Weekly Year 2: Microbiology Exam - June 5, 2026 (Section A:

Question 1

A paroxysm is a sudden, uncontrolled fit of coughing and is characteristic of which of the following conditions?

Accepted Answer

Pertussis (Whooping Cough) — A paroxysm, defined as a sudden, uncontrolled fit of coughing, is a hallmark symptom of pertussis (whooping cough).

Question 2

To treat patients who have ingested botulism toxin, large doses of which of the following must be administered?

Accepted Answer

Antitoxin — The primary treatment for botulism toxin ingestion is the administration of antitoxin, which neutralizes the toxin.

Question 3

The organism Clostridium perfringens multiplies in foods only under which of the following conditions?

Accepted Answer

Anaerobic — Clostridium perfringens is an obligate anaerobe, meaning it can only multiply and produce toxins in the absence of oxygen.

Question 4

Woolsorter's disease applies to which form of which of the following infections?

Accepted Answer

Inhalation form of anthrax — Woolsorter's disease is a historical term referring to the inhalation form of anthrax, which was a risk for workers handling animal wool.

Question 5

Ophthalmia neonatorum is most commonly associated with which two sexually transmitted infections?

Accepted Answer

Chlamydia and Gonorrhea — Ophthalmia neonatorum, an infection of the newborn's eyes, is most commonly caused by Chlamydia trachomatis and Neisseria gonorrhoeae.

Question 6

Which of the following microorganisms was the first to satisfy Koch's postulates in the late 19th century?

Accepted Answer

Vibrio cholerae — Robert Koch successfully applied his postulates to identify Vibrio cholerae as the causative agent of cholera.

Question 7

Which of the following best describes the mechanism of action of diphtheria toxin?

Accepted Answer

It inhibits protein synthesis by inactivating elongation factor-2 (EF-2). — Diphtheria toxin is an A-B toxin that ADP-ribosylates elongation factor-2 (EF-2), thereby inhibiting protein synthesis and leading to cell death.

Question 8

The identification of bacteria by serological tests is based on the presence of specific antigens. Which of the following bacterial components is least likely to contain useful antigens for serological identification?

Accepted Answer

Peptidoglycan — While peptidoglycan is a crucial component of the bacterial cell wall, its antigenic variability is generally lower compared to surface structures like capsules, LPS, and flagella, making it less useful for specific serological identification.

Question 9

Which of the following species of Pasteurella has been associated with infection of the female genital tract and newborn?

Accepted Answer

Pasteurella multocida — Pasteurella multocida is known to cause infections in humans, including those of the genital tract and can be transmitted to newborns.

Question 10

Which of the following diseases is best diagnosed by serologic means?

Accepted Answer

Lyme disease — Lyme disease is often diagnosed serologically by detecting antibodies against Borrelia burgdorferi, as direct detection of the organism can be difficult.

Question 11

Which of the following is NOT a most important cause of acute bacterial meningitis?

Accepted Answer

Escherichia coli — While E. coli can cause meningitis, particularly in neonates, it is not considered one of the most important causes of acute bacterial meningitis in the general adult population, which is dominated by S. pneumoniae and N. meningitidis, with H. influenzae type b being a significant cause in unvaccinated children.

Question 12

Which of the following is most likely to be associated with the formation of a bacterial biofilm?

Accepted Answer

Bacteria attached to a medical implant — Biofilms are structured communities of bacteria encased in a self-produced matrix and are commonly found attached to surfaces, especially medical implants, where they are resistant to antibiotics and host defenses.

Question 13

Which one of the following is a potential complication of streptococcus pharyngitis?

Accepted Answer

Rheumatic fever — Rheumatic fever is a serious inflammatory condition that can develop as a complication of untreated or inadequately treated streptococcal pharyngitis (strep throat).

Question 14

The presence of a pseudomembrane in the throat is a result of infection by which of the following organisms?

Accepted Answer

Corynebacterium diphtheriae — A characteristic pseudomembrane, a grayish-white membrane composed of fibrin, dead cells, and inflammatory cells, is a hallmark of diphtheria, caused by Corynebacterium diphtheriae.

Question 15

A paroxysm is a sudden, severe attack of coughing associated with which of the following conditions?

Accepted Answer

Pertussis (Whooping Cough) — A paroxysm, in the context of infectious diseases, refers to a sudden, severe attack of coughing, which is characteristic of pertussis.

Question 16

The Mantoux test is used to identify:

Accepted Answer

All of the above — The Mantoux test (tuberculin skin test) indicates prior exposure to Mycobacterium tuberculosis and can be positive in individuals with latent TB infection or active TB disease. Therefore, it helps identify exposure and potential infection.

Question 17

Which of the following bacterial species is the most common cause of 'typical' pneumonia?

Accepted Answer

Streptococcus pneumoniae — Streptococcus pneumoniae is considered the most common bacterial cause of community-acquired (typical) pneumonia.

Question 18

To treat patients who have ingested botulism toxin, large doses of which of the following must be administered?

Accepted Answer

Antitoxin — The primary treatment for botulism is the administration of antitoxin to neutralize the circulating botulinum toxin. Antibiotics are not effective against the toxin itself but may be used for wound botulism.

Question 19

The organism Clostridium perfringens multiplies in foods only under which of the following conditions?

Accepted Answer

Anaerobic — Clostridium perfringens is an obligate anaerobe and requires anaerobic conditions to multiply and produce its toxins in food.

Question 20

A spore-forming, motile rod that can cause foodborne illness in a diarrheal or emetic form is Bacillus:

Accepted Answer

Cereus — Bacillus cereus is a spore-forming bacterium known to cause food poisoning, with distinct diarrheal and emetic syndromes.

Question 21

Woolsorter's disease applies to the form of :

Accepted Answer

Inhalation; anthrax — Woolsorter's disease is an old term for the inhalation form of anthrax, which posed a significant risk to workers in the wool industry.

Question 22

Which one of the following describes the mode of action of tetanospasmin (tetanus toxin)?

Accepted Answer

It inhibits neurotransmitter release at inhibitory synapses in the spinal cord, leading to spastic paralysis. — Tetanospasmin acts in the central nervous system to inhibit the release of inhibitory neurotransmitters (GABA and glycine), resulting in uncontrolled muscle contraction and spastic paralysis.

Question 23

Salpingitis is associated with which of the following conditions and can lead to which of the following complications?

Accepted Answer

Chlamydia trachomatis infection; pelvic inflammatory disease — Salpingitis (inflammation of the fallopian tubes) is a common manifestation of pelvic inflammatory disease (PID), often caused by Chlamydia trachomatis and Neisseria gonorrhoeae, and can lead to infertility and ectopic pregnancy.

Question 24

Ophthalmia neonatorum is associated with which two STDs?

Accepted Answer

Gonorrhea and Chlamydia — Ophthalmia neonatorum, an infection of the newborn's eyes, is most commonly caused by Neisseria gonorrhoeae and Chlamydia trachomatis, which are sexually transmitted infections.

Question 25

Fish are the second intermediate hosts for which of the following parasites?

Accepted Answer

Clonorchis sinensis — Clonorchis sinensis (Chinese liver fluke) uses freshwater fish as its second intermediate host.

Question 26

Which of the following secretes defensive secretions to cause irritation on human skin?

Accepted Answer

Millipede — Millipedes secrete defensive chemicals, often quinones or cyanogenic compounds, which can cause irritation and discoloration of the skin.

Question 27

Holometabolous insects have:

Accepted Answer

Complete metamorphosis (egg, larva, pupa, adult) — Holometabolous insects undergo complete metamorphosis, which involves distinct larval and pupal stages before reaching the adult form.

Question 28

Which of the following transmits parasites that cause river blindness?

Accepted Answer

Blackfly — River blindness (onchocerciasis) is transmitted by the bite of infected blackflies (genus Simulium).

Question 29

Which insecticide targets GABA in its action?

Accepted Answer

Fipronil — Fipronil is a phenylpyrazole insecticide that acts by blocking GABA-gated chloride channels in insect nervous systems, leading to hyperexcitation and death.

Question 30

Presence of triatomine bugs could predispose the population to:

Accepted Answer

Chagas disease — Triatomine bugs (kissing bugs) are vectors for Trypanosoma cruzi, the parasite that causes Chagas disease.

Question 31

People living in forested areas are at a risk of:

Accepted Answer

Rocky Mountain Spotted Fever — Rocky Mountain Spotted Fever is transmitted by ticks, which are commonly found in forested and brushy areas.

Question 32

Which of the following insects are commonly found in Latin America?

Accepted Answer

All of the above — Aedes aegypti (vector for dengue, Zika, chikungunya), Anopheles mosquitoes (vector for malaria), and Triatomine bugs (vector for Chagas disease) are all commonly found in Latin America.

Question 33

Pruritus (itching) can be best diagnosed for:

Accepted Answer

All of the above — Pruritus is a symptom that can be caused by a wide range of conditions, including allergic reactions, parasitic infestations like scabies, and fungal infections. Therefore, a diagnosis of pruritus would involve investigating all these possibilities.

Question 34

If you found lice eggs (nits) in someone's clothing, what species would they most likely be from?

Accepted Answer

Pediculus humanus humanus (body louse) — Body lice (Pediculus humanus humanus) tend to lay their eggs (nits) on clothing and bedding, whereas head lice typically attach nits to hair shafts.

Question 35

Which of the following is the odd one out in terms of transmission mechanism?

Accepted Answer

Typhoid fever — Malaria, Lyme disease, and Chagas disease are all vector-borne diseases (mosquito, tick, and triatomine bug, respectively). Typhoid fever is primarily transmitted through contaminated food and water (fecal-oral route).

Question 36

Which one of the following is larviparous?

Accepted Answer

Drosophila melanogaster (fruit fly) — Larviparous is a term used to describe animals that give birth to larvae. Drosophila melanogaster, a common fruit fly, lays eggs from which larvae (maggots) hatch, and the adult fly is the mature form of the insect.

Weekly Year 2: Microbiology Exam - June 5, 2026 (Section A:

Questions, Answers & Explanations