Dataset of changes in viscosity of Escherichia albertii cultures during storage at room temperature

Published: 24 March 2023| Version 2 | DOI: 10.17632/hfwvd8z8xm.2
Miyuki Fujioka


Escherichia albertii was named in 2003 as a new species in the genus Escherichia and is known as a causative agent of diarrhea. Although the biochemical characteristics of E. albertii are not specific for differentiating it from other species, it is now possible to identify the species by PCR targeting specific genes. Among about 100 strains of E. albertii at our institution, only one strain was viscous, but we examined the change in viscosity because some of the strains acquired viscosity during storage. The target strain was the strain with viscosity change, and the controls were the viscous strain, E. albertii JCM strain, and E. coli ATCC strain. Biochemical properties, drug susceptibility, and string tests were performed under various conditions. No significant differences were observed in biochemical properties and drug susceptibility tests. In the string test of the viscous strain, the viscous colonies did not show any significant change in viscosity with passaging, especially the non-viscous colonies did not show any change in viscosity. Similarly, there was no change in the viscosity of either the viscous or the non-viscous colonies by passaging in the strain with altered viscosity. Neither the length of the storage period nor the casitone concentration affected the viscosity change. The change in viscosity was related to the storage of the strain at room temperature, suggesting that the process from the clinical specimen to the storage after isolation may have affected the change in viscosity.


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The strains were isolated and identified as E. albertii at Sapporo Clinical Laboratory and transferred to this institution on a Mueller–Hinton S (Eiken, Tochigi, Japan) test tube medium. These transferred strains were cultured in a LB (Sigma-Aldrich Japan, Tokyo, Japan) broth and a Heart infusion (HI) agar medium (Eiken, Tochigi, Japan) on the day of delivery, stored at room temperature in a Casitone medium (Eiken, Tochigi, Japan) and frozen at -80°C in the Microbank (Iwaki, Tokyo, Japan) according to the manufacturer's instructions. The transferred strains that had changed to a viscous consistency after four months of storage at room temperature on Casitone medium (strains with viscosity change) were included. ・Biochemical characterization and antimicrobial susceptibility testing Antimicrobial susceptibility was determined using the Kirby–Bauer disk diffusion method. The antibiotics were used ofloxacin, ciprofloxacin, erythromycin, fosfomycin, and tetracycline (Sensi disk, BD Fukushima, Japan). The diameters of the inhibition zones were interpreted according to the CLSI guidelines. ・Effect of subculture on string testing The viscosity-altered strains stored in Casitone medium and Microbanks were incubated in LB broth at 37°C for 24 h. Then the bacterial solution was diluted such that 100–200 colonies developed on standard agar plates (Nissui, Tokyo, Japan) and incubated at 37°C for 24 h. String test was performed on all colonies, and a string of 5 mm or higher was considered to be positive for viscosity. Then, one viscous and one non-viscous colony from the medium were each inoculated into LB broth and grown to a concentration of McFarland 0.5 at 37°C. The cultured medium was then diluted such that 100–200 colonies grew on standard agar plates and incubated similarly. The string test was then repeated on the colonies. ・Effect of storage time on viscosity change The effect of storage duration at room temperature was examined using Casitone medium. The strains were incubated in LB broth at 37°C for 24 h, and the culture solution was diluted so that 100–200 colonies would develop on a standard agar plate. Twenty non-viscous colonies grown on the medium were picked and stored on the Casitone medium. After 1-3 months, the string test was performed using the abovementioned process. ・Effect of casitone concentration on viscosity change during storage at room temperature We prepared media with casitone concentrations of 0.1, 0.5, 1, 2, and 10% to examine the effect of casitone on the change in viscosity. Ten non-viscous colonies were inoculated into each medium at different casitone concentrations and stored at room temperature after incubation at 37°C for 24 h. The string test was performed to analyze the viscosity.


Hirosaki Daigaku


Clinical Microbiology