Objective 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. Methods 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. Results 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. Conclusion 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.

OBJECTIVETo explore the effects of different beta-lactam antibiotics on the inducing of LPS release from gram-negative bacteria and on the protection of infected animals.

METHODSWistar rats were employed as the model and were inflicted by 30% TBSA III degree scalding and sepsis caused by PA103. The rats were randomly divided into 3 groups, i.e. simple antibiotic treatment group (A), treatment after sensitization with galactosamine (GalN) group (G) and treatment after blocking with carrageenan (CGN) group (C). The rats were injected intra-peritoneally with imipenem (IMP, 5 mg) and ceftazidime (CTZ, 10 mg) for single time, respectively. Same amount of aseptic normal saline was injected in the control group, and GalN (50 mg) was added in G and CGN (1 mg) in C groups. The blood bacterial concentration and plasma LPS levels were determined at different time points after the treatment by antibiotics. The mortality was observed in G and C groups at 10 days after treatment.

RESULTSThe blood bacterial amount could be decreased by both IMP and CTZ evidently. Large amounts of LPS released from PA103 could be induced by IMP and CTZ during their bactericidal process. But the plasma LPS level in rats treated by CTZ was markedly higher than that by IMP (P < 0.05 approximately 0.01). The mortality in G group treated by CTZ was much higher than that by IMP (P < 0.05). Nevertheless, the mortality in C groups was the same no matter CTZ or IMP was applied (P < 0.05).

CONCLUSIONThere was no difference of the bactericidal power between IMP and CTZ. But CTZ was more powerful in inducing LPS release from bacteria than IMP. It was implied by the difference between these two antibiotics that IMP might be better choice in clinical application for burn infection due to its lower potential of inducing LPS release from the bacteria.

Animals ; Anti-Bacterial Agents ; pharmacology ; Burns ; complications ; Ceftazidime ; pharmacology ; Cell Division ; drug effects ; Colony Count, Microbial ; Female ; Galactosamine ; pharmacology ; Imipenem ; pharmacology ; Lipopolysaccharides ; metabolism ; Male ; Pseudomonas Infections ; etiology ; mortality ; prevention & control ; Pseudomonas aeruginosa ; drug effects ; growth & development ; metabolism ; Rats ; Rats, Wistar ; Sepsis ; blood ; etiology ; prevention & control ; Survival Rate ; Time Factors

Objective:To compare the effects and characteristic difference of negative pressure materials of polyvinyl alcohol and polyurethane in the treatment of full-thickness burn wounds after escharotomy.Methods:From January 2018 to December 2019, 60 patients with full-thickness burns who met the inclusion criteria and hospitalized in Xuzhou Renci Hospital were recruited in this prospective randomized controlled trial. According to the random number table, 60 cases were divided into polyvinyl alcohol group ( n =30, 13 males and 17 females) and polyurethane group ( n =30, 14 males and 16 females), aged (34±7) and (35±6) years respectively, with burn area of 4.20% (2.23%, 4.90%) total body surface area (TBSA) and 3.89% (2.18%, 4.76%)TBSA and escharectomy area of 2.70% (1.97%, 3.42%) TBSA and 2.87% (2.12%, 3.34%)TBSA, respectively. After patient′s admission, debridement was immediately performed on the full-thickness burn wound, and the dressing was changed with iodophor once a day. Escharectomy was performed on post injury day 3. After thorough hemostasis and washing the wounds with normal saline, patients of the two groups chose corresponding foam materials and supporting facilities for continuous negative-pressure treatment for 1 week, with the negative pressure value setting at -19.9 kPa. Installation time of negative-pressure material was recorded. After a week of negative-pressure treatment, the maximum pulling force of removing foam material was recorded to evaluate the adhesional degree between foam materials and wounds. The amount of bleeding in the process of removing foam materials was recorded, hyperplasiaof granulation tissue was observed with hematoxylin eosin (HE) staining, and the expression of CD31 was detected by immunohistochemical staining and Western blotting to denote vascularization. The ratio of R1 to R0 of coefficient of restitution of foam material before and one week after negative-pressure treatment and drainage volume of wound exudate within a week of negative-pressure treatment were recorded to denote the drainage ability of foam material to wound exudate. One week after negative-pressure treatment, the bacterial colonization, residual foreign body, and eczema rate of skin edge were recorded. Data were statistically analyzed with chi-square test, independent-sample t test, and Mann-Whitney U test. Results:(1) Installation time of negative-pressure material of patients in polyurethane group was (14±3) min, which was significantly shorter than (18±3) min in polyvinyl alcohol group ( t=2.788, P<0.01). (2) One week after negative-pressure treatment, the maximum pulling force of removing foam material of patients in polyvinyl alcohol group was (6.4±0.4) N, which was significantly lower than (16.7±0.8) N in polyurethane group ( t=12.010, P<0.01). (3) One week after negative-pressure treatment, the volume of wound bleeding of patients in polyvinyl alcohol group was (20±3) mL in the process of removing foam material, which was significantly less than (59±3) mL in polyurethane group ( t=50.200, P<0.01). (4) One week after negative-pressure treatment, HE staining showed that hyperplastic thickness of wound granulation tissue of patients in polyurethane group was (2.3±0.6) mm which was significantly higher than (1.6±0.4) mm in polyvinyl alcohol group ( t=6.667, P<0.01); immunohistochemical staining showed that the number of microvascular lumen in wound granulation tissue of patients in polyurethane group was significantly more than that in polyvinyl alcohol group; Western blotting showed that protein expression of CD31 in wound granulation tissue of patients in polyurethane group (1.00±0.05) was significantly higher than 0.42±0.03 of polyvinyl alcohol group ( t=10.490, P<0.01). (5)The ratio of R1 to R0 of coefficient of restitution of foam material of patients in polyvinyl alcohol group was 0.39±0.19, which was significantly lower than 0.52±0.16 in polyurethane group ( t=2.975, P<0.01). In patients of polyvinyl alcohol group, the drainage volume of wound exudate of foam material during one week after negative-pressure treatment was (1 258±444) mL, significantly less than (1 658±580) mL of polyurethane group ( t=3.003, P<0.01). (6) One week after negative-pressure treatment, the number of residual foreign body in wounds of patients of polyurethane group was (14.14±0.37) particles, which was significantly more than (3.36±0.15) particles in polyvinyl alcohol group ( t=26.200, P<0.01). The level of bacterial colonization of wounds and eczema rate of skin edge of patients between the two groups were close. Conclusions:Polyurethane foam material is easy to install and operate, relatively difficult to dry and shrink, and has strong ability to discharge wound exudation. Polyurethane foam material is better than polyvinyl alcohol foam material in promoting wound angiogenesis and tissue proliferation. Polyurethane foam material can be chosen firstly for the wounds with need of protecting deep tissues and important organs, as well as the wounds with obvious inflammatory edema and serious contamination. Polyvinyl alcohol foam material is less adherent to wounds, which is better than polyurethane foam material in the aspects of reducing wound bleeding and residual foreign body. Polyvinyl alcohol foam material can be firstly selected to fix and promote skin graft survival after skin grafting, wound bed preparation before skin grafting of burn with large area and deep wound cavity or sinus, etc. Both types of foam materials need to be improved in the aspects of bacterial colonization and prevention and treatment of skin eczema.