Which lab test determines the species of bacteria and the antibiotic to which it is susceptible?

• A. Culture and sensitivity
• B. Gram stain
• C. Blood culture
• D. Urine culture

Answer: (A)

Culture and sensitivity testing is the lab method that identifies the bacterial species and determines which antibiotics the organism is susceptible to. By growing the organism from the patient sample (culture) labs can pinpoint its species, and then they test how it responds to various antibiotics (sensitivity testing) to guide effective treatment. A Gram stain provides rapid information about whether bacteria are Gram-positive or Gram-negative and their shape, but it does not identify the exact species or reveal which drugs will work. Blood culture and urine culture detect bacteria in blood or urine, respectively, but on their own do not provide the susceptibility profile—the isolated organisms from those cultures are what undergo susceptibility testing.