title: Antimicrobial susceptibility patterns of Nocardia asteroides.
abstract: Testing of the susceptibility to 12 antimicrobial agents, including beta-lactams, aminoglycosides, ciprofloxacin, and erythromycin, was performed by broth microdilution on 78 consecutive clinical isolates of Nocardia asteroides. Surprisingly, a limited number of patterns of susceptibility were identified that included all drug classes, with 95% of isolates exhibiting one of five patterns. One group (17%) exhibited resistance to the broad-spectrum cephalosporins, one group (18%) was susceptible to both ampicillin and erythromycin, one group (17%) was susceptible to ampicillin and carbenicillin but intermediate in susceptibility to imipenem, and the most common group (35%) was resistant to ampicillin but susceptible to the broad-spectrum cephalosporins and imipenem. The most active parenteral agents were amikacin (95%), imipenem (88%), ceftriaxone (82%), and cefotaxime (82%), while the most active oral agents were the sulfonamides (100%), minocycline (100%), and ampicillin (40%). Additional studies are needed to determine whether differences in beta-lactamases relate to varying beta-lactam resistance and whether taxonomic differences that correlate with the different susceptibility groups can be identified.
authors.affiliation: Department of Microbiology, University of Texas Health Center, Tyler 75710.
authors.forename: R J
authors.initials: RJ
authors.lastname: Wallace
authors.forename: L C
authors.initials: LC
authors.lastname: Steele
authors.forename: G
authors.initials: G
authors.lastname: Sumter
authors.forename: J M
authors.initials: JM
authors.lastname: Smith
mesh_terms: D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D009617:Nocardia Infections / Q000382:microbiology; D009616:Nocardia asteroides / Q000187:drug effects*; D013420:Sulfamethoxazole / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D013420:Sulfamethoxazole