[An experimental study on the release of endotoxin from gram negative bacteria induced by antibiotics]

To explore the characteristics and possible mechanism of LPS released from Gram negative bacteria induced by antibiotics, so as to improve clinical management of endotoxemia and sepsis.

Cultures containing PA103 subtype of Pseudomonas aeruginosa (PA) and E coli 25922 subtype of E coli were treated with four kinds of antibiotics as Imipenam (IMP), ceftazidime (CTZ), amikacin (AMN) and pefloxacine (PFX) in four concentrations of 0.5, 1, 5 and 10 MIC for 8 hours. The changes in the bacterial quantity and morphology and the supernatant levels of free LPS of the culture media were observed at different time points.

All the four kinds of antibiotics could kill the tested bacteria in similar degree, but lead to the different types of morphological changes of the bacteria. In detail, IMP could convert the bacteria into spherical shape, while CTZ and PFX made the bacteria to filamentous shape. But AMN could induce lysis of bacterial thallus. Under same condition, the ability of different kinds and concentrations of antibiotics to induce LPS release ranked as CTZ > PFX > IMP > AMN, 0.5MIC > 1MIC > 5MIC > 10MIC. Along with the prolongation of the action time, the LPS release increased. Furthermore, PA103 released less endotoxin than E. coli after the action of antibiotics.

All of the four antibiotics, i,e, IMP, CTZ, AMN and PFX could induce PA103 and E coli 25922 to release different levels of LPS, which was related to bacterial morphological changes. The LPS release from the bacteria was correlated to the antibiotics applied, concentrations, action time and the bacterial features. Antibiotics with less ability of inducing LPS release were recommended for clinical management of the sepsis and/or septic shock caused by Gram negative bacteria.