A clean catch urine from a female with suspected UTI shows Gram-positive cocci that are catalase positive, coagulase negative, and staph latex negative; novobiocin panel shows growth. Which organism is most likely?

A clean catch urine from a female with suspected UTI shows Gram-positive cocci that are catalase positive, coagulase negative, and staph latex negative; novobiocin panel shows growth. Which organism is most likely?

• A. Staphylococcus saprophyticus
• B. Staphylococcus aureus
• C. Enterococcus faecalis
• D. Streptococcus pyogenes

Answer: (A)

Identification of the organism relies on a stepwise interpretation of tests that separate staphylococci from streptococci, then distinguish S. aureus from coagulase‑negative staphylococci, and finally differentiate among CoNS by novobiocin susceptibility. The Gram stain showing cocci in clusters points to Staphylococcus. A catalase-positive result confirms a Staphylococcus species rather than Streptococcus. A negative coagulase test rules out Staphylococcus aureus, leaving coagulase-negative staphylococci. The latex agglutination test being negative supports a non‑aureus staphylococcal species. The novobiocin test shows growth, indicating resistance to novobiocin. Among coagulase-negative staphylococci, Staphylococcus saprophyticus is resistant to novobiocin, whereas others like Staphylococcus epidermidis are susceptible. In a young woman with a UTI, this combination—Gram-positive cocci in clusters, catalase positive, coagulase negative, latex test negative, and novobiocin-resistant—is most consistent with Staphylococcus saprophyticus.

Identification of the organism relies on a stepwise interpretation of tests that separate staphylococci from streptococci, then distinguish S. aureus from coagulase‑negative staphylococci, and finally differentiate among CoNS by novobiocin susceptibility. The Gram stain showing cocci in clusters points to Staphylococcus. A catalase-positive result confirms a Staphylococcus species rather than Streptococcus. A negative coagulase test rules out Staphylococcus aureus, leaving coagulase-negative staphylococci. The latex agglutination test being negative supports a non‑aureus staphylococcal species. The novobiocin test shows growth, indicating resistance to novobiocin. Among coagulase-negative staphylococci, Staphylococcus saprophyticus is resistant to novobiocin, whereas others like Staphylococcus epidermidis are susceptible. In a young woman with a UTI, this combination—Gram-positive cocci in clusters, catalase positive, coagulase negative, latex test negative, and novobiocin-resistant—is most consistent with Staphylococcus saprophyticus.