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Module 4: Microbiology: Practice Questions

1. (M1) A 71-year-old man has had pain in his mouth for the past 10 days. On examination there is pharyngeal swelling, erythema, and exudate. Which of the following preanalytical variables is most likely to complicate identification of the causative organisms?

A. Low concentration of organisms

B. Presence of normal microflora

C. Sample collection technique

D. Specimen transport

E. Timing of sample collection

2. (M3) A respiratory culture is obtained, but an unusual organism, Rhodococcus equi, is suspected as the causative organism. Which of the following components of laboratory testing is most likely to be impact the receipt of results by the ordering physician?

A. Preanalytical

B. Analytical

C. Postanalytical

3. (M4) A 33-year-old woman has had low-grade fever with night sweats and productive cough for the past month. Her chest x-ray shows upper lobe granulomatous disease. A positive result for which of the following is the best evidence for use of immediate antimicrobial therapy and patient isolation?

A. C-reactive protein

B. HIV test

C. Interferon gamma release assay

D. Sputum with acid fast bacilli

E. Tuberculin skin test

4. (M5) A 24-year-old health care worker incurs a needlestick injury while performing phlebotomy. A blood sample is drawn on this worker within a day following the injury, and the following test results are obtained on that sample:


Hepatitis A, IgMnegative
Hepatitis A, IgGpositive
Hepatitis B, core antibodynegative
Hepatitis B, surface antigenpositive
Hepatitis B, surface antibodynegative
Hepatitis C antigennegative

What is the most likely interpretation of these findings?

A. Hepatitis A acute infection

B. Hepatitis B, carrier status

C. Hepatitis B, needlestick exposure

D. Hepatitis B, prior vaccination

E. Hepatitis C, chronic infection

5. (M6) A 33-year-old man has acute infective endocarditis with blood culture positive for Streptococcus, viridans group. He is given an antibiotic regimen that includes gentamicin. A test is performed for the minimum inhibitory dilution (MID) for gentamicin based upon patient serum dilutions for both peak and trough antibiotic concentrations. The findings are shown (0 at the right is the control, with no antibiotic):



What is the MID that best predicts good antibiotic effectiveness?

A. 1:2

B. 1:4

C. 1:8

D. 1:16

E. 1:32

F. 1:64

G. 1:128

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