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

High prevalence of dental erosion has been reported in recent years. The prevention and treatment of dental erosion has therefore attracted lots of attention in dentistry. Matrix metalloproteinases (MMPs) is a type of proteolytic enzyme containing Zn2+ and Ca2+, which can degrade organic matrix in advanced dental erosion. MMPs inhibitors were reported to have the potential to prevent the organic matrix of dentin from degradation, which might provide protective capacity against dental erosion. The present article reviews the mechanism and potential application of MMPs inhibitors in the prevention and treatment of dental erosion.

Objective: To evaluate the effects of quercetin on dentin resistance to erosion and provide evidence-based recommendations for the prevention and therapy of dental erosion. Methods: One hundred and twenty-eight dentin samples were prepared from 50 extracted human wisdom teeth (collected from Department of Oral Surgery, School and Hospital of Stomatology). Ninety-six samples were randomly divided into 8 groups using the following different soaking solutions: deionized water, ethanol (control groups), 12.300 mg/L sodium fluoride, 0.120 mg/L chlorhexidine, 0.183 mg/L epigallocatechin gallate (EGCG), and 0.075, 0.150 and 0.300 mg/L quercetin. In each group, twelve specimen was prepared. Before daily acid challenge, the samples were immersed in the respective solutions for 2 min, rinsed with deionized water, and immersed in artificial saliva for 2 h. The samples were then subjected to 4 cycles of in vitro acid challenges. This protocol was applied for 7 d. The surface microhardness (SMH) and surface profiles were measured before and after erosion using the surface microhardness tester and contact profilometry, respectively. The change in surface profiles and reduction in SMH were used to calculate the substance loss and reduction percentage of SMH (SMH%) respectively. Scanning electron microscope (SEM) images were taken to observe the surface morphology of the samples. Additionally, another thirty two samples were divided into 8 groups (n=4) as mentioned above. The specimens were treated with 10% phosphoric acid and desiccated, immersed in the respective solutions for 2 min, rinsed, and immersed in the artificial saliva at 37 ℃ for 7 d. The content of cross-linked carboxyterminal telopeptide of type Ⅰ collagen (ICTP) in the soaking solutions were measure quantitatively. Results: Compared with the control groups, the application of chlorhexidine, quercetin, and EGCG were effective in preventing the surface softening and substance loss of human dentin after erosion. More specifically, the specimens treated with 0.300 mg/L quercetin exhibited the lowest SMH% [(8.75±4.95)%], the lowest surface substance loss [(2.26±1.16) μm], and the lowest contents of ICTP in the soaking solution [(5.72±0.88) ng], showing significant differences to the chlorhexidine and EGCG treated samples (P<0.05). No significant differences were found in the substance loss and ICTP contents in the three soaking solutions with different concentrations of quercetin(P>0.05). However, the specimens treated with 0.300 mg/L quercetin exhibited significantly lower SMH% than those treated with the other two concentrations of quercetin (P<0.05). Conclusions Within the limitations of the current study, immersion in the quercetin solution is effective in improving the dentin resistance to erosion by inhibiting the dentinal MMP. Among all the concentrations tested, 0.300 mg/L quercetin showed the best performance.