Dietary Manganese Promotes Staphylococcal Infection of the Heart.

Diet, and specifically dietary metals, can modify the risk of infection. However, the mechanisms by which manganese (Mn), a common dietary supplement, alters infection remain unexplored. We report that dietary Mn levels dictate the outcome of systemic infections caused by Staphylococcus aureus, a leading cause of bacterial endocarditis. Mice fed a high Mn diet display alterations in Mn levels and localization within infected tissues, and S. aureus virulence and infection of the heart are enhanced. Although the canonical mammalian Mn-sequestering protein calprotectin surrounds staphylococcal heart abscesses, calprotectin is not released into the abscess nidus and does not limit Mn in this organ. Consequently, excess Mn is bioavailable to S. aureus in the heart. Bioavailable Mn is utilized by S. aureus to detoxify reactive oxygen species and protect against neutrophil killing, enhancing fitness within the heart. Therefore, a single dietary modification overwhelms vital host antimicrobial strategies, leading to fatal staphylococcal infection.

Experimental central nervous system aspergillosis therapy: efficacy, drug levels and localization, immunohistopathology, and toxicity.

We have shown previously that high-dose lipid amphotericin preparations are not more efficacious than lower doses in aspergillosis. We studied toxicity, drug concentrations and localization, and quantitative infection concurrently, using a 4-day model of central nervous system (CNS) aspergillosis to assess early events. Mice given Aspergillus fumigatus conidia intracerebrally, under a cyclophosphamide immunosuppressive regimen, were treated for 3 days (AmBisome at 3 or 10 mg/kg of body weight, Abelcet at 10 mg/kg, amphotericin B deoxycholate at 1 mg/kg, caspofungin at 5 mg/kg, or voriconazole at 40 mg/kg). Sampling 24 h after the last treatment showed that AmBisome at 3 but not at 10 mg/kg, as well as Abelcet, caspofungin, and voriconazole, reduced brain CFU. All regimens reduced renal infection. Minor renal tubular changes occurred with AmBisome or Abelcet therapy, whereas heart, lung, and brain showed no drug toxicity. Amphotericin B tissue and serum concentrations did not correlate with efficacy. Endothelial cell activation (ICAM-1 and P-selectin in cerebral capillaries) occurred during infection. Amphotericin B derived from AmBisome and Abelcet localized in activated endothelium and from Abelcet in intravascular monocytes. In 10-day studies dosing uninfected mice, minor renal tubular changes occurred after AmBisome or Abelcet at 1, 5, or 10 mg/kg with or without cyclophosphamide treatment; nephrosis occurred only with Abelcet in cyclophosphamide-treated mice. Hepatotoxicity occurred with AmBisome and Abelcet but was reduced in cyclophosphamide-treated mice. Marked CFU reduction by AmBisome at 3 mg/kg occurred in association with relatively more intense inflammation. Abelcet renal localization appears to be a precursor to late nephrotoxicity. Hepatotoxicity may contribute to high-dose Abelcet and AmBisome failures. Our novel observation of endothelial amphotericin localization during infection may contribute to amphotericin mechanism of efficacy.

[Cardiac involvement in adults with echinococcosis].

Experiments have established that the first target for echinococcus is the liver and lung and that for pathogenic fungi and protozoa is the heart. Adult patients with hepatic hydatid disease complicated by paecilomycosis have been found to have atypical paecilomycosis-associated myocarditis, the treatment of which was developed by the authors, by using antibiotics, fungicides, and homeopathic remedies.

Experimental analyses of synergistic combinations of antibiotics with a recently recognised antibacterial agent, lacidipine.

The cardiovascular drug lacidipine (Lc) is known to possess antibacterial activity. Further potentiation of action is possible by synergism between Lc and an antibiotic or a non-antibiotic. The minimum inhibitory concentration (MIC) of antibiotics, Lc and other non-antibiotics were detected by the agar dilution technique in different bacteria. Synergism was determined by disc diffusion assay, the fractional inhibitory concentration (FIC) index through checkerboard assessment and, also, the protective capacity of the combination by administering the drugs along with 50 x LD(50) challenge dose of virulent Salmonella typhimurium in animal experiments. Synergism between Lc and penicillin was found to be statistically significant (P

Culture-positive and culture-negative endocarditis in patients with cancer: a retrospective observational study, 1994-2004.

Endocarditis is uncommon in patients with cancer. The characteristics of culture-positive (CPE) and culture-negative endocarditis (CNE) in high-risk cancer patients are not known; therefore we sought to evaluate the disease characteristics in patients with endocarditis at a comprehensive cancer center. We retrospectively reviewed the transthoracic (TTE) and transesophageal (TEE) echocardiograms obtained from 654 consecutive cancer patients in whom endocarditis was suspected between 1994 and 2004. Endocarditis was confirmed in 45 (7%) of 654 patients using modified Duke University criteria based on information obtained from hospital records and computerized data systems. In 21 (95%) of 22 cases, TEE examinations were diagnostic, and 16 (42%) of 38 patients with initially nondiagnostic TTE studies had the diagnosis confirmed by TEE study; this difference between diagnostic TEE and initial nondiagnostic TTE was significant (p < 0.0001). Among the 26 (58%) patients with CPE, Staphylococcus aureus (35%) was the most common organism isolated, followed by coagulase-negative Staphylococcus species (23%). Eighteen (78%) of 23 patients with a central venous catheter had CPE, whereas only 8 (36%) of 22 patients without a central venous catheter had CPE (odds ratio [OR], 6.3; 95% confidence interval [CI], 1.69-23.53; p < 0.006). Vegetations were larger in patients with CPE than in patients with CNE (median +/- standard deviation, 10 +/- 8.8 vs. 8.7 +/- 3.9 mm). Fifteen patients (58%) with CPE and 10 (53%) with CNE had embolic complications. We note that cutaneous and septic pulmonary emboli were more common in patients with CPE than in patients with CNE (31% vs. 11% and 15% vs. 0%, respectively), whereas embolic cerebrovascular and fatal embolic coronary events were more common in patients with CNE than in those with CPE (37% vs. 12% and 21% vs. 0%, respectively; p = 0.026). The 4-week endocarditis-attributable death rate did not differ significantly between the groups (CPE, 15% vs. CNE, 32%; p = 0.28). On stepwise multivariate regression analysis, patients with neutropenia (OR, 22.52; 95% CI, 2.25-225.48; p < 0.008) and those with embolic cerebrovascular events (OR, 17.07; 95% CI, 1.63-178.45; p < 0.01) had an increased probability of death due to endocarditis. The clinical spectrums of CPE and CNE differed in these patients with cancer. In patients with CNE, embolic cerebrovascular and fatal myocardial infarction were relatively common.

Effect of Mesua ferrea Linn. flower extract on Salmonella.

Based on its traditional uses in folk medicine, the whole flower extract of Mesua ferrea Linn. was tested for its in vitro antimicrobial efficacy against five different strains of Salmonella spp. All the strains were found to be highly sensitive to the extract, MIC of the extract against each organism being 50 microg/ml. The extract was tested in vitro for its mode of antibacterial activity against S. Typhimurium NCTC 74 and it was found to be bactericidal in action. In vivo studies of this extract offered significant protection to Swiss albino mice at doses approximately 2 and 4 mg/mouse when challenged with 50 median lethal dose of S. Typhimurium NCTC 74. Further, the extract caused statistically significant reduction in viable count of the strain in liver, spleen and heart blood of challenged mice.

Real-time in vivo bioluminescent imaging for evaluating the efficacy of antibiotics in a rat Staphylococcus aureus endocarditis model.

Therapeutic options for invasive Staphylococcus aureus infections have become limited due to rising antimicrobial resistance, making relevant animal model testing of new candidate agents more crucial than ever. In the present studies, a rat model of aortic infective endocarditis (IE) caused by a bioluminescently engineered, biofilm-positive S. aureus strain was used to evaluate real-time antibiotic efficacy directly. This strain was vancomycin and cefazolin susceptible but gentamicin resistant. Bioluminescence was detected and quantified daily in antibiotic-treated and control animals with IE, using a highly sensitive in vivo imaging system (IVIS). Persistent and increasing cardiac bioluminescent signals (BLS) were observed in untreated animals. Three days of vancomycin therapy caused significant reductions in both cardiac BLS (>10-fold versus control) and S. aureus densities in cardiac vegetations (P < 0.005 versus control). However, 3 days after discontinuation of vancomycin therapy, a greater than threefold increase in cardiac BLS was observed, indicating relapsing IE (which was confirmed by quantitative culture). Cefazolin resulted in modest decreases in cardiac BLS and bacterial densities. These microbiologic and cardiac BLS differences during therapy correlated with a longer time-above-MIC for vancomycin (>12 h) than for cefazolin ( approximately 4 h). Gentamicin caused neither a reduction in cardiac S. aureus densities nor a reduction in BLS. There were significant correlations between cardiac BLS and S. aureus densities in vegetations in all treatment groups. These data suggest that bioluminescent imaging provides a substantial advance in the real-time monitoring of the efficacy of therapy of invasive S. aureus infections in live animals.

Susceptibility to thrombin-induced platelet microbicidal protein is associated with increased fluconazole efficacy against experimental endocarditis due to Candida albicans.

Platelet microbicidal proteins (PMPs) are believed to be integral to host defense against endovascular infection. We previously demonstrated that susceptibility to thrombin-induced PMP 1 (tPMP-1) in vitro negatively influences Candida albicans virulence in the rabbit model of infective endocarditis (IE). This study evaluated the relationship between in vitro tPMP-1 susceptibility (tPMP-1s) or resistance (tPMP-1r) and efficacy of fluconazole (FLU) therapy of IE due to C. albicans. Candida IE was established in rabbits with either tPMP-1s or tPMP-1r strains. Treatment groups received FLU (100 mg/kg/day) intraperitoneally for 7 or 14 days; control animals received no therapy. At these time points, cardiac vegetations, kidneys, and spleens were quantitatively cultured to assess fungal burden. At both 7 and 14 days and in all target tissues, the extent of candidal clearance by FLU was greater in animals infected with the tPMP-1s strain than in those infected with the tPMP-1r strain. These differences were statistically significant in the spleen and kidney. Corroborating these in vivo data, FLU (a candidastatic agent), in combination with tPMP-1, exerted an enhanced fungicidal effect in vitro against tPMP-1s and tPMP-1r C. albicans, with the extent of this effect greatest against the tPMP-1s strain. Collectively, these results support the concept that tPMP-1 susceptibility contributes to the net efficacy of FLU against C. albicans IE in vivo, particularly in tissues in which platelets and tPMP-1 likely play significant roles in host defense.

Impact of the order of initiation of fluconazole and amphotericin B in sequential or combination therapy on killing of Candida albicans in vitro and in a rabbit model of endocarditis and pyelonephritis.

In vitro time-kill studies and a rabbit model of endocarditis and pyelonephritis were used to define the impact that the order of exposure of Candida albicans to fluconazole (FLC) and amphotericin B (AMB), as sequential and combination therapies, had on the susceptibility of C. albicans to AMB and on the outcome. The contribution of FLC-induced resistance to AMB for C. albicans also was assessed. In vitro, AMB monotherapy rapidly killed each of four C. albicans strains; FLC alone was fungistatic. Preincubation of these fungi with FLC for 18 h prior to exposure to AMB decreased their susceptibilities to AMB for 8 to >40 h. Induced resistance to AMB was transient, but the duration of resistance increased with the length of FLC preincubation. Yeast sequentially incubated with FLC followed by AMB plus FLC (FLC-->AMB+FLC) showed fungistatic growth kinetics similar to that of fungi that were exposed to FLC alone. This antagonistic effect persisted for at least 24 h. Simultaneous exposure of C. albicans to AMB and FLC [AMB+FLC(simult)] demonstrated activity similar to that with AMB alone for AMB concentrations of > or =1 microg/ml; antagonism was seen using an AMB concentration of 0.5 microg/ml. The in vitro findings accurately predicted outcomes in our rabbit infection model. In vivo, AMB monotherapy and treatment with AMB for 24 h followed by AMB plus FLC (AMB-->AMB+FLC) rapidly sterilized kidneys and cardiac vegetations. AMB+FLC(simult) and FLC-->AMB treatments were slower in clearing fungi from infected tissues. FLC monotherapy and FLC-->AMB+FLC were both fungistatic and were the least active regimens. No adverse interaction was observed between AMB and FLC for the AMB-->FLC regimen. However, FLC-->AMB treatment was slower than AMB alone in clearing fungi from tissues. Thus, our in vitro and in vivo studies both demonstrate that preexposure of C. albicans to FLC reduces fungal susceptibility to AMB. The length of FLC preexposure and whether AMB is subsequently used alone or in combination with FLC determine the duration of induced resistance to AMB.

Identification of quantitative trait loci governing arthritis severity and humoral responses in the murine model of Lyme disease.

A spectrum of disease severity has been observed in patients with Lyme disease, with approximately 60% of untreated individuals developing arthritis. The murine model of Lyme disease has provided strong evidence that the genetic composition of the host influences the severity of arthritis following infection with Borrelia burgdorferi: infected C3H mice develop severe arthritis while infected C57BL/6N mice develop mild arthritis. Regions of the mouse genome controlling arthritis severity and humoral responses during B. burgdorferi infection were identified in the F2 intercross generation of C3H/HeNCr and C57BL/6NCr mice. Rear ankle swelling measurements identified quantitative trait loci (QTL) on chromosomes 4 and 5, while histopathological scoring identified QTL on a unique region of chromosome 5 and on chromosome 11. The identification of QTL unique for ankle swelling or histopathological severity suggests that processes under distinct genetic control are responsible for these two manifestations of Lyme arthritis. Additional QTL that control the levels of circulating Igs induced by B. burgdorferi infection were identified on chromosomes 6, 9, 11, 12, and 17. Interestingly, the magnitude of the humoral response was not correlated with the severity of arthritis in infected F2 mice. This work defines several genetic loci that regulate either the severity of arthritis or the magnitude of humoral responses to B. burgdorferi infection in mice, with implications toward understanding the host-pathogen interactions involved in disease development.

Reversal of Borrelia burgdorferi associated dilated cardiomyopathy by antibiotic treatment?

It is suggested that Borrelia burgdorferi infection could be associated with dilated cardiomyopathy (IDC). Stanek et al. were able to cultivate Borrelia burgdorferi from myocardial biopsy tissue of a patient with longstanding dilated cardiomyopathy. Here we present a study in which we examined the effect of standard antibiotic treatment on the left ventricular ejection fraction (LVEF) in patients with dilated cardiomyopathy associated with Borrelia burgdorferi infection. In this study we assessed the serum (IgG, IgM Elisa) and history of 46 IDC patients with specific regard to Borrelia burgdorferi infection (mean LVEF 30.4 +/- 1.3%, measured by cardiac catheterization and echocardiography with the length-area-volume method). All 46 patients received standard treatment for dilated cardiomyopathy: ACE inhibitors, digitalis, and diuretics. Eleven (24%) patients showed positive serology and a history of Borrelia burgdorferi infection; nine of these also had a typical history of tick bite and erythema chronicum migrans (ECM) and/or other organ involvement, and two had no recollection of tick bite or ECM but showed other Borrelia burgdorferi-associated disorders (neuropathy, oligoarthritis). These 11 patients with Borrelia burgdorferi infection received standard antibiotic treatment with intravenous ceftriaxone 2 g bid for 14 days. Six (55%) recovered completely and showed a normal LVEF after 6 months, three (27%) improved their LVEF, and two (18%) did not improve at all. This amounts to nine (82%) patients with recovery/improvement in the Borrelia burgdorferi group. The 35 patients who did not show positive serology or a history of Borrelia burgdorferi infection did not receive antibiotic treatment. In this group without Borrelia burgdorferi infection 12 (26%), showed recovery/improvement following the standard treatment of dilated cardiomyopathy (see earlier). Our results indicate that Borrelia burgdorferi infection could play a decisive role in the development of dilated cardiomyopathy, especially in a geographical region such as Graz, where Borrelia burgdorferi is endemic. While we are aware of the small number of Borrelia burgdorferi patients in this study, we nevertheless conclude that in a remarkable number of patients with signs of Borrelia burgdorferi infection, dilated cardiomyopathy could be reversed and LVEF improved.

Increased virulence of a human enterovirus (coxsackievirus B3) in selenium-deficient mice.

Coxsackievirus B3 (CVB3/20)-induced myocarditic lesions occurred more quickly and were more severe and virus titers in heart and liver were higher in selenium (Se)-deficient than Se-adequate mice. NK cell activity and serum neutralizing antibody titers were similar in both Se-adequate and -deficient CVB3/20-infected mice; however, lymphocyte proliferation to both mitogen and antigen was decreased in Se-deficient mice. CVB3/20 isolated from Se-deficient donor mice and inoculated into Se-adequate recipient mice induced severe myocarditis. In contrast, CVB3/20 isolated from Se-adequate donor mice and inoculated into Se-adequate recipient mice induced only moderate myocarditis, similar to that caused by the original virus stock. Thus, the general population of CVB3/20 virions, as a consequence of replicating in an Se-deficient host, underwent a phenotypic change to increased virulence. These results have important implications for the emergence of virulent viruses.

Efficacy of cefepime in a Staphylococcus aureus endocarditis rat model.

The efficacy of cefepime, a new broad-spectrum cephalosporin, was compared with those of cefpirome, ceftazidime, vancomycin, imipenem-cilastatin and penicillin G in a rat model of endocarditis caused by a methicillin-susceptible strain of Staphylococcus aureus. Rats were infected intravenously with approximately 10(5) cfu of a penicillin-resistant strain of S. aureus 24 h after placement of a catheter into the left ventricle of the heart via the carotid artery. Efficacy was evaluated by comparing bacterial counts in the cardiac vegetations of treated rats with those of untreated controls. Rats treated with cefepime, cefpirome, ceftazidime, imipenem-cilastatin and vancomycin showed a reduction in the number of bacteria recovered from cardiac vegetations compared with infected control animals; penicillin G was ineffective in this respect. Serum concentrations of the study antimicrobials were determined at selected times following the administration of a single subcutaneous dose. The pharmacokinetic parameters of the cephalosporins were similar in these animals. This study shows that cefepime may be of value in the treatment of staphylococcal endocarditis.

Comparison of fluconazole and amphotericin B for treatment of experimental Candida endocarditis caused by non-C. albicans strains.

Amphotericin B and fluconazole were compared for the treatment of experimental Candida endocarditis caused by Candida tropicalis and C. parapsilosis. Rabbits received no therapy, amphotericin B (1 mg/kg of body weight per day intravenously), or fluconazole (100 mg/kg/day intraperitoneally) for either 11 or 21 days. Against both species, amphotericin B and fluconazole were equally effective overall; however, amphotericin B was more rapidly fungicidal than fluconazole in vivo against C. tropicalis.

Efficacy of clarithromycin for treatment of experimental Lyme disease in vivo.

Clarithromycin provided effective therapy against arthritis induced by Borrelia burgdorferi infection in the hamster. In vitro, clarithromycin was at least 1 log more potent than tetracycline against two isolates of B. burgdorferi from human sources, as measured by MICs and 50% inhibitory concentrations. Clarithromycin was effective in preventing the onset of B. burgdorferi-induced arthritis, as determined by several parameters of paw swelling. When administered after the onset of arthritis, clarithromycin therapy reduced the degree of swelling and decreased recovery time. These results suggest that clarithromycin has potential as an effective therapy for Lyme disease.

Pathogenesis and chemotherapy of experimental Legionella pneumophila infection in the chick embryo.

The pathogenicity of Legionella pneumophila, serogroup 1, strain Nottingham N7, was assessed in terms of LD50 data and the ability of the organism to induce pathological lesions in the fertile hen's egg. Histopathological examination of embryo organs after inoculation with 1, 10, 100 and 1000 times the yolk sac LD50 revealed a disseminated infection. Systemic spread of the organism resulted in widespread necrosis and evidence of consolidation together with generation of copious amounts of oedema fluid. These were particularly severe in the liver, heart, spleen and kidney. The infection elicited a massive inflammatory response typified by infiltration with polymorphonuclear leucocytes and lymphocytes. Selected antimicrobial chemotherapeutic agents were investigated in protection studies for their capacity to ameliorate or control disease processes in this test system. Of those examined ciprofloxacin was most effective in reducing the incidence of lesions in these tissues and for prolonging embryo viability. Rifampicin, and to a lesser degree, erythromycin and doxycycline, also showed antimicrobial activity in these in vivo trials. These results indicate that the fertile hen's egg may be a useful alternative to other animal systems for the in vivo testing of clinically putative antimicrobial agents in the treatment of Legionnaires' disease.

Experimental endocarditis in rabbits. 5. Results of long-term penicillin or streptomycin treatment of streptococcus faecalis endocarditis and the effect of long-term exposure of healthy rabbits to the same drugs.

A previously described model of experimental Streptococcus faecalis endocarditis in rabbits without an indwelling catheter during the infectious processes was used to study the effect of long-term treatment with antibiotics. Groups of animals infected with six different strains were treated for four weeks and the following parameters were determined: survival rate, bacterial concentration in blood and vegetations, signs at autopsy indicating congestive heart failure. Before the therapeutic experiments, the tolerance of the rabbit to long-term exposure of the drugs penicillin and streptomycin was considered in a group of non-infected animals. Two out of 20 rabbits died with enteritis during the penicillin exposure, and a general weight reduction was observed. Streptomycin was apparently completely harmless. There was no therapeutic effect of streptomycin on S. faecalis endocarditis due to strains all designated resistant to streptomycin by MIC, except in rabbits infected with a strain, which showed partial susceptibility to the drug by IC50. Regardless of the therapeutic effect, evidence was obtained for rapid development of increased resistance of the infecting strains towards streptomycin. After long-term treatment with penicillin in either low or high dose some of the animals survived and the valves were sterilized in 37% of the animals after low-dose and in 39% after high-dose. It was observed that congestive heart failure occurred with the greatest frequency and intensity after infection with proteolytic strains.

Experimental endocarditis in rabbits. 6. Results of long-term combined therapy of Streptococcus faecalis endocarditis with penicillin and streptomycin.

The synergistic action of penicillin and streptomycin was investigated on animals with experimental endocarditis, using the previously described model and four different strains of Streptococcus faecalis. Two strains represented a moderate and two strains a high level of resistance to streptomycin. The purpose was to determine the effect of the combined penicillin and streptomycin treatment, since previous in vitro investigations showed that strains highly resistant to streptomycin were also resistant to combination of the drugs. Antibiotic treatment of the animals was carried out for 28 days, followed by a period of four weeks observation. The treatment resulted in a demonstrable effect against infection caused by the least streptomycin-resistant strain, but was completely ineffective in rabbits infected with the strain homogeneously resistant to 8000 micrograms/ml streptomycin. The synergistic effect of penicillin and streptomycin towards strains within a range of streptomycin resistance of 2000-8000 micrograms/ml could be predicted by the IC50 test, but not by MIC or the in vitro killing curve test for synergism. Besides the therapeutic results, this report also considers the following features: pathoanatomic and physiologic processes related to the number of viable bacteria in the endocardial vegetations; the influence of the proteolytic capacity of infecting strains; the development of congestive heart failure.

Interaction of air pollution and hyperbaric oxygen on virus replication.

A study was undertaken to weigh the effects of air pollution and oxygen at high pressure on the susceptibility of mice to Coxsackievirus B1 infection. Animals exposed to air pollutants or oxygen at high pressure were found to contain higher amounts of recoverable virus than control animals. Animals exposed to both air pollutants and oxygen at high pressure were found to contain the greatest levels of recoverable virus. This same group of animals was also found to have hearts which were smaller than any other group. Animals maintained in an ambient atmosphere had higher levels of recoverable virus and smaller hearts than animals exposed to terpene vapors and hyperbaric oxygen. The results of this study suggest that terpene vapors may nullify the activity of oxygen at high pressure.