Angiopoietin-2 enhances survival in experimental sepsis induced by multidrug-resistant Pseudomonas aeruginosa.

Levels of circulating angiopoietin-2 (Ang-2) increase in sepsis, raising the possibility that Ang-2 acts as a modulator in the sepsis cascade. To investigate this, experimental sepsis was induced in male C57BL6 mice by a multidrug-resistant isolate of Pseudomonas aeruginosa; survival was determined along with neutrophil tissue infiltration and release of proinflammatory cytokines. Survival was significantly increased either by pretreatment with recombinant Ang-2 2 h before or treatment with recombinant Ang-2 30 min after bacterial challenge. Likewise, Ang-2 pretreatment protected against sepsis-related death elicited by Escherichia coli; however, Ang-2 failed to provide protection in lipopolysaccharide (LPS)-challenged mice. The survival advantage of Ang-2 in response to P. aeruginosa challenge was lost in tumor necrosis factor (TNF)-deficient mice or neutropenic mice. Infiltration of the liver by neutrophils was elevated in the Ang-2 group compared with saline-treated animals. Serum TNF-α levels were reduced by Ang-2, whereas those of interleukin (IL)-6 and IL-10 remained unchanged. This was accompanied by lower release of TNF-α by stimulated splenocytes. When applied to U937 cells in vitro, heat-killed P. aeruginosa induced the secretion of IL-6 and TNF-α; low levels of exogenous TNF-α synergized with P. aeruginosa. This synergistic effect was abolished after the addition of Ang-2. These results put in evidence a striking protective role of Ang-2 in experimental sepsis evoked by a multidrug-resistant isolate of P. aeruginosa attributed to modulation of TNF-α production and changes in neutrophil migration. The protective role of Ang-2 is shown when whole microorganisms are used and not LPS, suggesting complex interactions with the host immune response.

Treatment of experimental osteomyelitis caused by methicillin-resistant Staphylococcus aureus with a synthetic carrier of calcium sulphate (Stimulan) releasing moxifloxacin.

The objectives of this study were to assess the efficacy of a synthetic semihydrate form of calcium sulphate (Stimulan) in experimental bone infection caused by methicillin-resistant Staphylococcus aureus (MRSA). Osteomyelitis was induced after inoculation of the test pathogen in the left tibia of 72 New Zealand rabbits assigned to the following groups: 18 control rabbits (Group A); 18 rabbits with Stimulan implanted (Group B); and 36 rabbits with moxifloxacin-impregnated Stimulan implanted (Group C). Rabbits were sacrificed at weekly intervals and cancellous bone was harvested for histopathology and for estimation of bacterial growth and concentrations of moxifloxacin. Bacterial growth from cancellous bone of Group C was significantly lower than the respective growth of Groups A and B on all days of sacrifice. The main histological finding of animals in all three groups was a moderate to intense inflammatory reaction accompanied by fibrosis. The degree of fibrosis was higher in Group C compared with both other groups. Infiltration by giant cells was also observed, which was greater in Group C on Day 42. Antibiotic levels in bone were higher for bone samples closer to the site of implantation. In conclusion, Stimulan admixed with 10% moxifloxacin was very effective in achieving complete eradication of the causative pathogen in experimental osteomyelitis caused by MRSA.

Clarithromycin is an effective immunomodulator when administered late in experimental pyelonephritis by multidrug-resistant Pseudomonas aeruginosa.

BACKGROUND: To apply clarithromycin as an immunomodulatory treatment in experimental urosepsis by multidrug-resistant Pseudomonas aeruginosa. METHODS: Acute pyelonephritis was induced in 40 rabbits after inoculation of the test isolate in the renal pelvis. Therapy was administered upon signs of sepsis in four groups: A, controls; B, intravenous clarithromycin; C, amikacin; and D, both agents. Survival and vital signs were recorded; blood was sampled for culture and estimation of pro-inflammatory mediators; monocytes were isolated for determination of apoptotic rate and ex vivo TNFalpha secretion. Quantitative cultures and biopsies of organs were performed after death. RESULTS: Increased rectal temperature and oxygen saturation were found in groups B and D compared to A and C. Mean survival of groups A, B, C and D was 2.65, 7.15, 4.25 and 8.70 days respectively. No differences were noted between groups concerning bacterial load in blood and tissues and serum endotoxins. Serum MDA and total caspase-3 activity of monocytes of group D decreased following treatment compared to other groups. Negative correlation was detected between cytoplasmic caspase-3 and ex vivo secretion of TNFalpha of blood monocytes of group A; similar correlation was not found for any other group. Pathology scores of liver and lung of group B were lower than group A. CONCLUSION: Clarithromycin administered late in experimental urosepsis by multidrug-resistant P. aeruginosa prolonged survival and ameliorated clinical findings. Its effect is probably attributed to immunomodulatory intervention on blood monocytes.

Clarithromycin is an effective immunomodulator in experimental pyelonephritis caused by pan-resistant Klebsiella pneumoniae.

OBJECTIVES: To apply clarithromycin as an immunomodulatory treatment in experimental infection caused by pan-resistant Klebsiella pneumoniae. METHODS: Acute pyelonephritis was induced in 80 rabbits after inoculation of the test isolate in the renal pelvis. Rabbits were divided into eight groups, with 10 animals in each group. In groups A-D, therapy was administered simultaneously with bacterial challenge as follows: A, controls; B, intravenous clarithromycin; C, amikacin; and D, both agents. In groups E-H, therapy was administered 24 h after bacterial challenge as follows: E, controls; F, intravenous clarithromycin; G, amikacin; and H, both agents. Blood was sampled for estimation of tumour necrosis factor-alpha (TNF-alpha) and malondialdehyde (MDA); monocytes were isolated for determination of intracellular activity of caspase-3 and ex vivo TNF-alpha secretion. Four days after bacterial challenge, animals were sacrificed for quantitative cultures and biopsies of organs. RESULTS: Serum TNF-alpha at 48 h was lower in groups B, C and D compared with group A. Activity of caspase-3 of monocytes was lower at 48 h in group D compared with group A. Bacterial loads of liver and spleen were decreased in group D compared with those of group A. The numbers of inflammatory cells of spleen of group B were lower compared with those of group A; those of kidney and mesenteric lymph nodes of group D were lower than those of group A. Serum MDA of group H was lower than that of group E and serum TNF-alpha of group F was lower compared with that of group E. TNF-alpha of monocyte supernatants and activity of caspase-3 of monocytes of group F were lower than those of group E. Bacterial tissue loads did not differ among groups E, F, G and H. The numbers of inflammatory cells of liver of groups F and H were lower compared with those of group E; those of kidney of groups F, G and H were lower compared with those of group E. CONCLUSIONS: Clarithromycin administered intravenously in experimental infection caused by pan-resistant K. pneumoniae attenuated systemic inflammatory response and local tissue damage. This effect is probably attributed to immunomodulatory intervention on blood monocytes.