Differences in susceptibility of Enterobacteriaceae and penicillin-resistant Staphylococcus aureus to tetracycline and minocycline.

Two hundred strains of penicillin-resistant Staphylococcus aureus and 311 isolates of Enterobacteriaceae were compared for their susceptibility to tetracycline and minocycline. Thirteen and one-half percent of the staphylococcal isolates were resistant to tetracycline but susceptible to minocycline. Similarly, 24% of the enterobacterial isolates were found to be tetracycline resistant but susceptible to minocycline. Of a total of 511 recent clinical isolates, 14.5% were susceptible to minocycline but were tetracycline resistant.