Question

A patient in the hospital has an intravenous catheter inserted to allow for the delivery of medications, fluids, and electrolytes. Four days after the catheter is inserted, the patient develops a fever and an infection in the skin around the catheter. Blood cultures reveal that the patient has a blood-borne infection. Tests in the clinical laboratory identify the blood-borne pathogen as Staphylococcus epidermidis, and antibiotic susceptibility tests are performed to provide doctors with essential information for selecting the best drug for treatment of the infection. Antibacterial chemotherapy is initiated and delivered through the intravenous catheter that was originally inserted into the patient. Within 7 days, the skin infection is gone, blood cultures are negative for S. epidermidis, and the antibacterial chemotherapy is discontinued. However, 2 days after discontinuing the antibacterial chemotherapy, the patient develops another fever and skin infection and 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 oral antibiotics, which successfully treat both the skin and blood-borne infection caused by S. epidermidis. Furthermore, the infection does not return after discontinuing the oral antibacterial chemotherapy. What are some possible reasons why intravenous chemotherapy failed to completely cure the patient despite laboratory tests showing the bacterial strain was susceptible to the prescribed antibiotic? Why might the second round of antibiotic therapy have been more successful? Justify your answers.

Answer 1

A patient who developed Staphylococcus epidermis infection as shown by the blood culture here is treated with intravenous antibiotics has also developed skin infection. Initially, the fever subsided and the skin infection subsided but after it recurred showing same infection and next episode of antibiotics orally was effective. The reasons could be :

Some bacteria are able to borrow resistance genes from neighbouring species through horizontal gene transfer and they are able to reproduce at an astonizing high speed that some of the Staphylococcus epidermis would have left being unaffected by the antibiotic therapy at initial antibiotic therapy.

Since antibiotics are used frequently these days , there is increased chance of developing resistance to few antibiotics and may require the second round of antibiotic therapy.

Some require combination of antibiotics to treat the infection. The next episode would have involved the use of combination which would have worked better.

Usually, skin infections have a chance of relapse and that is reason of need of second episode of antibiotics.

Thank you..