Antimicrobial Resistance Mediated By Synthesis of Richmond and Sykes Type I Beta-Lactamase
A number of beta-lactam antibiotics that are relatively resistant to hydrolysis by beta-lactamases have been developed. These new compounds have expanded antibacterial activity but also have posed several challenging clinical problems including therapeutic failures and relapses of infections. Strains most often involved are Enterobacter, Serratia, and Pseudomonas-genera that characteristically possess inducible chromosomal beta-lactamases (Richmond-Sykes type I). Due to the prevalence of these organisms, this study was initiated to evaluate current methodology for detection of this resistance and delineate situations wherein these problems are expected to arise. Prevalence of inducible beta-lactamases occurring in a hospital setting was determined along with frequency of mutation to a stably derepressed state. Interactions between these bacterial strains and beta-lactam drugs were examined through growth curves. A rapid susceptibility test was evaluated for detection of this resistance. These results emphasize the need to carefully evaluate clinical isolates capable of producing these enzymes before reporting results of rapid susceptibility procedures.
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