Mcq of the day Microbiology

Mcq of the day

Microbiology QuizMycobacteria questions

1. A 65 yr old man c/o low grade fever at night with periods of shaking chills and coughing up blood in sputum. An acidfaststain of the sputum shows AFB. The virulence factor of the organism is encoded by _____ gene

(A) Amp C

(B) kat G

(C) vpr

(D) vpu

Answer: Option (B) is the correct answer

Reference: Harrison’s Infectious Diseases; Pg 600

Option (B): The katGgene encodes for catalase/peroxidase enzymes that protectmycobacterium against oxidative stress

Option (A): AmpC confers drug resistance in gram negative bacilli

Option (C), (D) : Non structural genes of HIV

2. A homeless man unexpectedly died in a nighttime shelter. An acidfast

stain slide of tissue from the lungs during autopsy revealed AFB.HPE of the lung tissue showed granuloma with caseous necrosis. The probable host response is

(A) Delayed hypersensitivity

(B) humoral immune response

(C) Cell mediated immune response

(D) innate immunity

Answer: Option (C) is the correct answer

Reference: Apurba Sastry Essentials of Medical Microbiology, 2nd edition 283

Option (C): The formation of soft tubercle with caseous necrosis is a favourable sign of good host cell mediated immune response. Growth of M. tuberculosis is inhibited within this necrotic environment because of low oxygen tension and low pH. Eventually, the lesion heals and calcifies

Option (A): In patients with risk factors CMI is weak; bacilli is more virulent and hence there is a delayed hypersensitivity reaction (DTH) which leads to lung tissue destruction

Option (B): humoral immune response has a minor role.

3. A 45yr old man presented to the skin OPD with leonine facies, eyebrow alopecia, symmetric multiple infiltrated nodules and ulnar nerve palsy. A skin biopsy in this patient will reveal a bacteriological index of

(A) 0-1 +

(B) 2-3+

(C) 3-5+

(D) 4-6+

Answer: Option (D) is the correct answer

Reference: Harrison’s Infectious diseases; Pg 620

Option (D): The clinical picture is suggestive of lepromatous leprosy. The Bacteriological index in LL is 4-6+

Option (A): The Bacteriological index in Tuberculoid leprosy (TT, BT) is 0-1++

Option (C): The Bacteriological index in Borderline leprosy is 3-5+

4. A 40yr old woman presents to skin OPD with 2 sharply defined annular patch in the left forearm. The skin lesion was anaesthetic. The possibility of eliciting an IgM antibody response to M.leprae  PGL-1 in this patient is

(A) 60%

(B) 75%

(C) 85%

(D) 95%

Answer: Option (A) is the correct answer

Reference: Harrison’s Infectious Diseases; Pg 620

Option (A): Theclinical picture is suggestive of tuberculoid leprosy. In tuberculoid leprosy—patients have significant antibodies to PGL-1 only 60% of the time

Option (C): IgM antibodies to PGL-1 are found in 85% of Borderline (BB, BL leprosy patients

Option (D): IgM antibodies to PGL-1 are found in 95% of untreated lepromatous leprosy patients

5. A 35yr old man was diagnosed with MDR TB and was started on DOTS plus regimen. All the following drugs are a part of the regimen except

(A) Kanamycin

(B) Clarithromycin

(C) Cycloserine

(D) Ofloxacin

Answer: Option (B) is the correct answer

Reference: : Apurba Sastry Essentials of Medical Microbiology 2ndedition pg no: 293

Option (B): DOTS plus regimen does not include clarithromycin.

Option (A), (C), (D): DOTS plus regimen include a) intensive phase – kanamycin, Ofloxacin or Levofloxacin, Ethionamide, Cycloserine, Pyrazinamide, Ehtambutol with or without Isoniazid. b)Continuation phase – Ofloxacin or Levofloxacin, Ethionamide, Cycloserine, Ehtambutol

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