The growing number of fungal infections, coupled with emerging resistance to classical antifungal agents, has led to the development of new agents, among them voriconazole. Susceptibility to voriconazole was tested by two microdilution techniques: the National Committee for Clinical Laboratory Standards reference method M38-A and a colorimetric method, Sensititre YeastOne. The study tested a total of 244 isolates: 223 Aspergillus (136 Aspergillus fumigatus, 37 A. niger, 26 A. terreus, 16 A. flavus, 7 A. nidulans, and 1 A. ustus), 14 Fusarium (8 Fusarium moniliformis, and 6 F. oxysporum), 6 Scedosporium apiospermum, and 1 Rhizomucor pusillus strain and four control strains (Candida parapsilosis ATCC 22019, C. krusei ATCC 6258, A. fumigatus ATCC 204305, and A. flavus ATCC 204304). For all tested species except one F. moniliforme strain and R. pusillus, the MIC, the MIC at which 50% of the isolates are inhibited (MIC 50 ), and MIC 90 ranges of <1 g/ml were obtained for voriconazole, indicating excellent activity against these species. The high rate of agreement between the two methods used (97 to 99%) suggests that the Sensititre YeastOne colorimetric method may be a valuable tool for determining the susceptibility of filamentous fungi to voriconazole.

The in vitro susceptibility of Mycobacterium fortuitum and Mycobacterium chelonei to cefmetazole was studied by the agar dilution method. At a concentration of 16 ,ug/ml or lower, 44 isolates (96%) of M. fortuitum and 8 isolates (40%) of M. chelonei were inhibited.Infections caused by atypical mycobactetia, especially those of nosocomial origin, appear to be observed more frequently than in the past. This is particularly true of such rapidly growing mycobacteria as Mycobacterium fortuitum and Mycobacterium chelonei, which have been associated with such human infections as lung disease, subcutaneous abscess, thyroiditis, corneal ulcer, osteomyelytis, septicemia, meningitis, cervical adenitis, and urinary tract infections (9, 16).The major problem with infections caused by rapidly growing mycobacteria is not their diagnosis, which can be accomplished quite simply (11), but rather their treatment. Both M. fortuitum and M. chelonei are very resistant to most antituberculosis agents (10).Although in vitro activity of such antimicrobial agents as amikacin, doxycycline, sulfonamides, and erythromycin against the M. fortuitum complex has been reported (4,7,8,13,15), there is little agreement regarding the therapeutic effectiveness of these agents. Therefore, persons infected with these rapidly growing mycobacteria commonly are treated individually, depending on the antimicrobial agents to which the isolated organism is susceptible. The ,-lactam antibiotics have been shown to be ineffective against M. fortuitum and M. chelonei in vitro (1); however, recent reports have indicated that cefoxitin is active against M. fortuitum (3, 6) but less so against M. chelonei. In this study we investigated the MICs of another cephamycin, cefmetazole, against M. fortuitum and M. chelonei.Isolates was used as a control organism. Cefmetazole was supplied by Antibioticos S.A., Madrid, Spain.Mycobacteria for susceptibility testing were grown for 7 days at 28°C on Dubos oleic agar base (Difco). Aqueous suspensions of the cultures were prepared and diluted with distilled water to a final concentration of about 107 CFU/ml.In each experiment, the initial concentration of organisms was determined by titration and plating in duplicate.Agar dilution testing was performed with Mueller-Hinton agar (Difco). After autoclaving, the agar was cooled to 56°C before the addition of cefmetazole to final concentrations that ranged from 0.25 to 128 ,xg/ml. The agar containing cefmetazole was poured into plates and allowed to solidify overnight. The plates were inoculated with 0.001 ml per spot with a Steers replicator.Plates inoculated with S. aureus and M. fortuitum were incubated at 37°C and examined after 24 and 72 h, respectively. Plates inoculated with M. chelonei were examined after 72 h of incubation at 28°C. The MIC was considered as the lowest concentration that completely inhibited visible bacterial growth.The MIC of cefmetazole for M. fortuitum was generally lower than that for M. chelonei (Table 1). A total of 44 (96%) of the 46 strains of M. for...

The in vitro susceptibility of.Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium africanum, Mycobacterium avium, Mycobacterium fortuitum, and Mycobacterium chelonae (M. chelonei) to ticarcillin in combination with clavulanic acid (CA) was studied by the agar dilution method. All the M. tuberculosis, M. bovis, and M. africanum strains were inhibited at a ticarcillin concentration of 32 ,ug/ml or lower in combination with 5 ,ug of CA. M. chelonae and M. avium strains proved resistant to more than 128 ,ug of ticarcillin plus S ,ug of CA per ml. M. fortuitum strains needed 128 ,ug of ticarcillin plus 5 ,Ig of CA to inhibit approximately 30% of the isolates.Ticarcillin is a semisynthetic penicillin of the carboxypenicillin group with a broad antimicrobial spectrum. Its activity against gram-positive and gram-negative bacteria is bactericidal, inhibiting the synthesis of the cell wall by hindering the formation of alanine-glycine unions of polymers of the peptidoglycans (2, 10, 11).Ticarcillin is inactivated by penicillinases but proves stable against the cephalosporinases. It has been proved synergic with the aminoglycosides against gram-positive and gram-negative bacteria, and its association with clavulanic acid (CA) has also been proved highly useful. This has been shown in many in vitro and in vivo studies with different types of microorganisms (7,8).Until now, its activity against mnycobacteria has not been studied.In this study, an in vitro investigation was done of the activity of ticarcillin in association with CA against Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium inoculated with a Steer replicator with a 1/100 inoculum of the seed suspension in distilled water. The results were read after 2 weeks of incubation at 37°C.The method used to determine MICs for M. fortuitum and M. chelonae was described elsewhere (4). Cultures of the two species were incubated at 37 and 28°C, respectively, for 7 days in Dubos Oleic Agar Base (Difco Laboratories, Detroit, Mich.). Seed suspensions of the cultures were prepared by dilution with distilled water with the organisms scraped off the plate to match a final opacity of a 1 McFarland standard. An inoculum of the seed suspensions diluted 1:1,000 was delivered to Mueller-Hinton agar plates by using a Steer replicator. The antimicrobial concentrations ranged from 0.25 to 128 jig/ml. The results were read after incubation for 2 to 5 days at 37 and 28°C. The MIC was defined as the lowest concentration of antibiotic that completely inhibited visible bacterial growth. M. tuberculosis H37RV was used as the quality control for media without drugs. Staphylococcus aureus ATCC 25923 (Difco) and Escherichia coli ATCC 25922 (Difco) were used as controls for the MIC and diffusion methods. S. aureus 48, betalactamase producing, resistant to ticarcillin, and susceptible to ticarcillin plus CA, was used.The plates with CA were prepared the day that they were used.

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