Search for protein cross-reacting with OprD antibodies in Pseudomonas spp. and related species.

susceptibility test were performed on Mueller-Hinton agar with 5% horse blood according to NCCLS recommendations with the following discs: cefuroxime (30/jg), ceftizoxime (30 fig), cefpodoxime (30 /ig), cefixime (30 fig), cefaclor (30 ug) and loracarbef (10 and 30/ig). Agar and discs were from Sanofi Diagnostic Pasteur (Marnes-la-Coquette, France) except loracarbef prepared from standard reference powder (Eli Lilly, Indianpolis, USA). Plates were incubated overnight at 37°C in air. A total of 134 S. pneumoniae were tested: 55 fully susceptible (MIC s£ 0-25 mg/L), 71 intermediate (MIC 0-5-1 mg/L) and 8 resistant (MIC > 1 mg/L) to cefotaxime according to new NCCLS recommendations (Jorgensen et al., 1993). As inferred from the sensitivity and specificity to detect intermediate/resistant strains, results expressed as % agreement with MIC breakpoints at the best discriminating zone size were as follows: loracarbef (10 ug) 94-8%, loracarbef (30 fig) 88-8%, cefaclor 85-1%, cefixime and ceftizoxime 80-6%, cefuroxime 79-1% and cefpodoxime 73-1%. Loracarbef 10/ig discs clearly distinguished cefotaxime intermediate/resistant strains from fully susceptible ones: all the cefotaxime-resistant strains had a zone size of ^7 mm and 94-4% of intermediate strains had a zone size of ^10 mm. Only 2-2% of cefotaxime-susceptible strains had a zone size of ^10 mm (Figure). These data indicate that loracarbef 10 //g discs, at a 10 mm breakpoint have a very good sensitivity and specificity for the detection of S. pneumoniae resistant to extended-spectrum cephalosporins. References Bradley, J. S. (1991). Ceftnaxone failure in meningitis caused by Streptococcus pneumoniae with reduced susceptibility to /J-lactam antibiotics. Genetics of oxacillin resistance in clinical isolates o(Streptococcus pneumoniae that are oxacillin resistant and pencillin susceptible. (1993a). Screening for cephalosporin-resistant Streptococcus pneumoniae with the Kirby-Bauer disk susceptibility test. in diagnosis and management of cephalosporin-resistant Streptococcus pneumoniae meningitis. (1994). Screening for cephalosporin-resistant Streptococcus pneumoniae with the Kirby-Bauer disk susceptibility test. (1993). Development of quality control and interpretive criteria for antimicrobial susceptibility testing of Streptococcus pneumoniae. Cephalosporin treatment failure in penicillin-and cephalosporin-resistant Streptococcus pneumoniae meningitis. Sir, Imipenem penetrates the outer membrane of Gram-negative bacteria through porin proteins It has been shown that the good activity of imipenem against Pseu-domonas aeruginosa is related to its preferential penetration through the protein OprD (formerly D2, Huang & Hancock, 1993) and that acquired resistance to imipenem in this species is mainly associated with a loss of the protein OprD (Trias & Nikaido, 1990). Recently, we showed that all of 61 clinical strains of P. aeruginosa resistant to …