Pii: S0732-8893(00)00161-9

A proficiency testing project was conducted among 48 microbiology laboratories participating in Project ICARE (Intensive Care Antimicrobial Resistance Epidemiology). All laboratories correctly identified the Staphylococcus aureus challenge strain as oxacillinresistant and an Enterococcus faecium strain as vancomycin-resistant. Thirty-one (97%) of 32 laboratories correctly reported the Streptococcus pneumoniae strain as erythromycin-resistant. All laboratories testing the Pseudomonas aeruginosa strain against ciprofloxacin or ofloxacin correctly reported the organism as resistant. Of 40 laboratories, 30 (75%) correctly reported resistant MICs or zone sizes for the imipenemand meropenem-resistant Serratia marcescens. For the extended-spectrum b-lactamase (ESBL)-producing strain of Klebsiella pneumoniae, 18 (42%) of 43 laboratories testing ceftazidime correctly reported ceftazidime MICs in the resistant range. These results suggest that current testing generally produces accurate results, although some laboratories have difficulty detecting resistance to carbapenems and extended-spectrum cephalosporins. This highlights the need for monitoring how well susceptibility test systems in clinical laboratories detect emerging resistance. © 2000 Elsevier Science Inc. All rights reserved.