1981 Volume 22 Issue 1 Pages 1-7_1
Salmonella and E. coli strains, isolated from broiler chickens over the periods May 1974 to March 1975 (Period I) and May 1978 to March 1979 (Period II), were investigated and compared with respect to drug resistance.
In period I, 98% of the Salmonella strains and all of the E. coli strains were resistant to one or more drugs, while in period II, 75% of the former and 98.1% of the latter were resistant to at least one drug. The frequencies (%) of the individual drug resistances in the Salmonella strains were as follows (figures for period II in parentheses): tetracycline 66 (17), streptomycin 43 (16), sulfisoxazole 84 (59), chloramphenicol 13 (0), kanamycin 15 (38), ampicillin 10 (8), cephaloridine 14 (11), gentamicin 3 (3), furatrizine 90 (37), nalidixic acid 2 (0), and those in the E. coli strains were: tetracycline 93.3 (85.3), streptomycin 69.8 (65.7), sulfisoxazole 86.4 (89.4), chloramphenicol 35.4 (25.7), kanamycin 47.0 (52.8), ampicillin 7.4 (22.2), cephaloridine 5.7 (19.0), gentamicin 3.6 (0.9), furatrizine 93.8 (77.3), nalidixic acid 1.0 (0.7).
These results are of interest in relation to the amended law concerning feed additives enacted in 1975. However, the increasing frequencies of kanamycin and ampicillin resistances together with the prevalence of R plasmids among the E. coli strains suggest that it will be difficult to prevent the spread of drug-resistant bacteria in broiler rearing.
