Characterisation of drug resistance gene cassettes associated with class 1integrons in clinical isolates of Escherichia coli from Taiwan, ROC

The presence of class 1 integrons in clinical isolates of Escherichia coli was detected by PCR, Of 104 E, coli isolates from Kaohsiung, 54 (52%) carri ed class 1 integrons, with inserted DNA regions of 1-3 kb, These integrons were located on plasmids, as demonstrated by Southern hybridisation. DNA se quencing was used to identify the genetic content of the integron-variable regions. Different class 1 integrons contained various numbers, kinds and c ombinations of gene cassettes within their variable regions. These gene cas settes included those encoding resistance to trimethoprim (dfrIa, dfrV, dfr 12 and dfr17), aminoglycosides (aadA1a, aadA2, aadA4 and aadB), chloramphen icol (cmlA), erythromycin (ereA2) and beta -lactams (blaP1), An integron ca rrying three inserted cassettes - dfr12-orfF-aadA2 - was present in 33 (61% ) of the 54 isolates with class 1 integrons, Gene cassettes encoding resist ance were expressed phenotypically, The results indicate that class 1 integ rons are widespread in clinical E, coli isolates in Taiwan, The types, comb inations and frequency of the gene cassettes in integrons may reflect the s pecific selective pressures to which the isolates were exposed and could pr ovide useful surveillance data for relation to antibiotic usage information .