

a) Nontoxic and nonpathogenic to host

b) Have beneficial effect on host

c) Mimic antibiotics

d) Remain viable for a long time

e) Withstand acidic nature of host’s stomach

Correct Answer: c) Probiotics do not mimic antibiotics. Yogurt is the best food source. Make sure it says live culture, live bacteria, or probiotic on the label because not all yogurts are probiotic. In essence, the live culture or bacteria makes the yogurt probiotic. For this reason, it's important to select cultured dairy products that indicate "contains live cultures" or "contains active cultures" on the packaging.

29. Microorganism : Microbiology MCQ

Majority of the microorganisms associated with the human body

a) Protozoa

b) Bacteria

c) Fungi

d) Viruses

e) Parasites

Correct Answer: b) Bacteria. The human microbiome include bacteria, fungi, and archaea. Under normal circumstances they do not cause disease, but instead participate in maintaining health, are deemed members of the normal flora. It is estimated that 500 to 1,000 species of bacteria live in the human gut. The mass of microorganisms are estimated to account for 1-3% total body mass. Though members of the flora are found on all surfaces exposed to the environment (on the skin and eyes, in the mouth, nose, small intestine), the vast majority of bacteria live in the large intestine.

30. Canning : Microbiology MCQ

Which of the following is FALSE concerning the commercial canning process?

a) It uses pressurized steam.

b) It uses a retort.

c) It tries to kill Clostridium botulinum spores.

d) It kills all spores.

e) Cans are heated and the air is exhausted from the can.

Correct Answer: d) It kills all spores. Spores are very heat resistant.

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