The activities of ciprofloxacin and norfloxacin against 100 mycobacteria isolates were studied in vitro by the 1% standard proportion method. Ciprofloxacin was more active against M. tuberculosis and M. fortuitum with MICs of 1.0 and 0.25 ,ug/ml, respectively, against 90% of isolates; norfloxacin had MICs of 8.0 and 2.0 ,ug/ml, respectively, against 90% of isolates.

The BACTEC system and three conventional media (Middlebrook 7H10, selective Middlebrook 7H11 [S7H11], and Lowenstein-Jensen [LJ]) were compared for their mean recovery times and recovery rates of mycobacteria from acid-fast, smear-negative clinical specimens. Of the 71 smear-negative, culturepositive specimens recovered from 2,165 submitted smear-negative cultures, the BACTEC system detected 71.8%, compared with 88.7% for the conventional three-medium system. When media were individually compared, BACTEC medium (Middlebrook 7H12) was more successful in recovering mycobacteria (71.8%) than was LJ (62%), Middlebrook medium 7H10 (55.9%), or Middlebrook S7H11 medium (52.1%). Middlebrook 7H11 medium containing sodium selenate was also evaluated and did not increase the recovery rate or decrease the recovery time of mycobacterial species when compared with LJ, Middlebrook 7H10, S7H11, and 7H12 media. The mean detection time for the BACTEC system was less than that by conventional methods for the seven species of mycobacteria recovered. Detection times for Mycobacterium tuberculosis on the BACTEC system and conventional cultural systems were 13.7 and 26.3 days, respectively.

Strains of Mycobacterium avium-intracellulare complex often exhibit in vitro resistance to common antimycobacterial agents. Combinations of etambutol, isoniazid, kanamycin, rifampin, and streptomycin were tested to determine if synergism occurred. Ninety-six percent of the strains were susceptible to a combination of ethambutol and rifampin at concentrations attainable clinically. Other combinations of antimycobacterial agents inhibited 4 to 82% of the isolates tested.

Identification of routine mycobacterial isolates by gas-liquid chromatography profile analysis was performed on 335 strains received at the Mayo Clinic over a 10-month period. Comparison of identification by gas-liquid chromatography versus conventional biochemical profiles was made. The two methods agreed on the identification of 320 isolates, with gas-liquid chromatography profiling making eight errors and biochemical profiling making four errors. In three cases, discrepancies could not be resolved.

A total of 332 major pathogenic fungi were isolated from specimens cultured onto both fungal culture media and media used for culturing mycobacteria from January 1968 to June 1975. Only 72 (21.7%) fungi were recovered on media used for culturing mycobacteria. The effect of sodium hydroxide treatment was evaluated and shown to be detrimental to the recovery of fungi. It is recommended that clinical laboratories not rely on mycobacteriological cultures to recover fungal pathogens.