Which genus includes species that are Gram-negative, motile rods and may produce a red pigment, implicated in septicemia, pneumonia, and UTIs?

Which genus includes species that are Gram-negative, motile rods and may produce a red pigment, implicated in septicemia, pneumonia, and UTIs?

• A. Serratia marcescens
• B. Pseudomonas aeruginosa
• C. Klebsiella pneumoniae
• D. Escherichia coli

Answer: (A)

Red pigment production by a Gram-negative, motile rod points to the genus Serratia. Serratia marcescens is a classic example: it is a Gram-negative rod that is capable of motility and, at room temperature, often produces a distinctive red pigment called prodigiosin. This pigment-producing trait, along with its association with hospital-acquired infections such as septicemia, pneumonia, and urinary tract infections, helps identify Serratia in clinical contexts. Other organisms listed can cause similar infections and are Gram-negative rods with motility, but their pigments are different or absent. Pseudomonas aeruginosa also causes pneumonia and septicemia and UTIs, but its hallmark pigment is blue-green (pyocyanin) rather than red. Klebsiella pneumoniae is typically nonmotile and does not produce a red pigment, and Escherichia coli, while a common cause of UTIs and other infections, does not have a characteristic red pigment production.

Red pigment production by a Gram-negative, motile rod points to the genus Serratia. Serratia marcescens is a classic example: it is a Gram-negative rod that is capable of motility and, at room temperature, often produces a distinctive red pigment called prodigiosin. This pigment-producing trait, along with its association with hospital-acquired infections such as septicemia, pneumonia, and urinary tract infections, helps identify Serratia in clinical contexts.

Other organisms listed can cause similar infections and are Gram-negative rods with motility, but their pigments are different or absent. Pseudomonas aeruginosa also causes pneumonia and septicemia and UTIs, but its hallmark pigment is blue-green (pyocyanin) rather than red. Klebsiella pneumoniae is typically nonmotile and does not produce a red pigment, and Escherichia coli, while a common cause of UTIs and other infections, does not have a characteristic red pigment production.