What is the next step when a patient's urine culture shows ß-hemolytic streptococci?
—Joseph Schube, MD
Yorba Linda, Calif
I share your puzzlement. The group A ß-hemolytic streptococcus (Streptococcus pyogenes) is not ordinarily considered to be a urinary pathogen, and I am aware of no unique syndromes or implications associated with group A streptococci in urine cultures. However, the answers to the following 3 questions may prove helpful:
- Was the patient systemically ill? Bacteriuria can be a "spillover" from bloodstream infection. For example, patients with Staphylococcus aureus in urine cultures frequently have positive blood cultures, and the urine isolate is often of incidental significance (although a renal abscess or carbuncle, which can be life-threatening, does develop in some patients).
- Did the microbiology laboratory do special studies on the isolate or send it to a reference laboratory? The streptococci are a diverse group of microorganisms, and bacteriologic tests sometimes misclassify them. For example, not all ß-hemolytic streptococci are group A. Conversely, occasional group A streptococci do not exhibit ß-hemolysis on blood agar plates (these have been likened to a "rattlesnake without a rattle"). Conceivably, the isolate in question could have been a group B streptococcus or an enterococcus.
- What was the clinical scenario? Enterococci, the "streptococci" that most frequently cause urinary tract infection, are often associated with obstructive uropathy of various origins. If the patient had asymptomatic bacteriuria, I would repeat the culture and, if the culture were confirmed, possibly prescribe a short course of a ß-lactam antibiotic. Assuming the patient had normal renal function, oral penicillin V would be a good choice; like most ß-lactam antibiotics, it is eliminated mainly by renal excretion.
Professor of Medicine
Director, Division of Infectious Diseases
University of South Carolina School of Medicine
Columbia
