MICROBIOLOGY & IMMUNOLOGY FINAL EXAM ON OCULAR MICROBIOLOGY Dr. William J. Benjamin

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1 MICROBIOLOGY & IMMUNOLOGY FINAL EXAM ON OCULAR MICROBIOLOGY Dr. William J. Benjamin 1:00 pm 3:00 pm, Tuesday, November 11, 2008 in HPB 301 & 303 NAME: Score: / 188 Part A: Select the single most appropriate answer for questions 1 to 63. Each question is worth 2 points. 1. Mycobacteria can be seen by light microscopy as beaded red rods after they have been stained with: A. Gram stain B. Acid-Fast stain C. Wood stain D. Giemsa stain E. Finishing stain 2. A person s eyes came into contact with some cotton dust while working on a farm. He is in your office 3 days after the incident and has developed a keratoconjunctivitis with a macular keratitis on the left eye. You should not prescribe or use the following at this point: A. A topical corticosteroid drop. B. A topical anti-bacterial drop. C. A topical anti-fungal drop. C. An oral anti-bacterial preparation. E. A bandage soft contact lens. 1

2 3. A product that has been recommended for use in cases of Epidemic Keratoconjunctivitis is? A. Steri-Lid Eyelid Cleanser B. Dove Dishwashing Liquid C. Alcon Betadine 5% Ophthalmic Prep Solution D. OcuSoft Lid Scrub Plus E. Johnson & Johnson Baby Shampoo 4. It is best, all other things being equal, to prescribe an ophthalmic antibiotic that has the following characteristic: A. It is well-known as an antibiotic used for respiratory infections. B. It is not used much for infections or conditions elsewhere in the body. C. It has a very high MIC. D. It has a very high MBC. E. It is generally not commercially available in ophthalmic preparations. 5. The standardized agar used to perform disc diffusion susceptibility testing for Haemophilus influenzae, as opposed to most other pathogens, is: A. Mueller-Hinton agar B. Chocolate agar C. Sabouraud's agar with or without an antibacterial D. Mueller-Hinton agar with 5% sheep s blood E. Mueller-Hinton agar with 5% sheep s blood, chocolated 6. The nematode most associated with chorioretinitis lesions of the ocular posterior pole in humans is: A. Candida albicans B. Toxocara canis C. Histoplasma capsulatum D. Aspergillis fumigatus E. Toxoplasma gondii 2

3 7. You prescribed treatment for a farm laborer having a macular keratitis with a topical anti-bacterial drop containing gatifloxacin, a relatively new fluoroquinolone. He had had some hay blown into his eyes 3 days beforehand. Two days after initiation of your treatment the lesion appeared marginally better but the patient s photophobia and eye irritation had only slightly diminished. You should consider that: A. The infecting agent could be a bacterium that is resistant to the anti-bacterial being used. B. The infecting agent could be a mycobacterium that is resistant to the antibacterial being used. C. The infecting agent could be a fungus that is resistant to the anti-bacterial being used. D. The infecting agent could be a parasite that is resistant to the anti-bacterial being used. E. Any of the above could be true. 8. You prescribed treatment for a soft contact lens wearer having a keratoconjunctivitis accompanied by purulence. Wear of contact lenses was discontinued and the patient used tobramycin ophthalmic drops t.i.d. for 2 days. The condition at that time appeared to be resolving and, 5 days later (1 week after the initial visit), the condition looked resolved. You asked the patient to keep on the drops for 3 more days and taper off, then to resume contact lens wear with new lenses, storage cases, and solutions 2 weeks after the original visit. The patient came back at that time (2 weeks after the initial visit) with an angry looking keratoconjunctivitis in the same eye. You should consider that: A. The patient may not have complied with your request by discontinuing the antibacterial drops too early. Resistant strains of the infecting agent had not been eliminated and the infection came back. B. A pathogen came in contact with the eye after the antibacterial drops had been discontinued but before the normal flora were able to re-establish. Another infection formed quickly in this environment. C. The patient may not have complied with your request to restart contact lens wear using new lenses, new cases, and/or new solutions. The eye was infected again by the agent that had caused the original infection. D. The new infection may have no relationship to the previous infection or its treatment. E. Any of the above could be true. 3

4 9. Fungal infections of the eye are associated with: A. Immunocompromised persons. B. Ocular trauma. C. Ocular contamination with vegetable matter. D. Superinfection. E. All of the above have an association with fungal eye infections. 10. The following is the only topical agent known as an antifungal that is commercially available by prescription in an ophthalmic preparation: A. Tobramycin B. Prednisolone C. Amphotericin B D. Natamycin E. Zymar 11. Two bacterial ocular pathogens that apparently have a special affinity for corneal epithelial cells are: A. Pseudomonas aeruginosa and Streptococcus pneumoniae B. Chlamydia trachomatis and Herpes simplex C. Staphylococcus aureus and Corynebacterium diphtheriae D. Serratia marcescens and Streptococcus pyogenes E. Moraxella lacunata and Haemophilis influenzae 12. An intracellular parasite known to cause ocular fundus (chorioretinal) lesions similar to, but generally distinguishable from, those of Histoplasma capsulatum is: A. Toxocara canis B. Toxoplasma gondii C. Acanthamoeba sp. D. Leishmania sp. E. Microsporidia 4

5 13. In the early stages, keratitis caused by Acanthamoeba is often mistaken for keratitis caused by: A. Toxocara canis B. Pseudomonas aeruginosa C. Adenovirus D. Microsporidia E. Herpes-like viruses 14. Cytology of a conjunctival scrape for an eye having signs and symptoms of ocular inflammation is polynuclear, showing only many polymorphonuclear cells. The patient s contact lenses have small deposits with feathered edges, indicative of hyphae. Without consideration of any other signs and symptoms, the most likely diagnosis for this eye is: A. Bacterial infection B. Fungal infection C. Chlamydial infection D. Viral infection E. Protozoan infection 15. Cytology of a conjunctival scrape for an eye having signs and symptoms of ocular inflammation is eosinophilic: you see a few eosinophils. Without consideration of the signs and symptoms, the most likely diagnosis for this eye is: A. Bacterial infection B. Fungal infection C. Chlamydial infection D. Viral infection E. Immunologic/Allergenic inflammation 16. When treating an eye with a topical antibiotic, the patient should nearly always finish the entire amount of drug, either 10 or 14 days depending on the Rx, primarily since: A. To allow the eye to counteract toxic or allergenic side effects of drug. B. To more effectively kill opportunistic organisms not as influenced by the drug. C. To kill off the normal flora in order to aseptisize the affected area. D. To allow more time to kill resistant strains of the pathogenic organism. E. To disrupt the corneal epithelium so as to get more drug into the cornea. 5

6 17. These are pathogenic extracellular protozoans or multi-cellular parasites except: A. Trypanosoma sp. B. Malassezia furfur C. Toxocara canis D. Onchocerca volvulus E. Thelazia sp. 18. Epsilometer susceptibility tests are performed with filter paper strips impregnated with various antibiotic substances on a particular type of agar plate evenly streaked with the bacterium strain to be tested. Which medium is the standard used in most cases? A. Chocolate agar B. Mueller-Hinton agar C. Mueller-Hinton agar with 5% sheep s blood D. Chocolated Mueller-Hinton agar E. Sabouraud's agar with or without antibiotic 19. The standardized agar used to perform disc diffusion susceptibility testing for Streptococcus pneumoniae, as opposed to most other pathogens, is: A. Blood agar B. Mueller-Hinton agar C. Mueller-Hinton agar with 5% sheep s blood D. Chocolate agar or Chocolated Mueller-Hinton agar E. Lowenstein-Jensen agar 20. When treating an eye with a topical antibiotic, the patient should not taper off of the medication but should maintain the indicated dosage until the very end of the treatment period, because: A. To reduce the chances that the pathological organism will develop a resistance to the medication. B. To more effectively kill opportunistic organisms not as influenced by the drug. C. To kill off the normal flora in order to aseptisize the affected area. D. To allow more time to kill resistant strains of the pathogenic organism. E. To disrupt the corneal epithelium so as to get more drug into the cornea. 6

7 21. The form of trauma called antecedent trauma is that which: A. Removes the corneal or conjunctival epithelium as in an abrasion. B. Occurs prior to an infection and is necessary for the infection to occur. C. Occurs as a result of eye surgery. D. Heals improperly causing a raised or elevated corneal area. E. Occurs as a result of topical antibiotic drops. 22. An organism that is ubiquitous: A. Is present only in colonies hidden from direct sunlight. B. Feeds off of sodium fluorescein in solution. C. Increases resistance to the antibiotic being used to kill it. D. Is present all over in nature. E. Remains viable through formation of a spore or cyst. 23. Pseudomembranes or membranes that form over the palpebral conjunctiva are different in that: A. Pseudomembranes can be easily removed from the conjunctival surface but membranes are more attached, such that portions of the surface are removed with them. B. Pseudomembranes are caused by bacteria and membranes by viruses. C. Pseudomembranes are made of a different material than membranes. D. Pseudomembranes are toxic and membranes are allergenic. E. Pseudomembranes respond to anti-bacterial agents and membranes do not. 24. Use of the following topical agent is contraindicated in cases of fungal or suspected fungal keratitis or corneal ulceration: A. Ophthalmic tobramycin drops. B. Natamycin drops. C. A special mixture of Amphotericin B drops. D. Ophthalmic corticosteroid drops. E. Ocular lubricants. 7

8 25. Which of the following organisms is a multi-cellular pathogen of the eye? A. Acanthamoeba sp. B. Toxocara sp. C. Microsporidia sp. D. Chlamydia trachomatis E. Herpes simplex 26. The proportion of asymptomatic adults having a Gram (-) rod as a normal bacterial ocular flora is approximately: A. 0 out of 5 B. 1 out of 5 C. 2 out of 5 D. 3 out of 5 E. 4 out of There are several ocular viral pathogens that are Herpes-like. Which of the following is a Herpes-like virus? A. Chlamydia psittaci B. Adenovirus C. Varicella virus D. Coxsackie virus type A24 E. HIV / AIDS virus 28. The causative agents of Acute Hemhorrhagic Conjunctivitis are: A. Adenovirus types 8 and 19 viruses B. Varicella and Herpes zoster viruses C. Verrucae and Papilloma viruses D. Flu and Common Cold viruses E. Enterovirus type 70 and Coxsackie type A24 viruses 8

9 29. The standardized agar used to perform disc diffusion susceptibility testing for Moraxella lacunata, as opposed to most other pathogens, is: A. Mueller-Hinton agar B. Lowenstein-Jensen agar C. Sabouraud's agar with or without an antibacterial D. Mueller-Hinton agar with 5% sheep s blood E. Mueller-Hinton agar with 5% sheep s blood, chocolated 30. The Gram (+) organism most frequently associated with eyelid margin infections is: A. Pseudomonas aeruginosa B. Proprionibacterium acnes C. Haemophilis influenzae D. Neisseria gonorrhea E. Staphylococcus aureus 31. The Gram (+) organism second-most frequently associated with eyelid margin infections is: A. Pseudomonas aeruginosa B. Proprionibacterium acnes C. Haemophilis influenzae D. Neisseria gonorrhea E. Staphylococcus aureus 32. The Gram (+) organism causing almost all eyelid hordeola is: A. Pseudomonas aeruginosa B. Haemophilis influenzae C. Moraxella lacunata D. Staphylococcus aureus E. Proprionibacterium acnes 9

10 33. The "MBC" of an antibiotic is: A. Maximum concentration of bacteria to have growth visibly inhibited by the antibiotic. B. Maximum concentration of bacteria in which 99.9% are killed by the drug. C. Lowest concentration of antibiotic that kills 99.9% of the bacterial inoculum. D. The medium (agar) of choice, on which the bacteria are susceptible to the antibiotic. E. Lowest concentration of antibiotic that inhibits visible bacterial growth. 34. The "MIC" of an antibiotic is the: A. Maximum concentration of bacteria to have growth visibly inhibited by the antibiotic. B. Maximum concentration of bacteria in which 99.9% are killed by the drug. C. Lowest concentration of antibiotic that kills 99.9% of the bacterial inoculum. D. The medium (agar) of choice, on which the bacteria are susceptible to the antibiotic. E. Lowest concentration of antibiotic that inhibits visible bacterial growth. 35. The diameters of the inhibitory zones around penicillin and gentamicin sensi-discs are 18 mm and 10 mm, respectively. You may properly conclude one of the following: A. The bacterium is more susceptible to penicillin than to gentamicin. B. The bacterium is less susceptible to penicillin than to gentamicin. C. The bacterium is equally susceptible to penicillin and gentamicin. D. The bacterium is not susceptible to either penicillin or gentamicin. E. None of these conclusions are supported by the information available. 36. A weak Beta (β) hemolysis is signified by a(n) halo surrounding a colony on blood agar. A. white B. clear/transluscent C. absence of D. yellow or orange E. light green 10

11 37. A strong Beta (β) hemolysis is signified by a(n) halo surrounding a colony on blood agar. A. white B. clear/transluscent C. absence of D. yellow or orange E. green 38. An Alpha (α) hemolysis is signified by a(n) halo surrounding a colony on blood agar. A. white B. clear/transluscent C. partial D. yellow or orange E. green 39. Which of the following tests could be used to differentiate ocular Gram (+) Streptococci as Streptococcus pyogenes or Streptococcus pneumoniae. A. "P" disc (optochin) B. Coagulase reaction or mannitol fermentation C. Catalase reaction D. "A" disc (bacitracin) E. Type of hemolysis 40. A β-hemolytic Streptococcus that is resistant to the "A" disc (bacitracin) is: A. Pseudomonas aeruginosa B. Streptococcus pneumoniae C. Serratia marsescens D. Streptococcus agalactiae E. Streptococcus pyogenes 11

12 41. Cytology of a conjunctival scrape for an eye having signs and symptoms of ocular inflammation is mononuclear, showing only many mononuclear cells like lymphocytes mixed among the epithelial cells. Without consideration of the signs and symptoms, the most likely diagnosis for this eye is: A. Bacterial infection B. Fungal infection C. Chlamydial infection D. Viral infection E. Protozoan infection 42. Cytology of a conjunctival scrape for an eye having signs and symptoms of ocular inflammation is polymorphic, showing PMNs and mononuclear cells like lymphocytes mixed among the epithelial cells. Without consideration of the signs and symptoms, the most likely diagnosis for this eye is: A. Bacterial infection B. Fungal infection C. Chlamydial infection D. Viral infection E. Protozoan infection 43. Cytology of a conjunctival scrape for an eye having signs and symptoms of ocular inflammation is polynuclear, showing only many polymorphonuclear cells. Without consideration of the signs and symptoms, the most likely diagnosis for this eye is: A. Bacterial infection B. Fungal infection C. Chlamydial infection D. Viral infection E. Protozoan infection 12

13 44. You cultured from a corneal ulceration of your patient onto blood agar and the laboratory sent back the results as negative (no growth). Which of the following is the most true? A. The ulcer is best referred to as a sterile ulcer. B. The ulcer is best referred to as a culture-negative ulcer. C. The ulcer is the result of a bacterial infection that merely did not grow on agar. D. The ulcer is the result of a viral infection. E. The ulcer is the result of a mycobacterial or fungal infection. 45. Which of these organisms is actually not a parasite, but merely an eye pathogen? A. Entamoeba histolytica B. Chlamydia trachomatis C. Acanthamoeba culbertsoni D. Herpes simplex E. Onchocerca volvulus 46. Three microorganisms that can thrive in waxy, oily environments and that are involved in most of the human eyelid infections and meibomian gland dysfunction are: A. Moraxella lacunata, Staphylococcus aureus, Candida albicans B. Moraxella lacunata, Haemophilus aegyptius, Mycobacterium fortuitum C. Haemophilus aegyptius, Streptococcus pneumoniae, Candida albicans D. Haemophilus influenzae, Streptococcus pneumoniae, Malassezia furfur E. Propionibacterium acnes, Staphylococcus aureus, Malassezia furfur 47. Intracellular parasites include all of the following except: A. Viruses B. Chlamydia C. Mycobacteria D. Microsporidia E. Toxoplasma gondii 13

14 48. In response to therapy with Amphotericin B, Candida albicans will most likely: A. change, in part, from a large colony form into a small colony form which is more resistant. B. change from a yeast into a more resistant mold. C. form spores which will be more resistant. D. form cysts which will be more resistant. E. be rendered nonviable but not killed. 49. Characteristics of the organism most associated with a keratoconjunctivitis involving blue-green purulence include the following except: A. Can penetrate the intact human corneal epithelium. B. Can feed off of sodium fluorescein in solution. C. Can penetrate the cornea 24 to 48 hours after initial infection. D. The most virulent corneal pathogen. E. Is involved with a significant number of contact lens-related eye infections. 50. Identify a bacterium or group of bacteria that is a gram (-) coccus: A. Haemophilus sp. B. Streptococcus pyogenese C. Moraxella catarrhalis D. Proteus mirabilis E. Serratia marcescens 51. What culture medium could be used to culture from eyes in order to consistently grow the greatest number of different fungal ocular pathogens? A. Chocolate agar B. Sabouraud's agar C. Thioglycolate broth D. Blood agar E. Trypticase soy agar 14

15 52. A fibrinous exudate is generally associated with a bacterium that causes a mucopurulent conjunctivitis. This organism is: A. Staphylococcus aureus B. Staphylococcus epidermidis C. Herpes simplex D. Corynebacterium diphtheriae E. Chlamydia trachomatis 53. You cultured from a corneal ulceration of your patient onto blood agar and the laboratory results were positive (4 colonies of Serratia marcescens). Which of the following is most true? A. The ulcer is best referred to as a sterile ulcer. B. The ulcer is the result of a mycobacterial or fungal infection. C. The ulcer is the result of a viral infection. D. The ulcer is a culture-positive ulcer with Serratia marcescens as the suspected causative agent. E. The ulcer is really culture-negative because the colonies were not derived from bacteria that came from the patient s cornea. 54. The patient complains of mild red eyes, bilaterally, that became red shortly after a weekend visit to the Yucatan Peninsula. Now 10 days later, a slight mucous discharge is present and your microbiologist sees inclusions within the cytoplasm of cells scraped from the conjunctival surface through a light microscope. Your diagnosis and treatment: A. Chlamydial infection, treat only with topical antibiotic. B. Chlamydial infection, treat with systemic and perhaps also topical antibiotics. C. Viral infection, untreatable, send for medical work up. D. Bacterial infection, treat with topical antibiotic. E. Montezuma s revenge, send for medical work up. 15

16 55. The following organism is an extracellular bacterium that can form a spore or cyst which makes the organism more resistant and its eye infections harder to treat: A. Acanthamoeba species B. Microsporidia sp. C. Bacillus cereus D. Pseudomonas aeruginosa E. Onchocerca volvulus 56. An α-hemolytic Streptococcus that is sensitive to ethyl hydrochloride is: A. Pseudomonas aeruginosa B. Serratia marsescens C. Bacillis cereus D. Streptococcus pyogenes E. Streptococcus pneumoniae 57. Identify a bacterium or group of bacteria that can be cultured from more than 5% of normal asymptomatic eyes: A. Bacillus species B. Corynebacterium sp. C. Listeria monocytogenes D. Proprionibacterium acnes E. Diplococcus pneumoniae 58. A presumed Herpes keratitis or corneal ulceration is: A. A corneal infection over which the anterior surface is raised, or presumed. B. A corneal infection thought to be caused by a Herpes-like virus. C. A corneal infection always surrounded by an immune ring. D. An Acanthamoeba infection before it is known as amoebic. E. A corneal infection surrounded by infiltration. 16

17 59. Lyme disease is caused by a systemic infection of: A. The spirochete, Borrelia burgdorferi. B. A species of Acanthamoeba. C. The Deer Tick. D. Treponema pallidum. E. Microsporidia 60. There is 1 bacterium that causes the majority of conjunctivitis cases in children over than 5 years old. What is this bacterium? (Circle one answer) A. Proprionibacterium acnes B. Streptococcus pneumoniae C. Moraxella lacunata D. Staphylococcus aureus E. Haemophilus aegyptius 61. When the UAB Hospital Microbiology Laboratory encounters a bacterial sample that it can not identify, the specimen is most often sent to which of the following state-run organizations: A. Ciba Vision Corporation in Atlanta B. Alabama State Microbiology Reference Laboratory C. UAB Hospitals Microbiology Laboratory D. Centers for Disease Control (CDC) in Atlanta E. Dr. William H. Benjamin in the UAB Microbiology department 62. The glove box incubator is used to process specimens for which types of cultures? A. Mycobacteria B. Aerobic bacteria C. Chlamydia D. Campylobacters E. Anaerobic bacteria 17

18 63. The automated instrument used to identify common gram-positive and gram-negative bacteria in the University Hospital Microbiology Laboratory is the: A. Bact Alert B. MicroScan C. Vitek D. Sensititre E. Autobac Part B: There are two correct answers for each of the questions 64 through 65. For each appropriate answer you will receive 2 points (4 points per question). 64. There are 5 groups of bacterial pathogens that can penetrate the intact corneal epithelium without previous trauma. Which 2 of the following are not among them? (Circle two answers) A. Streptococcus pneumoniae B. Acanthamoeba sp. C. Neisseria gonorrhoeae D. Corynebacterium diphtheriae E. Pseudomonas aeruginosa 65. There are 2 bacteria that cause the majority of conjunctivitis cases in children less than 5 years old. What are these two bacteria? (Circle two answers) A. Proprionibacterium acnes B. Streptococcus pneumoniae C. Moraxella lacunata D. Staphylococcus aureus E. Haemophilus aegyptius 18

19 Part C: There are three correct answers for each of the questions 66 through 74. For each appropriate answer you will receive 2 points (6 points per question). 66. Three of the following can create a corneal infection that may first appear like a Herpes simplex (HSV) keratitis. Which are they? (Circle three of the following) A. Adenovirus types 8 and 19 B. Acanthamoeba culbertsoni C. Toxocara cati D. Epstein-Barr Virus E. Varicella/Zoster Virus (VZV) 67. Viruses that are more virulent, or contagious, or that are more difficult to treat by drug therapy have certain general characteristics. What are three of these characteristics? (Circle three answers) A. They are generally small viruses B. They are generally RNA viruses C. They are generally non-enveloped viruses D. They are generally retroviruses E. They generally exit cells by cell lysis 68. There are seven pathological or suspected pathological eye conditions for which microbiological laboratory studies are thought to be mandatory (at least by the textbooks). What are three of these conditions? (Circle three answers) A. Hyperacute conjunctivitis B. Corneal ulceration C. Corneal abrasion D. Suspected fungal eye infection E. Follicular conjunctivitis 19

20 69. There are three ocular pathogens which adhere preferentially to human corneal epithelium and cause the overwhelming majority of human bacterial keratitis and corneal ulceration. What are these three microorganisms? (Circle three answers) A. Pseudomonas aeruginosa B. Corynebacterium diphtheriae C. Streptococcus pyogenes D. Staphylococcus aureus E. Streptococcus pneumoniae 70. There are 3 eye pathogens which are classically thought to be of a diplo variety, seen arranged microscopically in cell pairs. What are they? (Circle three answers) A. Neisseria gonorrhoea B. Moraxella lacunata C. Bacillus cereus D. Corynebacterium diphtheriae E. Streptococcus pneumoniae 71. There are 3 bacterial ocular pathogens which grow better using chocolate agar instead of blood agar in order to be cultured. What are they? (Circle three answers) A. Neisseria gonorrhoea B. Haemophilus aegyptius C. Pseudomonas aeruginosa D. Moraxella lacunata F. Bacillus cereus 20

21 72. What are three products specially designed to provide more effective eyelid hygiene in patients with mild blepharitis or, perhaps, to help prepare the eyelids prior to ocular surgery? (Circle three answers) A. Steri-Lid Eyelid Cleanser B. Dove Dishwashing Liquid C. Alcon Betadine 5% Ophthalmic Prep Solution D. OcuSoft Lid Scrub Plus E. Johnson & Johnson Baby Shampoo 73. Identify the 3 microorganisms known to prefer the low-ph, oily, waxy environment of the eyelid margins. (Circle three of the following) A. Acanthamoeba species B. Certain strains of Staphylococcus aureus C. Malassezia furfur D. Moraxella lacunata E. Propionibacterium acnes 74. Identify three devices or instruments used to obtain inoculum from corneal ulcerations for growth of microbiological organisms on agar plates. (Circle three of the following) A. Kimura spatula B. Dacron swab (with or without calcium alginate) C. Schirmer strip D. Mucus thread E. Cotton swab 21