Vol. 11, 1992 265 -..-_.. All Clostridium difficile strains were susceptible to tosufloxacin, piperacillin, imipenem, metro- nidazole and chloramphenicol (Table 1). The MIC of ciprofloxacin for 50 % of the strains tested Was 8.0 mg/l and for 90 % of the strains 16 mg/1. Ninety percent of the Clostridium perfringens iso- lates were inhibited by 128 mg/1 of cefoxitin and 8 rag/1 of clindamycin. Tosufloxacin was more active than ciprofloxacin against the Bacteroides fragilis strains tested (Table 1). Imipenem was the most active beta-lac- tam agent tested against the isolates. Most strains Were susceptible to piperacillin, cefoxitin and clindamycin, while all of them were susceptible to raetronidazole and chloramphenicol. The other Bactero/des species were also more sus- ceptible to tosufloxacin than ciprofloxacin (Table 1). Imipenem and clindamycin had the highest an- tirnicrobial activities. Piperacillin, cefoxitin and Chloramphenicol were active against all strains tested. Four Bacteroides strains were resistant to metronidazole. All fusobacteria were susceptible to tosufloxacin, piperacillin, cefoxitin, imipenem, clindamycin, metronidazole and chloramphenicol, while a few Strains were resistant to ciprofloxacin (Table 1). The in vitro results presented here indicate that tosufloxacin is a promising new fluoroquinolone Which may be useful in the treatment and prophylaxis of anaerobic infections. Clinical Studies are thus warranted. References 1. FernandesPB, Chu DTW, Swanson RN, Ramer NR, Hanson CW, Bower RR, Stature JM, Hardy DJ: A- 61827 (A-60969), a new fluoronaphthyridine with ac- tivity against both aerobic and anaerobic bacteria. An- timicrobial Agents and Chemotherapy 1988,32: 27-32. 2. Holdeman LV, Cato EP, Moore WEC: Anaerobe laboratory manual, 4th ed. Virginia Polytechnic In- stitute and State University, Blacksburg, VA, 1977, p. 1-156. 3. Dornbusch K, Nord CE, Oisson-Liljequisl B: Anti- biotic susceptibility of anaerobic bacteria with special reference to Bacteroides fragitis. Scandinavian Journal of Infectious Diseases 1979, 19: 17-25. 4. National Committee for Clinical Laboratory Stan- dards: Methods for antimierobial susceptibilitytesting of anaerobic bacteria. 2nd ed. Document Mll-A2. NCCLS, Villanova, PA, 1990. In Vitro Activity of Azithromycin and Tetracycline against 358 Clinical Isolates of Brucella melitensis R. Landfnez 1., J. Lifiares 2, E. Loza 3, J. Mart[nez-Beltr~in 3, R. Martfn 2, E Baquero 3 The in vitro activity of azithromycin against human pathogenic strains of Brucella melitensis was tested at three centres and compared to that of tetracycline, the standard antibiotic currently used for the treatment of human brucellosis. MIC determination was carried out. Tested concentra- tion ranges for both azithromycin and tetra- cycline were between 0.03 and 16/ag/mL Brucella melitensis biotype 1, strain M16 was employed as a control microorganism. A total of 358 Brucella rnelitensis strains from human blood cultures were tested. MIC90 (~g/ml) values ranged from 0.5 to 1.00 for azithromycin and were 0.25 for tetracycline. It was concluded that there was little difference in the sensitivity of pathogenic Brucel- la melitensis to azithromycin and tetracycline iso- lated from three different regions in Spain. These results encourage further investigations on the possible therapeutic role of azithromycin in brucellosis. Current treatment of acute brucellosis combining tetracycline and streptomycin or rifampicin usually achieves excellent clinical and micro- biological results (1-3). Nevertheless, a variable percentage of failures and recurrence are reported in most published series. In addition, these therapeutic regimes pose difficulties in patients' compliance due to their duration; moreover, tetracyclines are contraindicated in children under eight years of age and in pregnant women. Thus, it is felt that new antibiotics over- coming these problems would represent a sig- nificant therapeutic advancement in the treat- ment of brucellosis. 1Departamento de Microbiologfa, Facultad de Medicina, Universidad de Valladolid, Ramon y Cajal, 7, 47005 Val- ladolid, Spain. 2Departamento de Mierobiologfa, Hospital "Pr/neipes de Espafia', Hospitalet de Llobregat, Barcelona, Spain. 3Departamento de Microbiologfa, Hospital 'Ram6n y Cajal", Madrid, Spain.