Microbiology Fundamentals 2nd Edition by Jennifer Bunn,Marjorie Kelly Cowan

Exercise 1

C A S E F I L E

Tracing the Cause
When I was a lab tech student, my preceptor and I were asked to go to the emergency room to draw blood on a patient. The lab requisition filled out by the nurse caring for the patient stated the patient had "fever for 1 week with a decreased level of consciousness."
On reporting to the ER, we were directed to the patient, who was lying on a gurney in an exam room. The patient was a 78-year-old diabetic gentleman who appeared pale and thin. We introduced ourselves and told the patient that we were there to draw blood. The patient barely acknowledged our presence and seemed to have difficulty staying awake. The ER nurses had already collected a urine specimen from the patient's Foley catheter for urinalysis and culture. They handed us the specimens they had collected, which had been labeled correctly with the patient's name and the collection date and time.
We proceeded to draw blood according to the physician's order. We obtained blood for a complete blood count, electrolytes, blood glucose, liver function, and cardiac markers. We also obtained blood from two different sites for blood cultures. Once we had collected all of the samples, we notified the nursing staff that we were finished. We labeled all the collection vials with the necessary information and returned to the lab.
After running all of the tests that could be performed in-house, we sent copies of all of the reports to the ER. The patient's hemoglobin and hematocrit were slightly low. The white blood cell count was very high. The patient's potassium was high, and the sodium level was low. Liver function was normal, as were cardiac markers. The urinalysis showed ketones and protein in the urine, evidence of dehydration but not of infection. The patient's serum glucose was high but not dangerously so.
On the basis of these lab studies, the patient was rehydrated with intravenous fluids and his potassium and sodium levels were soon corrected. He was also given insulin to lower his blood glucose. The patient was started on broad spectrum IV antibiotics pending the results of the urine and blood cultures. He continued to run a high fever and was only semiconscious following admission to the ICU.
The preliminary urine cultures failed to identify any bacteria in the patient's urine. That left the blood cultures; when the preliminary results came back in 48 hours, the results revealed the presence of Staphylococcus epidermidis in the patient's blood. Sensitivity studies showed that the organism was sensitive to Penicillin G, rifampin, and vancomycin. It also revealed that the microorganism was resistant to the ceftriaxone that the patient was currently receiving. The patient was switched to Penicillin G every 6 hours intravenously, and he made a relatively rapid recovery soon thereafter, with his fever disappearing within 36 hours.
• Why are blood cultures collected from two different sites?
• Why was it important for the laboratory staff to notify the nursing staff after the samples had been collected?