RESUMEN
The present study was carried out with 111 multiresistant pathogenic strains of enterobacterias isolated from different sources with increased resistance to three or more antibiotics. Among the identified species are included E. coli, Shigella sp., Salmonella oranienburg, Klebsiella pneumoniae and Citrobacter freundii. In general, the minimal inhibitory concentration of antibiotics was above 100 microgram/ml and in some cases it was superior to 1000 microgram/ml. Resistance transfer factors were detected in 72% of the strains; 33% movilized the complete pattern of resistance and 67% did it partially because some of the determinants were not transfered. The Citrobacter strains show a high frequency of transference (10(-1)), while for the others species it was in the order of 10(-2)--10(-3). The use of a multi-inoculator allows to perform in a simple way the preliminar evaluation about the presence or absence of R transfer factors in multiresistant strains. This technique has shown good correlation with the data obtained by the usual dilution and plating method.