Fluctuations in antibiotic resistances of gram-negative rods in one hospital, 1961-70, with comment on kanamycin-neomycin relationships.

Records of the percentages of various types of gram-negative rods resistant to six antibiotics are presented for the years 1961 to 1969 with additional notes on 1970. Gross amounts of each antibiotic used in each of the years are also depicted. Resistance-factor transference does not seem to be an important factor but levels of antibiotic usage do seem to affect the percentages of resistant strains found. In the case of kanamycin, extensive use of neomycin appears to have produced much cross-resistance. Free use of polymyxins does not seem to increase resistant percentages.