The Journal of Medical Microbiology, Vol 21, Issue 3 203-207, Copyright © 1986 by Society for General Microbiology
Cefoxitin sensitivity as a marker for inducible beta-lactamases
V. A. Moritz and P. B. Carson
Inducibility of beta-lactamase activity by cefoxitin was examined in 626
gram-negative clinical isolates selected for amoxycillin and cephalothin
resistance. The results indicated that precise identification and cefoxitin
sensitivity or resistance could be used to predict the inducibility of
beta-lactamase. Of 326 organisms from species capable of beta-lactamase
induction, induction was shown in 68% and was predictable from the
cefoxitin-sensitivity and identification data. No induction of
beta-lactamase occurred in the remaining species. A comparison of
beta-lactamase activities against cefotaxime, cefoperazone and latamoxef
showed that induction of enzyme activity against cefotaxime and
cefoperazone occurred at similar rates. Induction of activity against
latamoxef did not occur or was minimal with three bacterial species. The
data show that of 119 strains of Enterobacteriaceae displaying inducible
beta-lactamase, 113 would have been reported as unequivocally sensitive to
cefotaxime, 109 as sensitive to cefoperazone and 116 as sensitive to
latamoxef if the disk-diffusion technique alone had been used. The majority
of Pseudomonas strains examined produced inducible enzyme and they were
more resistant to the three cephalosporins tested than were the
Enterobacteriaceae.
