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Miscellaneous Staphylococcus aureus populations were tested with seven commercialized cephalosporins. The strains were divided in five groups according to the following criteria: penicillinase production or not: sensitivity to methicillin and cephalosporins; RB type resistance to methicillin; RH and RO type resistance to every beta-lactamine (according to Chabbert and Baudens). For each cephalosporin studied, the population cell analysis performed with these different groups showed the constant heterogeneous arrangement of the individual MIC. However, whatever the staphylococcus group, cephaloridine remains the antibiotic that inhibits the largest number of cells at lower concentration than other cephalosporins. In vitro results were compared with pharmacokinetic data of the different cephalosporins.

The cefradine-tobramycine association was used in 11 cases of septicaemia and in 10 cases of non-septicaemic severe poly-infections. In 15 cases, the treatment was undertaken because of the serious state of the patients before the bacteriologic results were known. This association is characterized by its great effectiveness and its very good tolerance, mainly from the renal point of view. The results shown here corroborate those two elements.

This report discusses the differences in enzymes of two populations of P. aeruginosa, one sensitive and the other resistant to carbenicillin, which were strains isolated from four patients with chronic urinary infections. These sensitive and resistant strains biosynthetize only one beta-lactamase which appears to be a cephalosporinase of the class Id of Richmond and Sykes (1973). In the four cases the bacterial resistance to carbenicillin does not involve a new beta-lactamase and is due to other factors.