SDS-PAGE for identification of species belonging to the Mycobacterium fortuitum complex.

We performed a study to determine the usefulness of SDS-PAGE of whole cell proteins for the characterization of species of rapidly growing mycobacteria belonging to the Mycobacterium fortuitum complex. Strains included 37 M. fortuitum, 32 M. chelonae, 10 M. peregrinum, 5 M. abscessus, and 3 M. mucogenicum. Eight collection strains (including type strains of the five species) were also included in the study. All strains yielded between 44 and 58 bands in the electrophoretograms. Intraspecies similarity showed Dice coefficients higher than 95%, with only one strain of M. fortuitum having a six-band difference (Dice coefficient 87.75%). However, interspecies similarity was always below 75%, the similarity being higher between M. fortuitum and M. peregrinum (75.51%) and between M. chelonae and M. abscessus (54.9%). Visual examination of the electrophoretograms was sufficient for species characterization. SDS-PAGE of whole cell proteins is a useful technique for identification of isolates of the M. fortuitum complex, and is easy to perform without the need for complex or expensive equipment.

A comparison between disk diffusion and microdilution for susceptibility testing of Mycobacterium fortuitum complex.

We evaluated a disk diffusion method using Mueller-Hinton agar for susceptibility testing of Mycobacterium fortuitum complex organisms. Ninety-five strains were tested both by broth microdilution and disk diffusion. Global results showed good correlation for all antimicrobials except for clarithromycin and erythromycin. However, when the results were analyzed according to species, correlation was poor except for a few antimicrobials. The analysis of the resistant/susceptible results was good for all the antimicrobials tested except azithromycin and erythromycin. In conclusion, the disk diffusion technique could be useful as a screening technique for some antibiotics, but the results must be confirmed by using an accepted reference technique.

In vitro activity of gemifloxacin (SB-265805) compared with 14 other antimicrobials against intestinal pathogens.

We studied the in vitro activity of gemifloxacin (SB-265805) and 14 comparator antimicrobials against 288 recent isolates of enteropathogenic bacteria (106 Salmonella: spp., 32 Hafnia alvei, 22 Yersinia enterocolitica, 21 Shigella: spp., 16 Aeromonas: spp. and 91 Campylobacter jejuni). Gemifloxacin, the other fluoroquinolones and cefotaxime were very active against all microorganisms tested except for C. jejuni. Seventy-seven per cent of isolates of C. jejuni were inhibited by erythromycin < or =0.5 mg/L. Only one strain of C. jejuni was highly resistant to this antimicrobial agent. Of the compounds tested, gentamicin was the most active in vitro. The in vitro activity of the other antibiotics tested was variable. A quinolone could be a good choice for treating gastrointestinal infections when antimicrobial therapy is indicated. For C. jejuni, another antibiotic such as erythromycin should be considered.

Usefulness of the BACTEC MYCO/F lytic system for detection of mycobacteremia in a clinical microbiology laboratory.

278 BACTEC MYCO/F lytic system blood cultures for mycobacteria were evaluated between 1997 and 1999. Sixty of them were read as positive by the system, being considered 15 of them as false positives. Twenty-seven yielded mycobacterial growth (13 Mycobacterium avium from 3 patients and 14 Mycobacterium tuberculosis from 8 patients). Other bacteria isolated were coagulase-negative Staphylococcus (13 samples), Corynebacterium sp. (5 samples), Salmonella enteritidis (2 samples) and Klebsiella pneumoniae (1 sample). Five of these isolates were considered as true episodes of bacteremia. The average time for detection of mycobacteria was 12.6 days for M. avium and 26.4 days for M. tuberculosis. BACTEC MYCO/F lytic system is useful for detection of mycobacteremia in clinical microbiology laboratories.

In vitro susceptibilities of rapidly growing mycobacteria to telithromycin (HMR 3647) and seven other antimicrobials.

The antimicrobial activities of telithromycin (HMR 3647) and seven other antimicrobials against 94 strains of rapidly growing mycobacteria were determined. Telithromycin at a concentration of 1 microg/ml inhibited Mycobacterium peregrinum (100%), Mycobacterium chelonae (80%), Mycobacterium abscessus-Mycobacterium mucogenicum (44.4%), and Mycobacterium fortuitum (2.1%). All or most strains of M. peregrinum, M. fortuitum, and M. mucogenicum were inhibited by 2 microg of quinolones per ml.