A case of Staphylococcus saprophyticus bacteremia caused by obstructive pyelonephritis

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Clinical Bacteriology

Background:

• Urinary tract infections (UTIs) are commonly caused by Staphylococcus saprophyticus, particularly in younger women.
• Bloodstream infections (bacteremia) with coagulase-negative staphylococci, including S. saprophyticus, are infrequently reported and often presumed to be contaminants.
• Accurate identification of bacterial pathogens is critical for effective patient management.

Observation:

• A 64-year-old woman presented with left calculous pyelonephritis.
• Blood cultures yielded Gram-positive cocci in clusters, identified as Staphylococcus saprophyticus.
• This represents a rare instance of S. saprophyticus bacteremia in an older adult with pyelonephritis.

Findings:

• The isolated Staphylococcus saprophyticus strain was identified through blood culture analysis.
• The presence of S. saprophyticus in blood cultures, in this case, represented true bacteremia rather than contamination.
• This finding challenges the common assumption of contamination for coagulase-negative staphylococci in blood cultures from UTI patients.

Implications:

• Accurate identification and antimicrobial susceptibility testing of S. saprophyticus are essential for diagnosing and treating true bacteremia.
• The high prevalence of methicillin-resistant S. saprophyticus necessitates careful antibiotic selection.
• This case highlights the importance of considering less common pathogens in severe infections and the need for robust diagnostic protocols.