Cross-resistance patterns among clinical isolates of Klebsiella pneumoniaewith decreased susceptibility to cefuroxime

The frequency of decreased susceptibility to cefuroxime and quinolones and the correlation between these drug resistance traits was investigated in cl inical isolates of Klebsiella pneumoniae from two Danish counties. Eighty-t hree randomly selected clinical isolates of K. pneumoniae with decreased su sceptibility to cefuroxime were examined for cross-resistance patterns and the production of beta-lactamases. The frequency of resistance to cefuroxim e and ciprofloxacin has increased from <5% in 1990 to 15% and 7% in 1998, r espectively. Two of the 83 isolates were multiply resistant and seemed to p roduce extended-spectrum beta-lactamases. However, cross-resistance to cipr ofloxacin and other classes of drug in 68% of the remaining isolates indica tes that other resistance mechanisms, such as penetration barriers, had pro bably been selected in these Danish isolates. The susceptibility to ciprofl oxacin decreased successively with decreasing susceptibility to cefuroxime for K. pneumoniae, This did not occur in cefuroxime-resistant Escherichia c oli.