VANCOMYCIN RESISTANCE IN GRAM-POSITIVE ORGANISMS

Vancomycin is active against most Gram-positive bacteria. The genera L euconostoc, Lactobacillus, Pediococcus and Erysipelothrix are normally resistant to vancomycin but do not represent a major problem because the incidence of infections caused by these organisms is low and they are usually susceptible to other antimicrobial agents. More disturbing , however, is the emergence of vancomycin resistance in clinical enter ococcal and staphylococcal isolates. Acquisition of new genes is respo nsible for vancomycin resistance in isolates or Enterococcus faecalis and Enterococcus faecium. Whereas low-level vancomycin resistance appe ars to be a normal or inherent characteristic of Enterococcus gallinar um and Enterococcus casseliflavus. To date, vancomycin resistance has not been reported in clinical isolates of Streptococcus spp. or Staphy lococcus aureus. However, stepwise decreases in vancomycin susceptibil ity have been observed in coagulase-negative staphylococci, particular ly Staphylococcus haemolyticus. Because coagulase-negative staphylococ ci and enterococci are now the second and third most common organisms causing hospital-acquired bloodstream infection in the USA, respective ly, and because resistance to vancomycin in these organisms is usually accompanied by multiple resistance to antimicrobial agents, vancomyci n-resistant enterococci and staphylococci represent a major problem fo r the physician. Efforts to avoid their emergence by appropriate antib iotic use and to stop their dissemination by adherence to infection co ntrol practices are needed as few therapeutic alternatives are current ly available.