Factors associated with Pseudomonas pickettii intrinsic contamination of commercial respiratory therapy solutions marketed as sterile

Abstract

Laboratory investigations were conducted to study the growth dynamics of Pseudomonas pickettii in commercial 0.9% sodium chloride solution under various environmental conditions and to determine the retention of these organisms after challenge through a 0.2-μm cartridge filter system. Low numbers of P. pickettii (1 to 10 CFU/ml of test solution) inoculated into commercial vials containing 5 ml of 0.9% sodium chloride solution and 500-ml volumes of 0.9% sodium chloride solution were shown to proliferate over a 168-h incubation period. These organisms demonstrated growth over a wide range of temperatures (15 to 42°C) in this salt solution, and survival studies at 50, 55, and 60°C indicated that this strain was not unusually resistant to heat (with the times required at a given temperature to reduce the surviving microbial population 10-fold [D-values] being 26.0, 1.9, and 0.7 min, respectively). A challenge test demonstrated that P. pickettii organisms were not completely retained by a 0.2-μm cartridge filter. The number of organisms detected increased from 1 CFU/liter of effluent at 1 to 2 min to a maximum of 176 CFU/liter at 4 to 5 min. Our results indicate that P. pickettii can penetrate a 0.2-μm filtration system and that the passage of organisms and subsequent microbial growth in the filter effluent probably are the mechanisms by which these organisms were recovered from 'sterile' commercial 0.9% sodium chloride solution.