1. Which one of the following general methods is unlikely to be used as a laboratory test to identify an infectious agent?
A. Culture of the organism
B. Nucleic acid amplification for selected pathogens
C. Susceptibility testing of organisms to different antibiotics
D. Karyotyping of isolated organisms that are pathogenic
The correct answer is D. Karyotyping of chromosomes is not a diagnostic test for infections. All of the other methods are mainstays in the evaluation for an infectious disease.
2. Susceptibility tests are most widely used for which of the following types of organisms?
The correct answer is A. Susceptibility testing for the other types of microorganisms is far less common, if they are performed at all.
3. Which of the following organisms is most likely to be an incidental contaminant of the specimen because of its presence within the normal bacterial flora of the skin?
C. Coagulase-negative staphylococci
The correct answer is C. The result is especially likely to represent a skin contaminant introduced during specimen collection if the coagulase-negative staphylococci are present in only one of multiple blood culture specimens.
4. Which of the following is not normally sterile?
The correct answer is D. All of the other choices are sterile. The sputum is often contaminated from the upper respiratory tract with many other organisms, such as viridans group streptococci.
5. Which of the bacteria listed below is an obligate intracellular bacterium and, as a result, cannot be detected by routine bacterial culture?
The correct answer is C. Rickettsia, Ehrlichia, and Anaplasma are all obligate intracellular bacteria. Candida and Cryptococcus are yeasts and not intracellular. Pseudomonas is a bacterium, but it is not intracellular.