Altered expression of oligopeptide-binding protein (OppA) and aminoglycoside resistance in laboratory and clinical Escherichia coli strains

Oligopeptide-binding protein (OppA) is the periplasmic component of the maj or oligopeptide transport system of enteric bacteria. Genetic and biochemic al evidence suggests that OppA plays a role in the uptake of aminoglycoside antibiotics in Escherichia coil K-12, Forty-sis (82%) of 56 aminoglycoside -resistant mutants of E, coli K-12 selected in vitro had reduced or undetec table OppA levels? as compared with their parent strain. Moreover, nine (36 %) of 25 aminoglycoside-resistant clinical isolates of E, coil expressed re duced or undetectable levels of OppA. No decrease in OppA expression was ob served among aminoglycoside-sensitive E, coil strains from patients. Twenty -three (42%) of 56 aminoglycoside-resistant mutants of E, coil K-12 and sis (24%) of 25 clinical isolates also were deficient for expression of ornith ine or arginine decarboxylases, or both, and these deficiencies might negat ively affect OppA expression by reducing polyamine synthesis. These results support the view that reduced OppA expression is associated with aminoglyc oside resistance in E, coil strains.