Nokea
A wound culture revealed Gram-negative rods that are lactose non-fermenters. The bacteria were isolated from a patient with a deep tissue infection. What is the most likely microorganism?
Correct Answer: A
Rationale: The correct answer is A: Pseudomonas aeruginosa. P. aeruginosa is a Gram-negative rod that is a lactose non-fermenter commonly associated with deep tissue infections. It is an opportunistic pathogen known for its ability to cause infections in immunocompromised individuals. P. aeruginosa is often resistant to multiple antibiotics and can form biofilms, making it difficult to treat.
Summary of why other choices are incorrect:
B: Escherichia coli is a Gram-negative rod that ferments lactose and is commonly found in the gastrointestinal tract. It is not typically associated with deep tissue infections.
C: Salmonella typhi is a Gram-negative rod that causes typhoid fever, primarily affecting the gastrointestinal system, not deep tissue infections.
D: Shigella dysenteriae is a Gram-negative rod that causes bacillary dysentery, which primarily affects the gastrointestinal tract and does not typically cause deep tissue infections.