A patient in the hospital has an intravenous catheter insertedto allow for the delivery of medications, fluids, and electrolytes.Four days after the catheter is inserted, the patient develops afever and an infection in the skin around the catheter. Bloodcultures reveal that the patient has a blood-borne infection. Testsin the clinical laboratory identify the blood-borne pathogen asStaphylococcus epidermidis, and antibiotic susceptibility tests areperformed to provide doctors with essential information forselecting the best drug for treatment of the infection.Antibacterial chemotherapy is initiated and delivered through theintravenous catheter that was originally inserted into the patient.Within 7 days, the skin infection is gone, blood cultures arenegative for S. epidermidis, and the antibacterial chemotherapy isdiscontinued. However, 2 days after discontinuing the antibacterialchemotherapy, the patient develops another fever and skin infectionand the blood cultures are positive for the same strain of S.epidermidis that had been isolated the previous week. This time,doctors remove the intravenous catheter and administer oralantibiotics, which successfully treat both the skin and blood-borneinfection caused by S. epidermidis. Furthermore, the infection doesnot return after discontinuing the oral antibacterial chemotherapy.What are some possible reasons why intravenous chemotherapy failedto completely cure the patient despite laboratory tests showing thebacterial strain was susceptible to the prescribed antibiotic? Whymight the second round of antibiotic therapy have been moresuccessful? Justify your answers.
