Nokea
The number of new cases of a disease over a certain period of time compared with the general healthy population is referred to as:
- A. incidence
- B. prevalence
- C. virulence
- D. mortality
Correct Answer: A
Rationale: The correct answer is A: incidence. Incidence refers to the number of new cases of a disease occurring within a specific time period in relation to the healthy population. It helps in understanding the risk of developing the disease. Prevalence (B) is the total number of existing cases at a given point in time. Virulence (C) is the severity of the disease once contracted. Mortality (D) refers to the number of deaths due to the disease, not the new cases. Therefore, the correct term for new cases is incidence.
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A vaginal yeast infection is typically caused by:
- A. Histoplasma capsulatum
- B. Candida albicans
- C. Aspergillus niger
- D. Saccharomyces cerevisiae
Correct Answer: B
Rationale: The correct answer is B: Candida albicans. Candida albicans is the most common cause of vaginal yeast infections due to its ability to overgrow in warm, moist environments like the vagina. It is a type of fungus that naturally resides in the body, but can cause infection when its growth is not regulated. Histoplasma capsulatum (A) causes a lung infection, Aspergillus niger (C) causes fungal sinusitis, and Saccharomyces cerevisiae (D) is a type of yeast used in baking and brewing, not typically associated with vaginal infections.
Which of the following best describes bacterial conjugation?
- A. Transfer of DNA through a sex pilus
- B. Uptake of free DNA from the environment
- C. Transfer of DNA by bacteriophages
- D. Binary fission
Correct Answer: A
Rationale: The correct answer is A because bacterial conjugation involves the transfer of genetic material through a sex pilus from a donor bacterium to a recipient bacterium. This process allows for the exchange of genetic material and can lead to increased genetic diversity within bacterial populations.
Option B is incorrect because the uptake of free DNA from the environment is known as transformation, not conjugation. Option C is incorrect as transfer of DNA by bacteriophages is called transduction, not conjugation. Option D is incorrect because binary fission is a form of asexual reproduction in bacteria, not a mechanism for genetic exchange.
Rocky Mountain spotted fever is caused by:
- A. Borrelia burgdorferi
- B. Rickettsia rickettsii
- C. Rickettsia prowazekii
- D. Ehrlichia chaffeensis
Correct Answer: B
Rationale: The correct answer is B: Rickettsia rickettsii. Rocky Mountain spotted fever is caused by Rickettsia rickettsii, a bacterium transmitted by ticks. This pathogen primarily affects the endothelial cells of blood vessels, leading to vasculitis. Borrelia burgdorferi (choice A) causes Lyme disease, not Rocky Mountain spotted fever. Rickettsia prowazekii (choice C) causes epidemic typhus, and Ehrlichia chaffeensis (choice D) causes human monocytic ehrlichiosis, both of which are distinct from Rocky Mountain spotted fever. Therefore, the correct choice is B based on the specific etiology of the disease.
A bacteriological analysis revealed spore-forming, Gram-positive rods in a wound smear. The bacteria were motile and produced gas in nutrient broth. What is the causative agent?
- A. Clostridium perfringens
- B. Bacillus anthracis
- C. Clostridium tetani
- D. Bacillus cereus
Correct Answer: A
Rationale: Rationale:
1. Spore-forming, Gram-positive rods: Characteristics shared by Clostridium and Bacillus.
2. Motile and gas production in nutrient broth: Clostridium perfringens is motile and produces gas, distinguishing it from Bacillus species.
3. Clostridium perfringens causes gas gangrene, correlating with gas production.
4. Bacillus anthracis causes anthrax, not related to wound infections.
5. Clostridium tetani causes tetanus, not associated with gas production.
6. Bacillus cereus causes food poisoning, not commonly associated with wound infections.
Summary:
- A is correct (Clostridium perfringens) due to motility, gas production, and wound infection correlation.
- B (Bacillus anthracis) causes anthrax, not wound infections.
- C (Clostridium tetani) causes tetanus, not gas production.
- D (B
Specify the microbiological characteristic of the air:
- A. Contaminated
- B. Within the permissible limits
- C. Almost pure
- D. Pure
Correct Answer: A
Rationale: The correct answer is A: Contaminated. The air is never completely free of microorganisms, so it is considered contaminated. Microorganisms are ubiquitous in the environment. Permissible limits (B) imply a specific standard, which is not relevant to the general microbiological characteristic of air. Almost pure (C) and pure (D) are not accurate as air always contains some level of microorganisms.