The antibiotic susceptibilities of 16 clinical isolates of Aeromonas hydrophila obtained from cancer patients with septicemia were studied. Of the new 1-lactam antibiotics tested, azthreonam and moxalactam were the most active, followed by cefoperazone, cefotaxime, and ceftizoxime. Excellent activity was demonstrated by chloroamphenicol, tetracycline, aminoglycosides, and trimethoprim-sulfamethoxazole. Semisynthetic penicillins had no appreciable activity against this organism.

Thienamycin, a new beta-lactam antibiotic, exhibited potent, broad-spectrum activity in vitro against gram-negative bacilli and gram-positive cocci, including many isolates resistant to currently available antibiotics. All isolates were inhibited at concentrations les than or equal to 25 yg/ml, with the exception of 12% Ill., abstr. no. 228, 1976). This study was undertaken to confirm these observations and add data which compare this drug with carbenicillin, ticarcillin, and amoxicilhin, which are in current use, and with the investigational drugs apalcillin

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Mezlocillin is a new broad-spectrum semisynthetic penicillin that has shown encouraging in vitro activity against the infecting organisms most likely to cause mortality and morbidity in cancer patients receiving chemotherapy. The serum clearances and urine recoveries of mezlocillin, ampicillin, and carbenicillin were compared after the intravenous administration of single 3-g doses. The peak mean serum concentrations of mezlocillin and carbenicillin were 269 and 278 ,ug/ml, respectively, whereas the peak ampicillin level was lower at 167 ,ug/ml. The terminal half-life of mezlocillin, 66 min, was not significantly different from those of ampicillin and carbencillin (63 and 77 min, respectively). Recoveries of mezlocillin, ampicillin, and carbenicillin from urine over 6-h periods after drug dosage were 45, 61, and 80%, respectively. A further study in 11 cancer patients examined serum maintenance levels of mezlocillin when 3-g doses were given intravenously every 4 h for at least 7 consecutive days. After 3 days of therapy, the mean serum concentrations were maintained above 50 ,ug/ml. Although therapeutic efficacy was not an objective of this study, all of three documented bacterial infections were cured, and no serious toxicity was encountered.