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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.

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.

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