Rapid Quantitative Detection of Live Escherichia coli Based on Chronoamperometry.

The rapid quantitative detection of Escherichia coli (E. coli) is of great significance for evaluating water and food safety. At present, the conventional bacteria detection methods cannot meet the requirements of rapid detection in water environments. Herein, we report a method based on chronoamperometry to rapidly and quantitatively detect live E. coli. In this study, the current indicator i0 and the electricity indicator A were used to record the cumulative effect of bacteria on an unmodified glassy carbon electrode (GCE) surface during chronoamperometric detection. Through the analysis of influencing factors and morphological characterization, it was proved that the changes of the two set electrochemical indicator signals had a good correlation with the concentration of E. coli; detection time was less than 5 min, the detection range of E. coli was 104−108 CFU/mL, and the error range was <30%. The results of parallel experiments and spiking experiments showed that this method had good repeatability, stability, and sensitivity. Humic acid and dead cells did not affect the detection results. This study not only developed a rapid quantitative detection method for E. coli in the laboratory, but also realized a bacterial detection scheme based on the theory of bacterial dissolution and adsorption for the first time, providing a new direction and theoretical basis for the development of electrochemical biosensors in the future.

Monitoring and evaluation of antibiotic resistance genes in three rivers in northeast China.

Antibiotic resistance genes (ARGs) have become an important public health problem. In this study, we used metagenomic sequencing to analyze the composition of ARGs in selected original habitats of northeast China, comprising three different rivers and riverbank soils of the Heilongjiang River, Tumen River, and Yalu River. Twenty types of ARG were detected in the water samples. The major ARGs were multidrug resistance genes, at approximately 0.5 copies/16S rRNA, accounting for 57.5% of the total ARG abundance. The abundance of multidrug, bacitracin, beta-lactam, macrolide-lincosamide-streptogramin, sulfonamide, fosmidomycin, and polymyxin resistance genes covered 96.9% of the total ARG abundance. No significant ecological boundary of ARG diversity was observed. The compositions of the resistance genes in the three rivers were very similar to each other, and 92.1% of ARG subtypes were shared by all water samples. Except for vancomycin resistance genes, almost all ARGs in riverbank soils were detected in the river water. About 31.05% ARGs were carried by Pseudomonas. Opportunistic pathogenic bacteria carrying resistance genes were mainly related to diarrhea and respiratory infections. Multidrug and beta-lactam resistance genes correlated positively with mobile genetic elements (MGEs), indicating a potential risk of diffusion. The composition of ARGs in three different rivers was similar, indicating that climate plays an important role in ARG occurrence. ARG subtypes in river water were almost completely the same as those in riverbank soil. ARGs had no significant geographical distribution characteristics. Many ARGs were carried by human pathogenic bacteria related to diarrhea and respiratory infections, such as Pseudomonas aeruginosa and Aeromonas caviae. In general, our results provide a valuable dataset of river water ARG distribution in northeast China. The related ecological and geographical distribution characteristics should be further explored.

Characterization of a novel Vibrio parahaemolyticus host-phage pair and antibacterial effect against the host.

Vibrio parahaemolyticus is a widely recognized pathogen that has caused numerous outbreaks and is prevalent in the marine environment. In this study, we investigated the characteristics of the novel V. parahaemolyticus strain BTXS2 and its associated phage, VB_VpP_BT-1011, isolated from the Bohai Coast (Tianjin, China). Strain BTXS2 is a short coryneform bacterium with a terminal flagellum and is able to utilize and metabolize a wide variety of organic matter because of its unique carbon source utilization and enzyme activity. It grows well in medium between pH 5.0 and 9.0 and salinities of simulated freshwater, estuary water, and seawater (NaCl 0.5%-3%). Multiple antibiotic resistance genes and virulence genes that endanger human health were found in the BTXS2 genome. Phage VB_VpP_BT-1011, which infects BTXS2, is a 40,065-bp double-stranded DNA virus of the family Myoviridae with a latent time of 30 min and burst size of 24 PFU/cell. Like its host, the phage tolerates a broad range of environmental conditions (salinity, 0-3% NaCl; pH 5.0-9.0; temperature, 4-37°C). A host range test showed that the phage only infected and inhibited isolate BTXS2. In summary, we investigated a novel V. parahaemolyticus host-phage pair and the antibacterial effect of the phage on V. parahaemolyticus, providing insights into marine microbial ecology and risks.