Microbiology Mock Exams 3

Which of the following Enterobacterales is a lactose non-fermenter?

a. Escherichia coli

b. Klebsiella pneumoniae

c. Enterobacter cloacae

d. Salmonella enterica

D

The most common cause of community-acquired UTI is:

a. Proteus mirabilis

b. Escherichia coli

c. Klebsiella pneumoniae

d. Pseudomonas aeruginosa

B

Which characteristic is typical for Enterococcus spp.?

a. Catalase positive

b. Growth in 6.5% NaCl

c. Oxidase positive

d. Spore-forming

B

Listeria monocytogenes is best described as:

a. An extracellular pathogen that produces endotoxin

b. An intracellular pathogen that invades mononuclear phagocytes

c. An obligate intracellular bacterium (cannot grow on artificial media)

d. A strictly anaerobic spore former

B

Human herpesvirus 8 (HHV-8) is associated with:

a. Burkitt lymphoma

b. Kaposi sarcoma

c. Infectious mononucleosis

d. Roseola infantum

B

Primary EBV infection can present as:

a. Asymptomatic infection

b. Infectious mononucleosis

c. Burkitt lymphoma

d. a + b

D

Which statement is TRUE about hepatitis A virus (HAV)?

a. It commonly causes chronic hepatitis

b. It is an enveloped DNA virus

c. It elicits protective immunity after infection

d. It is mainly transmitted by blood transfusion

C

Which patient can be infected with hepatitis D virus?

a. Anti-HCV positive

b. Anti-HAV IgG positive

c. Anti-HEV IgM positive

d. HBsAg positive

D

In which case can a patient be HCV RNA positive but anti-HCV negative?

a. Never

b. After effective treatment

c. Very recent HCV exposure

d. After vaccination

C

Dimorphic fungi grow:

a. As mould at 37°C and as yeast at 30°C

b. As mould at 30°C and as yeast at 37°C

c. As mould at both 30°C and 37°C

d. As yeast at both 30°C and 37°C

B

The most common source of Candida bloodstream infection in hospitalized patients is:

a. Endogenous GI colonization with translocation

b. Catheters/medical devices

c. Skin flora only

d. None of the above

B

The main route of infection for Aspergillus spp. is:

a. Inhalation of airborne conidia

b. Sexual transmission

c. Fecal-oral transmission

d. Vector-borne transmission

A

"Gold standard" for laboratory diagnosis of Chlamydia trachomatis infection in routine

practice is:

a. Direct immunofluorescence

b. Culture

c. Nucleic acid amplification tests (NAATs)

d. ELISA for IgG

C

Which statement is NOT true about Mycoplasma pneumoniae?

a. It causes infections worldwide

b. It produces an exotoxin that directly destroys respiratory epithelium

c. It can cause atypical pneumonia

d. It lacks a cell wall

B

Primary HPV oncoproteins are:

a. E1 + E2

b. E4 + E5

c. E6 + E7

d. L1 + L2

C

Which statement is TRUE?

a. Rubella incubation period is <4 days

b. >80% of rubella infections are symptomatic

c. Best screening for rubella immunity is rubella-specific IgM

d. Women of childbearing age should be screened for rubella IgG and vaccinated if IgG

negative

D

In bacterial meningitis, CSF is typically:

a. Clear and colorless

b. Cloudy and xanthochromic

c. Slightly cloudy and colorless

d. Bloody (pinkish)

C

Rapid diagnosis of HSV encephalitis is important because:

a. HSV is a common cause of focal encephalitis

b. Early antiviral therapy improves outcomes

c. HSV becomes latent in nerve ganglia

d. All of the above

D

The most characteristic clinical sign of Lyme disease is:

a. Relapsing fever

b. Expanding ring-like erythema (erythema migrans)

c. Facial nerve palsy as the first sign always

d. Arthritis is never seen

B

Neutralizing antibodies against coronaviruses are mainly directed against:

a. Nucleocapsid (N)

b. Spike (S)

c. Membrane (M)

d. Envelope (E)

B

Which pathogen causing acute localized GI infection in adults has NO animal reservoir?

a. Campylobacter jejuni

b. Shigella spp.

c. Salmonella enteritidis

d. Yersinia enterocolitica

B

Which neurological complication is associated with Zika virus infection?

a. Parkinson disease

b. Guillain-Barré syndrome

c. Alzheimer disease

d. Multiple sclerosis

B

A serious complication of West Nile virus infection is:

a. Encephalitis

b. Endocarditis

c. Arthritis

d. Hemorrhage

A

Brill-Zinsser disease is caused by:

a. Rickettsia rickettsii

b. Rickettsia typhi

c. Rickettsia prowazekii

d. Orientia tsutsugamushi

C

Paroxysmal coughing fits in pertussis belong mainly to:

a. Catarrhal stage (early)

b. Paroxysmal stage (later)

c. Convalescent stage only

d. Incubation period

B

"Gold standard" for diagnosis of brucellosis is:

a. Blood culture

b. Rapid antigen detection

c. Widal test

d. Microscopy of stool

A

Clinical disease due to Mycobacterium tuberculosis is definitively diagnosed by:

a. Culture of the organism from clinical specimens

b. Chest X-ray only

c. Mantoux test only

d. Symptoms plus IGRA alone

A

Main disadvantage of Sabin oral polio vaccine (OPV) is:

a. It cannot induce mucosal immunity

b. It is inactivated and weakly immunogenic

c. It can revert to neurovirulence

d. It must be injected intramuscularly

C

Pityriasis versicolor is caused by:

a. Candida albicans

b. Malassezia spp.

c. Dermatophytes

d. Aspergillus fumigatus

B

Dermatophyte infections are reliably diagnosed by:

a. Serology

b. Direct microscopy + culture from skin/hair/nail

c. Blood culture

d. PCR only is mandatory

B

Cornerstone of infective endocarditis diagnosis (microbiological) is:

a. Positive blood cultures

b. Urine culture

c. Stool culture

d. Throat swab culture

A

Paramyxoviruses have:

a. dsDNA genome

b. +ssRNA genome

c. −ssRNA genome

d. No envelope

C

Enteroviruses:

a. Are transmitted only via respiratory droplets

b. Are an important cause of viral aseptic meningitis

c. Are enveloped viruses

d. Do not survive in the environment

B

Rhinoviruses:

a. Commonly cause upper respiratory tract infections (common cold)

b. Are most often detected in stool

c. Are transmitted mainly by fecal-oral route

d. Cannot infect the upper airway

A

Chagas disease (South American trypanosomiasis):

a. Is treated with antimonial compounds

b. Is usually an acute self-limited illness

c. Can cause chronic disease that is difficult to treat

d. Is caused by Trypanosoma brucei

C

Toxoplasmosis is best confirmed by:

a. Demonstration of parasites in peripheral blood smear in immunocompetent host

b. Rising titer of specific serum antibodies alone is always confirmatory

c. Detection of parasite DNA (PCR) in amniotic fluid/CSF in appropriate setting

d. Finding cysts routinely in stool

C

Which statement is NOT true about Corynebacterium diphtheriae?

a. Toxin can cause systemic effects

b. Toxin affects heart and peripheral nerves

c. Widespread vaccination has reduced disease

d. Cutaneous diphtheria never produces toxin

D

Which statement is NOT true about Nocardia?

a. Pulmonary disease occurs only in immunocompromised patients

b. It is aerobic and branching

c. It can be weakly acid-fast

d. It can cause brain abscesses

A

Vaginitis is NOT caused by:

a. Candida albicans

b. Trichomonas vaginalis

c. Gardnerella vaginalis

d. Neisseria gonorrhoeae

D

The most common threadworm worldwide is:

a. Enterobius vermicularis

b. Ascaris lumbricoides

c. Trichinella spiralis

d. Taenia saginata

A

Most commonly used confirmatory test for HIV (classic approach) is:

a. ELISA alone

b. Western blot / immunoblot (confirmatory)

c. CRP

d. Gram stain

B

Fever of unknown origin (classic definition) includes:

a. Temperature >38.3°C with illness >3 weeks and no diagnosis after evaluation

b. Temperature <37°C with fatigue

c. Any fever for 24 hours

d. Only fevers due to cancer

A

Ziehl-Neelsen stain is used mainly to identify:

a. Mycobacteria (acid-fast bacilli)

b. Malaria parasites

c. Fungi

d. Helminths

A

Vaccines are available for:

a. Haemophilus influenzae type b

b. All Haemophilus influenzae strains equally

c. Only non-typeable H. influenzae

d. H. influenzae type a only

A

Tetanospasmin acts mainly by:

a. Blocking acetylcholine release at NMJ causing flaccid paralysis

b. Inhibiting release of GABA and glycine in inhibitory interneurons

c. Inhibiting DNA synthesis in neurons

d. Activating complement

B

Clostridium tetani microscopic appearance:

a. Gram-negative rods with capsules

b. Gram-positive rods with terminal spores ("drumstick")

c. Gram-positive cocci in chains

d. Gram-negative diplococci

B

Needing fewer Vibrio cholerae organisms after taking antacids suggests:

a. Antacids are antibiotics

b. Gastric acid is a protective barrier

c. Antacids increase intestinal motility

d. Cholera toxin is destroyed by antacids

B

Most common gram-negative bacterium in burn wound infections is:

a. Streptococcus pyogenes

b. Pseudomonas aeruginosa

c. Staphylococcus epidermidis

d. Corynebacterium diphtheriae

B

Most commonly associated with Guillain-Barré syndrome:

a. Campylobacter jejuni

b. Helicobacter pylori

c. Shigella dysenteriae

d. Vibrio cholerae

A

Orthomyxoviruses are:

a. dsDNA viruses

b. +ssRNA non-segmented

c. −ssRNA segmented

d. dsRNA segmented

C

The herpesvirus genome is:

a. Linear dsDNA

b. Circular ssRNA

c. Linear +ssRNA

d. Segmented dsRNA

A

Most typical bacterial cause of acute pharyngotonsillitis:

a. Staphylococcus epidermidis

b. Streptococcus pyogenes

c. Haemophilus influenzae

d. Pseudomonas aeruginosa

B

In the satellitism test:

a. H. influenzae grows near S. aureus on blood agar

b. S. aureus grows near H. influenzae

c. Mycobacterium grows near S. aureus

d. H. influenzae grows best on MacConkey

A

Which statement is NOT true about leptospirosis?

a. It is caused by Leptospira

b. It is zoonotic

c. Infection cannot occur through skin abrasions

d. Contaminated water with animal urine can transmit infection

C

Symptoms associated with cystitis include:

a. Strong persistent urge to urinate

b. Pelvic discomfort

c. Low grade fever can occur

d. All of the above

D

Which statement is NOT true about secondary syphilis?

a. Rash may appear on trunk and extremities

b. Lesions of secondary syphilis are non-infectious

c. Lymphadenopathy can occur

d. Symptoms can resolve and serology remains positive

B

Which drug can be used for some environmental (non-tuberculous) mycobacterial

infections?

a. Rifampicin

b. Ethambutol

c. Ciprofloxacin (depending on species)

d. All of the above

D

What is TRUE about Neisseria meningitidis?

a. It has multiple serogroups

b. Carriage in nasopharynx occurs and transmission is via close contact

c. A proportion of healthy people are carriers

d. All of the above

D

If "red" microorganisms appear on Ziehl-Neelsen stain of sputum, the specimen is:

a. Negative for acid-fast organisms

b. Positive for acid-fast microorganisms

c. Positive for fungal hyphae

d. Positive for spirochetes

B

Which statement is NOT true about congenital Parvovirus B19 infection?

a. It can cause severe anemia and heart failure (hydrops)

b. There is minimal risk of fetal death in 2nd trimester infection

c. Maternal infection does not automatically warrant termination

d. There is no evidence of teratogenicity

B

Which medium is most useful to identify lactose fermenters among Enterobacterales?

a. Blood agar

b. MacConkey agar

c. Chocolate agar

d. Lowenstein-Jensen

B

A key biochemical feature of Proteus mirabilis is:

a. Oxidase positive

b. Urease positive with swarming motility

c. Catalase negative

d. Strict anaerobe

B

Which organism is classically associated with "currant jelly sputum"?

a. E. coli

b. Klebsiella pneumoniae

c. Shigella sonnei

d. Yersinia pestis

B

The shiga toxin mechanism is best described as:

a. ADP-ribosylation of Gs increasing cAMP

b. Cleavage of SNARE proteins blocking inhibitory neurotransmitters

c. Inactivation of 60S ribosomal subunit

d. Activation of guanylate cyclase increasing cGMP

C

Which organism most commonly causes bloody diarrhea with low infectious dose and

person-to-person spread?

a. Salmonella enteritidis

b. Shigella spp.

c. Vibrio cholerae

d. Campylobacter jejuni

B

A key virulence factor of Bordetella pertussis is:

a. Vi capsule

b. Pertussis toxin

c. Protein A

d. Coagulase

B

Which lab finding is most suggestive of Legionella pneumonia?

a. High sodium (hypernatremia)

b. Hyponatremia

c. High eosinophils

d. Severe neutropenia in all cases

B

Legionella is best detected by:

a. Gram stain of sputum always shows many organisms

b. Urinary antigen test (for L. pneumophila serogroup 1)

c. Latex agglutination for stool antigen

d. KOH mount of sputum

B

Which statement is TRUE about Pseudomonas aeruginosa?

a. It is oxidase negative

b. It produces blue-green pigment (pyocyanin)

c. It is a strict anaerobe

d. It is always susceptible to ampicillin

B

Which organism is most associated with otitis media in children (among these)?

a. Moraxella catarrhalis

b. Treponema pallidum

c. Bacillus anthracis

d. Leptospira interrogans

A

Haemophilus influenzae requires which factors for growth?

a. Factor V only

b. Factor X only

c. Factors X and V

d. No special factors

C

Diphtheria toxin acts by:

a. Inhibiting EF-2 protein synthesis

b. Opening chloride channels

c. Blocking GABA release

d. Activating adenylate cyclase

A

Bacillus anthracis is characterized by:

a. Motile organism

b. Polypeptide (D-glutamate) capsule

c. Terminal spores "drumstick"

d. Oxidase positive diplococcus

B

Clostridium perfringens causes gas gangrene mainly through:

a. Alpha toxin (lecithinase)

b. Pertussis toxin

c. Heat-labile enterotoxin binding GM1

d. Endotoxin only

A

Most common cause of pseudomembranous colitis:

a. C. tetani

b. C. difficile

c. C. botulinum

d. C. perfringens

B

Botulinum toxin causes:

a. Spastic paralysis

b. Flaccid paralysis due to blockade of acetylcholine release

c. Hemorrhagic rash

d. Demyelination

B

Which statement is TRUE about influenza virus?

a. It is a non-segmented +ssRNA virus

b. Antigenic shift occurs only in influenza C

c. It has segmented −ssRNA genome

d. It is a DNA virus

C

The main target of neutralizing antibodies in influenza is:

a. Matrix protein M1

b. Hemagglutinin (HA)

c. Nucleoprotein (NP)

d. Polymerase PB2

B

HSV establishes latency mainly in:

a. Hepatocytes

b. Dorsal root/trigeminal ganglia

c. Red blood cells

d. Neutrophils

B

VZV primary infection typically causes:

a. Shingles

b. Chickenpox (varicella)

c. Kaposi sarcoma

d. Fifth disease

B

CMV infection is most concerning in:

a. Healthy children only

b. Immunocompromised and congenital infection

c. Only elderly with arthritis

d. People after eating seafood

B

EBV infects mainly:

a. T cells

b. B cells via CD21

c. Neutrophils

d. Erythrocytes

B

HPV causes cancer mainly by:

a. Integrating and expressing E6/E7 that inactivate p53/Rb

b. Producing endotoxin

c. Destroying cilia with exotoxin

d. Forming biofilm in lungs

A

HAV is transmitted mainly by:

a. Fecal-oral route

b. Sexual blood exposure only

c. Tick bite

d. Aerosols only

A

HBV is best described as:

a. Enveloped DNA virus with reverse transcriptase

b. Non-enveloped RNA virus

c. Enveloped −ssRNA virus

d. dsRNA virus

A

HEV infection is particularly severe in:

a. Children

b. Pregnant women (especially 3rd trimester)

c. People with asplenia only

d. People after vaccination

B

HCV genome is:

a. dsDNA

b. +ssRNA

c. −ssRNA segmented

d. dsRNA

B

Confirmatory test for active HCV infection is:

a. Anti-HCV IgG

b. HCV RNA (PCR)

c. HCV IgM

d. HCV culture routinely

B

HIV is:

a. DNA virus

b. Retrovirus with reverse transcriptase

c. Prion

d. Bacterium

B

Classic "window period" issue in early HIV infection relates to:

a. PCR negative, antibody positive

b. Antibody negative, viral RNA positive

c. Both always negative

d. Only p24 becomes negative forever

B

Prion diseases are caused by:

a. RNA viruses

b. Misfolded proteins without nucleic acids

c. Protozoa invading neurons

d. Helminths in CSF

B

Rabies virus is:

a. Orthomyxovirus

b. Rhabdovirus

c. Reovirus

d. Paramyxovirus

B

Rotavirus is:

a. dsRNA segmented virus

b. −ssRNA non-segmented

c. +ssRNA enveloped virus

d. DNA virus

A

West Nile virus is transmitted mainly by:

a. Mosquitoes

b. Ticks

c. Sexual contact

d. Fecal-oral route

A

Dengue severe disease is associated with:

a. Hemorrhagic manifestations and plasma leakage

b. Spastic paralysis

c. Chronic hepatitis

d. Pseudomembranous colitis

A

Naegleria fowleri infection is typically acquired by:

a. Undercooked pork

b. Nasal exposure to warm freshwater with amoebae

c. Cat feces ingestion

d. Tick bite

B

Toxoplasma gondii classic source is:

a. Cat feces (oocysts) or undercooked meat (tissue cysts)

b. Raw milk only

c. Mosquito bite

d. Contaminated IV fluids only

A

Trypanosoma brucei is transmitted by:

a. Tsetse fly

b. Triatomine bug

c. Sandfly

d. Mosquito

A

Treponema pallidum is best diagnosed in early primary chancre by:

a. Culture on blood agar

b. Dark-field microscopy / direct detection (where available)

c. Widal test

d. Stool antigen

B

A classic feature of secondary syphilis is:

a. Painful vesicles on dermatomes only

b. Diffuse rash including palms/soles

c. Pseudomembrane in throat

d. Gray "rice-water" stools

B