IMIDAZOLIDINYL UREA RESISTANT PSEUDOMONAS 417 o 2 1 i i i 'T • •' • 0 2 4 6 24 96 168 336 $04 67:2 Hours Figure 1. Growth of P. aeruginosa ATCC 9027 in dilute nutrient broth with imidazolidinyl urea at concentrations of: 6% ([]), 4% (--), 2% (0), 1% (/•), 0.5% (x), and 0% (V). 9 8 7 6 5 3 2 1 0 2 4 6 24 96 168 356 504 672 Hours Figure 2. Growth of P. aeruginosa P5 in dilute nutrient broth with imidazolidinyl urea at concentrations of: 6% ([]), 4% (--), 2% (0), 1% (/•), 0.5% (x), and 0% (V).

418 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS I I I [ ! 1 I I 0 2 4 6 24. 96 1 68 .•6 •0• 672 Hour• Figure 3. Growth of P. putida 495 in dilute nutrient broth with imidazolidinyl urea at concentrations of 6% ([•), 4% (--), 2% (O), 1% (/•), 0.5% (x), and 0% cfu/ml within 4 hours (Figure 4). The population did not enter exponential log phase growth until 24 hours after inoculation. This was a much longer lag period than the 6 hours required for the cells to adapt to imidazolidinyl urea. The cell population grown in 0.05% quaternium 15 also demonstrated a 24-hour lag period. GROWTH PATTERNS IN AN EMULSION Various concentrations of the peanut oil emulsion were employed as a growth medium to determine if cosmetic components enhanced or changed the growth pattern of the organisms. The ATCC 9027 isolate was killed by all 3 concentrations of imidazolidinyl urea (0.5, 1.0, and 2.0%) in the diluted (10% and 30%) and 100% emulsion. The growth pattern of the product isolates inoculated into 100% emulsion was slightly different from the pattern demonstrated in the diluted products. For example, the lag time for P5 in 100% product was 20 hours less than that required by P5 grown in 0, 10, or 30% product solutions (Figure 5). The cell population in 100% product pre- served with 2% imidazolidinyl urea produced a growth pattern most similar to the pattern in unpreserved dilute nutrient broth. In all experiments with product isolates, the addition of product only slightly enhanced the growth of the organisms in the presence of imidazolidinyl urea. It was possible to further adapt the product isolates to grow in the presence of imidazo- lidinyl urea. After pre-incubation in broth containing 1% imidazolidinyl urea or 10% product containing 1% imidazolidinyl urea, strain P5 immediately entered exponential log phase after inoculation into 100% product preserved with 2.0% imidazolidinyl urea