Cross-resistance between some aminoglycoside antibiotics

The cross-resistance between the aminoglycoside antibiotics, gentamycin, tobramycin, kanamycin and streptomycin was tested using clinical isolates of Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus obtained from Ahmadu Bello University Teaching Hospital Zaria, Nigeria (ABUTH). The antibiotics can be classified into two groups: the kanamycin and streptomycin group on one hand to which isolates easily acquired resistance, and the amikacin, gentamycin and tobramycin group on the other to which the isolates did not easily develop resistance. There seems not to be any hard and fast rule that can be applied to the cross-resistance between these aminoglycoside antibiotics. The isolates varied markedly in their pattern of cross-resistance towards the different antibiotics.