Tl. Raivio et al., ASSOCIATION BETWEEN TRANSCRIPT LEVELS OF THE PSEUDOMONAS-AERUGINOSA REGA, REGB, AND TOXA GENES IN SPUTA OF CYSTIC-FIBROSIS PATIENTS, Infection and immunity, 62(8), 1994, pp. 3506-3514
In this study, we examined the regulation of exotoxin A (ETA) producti
on by Pseudomonas aeruginosa during chronic lung infections of cystic
fibrosis (CF) patients. We used a recently developed technique termed
population transcript accumulation in hybridization studies with RNA e
xtracted from sputa. With this technique, we demonstrated that the str
uctural gene for ETA, toxA, as well as two genes encoding positive reg
ulators of ETA synthesis, regA and regB, were expressed in the lungs o
f CF patients infected with P. aeruginosa. These genes were always exp
ressed together, never alone or in pairs, suggesting coincident expres
sion and a possible regulatory role for regA and regB in this environm
ent. Fluctuations in the levels of the three gene products were observ
ed among samples, consistent with a regulatory phenomenon. The level o
f regB RNA detected never exceeded that of regA, although the ratio of
regA RNA to regB RNA detected did change between samples. These obser
vations are in agreement with in vitro observations which have shown t
hat regB is located 3' to regA in an operon which is expressed from tw
o independently regulated promoters located upstream of regA. The pres
ence of high levels of toxA, regA, and regB RNAs in some sputum sample
s prompted us to look for hyperproducing-toxin strains in the sputa of
CF patients. In vitro, one such strain, 4384, had a transcript accumu
lation pattern for toxA, regA, and regB similar to that of a laborator
y hyperproducer of ETA, strain PA103. These observations suggest that
regA and regB are involved in the regulation of ETA production in stra
ins of P. aeruginosa infecting the lungs of CF patients and that some
of these strains may regulate ETA production in a manner similar to th
at of the hyperproducing-ETA strain PA103.