susceptibilities of 39 isolates of Nocardia spp., including 26 strains of Nocardia asteroides (1). Three investigational fluoroquinolones, PD 117558, PD 117596, ...
ANTIMICROBIAL AGENrS AND CHEMOTHERAPY, Nov. 1993, p. 2515 0066-4804/93/112515-01$02.00/0
Vol. 37, No. 11
Letter to the Editor Antimicrobial Susceptibilities of Nocardia Khardori and colleagues recently reported the in vitro susceptibilities of 39 isolates of Nocardia spp., including 26 strains of Nocardia asteroides (1). Three investigational fluoroquinolones, PD 117558, PD 117596, and PD 127391; two investigational aminoglycosides, SCH 21420 and SCH 22591; and a cephamycin, cefmetazole, all had good in vitro activities against the isolates of N. asteroides. These antibiotics may show promise as alternative therapies when standard therapy with a sulfonamide or trimethoprim-sulfamethoxazole is not tolerated or is ineffective. Unfortunately, cefmetazole is the only currently available alternative, and it must be administered parenterally. Only the investigational fluoroquinolones may offer alternative oral therapy. N. asteroides complex is now known to contain several species, some of which can be differentiated by their antibiotic susceptibility patterns. Approximately 20% of N. asteroides spp. are composed of Nocardia farcinica, which is characterized by resistance to cefotaxime, ceftriaxone, and cefamandole (4, 5). Nocardia nova also makes up approximately 20% of N. asteroides spp., and it is characterized by susceptibilities to ampicillin and erythromycin (3, 4). The value of accurate identification and complete susceptibility testing of N. asteroides spp. was recently illustrated in a case report of pneumonia following cardiac transplantation caused by N. nova and Aspergillus fumigatus (2). The patient was successfully treated for the nocardial component of his disease with clarithromycin when sulfisoxazole therapy was not tolerated. The macrolide antibiotics erythromycin, clarithromycin, and azithromycin may currently offer alternative oral therapy for patients with infections caused by N. nova in whom standard therapy is not tolerated or is ineffective. It would be of great utility to the clinician if susceptibility studies of N. asteroides complex would include species
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identification and results for the cardinal antibiotics, allowing for susceptibility grouping (extended-spectrum cephalosporins, ampicillin, and macrolides). This additional information would allow statements concerning alternative antibiotic therapy with both approved and investigational agents to result in increasing clinical benefits as experience is accumulated. REFERENCES 1. Khardori, N., R. Shawar, R. Gupta, B. Rosenbaum, and K. Rolston. 1993. In vitro antimicrobial susceptibilities of Nocardia species. Antimicrob. Agents Chemother. 37:882-884. 2. Monteforte, J. S., and C. A. Wood. 1993. Pneumonia caused by Nocardia nova and Aspergillus fumigatus after cardiac transplantation. Eur. J. Clin. Microbiol. Infect. Dis. 12:112-114. 3. Wallace, R. J., Jr., B. A. Brown, M. Tsukamura, J. M. Brown, and G. 0. Onyi. 1991. Clinical and laboratory features of Nocardia nova. J. Clin. Microbiol. 29:2407-2411. 4. Wallace, R. J., Jr., L. C. Steele, G. Sumter, and J. M. Smith. 1988. Antimicrobial susceptibility patterns of Nocardia asteroides. Antimicrob. Agents Chemother. 32:1776-1779. 5. Wallace, R. J., Jr., M. Tsukamura, B. A. Brown, J. Brown, V. A. Steingrube, Y. Zhang, and D. R. Nash. 1990. Cefotaxime-resistant Nocardia asteroides strains are isolates of the controversial species Nocardia farcinica. J. Clin. Microbiol. 28:2726-2732.
Craig A. Wood Division of Infectious Diseases Hahnemann University Philadelphia, Pennsylvania 19102-1192
Ed. Note: There is currently a need to increase our understanding of the relative antimicrobial susceptibilities of species composing the Nocardia asteroides complex. Such information could be useful in choosing the appropriate antimicrobial therapy for infections caused by these organisms. The above letter to the editor addresses this issue.
