Ismini Donta

Improvement of skin-graft survival after autologous transplantation of adipose-derived stem cells in rats

BACKGROUND Skin grafts are frequently used for a variety of indications in plastic and reconstructive surgery. Their necrosis is a common complication, while different therapies have been proposed. Currently, adipose-derived stem cells (ASCs) hold great promise for their angiogenic potential and role during tissue repair. In this study, autologous transplantation of ASCs was used in skin grafts in rats to determine if it increases angiogenesis, skin-graft survival and wound healing. METHODS ASCs were isolated, cultured, labelled with fluorescent dye and injected under full-thickness skin grafts in 10 rats (group 1), while 10 others served as controls (group 2). Skin grafts were analysed after 1 week. Collagens framework was assessed with Massons trichrome stain and angiogenesis with von Willebrand factor (vWF) immunohistochemistry. In addition, immunohistochemical staining intensity of vascular endothelial growth factor (VEGF) and transforming growth factor b3 (TGFb3) was assessed in all grafts. RESULTS Mean area of graft necrosis was significantly less in group 1 than in group 2 (6.12% vs. 32.62%, p<0.01). Statistically significant increase of microvessel density, collagen density, VEGF and TGFb3 expression was noted in group 1 compared with group 2 (all: p<0.01). CONCLUSIONS These findings suggest that autologous ASCs transplantation increases full-thickness skin-graft survival and shows promise for use in skin-graft surgery. This might be both due to in situ differentiation of ASCs into endothelial cells and increased secretion by ASCs of growth factors, such as VEGF and TGFb3 that enhance angiogenesis and wound healing.

Vancomycin or vancomycin plus netilmicin for methicillin- and gentamicin-resistant Staphylococcus aureus aortic valve experimental endocarditis.

Using a rabbit model of aortic valve endocarditis, we studied the efficacy of vancomycin alone or in combination with netilmicin and/or rifampin against a methicillin- and gentamicin-resistant strain of Staphylococcus aureus (MGRSA). Antibiotics were given for 6 to 12 days, as follows: vancomycin (15 mg/kg of body weight every 12 h [BID] intravenously), vancomycin plus netilmicin (2.5 mg/kg BID intramuscularly), vancomycin plus rifampin (10 mg/kg BID intramuscularly), and vancomycin plus netilmicin plus rifampin at the same routes, dosages, and schedules mentioned above. Netilmicin was given to two additional groups at a higher dosage (6 mg/kg every 24 h intramuscularly) alone or in combination with vancomycin (15 mg/kg BID intravenously) for 12 days. All regimens resulted in undetectable bacterial counts in a significant proportion of vegetations (except netilmicin alone) or reduced the bacterial counts in the vegetations compared with the counts in the untreated controls (P<0.01 to P<0.001). No resistance to rifampin or netilmicin developed during therapy. It is concluded that in the treatment of experimental aortic valve endocarditis caused by MGRSA (i) vancomycin as monotherapy is as efficacious as the triple combination, (ii) the addition of netilmicin (once daily or BID) to vancomycin does not improve the efficacy of the latter antibiotic, even in the presence of rifampin, and (iii) a 12-day course in more effective than a 6-day one, but not at a statistically significant level.

Efficacy of ceftazidime and aztreonam alone or in combination with amikacin in experimental left-sided Pseudomonas aeruginosa endocarditis.

The in vivo efficacies of ceftazidime, aztreonam, and the combinations of ceftazidime with amikacin and aztreonam with amikacin were studied in the rabbit left-sided endocarditis model by using two strains of Pseudomonas aeruginosa, one multisusceptible and one multiresistant, in a total of 156 animals. Antibiotics were given intramuscularly for 10 days, as follows: amikacin, 7 mg/kg of body weight every 8 h, and ceftazidime and aztreonam, 50 mg/kg every 8 h. All regimens except amikacin alone significantly reduced the number of CFU per gram of vegetation (P < or = 0.008), but only for the multisusceptible strain for which sterile vegetations were obtained in 20, 25, 21, 75, and 53% of the groups treated with amikacin, ceftazidime, aztreonam, and the combination groups ceftazidime-amikacin and aztreonam-amikacin, respectively (ceftazidime plus amikacin versus controls, P = 0.001). Regarding the decrease in the numbers of colonies in vegetations, (i) all regimens significantly reduced the number of CFU per gram of vegetation (P < 0.001), (ii) results with ceftazidime-amikacin compared with those with monotherapy were significantly different (P < or = 0.007), and (iii) results with aztreonam-amikacin, although better than those with monotherapy, were marginally not statistically significant. At 1 h postdose, mean amikacin, aztreonam, and ceftazidime levels in serum were 35 +/- 19.4, 89.6 +/- 8.16, and 92.61 +/- 11.52 micrograms/ml, respectively. It was concluded that the combination of ceftazidime, and possibly aztreonam, with amikacin given at high doses and short intervals could have a place in the therapy of patients with left-sided endocarditis caused by P. aeruginosa.

Impact of Graded Hypothermia on Coagulation and Fibrinolysis

BACKGROUND Hypothermia has a detrimental effect on hemostatic mechanism. The purpose of this experimental study was to investigate the effect of graded hypothermia on markers of the anticoagulant system (antithrombin III and protein C) and fibrinolytic system (plasminogen, α(2)-antiplasmin), and on vascular wall and other tissue specimens. MATERIALS AND METHODS Ten New Zealand rabbits were subjected to mild and then moderate core hypothermia of 32 °C for 60 min. Blood samples were obtained at normothermic (T(1)), mild (T(2)), and moderate (T(3)) hypothermic conditions. Chromogenic assay methods were used to determine quantitatively (%) the activity of antithrombin III, protein C, plasminogen, and α(2)-antiplasmin. Hypothermic values were compared with the normothermic values. Tissue and vessel wall specimens were examined under light microscope. RESULTS Reduction of activity (%) from normothermia (T(1)) to mild (T(2)) and moderate (T(3)) hypothermia was found for antithrombin III (103.40 ± 12.54, 87.40 ± 13.50, and 82.70 ± 20.78, respectively, with statistically significant difference between T(1)-T(3): P = 0.03), for protein C (70.1 ± 7.51, 56.30 ± 8.34, and 53.1 ± 7.34, with statistically significant difference between T(1)-T(2) and T(1)-T(3): P = 0.015 for both comparisons) and α(2)-antiplasmin (97 ± 9.63, 80.60 ± 11.73, and 83.70 ± 13.94, with statistically significant difference between T(1)-T(2): P = 0.006). Plasminogen activity was increased (14.50 ± 0.52, 16.30 ± 1.63, and 17.30 ± 2.45, with statistically significant difference between T(1)-T(2) and T(1)-T(3): P = 0.033 for both comparisons). Histologic examination revealed no significant lesions on tissue and vessel wall specimens. CONCLUSIONS The results of our study suggest that even though the hypothermia period was relatively short, the processes of coagulation and fibrinolysis were altered with simultaneous changes.

Evidence of Less Severe Aortic Valve Destruction after Treatment of Experimental Staphylococcal Endocarditis with Vancomycin and Dexamethasone

ABSTRACT The beneficial effects of therapy combining an antibiotic and dexamethasone have been reported in human studies on meningitis and in experimental studies on septic arthritis, nephritis, and endophthalmitis. Since most patients with staphylococcal endocarditis need a combination of medical and surgical treatment, the purpose of this study was to determine whether the addition of dexamethasone to vancomycin has any beneficial effect regarding the degree of valve tissue damage or the course of experimental aortic valve endocarditis caused by a methicillin-resistant strain of Staphylococcus aureus. Rabbits with catheter-induced aortic valve vegetations were randomly assigned to a control group and to groups receiving dexamethasone (0.5 mg/kg of body weight, intravenously [i.v.], twice a day [b.i.d]), vancomycin (30 mg/kg, i.v., b.i.d), or dexamethasone plus vancomycin, for a total of 10 doses (two doses per day for 5 days). The severity of valve tissue damage was significantly less in groups receiving vancomycin plus dexamethasone compared with that of the group receiving vancomycin alone (P < 0.001). The severity of tissue damage was inversely correlated with the mean polymorphonuclear leukocyte number in valve tissue. No statistically significant differences were observed between the vancomycin-treated group and the vancomycin-plus-dexamethasone-treated group in survival, blood culture sterilization rate, or reduction of the microbial burden (in CFU per gram) in valvular tissue. In conclusion, treatment with a combination of vancomycin and dexamethasone for 5 days reduces the severity of valve tissue damage in experimental staphylococcal aortic valve endocarditis. These findings could have significant implications in the treatment of staphylococcal endocarditis and deserve further confirmation in clinical trials.

Successful single-dose teicoplanin prophylaxis against experimental streptococcal, enterococcal, and staphylococcal aortic valve endocarditis.

Teicoplanin is a glycopeptide antibiotic that is administered both intramuscularly and intravenously. It has a prolonged half-life and a less toxic profile in comparison to those of vancomycin. The efficacy of a single dose of teicoplanin (18 mg/kg of body weight given intramuscularly) for the prevention of endocarditis due to Streptococcus oralis, Enterococcus faecium, and methicillin-resistant Staphylococcus aureus (MRSA) was evaluated after applying the rabbit model. Vancomycin at a single dose of 30 mg/kg given intravenously was used as the comparative agent for the prevention of endocarditis due to MRSA and E. faecium, while ampicillin at a single dose of 40 mg/kg given intravenously was used as the comparative agent for the prevention of endocarditis due to S. oralis. Rabbits in the teicoplanin group were infected at 1 h postdosing with approximately 10(7) CFU of each strain. Rabbits in the other groups were infected at 0.5 h postdosing with approximately 10(7) CFU of S. oralis (ampicillin group) or E. faecium and MRSA (vancomycin group). All rabbits were sacrificed 5 days later. Teicoplanin and vancomycin protected the animals challenged with E. faecium by 87.5 and 50%, respectively, and protected the animals challenged with MRSA by 100 and 92%, respectively. Teicoplanin and ampicillin protected the animals challenged with S. oralis by 100 and 77%, respectively. Prevention of endocarditis by teicoplanin was likely to be due to a prolonged inhibition of bacterial growth by the sustained supra-MICs. It is concluded that teicoplanin is very effective in preventing experimental streptococcal, enterococcal, and staphylococcal endocarditis and may be an attractive alternative antibiotic in patients allergic to beta-lactams, especially in the outpatient setting.

Single-Oral-Dose Azithromycin Prophylaxis against Experimental Streptococcal or Staphylococcal Aortic Valve Endocarditis

ABSTRACT Azithromycin and ampicillin protected 94 and 72% of animals challenged with Streptococcus oralis, respectively (P = 0.177), while azithromycin and vancomycin protected 59 and 94% of the methicillin-resistant Staphylococcus aureus (MRSA)-challenged animals, respectively (P = 0.018). Azithromycin is effective in preventing experimental streptococcal endocarditis, but against MRSA it is less effective than vancomycin.

A diet rich in monounsaturated fatty acids improves the lipid profile of mice previously on a diet rich in saturated fatty acids.

This study investigated whether switching from a diet rich in saturated fatty acids (SAFAs) to a diet rich in monounsaturated fatty acids (MUFAs) or to one with equal amounts of MUFAs-SAFAs favorably affects the lipid profile of hypercholesterolemic mice. C57BL/6 mice (n = 82) were allocated into 4 groups. The first group (control, n = 10) was fed standard chow. The 3 remaining groups (n = 24 mice/group) were fed a SAFA-rich diet for 8 weeks and were then allocated for 16 weeks to either a MUFA-rich diet, an equal in MUFAs-SAFAs-rich diet, or continued the previous SAFA-rich diet. After 8 weeks, mice consuming SAFA-rich diet had increased weight, total cholesterol (TC), and high-density lipoprotein cholesterol (HDL-C) levels (P < .05 vs baseline). At week 24, MUFA-rich and MUFA-SAFA rich diets decreased TC and low-density lipoprotein cholesterol (LDL-C) levels (P < .05) compared with week 8. In conclusion, switching to MUFA-rich diets or substituting half of the SAFAs with MUFAs can reverse diet-induced-hypercholesterolemia.

Successful treatment with moxifloxacin of experimental aortic valve endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA)

Moxifloxacin (MXF) is an 8-methoxyquinolone with high activity against Gram-positive bacteria. In an experimental model of aortic valve endocarditis (EAVE), the efficacy of MXF was evaluated against a strain of methicillin-resistant Staphylococcus aureus (MRSA). Rabbits with catheter-induced aortic valve vegetations were randomly assigned to a control group or to groups receiving MXF 20 mg/kg intravenous (i.v.) twice a day (bid) or vancomycin (VAN) 30 mg/kg i.v. bid for a total of eight doses (4 days). Rabbits were sacrificed 15 h after the last dose of antibiotics. In another group, treatment with MXF was extended to 5 days and rabbits were sacrificed 5 days after the last dose (10th dose) of MXF in order to detect possible relapses of endocarditis after the end of treatment (test-of-cure (TOC) study). Both MXF and VAN significantly reduced the bacterial load in vegetations (P < 0.001 vs. controls). All animals in the MXF-TOC group had sterile vegetations. MXF given at a dose of 20 mg/kg i.v. bid for 4 days was equally effective as VAN in the treatment of EAVE due to MRSA. When treatment with MXF was extended to 5 days, the cure rate reached 100% and no relapses of endocarditis were observed.

Efficacy of Teicoplanin, Administered in Two Different Regimens, in the Treatment of Experimental Endocarditis Due to Enterococcus faecalis

Abstract Using a rabbit model of endocarditis, we studied the efficacy of teicoplanin against a strain of Enterococcus faecalis resistant to ampicillin. Rabbits were randomly assigned to receive no antibiotics, teicoplanin 12 or 18 mg/kg of body weight every 12h, for 9 days. The effect of treatment on bacterial counts of vegetations and survival of the animals was evaluated at the end of treatment and 10 days thereafter. The two treatment regimens of teicoplanin produced peak serum levels 18.51±1.84 and 34.66±4.19 μg/ml, and trough levels above 10×MIC of teicoplanin for the infecting organism. Both regimens resulted in significant bacterial reduction in the vegetations as compared to the control group (p<0.001). The drug prevented relapse of the infection 10 days after discontinuation of treatment. By increasing the teicoplanin dosage no additional therapeutic benefit was observed in terms of bacterial killing, sterilization of the vegetations, and survival of the animals, although the higher doses gave numerically superior results. These findings may have meaning for the optimum use of teicoplanin in the treatment of enterococcal endocarditis.