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Antimicrob Agents Chemother. 1977 April; 11(4): 599-604
Copyright © 1977 American Society for Microbiology. All Rights Reserved.

Comparative Activity of Ampicillin and Cefuroxime Against Three Types of Haemophilus influenzae

R. B. Sykes, A. Griffiths and D. M. Ryan

Glaxo Research Ltd., Greenford, Middlesex, UB6 OHE, England

ABSTRACT

On the basis of their susceptibility to ampicillin, strains of Haemophilus influenzae can be divided into three types: type 1 are normally susceptible strains, type 2 produce stable spheroplasts from low inocula, and type 3 are ß-lactamase producers. Because of the production of spheroplasts, standard broth and agar dilution techniques have failed to differentiate between the responses of type 2 and 3 strains to ampicillin, or to identify the superiority of cefuroxime over ampicillin against the ß-lactamase-producing strains. Disk susceptibility tests with heavily seeded plates were also difficult to interpret. To overcome these problems, we developed a medium that supports the growth of H. influenzae, but not survival of spheroplasts, thereby reducing the complicating influence of spheroplast formation. Utilization of the medium made it possible to identify ß-lactamase-producing strains via both minimal inhibitory concentration and disk susceptibility techniques, as well as the superiority of cefuroxime over ampicillin against such strains. In vivo experiments showed that cefuroxime and ampicillin are equally active against infections with type 1 and 2 strains, but that cefuroxime is superior to ampicillin against infections with type 3 ß-lactamase-producing strains.


Antimicrob Agents Chemother. 1977 April; 11(4): 599-604
Copyright © 1977 American Society for Microbiology. All Rights Reserved.




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Copyright © 1977 by the American Society for Microbiology. All rights reserved.