Microbiological findings in febrile neutropenia

BACKGROUND

This study was carried out to assess the isolation rate of bacterial and fungal causative agents in Mexican neutropenic adults with hematological neoplasia.

METHODS

A prospective observational survey involving 120 consecutive episodes of febrile neutropenia during 1 year was carried out. These episodes were observed in 630 patients discharged with diagnoses of leukemia or lymphoma, or after bone-marrow transplantation.

RESULTS

At least one pathogen was isolated in 42 of 120 episodes (35%), and was present in 39 patients with acute myeloid leukemia (AML) (43%), acute lymphoblastic leukemia (ALL) (23%), and in patients who underwent bone-marrow transplantation (20%). Primary bacteremia was the most frequent cause of fever (24 episodes, 57%), followed by intravascular device-related infections (5 episodes, 17%), and soft-tissue infections (5 episodes, 15%). Escherichia coli (33%) was the most frequently isolated agent of primary bacteremia, followed by coagulase-negative Staphylococcus (29%), and Klebsiella oxytoca (16%). Fungal infection was responsible for five events (4%): two episodes of pneumonia (Penicillium marneffei and Aspergillus fumigatus, one event each); two cases of fungemia, one due to Candida tropicalis and one to Rhodotorula gluttinis, and one cryptococcal meningitis event.

CONCLUSIONS

The isolation rate, approximately 30%, was in accordance with previous reports; similar percentages of Gram-positive and Gram-negative isolates were found. A remarkably low rate of viridans group streptococci and fungal agents was observed, despite the fact that neutropenia is the main risk factor for infection due to these agents. Studies reporting local microbiological findings are necessary because they support an antibiotic choice for prophylaxis or therapy more accurately than reports from other areas.

Bacteremic and nonbacteremic pneumococcal pneumonia. A prospective study

We prospectively identified cases of pneumococcal pneumonia and used stringent criteria to stratify them into bacteremic and nonbacteremic cases. Although patients were distributed among racial groups in proportion to all patients seen at this medical center, the proportion of African-Americans with bacteremic disease was significantly increased. All patients had at least 1 underlying condition predisposing to pneumococcal infection, and most had several. Although the mean number of predisposing factors was greater among bacteremic patients than nonbacteremic patients, only alcohol ingestion was significantly more common. Nearly one-third of patients had substantial anemia (hemoglobin < or = 10 g/dL) on admission, which may have predisposed to infection. In the case of other laboratory abnormalities, such as albumin, creatinine, and bilirubin, it was difficult to determine which abnormality might have predisposed to pneumococcal infection and which might have resulted from it. The radiologic appearance was varied. Airspace consolidation and air bronchogram on chest X-ray were highly associated with bacteremic disease, as was the presence of pleural effusion. Although the Pneumonia Patient Outcomes Research Team (PORT) risk score was a predictor of mortality, it did not help to predict the presence of bacteremia in an individual case. Most patients who died in the first week in hospital were bacteremic, and a high PORT risk score with bacteremia reliably predicted a high likelihood of a fatal outcome. Eleven patients had extrapulmonary disease with meningitis, empyema, and septic arthritis predominating; all of these patients were bacteremic. The antibiotic susceptibility of our strains correlated well with those that have been reported in the United States during the years of this study. The use of numerous antibiotics of different classes in many patients, especially those who were the most ill, precluded analysis of outcome based on antibiotic therapy. Only 17 patients had been vaccinated. Since nearly all patients had conditions for which pneumococcal vaccine is recommended and more than one-third had been hospitalized in the preceding 6 months, the low rate of vaccination can be regarded as a missed opportunity to administer a potentially beneficial vaccine.

Symptomatic and health status outcomes in the Canadian randomized MAC treatment trial (CTN010). Canadian HIV Trials Network Protocol 010 Study Group

Our objective was to compare the effect of 2 regimens for treatment of Mycobacterium avium complex (MAC) bacteraemia in an HIV-positive population on symptoms and health status outcomes using a substudy of an open-label randomized controlled trial. The study was conducted in 24 hospital-based human immunodeficiency virus (HIV) clinics in 16 Canadian cities. Patients had HIV infection and MAC bacteraemia and were given either rifampin 600 mg, ethambutol 15 mg/kg daily, clofazimine 100 mg daily and ciprofloxacin 750 mg twice daily (4-drug arm) or rifabutin 600 mg daily (amended to 300 mg daily in mid-trial), ethambutol 15 mg/kg daily and clarithromycin 1000 mg twice daily (3-drug arm). The primary health status outcome was the change on the 8-item symptom subscale of the Medical Outcome Study (MOS)-HIV Health Survey adapted for MAC. Changes on other MOS-HIV subscales and on the Karnofsky score were also evaluated. Patients on the 3-drug arm had better outcomes on the MOS-HIV symptom subscale at 16 weeks (P=0.06), with statistically significant differences restricted to night sweats and fever and chills (P < 0.001). The proportion of patients improving on the symptom subscale relative to baseline was 55% on the 3-drug arm and 40% on the 4-drug arm. Patients on the 3-drug arm also had better Karnofsky score at 16 weeks (P < 0.001) and better outcomes on the social function, mental health, energy/fatigue, health distress and cognitive function subscales of the MOS-HIV. The 3-drug arm is superior to the 4-drug arm in terms of impact on MAC-associated symptoms, functional status and other aspects of health status.

Meningococcal septicaemia and plastic surgery--a strategy for management

Meningococcal septicaemia is a severe life threatening illness that is part of the spectrum of meningococcal disease. It is of particular concern to the plastic and reconstructive surgeon because as the medical and intensive care of these patients improves, more are surviving the acute phase of the septicaemia and suffering from the associated complications such as skin necrosis and extremity loss. Recently there have been several reports in the literature concerning the management of skin infarction with both skin grafting and free flap surgery. This paper will provide an update on the proposed pathophysiological mechanisms involved, summarise the present data on plastic surgical care and suggest a stratagem for future management of these difficult cases.

Brucella bacteraemia: clinical and laboratory observations in 160 patients

OBJECTIVES

To describe the clinical, serological, and prognostic features of bacteraemic brucellosis in an endemic region.

METHODS

Retrospective case series of 160 patients admitted from 1983 to 1995 to a hospital providing secondary and tertiary level medical care in Saudi Arabia. All patients had positive blood cultures for Brucella species, predominantly Brucella melitensis.

RESULTS

Bacteraemia was documented in 38% of 545 cases of brucellosis admitted to our institution during the study period. The main clinical syndromes were febrile illness alone (44%) or fever with arthritis (42%). Of 68 isolates that were speciated, 93% were Brucella melitensis. Initial agglutinating antibody titre was > or =1:320 in 96% of the patients. Antimicrobial resistance of B.melitensis isolates was: co-trimoxazole, 29%; rifampicin, 3.5%; streptomycin, 0.6%; and tetracycline, 0.6%. No increase in resistance was noted over the 13-year study period. Commonly used antimicrobial regimens consisted of streptomycin plus tetracycline or rifampicin plus doxycycline given for 6 weeks. Seven patients (5%) had relapse of their symptoms after antimicrobial therapy. Three of these had infective endocarditis with repeated bacteraemia. These patients required aortic valve replacement and recovered after surgery. The remaining four patients responded to a second course of therapy.

CONCLUSIONS

Brucella bacteraemia is an acute febrile disease often associated with rheumatologic complaints. Most patients have an agglutinating antibody titre > or =1:320 and respond well to standard chemotherapy regimens with low mortality.

Intravascular catheter-associated infections

Serious infections associated with intravascular catheters are common. The available data suggests there are likely to be more than 500 000 cases of catheter-associated bloodstream infections occurring annually in Western Europe and the USA. These may be associated with as many as 100 000 deaths. The pathophysiology of this common condition is still not fully elucidated. With catheters that are in place for short periods (a few days), microbial migration down the outer surface of the device to the intravascular tip predominates. For catheters that are in place for longer periods, migration occurs more often via the internal lumen. After being in place for more than 8 days, nearly all central vein catheters will have microorganisms embedded in a biofilm within the catheter lumen. In some catheters, microorganisms will proliferate to sufficient numbers for systemic sepsis to result. The occurrence and rate of this proliferation is dependent on microbial virulence factors, host factors, and characteristics of the catheter. Diagnosis of intravascular device-associated sepsis remains problematic because the pathophysiology of the condition changes with time and because standard culture techniques rarely detect organisms embedded in biofilms. The semiquantitative roll method on blood agar remains in common use because of its simplicity. However, the method only samples the external surface of the catheter. For catheters that have been in place for extended periods of time, methods that better sample the internal lumen, such as sonication and quantitative broth methods, should be developed and used.

Dexamethasone blocks sepsis-induced protection of the heart from ischemia reperfusion injury

Previous investigations have shown that sepsis, while causing cardiac dysfunction, can protect the heart from ischemia-reperfusion injury. Sepsis-induced protection may be due to nitric oxide produced by an inducible form of nitric oxide synthase generated in response to cytokines released during sepsis. The glucocorticoid dexamethasone has been shown to inhibit the synthesis of the inducible form of nitric oxide synthase (iNOS). The goals of this study were to determine if dexamethasone would prevent sepsis-induced cardiac dysfunction and sepsis-induced protection of the heart from ischemia-reperfusion injury. In this experiment, rats were made septic by injecting Escherichia coli into the dorsal subcutaneous space. Control rats were injected with sterile saline. At the time of surgery, some of the control and septic animals were injected intraperitoneally with dexamethasone (3 mg/kg). The next day, 24-26 hr after injection of the first dose of E. coli, animals were anesthetized, and hearts were removed and studied in the isovolumic beating-heart preparation. Left ventricular end diastolic pressure was set to 5 mmHg, and left ventricular pressure was measured continuously throughout the protocol. Left ventricular developed pressure (LVDP) was used as an index of LV function. After stabilization, hearts were made globally ischemic for 35 min and then reperfused for 25 min. As has been shown previously, sepsis depressed LVDP but also protected the heart from further depression of LVDP by ischemia and reperfusion. Dexamethasone prevented both sepsis-induced cardiac dysfunction and sepsis-induced protection of the heart from ischemia-reperfusion injury. In addition plasma nitrite/nitrate levels were not different from control levels in the dexamethasone-treated septic rats whereas levels were elevated in the septic animals. The dexamethasone mediated abrogation of sepsis-induced cardiac dysfunction and protection during ischemia-reperfusion injury may be due to suppression of nitric oxide production.

Modulation of systemic hemodynamics by exogenous L-arginine in normal and bacteremic sheep

OBJECTIVE

To investigate whether exogenous L-arginine, the substrate for nitric oxide synthase, modulates systemic hemodynamics in sepsis.

DESIGN

Prospective, controlled study in a sheep model of sepsis.

SETTING

Animal research facility in a university hospital.

SUBJECTS

Adult sheep weighing between 35 and 55 kg.

INTERVENTIONS

Adult sheep sedated and mechanically ventilated, were monitored with a pulmonary arterial catheter and an ileal tonometer. Four groups of sheep were studied: nonseptic, septic, nonseptic treated with L-arginine, and septic treated with L-arginine. Sepsis was induced by the intravenous administration of Escherichia coli (1.5x10(8) colony-forming units/kg for 30 mins). L-arginine was administered as an intravenous bolus (200 mg/kg for 10 mins) before the septic challenge followed by 200 mg/kg/hr for 300 mins.

MEASUREMENTS AND MAIN RESULTS

Sepsis induced a state of acidosis, hyperlactatemia, hypoxemia, and gastric intramucosal acidosis. During the first 30 mins after the septic challenge, there was a decrease in cardiac index and blood pressure, and an increase in systemic vascular resistance. Thereafter, blood pressure returned to baseline values, and systemic vascular resistance fell. Treatment with L-arginine in nonseptic sheep did not induce any biochemical or hemodynamic effect. In septic sheep, treatment with L-arginine was associated with a greater increase in systemic vascular resistance during the first 30 mins, and a more marked decrease in blood pressure and systemic vascular resistance after 180 mins.

CONCLUSIONS

Exogenous administration of L-arginine does not induce hemodynamic effects in normal animals, exacerbates the acute vasoconstriction associated with the intravenous infusion of E. coli and potentiates the sepsis-induced vasodilation. Our results suggest that a) nitric oxide production is not constitutively modulated by exogenous L-arginine, b) L-arginine probably enhances the sepsis-induced sympathetic discharge, and c) L-arginine becomes rate-limiting for the formation of nitric oxide at approximately 3 hrs after the initiation of the septic challenge.

Lung matrix incorporation of plasma fibronectin reduces vascular permeability in postsurgical bacteremia

Plasma fibronectin (pFN) can incorporate into the lung extracellular matrix (ECM) as well as enhance hepatic cell phagocytic removal of bloodborne microparticulate debris that can contribute to lung vascular injury. Treatment of human pFN (hFN) with N-ethylmaleimide (NEM) blocks its ECM incorporation but not its ability to augment phagocytosis. Using hFN purified from fresh human plasma cryoprecipitate, we compared the effect of NEM-treated hFN versus normal hFN on lung transvascular protein clearance (TVPC) in postoperative bacteremic sheep to determine whether the ability of hFN to attenuate the increase in lung endothelial permeability required its ECM incorporation. Sheep with lung lymph fistulas were infused with a sublethal dose of Pseudomonas aeruginosa (5 x 10(8)) 48 h after surgery. In the first study, sheep received either FN-rich human cryoprecipitate, FN-deficient cryoprecipitate, FN purified from cryoprecipitate (hFN), FN-deficient cryoprecipitate reconstituted with purified hFN, or the sterile saline diluent. In the second study, sheep received either 200 mg of purified hFN (group I), 200 mg of NEM-treated hFN (group II), or the saline diluent (group III). In the first study, the increase in TVPC after bacterial challenge was attenuated by FN-rich cryoprecipitate, hFN, or reconstituted FN-deficient cryoprecipitate (P < 0.05) but not by saline and FN-deficient cryoprecipitate. In the second study, TVPC increased by 2 h (P < 0.05) and peaked over 4-8 h (P < 0.05) at 380-420% above baseline in postoperative bacteremic sheep given the diluent (group III). In contrast, intravenous infusion of hFN, but not of NEM-treated hFN, significantly (P < 0.05) attenuated this increase of lung protein clearance. Thus the ability for the intravenously infused purified pFN to attenuate the increase in lung endothelial protein permeability in sheep during postsurgical bacteremia appears to require its ECM incorporation into the interstitial ECM of the lung.

Risk factors for melioidosis and bacteremic melioidosis

A case-control study was conducted in four hospitals in northeastern Thailand to identify risk factors for melioidosis and bacteremic melioidosis. Cases were patients with culture-proven melioidosis, and there were two types of controls (those with infections, i.e., with community-acquired septicemia caused by other bacteria, and those without infection, i.e., randomly selected patients admitted with noninfectious diseases to the same hospitals). Demographic data, clinical presentations, and suspected risk factors were analyzed. Diabetes mellitus, preexisting renal diseases, thalassemia, and occupational exposure, classified by the soil and water risk assessment, were confirmed to be significant risk factors for melioidosis and bacteremic melioidosis. Only diabetes mellitus was a significant factor associated with bacteremic melioidosis, as compared with nonbacteremia. A significant interaction was found between diabetes mellitus and occupational exposure. Thus, diabetic rice farmers would be the most appropriate population group for targeted control measures such as vaccination in the future.

Prediction of microbial infection and mortality in medical patients with fever: plasma procalcitonin, neutrophilic elastase-alpha1-antitrypsin, and lactoferrin compared with clinical variables

Fever suggests the likelihood of severe microbial infection. Abnormal temperature, tachycardia, tachypnea, and abnormal white blood cell counts define the systemic inflammatory response syndrome (SIRS). In 300 hospitalized medical patients with fever, we determined clinical variables and procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels in plasma. Of the patients, 71% had clinical infection (by clinical judgment) and 44% had microbial infection (by microbiological testing). SIRS occurred in 95%, and the 28-day mortality rate was 9%. The sensitivity for predicting microbial infection, bacteremia, and mortality was less but the specificity was greater for supranormal procalcitonin, elastase-alpha1-antitrypsin, and lactoferrin levels than for SIRS. The area under the receiver operating characteristic curve (AUC) for microbial infection was higher for procalcitonin and elastase-alpha1-antitrypsin levels than for clinical variables and lactoferrin level. The AUC for bacteremia was also higher for inflammatory factors (>0.70; P < .001) than for clinical variables. The AUC for mortality (P < .05) was 0.79 for the respiratory rate, 0.69 for elastase-alpha1-antitrypsin level, 0.65 for heart rate, 0.61 for procalcitonin level, and 0.60 for white blood cell count. In febrile medical patients, plasma procalcitonin and elastase-alpha1-antitrypsin levels may predict microbial infection and bacteremia better than (and mortality as well as) do clinical symptoms.

Intestinal permeability in liver cirrhosis: relationship with severe septic complications

OBJECTIVES

Patients with liver cirrhosis are at high risk of severe septic complications such as spontaneous bacterial peritonitis (SBP) and bacteraemia. The aims of this study were to assess intestinal permeability in patients with liver cirrhosis and to search for a relationship between an impaired intestinal permeability and the occurrence of severe septic complications.

METHODS

Intestinal permeability was assessed in a group of 80 cirrhotic patients (Child A, n = 13; Child B, n = 26; Child C, n = 41) and 28 healthy control subjects. A severe septic complication (bacteraemia and/or SBP) occurred in 16 patients, within 10 days before (n = 8 cases) or after (n = 8 cases) the test was performed. Lactulose (LAC) 10 g was given orally together with mannitol (MAN) 5 g, and urinary excretion rates were determined.

RESULTS

Urinary mannitol excretion (MAN%) was lower while the LAC/MAN ratio was higher in patients than in control subjects (P < 0.001); these abnormalities were more marked in Child C patients (Child C patients vs control subjects: MAN%, 8.20 +/- 0.79 vs 14.59 +/- 0.58, P < 0.001; LAC/MAN, 0.066 +/- 0.026 vs 0.017 +/- 0.001, P < 0.02). When compared with non-infected patients, septic patients had a lower MAN% and an increased LAC/ MAN ratio (5.45 +/- 1.12 vs 9.83 +/- 0.87, P < 0.02; 0.130 +/- 0.063 vs 0.029 +/- 0.005, P < 0.02).

CONCLUSION

Although the main mechanism involved in the decrease in MAN% is likely a reduction in area of the intestinal absorptive surface, these results argue in favour of an increased intestinal permeability in liver cirrhosis, especially in patients with severe infectious complications. The impairment of intestinal function barrier may contribute to severe septic complications in these patients.

Pseudomonas aeruginosa bacteremia in patients infected with human immunodeficiency virus type 1

A prospective analysis of 43 episodes of Pseudomonas aeruginosa bacteremia in HIV-1-infected subjects was performed and the results compared with the incidence and outcome of Pseudomonas aeruginosa bacteremia in other high-risk patients, such as transplant recipients, leukemia patients, or patients hospitalized in the intensive care unit. The incidence of bacteremia/fungemia as a whole and of gram-negative and Pseudomonas aeruginosa bacteremia in particular was greater in HIV-1-infected subjects than in the unselected general population admitted. In contrast, the incidence of Pseudomonas aeruginosa bacteremia in HIV-1-infected patients did not differ from that in patients with other high-risk conditions. In patients with HIV-1 infection, independent risk factors for presenting Pseudomonas aeruginosa bacteremia were nosocomial origin (OR, 2.7; 95% CI, 1.3-5.7), neutropenia (OR, 2.7; 95% CI, 1.07-6.8), previous treatment with cephalosporins (OR, 3.6; 95% CI, 1.1-11.6), and a CD4+ cell count lower than 50 cells/mm3 (OR, 3.1; 95% CI, 1.7-8.6). Primary bacteremia and pneumonia were the most common forms of presentation. Fourteen (33%) patients died as a consequence of the bacteremia. The presence of severe sepsis (OR, 17.5; 95% CI, 3.2-68) and the institution of inappropriate definitive antibiotic therapy (OR, 2.7; 95% CI, 1.1-13) were independently associated with a poor outcome. One year after the development of bacteremia, only eight (19%) patients remained alive.

New criteria for selecting the proper antimicrobial chemotherapy for severe sepsis and septic shock

The mortality rate resulting from severe bacterial sepsis, particularly that associated with shock, still approaches 50% in spite of appropriate antimicrobial therapy and optimum supportive care. Bacterial endotoxins that are part of the cell wall are one of the cofactors in the pathogenesis of sepsis and septic shock and are often induced by antimicrobial chemotherapy even if it is administered rationally. Not all antimicrobial agents are equally capable of inducing septic shock; this is dependant on their mechanism of action rather than on the causative pathogen species. The quantity of endotoxin released depends on the drug dose and whether filaments or spheroplast formation predominates. Some antibiotics such as carbapenems, ceftriaxone, cefepime, glycopeptides, aminoglycosides and quinolones do not have the propensity to provoke septic shock because their rapid bactericidal activity induces mainly spheroplast or fragile spheroplast-like bacterial forms.

Decreased alpha-adrenergic response in the intestinal microcirculation after "two-hit" hemorrhage/resuscitation and bacteremia

BACKGROUND

The two-hit theory of multiple organ dysfunction syndrome proposes that an initial insult primes the host for an altered response to subsequent stimuli. We have previously documented enhanced dilator tone in the small intestine after a two-hit insult; however, the effects on vasoconstrictor function are unknown. We postulated that prior hemorrhage and resuscitation followed by bacteremia would alter microvascular responsiveness to alpha-adrenergic stimulation.

METHODS

Male Sprague-Dawley rats underwent fixed-volume hemorrhage with resuscitation (H/R) or sham procedure (Sham). At 24 or 72 h, in vivo videomicroscopy of the small intestine was performed (inflow A1 and premucosal A3 arterioles). Constrictor function was assessed by topical application of norepinephrine (NE; 10(-8)-10(-6) M) before and 1 h after intravenous Escherichia coli or saline.

RESULTS

Sham, 24 or 72 h H/R, and E. coli alone produced no significant changes in A1 or A3 response to NE. Sequential H/R + E. coli resulted in decreased constrictor response in both A1 (72 h H/R + E. coli-38% from baseline vs Sham - 54%, P < 0.05) and A3 arterioles (-8% vs -51%, P < 0.05) at high doses of NE (10(-6) M).

CONCLUSIONS

Prior H/R primes the intestinal microvasculature for an altered response during a subsequent stress and these effects persist for up to 72 h following H/R. Sequential insults in this two-hit model caused marked hyporesponsiveness to NE. These alterations in control of microvascular tone might contribute to the hemodynamic compromise of sepsis, impair mucosal blood flow, and contribute to the development of MODS.

Interleukin-1 mediates hemodynamic dysfunction and release of eicosanoids and tumor necrosis factor during graded bacteremia

The pathophysiologic events of sepsis mediated by interleukin-1 (IL-1) remain ill-defined. The purpose of this study was to identify the circulatory derangements of which IL-1 was a necessary mediator and evaluate its interactions with tumor necrosis factor (TNF) and the eicosanoids during graded bacteremia. Eleven adult female swine were anesthetized, mechanically ventilated, and monitored with pulmonary artery catheters and arterial lines; they received intravenously either saline vehicle (septic control, n = 6) or human recombinant IL-1 receptor antagonist (IL-1ra, n = 5). The animals were then infused with Aeromonas hydrophila (10(9)/mL) for 4 h at rates gradually increased from .2 mL/kg/h to 4 mL/kg/h over 3 h, then sacrificed after 4 h. Mean arterial pressure (MAP), left ventricular stroke work index (LVSWI), and systemic vascular resistance index (SVRI) were recorded at baseline and hourly thereafter, and plasma 6-keto-PGF1alpha (6-KETO), tumor necrosis factor-alpha (TNF) and leukotrienes B4(LTB4) and C4D4E4 (LTCDE), pg/mL, were measured by ELISA. MAP, LVSWI, arterial P(O2) all decreased in the septic control group to levels significantly below those of the IL-1 antagonist animals. Circulating 6-KETO, LTCDE, and TNF increased significantly in all septic animals. Plasma LTB, and TNF were reduced by IL-1 blockade, compared with septic controls. TxB2 was not affected by IL-1 inhibition. There were no intergroup differences in platelet aggregation, but the in vitro aggregation response decreased from baseline in septic controls to 54+/-27% (p < .05). IL-1 is necessary to the development of systemic hypotension impaired LVSWI, and increased intravascular platelet aggregation during graded bacteremia. Conversely, IL-1 helps to maintain stroke volume and low SVRI in graded bacteremia, possibly through increased prostacyclin release. It may contribute to impaired pulmonary gas exchange and increased tissue oxygen demands. TNF release is stimulated in the presence of unopposed IL-1 and may be synergistic with it in the adverse hemodynamic effects of endogenous IL-1. IL-1 is required for increased leukotriene and prostacyclin levels in this model, but it is not involved in thromboxane release. Whether the lack of survival benefit from IL-1ra in human sepsis is due to these mixed cardiopulmonary and mediator effects, to species differences, or to timing of IL-1ra administration is not clear from the data.

Experimental infection by Vibrio anguillarum in mice and guinea pigs

The fish pathogen Vibrio anguillarum causes a lethal infection in farmed fish characterized by hemorrhagic septicemia. There are no reports of experimental laboratory infections in warm-blooded animals. We investigated the effects of an intraperitoneal infection with different doses of a V. anguillarum suspension in mice and guinea pigs. The infection caused a 95-100% of mortality in 24-48 h. Hemorrhagic septicemia was observed at necropsy and confirmed by histological and hematological examination. Immunohistochemically positive bacterial clumps were detected exclusively in vessel lumen in all examined organs, including brain, and V. anguillarum was reisolated in pure culture from all organs, particularly from the kidney. Blood analysis showed erythropenia and leukopenia with granulocytosis in mice, platelet reduction and leukopenia with lymphocytosis in guinea pigs.

[Selection of virulent mutants of Streptococcus pneumoniae. Utilization of a murine model of septicemia]

Genetic construction of virulence deficient mutant is a strategy to analyse virulence genes of Streptococcus pneumoniae and was used to virulence factors as capsule, pneumolysin, autolysin and PspA. We perform a model allowing the in vivo positive selection of virulent S. pneumoniae mutants. Mice which are the most susceptible animals to pneumococcal infection, offer the best model for screening virulent S. pneumoniae. Indeed, after intraperitoneal injection of bacterial mix which was composed to a lot of avirulent bacteria (6 log10 CFU per mouse) (V1015 strain, DL50 = 7.05) and few virulent pneumococci (1 to 2 log10 CFU per mouse) (P4241 strain, DL50 < 1), mice cleared all avirulent bacteria but not virulent pneumococci. Thus, mice dead in 3 to 4 days with septicaemia and positive hemoculture contained only virulent strain. This model was validated by in vivo selection of a virulent mutant (V1042, DL50 = 4.1) which was obtained after transformation of avirulent strain V1015 with the genomic fragment of virulent strain P4241. Our model of screening was the only one allowing detection of virulent S. pneumoniae mutants. This new genetic strategy which consisted in gene addition and used mouse as selection agent, could be used to discover new virulence genes required to in vivo bacterial development.

Microvascular perfusion deficits are not a prerequisite for mucosal injury in septic rats

Our major objective was to investigate whether injury to the mucosa of the small intestine occurred in a normotensive model of sepsis and whether such injury was associated with microvascular perfusion deficits. Using fluorescence intravital microscopy, we show direct evidence of cell injury within the mucosa (pneumonia 12.4 +/- 2.6 cells/field, sham 2.2 +/- 0.7 cells/field), whereas use of 51Cr-labeled EDTA showed evidence of increased mucosal permeability (pneumonia 1.90 +/- 0.67 ml. min-1. 100 g-1; sham 0.24 +/- 0.04 ml. min-1. 100 g-1), 48 h following induction of pneumonia. Despite such injury the capillary density in the ileal mucosa and submucosa of pneumonic rats (1,027 +/- 77 and 1,717 +/- 86 mm2) was not significantly different compared with sham (998 +/- 63 and 1,812 +/- 101 mm2). However, a modest albeit significant decrease in capillary perfusion was measured in the muscularis layer of pneumonia (11.0 +/- 1.3 mm) compared with sham (13.9 +/- 0.63 mm) and appeared to be associated with leukocyte entrapment. Pretreatment using low doses of endotoxin to induce endotoxin tolerance not only increased muscularis capillary density but reduced the number of leukocytes trapped within the microvasculature, decreased myeloperoxidase activity within the ileum in pneumonic rats, and prevented mucosal injury. In conclusion, we have shown that pneumonia results in remote injury to the mucosa of the ileum and that such injury was not associated with concurrent mucosal perfusion deficits.

TNF-binding protein ameliorates inhibition of skeletal muscle protein synthesis during sepsis

We examined the effects of TNF-binding protein (TNFBP) on regulatory mechanisms of muscle protein synthesis during sepsis in four groups of rats: Control; Control+TNFBP; Septic; and Septic+TNFBP. Saline (1. 0 ml) or TNFBP (1 mg/kg, 1.0 ml) was injected daily starting 4 h before the induction of sepsis. The effect of TNFBP on gastrocnemius weight, protein content, and the rate of protein synthesis was examined 5 days later. Sepsis reduced the rate of protein synthesis by 35% relative to controls by depressing translational efficiency. Decreases in protein synthesis were accompanied by similar reductions in protein content and muscle weight. Treatment of septic animals with TNFBP for 5 days prevented the sepsis-induced inhibition of protein synthesis and restored translational efficiency to control values. TNFBP treatment of Control rats for 5 days was without effect on muscle protein content or protein synthesis. We also assessed potential mechanisms regulating translational efficiency. The phosphorylation state of p70(S6) kinase was not altered by sepsis. Sepsis reduced the gastrocnemius content of eukaryotic initiation factor 2Bepsilon (eIF2Bepsilon), but not eIF2alpha. The decrease in eIF2Bepsilon content was prevented by treatment of septic rats with TNFBP. TNFBP ameliorates the sepsis-induced changes in protein metabolism in gastrocnemius, indicating a role for TNF in the septic process. The data suggest that TNF may impair muscle protein synthesis by reducing expression of specific initiation factors during sepsis.

Reduced bacterial dissemination and liver injury in CD14-deficient mice following a chronic abscess-forming peritonitis induced by Bacteroides fragilis

The CD14 myelomonocytic differentiation antigen plays a major role in acute Gram-negative infections with Escherichia coli; however, its role in chronic infections has not yet been analyzed. To address this question, we studied the role of CD14 in a chronic abscess-forming peritonitis, induced by Bacteroides fragilis. B. fragilis (3x10(8) CFU/ml) were resuspended in a liquid nutrient agar and injected into the peritoneal cavity of CD14-deficient (CD 14-/-) and normal C57BL/6J (CD 14+/+) mice, respectively. After 3 days there was a severe phlegmonous intra-abdominal inflammation in both groups. After 7 days an abscess-forming peritonitis developed and by 14 days the infectious foci were compartimentalized. These observations were indistinguishable between CD14-/- and CD14+/+ mice. Although no differences were seen in abscess formation, CD14-/- mice were able to clear B. fragilis more efficiently from the blood than CD14+/+ mice. After 3, 7, and 14 days blood cultures were B. fragilis positive in 11% (1/9), 20% (2/10), and 0% (0/9) in CD14-/-compared with 90% (9/10), 78% (7/9), and 20% (2/10) in CD14+/+ mice, respectively (P<0.05). Furthermore, although the infection resulted in hepatocellular necrosis and severe hepatitis in both groups, at day 14 the liver cell damage was more severe in CD14+/+ than in CD14-/- mice (P<0.05). These results show that the chronic abscess formation induced by B. fragilis capsular polysaccharides is CD14 independent; however, bacterial clearance and/or dissemination and liver cell damage are at least partially influenced by CD14-dependent mechanisms.

A murine model of renal abscess formation

We developed a murine model of kidney abscess by direct renal injection of either Escherichia coli (1 x 10(6) to 7 x 10(6) organisms) or sterile medium. Bacterial infection produced renal abscesses, bacteremia, and late-onset leukocytosis in all animals. Controls were unaffected. This model may be useful for the study of various sequelae of kidney infection.

Altered vasoconstrictor and dilator responses after a "two-hit" model of sequential hemorrhage and bacteremia

BACKGROUND

The "two-hit" theory of multiple organ dysfunction (MOD) proposes that an initial insult, such as hemorrhage (HEM), primes the host for an abnormal response to a second stress such as infection. The immunologic/inflammatory component of this theory has been well examined; however, the effects on vascular responsiveness are poorly understood. We hypothesized that HEM primes the vasculature for an altered response to a second pathophysiologic stress.

METHODS

Male Sprague-Dawley rats underwent a fixed-volume HEM with resuscitation (H/R) or sham procedure (Sham). At 48 h, animals were given iv E. coli or saline and followed for 1 h. Thoracic aortic rings were then placed in organ baths containing Krebs buffer aerated with 95% O2, 5% CO2. Cumulative dose-response curves to phenylephrine (PHE) and acetylcholine (ACH) were obtained. Maximum force of contraction (Fmax) was measured and pD2 values (receptor sensitivity) were derived.

RESULTS

H/R alone resulted in heightened constrictor tone and blunted dilator tone. E. coli reduced Fmax in response to PHE by 50% in Sham vs 76% in H/R. Receptor sensitivity (pD2) to PHE was reduced to a greater degree in H/R (3-fold vs 2-fold). These animals also had a more pronounced enhancement of ACH receptor sensitivity (7-fold vs 2-fold).

CONCLUSIONS

Hemorrhage primes the vasculature for an altered response to a subsequent stress. When infection is added as a "second hit," responsiveness to adrenergic agents is diminished and dilator tone is increased. These data may explain the cardiovascular derangements seen clinically in patients who develop MODS after major hemorrhage followed sequentially by infection.

Selective inhibition of inducible nitric oxide synthase: effects on hemodynamics and regional blood flow in healthy and septic sheep

OBJECTIVES

To investigate the effects of S-ethylisothiourea (S-EITU) on hemodynamics, oxygen transport, and regional blood flow in healthy and septic sheep.

DESIGN

Prospective, randomized, controlled experimental study with repeated measures.

SETTING

Investigational intensive care unit at a university medical center.

SUBJECTS

Eleven healthy, female adult sheep of the Merino breed, divided into a control group (n = 5) and into a group treated with S-EITU (n = 6).

INTERVENTIONS

All sheep were chronically instrumented. After a 5-day recovery period, they were randomly assigned to either control or S-EITU groups. While control sheep received only saline, S-EITU was administered in increasing doses of 1, 3, and 9 mg/kg/hr over 1 hr each (nonseptic phase). After 2 days of recovery, a continuous infusion of live Pseudomonas aeruginosa (2.5 x 106 colony-forming units/min) was started in all sheep and maintained for the remainder of the experiment. After 24 hrs of sepsis, the sheep again received their assigned treatment (septic phase). In both the nonseptic and septic phases, the sheep received colored microspheres through a left atrial catheter to allow analysis of regional blood flows. All animals were autopsied at the end of the experiments, and organ probes were removed for blood flow analyses.

MEASUREMENTS AND MAIN RESULTS

The administration of S-EITU caused a dose-dependent vasoconstriction in the nonseptic phase. After 24 hrs of Pseudomonas infusion, all sheep developed a hyperdynamic circulatory state, with increased cardiac indices and reduced arterial pressures and systemic vascular resistances. Oxygen extraction decreased significantly, preventing an increase in oxygen consumption, despite an increased oxygen delivery. The hyperdynamic circulation was dose dependently reversed by S-EITU, causing an increase in arterial pressure by peripheral vasoconstriction. Sheep in the control group showed a continuation of the hyperdynamic circulation. The effects of S-EITU on hemodynamics and regional blood flows were comparable under septic and nonseptic conditions.

CONCLUSIONS

With the inducible form of nitric oxide synthase expressed under septic, but not under nonseptic conditions, S-EITU was expected to have vasoconstrictive properties only in the septic phase. It produced a comparable vasoconstriction during the nonseptic phase of the experiment. Thus, either S-EITU does not selectively block the inducible nitric oxide synthase in sheep, or other vasodilators besides nitric oxide play an important role in septic vasodilation.

Facial cellulitis and Pseudomonas luteola bacteremia in an otherwise healthy patient

Pseudomonas luteola is an aerobic, Gram negative rod, formerly classified as CDC group Ve-1 and Chryseomonas luteola. It is an uncommon clinical isolate. A previously healthy 59-year-old homosexual man with facial cellulitis and Pseudomonas luteola bacteremia is reported. Previously reported cases of P. luteola bacteremia have occurred in association with pancreatic abscess, prosthetic valve endocarditis, cardiac surgery, granulomatous hepatitis, peritonitis, and indwelling vascular catheters. This case suggests that the spectrum of disease caused by this bacteria may continue to expand.

E. Coli bacteremia-induced changes in the skeletal muscle microcirculation vary with anesthetics

AIM

To test if anesthetic procedures change the hemodynamic pattern in animals with experimental septic shock.

METHODS

The effect of two anesthetics on systemic hemodynamic and skeletal muscle microcirculatory responses in high cardiac output live E. coli bacteremia was studied in rats and compared to the effect of two other anesthetic procedures in previously published studies.

RESULTS

Baseline blood pressures and cardiac outputs were similar in rats with decerebrate, ketamine/xylazine, pentobarbital or urethane/chloralose anesthesia. There was a relative baseline tachycardia in decerebrate rats. Ketamine/xylazine anesthetized rats had reduced blood pressure, cardiac output, and heart rate. In decerebrate, pentobarbital, and urethane/chloralose anesthesia, cardiac output increased initially during bacteremia but did not remain elevated in pentobarbital anesthesia. Blood pressure and heart rate remained constant in pentobarbital, decerebrate, and urethane/chloralose anesth esia. During bacteremia, cardiac output, blood pressure, and vascular resistance did not change with ketamine/xylazine, but the heart rate increased. Baseline diameters of cremaster muscle large (A1) arterioles were higher in decerebrate anesthesia. A1 arterioles constricted during high cardiac output bacteremia in decerebrate rats, and pentobarbital or urethane/chloralose-anesthetized rats. A4 arterioles in bacteremia dilated in decerebrate and pentobarbital anesthesia, but did not change under urethane/chloralose and ketamine/xylazine anesthesia.

CONCLUSION

Anesthetics influence baseline systemic variables and the response of systemic hemodynamics of rats to E. coli bacteremia. During bacteremia, anesthetics primarily affect the reactivity of skeletal muscle small arterioles. Ketamine/xylazine anesthesia has the most pronounced effect on systemic and microcirculatory variables and seems to be an inappropriate choice in sepsis experiments in rats.

Streptococcus sanguis-induced platelet clotting in rabbits and hemodynamic and cardiopulmonary consequences

By mimicking hemostatic structural domains of collagen, Streptococcus sanguis (aggregation-positive phenotype; Agg+) induces platelets to aggregate in vitro. To test the hypothesis that aggregation occurs in vivo, S. sanguis (Agg+ or Agg- suspension) was infused intravenously into rabbits. The extent of hemodynamic and cardiopulmonary changes and the fate of circulating platelets were Agg+ strain dose dependent. Within 45 to 50 s of the start of infusion, 40 x 10(8) CFU of the Agg+ strain caused increased blood pressure. Thirty seconds after infusion, other changes occurred. Intermittent electrocardiographic abnormalities (13 of 15 rabbits), ST-segment depression (10 of 15 rabbits), and preventricular contractions (7 of 15 rabbits) manifested at 3 to 7 min, with frequencies dose dependent. Respiratory rate and cardiac contractility increased during this phase. Blood catecholamine concentration, thrombocytopenia, accumulation of 111Indium-labeled platelets in the lungs, and ventricular axis deviation also showed dose dependency. Rabbits were unaffected by inoculation of an Agg- strain. Therefore, Agg+ S. sanguis induced platelet aggregation in vitro. Platelet clots caused hemodynamic changes, acute pulmonary hypertension, and cardiac abnormalities, including ischemia.

Dopexamine attenuates endotoxin-induced microcirculatory changes in rat mesentery: role of beta2 adrenoceptors

OBJECTIVE

To investigate the influence of dopexamine on endotoxin-induced leukocyte adherence and on vascular permeability in postcapillary venules of rat mesentery.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Twenty-seven male Wistar rats, weighing 250 to 350 g.

INTERVENTIONS

Rats received one of three treatments: a) infusion of Escherichia coli endotoxin without dopexamine pretreatment; b) infusion of endotoxin with dopexamine pretreatment; or c) infusion of endotoxin after pretreatment with dopexamine and ICI 118,551, a selective beta2-receptor antagonist.

MEASUREMENTS AND MAIN RESULTS

Leukocyte adherence, red blood cell velocity, and vessel diameters in postcapillary venules were evaluated using in vivo videomicroscopy. Vascular permeability was determined by measuring the extravasation of fluorescence-labeled albumin. Venular wall shear rate was calculated from red cell velocity and vessel diameter. Dopexamine attenuated both the increase in leukocyte adherence and vascular permeability during endotoxemia. The attenuating effect on leukocyte adherence could not be antagonized by the beta2-adrenoceptor antagonist. However, the attenuating effect on vascular permeability was antagonized by ICI 118,551. Dopexamine prevented a decrease in venular wall shear rate during endotoxemia. This effect was not influenced by ICI 118,551.

CONCLUSIONS

Dopexamine attenuates endotoxin-induced microcirculatory disturbances in rat mesentery. The attenuating effect on vascular permeability is a beta2-adrenoceptor-mediated process, whereas the beta2-adrenoceptor actions of dopexamine play no significant role in attenuating leukocyte adherence.

Acute septicaemic pasteurellosis in Vietnamese pigs

Sixteen isolates of Pasteurella multocida were cultured from cases diagnosed as acute septicaemic pasteurellosis in Vietnamese pigs. The HSB-PCR assay provided rapid presumptive determination of 10 isolates of P. multocida identified as haemorrhagic septicaemia (HS) causing type B cultures (B:2, B:5, B:2,5). Serological designation using the Carter and Heddleston typing systems confirmed these findings, and identified the six HSB-PCR negative cultures as either A:1, A:3 or D:3,4. Biochemical fermentation and REP-PCR revealed phenotypic and genotypic identity between P. multocida type A:1 isolated from Vietnamese pigs and poultry. Marked homogeneity was also demonstrated among HSB-PCR positive swine isolates, which were shown to possess genotypic identity with P. multocida type B:2 from buffaloes diagnosed with HS.

Benefits and risks of antipyretic therapy

Physicians have used various forms of antipyretic therapy since antiquity to lower the temperature of febrile patients. Nevertheless, it has yet to be determined whether the benefits of antipyretic therapy outweigh its risks. It is not known, for example, if core temperatures encountered during the febrile state ever reach levels that are intrinsically noxious (and therefore merit antipyretic intervention) or when, if ever, fever's metabolic costs exceed its physiologic benefits, or if the benefits of symptomatic relief afforded by antipyretic drugs consistently exceed their toxicologic cost. Whereas preliminary experimental and clinical observations suggest that antipyretic therapy has the potential to increase the duration and/or severity of certain infections, such data are as yet too fragmentary to draw firm conclusions regarding their validity. Finally, although clinicians have long suspected that bacteremia and other severe infections might induce fevers that are less responsive to antipyretic therapy than are those associated with self-limited infections, this concept has not held up under scientific scrutiny. Thus, despite over 2.5 millennia of clinical experience, important questions regarding the risks and benefits of antipyretic therapy remain to be answered.

N(G)-monomethyl-L-arginine improves survival in a pig model of abdominal sepsis

OBJECTIVE

To test the effect of a continuous infusion of the nitric oxide synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on survival rate and hemodynamics in a pig model of endogenous peritoneal live bacterial sepsis.

DESIGN

Prospective, randomized trial.

SETTING

Laboratory at a university medical center.

SUBJECTS

Thirty-five pigs with an average weight of 26 kg (range 21 to 33).

INTERVENTIONS

After surgical preparation, animals (control, n=6) given anesthesia and fluids were observed for 9 hrs. Fifteen experimental animals received 0.5 g of cecal content/kg of body weight intraperitoneally after surgery. Nine of these animals received standard anesthesia and fluids and were observed for 9 hrs or until death. Six animals received a continuous infusion of L-NMMA (10 mg/kg/hr) 3 hrs after sepsis induction. Starting 3 hrs after surgery, five nonrandomized animals were given anesthesia and fluids and received a 6-hr continuous infusion of L-NMMA (10 mg/kg/hr). An additional nine animals were anesthetized and blood samples were taken to determine plasma nitrate concentrations in nonoperated pigs.

MEASUREMENTS AND MAIN RESULTS

L-NMMA treatment increased 9-hr survival in septic animals from 11% to 83% (p < .001), prevented a further decrease in mean arterial pressure and restored mean arterial pressure to control levels (p < .00002 vs. nontreated septic animals). Mean pulmonary arterial pressure increased slightly during L-NMMA infusion (p < .0003). Coronary blood flow was preserved during L-NMMA treatment. Cardiac index and urine production reached and maintained control levels during L-NMMA treatment of septic animals. Mean central venous pH did not deteriorate during L-NMMA treatment. Animals treated with L-NMMA had plasma nitrate concentrations similar to nonseptic control animals. The results from the nonseptic control group receiving L-NMMA suggest that a substantial part of the effect of L-NMMA in this model of septic shock may be due to inhibition of the constitutive nitric oxide production.

CONCLUSIONS

In this porcine model of peritoneal sepsis, infusion of L-NMMA increased survival rate and maintained mean arterial pressure without worsening tissue oxygenation. Coronary blood flow, cardiac index, systemic vascular resistance, and urine production were well maintained during L-NMMA treatment.

Bioelectrical impedance analysis predicts outcome in patients with suspected bacteremia

Fluid shifts from intracellular to extracellular water (ICW to ECW) are a feature of sepsis, caused by increased vascular permeability and cell catabolism. Changes in ECW and total body water (TBW) were assessed in a prospective observational study of patients with bacteremia by a bedside technique, and its prognostic impact determined. In 78 hospital patients with fever, the resistance ratio (Rinf/RO) and estimated ECW/TBW ratio from multifrequency bioelectrical impedance analysis, and f1p4m albumin concentration were measured. Rinf/RO and ECW/TBW ratios decreased from day 0 to 2 in patients with significant bacteremia (n = 31), but not in patients with doubtful or negative blood cultures (n = 22 and 25). Increased Rinf/RO at baseline, and further increase of ECW/TBW from day 0 to 2, were associated with lower rate of recovery after 1 week and with higher mortality. Baseline Rinf/RO above the median (0.75) had positive and negative predictive values of 0.31 and 0.95 for death. This prognostic effect was independent of underlying disease and blood culture result in a multivariate model. Hypoalbuminemia at baseline was predictive of outcome, but changes in albumin from day 0 to 2 were unrelated to blood culture results or outcome. In patients with bacteremia, fluid shifts from intracellular to extracellular water occur early, are rapidly reversible by antibiotic treatment but are associated with adverse prognosis. Bioelectrical impedance deserves further study as a tool for bedside monitoring of patients with bacteremia.

Clinical significance of bacteremia involving the "Streptococcus milleri" group: 51 cases and review

Fifty-one cases of bacteremia due to the "Streptococcus milleri" group were analyzed. Among these were 40 patients with underlying diseases, and associated local infections were present in 27 patients. The most frequent sites of infection were the thoracic cavity and the digestive and hepatobiliary tracts. A probable portal of entry related to mucosal-barrier trauma was identified for an additional 16 patients. The origin of bacteremia was unknown for the remaining eight patients. Abscess formation was evident for only six patients, and there were no cases of endocarditis. Multiple positive blood cultures and polymicrobial bacteremia were associated significantly with the presence of local sites of infection. The most common causative species were Streptococcus anginosus and Streptococcus constellatus. Two patients died of bacteremia.

Pulmonary sequestration of polymorphonuclear leukocytes released from bone marrow in bacteremic infection

We examined the bone marrow response and the sequestration of polymorphonuclear leukocytes (PMNs) in lung using a bacteremic infection model in rabbits. PMNs were labeled with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) in the bone marrow, and the bone marrow release and the sequestration of BrdU-labeled PMNs were measured using immunohistochemistry. A focal subcutaneous infection (S) was induced, and the bacteremia (B) was produced 4 h later with Streptococcus pneumoniae (S+B). This S+B group was compared with other groups with only subcutaneous infection or only bacteremia. The S+B group developed a profound leukopenia after the bacteremia that was associated with an increase in circulating BrdU-labeled PMNs. Morphometric studies showed more PMN sequestration in the lung of the S+B group compared with the others (P < 0.05). Compared with unlabeled PMNs, BrdU-labeled PMNs, which represent newly released PMNs, preferentially sequestered in lung (P < 0.05) and were slow to migrate into the infected tissues (P < 0.05). We conclude that bacteremic infection is associated with an accelerated release of PMNs from the bone marrow and that these newly released PMNs preferentially sequester in lung and are slow to migrate into infected tissues.

A new causal model of dental diseases associated with endocarditis

Infective endocarditis (IE) is a serious disease that is associated with dental diseases and treatment. The objective of this study was to summarize the epidemiological information about IE and reevaluate previous causal models in light of this evidence. The world biomedical literature was searched from 1930 to 1996 for descriptive and analytic epidemiological studies of IE. Multiple searching strategies were performed on 9 databases, including MEDLINE, CATLINE, and WORLDCAT. Results show that: 1) the incidence of IE varies between 0.70 to 6.8 per 100,000 person-years: 2) the incidence of IE increases 20 fold with advancing age: 3) over 50% of all IE cases are not associated with either an obvious procedural or infectious event 3 months prior to developing symptoms; 4) about 8% of all IE cases are associated with periodontal or dental disease without a dental procedure: 5) the time from the diagnosis of heart valve deformities to the development of IE approaches 20 years: 6) the median time from identifiable procedures to the onset of IE symptoms is about 2 to 4 weeks: 7) the risk of IE after a dental procedure is probably in the range of 1 per 3,000 to 5,000 procedures: and 8) over 80% of all IE cases are acquired in the community, and the bacteria are part of the host's endogenous flora. The synthesis of these data demonstrates that IE is a disorder with the epidemiological picture of a chronic disease such as cancer, instead of an acute infectious disease, with a long latent period and possibly several definable intermediates or stages. A new causal model is proposed that includes early bacteremias that may "prime" the endothelial surface of the heart valves over many years, and a late bacteremia over days to weeks that allows adherence and colonization of the valve, resulting in the characteristic fulminant infection.

The role of coronary flow and adenosine in postischemic recovery of septic rat hearts

Sepsis depresses myocardial function but prevents subsequent ischemia-reperfusion injury. Elevated coronary flow (CF) and endogenous adenosine may be important factors in the complete recovery of postischemic myocardial function observed in septic rat hearts. The purpose of this study was to determine the effects of manipulating CF and of antagonizing adenosine receptors on the postischemic recovery of left ventricular developed pressure (LVDP) in septic and control rat hearts. The relationship between CF and LVDP in septic rat hearts before ischemia was depressed compared with control. However, this relationship was unaltered by ischemia in septic hearts, whereas in control hearts it was severely depressed. Preventing the elevation of CF during reperfusion did not significantly affect the recovery of LVDP in septic rat hearts. Adenosine antagonism by 8-phenyltheophylline (0.1 and 1 nM) prevented the elevated CF during reperfusion, and the higher dose significantly depressed postischemic function. We conclude that elevated CF did not contribute to the recovery of postischemic LVDP in septic rat hearts but that endogenous adenosine may provide protection from ischemia.

Microvascular changes explain the "two-hit" theory of multiple organ failure

OBJECTIVE

The objective was to determine intestinal microvascular endothelial cell control after sequential hemorrhage and bacteremia.

SUMMARY BACKGROUND DATA

Sepsis that follows severe hemorrhagic shock often results in multiple system organ failure (MSOF) and death. The sequential nature of this clinical scenario has led to the idea of a "two-hit" theory for the development of MSOF, the hallmark of which is peripheral vasodilation and acidosis. Acute bacteremia alone results in persistent intestinal vasoconstriction and mucosal hypoperfusion. Little experimental data exist to support the pathogenesis of vascular dysregulation during sequential physiologic insults. We postulate that hemorrhagic shock followed by bacteremia results in altered microvascular endothelial cell control of dilation and blood flow.

METHODS

Rats underwent volume hemorrhage and resuscitation. A sham group underwent the vascular cannulation without hemorrhage and resuscitation, and controls had no surgical manipulation. After 24 and 72 hours, the small intestine microcirculation was visualized by in vivo videomicroscopy. Mean arterial pressure, heart rate, arteriolar diameters, and A1 flow by Doppler velocimetry were measured. Endothelial-dependent dilator function was determined by the topical application of acetylcholine (ACh). After 1 hour of Escherichia coil bacteremia, ACh dose responses were again measured. Topical nitroprusside was then applied to assess direct smooth muscle dilation (endothelial-independent dilator function) in all groups. Vascular reactivity to ACh was compared among the groups.

RESULTS

Acute bacteremia, with or without prior hemorrhage, caused significant large-caliber A1 arteriolar constriction with a concomitant decrease in blood flow. This constriction was blunted at 24 hours after hemorrhage but was restored to control values by 72 hours. There was a reversal of the response to bacteremia in the premucosal A3 vessels, with a marked dilation both at 24 and 72 hours. The sequence of hemorrhage and E. coli resulted in a progressive enhanced reactivity to the endothelial-dependent stimulus of ACh in the A3 vessels at 24 and 72 hours. Reactivity to endothelial-independent smooth muscle relaxation and subsequent vessel dilation was similar for all groups.

CONCLUSIONS

These data indicate that there is altered endothelial control of the intestinal microvasculature after hemorrhage in favor of enhanced dilator mechanisms in premucosal vessels with enhanced constrictor forces in inflow vessels. This enhanced dilator sensitivity is most evident in small premucosal vessels. This experimental finding supports the premise that an initial pathophysiologic stress alters the subsequent microvascular blood flow responses to systemic inflammation. These changes in the intestinal microcirculation are in concert with the "two-hit" theory for MSOF.

[Sepsis in surgery: pathogenesis, new therapeutic approaches]

Sepsis and septic shock are phenomena with a characteristic clinical picture and etiologically related to injury. Chains of events from injury (e.g., infection) through activation of immunological system to multiple organ failure are responsible for sepsis. Neutralization of endotoxins, TNF, interleukins and so on, can improve the treatment of sepsis in the future.

The early management of meningococcal disease

Meningococcal disease is a fulminant infection with an overall mortality of 8%. Mortality is significantly increased with meningococcal septicaemia, particularly when there has been a delay in the diagnosis. The trend from 1985 to 1995 has been an increase in incidence of this disease, and the relative importance of meningococcal disease has also increased following a fall in the incidence of invasive Haemophilus influenzae disease with childhood immunisation. The management of such cases can be complex and time critical. Patients with meningococcal septicaemia often require aggressive resuscitation, including airway support, intravenous colloid, and parenteral antibiotics; hypoglycaemia is also commonly seen, and inotropes may be needed to support the circulation. We examine the treatment strategies in the early management of meningococcal disease and provide an algorithm for use by ambulance personnel, general practitioners, accident and emergency clinicians, and paediatricians. The objective of this algorithm is to ensure that an optimally resuscitated patient is delivered to the definitive care facility.

Effects of anti-C5a monoclonal antibodies on oxygen use in a porcine model of severe sepsis

METHODS

We analysed the effects of complement depletion and of C5a inhibition on haemodynamic parameters, oxygen delivery (DO2), oxygen consumption (VO2), oxygen extraction ratio (OER) and blood lactate levels after live bacteria infusion in pigs.

RESULTS

In the first series of experiments, animals were decomplemented by cobra venom factor (CVF, 125 micrograms kg-1) and challenged with 1.3 x 10(9) Escherichia coli kg-1. In a second series, animals were treated with neutralizing anti-C5a monoclonal antibodies (mAb) T13/9 before infusion of an increased E. coli dosage (1 x 10(10) E. coli kg-1). Administration of Gram-negative bacteria resulted in hypotension, tachycardia, pulmonary hypertension and decreased cardiac output typical for severe sepsis. These alterations were more pronounced in animals challenged with a higher bacteria concentration (1 x 10(10) E. coli kg-1, n = 5) than with a lower dosage (1.3 x 10(9) E. coli kg-1, n = 4). Complement depletion by CVF injection 24 h before E. coli infusion (n = 4), or anti-C5a mAb T13/9 administration (n = 4) had no effect on the changes in haemodynamic parameters and in DO2 associated with E. coli challenge. Application of either 1.3 x 10(9) or 1 x 10(10) E. coli kg-1 resulted in a marked decrease in VO2 and an increase in blood lactate levels, whereas the OER did not change throughout the experiment. In contrast, pretreatment with CVF 24 h before low-dose E. coli (1.3 x 10(9) kg-1) administration resulted in a significant increase in VO2 (P < 0.05) and in OER (P < 0.05) compared with untreated septic animals (n = 4). No hyperlactaemia occurred in complement-depleted septic animals compared with complement-sufficient animals (P < 0.05). Animals challenged with a high E. coli dose (1 x 10(1) kg-1) and treated with anti-C5a mAbs showed a pronounced increase in VO2 and OER (P < 0.05) accompanied by an attenuated increase in lactate levels (P < 0.05) compared with untreated septic animals.

CONCLUSION

The results demonstrate an improved oxygen use after complement depletion in this model of severe Gram-negative sepsis. Furthermore, a similar effect was seen after specifically neutralizing C5a by mAbs, indicating a role of C5a in the underlying mechanism.

Elevated circulating E-selectin, intercellular adhesion molecule 1, and von Willebrand factor in patients with severe infection

To investigate interactions between the endothelium and leukocytes in patients with sepsis, we measured soluble adhesion molecules (sE-selectin and sICAM-1), von Willebrand factor antigen (vWf:Ag), myeloperoxidase (MPO), and lactoferrin (Lacto-f) as plasma markers of endothelial and neutrophil activation. We tested whether the five proteins were predictors of clinical severity, which was evaluated by simplified acute physiological score (SAPS), number of organ failures (MOF), acute lung injury (ALI), and subsequent final outcome. Levels of the five plasma markers were higher in patients with severe infection (n = 25) than in patients without sepsis (n = 7) and healthy volunteers (n = 9). In the study population, levels of sE-selectin, sICAM-1, and vWf:Ag were higher for nonsurvivors as well as for patients with septic shock or with bacteremia, and they were correlated with SAPS and MOF. Survival outcome was predicted with high sensitivity and specificity by initial plasma levels of sICAM-1 and vWf:Ag. The initial sICAM-1 level appeared to be an independent prognostic variable, based on a logistic regression analysis. Unlike sE-selectin, sICAM-1 remained at high levels indefinitely in nonsurvivors. We conclude that, unlike neutrophil activation markers, levels of endothelium-derived soluble adhesion molecules and vWf:Ag in severe sepsis syndrome are correlated with the severity of illness and may be considered as predictors of survival outcome.