EXPRESSION OF GENES ASSOCIATED WITH ANTIBIOTIC EXTRUSION IN PSEUDOMONAS-AERUGINOSA

We cloned the gene(s) associated with multiantibiotic resistance in Ps eudomonas aeruginosa from a mutant with elevated drug extrusion. The s train harboring cloned gene accumulated less amount of ofloxacin than the strain without the clone. By using Southern and northern blot anal yses, we investigated whether multiantibiotic resistance is caused by gene amplification or overexpression. We found that all our multiantib iotic resistant mutants isolated earlier overexpressed mRNA homologous to the cloned gene(s). Overexpresssions of the 41 KDa and 110 KDa inn er and the 50 KDa outer membrane proteins were detected. Other multian tibiotic resistant mutants including the nalB mutant overexpressed the mRNA and the membrane proteins, but the nfxB and nfxC mutants did lit tle. We concluded that low antibiotic accumulation in the multiantibio tic resistant mutants is attributable to overexpression of the antibio tic extrusion machinery. (C) 1995 Academic Press, Inc.