Nokea
Which bacteria is commonly associated with urinary tract infections (UTIs)?
- A. Escherichia coli
- B. Clostridium botulinum
- C. Staphylococcus aureus
- D. Bacillus cereus
Correct Answer: A
Rationale: The correct answer is A: Escherichia coli. E. coli is commonly associated with UTIs due to its ability to colonize the urinary tract. It possesses adhesins that allow it to attach to the bladder wall, causing infection. E. coli is also a common inhabitant of the intestinal tract, making it easily able to migrate to the urinary system.
Explanation of incorrect choices:
B: Clostridium botulinum - This bacterium causes botulism, a rare foodborne illness, not UTIs.
C: Staphylococcus aureus - Often associated with skin infections and abscesses, not UTIs.
D: Bacillus cereus - Known for causing food poisoning, not UTIs.
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A man died from an acute infectious disease accompanied by fever, jaundice, haemorrhagic rash on the skin and mucous membranes as well as by acute renal insufficiency. Histological examination of renal tissue (stained by Romanovsky-Giemsa method) revealed some convoluted bacteria looking like C and S letters. What bacteria were revealed?
- A. Leptospira
- B. Treponema
- C. Spirilla
- D. Borrelia
Correct Answer: A
Rationale: The correct answer is A: Leptospira. The key features pointing to Leptospira are the presence of convoluted bacteria resembling C and S letters, which is characteristic of Leptospira species. Leptospirosis presents with fever, jaundice, haemorrhagic rash, and acute renal insufficiency. The other choices (B: Treponema, C: Spirilla, D: Borrelia) do not match the histological description or the clinical presentation of the case. Treponema is associated with syphilis, Spirilla with genus Spirochaeta, and Borrelia with Lyme disease, none of which match the given scenario.
Cell mediated immunity has a leading role in:
- A. Infections with facultative and obligate intracellular pathogens
- B. Infections with extracellular pathogens
- C. Type 1 hypersensitivity reactions
- D. Toxin mediated infections
Correct Answer: A
Rationale: Cell-mediated immunity plays a crucial role in combating infections with intracellular pathogens by activating T cells to directly kill infected cells. Facultative and obligate intracellular pathogens, such as viruses and some bacteria, require cell-mediated immunity for effective clearance. Option A is correct due to the specificity of this immune response. Choices B, C, and D are incorrect as they are primarily associated with humoral immunity involving antibodies and not T cell responses against intracellular pathogens.
A patient with a sore throat had a throat smear revealing Gram-positive cocci in pairs. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes.
Rationale:
1. Gram-positive cocci in pairs suggest Streptococcus species.
2. Catalase-negative rules out Staphylococcus.
3. Beta-hemolytic indicates Streptococcus pyogenes due to its beta-hemolytic properties.
Summary:
B: Streptococcus pneumoniae is catalase-negative but not beta-hemolytic.
C: Enterococcus faecalis is not typically beta-hemolytic.
D: Staphylococcus aureus is catalase-positive and not typically in pairs.
Which scientist is most responsible for ending the controversy about spontaneous generation?
- A. John Needham
- B. Joseph Lister
- C. Louis Pasteur
- D. Robert Koch
Correct Answer: C
Rationale: The correct answer is C: Louis Pasteur. He conducted experiments that definitively disproved the theory of spontaneous generation through his famous swan-neck flask experiment. By showing that microorganisms only appeared in the broth when exposed to air, Pasteur demonstrated that they did not arise spontaneously. John Needham's experiments were inconclusive, Joseph Lister is known for his contributions to antiseptic surgery, and Robert Koch is credited with developing Koch's postulates for identifying the causative agents of diseases, but neither of them directly contributed to ending the controversy about spontaneous generation.
Which of these viruses is a laboratory product?
- A. Monkeypox
- B. Variola
- C. Vaccinia
- D. Cowpox
Correct Answer: C
Rationale: Rationale:
1. Vaccinia is a laboratory product used in smallpox vaccination.
2. Variola is the virus that causes smallpox, not a laboratory product.
3. Monkeypox is a naturally occurring virus, not a laboratory product.
4. Cowpox can be found in nature and is used in vaccine production, but it is not a laboratory product like Vaccinia.