Cloning of a beta-lactam resistance determinant ofEnterobacter cloacaeaffecting outer membrane proteins of Enterobacteriaceae

In this paper we describe the cloning of a restriction fragment of Enterobacter cloacae chromosomal DNA that causes β-lactam resistance in both Escherichia coli HB101 and the parental strain E. cloacae 2249-1. The increase in minimum inhibitory concentration (MIC) of the β-lactam antibiotics studied was not the result of enhanced β-lactamase production, but of a decrease in the concentration of the pore proteins OmpF and OmpC in E. coli and of a 37-kDa membrane protein in E. cloacae. The results obtained thus far indicate that we have cloned a gene encoding a 20 kDa polypeptide that is involved in the regulation of outer membrane protein synthesis.