Lll. Yeh et Cl. Chi, Another look at differences in the susceptibility of Escherichia coli and Klebsiella pneumoniae to cephalothin and cefazolin, INT J ANT A, 17(6), 2001, pp. 521-524
The significance of in vitro susceptibility tests on Enterobacteriaceae to
cephalothin and cefazolin has not been exactly defined in the guidelines of
the National Committer for Clinical Laboratory Standards. In the hope of c
larifying this confusion. we provide additional information from an ancilla
ry study of the Taiwan Surveillance of Antimicrobial Resistance 1998 (TSAR
I). There were 505 Escherichia coli and 227 Klebsiella pneumoniae isolates
susceptible to cephalothin. reported by 42 participating hospitals. The sus
ceptibility of these isolates were re-tested at the Microbial Infections Re
ference Laboratory using cefazolin, with the result that 72% of the 252 cep
halothin-resistant E. coli isolates and 24% of the 41 cephalothin-resistant
K. pneumoniae isolates were found to be susceptible to cefazolin. We furth
er surveyed the availability of cephalothin and cefazolin in Pharmacy Depar
tments: all of the TSAR I hospitals had cefazolin available in their pharma
cies. The resistance rate of E. coli was significantly lower for 12 hospita
ls that had cefazolin in both pharmacy and laboratory compared with 11 hosp
itals that had cefazolin available in pharmacy but cephalothin in laborator
y. In addition, for all the hospitals that had cephalothin available for cl
inical use, the resistance rate was twice as low in two hospitals reporting
cefazolin susceptibility as in the seven hospitals reporting cephalothin s
usceptibility. Our findings suggest that inappropriate selection of cephalo
thin and cefazolin for susceptibility testing contribute to inaccurate indi
cations of in vivo activity for first generation cephalosporins in the trea
tment of E. roil infections. (C) 2001 Elsevier Science B.V. and Internation
al Society of Chemotherapy. All rights reserved.