Nokea
For shigella is true:
- A. They produce hydrogen sulfide
- B. They ferment lactose
- C. They are nonmotile
- D. All of them are mannitol positive
Correct Answer: C
Rationale: Step-by-step rationale:
1. Shigella is a nonmotile bacterium.
2. This lack of motility is a key characteristic used to differentiate it from other enteric bacteria.
3. Nonmotile nature of Shigella helps it to cause infections by invading the intestinal epithelial cells.
4. Therefore, choice C is correct as Shigella is indeed nonmotile.
Summary:
A: Incorrect - Shigella does not produce hydrogen sulfide.
B: Incorrect - Shigella does not ferment lactose.
D: Incorrect - Shigella is not mannitol positive.
You may also like to solve these questions
Which one of the following statements about Rickettsiae is true?
- A. They do not form spores, capsules and flagella
- B. They have slim glycocalyx layer
- C. They have bipolar fimbriae
- D. All of the above
Correct Answer: D
Rationale: Rationale:
1. Rickettsiae are obligate intracellular bacteria, hence they do not form spores, capsules, or flagella.
2. They have a slim glycocalyx layer, aiding in attachment to host cells.
3. Bipolar fimbriae are structures that help in adhesion to host cells.
Therefore, all statements (A, B, and C) are true for Rickettsiae, making option D the correct answer. Other choices are incorrect as they do not accurately describe the characteristics of Rickettsiae.
A smear from a sore throat revealed rod-shaped bacteria with polar granules. What is the most likely causative agent?
- A. Corynebacterium diphtheriae
- B. Streptococcus pneumoniae
- C. Haemophilus influenzae
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The most likely causative agent is Corynebacterium diphtheriae. Step 1: Presence of rod-shaped bacteria indicates a bacillus. Step 2: Polar granules suggest metachromatic granules seen in C. diphtheriae. Step 3: C. diphtheriae causes diphtheria, which presents with sore throat. Summary: B is incorrect as S. pneumoniae is a cocci, not a bacillus. C is incorrect as H. influenzae is a pleomorphic coccobacillus. D is incorrect as K. pneumoniae is a large, encapsulated bacillus.
The establishment and further spreading of an infectious disease within a new population is a process called:
- A. emergence
- B. adoption
- C. inclusion
- D. appearance
Correct Answer: A
Rationale: The correct answer is A: emergence. The term emergence refers to the process of a new infectious disease appearing and spreading within a population. It signifies the initial introduction and establishment of the disease in the new population.
Explanation for other choices:
B: Adoption does not accurately describe the process of a disease spreading within a new population.
C: Inclusion is not a term commonly used to describe the spread of infectious diseases.
D: Appearance is too vague and does not capture the complexity of the process of establishment and spreading of an infectious disease.
A wound infection culture revealed Gram-positive cocci in clusters. The bacteria were catalase-positive and coagulase-positive. What is the most likely causative agent?
- A. Staphylococcus aureus
- B. Staphylococcus epidermidis
- C. Streptococcus pyogenes
- D. Enterococcus faecalis
Correct Answer: A
Rationale: The correct answer is A: Staphylococcus aureus. This bacterium is characterized by Gram-positive cocci in clusters, catalase-positive, and coagulase-positive. Staphylococcus aureus is a common pathogen causing wound infections due to its ability to produce toxins and enzymes. Staphylococcus epidermidis (B) is catalase-positive but coagulase-negative, making it less likely to cause infections. Streptococcus pyogenes (C) is catalase-negative and typically causes streptococcal infections, not wound infections. Enterococcus faecalis (D) is catalase-negative and typically associated with urinary tract infections. Thus, Staphylococcus aureus is the most likely causative agent based on the given characteristics.
There is/are __________ level(s) of biosafety depending on the organisms handled.
- A. 1
- B. 2
- C. 3
- D. 4
Correct Answer: D
Rationale: The correct answer is D (4) because biosafety levels range from 1 to 4, each corresponding to the level of containment required when handling different types of organisms. BSL-1 is for low-risk agents, while BSL-4 is for dangerous pathogens. Choice A (1) is incorrect as there are multiple levels, not just one. Choice B (2) and C (3) are incorrect as they do not account for all the levels of biosafety required for handling various organisms. Therefore, D is the correct answer as it encompasses the full range of biosafety levels.