No abstract

397Wall fragments were prepared from two strains of Pseudomonas cepacia and from P. aeruginosa, and their contents of readily extractable lipid, pronase-digestible protein and lipopolysaccharide were measured. Lipopolysaccharide extracted from P. cepacia, although biologically active, contained no detectable 2-keto-3-deoxyoctonic acid, but contained phosphate, rhamnose, glucose, heptose and hexosamine in concentrations comparable to those found in P. aeruginosa.

A strain of Pseudomonas cepacia that survived for 14 years (1963 to 1977) as a contaminant in an inorganic salt solution which contained commercial 0.05% benzalkonium chloride (CBC) as an antimicrobial preservative, was compared to a recent clinical isolate of P. cepacia. Ammonium acetate was present in the concentrated stock CBC solution, and served as a carbon and nitrogen source for growth when carried over into the salts solution with the CBC. The isolate's resistance to pure benzalkonium chloride was increased step-wise to a concentration of 16%. Plate counts showed 4 x 10(3) colony-forming units per ml in the salts solution. Comparison of growth rates, mouse virulence, antibiotics resistance spectra, and substrate requirements disclosed no differences between the contaminant and a recently isolated clinical strain of P. cepacia. The results indicate that it is critical that pharmaceutical solutions containing benzalkonium chloride as an antimicrobial preservative be formulated without extraneous carbon and nitrogen sources or be preserved with additional antimicrobial agents.

Sucrose-lysozyme spheroplasts were prepared from two strains ofPseudomonas cepacia and tested for susceptibility to polymyxin B and benzalkonium chloride. Spheroplasts were more susceptible than whole cells to benzalkonium chloride but not to polymyxin B. Disruption of the outer membrane layer was not by itself sufficient to render P. cepacia susceptible to polymyxin B. Pseuldomonas cepacia, originally described as a plant pathogen (2), has been implicated in nosocomial infections with increasing frequency (3,6 (EDTA) at a concentration of 15 mg, contained in 0.24 ml of a neutralized 6.25% (wt/vol) solution, and 300 ug of lysozyme (0.10 ml of a 0.3% solution) were added. Phase microscopy indicated the presence of 99.9 to 100% spheroplasts in all preparations. Control cells were washed with distilled water and resuspended in fresh medium prior to susceptibility testing. The susceptibility of cells and spheroplasts to PMB and BC was determined as follows. Samples (3 ml) of whole-cell or spheroplast suspensions were added to 7-ml portions of medium containing appropriate concentrations of the test compound. P. cepacia was tested in semidefined medium; E. coli was tested in nutrient broth. Assay tubes for Tris-EDTA-lysozyme spheroplasts were osmotically stabilized with 0.25 M sucrose. The number of viable whole cells and spheroplasts was determined by plate counts immediately after contact (0.5 min) with the antimicrobial agents and after 60 min of incubation at room temperature. Serial dilutions were made into tubes containing 0.01 M MgCl2, 0.22% lecithin, 1.55% polysorbate 80, and 0.25 M sucrose. Samples were plated on Trypticase soy agar with lecithin and polysorbate 80 (BBL) and incubated at 30°C (P. cepacia) or 37°C (E. coli) for 48 h. Controls were plated in the same manner immediately prior to the addition of the antimicrobial agents.

associated sulfur oxidation by the autotroph Thiobacillus thiooxidans. J. Bacteriol. 92:899-904. 1966.-Washed cell wall-membrane fragments derived from sulfur-grown cells of the strictly autotrophic bacterium, Thiobacillus thiooxidans, oxidized elemental sulfur to sulfate without the addition of cofactors. The oxidation was optimal at pH 7.0 and was increased by the presence of wetting agents. Oxygen uptake was inhibited by cyanide, azide, and thiol-binding agents. Sulfite was also oxidized, and both the sulfurand sulfite-oxidizing systems were heat-labile. Neither thiosulfate nor tetrathionate was oxidized by soluble or membrane preparations. The fragments fixed C402 in the presence of ribose-5-phosphate, Mg++, and adenosine triphosphate. Sulfur oxidation did not provide energy for C1402 fixation in this system.