What is the primary mode of transmission for tetanus?
- A. Ingestion of contaminated food
- B. Inhalation of droplets
- C. Contaminated wounds
- D. Direct physical contact
Correct Answer: C
Rationale: The correct answer is C: Contaminated wounds. Tetanus is caused by the bacterium Clostridium tetani, which enters the body through breaks in the skin such as wounds or cuts. The bacteria produce a toxin that affects the nervous system, leading to muscle stiffness and spasms. Ingestion of contaminated food (choice A) is not a mode of transmission for tetanus. Inhalation of droplets (choice B) is more relevant for respiratory infections. Direct physical contact (choice D) is not the primary mode of transmission for tetanus as the bacteria need a portal of entry such as a wound to cause infection.
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Which of the following is a feature of Gram-negative bacteria?
- A. Thick peptidoglycan layer
- B. Outer membrane with lipopolysaccharides
- C. Presence of teichoic acids
- D. Absence of a cell wall
Correct Answer: B
Rationale: The correct answer is B: Outer membrane with lipopolysaccharides. Gram-negative bacteria have an outer membrane containing lipopolysaccharides (LPS), which are important in pathogenesis and immune response. This feature is unique to Gram-negative bacteria, distinguishing them from Gram-positive bacteria (choice A). Teichoic acids (choice C) are found in the cell walls of Gram-positive bacteria, not Gram-negative. The statement in choice D, absence of a cell wall, is incorrect as all bacteria have a cell wall, although the composition may vary between Gram-negative and Gram-positive bacteria.
Which of the following pathogens has the widest infectious spectrum
- A. Anthrax bacillus
- B. mumps virus
- C. the causative agent of gonorrhea
- D. the rabies virus
Correct Answer: A
Rationale: The correct answer is A, Anthrax bacillus, because it has the widest infectious spectrum among the options provided. Anthrax bacillus can infect a wide range of hosts, including humans and various animals. It is known for its ability to survive in different environments and cause disease through various routes of exposure. In contrast, choices B, C, and D have more limited infectious spectra. Mumps virus primarily infects humans, the causative agent of gonorrhea mainly affects humans through sexual contact, and the rabies virus typically infects mammals through bites from infected animals. Therefore, Anthrax bacillus is the correct choice due to its broader range of hosts and modes of transmission compared to the other options.
Which of the following antibodies indicates acute measles infection
- A. Anti-mumps IgM
- B. Anti-rubella IgM
- C. Anti-measles IgM
- D. Anti-CMV IgM
Correct Answer: C
Rationale: The correct answer is C: Anti-measles IgM. During acute measles infection, the body produces IgM antibodies specific to the measles virus. This indicates a recent or current infection.
A: Anti-mumps IgM and B: Anti-rubella IgM are specific to mumps and rubella viruses, respectively, not measles.
D: Anti-CMV IgM is specific to cytomegalovirus, not measles.
In summary, choice C is correct because Anti-measles IgM is the specific antibody indicating acute measles infection, while the other choices are antibodies related to different viruses.
Poxviruses are the largest viruses, almost visible on a light microscope.
- A. TRUE
- B. FALSE
- C. Not Sure
- D. Partially
Correct Answer: A
Rationale: The correct answer is A: TRUE. Poxviruses are indeed the largest viruses, ranging from 200-450 nm in size, which is close to the resolution limit of a light microscope. This makes them almost visible under a light microscope. The other choices are incorrect because poxviruses are not smaller or uncertain in size (choices B and C), nor are they partially visible - they are almost visible due to their relatively large size.
Microscopy of a wound abscess revealed Gram-negative rods producing blue-green pigment with a distinctive odor of jasmine. What is the likely causative agent?
- A. Pseudomonas aeruginosa
- B. Proteus vulgaris
- C. Escherichia coli
- D. Klebsiella pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. Pseudomonas aeruginosa is known for producing a blue-green pigment called pyocyanin, which gives the characteristic color seen in the wound abscess. The distinctive odor of jasmine is also a key feature of Pseudomonas aeruginosa. Proteus vulgaris (B) and Klebsiella pneumoniae (D) do not produce blue-green pigment or have a jasmine-like odor. Escherichia coli (C) typically does not produce blue-green pigment or have a jasmine-like odor.