Our Microbiology Department serves only outpatients. We do not routinely perform susceptibility testing on enterococci isolated from urine. Instead, we send a report stating that enterococci are predictably susceptible to urinary concentrations of ampicillin, but resistant to trimethoprim/sulfamethoxazole and cephalosporins. I have been asked to initiate screening for vancomycin resistance in enterococcal isolates, but I am unclear as to the need for this information, since we receive specimens only from outpatients.

Answer:

Ascertaining how the vancomycin susceptibility test results will be used is imperative before any decision about initiating testing can be made. Typically, a clinical microbiology laboratory develops susceptibility testing and reporting protocols in conjunction with the clinical services in their institutions who will use the results (e.g. Medical and Surgery services, Infectious Disease Specialists, Infection Control, Pharmacy, other medical staff, etc.). Your situation is different since only isolates from outpatients are tested. Yet, some of these specimens may come from patients who are seen in ambulatory surgery centers, attend adult day care centers, or spend time in non-traditional healthcare delivery centers where vancomycin-resistant enterococcal infections may develop and spread. Thus, there may be a legitimate reason for determining vancomycin resistance. Each laboratory needs to adopt protocols that best serve their "customers", but this should be based on a clear understanding of how the information will be used. This is part of the laboratory's quality assurance program.

References:

Cetinkaya, Y, P Falk, and G Mayhall. 2000. Vancomycin-resistant enterococci. Clin. Microbiol. Rev. 13(4):686-601.

Murray, BE. 2000. Vancomycin-resistant enterococcal infections. . N. Engl. J. Med. 342:710-721.