title: Susceptibility profiles of Nocardia isolates based on current taxonomy.
abstract: The genus Nocardia has undergone rapid taxonomic expansion in recent years, and an increasing number of species are recognized as human pathogens. Many established species have predictable antimicrobial susceptibility profiles, but sufficient information is often not available for recently described organisms. Additionally, the effectiveness of sulfonamides as first-line drugs for Nocardia has recently been questioned. This led us to review antimicrobial susceptibility patterns for a large number of molecularly identified clinical isolates. Susceptibility results were available for 1,299 isolates representing 39 different species or complexes, including 11 that were newly described, during a 6-year study period. All tested isolates were susceptible to linezolid. Resistance to trimethoprim-sulfamethoxazole (TMP-SMX) was rare (2%) except among Nocardia pseudobrasiliensis (31%) strains and strains of the N. transvalensis complex (19%). Imipenem susceptibility varied for N. cyriacigeorgica and N. farcinica, as did ceftriaxone susceptibility of the N. nova complex. Resistance to more than one of the most commonly used drugs (amikacin, ceftriaxone, TMP-SMX, and imipenem) was highest for N. pseudobrasiliensis (100%), N. transvalensis complex (83%), N. farcinica (68%), N. puris (57%), N. brasiliensis (51%), N. aobensis (50%), and N. amikacinitolerans (43%). Thus, while antimicrobial resistance can often be predicted, susceptibility testing should still be considered when combination therapy is warranted, for less well characterized species or those with variable susceptibility profiles, and for patients with TMP-SMX intolerance.
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, ARUP Laboratories, Salt Lake City, Utah, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Schlaberg
authors.forename: Mark A
authors.initials: MA
authors.lastname: Fisher
authors.forename: Kimberley E
authors.initials: KE
authors.lastname: Hanson
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000583:Amikacin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002443:Ceftriaxone / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D000069349:Linezolid; D008826:Microbial Sensitivity Tests; D009615:Nocardia / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D009617:Nocardia Infections / Q000188:drug therapy / Q000382:microbiology; D023303:Oxazolidinones / Q000494:pharmacology; D010802:Phylogeny; D013045:Species Specificity; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology
chemical_list: D000081:Acetamides; D000900:Anti-Bacterial Agents; D023303:Oxazolidinones; D015378:Imipenem; D002443:Ceftriaxone; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D000583:Amikacin; D000069349:Linezolid