resistance was most frequent to penicillin ( 70 % of all isolates ) , ampicillin ( 49 % ) , and carbenicillin ( 32 % ) and was concluded to be related to the concentrations of the individual antibiotics in the disks used for assaying resistance and to the production of low levels of beta-lactamase .
C0030842
penicillin
C0006976
carbenicillin