Micro Practice Exam

When collecting material from wounds or abscesses, the preferred method is:

• swabbing the outer skin

• collecting dried exudate

• aspirating from the advancing line of infection

• wiping with alcohol first

Which anticoagulant is most commonly used in blood culture bottles?

• EDTA

• heparin

• sodium polyanethol sulfonate (SPS)

• citrate

What is an example of nonselective media?

• Columbia Nalidixic Acid agar

• MacConkey agar

• Chocolate agar

• Sheep blood agar

What is the preferred method for preparing thin fluid specimens?

• two-slide crush technique

• cytocentrifuge preparations

• plate inoculation

• direct staining without preparation

Why do Gram-positive bacteria retain the crystal violet-iodine complex?

• they have a thin peptidoglycan layer

• alcohol strengthens their membrane

• their thick peptidoglycan layer traps the CVI complex

• safranin binds before crystal violet

What type of microscope is primarily used for routine microbiology?

• electron microscope

• dark-field microscope

• bright-field compound microscope

• fluorescent microscope

According to the Murray-Washington method, an acceptable sputum sample contains:

• >25 epithelial cells and <10 PMNs/LPF

• <25 epithelial cells and ≥10 PMNs/LPF

• <10 epithelial cells and no PMNs

• ≥50 epithelial cells and few PMNs

Which medium is selective for gram-positive organisms?

• MacConkey agar

• Blood agar

• Chocolate agar

• Colistin Nalidixic Agar (CNA)

Which type of hemolysis results in complete clearing of red blood cells around a colony?

• alpha

• beta

• gamma

• delta

Answer explanation

alpha- partial

gamma- none

Which organism is associated with swarming growth on agar?

• Streptococcus pneumoniae

• Escherichia coli

• Proteus species

• Staphylococcus aureus