High temperature induced antibiotic sensitivity changes in Pseudomonas aeruginosa

Pseudomonas aeruginosa, which was resistant to a wide variety of antibiotic s, became sensitive to several of these antibiotics when grown and tested a t 46 degrees C. Cell wall antibiotics such as pencillin G and ampicillin we re only effective when added to cells growing at 46 degrees C prior to a te mperature shift to 37 degrees C. Antibiotics which penetrate the cytoplasmi c membrane to express their inhibiting action present a pattern different f rom those which are active against the outer cell wall. In order that these compounds be effective, the permeability of the cytoplasmic membrane must be further altered with agents such as EDTA which allow the penetration of actinomycin D. Inhibitors of protein synthesis, such as streptomycin and ch loramphenicol, have increased access to their sites of action in cells grow n at 46 degrees 0. Cells grown at 46 degrees C have 40% less lipopolysaccha ride (LPS) than cells grown at 37 degrees C and the LPS aggregates were of large molecular size in cells grown at 46 degrees C. Growth at 46 degrees C affects the permeability properties of the outer cell wall more than the p ermeability properties of the cytoplasmic membrane and this was due, in par t, to the selective release of LPS or LPS-protein complexes at elevated gro wth temperatures.