Nokea
The most commonly acquired laboratory infections are caused by
- A. bacteria.
- B. viruses.
- C. protozoans.
- D. prions.
Correct Answer: A
Rationale: The correct answer is A: bacteria. Bacteria are the most common cause of laboratory-acquired infections due to their ability to survive and multiply in various environments. They can easily contaminate lab equipment and surfaces, leading to infections if proper precautions are not taken. Viruses (choice B) are less common in laboratory-acquired infections as they require specific conditions to survive outside a host. Protozoans (choice C) are larger and less likely to be transmitted in a laboratory setting. Prions (choice D) are misfolded proteins and are not considered living organisms, making them an unlikely source of laboratory infections.
You may also like to solve these questions
A patient with a sore throat had a throat culture revealing Gram-positive cocci in chains. The bacteria were catalase-negative and beta-hemolytic on blood agar. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Staphylococcus aureus
- C. Streptococcus pneumoniae
- D. Enterococcus faecalis
Correct Answer: A
Rationale: Step 1: Gram-positive cocci in chains suggest Streptococcus species.
Step 2: Catalase-negative eliminates Staphylococcus aureus.
Step 3: Beta-hemolytic on blood agar matches Streptococcus pyogenes.
Step 4: Streptococcus pyogenes is a common cause of sore throat (pharyngitis).
Summary:
A: Streptococcus pyogenes - Correct due to Gram-positive cocci in chains, catalase-negative, beta-hemolytic, and common cause of sore throat.
B: Staphylococcus aureus - Incorrect due to catalase-positive.
C: Streptococcus pneumoniae - Incorrect due to alpha-hemolytic.
D: Enterococcus faecalis - Incorrect due to not being beta-hemolytic.
Complex communities of microorganisms on surfaces are called
- A. colonies
- B. biofilms
- C. biospheres
- D. flora
Correct Answer: B
Rationale: The correct answer is B: biofilms. Biofilms refer to complex communities of microorganisms that adhere to surfaces. They are characterized by a protective matrix that allows the microorganisms to communicate and cooperate. Colonies (A) typically refer to groups of a single species, not diverse communities. Biospheres (C) refer to the regions of the Earth where life exists, not specific microbial communities. Flora (D) generally refers to the plant life in a particular region, not microbial communities on surfaces.
A patient with a sore throat and fever had a throat culture revealing Gram-positive cocci in chains. The bacteria were beta-hemolytic. What is the most likely causative agent?
- A. Streptococcus pyogenes
- B. Streptococcus pneumoniae
- C. Enterococcus faecalis
- D. Staphylococcus aureus
Correct Answer: A
Rationale: The correct answer is A: Streptococcus pyogenes.
1. Gram-positive cocci in chains suggest streptococci.
2. Beta-hemolytic activity indicates Streptococcus pyogenes.
3. Streptococcus pyogenes is commonly associated with sore throat (pharyngitis) and fever.
4. Streptococcus pneumoniae (choice B) is alpha-hemolytic and mainly causes pneumonia.
5. Enterococcus faecalis (choice C) is not typically associated with sore throat.
6. Staphylococcus aureus (choice D) is not commonly beta-hemolytic and is not a typical cause of pharyngitis.
What reaction is catalyzed by a beta-lactamase enzyme
- A. the final cross-linking reaction to form the bacterial cell wall
- B. the biosynthesis of the penicillin structure from the amino acid valine and cysteine
- C. the hydrolysis of the four-membered ring present in penicillin
- D. the hydrolysis of the acyl side chain from penicillin structures
Correct Answer: C
Rationale: The correct answer is C: the hydrolysis of the four-membered ring present in penicillin. Beta-lactamase enzyme catalyzes the hydrolysis of the four-membered beta-lactam ring present in penicillin, rendering the antibiotic ineffective against bacterial cell walls. This enzyme breaks the bond in the beta-lactam ring, thus inactivating the antibiotic.
Incorrect choices:
A: the final cross-linking reaction to form the bacterial cell wall - This is incorrect as beta-lactamase does not participate in the formation of bacterial cell walls.
B: the biosynthesis of the penicillin structure from the amino acid valine and cysteine - This is incorrect as beta-lactamase is not involved in the biosynthesis of penicillin.
D: the hydrolysis of the acyl side chain from penicillin structures - This is incorrect as beta-lactamase specifically targets the beta-lactam ring, not the
A 28-year-old patient was hospitalized with preliminary diagnosis "influenza". Roseolous-petechial rash appeared on the 5th day of disease on the trunk. The temperature is 41oC. Hyperemia of face, reddening of scleras, tremor of tongue, tachycardia, splenomegaly are present. What is the most likely diagnosis?
- A. Epidemic typhus
- B. Measles
- C. Alcohol delirium
- D. Leptospirosis
Correct Answer: A
Rationale: The most likely diagnosis is Epidemic typhus (Choice A) based on the symptoms described. The presence of roseolous-petechial rash, high fever (41oC), hyperemia of face, reddening of scleras, tremor of the tongue, tachycardia, and splenomegaly are classic signs of epidemic typhus. The rash typically appears around the 5th day of the disease.
Summary:
- B: Measles typically presents with a maculopapular rash starting on the face and spreading downward. It doesn't usually present with tremor of the tongue or splenomegaly.
- C: Alcohol delirium is characterized by confusion, disorientation, and hallucinations due to alcohol consumption. It doesn't match the symptoms described.
- D: Leptospirosis presents with fever, muscle pain, and conjunctival suffusion. It doesn't typically present with the specific rash and trem