FMGE Microbiology questions, organised for recall

1. Q1. An infant has absent T and B lymphocyte function, and deoxyadenosine accumulates to levels toxic to lymphocytes. Deficiency of which enzyme causes this?

   • A. Thymidine phosphorylase
   • B. Adenosine deaminase
   • C. Arginase
   • D. Xanthine oxidase

   Answer: B. Adenosine deaminase

2. Q2. Within minutes of a wasp sting a patient develops stridor, urticaria and hypotension. The reaction is mediated by antibody bound to which cell-surface receptor?

   • A. Fc-gamma-RIII on natural killer cells
   • B. Complement receptor 1 on erythrocytes
   • C. Fc-epsilon-RI on mast cells
   • D. MHC class II on macrophages

   Answer: C. Fc-epsilon-RI on mast cells

1. Q1. A man with HIV and a CD4 count of 90 has a dry cough, desaturation on exertion, bilateral perihilar ground-glass change and a raised LDH. Which organism is most likely, and how is it confirmed?

   • A. Pneumocystis jirovecii, on induced sputum or lavage with silver or immunofluorescent staining
   • B. Cryptococcus neoformans, on India ink staining of sputum
   • C. Mycobacterium tuberculosis, on Ziehl-Neelsen staining
   • D. Aspergillus fumigatus, on serum galactomannan alone

   Answer: A. Pneumocystis jirovecii, on induced sputum or lavage with silver or immunofluorescent staining

2. Q2. A woman's red cells fail to agglutinate with anti-A, anti-B and anti-H, and her serum agglutinates group O donor cells. Which blood can she safely receive?

   • A. O negative blood
   • B. AB positive blood
   • C. Blood from another Bombay phenotype donor only
   • D. Any group, since she carries neither A nor B antigen

   Answer: C. Blood from another Bombay phenotype donor only

1. Q1. Stool is plated on MacConkey agar; some colonies turn pink while others stay pale. What does the colour difference show, and what produces it?

   • A. Haemolysis, which clears the medium around the colony
   • B. Hydrogen sulphide production, which blackens the colony
   • C. Urease activity, which raises the pH
   • D. Lactose fermentation, which lowers pH and turns the neutral red indicator pink

   Answer: D. Lactose fermentation, which lowers pH and turns the neutral red indicator pink

2. Q2. A man has a single painless genital ulcer with an indurated base and rubbery non-tender inguinal nodes, three weeks after exposure. Serology is still negative. What will confirm the diagnosis now?

   • A. Dark field microscopy of serum expressed from the ulcer base
   • B. Gram stain of the ulcer exudate
   • C. Tzanck smear from the ulcer edge
   • D. Culture on Thayer-Martin medium

   Answer: A. Dark field microscopy of serum expressed from the ulcer base

1. Q1. A child develops a papule on the hand a week after being scratched while playing, followed by tender axillary lymphadenopathy and low-grade fever. Which organism is responsible?

   • A. Francisella tularensis
   • B. Bartonella henselae
   • C. Pasteurella multocida
   • D. Yersinia pestis

   Answer: B. Bartonella henselae

2. Q2. A woman has frothy, foul-smelling vaginal discharge with intense itching and a punctate haemorrhagic cervix. Which statement about the causative organism is FALSE?

   • A. It is transmitted almost exclusively by sexual contact
   • B. Metronidazole is the treatment of choice
   • C. It exists in both trophozoite and cyst forms
   • D. Motile organisms may be seen on a saline wet mount

   Answer: C. It exists in both trophozoite and cyst forms

1. Q1. A young woman has itchy hypopigmented scaly patches over the chest and back. KOH mounts show short curved hyphae with clusters of round yeast cells. Which organism, and why does the pigment change occur?

   • A. Trichophyton rubrum, which invades the hair shaft
   • B. Malassezia furfur, whose azelaic acid inhibits melanocyte tyrosinase
   • C. Candida albicans, which forms pseudohyphae
   • D. Microsporum canis, which fluoresces under Wood's lamp

   Answer: B. Malassezia furfur, whose azelaic acid inhibits melanocyte tyrosinase

2. Q2. A poorly controlled diabetic presents with black necrotic tissue filling the nasal cavity and eroding the hard palate. Which fungus is responsible, and what makes diabetic ketoacidosis such a strong risk factor?

   • A. Aspergillus fumigatus, which needs neutropenia to invade
   • B. A Mucorales species, because acidosis frees iron from transferrin and impairs phagocyte function
   • C. Candida albicans, because of mucosal overgrowth
   • D. Cryptococcus neoformans, because of impaired cell-mediated immunity

   Answer: B. A Mucorales species, because acidosis frees iron from transferrin and impairs phagocyte function

1. Q1. A child has profuse painless watery stools described as rice-water, with rapid dehydration and no fever. Which organism, and what is the mechanism of the diarrhoea?

   • A. Vibrio cholerae, whose toxin raises cyclic AMP and drives chloride secretion
   • B. Shigella dysenteriae, which invades colonic mucosa
   • C. Entamoeba histolytica, which causes flask-shaped ulcers
   • D. Enterohaemorrhagic E. coli, which causes haemolytic uraemic syndrome

   Answer: A. Vibrio cholerae, whose toxin raises cyclic AMP and drives chloride secretion

2. Q2. Which mosquito transmits Zika, dengue and chikungunya, and what feature of its behaviour makes control difficult?

   • A. Anopheles species, which bite at night
   • B. Culex quinquefasciatus, which breeds in dirty water
   • C. Aedes aegypti and Aedes albopictus, which bite by day and breed in small clean domestic water collections
   • D. Mansonia species, which attach to aquatic plants

   Answer: C. Aedes aegypti and Aedes albopictus, which bite by day and breed in small clean domestic water collections

1. Q1. A man has a sharply demarcated, raised, painful erythematous plaque on the shin with fever and a clear border against normal skin. Which organism, and which layer of skin is involved?

   • A. Staphylococcus aureus, involving the deep dermis and fat
   • B. Streptococcus pyogenes, involving the upper dermis and superficial lymphatics
   • C. Haemophilus influenzae type b, involving subcutaneous tissue
   • D. Clostridium perfringens, involving fascia and muscle

   Answer: B. Streptococcus pyogenes, involving the upper dermis and superficial lymphatics

2. Q2. Which specimen and test confirm SARS-CoV-2 infection in a symptomatic patient, and why is that method chosen?

   • A. Serum antibody testing, because it detects recent infection
   • B. Chest CT alone, because the pattern is specific
   • C. A nasopharyngeal swab tested by reverse transcription PCR, because it detects viral RNA directly
   • D. Blood culture, because viraemia is constant

   Answer: C. A nasopharyngeal swab tested by reverse transcription PCR, because it detects viral RNA directly

3. Q3. An outbreak of unknown cause requires simultaneous testing for several candidate pathogens from one sample. Which PCR format is designed for this?

   • A. Multiplex PCR, using several primer pairs in one reaction
   • B. Nested PCR, using two sequential primer pairs
   • C. Real-time PCR, quantifying a single target
   • D. Reverse transcription PCR, converting RNA to cDNA

   Answer: A. Multiplex PCR, using several primer pairs in one reaction

1. Q1. Small white spots on an erythematous buccal mucosa appear two days before a rash. What are they called, and which infection do they signal?

   • A. Forchheimer spots, in rubella
   • B. Koplik spots, in measles
   • C. Nagayama spots, in roseola
   • D. Aphthous ulcers, in Behcet disease

   Answer: B. Koplik spots, in measles

2. Q2. Which organism's spores are used as the biological indicator for validating steam autoclave cycles, and at what temperature?

   • A. Bacillus atrophaeus at 160 degrees C dry heat
   • B. Clostridium tetani spores at 100 degrees C
   • C. Geobacillus stearothermophilus at 121 degrees C moist heat
   • D. Pseudomonas aeruginosa at 80 degrees C

   Answer: C. Geobacillus stearothermophilus at 121 degrees C moist heat

1. Q1. Which statement correctly describes the diphtheritic membrane?

   • A. A grey membrane confined to the tonsil that peels away cleanly
   • B. A grey pseudomembrane extending beyond the tonsils that bleeds when removed, because it is adherent to necrotic mucosa
   • C. A white curdy membrane wiped off easily
   • D. A yellow membrane limited to the soft palate

   Answer: B. A grey pseudomembrane extending beyond the tonsils that bleeds when removed, because it is adherent to necrotic mucosa

2. Q2. Which mechanism of bacterial gene transfer is mediated by a bacteriophage, and what is its practical significance?

   • A. Conjugation, transferring plasmids through a pilus
   • B. Transformation, taking up naked DNA
   • C. Transduction, which can carry toxin genes such as those of Corynebacterium diphtheriae
   • D. Transposition, moving genes within a genome

   Answer: C. Transduction, which can carry toxin genes such as those of Corynebacterium diphtheriae

1. Q1. Biopsy from a chronic verrucous foot lesion shows thick-walled, brown, septate sclerotic bodies dividing by internal septation. What is the diagnosis?

   • A. Histoplasmosis
   • B. Chromoblastomycosis
   • C. Coccidioidomycosis
   • D. Candidiasis

   Answer: B. Chromoblastomycosis

2. Q2. How does Bacillus anthracis appear on Gram stain, and what arrangement is characteristic?

   • A. Gram-positive cocci in clusters
   • B. Gram-negative diplococci
   • C. Gram-positive rods with squared ends in chains, resembling bamboo
   • D. Gram-positive bacilli with spherical ends

   Answer: C. Gram-positive rods with squared ends in chains, resembling bamboo

Every FMGE session paper, all 19 subjects together, is on our previous year questions page.