A 24-year-old female presents to your office with burning urination, urgency and frequency. She is sexually active. Urine cultures show catalase-positive, gram-positive cocci. The organism responsible for this patient's symptoms is most likely to be:

Question

A 24-year-old female presents to your office with burning urination, urgency and frequency.  She is sexually active.  Urine cultures show catalase-positive, gram-positive cocci.  The organism responsible for this patient's symptoms is most likely to be:

Quizplus · Accepted Answer

11ec160b_3877_81b1_9249_433e6409369d_MD0001_00 The Staphylococci are Gram-positive cocci that form clusters, pairs and, rarely, short chains. The catalase test (with 3% hydrogen peroxide) differentiates Streptococci (catalase-negative) from Staphylococci (catalase-positive). The ability to clot blood plasma (slide and tube coagulase tests) separates Staphylococci into two groups: the coagulase-positive Staphylococci, which constitutes the most pathogenic species Staphylococcus aureus, and coagulase-negative staphylococci (CNS), which constitutes S. epidermidis, S. Saprophyticus, S. haemolyticus, and 30+ other species. The coagulase-negative staphylococci exist as part of the normal flora on the skin and in the throat and nose, and only some species can cause infections. S. saprophyticus is a common cause of urinary tract infection; it is responsible for almost half of all UTIs in sexually active young women. S. saprophyticus is resistant to novobiocin. When catalase-positive, coagulase-negative gram-positive cocci in clusters are isolated from urine specimens of the above group of patients, the laboratory performs a novobiocin test to distinguish this organism from other similar pathogens. (Choice A) Coagulase positivity is a characteristic of S. aureus; this is how S. aureus is differentiated from the other species of Staphylococci that do not express coagulase. (Choice B) Hemolysis is a typical feature of Streptococci (streptolysin O and streptolysin S) and Staphylococcus aureus (hemolysin). S. saprophyticus does not cause hemolysis. (Choice D) DNase is produced by group A streptococcus. DNase degrades DNA in pus to facilitate spread of the organism. Anti DNase can be used as a laboratory test in patients who have had streptococcal infection followed by glomerulonephritis. DNase is not produced by S. saprophyticus. (Choice E) Yellow pigment is produced by Staphylococcus aureus. Staphylococcus aureus usually does not cause urinary tract infections. If S. aureus is cultured from the urine you should suspect a metastatic infection from another location in the body (an abscess or infective endocarditis etc.) Educational Objective: S saprophyticus is responsible for almost half of all UTIs in sexually active young women. Staphylococcus saprophyticus belongs to coagulase negative staphylococci and is unique among these because it is resistant to novobiocin.

A 24-Year-Old Female Presents to Your Office with Burning Urination