Abstract:

Objective To explore the application value of bacterial ultrasonic dispersion counter in pretreatment of microbiology experiment. Methods The bacterial suspensions of nine different types of bacteria species were prepared by using the traditional manual dispersion method and the new instrument ultrasonic dispersion method, and then the dispersion effects of those bacterial suspensions which prepared by two methods were compared through the macroscopic observation, gram’s stain microscopy and turbidity measure of bacterial suspension. The impacts of these two methods on the activity of bacteria were also compared in this study. Results Seven types of bacteria could be dispersed sufficiently in low level power, while the other two types of bacteria were dispersed in medium level power. Different types of bacteria had different ultrasonic processing time, with the longest 120 s and the shortest 10 s. The degree of uniformity of the bacterial suspensions prepared by the instrument ultrasonic dispersion method was better and there was no obvious bacterial aggregation. The dispersion effects of the bacterial suspensions of Acinetobacter baumannii, Klebsiella pneumoniae and Stenotrophomonas maltophilia, etc. prepared by the two methods had no statistically significant difference. The ideal dispersion effect of the bacterial suspensions could be obtained at 30 s of ultrasonic dispersing; the extension of ultrasonic dispersing time, the turbidity of most of bacterial suspensions didn’t change significantly. However, as for Acinetobacter baumannii, Enterobacter cloacae and Escherichia coli, the turbidity of bacterial suspensions significantly decreased with the extension of ultrasonic dispersing time, while for Klebsiella Pneumoniae, the turbidity of bacterial suspension got top at 60s and then gradually declined with the extension of ultrasonic dispersing time. Under the 1∶10 ⁵ dilution degree, the mean number of plate bac-terial colonies of Escherichia coli dispersed by the instrument ((59±6)×10 ⁵ CFU/ml)) was significantly lower than that of the manual dispersions ((76±8)×10 ⁵ CFU/ml)), F=10.321, P=0.033; the mean number of plate bacterial colonies of Noka bacteria dispersed by the instrument ((9±6)×10 ⁵ CFU/ml)) was significantly higher than that of the manual dispersions ((2±0)×10 ⁵ CFU/ml)), F=8.693, P=0.015; there was no significant difference on growth activity in bacterial suspensions of other 7 types of bacteria species prepared by using the instrument ultrasonic dispersion method and the traditional manual method. Conclusion Compared with traditional manual dispersion method, the dispersion effect of bacterial ultrasonic dispersion counter for the tested bacteria species is more ideal, and instrument ultrasonic dispersion need shorter time and have no influence to bacteria growth activity at the same time. The bacterial ultrasonic dispersion counter is able to provide a set of safe, efficient, and standardized solution for bacterial suspension preparation, which has high application value in pretreatment of microbiology experiment.

Key words: Sonication, Microbiological techniques, Specimen handling, Comparative study