not be detected could be divided into two categories those which were already resistant to the indicator antibiotics and further induction was undetectable and those in which even though susceptible to the indicator induction could not be demonstrated the described method is the first successful rapid detection of inducible class 1 u03b2 lactamases the rate of success for the majority of taxa tested is comparable to that of the overnight method table 1______________________________________the u03b2 lactam family of antibiotice sup a______________________________________penicillins cephalosporins cephamycins benzylpenicillin cephalothin cefoxitin methicillin cefamandole cefotetan ampicillin cefuroxime cefmetazole carbenicillin cefotaxime mezlocillin ceftriaxone piperacillin ceftazidime carbapenems monobactams imipenem aztreonam______________________________________ sup a limited examples in each group are given table 2______________________________________group 1 distribution and numbers of isolates testedclass 1 u03b2 lactamase total wild producers tested types mutants______________________________________ aeromonas hydrophila group 15 15 0 citrobacter freundii 48 35 13 enterobacter aerogenes 25 19 6 enterobacter agglomerans 4 4 0 enterobacter cloacae 30 20 10 morganella morganii 25 19 6 proteus vulgaris 20 16 2 providencia rettgeri 16 16 0 providencia stuartii 16 10 6 pseudomonas aeruginosa 32 26 6 other pseudomonas spp 17 4 13 serratia liquefaciens 20 20 0 serratia marscescens 25 20 5 xanthomonas maltophilia 6 4 2.