Hk Agar (kyokuto, Tokyo) Supplemented with 5% Laked Sheep at 37њc for 7 Days in an Anaerobic Chamber (co 2 Concentration

to the final endpoint was not observed for the antimicrobial agents Actinomyces species and Propionibacterium propionicus are tested in this study. well-known causes of actinomycosis. Because histological examiBecause of differences in the experimental conditions, the nation plays a pivotal role in the recognition of actinomycosis, NCCLS (National Committee for Clinical Laboratory Standards) isolation and identification of the causative bacteria as well as breakpoint should not be applied directly to our results. However, susceptibility testing are rarely performed routinely by laboratories we needed a standard to interpret the data. Thus, we used the in Japan. Penicillins have been used as effective agents in empirical susceptibility breakpoints of the NCCLS as a reference standard chemotherapy. Owing to the excellent activity of the new quinoin table 1. The susceptibility breakpoints used were those described lones against numerous aerobic bacteria, including b-lactamase– in the standards M7-A2, M11-A, and M100-S4 established by the producing strains, these drugs are being used increasingly for a NCCLS. For the data on the new quinolones, which were tested variety of infections, including those of the eye, in Japan. We by the agar dilution method, an MIC value (3.13 mg/mL) comparafound several reports on susceptibility to the new quinolones, but ble to the NCCLS breakpoint for ofloxacin (2 mg/mL) was adopted. reports on the antimicrobial activity of these agents against slowTable 1 shows the results we obtained with the broth microdilugrowing species such as Actinomyces species are rare. We recently tion method. Actinomyces species and P. propionicus had similar encountered two patients with lacrimal canaliculitis and one with susceptibility profiles. These isolates were generally susceptible to an ear infection caused by P. propionicus or Actinomyces species. ampicillin, oxacillin, cefazolin, cefmetazole, cefoperazone, minoWe tested the antimicrobial susceptibility of these strains by using cycline, and clindamycin, but less susceptible to amikacin. These the broth microdilution method and found that ofloxacin had a low results agree with the data reported by Holmberg et al. [2], Schaal, level of activity against them. We used some reference strains and Niederau et al. [3], Wade [4], and Cullmann et al. [5]. Aztreonam clinical isolates, and reassessed the susceptibility of Actinomyces and ofloxacin had poor activity against these strains. Fosfomycin species and P. propionicus to antimicrobial agents, including these also showed poor activity (MIC, from 16 mg/mL to ú32 mg/mL). new drugs. All strains of Actinomyces species examined were susceptible to The strains used were as follows: three strains of Actinomyces ceftazidime, but three of five P. propionicus strains were intermediisraelii (NCTC [National Collection of Type Cultures] 10215 and ately susceptible to resistant to this drug. two clinical isolates); two strains of Actinomyces gerencseriae Table 2 shows the susceptibility of the isolates to seven new (formerly A. israelii serovar II) (DSM [Deutsche Sammlung von quinolones. A. israelii and A. gerencseriae had almost the same Mikroorganismen und Zellkulturen GmbH] 6844 and one clinical susceptibility profiles when tested against these quinolones and isolate); three strains of Actinomyces naeslundii (JCM [Japan Colother agents examined by the broth microdilution method. These lection of Microorganisms] 8349, JCM8350, and one clinical isoisolates were generally less susceptible or resistant to all new late); and Actinomyces viscosus JCM8353 and five strains of quinolones tested except DU6859a. The susceptibility profiles of P. propionicus (DSM43015, DSM43307 and three clinical isolates). Susceptibility to several antimicrobial agents was determined by the broth microdilution method with dry plates containing a series of lyophilized drugs (Sensimic, Terumo, Tokyo). Table 1. Susceptibilities of Actinomyces species and PropionibacteThe organisms were suspended in ABCM broth (Eiken Kagaku, rium propionicus to 14 antimicrobial agents, as determined by the Tokyo) and inoculated at a concentration of 10 cfu per well. The broth microdilution method. plates were incubated anaerobically at 377C for 7 days with use of the AnaeroPack system (CO2 concentration, 20%; Mitsubishi No. of strains for which Gas Chemical, Tokyo). MIC range indicated MIC was Agent (MIC value in mg/mL) (mg/mL) determined* Susceptibility to seven new quinolones was examined by using an agar dilution method, as described previously [1], with brucella Ampicillin (£2, 4, §8) £0.25 13, 0, 0 HK agar (Kyokuto, Tokyo) supplemented with 5% laked sheep Oxacillin (£1, 2, §4) £0.25–1 13, 0, 0 blood as testing medium. The plates were incubated anaerobically Cefazolin (£4, 8, §16) £0.5–1 13, 0, 0 at 377C for 7 days in an anaerobic chamber (CO2 concentration, Cefmetazole (£16, 32, ú32) £0.5–2 13, 0, 0 10%; Hirasawa, Tokyo). A longer incubation time and higher conCefoperazone (£16, 32, ú32) £0.5 13, 0, 0 centration (10 cfu per well) were required for good growth and Ceftazidime (£4, 8, §16) £0.5–32 10, 0, 3 to clarify the endpoints. The effect of the extended incubation time Aztreonam (£4, 8, §16) 4–õ32 1, 1, 11 Amikacin (£8, 16, §32) £1–õ32 2, 4, 7 Minocycline (£4, 8, §16) £0.5–4 13, 0, 0 Clindamycin (£2, 4, §8) £0.25–0.5 13, 0, 0 Erythromycin (£0.25, 0.5, §1) £0.25–1 11, 1, 1 Reprints or correspondence: Dr. Kunitomo Watanabe, Institute of Anaerobic Ofloxacin (£1, 2, §4) 4–õ16 0, 0, 13 Bacteriology, Gifu University School of Medicine, 40 Tsukasa-machi, Gifu, Vancomycin (£2, 4, §8) 2–8 5, 5, 3 500 Japan. NOTE. The following isolates were tested: A. israelii, 2 strains; A. gerencClinical Infectious Diseases 1997;25(Suppl 2):S262–3 seriae, 2 strains; A. naeslundii/viscosus, 4 strains; and P. propionicus, 5 strains. q 1997 by The University of Chicago. All rights reserved. 1058–4838/97/2503–0055$03.00 * Refers to column 1.