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Arch Hellen Med, 23(1), January-February 2006, 45-51


Class 1 integrons in Enterobacteriaceae from farm animals,
hospitalized and non-hospitalized patients


1"G.K. Daikos" Infectious Diseases Research Laboratory, 1st Department of Propedeutic Medicine, Medical School of Athens, Athens,
2Department of Clinical Microbiology, "Laikon" General Hospital, Athens,
3Department of Microbiology, Medical School of Athens,
4Technological Institution of Athens,
5Veterinary Laboratory of Chalkida, Chalkida, Greece

OBJECTIVE Class 1 integrons are DNA structures that recognize and capture mobile gene cassettes. A considerable portion of the genes encoding antibiotic resistance is integrated into these DNA elements. This study aimed to detect and compare class 1 integrons in Enterobacteriaceae from farm animals and hospitalized and non-hospitalized patients.

METHOD Two hundred clinical isolates of Enterobacteriaceae causing human infection or colonization were collected between May and November 2003, 100 from patients hospitalized for more than 72 hours (hospital acquired, HA) and 100 from outpatients with no prior hospitalization in the preceding 4 months (community acquired, CA). Fifty-seven Enterobacteriaceae isolates were collected from farm animals (FA) during the same period. The microorganisms were identified using a standardized identification system and their susceptibilities to commonly used antibiotics were determined by the Kirby-Bauer and broth microdilution MIC methods according to NCCLS guidelines. The presence of class 1 integrons was detected by amplifying the integrase 1 gene, and their size was calculated by amplifying the variable regions. Similarities between the microorganisms were identified by pulsed field gel electrophoresis of their genomes after digestion by XbaI and similarities between the integrons were studied after sequencing of the variable regions.

RESULTS The rate of integron 1 carriage was 50.8% for FA Enterobacteriaceae, 21% for HA and 11% for CA. The size range of the variable region was 600-3300 bp, 800-2500 bp, and 800-1500 bp for HA, FA and CA integrons, respectively. The 800 bp variable regions of three integrons detected in three different E. coli isolates of hospital, community and animal origin carried an identical gene cassette (aadA1) and the 1400 bp variable regions of three different E. coli isolates of hospital, community and animal origin were identical, carrying the genes aadA and dfrI. The prevalence of class 1 integrons in multiresistant Enterobacteriaceae was 53.8% while no integron was detected among the sensitive isolates.

CONCLUSIONS The highest prevalence of class 1 integrons was detected among FA Enterobacteriaceae. The HA integrons harboured the longest variable regions. Identical integrons were found in human and animal microorganisms. The antibiotic resistance profile is associated with the presence of integrons.

Key words: Class 1 integron, ┼nterobacteriaceae, Resistance gene.

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