Which structure protects bacteria from phagocytosis?

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microbiology chapter 13 test bank Questions

Question 1 of 9

Which structure protects bacteria from phagocytosis?

Correct Answer: B

Rationale: The correct answer is B: Capsule. Capsules are a protective layer outside the bacterial cell wall that helps bacteria evade phagocytosis by immune cells. The capsule inhibits phagocytic cells from engulfing the bacteria, making it difficult for them to be recognized and destroyed. A: Flagella - Flagella are not involved in protecting bacteria from phagocytosis. They are responsible for bacterial movement. C: Endospore - Endospores are dormant, resistant structures formed by some bacteria in response to harsh conditions. They do not directly protect against phagocytosis. D: Pili - Pili are hair-like structures used for adhesion and conjugation, not for protection against phagocytosis.

Question 2 of 9

During the skill-building session in microbiology the students need to stain the prepared and fixed sputum smears obtained from a tuberculosis patient. What staining technique should be used in this case?

Correct Answer: C

Rationale: The correct staining technique for staining sputum smears from a tuberculosis patient is Ziehl-Neelsen staining. This technique uses a carbol fuchsin stain that specifically stains acid-fast organisms like Mycobacterium tuberculosis. The steps involved include staining with carbol fuchsin, decolorizing with acid-alcohol, counterstaining with methylene blue, and then examining under a microscope. This staining method is crucial for detecting the acid-fast bacilli characteristic of tuberculosis. Explanation for incorrect choices: A: Gram staining is used to differentiate bacteria into Gram-positive and Gram-negative, not suitable for acid-fast organisms like Mycobacterium tuberculosis. B: Giemsa staining is used for detecting parasites and certain types of white blood cells, not specific for acid-fast bacteria. D: Burry staining is not a recognized staining technique in microbiology for staining acid-fast organisms.

Question 3 of 9

Malaria is caused by a:

Correct Answer: D

Rationale: The correct answer is D: protozoan. Malaria is caused by Plasmodium parasites transmitted through the bite of infected female Anopheles mosquitoes. These parasites belong to the protozoa kingdom, not viruses (choice A), bacteria (choice B), or helminths (choice C). Protozoa have complex life cycles involving both mosquito and human hosts, leading to the development of malaria in humans. Other choices are incorrect as they do not align with the known etiology and characteristics of malaria.

Question 4 of 9

What is the best therapeutic plan for treating actinomycosis?

Correct Answer: D

Rationale: The correct answer is D, chemotherapy combined with surgical therapy. Actinomycosis is a bacterial infection that requires a combination of antibiotics to target the bacteria and surgery to remove abscesses or infected tissues. Antibiotics alone may not penetrate abscesses effectively. Waiting for self-clearance can lead to complications. Surgical treatment alone may not eradicate the infection entirely. Therefore, the most effective therapeutic plan is to combine chemotherapy to treat the infection systemically and surgery to remove localized infections.

Question 5 of 9

From a medicinal herb a certain phytopathogenic microorganism was secured. In the nutrient medium it forms "fried egg"colonies. What is the most likely agent?

Correct Answer: C

Rationale: Step 1: "Fried egg" colonies typically refer to colonies with a raised center and flattened periphery, resembling the appearance of a fried egg. Step 2: Actinomycetes are filamentous bacteria known to form "fried egg" colonies in nutrient medium. Step 3: Actinomycetes are commonly found in soil and are known to be phytopathogenic microorganisms. Step 4: Actinomycetes produce secondary metabolites with medicinal properties, making them a likely agent from a medicinal herb. Overall, the correct answer is C (Actinomycetes) as they fit the description provided in the question and are commonly associated with the given scenario. The other choices are incorrect as they do not exhibit the specific characteristics mentioned in the question or are not typically associated with forming "fried egg" colonies in nutrient medium.

Question 6 of 9

Bacteriological laboratory examines canned meat whether it contains botulinum toxin. For this purpose an extract of test specimen and antitoxic antibotulinic serum of A, B, E types were introduced to a group of mice under examination; a control group of mice got the extract without antibotulinic serum. What serological reaction was applied?

Correct Answer: A

Rationale: The correct answer is A: Neutralization. In this scenario, the antibotulinic serum of types A, B, and E were introduced to neutralize the botulinum toxin in the test specimen. The serological reaction applied here involves the neutralization of the toxin by the specific antibodies present in the serum. This process prevents the toxin from causing harm to the mice. Summary of other choices: B: Precipitation - This involves the formation of insoluble complexes between antigen and antibody, not the specific neutralization seen in this case. C: Complement binding - This involves activation of the complement system leading to cell lysis, not the direct neutralization of toxin. D: Double immune diffusion - This technique is used to determine the presence of specific antibodies or antigens based on their diffusion patterns, not the neutralization of toxin as seen in this scenario.

Question 7 of 9

The flagellar antigen of the bacteria is known as:

Correct Answer: B

Rationale: The correct answer is B: H antigen. Flagellar antigen is typically referred to as the H antigen in bacteria. Flagella are the whip-like structures used for movement in bacteria, and the H antigen is specifically associated with the flagella. The other choices (A: D antigen, C: K antigen, D: F antigen) are not related to flagella in bacteria and are commonly associated with other types of antigens in bacterial classification.

Question 8 of 9

A child is ill with diphtheria. A smear of the affected mucous membrane revealed blue rods with thickenings at the poles. What staining method was used?

Correct Answer: A

Rationale: The correct answer is A: Neisser staining method. Neisser staining method is used to stain diphtheria bacilli, which appear as blue rods with thickenings at the poles. The rationale is that Neisser staining specifically targets and highlights the characteristics of the diphtheria bacilli. Incorrect choices: B: Gram staining is not specific for diphtheria bacilli and does not show the characteristic blue rods with thickenings at the poles. C: Ziehl-Neelsen staining is used for acid-fast bacteria like Mycobacterium tuberculosis, not for diphtheria bacilli. D: Loeffler staining is used for diphtheria bacilli but does not produce blue rods with thickenings at the poles as seen in this case.

Question 9 of 9

The correct descending order of taxonomic categories is

Correct Answer: C

Rationale: The correct descending order of taxonomic categories is domain, kingdom, phylum, class, order, family, genus, species. This hierarchical classification system helps organize and categorize living organisms based on their shared characteristics and evolutionary relationships. Explanation: - Domain is the broadest category, representing the highest level of classification. - Kingdom further divides organisms into major groups based on similar characteristics. - Phylum, class, order, family, and genus successively narrow down the classification based on more specific shared characteristics. - Species is the most specific category, representing individual organisms capable of interbreeding. Summary of other choices: A: Incorrect as it has the incorrect order of phylum, kingdom, and division. B: Incorrect as it has the incorrect order of family and species. D: Incorrect as it has the incorrect order of domain, kingdom, and class.

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