A DAMB 711 Microbiology Exam 2A 100 points September 27, 2011 Your name: _____________________________________________ Exam # ___________ Seat # ____________ 1 I. Multiple Choice: Choose the ONE BEST answer. Mark the correct answer in Part 1 of your answer sheet. 1. Which of the following conveys the highest risk of nosocomial infection to a hospitalized patient? A. the hospital environment (rooms, floors, fomites) B. invasive medical devices (catheters, respirators, etc.) C. hospital personnel, including physicians D. mechanical vectors 2. The clonality of pathogenic bacteria refers to: A. the environmental regulation of genes encoding virulence factors B. the acquisition of virulence determinants encoded on extra-chromosomal elements C. the infective dose of a specific species of bacteria D. opportunistic pathogens E. only a few strains in a species will be the etiologic agent of a disease 3. Diseases caused by this genus of bacteria are never transmitted through contaminated food. A. Listeria B. Staphylococcus C. Mycobacteria D. Corynebacteria 4. When Vibrio cholera is moved from a high salt, basic environment to isotonic conditions, with neutral pH a sensor kinase in the bacterium phosphorylates a response regulator that initiates transcription. This is an example of: A. the environmental regulation of genes encoding virulence factors B. the acquisition of virulence determinants encoded on extra-chromosomal elements C. the infective dose of a specific species of bacteria D. opportunistic pathogens E. only a few strains in a species will be the etiologic agent of a disease 5. In which form of tuberculosis is a patient coughing up infectious material? A. miliary B. active C. latent/dormant D. primary E. disseminated 2 6. The life threatening manifestation of diphtheria that is most frequently the cause of death is: A. the pseudo-membrane B. heart failure caused by toxemia C. transient paralysis caused by toxemia D. bull neck 7. What are Molecular Koch's Postulates trying to determine? A. the bacterium or other microorganism that is the etiologic (causative) agent of a disease B. the virulence determinant (gene) that encodes the major virulence factor of a pathogenic microorganism C. an appropriate animal model for a disease D. both A and B E. both B and C 8. What are Koch's Postulates trying to determine? A. the bacterium or other microorganism that is the etiologic (causative) agent of a disease B. the virulence determinant (gene) that encodes the major virulence factor of a pathogenic microorganism C. an appropriate animal model for a disease D. both A and B E. both B and C 9. A bacterium found in dental plaque that may actually kill other bacteria through metabolic synthesis of hydrogen peroxide and raise the pH of plaque through metabolic synthesis of ammonia is: A. Streptococcus mutans B. S. gordonii C. S. salivarius D. S. sanguinis E. S. mitis 10. Injection of PPD (purified protein derivative) sub-dermally with resulting induration and inflammation in 48 to 72 hours without an X-ray showing a tubercle indicates a patient: A. has been infected with M. tuberculosis B. has been infected with M. tuberculosis or an atypical mycobacterium C. should have his or her sputum cultured for mycobacteria D. B and C E. A, B and C 3 11. A bacterium is swallowed and adheres to the mucous membranes of the host gastrointestinal tract; it begins to metabolize and replicate in the area of infection: it releases LPS which stimulates the release of massive quantities of inflammatory mediators. The bacterium avoids destruction by the host immune system by preventing complement activation. A. This bacterium will cause disease. B. This bacterium could do all of these things and still not be able to cause disease. Many bacteria are intracellular parasites with specialized mechanisms for survival in the macrophage. In questions 12 and 13, below, use the following choices to identify the mechanism the bacterium used to survive the macrophage. A. Escapes the endosome. B. Prevents fusion of the phagosome and lysosome. C. Activates transcription of an acid tolerance response gene. A12. Listeria monocytogenes B13. Mycobacterium tuberculosis 14. Subacute bacterial endocarditis (SBE) differs from acute endocarditis in that: A. Staphylococcus aureus is the etiological agent B. patients with mitral valve condition are predisposed to SBE and not acute endocarditis C. patients run low grade fevers and symptoms persist for months D. Viridans streptococci and Enterococcus faecalis are frequent causes E. C and D are true. 15. Bacteria that are acid fast: A. will not retain a primary stain if acid is used as a decolorizing agent. B. will retain a primary stain even if acid is used as a decolorizing agent. C. have very low percentages of lipid in their cell walls. D. do not have mycolic acids in their cell walls. 16. A mycolic acid that can cause wasting disease when injected into mice is: A. Wax D. B. sulfolipid C. cord factor D. Actin A E. A and B 4 17. Patients that are compromised in cell mediated immunity: A. are more susceptible to Listeria monocytogenes B. are more susceptible to Mycobacterium tuberculosis. C. are more susceptible to Streptococcus pyogenes. D. Both A and B. E. Both B and C. 18. Infections caused by bacteria that develop resistance to this anti-microbic are untreatable unless new anti-microbics can be developed to take its place. A. penicillin B. cephalosporin C. sulfonamide D. vancomycin 19. The anti-microbic action of the sulfonamides is due to their molecular: A. resemblance to acyl-d-alanylalanine B. resemblance to penicillin binding proteins (PBPs) C. resemblance to para-aminobenzoic acid (PABA) D. resemblance to trimethoprim 20. Characteristics of the Staphylococcus aureus enterotoxin that make it a dangerous cause of food poisoning: A. It resists heat. B. Staphylococcus aureus grows in high salt environments. C. It resists proteases such as trypsin. D. A and C. E. A, B and C. 21. The exfoliative toxin is produced by ______________ and it causes the symptoms of __________________. A. Enterococcus faecalis; scalded skin syndrome B. Streptococcus pyogenes; scarlet fever C. Staphylococcus aureus; scalded skin syndrome D. Streptococcus pneumoniae E. Staphylococcus aureus; impetigo 22. Mannitol salt agar is selective and differential for __________________. The selective component is _______________; the differential component is ________. A. Enterococcus faecalis; 7.5% sodium chloride; mannitol B. Staphylococcus aureus; 7.5% sodium chloride; mannitol C. Corynebacterium diphtheria; tellurite; mannitol D. Staphylococcus aureus; mannitol; 7.5% sodium chloride E. Streptococcus pneumoniae; optochin; -hemolytic response 5 23. Protein A is: A. Useful for serotyping strains of Streptococcus pyogenes. B. A protein that is a virulence determinant for Staphylococcus aureus and can activate fibrinogen to cause clot formation around the bacterial cell. C. A unique cell surface protein of Staphylococcus aureus that contributes to the virulence of the bacterium by binding the Fc region of immunoglobulins D. Toxic for white blood cells. E. Carried on a temperate bacteriophage 24. The best explanation for the influence of iron on expression of the diphtheria toxin is: A. The gene for the diphtheria toxin is encoded by a prophage. The prophage controls expression of the toxin protein through a repressor protein that is inactive in the presence of iron. B. The gene for the diphtheria toxin is encoded by a prophage. A repressor protein encoded on the host chromosome regulates expression of the toxin gene. Iron is a co-repressor. In conditions of plentiful iron, it binds the repressor protein, DtxR; the iron/DtxR complex then binds the tox gene promoter to prevent transcription. C. The gene for the diphtheria toxin is encoded by a prophage. A second prophage controls expression of the toxin protein through a repressor protein. Iron is a co- repressor; in high iron concentrations it dissociates from the DtxR repressor resulting in expression of the toxin gene. D. The gene for the diphtheria toxin is encoded by a prophage. A repressor protein encoded on the host chromosome regulates expression of the toxin gene. Iron is a co-repressor. In low iron concentrations iron dissociates from the repressor protein (DtxR) resulting in expression of the toxin gene. E. Both B and D are correct. 6 25. A method used by epidemiologists to determine the source of nosocomial infections caused by S. aureus is: A. serotyping B. pyocin typing C. phage (bacteriophage) typing D. cell wall composition For the bacteria that cause caries, below, answer: A. If it is a human strain. B. If it is an animal strain. C. If it is not cariogenic A26. Streptococcus sobrinus B27. Streptococcus maccaccae B28. Streptococcus cricetus A29. Streptococcus mutans B30. Streptococcus ferus B31. Streptococcus rattus C32. Streptococcus agalactiae 33. A Staphylococcus aureus that cannot produce this enzyme is avirulent. A. catalase B. lipase C. coagulase D. hyaluronidase E. staphylokinase 34. “Acidogenic” describes a characteristic that conveys virulence to the etiologic agents of: A. Ludwig’s angina B. strep throat C. sub-acute bacterial endocarditis D. osteomyelitis E. caries 35. Antimicrobics that inhibit peptidoglycan synthesis attack this biosynthetic precursor: A. acyl-d-alanylalanine B. penicillin binding proteins (PBPs) C. para-aminobenzoic acid (PABA) D. N-acetylglucosamine-N-acetylmuramic acid (NAM-NAG) E. DNA dependent RNA polymerase 7 36. The diphtheria toxin has the same effect on procarytic