Bacteria capable of growing at low temperatures are called:

Correct Answer: C

Rationale: The correct answer is C: psychrophiles. Psychrophiles are bacteria that can grow at low temperatures, typically below 20°C. This is because they have adapted to survive and thrive in cold environments. Mesophiles (A) grow best at moderate temperatures, thermophiles (B) thrive in high temperatures, and halophiles (D) prefer high salt concentrations. Psychrophiles are specifically adapted to cold temperatures, making them the correct choice in this scenario.

Correct Answer: A

Rationale: The correct answer is A: Borrelia burgdorferi. This bacterium is associated with Lyme disease, a tick-borne illness. Borrelia burgdorferi is transmitted to humans through the bite of infected black-legged ticks. It causes a range of symptoms, including fever, rash, joint pain, and neurological problems. Summary: B: Clostridium botulinum is associated with botulism, a serious illness caused by a toxin produced by this bacterium. C: Escherichia coli is a common bacterium found in the intestines of humans and animals, some strains can cause food poisoning. D: Streptococcus pneumoniae is a bacterium that can cause pneumonia and other respiratory infections, but not Lyme disease.

Correct Answer: A

Rationale: The correct answer is A: Mycobacterium tuberculosis. 1. Bright-red acid-resistant bacilli indicate the presence of mycolic acids in the cell wall, characteristic of Mycobacterium species. 2. Found in groups or singularly suggests the clumping nature of acid-fast bacilli. 3. Growth appearing after 10-15 days on nutrient media is consistent with the slow growth rate of Mycobacterium tuberculosis. 4. Yersinia pseudotuberculosis (B) and Klebsiella rhinoscleromatis (D) are not acid-fast bacilli and do not match the growth characteristics described. 5. Histoplasma dubrosii (C) is a fungus, not a bacterium, and does not exhibit acid-fast staining or the described growth pattern.

Correct Answer: A

Rationale: Pili in bacteria are responsible for conjugation, allowing the transfer of genetic material between cells. They form a bridge between donor and recipient cells, facilitating the exchange of DNA. Flagella are for movement, capsules for protection, and ribosomes for protein synthesis. Pili is the only structure directly involved in genetic material exchange.

Correct Answer: A

Rationale: Step 1: Treponema pallidum is a spirochete bacterium known to cause syphilis. Step 2: It is sexually transmitted and can cause various stages of disease. Step 3: Neisseria gonorrhoeae causes gonorrhea, not syphilis. Step 4: Chlamydia trachomatis causes chlamydia, not syphilis. Step 5: Escherichia coli is a common gut bacterium and not responsible for syphilis. Treponema pallidum is the correct answer as it is the specific bacterium known to cause syphilis.

Correct Answer: C

Rationale: The correct answer is C: IgG. IgG is the only antibody that can cross the placenta due to its small size and unique structure, allowing it to provide passive immunity to the fetus. IgA is mainly found in mucosal secretions, IgM is too large to cross the placental barrier, and IgD plays a role in B cell activation but is not involved in placental transfer.

Correct Answer: A

Rationale: Step 1: Clostridia of tetanus, botulism, anaerobic gas infection are spore-forming bacteria. Step 2: Spores are resistant structures that allow bacteria to survive in harsh conditions. Step 3: Feces contain these spore-forming bacteria due to contamination. Step 4: When feces are deposited on soil, the spores of these bacteria enter the soil. Step 5: Spores can remain dormant in soil for long periods. Summary: Choice A is correct as spore-forming bacteria enter soil through feces, which act as a source of contamination. Choices B, C, and D are incorrect as they do not involve the direct introduction of spores into soil like feces do.

Correct Answer: D

Rationale: The correct answer is D: Adenovirus. Adenovirus commonly causes acute febrile pharyngitis and pharyngoconjunctival fever. Adenovirus is known to cause respiratory infections and can present with symptoms such as sore throat, fever, and conjunctivitis. VZV (Varicella-Zoster Virus) causes chickenpox and shingles, not these specific symptoms. Measles virus causes a systemic illness with characteristic rash, not typically pharyngitis. Rubella virus causes a mild febrile illness with rash, but not pharyngitis. Therefore, based on the clinical presentation described, adenovirus is the most likely cause.

Correct Answer: A

Rationale: The correct answer is A: Rifampicin. Rifampicin is known to cause red discoloration of bodily fluids, including tears and urine, due to its side effect of harmless color changes. Benzylpenicillins (B and C) and Biseptol-480 do not typically cause such discoloration. Rifampicin's mechanism of action involves binding to bacterial RNA polymerase, leading to inhibition of RNA synthesis, which is unrelated to the mechanism of the other drugs. Thus, based on the unique side effect profile of Rifampicin and its mechanism of action, it is the most likely drug causing red tears and urine in this scenario.