Question 1

The tuberculin skin test looks to identify ________ specific to Mycobacterium tuberculosis.

Accepted Answer

The tuberculin skin test identifies delayed hypersensitive (DTH) TH1 cells specific to Mycobacterium tuberculosis. These cells are part of the immune response that reacts to the antigens of the bacteria, indicating a previous or current infection.

Question 2

Most drug-resistant bacteria isolated from patients contain a(n)

Accepted Answer

R plasmids are mobile genetic elements that carry genes coding for antibiotic resistance. They are often responsible for the spread of resistance among bacterial populations. Therefore, most drug-resistant bacteria isolated from patients are expected to contain R plasmids. T1 phages are bacteriophages that infect E. coli, but they are not related to antibiotic resistance. Reverse transcriptase is an enzyme that converts RNA into DNA, and it is not directly involved in antibiotic resistance. β-lactam antibiotics are a type of antibiotic that inhibit bacterial cell wall synthesis, but they are not a feature of drug-resistant bacteria itself.

Question 3

Two common or important bacterial pathogens found in the blood are

Accepted Answer

Pseudomonas aeruginosa and Escherichia coli are both common bacterial pathogens that can be found in the blood. Pseudomonas aeruginosa is often associated with infections in immunocompromised individuals, while Escherichia coli can cause urinary tract infections, sepsis, and meningitis.

Question 4

Compared with other precipitation tests, agglutination tests are

Accepted Answer

Agglutination tests are more sensitive than precipitation tests because they can detect smaller amounts of antigen or antibody.

Question 5

Which of the following prevents supercoiling of bacterial DNA?

Accepted Answer

Quinolones such as ciprofloxacin and levofloxacin target DNA gyrase, which is necessary for bacterial DNA replication and prevents supercoiling of DNA. Macrolides (A), penicillins (C), and cephalosporins (D) target different components of bacterial cells and do not directly affect DNA supercoiling.

Question 6

Which of the following is a novel antimicrobial target?

Accepted Answer

Disruption of lipid biosynthesis is a novel antimicrobial target because it is not typically targeted by traditional antibiotics and could potentially avoid the issue of antibiotic resistance.

Question 7

In the United States, every clinical and research institution requires that workers be protected from ________, a pathogen that is contracted almost exclusively from handling patient specimens (rather than from known exposure or accidents).

Accepted Answer

Hepatitis B is a bloodborne pathogen that can be contracted from handling patient specimens. Therefore, all clinical and research institutions require workers to be protected from it. Options A, C, and D are also important infectious agents, but they may have different modes of transmission or risks associated with them.

Question 8

A gram-negative, oxidase-positive diplococcus growing on chocolate agar likely belongs to the genus

Accepted Answer

Neisseria species are gram-negative, oxidase-positive diplococci that grow well on chocolate agar. Escherichia is a gram-negative rod, while Mycobacterium is an acid-fast bacillus and Pseudomonas is a gram-negative rod that does not typically grow well on chocolate agar.

Question 9

Blood agar is an example of amedium that supports the growth of many microbes. Medium that supports a wide variety of growth is called ________ medium.

Accepted Answer

A general-purpose medium can support the growth of a wide variety of microbes, including both fastidious and non-fastidious organisms. Blood agar is an example of a general-purpose medium. Selective medium contains components that inhibit the growth of certain microbes while allowing the growth of others, while stable medium refers to a medium that does not change its composition over time. Halophilic medium is specific to organisms that require a high concentration of salt for growth.

Question 10

The basis for blood typing is referred to as

Accepted Answer

Hemagglutination is the basis for blood typing. This technique involves mixing a person's blood with antibodies against blood group antigens. If the antigen is present, the blood cells will clump or agglutinate, indicating a positive reaction. This reaction is used to determine a person's blood type. Neutralization, immunodiffusion, and precipitation are other immunoassay techniques but are not used for blood typing.

Question 11

Protein A, commonly used in immunoblots, is derived from

Accepted Answer

Protein A is derived from Staphylococcus aureus and is commonly used in immunoblots to detect and purify antibodies. It binds specifically to the Fc region of many mammalian IgG antibodies, making it a useful tool in protein purification and detection processes.

Question 12

Blood infections are most commonly caused by Enterococcus and ________, among many other genera.

Accepted Answer

Staphylococcus is a common cause of blood infections, along with other genera, including Enterococcus, Escherichia coli, and Coryneform bacteria. Propionibacteria are not commonly associated with blood infections.

Question 13

Eukaryotic intestinal parasites, such as Giardia, can be identified by observing stool samples for the presence of

Accepted Answer

Eukaryotic intestinal parasites like Giardia exist as cysts in the host's stool samples. Identification of these cysts can help diagnose the infection. Antibodies, LPS, and blood may not necessarily be present in stool samples of individuals with Giardia infection.

Question 14

Which bacterium shows a characteristic metallic green sheen when grown on eosin-methylene blue (EMB) agar?

Accepted Answer

Escherichia coli shows a metallic green sheen when grown on eosin-methylene blue (EMB) agar. This is due to the presence of a surface protein called Colicin V, which causes the metallic green color. Salmonella enterica may also grow on EMB agar, but it does not produce a metallic sheen. Staphylococcus aureus and Streptococcus pyogenes do not grow on EMB agar.

Question 15

A laboratory in which Ebola virus is studied would be classified as a BSL-________ laboratory.

Accepted Answer

Ebola virus is a highly contagious and deadly virus, and therefore would require the highest level of biosafety precautions. BSL-4 laboratories are designed to handle the most dangerous and exotic pathogens, and would be appropriate for studying Ebola virus.

Question 16

________ defines the lowest quantity of an antigen that can be detected in a serological test.

Accepted Answer

Sensitivity is a term used to define the lowest quantity of an antigen that can be detected in a serological test.

Question 17

Which of the following is a cause of drug-specific resistance in disease-causing organisms?

Accepted Answer

The indiscriminate nonmedical use of antimicrobials can lead to the development of drug-specific resistance in disease-causing organisms. This occurs when the overuse or misuse of antibiotics selectively pressures bacteria to develop resistance to one or more particular antibiotics, making them less effective as a treatment option.

Question 18

EMB agar is an example of a ________ medium.

Accepted Answer

EMB agar is both selective and differential. It contains dyes and other inhibitors that selectively inhibit the growth of gram-positive bacteria, while the differential aspect lies in its ability to distinguish between lactose-fermenting and non-lactose fermenting bacteria, based on the color that colonies produce when grown on the medium.

Question 19

________, periodic reports on the susceptibility of clinically isolated organisms to the antibiotics in current local use, are particularly valuable for tracking the emergence of new antibiotic-resistant strains of pathogens.

Accepted Answer

Antibiograms are specifically designed to display the susceptibility of clinically isolated organisms to the antibiotics in current local use. The other options listed are not designed for this purpose.

Question 20

Antibody titer can be measured by

Accepted Answer

Antibody titer can be measured by agglutination, which involves the clumping together of bacterial cells or particles when mixed with antibodies specific for the target antigen. The degree of clumping can be used to determine the concentration of antibodies in a patient's blood serum.

Quiz 28: Clinical Microbiology and Immunology