Broad-spectrum antibiotic resistance of Planctomycetes organisms determined by Etest.
OBJECTIVE
The in vitro susceptibility of Planctomycetes organisms to antibiotics has seldom been studied and when it has, a variety of methods have been used. The objective of the study was to expand the knowledge of Planctomycetes antibiotic susceptibility patterns.


METHODS
Planctomyces maris, Planctomyces brasiliensis, Blastopirellula marina, Planctomyces limnophilus, Gemmata obscuriglobus and Rhodopirellula baltica reference strains were tested for in vitro susceptibility to 18 antibiotics, representing 11 antibiotic families, using the Etest method.


RESULTS
All Planctomycetes organisms were found to be resistant to β-lactams, with MICs of > 32 mg/L for penicillin G and imipenem, and MICs of > 256 mg/L for ampicillin, cefalotin and ceftriaxone. The organisms were resistant to nalidixic acid and vancomycin (MIC > 256 mg/L), but susceptible to tetracycline (MICs < 0.016-0.5 mg/L) and doxycycline (MICs < 0.016-1 mg/L). The MIC of gentamicin ranged from 1 mg/L (P. limnophilus) to > 256 mg/L (B. marina and P. brasiliensis); the MIC of erythromycin ranged from 0.032 mg/L (P. limnophilus) to 2 mg/L (P. brasiliensis); the MIC for ciprofloxacin ranged from 0.008 mg/L (R. baltica) to > 32 mg/L (P. brasiliensis); and the MIC for colistin ranged from 0.125 mg/L (P. limnophilus) to 96 mg/L (B. marina).


CONCLUSIONS
In addition to shedding new light on the biology of Planctomycetes organisms, these data could be used for the further phenotypic characterization of Planctomycetes organisms, and for the optimization of culture media for the primary isolation and growth of Planctomycetes organisms from contaminated specimens.
Cayrou
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C
Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes, UMR CNRS 6236 IRD 3R198, IFR 48, Faculté de Médecine, Université de la Méditerranée, Marseille, France.
Raoult
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D
Drancourt
M
M
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects*; D024881:Drug Resistance, Bacterial; D008826:Microbial Sensitivity Tests; D014871:Water Microbiology
D000900:Anti-Bacterial Agents