A Gram-positive cocci in chains was isolated from a patient with a throat infection. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?

Questions 80

ATI RN

ATI RN Test Bank

microbiology an introduction 13th edition test bank Questions

Question 1 of 9

A Gram-positive cocci in chains was isolated from a patient with a throat infection. The bacteria were catalase-negative and beta-hemolytic. What is the most likely causative agent?

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pyogenes. Rationale: 1. Gram-positive cocci in chains: S. pyogenes is a Gram-positive cocci in chains. 2. Catalase-negative: S. pyogenes is catalase-negative. 3. Beta-hemolytic: S. pyogenes exhibits beta-hemolysis. Summary of other choices: B: Streptococcus pneumoniae is alpha-hemolytic and optochin-sensitive. C: Enterococcus faecalis is catalase-negative, but not typically beta-hemolytic. D: Staphylococcus aureus is catalase-positive and coagulase-positive.

Question 2 of 9

Infections that may result from the use of catheters are classified as:

Correct Answer: A

Rationale: The correct answer is A: iatrogenic infections. Iatrogenic infections are those caused by medical interventions like catheter use. Catheters can introduce pathogens into the body, leading to infections. Local infections (B) refer to infections confined to a specific area, not necessarily caused by catheters. Exogenous infections (C) come from an external source, not specifically related to medical interventions. Endogenous infections (D) arise from the body's own flora and are not directly related to catheter use.

Question 3 of 9

A Gram-negative, comma-shaped bacterium was isolated from a patient with cholera. What is the most likely microorganism?

Correct Answer: A

Rationale: The correct answer is A: Vibrio cholerae. 1. Vibrio cholerae is a Gram-negative, comma-shaped bacterium known to cause cholera. 2. Shigella dysenteriae causes dysentery, not cholera. 3. Salmonella typhi causes typhoid fever, not cholera. 4. Campylobacter jejuni causes gastroenteritis, not cholera. Therefore, based on the symptoms presented and the characteristics of the bacterium, Vibrio cholerae is the most likely microorganism.

Question 4 of 9

The most common urinary tract pathogen is:

Correct Answer: C

Rationale: The correct answer is C: Escherichia coli. E.coli is the most common urinary tract pathogen due to its ability to adhere to and infect the urinary tract epithelium. It accounts for approximately 80-85% of urinary tract infections. It possesses specific virulence factors that enable it to colonize and cause infection in the urinary tract. Proteus mirabilis (A) is known for causing complicated UTIs, but it is less common than E.coli. Staphylococcus aureus (B) is not a common urinary pathogen. Pseudomonas aeruginosa (D) is more commonly associated with hospital-acquired infections, rather than community-acquired urinary tract infections.

Question 5 of 9

Staphylococcal scalded skin syndrome is most common in:

Correct Answer: A

Rationale: The correct answer is A: infants. Staphylococcal scalded skin syndrome is most common in infants because their immune systems are not fully developed, making them more susceptible to Staphylococcus aureus infections. This bacteria produces exotoxins that cause the skin to blister and peel, characteristic of the syndrome. Adolescents, young adults, and the elderly have more mature immune systems, making them less vulnerable to this specific infection. Therefore, infants are at a higher risk for developing Staphylococcal scalded skin syndrome compared to other age groups.

Question 6 of 9

A wound culture grew Gram-positive rods with central spores. The bacteria were catalase-positive and aerobic. Identify the microorganism.

Correct Answer: A

Rationale: The correct answer is A: Bacillus anthracis. The presence of Gram-positive rods with central spores, catalase-positive, and aerobic growth characteristics are indicative of Bacillus anthracis. Bacillus anthracis is known for its central spores and ability to grow aerobically. Summary of why other choices are incorrect: B: Clostridium tetani is a Gram-positive rod with terminal spores and is anaerobic. C: Streptococcus pyogenes is a Gram-positive cocci and catalase-negative. D: Klebsiella pneumoniae is a Gram-negative rod and catalase-positive, but is not associated with central spores.

Question 7 of 9

A 70-year-old man was admitted to the hospital after suffering extensive third-degree burns. Three days later he spiked a fever and there was pus on the dressing that had blue-green colour. Gram stain of the pus revealed gram-negative rods. The most possible cause of these findings is:

Correct Answer: A

Rationale: The correct answer is A: The pyocyanin released by Pseudomonas aeruginosa. Pyocyanin is a blue-green pigment produced by Pseudomonas aeruginosa, a common cause of nosocomial infections in burn patients. The presence of blue-green pus and gram-negative rods in the wound along with fever suggests an infection with Pseudomonas aeruginosa. The other choices are incorrect because E. Coli typically causes gastrointestinal infections and releases enterotoxins, Staphylococcus aureus releases hemolysins causing hemolysis of red blood cells, and Shigella dysenteriae releases shigatoxin causing bloody diarrhea, none of which match the clinical presentation described in the question.

Question 8 of 9

Characteristic features of infectious process:

Correct Answer: D

Rationale: Step-by-step rationale: 1. Infectious process triggers an immune response to fight off the invading pathogen. 2. The immune response can lead to inflammation, fever, and production of antibodies. 3. Hypersensitivity reactions can also occur in response to the infection. 4. Options A, B, and C are not defining features of the infectious process. Summary: Option D is correct because an infectious process typically leads to an immune response and possibly hypersensitivity reactions. Options A, B, and C are incorrect as they do not specifically relate to the immune response or hypersensitivity reactions in the context of an infectious process.

Question 9 of 9

What is virus Fixe?

Correct Answer: A

Rationale: The correct answer is A: A vaccine strain. Virus Fixe is a specific strain of rabies virus used in the production of rabies vaccines. This strain has been attenuated to be safe for use in vaccines. Choice B, a cell culture, is incorrect as it does not specifically refer to Virus Fixe. Choice C, a wild type of rabies virus, is incorrect as Virus Fixe is not a wild type but a modified strain. Choice D, an infectious disease, is incorrect as Virus Fixe is not a disease but a strain of virus used in vaccines.

Access More Questions!

ATI RN Basic


$89/ 30 days

ATI RN Premium


$150/ 90 days