Influence of temperature on beta-lactamase production and outer membrane proteins in gram-negative rods

The influence of temperature (ranging from 28 to 42 degrees C) was studied on the phenotypic expression of chromosomally mediated beta-lactamases in gram-negative clinical isolates and in their beta-lactamase-depressed resistant counterparts. The enzymes were expressed most intensely at lower temperatures (28 or 32 degrees C). In most strains the enzyme was barely detectable at growth temperatures of 42 degrees C independent of the inducer employed. The release of the enzyme into the surrounding medium was marginal even at a growth temperature of 42 degrees C. The major outer membrane proteins revealed discrepancies dependent on the growth temperature only for the Providencia rettgeri W 862 strain. Thus, it can be concluded that the phenotypic expression of chromosomal beta-lactamase is temperature dependent to the effect that the enzymes are most expressed at 28 or 32 degrees C. This agrees well with the increased susceptibility to most beta-lactams due to the lowered beta-lactamase production at higher temperatures. This effect was pronounced most strikingly in Proteus vulgaris.