Unit 5: Microbe-host interactions, microbial diseases and clinical microbiology - Practice Quiz

1 What term describes a relationship where both the host and the microbe benefit?

2 The community of microorganisms that normally live on and in the human body is called the:

3 A relationship in which one organism benefits while the other is unaffected is called:

4 A microorganism capable of causing disease is best described as a:

5 The degree or intensity of pathogenicity of a microorganism is known as its:

6 Toxins that are secreted by living bacteria into their surroundings are called:

7 An infection acquired during a stay in a hospital is termed a:

8 Which bacterium is the causative agent of tuberculosis?

9 Cholera, characterized by severe watery diarrhea, is caused by:

10 The bacterium responsible for tetanus is:

11 Which virus is the causative agent of AIDS?

12 Influenza in humans is caused by a virus belonging to which family?

13 COVID-19 is caused by which virus?

14 Oral thrush, a common fungal infection of the mouth, is usually caused by:

15 Ringworm (dermatophytosis) of the skin is caused by fungi commonly known as:

16 Malaria in humans is caused by protozoa of the genus:

17 Amoebic dysentery is caused by which protozoan?

18 Which staining technique is most commonly used to differentiate bacteria into two major groups based on cell wall structure?

19 Which rapid technique uses antigen-antibody binding to detect specific pathogens in a specimen?

20 Which molecular technique is used to amplify specific DNA sequences for identifying microorganisms?

21 A microorganism that resides on the human skin without causing disease but can become pathogenic when the host's immune system is compromised is best described as which type of organism?

22 In a symbiotic relationship where the microbe benefits while the host is neither harmed nor helped, the interaction is classified as:

23 A patient develops shock and multi-organ failure hours after a Gram-negative bacterial infection. The most likely mediator responsible is:

24 Which of the following best distinguishes an exotoxin from an endotoxin?

25 The ability of a pathogen to enter, multiply within, and spread through host tissues is collectively referred to as:

26 A patient presents with a thick grayish pseudomembrane over the tonsils and pharynx. The toxin responsible for this disease acts by:

27 Mycobacterium tuberculosis is difficult to stain with the Gram method primarily because of:

28 A patient with profuse watery ('rice-water') diarrhea is diagnosed with cholera. The cholera toxin causes fluid loss by:

29 HIV specifically infects CD4⁺ T-helper cells because its envelope glycoprotein gp120 binds to:

30 Influenza viruses undergo abrupt major changes in surface antigens through reassortment of genome segments, a process known as:

31 A hallmark of a latent viral infection, such as that caused by herpes simplex virus, is that the virus:

32 Oral thrush in an immunocompromised patient shows creamy white plaques. On microscopy, the causative organism most likely appears as:

33 Cryptococcus neoformans, a cause of meningitis in AIDS patients, is best identified in cerebrospinal fluid using:

34 The dimorphic nature of fungi such as Histoplasma capsulatum means they exist as:

35 A patient returning from a malaria-endemic region has cyclical fevers. The clinical fever pattern in Plasmodium infection corresponds to:

36 Entamoeba histolytica causes amoebic dysentery. The infective stage transmitted by the fecal-oral route is the:

37 When collecting a urine specimen for culture to detect a urinary tract infection, the recommended method to minimize contamination is:

38 A laboratory reports significant bacteriuria when a properly collected urine culture yields a colony count of at least:

39 A rapid diagnostic technique that uses fluorescently labeled antibodies to detect specific microbial antigens directly in a clinical specimen is called:

40 In clinical microbiology, MALDI-TOF mass spectrometry identifies bacteria rapidly by:

41 A germ-free (gnotobiotic) mouse is colonized with a single commensal Bacteroides species. Compared to a conventionally colonized mouse, which combination of outcomes is MOST expected in the gnotobiotic animal before colonization?

42 In a mutualistic relationship, the host provides nutrients while the microbe confers a benefit. Which scenario best illustrates a shift from mutualism to a pathobiont state rather than a stable commensal relationship?

43 A superantigen such as TSST-1 causes toxic shock by a mechanism distinct from conventional antigen presentation. Which statement correctly describes this mechanism?

44 Endotoxin (LPS) and exotoxins differ fundamentally. A patient's blood culture grows a Gram-negative rod and the patient develops DIC and hypotension. Which property is UNIQUE to the responsible LPS relative to typical exotoxins?

45 Mycobacterium tuberculosis survives inside macrophages by subverting phagosome maturation. Which molecular strategy is directly responsible for arresting phagosome-lysosome fusion?

46 Vibrio cholerae cholera toxin (CT) causes profuse watery diarrhea. The A1 subunit ADP-ribosylates a specific target. What is the downstream biochemical consequence?

47 HIV-1 reverse transcriptase lacks proofreading, giving a high mutation rate. Which clinical/evolutionary consequence follows MOST directly from this feature combined with high replication?

48 Influenza virus undergoes both antigenic drift and antigenic shift. A novel pandemic strain arises when two different influenza A subtypes co-infect one host cell. Which mechanism explains this?

49 Cryptococcus neoformans is a major cause of meningitis in AIDS patients. Which virulence factor is MOST directly responsible for its resistance to phagocytosis and is detected by the lateral-flow antigen (CrAg) test?

50 Candida albicans transitions between yeast and hyphal forms depending on environmental cues. Why is this dimorphic switching clinically significant during invasive candidiasis?

51 Plasmodium falciparum causes severe malaria partly through cytoadherence. Which parasite-encoded protein mediates sequestration of infected erythrocytes in the microvasculature?

52 Antigenic variation in Trypanosoma brucei allows chronic infection despite antibody responses. What is the molecular basis of this immune evasion?

53 A blood culture is flagged positive and Gram stain shows Gram-positive cocci in clusters. Which combination of downstream tests MOST rapidly distinguishes Staphylococcus aureus from coagulase-negative staphylococci and from streptococci?

54 A urine specimen from a catheterized patient grows CFU/mL of a single organism. In interpreting significant bacteriuria, why must this result be viewed cautiously?

55 MALDI-TOF mass spectrometry has transformed clinical identification. What is the fundamental principle that allows species-level identification within minutes?

56 A rapid latex agglutination test for a capsular antigen gives a positive result in a CSF sample, but the Gram stain and culture are negative. Which explanation is MOST consistent with a TRUE positive rather than a false positive?

57 In a real-time (quantitative) PCR assay for viral load, the cycle threshold () value relates to starting template. If Sample A has a of 20 and Sample B a of 30 with 100% efficiency, how do their initial template amounts compare?

58 16S rRNA gene sequencing is widely used to identify bacteria. Which limitation is MOST important when relying on it for clinical species-level identification?

59 Gas-liquid chromatography (GLC) analysis of short-chain and long-chain fatty acids is used in anaerobe identification. What does GLC actually measure to aid identification?

60 A patient develops hemolytic-uremic syndrome (HUS) after infection with Shiga toxin-producing E. coli (STEC). What is the precise molecular action of Shiga toxin that leads to endothelial damage?