Article

Resistance pattern and assessment of phenicol agents' minimum inhibitory concentration in multiple drug resistant Chryseobacterium isolates from fish and aquatic habitats.

Unité de Virologie et Immunologie Moléculaires, Institut National de la recherche Agronomique, Centre de Recherches de Jouy-en-Josas, Jouy-en-Josas, France.
Journal of Applied Microbiology (impact factor: 2.34). 02/2005; 99(2):323-32. DOI:10.1111/j.1365-2672.2005.02592.x pp.323-32
Source: PubMed

ABSTRACT To assess the susceptibility of Chryseobacterium isolates of fish and aquatic habitats to antimicrobial compounds. Special attention was paid to the resistance to chloramphenicol and florfenicol, a phenicol derivative recently licensed for use in veterinary medicine and fish farming.
Sixty-seven Chryseobacterium spp. isolates and reference strains, originating mainly from different aquatic habitats, were tested using the disk-diffusion method. In addition, agar dilution was used for assessing minimum inhibitory concentration of chloramphenicol and florfenicol. In spite of (i) conditions that hampered properly standardized experiments and (ii) the heterogeneity of the isolates resulting in some aberrant values in diffusion, correlation between the two methods was confirmed. Most of the isolates exhibited considerable multiresistance to most antimicrobial drug families, and many were clearly resistant to phenicols. Molecular investigations conducted on 10 strains selected for high resistance to florfenicol did not establish the existence of floR or cmlA genes currently reported in the literature as responsible for florfenicol resistance. Nevertheless, when an efflux pump inhibitor, phenyl-arginin-beta-naphthylamide, was combined with diffusion tests, drug susceptibility to florfenicol was restored, suggesting that Chryseobacterium's resistance to this molecule is under the control of efflux mechanisms.
Constitutive multiresistance to antibiotics is common in chryseobacteria isolated from the aquatic environment. Although no gene related to the floR family could be detected, efflux mechanisms could partly support the resistance to phenicols.
These results explain the difficulty of treatment and clearly reflect the properties previously reported in Chryseobacterium isolates of human origin. Because several species have been involved in opportunistic infections in humans, the possible role of aquatic organisms as a source of infection should be considered.

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Keywords

aberrant values
 
agar dilution
 
antimicrobial compounds
 
antimicrobial drug families
 
aquatic environment
 
aquatic habitats
 
Chryseobacterium's resistance
 
Constitutive multiresistance
 
different aquatic habitats
 
diffusion tests
 
disk-diffusion method
 
drug susceptibility
 
efflux pump inhibitor
 
florfenicol resistance
 
isolates exhibited considerable multiresistance
 
minimum inhibitory concentration
 
Molecular investigations
 
opportunistic infections
 
possible role
 
two methods
 

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