Nokea
Which bacteria are known for their ability to fix nitrogen?
- A. Bacillus cereus
- B. Azotobacter species
- C. Clostridium botulinum
- D. Escherichia coli
Correct Answer: B
Rationale: The correct answer is B: Azotobacter species. Azotobacter are known for their ability to fix nitrogen through the process of nitrogen fixation, converting atmospheric nitrogen into a form that plants can use. Bacillus cereus is not known for nitrogen fixation. Clostridium botulinum is a bacterium that causes botulism and does not fix nitrogen. Escherichia coli is a common gut bacterium but does not have the ability to fix nitrogen. Thus, Azotobacter species is the correct choice based on its unique ability to fix nitrogen.
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Which one of the following statements about Campylobacter fetus is NOT CORRECT?
- A. Gram-positive rod-shaped bacterium
- B. Optimal temperature for cultivation 35-37C
- C. Opportunistic pathogen causes infections usually in newborns, immunocompromised patients and cancer
- D. Fastidious, microaerophile
Correct Answer: A
Rationale: The correct answer is A: Gram-positive rod-shaped bacterium. Campylobacter fetus is actually a Gram-negative bacterium. This is because it has a thin peptidoglycan layer in its cell wall, which does not retain the crystal violet stain used in the Gram-staining technique. It appears red or pink under a microscope after counterstaining with safranin. Therefore, statement A is incorrect.
B: Optimal temperature for cultivation 35-37C - Correct, as Campylobacter fetus thrives at this temperature range.
C: Opportunistic pathogen causes infections usually in newborns, immunocompromised patients, and cancer - Correct, as Campylobacter fetus can cause infections in these populations.
D: Fastidious, microaerophile - Correct, as Campylobacter fetus is fastidious and requires specific growth conditions, including low oxygen levels.
Which of the following best describes the Gram stain process?
- A. It differentiates bacteria based on their flagella
- B. It identifies bacteria based on their shape
- C. It differentiates bacteria based on their cell wall structure
- D. It is used to determine bacterial motility
Correct Answer: C
Rationale: The Gram stain process involves staining bacterial cells with crystal violet and iodine, followed by decolorization and counterstaining. The primary differentiation is based on the cell wall structure, distinguishing bacteria into Gram-positive (retain purple color) and Gram-negative (lose purple color). This classification is crucial in microbiology for treatment decisions as it correlates with different antibiotic susceptibilities. Choices A, B, and D are incorrect because the Gram stain process does not primarily focus on flagella, shape, or motility of bacteria.
The bacteria that causes whooping cough is:
- A. Bordetella pertussis
- B. Haemophilus influenzae
- C. Pseudomonas aeruginosa
- D. Streptococcus pneumoniae
Correct Answer: A
Rationale: The correct answer is A: Bordetella pertussis. Whooping cough is caused by this bacteria, which specifically infects the respiratory tract. Bordetella pertussis produces toxins that lead to the characteristic symptoms of the disease. Haemophilus influenzae, Pseudomonas aeruginosa, and Streptococcus pneumoniae are not the causative agents of whooping cough. Haemophilus influenzae can cause respiratory infections, Pseudomonas aeruginosa is associated with hospital-acquired infections, and Streptococcus pneumoniae is a common cause of pneumonia and other respiratory infections, but none of these bacteria are responsible for whooping cough.
Differentiating media are:
- A. Lowenstein-Jensen and Petraniani
- B. Apoholate-citrate aga and Brilliant-green phenol-red Lactose Agar
- C. Endo, Gassner and Levin
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C because Endo, Gassner, and Levin are all examples of differential media used in microbiology. These media contain specific components that allow for the differentiation of different types of microorganisms based on their metabolic characteristics or biochemical reactions. Lowenstein-Jensen and Petraniani (choice A) are selective media for mycobacteria, not differential. Apoholate-citrate agar and Brilliant-green phenol-red Lactose agar (choice B) are selective media for Salmonella and E. coli, respectively, not differential. Therefore, the correct choice is C as it includes examples of differential media commonly used for microbial identification.
Infections of the reproductive tract resulting from the introduction of microorganisms through a medical procedure are called:
- A. chronic infections
- B. endogenous infections
- C. systemic infections
- D. iatrogenic infections
Correct Answer: D
Rationale: The correct answer is D: iatrogenic infections. Iatrogenic infections refer to infections caused by medical or surgical treatment, including procedures that introduce microorganisms into the body. In this case, infections of the reproductive tract caused by medical procedures fall under this category.
A: Chronic infections do not specifically refer to infections caused by medical procedures.
B: Endogenous infections arise from organisms already present in or on the body, not introduced through medical procedures.
C: Systemic infections affect the entire body, not specific to infections caused by medical procedures.
Therefore, the term "iatrogenic infections" is the most appropriate choice in this context.