NEW NOCARDIA TAXON AMONG ISOLATES OF NOCARDIA-BRASILIENSIS ASSOCIATEDWITH INVASIVE DISEASE

Nocardia brasiliensis, the second most frequently isolated aerobic act inomycete in the clinical laboratory, is usually associated with local ized cutaneous infections. However, 22% of 238 N. brasiliensis isolate s from the United States and 12% of 66 isolates from Queensland, Austr alia, which had been collected over a 17-year period, were associated with extracutaneous and/or disseminated diseases, Of the 62 invasive i solates, 37 (60%) were susceptible to ciprofloxacin and/or were suscep tible to clarithromycin and resistant to minocycline, compared with on ly 6 (3%) of 242 localized cutaneous isolates, The 43 isolates with th is susceptibility pattern appeared to define a new taxon, They were si milar to Nocardia asteroides complex isolates clinically in proportion s from persons with pulmonary (70%), central nervous system (23%), and /or disseminated diseases (37%) in the setting of corticosteroids (74% ) or AIDS (14%), This putative new taxon differed from N, brasiliensis in the hydrolysis of adenine (92 versus 4%), beta-lactamase patterns on isoelectric focusing, and the presence of two early mycolic acid-es ter peaks by high-performance liquid chromatography, Restriction analy sis of a 439-bp fragment of the 65-kDa heat shock protein gene reveale d that N, brasiliensis and the new taxon had different restriction pat terns with 8 of the 11 enzymes tested, Screening of invasive isolates of N. brasiliensis for susceptibility to ciprofloxacin will identify m ost isolates of the new taxon, which likely represents a new Nocardia species.