Kanamycin sulfate was replaced by gentamicin sulfate in an effort to control an outbreak of nosocomial infections caused by enteric organisms with R-factor-mediated kanamycin resistance in an intensive care nursery. Within a month the kanamycin-resistant organisms were essentially eliminated from the nursery, indicating that the selective pressure provided by the extensive use of kanamycin was a major factor in causing and propagating the outbreak. Over a period of observation of 15 months, a significant increase in the gentamicin resistance of the Gram-negative intestinal flora of the infants occurred, but no clinical infections due to gentamicin-resistant enteric organisms were observed.
Franco JA, Eitzman DV, Baer H. Antibiotic Usage and Microbial Resistance in an Intensive Care Nursery. Am J Dis Child. 1973;126(3):318-321. doi:10.1001/archpedi.1973.02110190280006