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Antimicrobial Preservative Efficacy and Microbial Content Testing*
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Scott V.W. Sutton, Philip A. Geis
The ASTM methods (90) actually comprise a series of experiments to show whether a neutralizer is nontoxic and effective. Testing is first done to determine the maximum tolerated concentration (MTC) of the inactivator using the correct liquid test medium. Often, the medium will be buffered peptone water. After adding the target organism, one determines the microbial counts at 0 and 30 minutes. The peptone water should not cause a significant decrease in microbial survival over the 30 minutes.
Antimicrobial preservative efficacy and microbial content testing
Published in Philip A. Geis, Cosmetic Microbiology, 2006
The ASTM methods84 actually comprise a series of experiments to show whether a neutralizer is nontoxic and effective. Testing is first done to determine the maximum tolerated concentration (MTC) of the inactivator using the correct liquid test medium. Often, the medium will be buffered peptone water. After adding the target organism, one determines the microbial counts at 0 and 30 min. The peptone water should not cause a significant decrease in microbial survival over the 30 min.
Continuous flow system for biofilm formation using controlled concentrations of Pseudomonas putida from chicken carcass and coupled to electrochemical impedance detection
Published in Biofouling, 2020
Daoyuan Yang, José I. Reyes-De-Corcuera
The concentration changes of the original and the diluted bacterial suspensions (log CFU ml−1) for 100-fold, 1,000-fold and 10,000-fold dilution were monitored for up to 63 h to ensure that the flow system produced consistent bacterial concentrations. As shown in Figure 3, throughout the entire experiments, the original bacterial suspension stayed at 8.6 ± 0.2, 8.5 ± 0.1 or 8.7 ± 0.4 log CFU ml−1, and the diluted bacterial suspension stayed at 6.8 ± 0.3, 5.5 ± 0.2 or 5.1 ± 0.6 log CFU ml−1 corresponding to the 100-fold, 1,000-fold or 10,000-fold dilution, respectively. The variability of the diluted cell suspensions concentration was small throughout the individual experiment up to 63 h and among the experimental replicates, demonstrating the usefulness of the proposed flow system and its potential to mimic conditions found in food systems. However, for water distribution systems as an example, further dilution is necessary. The inner surface of the SS tubes, different from most commonly used grids or coupons, were used as the biofilm attaching surface, since SS is the major material used in the food industry. Peptone water was chosen to dilute the bacterial suspension because it can maintain bacterial counts constant by providing a nutrient source for a short time and minimizing cell death.
A novel probiotic, Lactobacillus johnsonii 456, resists acid and can persist in the human gut beyond the initial ingestion period
Published in Gut Microbes, 2019
Michael J. Davoren, Jared Liu, Jocelyn Castellanos, Norma I. Rodríguez-Malavé, Robert H. Schiestl
SGA was prepared by dissolving 3.3ppm pepsin (Sigma) and 0.2% NaCl w/v in 0.1% peptone water (Becton Dickinson; Franklin Lakes, NJ). The pH of this solution was then brought to 1.2 with the addition of 11.65M hydrochloric acid to recapitulate concentrated gastric fluid in an otherwise empty human stomach. This solution was diluted using additional 0.1% peptone water to pHs of 1.6, 2.0, and 3.0. The probiotic strains (L. johnsonii 456, L. johnsonii VPI 7960, L. casei, L. acidophilus, L. plantarum, B. lactis, and S. salivarius) were grown to a concentration of roughly 1 × 108 CFU/mL by the methods described above. 106 mid-log phase cells were inoculated into 10mL SGA or 0.1% peptone water control (pH 6) and incubated for 2 hours at 37° C to simulate gastric transit. After incubation, samples were diluted in 0.1% peptone water and plated on agar for enumeration.
Microbial contamination of multiple‐use bottles of fluorescein ophthalmic solution
Published in Clinical and Experimental Optometry, 2019
Samuel Kyei, David France, Kofi Asiedu
One millilitre of the sample was added to 9 ml of peptone water and incubated for six hours. Peptone water serves as a maximum recovery diluent. The samples were serially diluted to prevent bacterial overgrowth during culturing, then plated using the following pour plate method. First, 1,000 μl of the serially diluted samples were inoculated into clean autoclaved Petri dishes. Some 20 ml of the culture media (blood agar, Sabouraud dextrose agar, MacConkey or plate count agar) were poured into the plates, swelled gently and allowed to solidify. The solidified plate samples were incubated in Panasonic cooled incubator MIR‐154 at 37°C for 24 hours for bacteria and 25°C for fungi, respectively. Individual visible viable colonies seen after 24 hours were counted and recorded. This was to enable the calculation of the colony forming units (CFUs), of viable bacteria which were expressed as CFU/ml.