Susceptibility and Cross-Resistance of Bacteria to Four Related Antibiotics

Abstract

Summary and conclusions

The antibiotics kanamycin, paromomycin and neomycin were shown to have essentially the same activity in vitro against strains of Staphylococcus aureus and of various Enterobacteriaceae. Bacteria made resistant to any one of these 3 antibiotics by subcultures on that antibiotic also exhibit virtually complete cross-resistance to the other two. Organisms isolated from infected sources do not show significant cross-resistance between streptomycin and any of these 3 antibiotics. However, strains made resistant in vitro to either kanamycin, paromomycin or neomycin show moderate increases in resistance to streptomycin, and strains made resistant to the latter exhibit only minor increases in resistance to the other 3 antibiotics. With all 4 antibiotics, corresponding parent and resistant variants of the staphylococci were of the same phage type, and resistant variants of K. pneumoniae and E. coli retained their serological specificity. Fecal organisms isolated from patients during oral treatment with paromomycin or kanamycin were resistant to the antibiotic administered and showed moderate to marked resistance also to the other one and to neomycin.