| With this technique , we demonstrated that the structural gene for ETA , toxA , as well as two genes encoding positive regulators of ETA synthesis , regA and regB , were expressed in the lungs of CF patients infected with P . aeruginosa . ^^^ The presence of high levels of toxA , regA , and regB RNAs in some sputum samples prompted us to look for hyperproducing toxin strains in the sputa of CF patients . ^^^ These observations suggest that regA and regB are involved in the regulation of ETA production in strains of P . aeruginosa infecting the lungs of CF patients and that some of these strains may regulate ETA production in a manner similar to that of the hyperproducing ETA strain PA103 . . ^^^ |