Laboratory capacity to detect antimicrobial resistance, 1998.

Emerging mechanisms of antimicrobial resistance have clinical, microbiologic, and infection-control implications for health-care providers. Antimicrobial resistant organisms include Staphylococcus aureus with reduced susceptibility to vancomycin (minimum inhibitory concentration [MIC] > or = 4 microg/mL), including vancomycin intermediate S. aureus (VISA; vancomycin MIC = 8-16 microg/mL) and Enterobacteriaceae that produce extended spectrum beta-lactamases (ESBLS), which result in resistance to a broad range of beta-lactam antibiotics. Detecting VISA and ESBLs-producing gram-negative pathogens can be difficult for clinical microbiology laboratories. Although CDC and the National Committee for Clinical Laboratory Standards (NCCLS) have published screening and confirmatory methods for these pathogens (Tables 1 and 2), the extent of use of these methods is unknown. This report summarizes results from a survey of microbiology laboratories that participate in the Active Bacterial Core Surveillance (ABCs)/Emerging Infections Program (EIP) Network to assess the capacity of clinical microbiology laboratories to detect VISA and ESBL-producing pathogens; findings indicate that despite adequate capacity for proper testing, many laboratories do not have appropriate methodology to detect these resistant pathogens.