2. Bacillus anthracis and Bacillus cereus can best be differentiated by which tests?

3. Which is the specimen of choice for proof of food poisoning by B. cereus?

4. A suspected B. anthracis culture obtained from a wound specimen produced colonies that had many outgrowths (Medusa-head appearance), but were not β-hemolytic on sheep blood agar. Which test should be performed next?

5. Which of the following tests should be performed for initial differentiation of L. monocytogenes from group B streptococci?

6. Culture of a finger wound specimen from a meat packer produced short gram-positive, non–spore-forming bacilli on a blood agar plate showing no hemolysis. Given the following test results at 48 hours, what is the most likely identification?

7. Nonspore-forming, slender, gram-positive, rod-forming palisades and chains were recovered from a vaginal culture and grew well on tomato juice agar. The most likely identification is:

8. A Corynebacterium species recovered from a throat culture is considered a pathogen when it produces:

9. A presumptive diagnosis of Gardnerella vaginalis can be made using which of the following findings?

10. A gram-positive branching filamentous organism recovered from a sputum specimen was found to be positive with a modified acid-fast stain method. What is the most likely presumptive identification?

11. Routine laboratory testing for Treponema pallidum involves:

12. Spirochetes often detected in the hematology laboratory while scanning a blood film, even before the physician suspects the infection, are:

13. Which of the following organisms is the cause of Lyme disease?

14. The diagnostic method most commonly used for the identification of Lyme disease is:

15. Primary atypical pneumonia is caused by:

16. Which organism typically produces “fried egg” colonies on agar within 1 to 5 days of culture obtained from a genital specimen?

17. The manganous chloride–urea test is used for the identification of which organism?

18. A gram-positive (gram-variable), beaded organism with delicate branching was recovered from the sputum of a 20-year-old patient with leukemia. The specimen produced orange, glabrous, waxy colonies on Middlebrook agar that showed partial acid-fast staining with the modified Kinyoun stain. What is the most likely identification?

19. A direct smear from a nasopharyngeal swab stained with Loeffler methylene blue stain showed various letter shapes and deep blue, metachromatic granules. The most likely identification is:

20. Which of the following is the best, rapid, nonculture test to perform when G. vaginalis is suspected in a patient with vaginosis?

21. Which is the test of choice for the confirmation of Chlamydia trachomatis infection in urine?

22. Which test is the most reliable for the detection of M. pneumonia in serum and for the confirmation of diagnosis?

23. Identify the following bacterium–specimen pairing that is mismatched (specimen not appropriate for isolation):

24. Which of the following organisms are transmitted to animals and humans after a tick bite?

25. Following a hike in the woods, a young male noted a tick on his ankle. He removed the tick, but 2 weeks later, he noticed a circular, “bull’s eye” rash at the site of the bite. Which specimen(s) should be obtained to establish a diagnosis of Lyme borreliosis?

26. Partially acid-fast, gram-positive, filamentous-branching bacteria that fragmented into rods and cocci were seen in a sputum sample from a patient with HIV infection. Which of the following is the most likely presumptive identification?

27. An asymptomatic 25-year-old female patient with persistent nongonococcal urethritis (NGC) and pelvic inflammatory disease (PID) was suspected of being infected with Mycoplasma genitalium. Which category of testing should not be utilized to establish a final identification?

1. Obligate anaerobes, facultative anaerobes, and microaerophiles are terms referring to bacteria that require:

2. Which of the following most affects the oxidation–reduction potential (Eh, or redox potential) of media for anaerobic bacteria?

3. Which of the following is the medium of choice for the selective recovery of gramnegative anaerobes?

4. Anaerobic bacteria are routinely isolated from all of the following types of infections except:

5. Methods other than packaged microsystems used to identify anaerobes include:

6. Which broth is used for the cultivation of anaerobic bacteria to detect volatile fatty acids as an aid to identification?

7. A gram-positive spore-forming bacillus growing on sheep blood agar anaerobically produces a double zone of β-hemolysis and is positive for lecithinase. What is the presumptive identification?

8. Egg yolk agar is used to detect which enzyme produced by several Clostridium species?

9. Which of the following organisms will display lipase activity on egg yolk agar?

10. Which spore type and location is found on Clostridium tetani?

11. Gram-positive bacilli recovered from two blood cultures from a 60-year-old patient with diabetes gave the following results: Spores seen = Neg Hemolysis = + (double zone) Motility = Neg Lecithinase = + Volatile acids by GLC (PYG) = acetic acid (A) and butyric acid (B) What is the most likely identification?

12. Which mechanism is responsible for botulism in infants caused by C. botulinum?

13. The classic form of foodborne botulism is characterized by the ingestion of:

14. Which test is performed to confirm an infection with C. botulinum?

15. Which Clostridium spp. causes pseudomembranous colitis or antibiotic-associated colitis?

16. Identification of C. tetani is usually based on:

17. Obligate anaerobic gram-negative bacilli that do not form spores, grow well in 20% bile (Bacteroides bile esculin [BBE] agar), and are resistant to penicillin two-unit disks are most likely:

18. Which Bacteroides spp. is noted for “pitting” of the agar and is sensitive to penicillin two-unit disks?

19. Which gram-negative bacilli produce brown to black pigment on KVA agar and brick red fluorescence when exposed to an ultraviolet (UV) light source?

20. The following characteristics of an obligate anaerobic gram-negative bacilli best describe which of the listed genera? Gram staining = Long, slender rods with pointed ends Colonial appearance = Dry bread crumbs or “fried-egg” appearance Penicillin two-unit disk test = Susceptible

21. All of the following genera are anaerobic cocci that stain gram positive except:

22. The gram-positive non–spore-forming, anaerobic, short, pleomorphic rods most frequently recovered from blood cultures as a contaminant are:

23. Which Clostridium species is most often recovered from a wound infection with gas gangrene?

24. Gram staining of a smear taken from the periodontal pockets of a 30-year-old man with poor dental hygiene showed sulfur granules containing gram-positive rods (short diphtheroids and some unbranched filaments) and were non–acid fast. Colonies on blood agar resembled “molar teeth” in formation. The most likely organism is:

25. Antimicrobial susceptibility testing of Bacteroides and Clostridium spp. anaerobes are done by which of the following methods?

26. An abdominal postoperative wound specimen grew catalase-positive, indole-negative, nonpigmented, nonfluorescent, gram-negative, pleomorphic bacilli (safety pin–shaped) on 20% bile media. The colonies also grew on KVA agar (resistant to kanamycin, vancomycin, and colistin). What is the most likely identification?

1. The best specimen for recovery of the mycobacteria from a sputum sample is the:

2. What concentration of sodium hydroxide (NaOH) is used to prepare a working decontamination solution for the processing of not normally sterile specimens for mycobacteria?

3. Which is the most appropriate nonselective medium for recovery of mycobacteria from a heavily contaminated specimen?

4. Mycobacteria stained by using the Ziehl-Neelsen or Kinyoun methods with methylene blue counterstain are seen microscopically as:

5. Acid-fast staining of a smear prepared from digested sputum showed slender, slightly curved, beaded, red mycobacterial rods. Growth on the Middlebrook 7H10 medium slants produced buff-colored microcolonies with a serpentine pattern after 14 days at 37°C. Niacin and nitrate reduction test results were positive. What is the most probable presumptive identification?

6. Which organism, associated with tuberculosis in cattle, causes tuberculosis in humans, especially in regions where dairy farming is prevalent?

7. Which of the following organisms are used as controls for rapid growers and slow growers, respectively?

8. Which of the following Mycobacterium spp. produce(s) pigmented colonies in the dark (is a scotochromogen)?

9. All of the following mycobacteria are associated with skin infections except:

10. All of the following Mycobacterium spp. produce the enzyme required to convert niacin to niacin ribonucleotide except:

11. The catalase test for mycobacteria differs from that used for other types of bacteria by using:

12. Growth inhibition by thiophene-2-carboxylic hydrazide (T2H) is used to differentiate M. tuberculosis from which other Mycobacterium species?

13. Which of the following Mycobacterium spp. is best differentiated by the rapid hydrolysis of Tween 80?

14. Mycobacteria isolated from the hot water system of a hospital grew at 42°C. Colonies on the Löwenstein-Jensen medium were not pigmented after exposure to light and were negative for niacin accumulation and nitrate reduction. The most likely identification is:

15. A Mycobacterium species recovered from a patient with AIDS gave the following results: What is the most likely identification?

16. The urease test is needed to differentiate M. scrofulaceum from which of the following mycobacteria?

17. A laboratory provides the following services for identification of mycobacteria: Acidfast staining of clinical specimens Inoculation of cultures Shipment of positive cultures to a reference laboratory for identification According to the ATS’s definition for levels of service this laboratory is:

18. According to the College of American Pathologists (CAP) guidelines, which services for mycobacteria would be performed by a Level II laboratory?

19. Culture of a skin (hand) wound from a manager of a tropical fish store grew on Löwenstein-Jensen agar slants at 30°C in 10 days but did not grow on the same media at 37°C in 20 days. Given the following results, what is the most likely identification?

20. Which nonpathogenic Mycobacterium species is isolated most often from clinical specimens and is called the “tapwater bacillus”?

21. Which of the following drugs are first-line antibiotics used to treat classic tuberculosis for which susceptibility testing is performed by the disk diffusion method on Middlebrook 7H10 or 7H11 agar plates?

22. How long should M. tuberculosis–positive cultures be kept by the laboratory after identification and antibiotic susceptibility testing have been performed?

23. According to the reporting standards of the ATS, one or more acid-fast bacilli (AFB) per oil immersion field (1,000×) are reported as:

24. Which of the following rapid-growing Mycobacterium spp. would most likely grow on a MacConkey agar plate and on other routine bacteriologic media?

25. Rapid methods for identifying classic infection with M. tuberculosis include:

26. Individuals showing a positive purified protein derivative (PPD) skin test for M. tuberculosis are usually:

27. Which of the following Mycobacterium species is diagnosed by means other than culture?

28. Which M. avium complex organism is the most frequently isolated mycobacterium from patients with AIDS?

29. Which mycobacterium of the M. tuberculosis complex fails to grow in culture and has a characteristic “croissant-like” morphology in stained smears?

30. Which two mycobacteria commonly isolated from subcutaneous skin have an optimal growth temperature of 30°C?

31. Which mycobacterium is associated with Crohn disease?

32. Which temperature range is ideal for the recovery of M. marinum?

33. Key biochemical tests used to identify M. tuberculosis are:

34. What report should be given for the results of the following AFB smear? Number of AFB seen = 2 per 300 fields (1,000× magnification)

35. What vaccine against tuberculosis is available, and what is the source of the vaccine?