Question 1

Non-acid-fast aerobic actinomycetes include:

Accepted Answer

Streptomyces, Actinomadura, Dermatophilus, Nocardiopsis, and the thermophilic Actinomycetes are gram-positive, branching filaments that do not have mycolic acids present in their cell envelopes and are therefore non-acid-fast.

Question 2

Which partially acid-fast, gram-positive, and branching filamentous bacteria appear dry and white to creamy to orange with rhizoid edges on routine agar and are urea-positive and resistant to lysozyme?

Accepted Answer

Tsukamurella is a partially acid-fast, gram-positive, and branching filamentous bacterium that appears dry and white to creamy to orange with rhizoid edges on routine agar and is urea-positive and resistant to lysozyme.The other three organisms listed are lysozyme-sensitive.

Question 3

Partially acid-fast aerobic actinomycetes include:

Accepted Answer

The genera Nocardia, Rhodococcus, Gordonia, and Tsukamurella are all partially acid-fast aerobic actinomycetes.

Question 4

Nocardia spp.form branched filaments that extend into the air that are called _____ hyphae.

Accepted Answer

Nocardia spp.form branched filaments that extend into the air and are referred to as aerial hyphae.

Question 5

The organism that has been most commonly associated with human disease, particularly in patients who are immunocompromised, such as those infected with human immunodeficiency virus (HIV), is:

Accepted Answer

Rhodococcus equi has been the organism most commonly associated with human disease, particularly in patients who are immunocompromised, such as those infected with HIV.R.equi is a facultative intracellular organism that can persist and replicate within macrophages.Determinants of virulence of R.equi are under investigation and may involve cell wall mycolic acids that play a role in intracellular survival, production of interleukin 4, and granuloma formation.

Question 6

A chronic, granulomatous infection of subcutaneous tissues, which is caused by aerobic actinomycetes resulting in tissue swelling and draining sinus tracts, is referred to as:

Accepted Answer

Infection caused by most non-acid-fast aerobic actinomycetes is usually chronic, granulomatous lesions of the skin referred to as mycetoma.Mycetoma is an infection of subcutaneous tissues, resulting in tissue swelling and draining sinus tracts.These infections are acquired by traumatic inoculation of organisms (usually in the lower limbs)and are usually caused by fungi.If a mycetoma is caused by an actinomycete, the infection is then called actinomycetoma.

Question 7

The group of bacteria that can be described as being normal inhabitants of soil and water and primarily responsible for the decomposition of plant material is:

Accepted Answer

Nocardia are normal inhabitants of soil and water and are primarily responsible for the decomposition of plant material.Infections caused by Nocardia spp.are found worldwide.Because they are ubiquitous, the isolation of these organisms from clinical specimens does not always indicate infection.

Question 8

Nocardia spp.cause which of the following types of infections in individuals who are immunocompromised?

Accepted Answer

Nocardia spp.cause three types of skin infections in individuals who are immunocompromised: (1)mycetoma, which is a chronic, localized, painless, subcutaneous infection; (2)lymphocutaneous infections; and (3)skin abscesses or cellulites.In individuals who are immunocompromised, Nocardia spp.can cause invasive pulmonary infections and disseminated infections.

Question 9

Nocardia spp.form branched filaments that extend along the agar surface, which are called _____ hyphae.

Accepted Answer

Nocardia spp.form branched filaments that extend along the agar surface and are referred to as substrate hyphae.

Question 10

Which organisms should be used to run quality control for acid-fast stains?

Accepted Answer

The only organisms that are partially acid-fast positive and acid-fast negative are Nocardia and Streptomyces, respectively.All other combinations are either both acid-fast positive (Nocardia and Rhodococcus)or both acid-fast negative (Streptomyces and Actinomadura; Dermatophilus and Nocardiopsis).

Quiz 18: Nocardia Streptomyces Rhodococcus and Similar Organisms