Vancomycin-Intermediate Staphylococcus aureus

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A 69-year-old male presented to the Emergency Department with fever, altered mental status and hiccups. Past medical history consisted of seizures, brain cyst removed in 2010 and a brain shunt placed in 2011. Patient also had a history of kidney stones and recurrent urinary tract infections (UTIs). Patient was started on empiric treatment for bacteremia (blood stream infection (BSI)) which consisted of vancomycin, cefepime and metronidazole. While the patient was in the hospital his condition declined and Ceftriaxone replaced Cefepime for possible community acquired pneumonia (CAP). Urine and respiratory specimens were collected for culture along with blood cultures for possible BSI. 

Lab Testing

Urine and respiratory cultures were negative. Blood cultures were positive on days 2, 3 and 6 with Staphylococcus aureus. All 3 sets of blood cultures grew methicillin resistant S. aureus (MRSA).  On days 2 and 3 the vancomycin MIC of the S. aureus was 2 µg/ml (which means the minimum inhibitory concentration (MIC) of the isolate was susceptible to vancomycin). On day 6 the vancomycin MIC increased to 4 µg/ml (which means MIC of the isolate was intermediate to vancomycin – vancomycin intermediate S. aureus (VISA)). 

Cause of Symptoms

Fever and altered mental status in the patient were due to a blood stream infection (BSI) or bacteremia with S. aureus. S. aureus is a common pathogen that is recovered from cases of BSI in patients. It is important in cases of S. aureus BSI that the susceptibility testing is known as soon as possible since the presence of MRSA and VISA (or vancomycin resistant S. aureus (VRSA)) can cause the empiric treatment for the BSI to fail. 


Empiric therapy can vary depending on the patients’ clinical presentation and other host factors. This patient was treated with vancomycin, cefepime and metronidazole, with the cefepime being changed to ceftriaxone to cover possible CAP. Because of the presence of the VISA, vancomycin was ultimately discontinued and the patient was placed on Linezolid. 

Blood is normally a sterile site and when bacteria are detected in the blood this is typically an abnormal finding.  Transient bacteremia can occur, for example when people have dental procedures, and contaminants from the skin can be introduced into the blood culture bottle when the blood sample is collected due to inadequate sterilization of the skin upon venipuncture.  Bacteremia can result in a patient via several mechanism such as, pneumonia, meningitis, surgery, introduced via a foreign body to name a few and can cause a severe infection called sepsis which can be life threatening.   Treatment for suspected bacteremia is often empiric when the patient presents with symptoms of a BSI since no laboratory data is available to confirm the pathogen at the time of admission to the emergency department. 

Contact Information

Nicole Jackson,