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Acinetobacter — Microbiology
Published in E. Bergogne-Bénézin, M.L. Joly-Guillou, K.J. Towner, Acinetobacter, 2020
Identification of bacteria to the genus Acinetobacter is based on the following criteria (Cowan, 1993): Gram-negative coccobacilli, oxidasenegative (with Kovac’s reagent), non-fermenting in O-F test, non-motile in hanging drop preparation, aerobic growth, catalase-positive, nitrate reduction mostly negative, and hydrolysis of Tween® mostly positive.
Published in Ronald M. Atlas, James W. Snyder, Handbook Of Media for Clinical Microbiology, 2006
Ronald M. Atlas, James W. Snyder
Use: For the simultaneous detection of total coliforms and E. coli by the fluorogenic procedure. A color change of the broth from yellow to blue-green indicates the presence of coliforms. A blue fluorescence under long-wave UV light permits the rapid detection of E.coli. As tryptophan is added to the broth, the indole reaction is easily done by adding KOVACS reagent. The formation of a red ring additionally confirms the presence of E.coli.
Sub-minimum inhibitory concentration ceftazidime inhibits Escherichia coli biofilm formation by influencing the levels of the ibpA gene and extracellular indole
Published in Journal of Chemotherapy, 2020
Fengjun Sun, Qian Yuan, Yu Wang, Lin Cheng, Xiaoyu Li, Wei Feng, Peiyuan Xia
Detection of the concentration of extracellular indole of E. coli was performed as previously described.16 Bacterial cultures were added into both LB broth and LB broth with 1/4 MIC CAZ and incubated at 37 °C with shaking at 180 rpm for 24 h. The bacterial cultures were centrifuged at 12,000 × g for 2 min. Then, 5 ml of cell-free supernatant was taken out and added into 2 ml of Kovac’s reagent containing 10 g of p-dimethylaminobenzaldehyde (Sigma, USA), 150 ml of amyl alcohol and 50 ml of HCl. The mixture was reacted for 2 min, and then 100 µl of the reaction solution was added into 900 µl of HCl/amyl alcohol solution (HCl:amyl alcohol = 1:3). The absorbance was determined at 540 nm, and the concentrations of extracellular indole were calculated according to a calibration curve.
Indole intercepts the communication between enteropathogenic E. coli and Vibrio cholerae
Published in Gut Microbes, 2022
Orna Gorelik, Alona Rogad, Lara Holoidovsky, Michael M. Meijler, Neta Sal-Man
Indole concentration in the bacterial samples was determined by mixing bacterial supernatants with 20% trichloroacetic acid in a 1:1 (v/v) ratio and incubating them on ice for 15 min. The samples were then centrifuged (at 13,000 × g for 10 min) to remove precipitated proteins, collected, and mixed 1:1 (v/v) with Kovac’s reagent (Sigma-Aldrich). The samples were vortexed and left standing for 1 min to allow phase separation. The top layers of the samples were collected, and their optical density at 571 nm was measured. A standard curve of known indole concentration was used to estimate the amount of indole in each sample.
Microbial contamination of multiple‐use bottles of fluorescein ophthalmic solution
Published in Clinical and Experimental Optometry, 2019
Samuel Kyei, David France, Kofi Asiedu
The isolated bacteria were examined for biochemical activity using various tests. The triple sugar iron and citrate agars were prepared in a test tube as directed by the manufacturer. Bacteria were inoculated in the media and the result observed and recorded. Other biochemical tests performed were indole formation using Kovac reagent, oxidase test using hydrogen peroxide and catalase using fresh serum. Results from these tests were recorded, aiding in the identification of the bacteria.