Isolation and antimicrobial susceptibility testing of fecal strains of the archaeon Methanobrevibacter smithii.
BACKGROUND
The archaeon Methanobrevibacter smithii is regarded as part of the indigenous microflora of the human intestine but may be connected with pathological conditions. The microbe is extremely oxygen intolerant and is not detectable by anaerobic culture techniques for bacteria. Accordingly, to date quantitative antimicrobial susceptibility data of human isolates are missing.


METHODS
The anoxic Hungate technique and a three-step culture procedure using media supplemented with antibiotics were applied to isolate M. smithii from randomly selected human feces. The minimum inhibitory concentrations (MICs) of 15 isolates and the reference strain DSM 861 were determined using a broth macrodilution test resembling the procedure for testing anaerobic bacteria.


RESULTS
The 16 strains were highly resistant (MICs >64 mg/l) against penicillin G, cephalothin, vancomycin, streptomycin, gentamicin, ciprofloxacin, and clindamycin. Metronidazole inhibited the strains at MICs between 0.5 and 64 mg/l.


CONCLUSIONS
Multiple-antibiotic-resistant Methanoarchaea occur in the human gut. They may be selected during therapy with common antibacterial agents and may be eliminated by the application of metronidazole.
Dermoumi
H L
HL
Institute of Medical Microbiology, University of Essen, Germany.
Ansorg
R A
RA
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D005243:Feces / Q000382:microbiology; D006801:Humans; D017013:Methanobacteriaceae / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D012016:Reference Values
D000900:Anti-Bacterial Agents; D008795:Metronidazole