Nokea
Gram-positive cocci arranged in chains were found in a wound smear. The bacteria were catalase-negative and beta-hemolytic on blood agar. What is the causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Enterococcus faecalis
- D. Micrococcus luteus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes. This bacterium fits all the given characteristics: Gram-positive cocci arranged in chains, catalase-negative, and beta-hemolytic on blood agar. Streptococcus pyogenes is known for causing skin and soft tissue infections. Staphylococcus aureus (B) is catalase-positive and typically forms clusters, not chains. Enterococcus faecalis (C) is catalase-negative but not beta-hemolytic. Micrococcus luteus (D) is catalase-positive and not typically associated with wound infections.
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Which bacteria is responsible for causing cholera?
- A. Shigella dysenteriae
- B. Vibrio cholerae
- C. Salmonella enterica
- D. Clostridium perfringens
Correct Answer: B
Rationale: The correct answer is B: Vibrio cholerae. Cholera is caused by this specific bacterium due to its production of cholera toxin, leading to severe watery diarrhea. Shigella dysenteriae causes dysentery, Salmonella enterica causes salmonellosis, and Clostridium perfringens causes food poisoning, none of which present with the characteristic symptoms of cholera.
The correct descending order of taxonomic categories is
- A. species, domain, phylum, kingdom, order, division, class, genus
- B. domain, kingdom, phylum, class, family, order, genus, species
- C. domain, kingdom, phylum, class, order, family, genus, species
- D. kingdom, domain, phylum, order, class, family, genus, species
Correct Answer: C
Rationale: The correct descending order of taxonomic categories is domain, kingdom, phylum, class, order, family, genus, species. This hierarchical classification system helps organize and categorize living organisms based on their shared characteristics and evolutionary relationships.
Explanation:
- Domain is the broadest category, representing the highest level of classification.
- Kingdom further divides organisms into major groups based on similar characteristics.
- Phylum, class, order, family, and genus successively narrow down the classification based on more specific shared characteristics.
- Species is the most specific category, representing individual organisms capable of interbreeding.
Summary of other choices:
A: Incorrect as it has the incorrect order of phylum, kingdom, and division.
B: Incorrect as it has the incorrect order of family and species.
D: Incorrect as it has the incorrect order of domain, kingdom, and class.
Rotaviruses:
- A. The NSP4 nonstructural protein of rotaviruses acts in a toxic-like manner.
- B. Disease can be significant in infants and adults
- C. Cannot survive the acidic environment in the stomach
- D. Prevents the absorption of water, but do not cause a net secretion of water and loss of ions
Correct Answer: A
Rationale: The correct answer is A because the NSP4 nonstructural protein of rotaviruses indeed acts in a toxic-like manner by disrupting calcium homeostasis, leading to diarrhea. Choice B is incorrect as rotaviruses can cause significant disease in infants, but not typically in adults. Choice C is incorrect as rotaviruses are resistant to stomach acid. Choice D is incorrect as rotaviruses cause a net secretion of water and loss of ions, contributing to diarrhea.
Which of the statements is false:
- A. Spirochaetes are bacilli
- B. Diplococci possess spherical shape
- C. In rod-shaped bacteria one of the diameters is bigger
- D. Coccobacilli are a type of rod-shaped bacteria
Correct Answer: A
Rationale: The correct answer is A because spirochaetes are not bacilli; they are spiral-shaped bacteria. Bacilli are rod-shaped bacteria, making statement A false. Statement B is true as diplococci are spherical bacteria occurring in pairs. Statement C is true as rod-shaped bacteria have one diameter longer than the other. Statement D is true as coccobacilli are short, oval-shaped bacteria resembling cocci and rods. In summary, spirochaetes are spiral-shaped, not bacilli, making statement A false.
For prevention of tuberculosis is used
- A. specific anti-tuberculosis serum
- B. BCG
- C. DTP
- D. PPD
Correct Answer: B
Rationale: The correct answer is B: BCG. Bacille Calmette-Guérin (BCG) vaccine is used for the prevention of tuberculosis. BCG is a live attenuated strain of Mycobacterium bovis that helps the immune system recognize and fight off tuberculosis bacteria. Specific anti-tuberculosis serum (A) is not used for prevention but for treatment. DTP (C) stands for diphtheria, tetanus, and pertussis vaccine, not specific for tuberculosis prevention. PPD (D) is a tuberculin skin test used for diagnosis, not prevention. Thus, BCG is the correct choice for tuberculosis prevention.