Mechanism of antibiotic resistance spread during sub-lethal ozonation of antibiotic-resistant bacteria with different resistance targets.

The increase and spread of antibiotic-resistant bacteria (ARB) in aquatic environments and the dissemination of antibiotic resistance genes (ARGs) greatly impact environmental and human health. It is necessary to understand the mechanism of action of ARB and ARGs to formulate measures to solve this problem. This study aimed to determine the mechanism of antibiotic resistance spread during sub-lethal ozonation of ARB with different antibiotic resistance targets, including proteins, cell walls, and cell membranes. ARB conjugation and transformation frequencies increased after exposure to 0-1.0 mg/L ozone for 10 min. During sub-lethal ozonation, compared with control groups not stimulated by ozone, the conjugative transfer frequencies of E. coli DH5α (CTX), E. coli DH5α (MCR), and E. coli DH5α (GEN) increased by 1.35-2.02, 1.13-1.58, and 1.32-2.12 times, respectively; the transformation frequencies of E. coli DH5α (MCR) and E. coli DH5α (GEN) increased by 1.49-3.02 and 1.45-1.92 times, respectively. When target inhibitors were added, the conjugative transfer frequencies of antibiotics targeting cell wall and membrane synthesis decreased 0.59-0.75 and 0.43-0.76 times, respectively, while that for those targeting protein synthesis increased by 1-1.38 times. After inhibitor addition, the transformation frequencies of bacteria resistant to antibiotics targeting the cell membrane and proteins decreased by 0.76-0.89 and 0.69-0.78 times, respectively. Cell morphology, cell membrane permeability, reactive oxygen species, and antioxidant enzymes changed with different ozone concentrations. Expression of most genes related to regulating different antibiotic resistance targets was up-regulated when bacteria were exposed to sub-lethal ozonation, further confirming the target genes playing a crucial role in the inactivation of different target bacteria. These results will help guide the careful utilization of ozonation for bacterial inactivation, providing more detailed reference information for ozonation oxidation treatment of ARB and ARGs in aquatic environments.

[Preparation and pharmaceutical characterization of Marine-SSL].

OBJECTIVE: To prepare and characterize marine sterically stabilized liposomes (Marine-SSL). METHODS: Liposomes were prepared by ethanol injection technique. An orthogonal test was utilized to optimize the formulation and preparation of Marine-SSL The unencapsulated marine and liposomes were separated by sephadex gel G-50, the encapsulation efficiency was detected by HPLC. The morphological examination of Marine-SSL was performed using transmission electron microscopy. The particle size and Zeta potential of the liposomes were measured. The in vitro release rate of marine from liposomes was tested. RESULTS: The liposomes with spherical or ellipsoidal shape and better stability featured the encapsulation efficiency of (85.39 +/- 1.21)%, the mean partical size of (156 +/- 10) nm, and Zeta potential of (- 39.0 +/- 3.06) mv. The release kinetics in vitro obeyed Higuchi equation. The stability of Marine-SSL was better. CONCLUSION: The selected formulation and preparation technic of Marine-SSL are rational and stable and liposomes feature a sustained release in vitro.