KMU Past Paper Practice

Question:

A microbiology laboratory isolates a large gram-positive rod from the skin lesion of an animal-hide worker. The organism forms spores, is non-motile and possesses an unusual capsule composed of polypeptide rather than polysaccharide. Which additional finding would best support identification of this organism?

Correct Answer:
Production of protective antigen with two enzymatic toxin factors

Explanation: Bacillus anthracis has a poly-D-glutamic acid capsule and produces protective antigen, edema factor and lethal factor, which together account for major toxin-mediated manifestations.

Question:

A patient develops severe pain and swelling around a traumatic wound. Examination shows rapidly progressive muscle destruction with gas in the tissues. Microscopy of wound material demonstrates large gram-positive rods. Which organism is the most likely cause?

Correct Answer:
Clostridium perfringens

Explanation: Clostridium perfringens can produce rapidly progressive toxin-mediated myonecrosis. Anaerobic growth in damaged tissue also contributes to characteristic gas formation.

Question:

An elderly hospitalized patient develops profuse diarrhea after receiving a prolonged course of broad-spectrum antibiotics. The major pathological process is toxin-mediated injury to the colonic mucosa. Which organism best fits this presentation?

Correct Answer:
Clostridioides difficile

Explanation: Antibiotic disruption of normal intestinal flora permits toxigenic C. difficile to proliferate, with its toxins producing inflammatory colonic injury and antibiotic-associated colitis.

Question:

A child with suspected respiratory diphtheria has a throat specimen sent to the laboratory. Culture identifies Corynebacterium diphtheriae. Which additional information is most important for establishing the organism’s ability to produce classical severe disease?

Correct Answer:
Demonstration of toxin-producing capacity

Explanation: Isolation of C. diphtheriae alone does not establish toxigenicity. Classical diphtheria depends on production of diphtheria toxin, so toxin-producing capacity is the key additional property.

Question:

A fish handler develops a localized painful violaceous lesion on a finger after a small cut sustained at work. He has no black eschar, generalized spasms or pharyngeal disease. Which organism should be considered first?

Correct Answer:
Erysipelothrix rhusiopathiae

Explanation: E. rhusiopathiae is associated with occupational exposure to fish and animal products and can enter through damaged skin to produce localized erysipeloid.

Question:

A woman living on a dairy farm has no symptoms but asks how to reduce her family’s risk of acquiring brucellosis. They regularly consume milk produced by their own livestock. Which change would most directly interrupt food-borne transmission?

Correct Answer:
Use only pasteurized dairy products

Explanation: Brucella can be transmitted through contaminated unpasteurized milk and dairy products. Pasteurization directly interrupts this important route of human infection.

Question:

A slaughterhouse employee presents with prolonged fever, fatigue and hepatosplenomegaly. Brucellosis is suspected. Which diagnostic approach is most appropriate for supporting the diagnosis in this clinical setting?

Correct Answer:
Blood culture with appropriate serological testing

Explanation: Brucella may be isolated from blood, while serology can support diagnosis when interpreted with the characteristic exposure history and clinical findings.

Question:

During investigation of a zoonotic disease outbreak, health workers find infected rodents and abundant fleas around human dwellings. Which intervention is most directly aimed at breaking the vector component of this transmission cycle?

Correct Answer:
Control of flea populations associated with rodents

Explanation: Yersinia pestis is maintained in a rodent–flea cycle. Flea control directly targets the vector responsible for transmitting infection from infected rodents to humans.

Question:

A patient with suspected plague presents with fever and a markedly enlarged tender axillary lymph node. The laboratory is asked to obtain a specimen that most directly samples the involved site. Which specimen is most appropriate?

Correct Answer:
Bubo aspirate

Explanation: In suspected bubonic plague, aspirate from the affected bubo directly samples the major site of disease and can be examined and cultured for Yersinia pestis.

Question:

A veterinary laboratory worker has repeated occupational contact with animals that may carry rabies virus. He has not sustained a recent bite. Which preventive approach is most appropriate before a future exposure occurs?

Correct Answer:
Pre-exposure rabies vaccination

Explanation: Pre-exposure vaccination is intended for people with continuing predictable rabies risk. It establishes active immunity before an exposure occurs.

Question:

A man bitten by a rabid animal receives appropriate prophylaxis before developing neurological symptoms. Why is early preventive intervention particularly important in rabies?

Correct Answer:
The virus must be controlled before significant neural spread to the CNS

Explanation: Rabies virus enters peripheral nerves and travels toward the CNS. Post-exposure prophylaxis is therefore designed to prevent progression before neurological disease develops.

Question:

Two workers are exposed to potentially contaminated animal material. One develops a localized skin lesion, whereas the other develops severe respiratory disease after inhaling spores. Which principle best explains the different clinical forms of anthrax?

Correct Answer:
Clinical form is strongly influenced by the route of spore entry

Explanation: B. anthracis can cause cutaneous, inhalational or gastrointestinal disease depending largely on how spores enter the host.

Question:

A man sustains a superficial clean wound while gardening. His colleague sustains a deep contaminated wound containing devitalized tissue. Why does the second wound carry a greater risk of tetanus?

Correct Answer:
It provides anaerobic conditions favorable for spore germination

Explanation: Deep devitalized tissue can create a low-oxygen environment that favors germination of C. tetani spores and subsequent production of tetanospasmin.

Question:

A patient recovers from clinically diagnosed tetanus. During counseling, he asks whether having had the disease means that future vaccination is unnecessary. Which principle best guides prevention of another episode?

Correct Answer:
Active immunization remains necessary for reliable protection

Explanation: Clinical tetanus does not provide dependable protective immunity. Tetanus toxoid-containing vaccination remains the basis of future active protection.

Question:

Several children in a crowded residential institution develop intense nocturnal itching. Treatment is given to symptomatic children, but new cases continue to appear. Which additional intervention is most important for interrupting transmission?

Correct Answer:
Coordinate management of relevant close contacts and recently used fabrics

Explanation: Scabies transmission can persist through untreated close contacts and contaminated recently used clothing or bedding, particularly in crowded institutional settings.

Question:

Two patients with leprosy are compared. Patient X has a few localized lesions with a low organism burden, while patient Y has widespread symmetrical lesions containing numerous organisms. Which factor best explains this difference in disease expression?

Correct Answer:
Strength of host cell-mediated immune response

Explanation: The leprosy spectrum reflects cell-mediated immunity: stronger immunity restricts organisms and lesions, whereas poor cellular immunity permits widespread bacillary multiplication.

Question:

A community program aims to reduce both transmission and disability from leprosy. Which strategy best addresses these two goals simultaneously?

Correct Answer:
Early detection and effective treatment of affected individuals

Explanation: Early diagnosis and effective treatment reduce continued transmission while limiting progressive peripheral nerve damage and subsequent disability.

Question:

An adult from a community where trachoma is endemic has inward turning of the upper eyelid with eyelashes rubbing against the cornea. Which preceding pathological process most directly produced this deformity?

Correct Answer:
Repeated conjunctival inflammation followed by fibrosis

Explanation: Repeated Chlamydia trachomatis infection causes chronic conjunctival inflammation and scarring; contraction of this scar tissue can produce entropion and subsequent trichiasis.

Question:

A public-health team implements the SAFE strategy in a community with endemic trachoma. A patient already has trichiasis and is at risk of progressive corneal injury. Which component specifically addresses this established mechanical complication?

Correct Answer:
Surgical correction of trichiasis

Explanation: The “S” in SAFE represents surgery for trichiasis. It addresses inward-directed eyelashes that mechanically damage the cornea and threaten vision.

Question:

Three patients are being investigated for infections in this topic. Patient 1 has suspected systemic anthrax, patient 2 has suspected Listeria meningitis, and patient 3 has suspected bubonic plague. Which set of specimens is most appropriately matched to these conditions?

Correct Answer:
Blood → cerebrospinal fluid → bubo aspirate

Explanation: Blood is appropriate in systemic anthrax, cerebrospinal fluid can diagnose Listeria CNS infection, and aspirate from an enlarged bubo directly samples bubonic plague.