In vitro antimicrobial susceptibility studies using amikacin and ticarcillin, alone and in combination, were performed on 20 strains of Pseudomonas aeruginosa . All strains were susceptible to amikacin, and ticarcillin was active against 16 of the 20 strains. Enhanced anti-pseudomonas activity could be demonstrated with the combination of amikacin and ticarcillin.

A multiply drug-resistant strain of Proteus mirabilis was isolated from 14 patients on a surgical service. Antimicrobial susceptibility studies demonstrated that the organism was highly resistant to numerous antibiotics, including gentamicin, tobramycin, and sisomicin. The organism was susceptible in vitro to amikacin but had low-level resistance to netilmicin. In vitro susceptibility studies with combinations of cephalothin with netilmicin and trimethoprim with sulfamethoxazole showed these drugs to be synergistic. Other drug combinations failed to act synergistically.

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