Article Figures & Data
Figures
- FIG. 1.
Differentiation of E. sakazakii using the newly developed OK medium. The distinct fluorescent colonies are identified as E. sakazakii, and black spotted colonies are H2S-producing microorganisms.
Tables
- TABLE 1.
Bacterial strains used to evaluate selective and differential media
Strain Sourcea Enterobacter sakazakii ATCC 51329 ATCC Enterobacter sakazakii ATCC 29544 ATCC Enterobacter sakazakii ATCC 29004 ATCC Enterobacter sakazakii ATCC 12868 ATCC Escherichia coli O157:H7 ATCC 35150 ATCC Escherichia coli O157:H7 ATCC 43889 ATCC Escherichia coli O157:H7 ATCC 43890 ATCC Escherichia coli ATCC 25922 ATCC Escherichia coli B E4a WSU Escherichia coli K-12 2B WSU Klebsiella pneumoniae K1a WSU Klebsiella pneumoniae Revco 41 WSU Klebsiella pneumoniae Revco 55 WSU Pseudomonas aeruginosa ATCC 15442 ATCC Salmonella enterica 6170 WSU Salmonella enterica serovar Typhimurium ATCC 19585 ATCC Salmonella enterica 4509 WSU Enterobacter aerogenes ATCC 13048 ATCC Enterobacter cloacae Rev 1210 Case 00-5395 WSU Enterobacter cloacae Rev 1343 Case 00-12286 WSU ↵ a ATCC, American Type Culture Collection (Manassas, Va.); WSU, Food Science and Human Nutrition bacteria collection at Washington State University (Pullman, Wash.).
- TABLE 2.
Selectivity of 4-methylumbelliferyl-α-d-glucoside solid media and their background noise production after incubation at 30°C for 24 h
Media Recovery of microbial flora (%)a Background noise (%)b with 16-strain cocktail E. sakazakii cocktail 16-strain cocktail VRBG agar 69.7 72.2 52.4b Tryptone bile agar 92.2 91.3 1.0a TSA 100.0 100.0 43.5b ↵ a Colonies recovered on VRBG and tryptone bile agar expressed as percentage of CFU ml−1 recovered on TSA.
↵ b Occurrence of nontarget fluorescent colonies expressed as percentage of total CFU ml−1 recovered on TSA. Values followed by different superscript letters are statistically different (P ≤ 0.05).
- TABLE 3.
Selection of nitrogen source and optimization of tryptone concentration at incubation of 30°C for 24 h tested with background culture mixed cocktail
Nitrogen source Background noise (%)a Tryptone concentration (g/liter) Background noise (%) Bacto Peptone 56.35 ± 2.48c 40 0.37 ± 0.65a Tryptone 0.68 ± 0.59a 20 0.62 ± 0.54a Proteose Peptone I 11.60 ± 3.38b 10 10.03 ± 4.01b Proteose Peptone II 1.38 ± 0.74a 5 48.85 ± 4.28c Proteose Peptone III 72.66 ± 10.19d 2.5 77.33 ± 12.20d ↵ a Occurrence of nontarget fluorescent colones expressed as percentage of total CFU ml−1 recovered on TSA; means ± standard deviations of three replicated plates. Values followed by different superscript letters are statistically different (P ≤ 0.05).
- TABLE 4.
Effect of incubation time and temperature on the recovery of fluorescent E. sakazakii colonies and total microorganisms tested with total culture mixed cocktail
Time (h) Fluorescent coloniesa Total colonies Fluorescent colonies/ total colonies (%)b 30°C 37°C 30°C 37°C 30°C 37°C 18 0.67 ± 0.58 5.33 ± 1.53 77.33 ± 6.66 87.67 ± 4.51 0.87a 6.08b 24 2.33 ± 1.15 7.33 ± 3.06 78.67 ± 6.43 88.67 ± 3.51 2.96a 8.27b 48 5.33 ± 1.53 7.33 ± 3.06 84.33 ± 7.51 89.33 ± 3.06 6.32b 8.21b
