Question

A nosocomial outbreak of bacteremia occurred in an adult oncology unit, and active surveillance for the presence of the causative pathogen was instituted by monitoring stools and perianal cultures of patients.Enterococcus faecium was isolated from stools in patients with bacteremia and 22 noninfected carriers. The stool isolates of bacteremic patients were found to be closely related to the respective blood isolates as determined by DNA typing techniques, in this case pulsed-field gel electrophoresis. Prior treatment with an aminoglycoside and high-dose ampicillin in some bacteremia patients proved to be ineffective. Therefore, to determine appropriate antimicrobial therapy for the treatment of the nosocomial E. faecium outbreak isolate, susceptibility testing was performed. Because prior therapy with aminoglycoside and high-dose ampicillin failed, molecular and genetic studies were performed to characterize the mechanisms of resistance, and their possible means of dissemination.

1. The role of empirical therapy on the treatment of disease.

2. Whether prior antibiotic treatment failure provides insight to possible mechanisms of resistance

3. How the bacterial targets of the different antibiotic classes differ.

4. How the bacterial targets of the different antibiotic classes differ.

5. Which antibiotic mechanism of resistance can produce the same resistance phenotype.

6. Which mechanism of resistance is most likely to produce cross-resistance to multiple classes of antibiotics.

7. The separate role of intrinsic and acquired mechanisms of resistance in antibiotic therapy

8. How acquired mechanisms of resistance are transmitted between organisms.

Answer 1