Antibiotic induced endotoxin release and clinical sepsis: a review

Phage therapy: eco-physiological pharmacology

Bacterial virus use as antibacterial agents, in the guise of what is commonly known as phage therapy, is an inherently physiological, ecological, and also pharmacological process. Physiologically we can consider metabolic properties of phage infections of bacteria and variation in those properties as a function of preexisting bacterial states. In addition, there are patient responses to pathogenesis, patient responses to phage infections of pathogens, and also patient responses to phage virions alone. Ecologically, we can consider phage propagation, densities, distribution (within bodies), impact on body-associated microbiota (as ecological communities), and modification of the functioning of body "ecosystems" more generally. These ecological and physiological components in many ways represent different perspectives on otherwise equivalent phenomena. Comparable to drugs, one also can view phages during phage therapy in pharmacological terms. The relatively unique status of phages within the context of phage therapy as essentially replicating antimicrobials can therefore result in a confluence of perspectives, many of which can be useful towards gaining a better mechanistic appreciation of phage therapy, as I consider here. Pharmacology more generally may be viewed as a discipline that lies at an interface between organism-associated phenomena, as considered by physiology, and environmental interactions as considered by ecology.

Effects of cytokine-suppressive anti-inflammatory drugs on inflammatory activation in ex vivo human and ovine fetal membranes

Intrauterine infection and inflammation are responsible for the majority of early (<32 weeks) spontaneous preterm births (PTBs). Anti-inflammatory agents, delivered intra-amniotically together with antibiotics, may be an effective strategy for preventing PTB. In this study, the effects of four cytokine-suppressive anti-inflammatory drugs (CSAIDs:N-acetyl cysteine (NAC), SB239063, TPCA-1 and NEMO binding domain inhibitor (NBDI)) were assessed on human and ovine gestational membrane inflammation. Full-thickness membranes were collected from healthy, term, human placentas delivered by Caesarean section (n=5). Using a Transwell model, they were stimulatedex vivowith γ-irradiation-killedEscherichia coliapplied to the amniotic face. Membranes from near-term, ovine placentas were stimulatedin uterowith lipopolysaccharide,Ureaplasma parvumor saline control and subjected to explant culture. The effects of treatment with CSAIDs or vehicle (1% DMSO) on accumulation of PGE2and cytokines (human interleukin 6 (IL6), IL10 and TNFα; ovine IL8 (oIL8)) were assessed in conditioned media at various time points (3–20 h). In human membranes, the IKKβ inhibitor TPCA-1 (7 μM) and p38 MAPK inhibitor SB239063 (20 μM) administered to the amniotic compartment were the most effective in inhibiting accumulation of cytokines and PGE2in the fetal compartment. NAC (10 mM) inhibited accumulation of PGE2and IL10 only; NBDI (10 μM) had no significant effect. In addition to the fetal compartment, SB239063 also exerted consistent and significant inhibitory effects in the maternal compartment. TPCA-1 and SB239063 suppressed oIL8 production, while all CSAIDs tested suppressed ovine PGE2production. These results support the further investigation of intra-amniotically delivered CSAIDs for the prevention of inflammation-mediated PTB.

Targeting the bacteria-host interface: strategies in anti-adhesion therapy

Bacterial infections are a major cause of morbidity and mortality worldwide and are increasingly problematic to treat due to the rise in antibiotic-resistant strains. It becomes more and more challenging to develop new antimicrobials that are able to withstand the ever-increasing repertoire of bacterial resistance mechanisms. This necessitates the development of alternative approaches to prevent and treat bacterial infections. One of the first steps during bacterial infection is adhesion of the pathogen to host cells. A pathogen’s ability to colonize and invade host tissues strictly depends on this process. Thus, interference with adhesion (anti-adhesion therapy) is an efficient way to prevent or treat bacterial infections. As a basis to present different strategies to interfere with pathogen adhesion, this review briefly introduces general concepts of bacterial attachment to host cells. We further discuss advantages and disadvantages of anti-adhesion treatments and issues that are in need of improvement so as to make anti-adhesion compounds a more broadly applicable alternative to conventional antimicrobials.

Biophysical mechanisms of the neutralization of endotoxins by lipopolyamines

Endotoxins (lipopolysaccharides, LPS) are one of the strongest immunostimulators in nature, responsible for beneficial effects at low, and pathophysiological effects at high concentrations, the latter frequently leading to sepsis and septic shock associated with high mortality in critical care settings. There are no drugs specifically targeting the pathophysiology of sepsis, and new therapeutic agents are therefore urgently needed. The lipopolyamines are a novel class of small molecules designed to sequester and neutralize LPS. To understand the mechanisms underlying the binding and neutralization of LPS toxicity, we have performed detailed biophysical analyses of the interactions of LPS with candidate lipopolyamines which differ in their potencies of LPS neutralization. We examined gel-to-liquid crystalline phase behavior of LPS and of its supramolecular aggregate structures in the absence and presence of lipopolyamines, the ability of such compounds to incorporate into different membrane systems, and the thermodynamics of the LPS:lipopolyamine binding. We have found that the mechanisms which govern the inactivation process of LPS obey similar rules as found for other active endotoxin neutralizers such as certain antimicrobial peptides.

Continuous progression of tubercular serpiginous-like choroiditis after initiating antituberculosis treatment

PURPOSE

To describe the frequency, risk factors, management, and outcome of eyes with tubercular serpiginous-like choroiditis showing continued progression following initiation of antituberculosis treatment.

DESIGN

Retrospective, comparative, interventional case series.

METHODS

SETTING

Institutional.

PATIENT POPULATION

One hundred ten patients of serpiginous-like choroiditis with 1) complete records, 2) tuberculin skin test, 3) active lesions in at least 1 eye, and 4) minimum 18 months follow-up.

INTERVENTION

Based on the positivity of tuberculin skin test, the patients were categorized in Group A (84 patients with positive tuberculin test) and Group B (26 patients with negative tuberculin test). Of the 84 patients in Group A, 19 received systemic corticosteroids while 65 also received 4-drug antituberculosis treatment in addition. All patients in Group B received corticosteroids. Patients with continued progression received an increased dose of corticosteroids with or without immunosuppressive agents.

MAIN OUTCOME MEASURE

Development of continued progression.

RESULTS

There were 61 men and 23 women in Group A and 19 men and 7 women in Group B. Continued progression was observed in 12 patients (14.28%) in Group A and none in Group B (P = .04). Of the 12 patients in Group A showing progression, 11 (16.9%) were receiving antituberculosis treatment and corticosteroids. The lesions responded in all eyes, and final visual acuity of 20/40 or better could be achieved in 10 eyes (75%).

CONCLUSION

Continued progression of choroiditis lesions occurs in 14% of patients after initiating antituberculosis treatment in tubercular serpiginous-like choroiditis. Increased immunosuppression with continuation of antituberculosis treatment resulted in good outcome.

ε/ζ systems: their role in resistance, virulence, and their potential for antibiotic development

Cell death in bacteria can be triggered by activation of self-inflicted molecular mechanisms. Pathogenic bacteria often make use of suicide mechanisms in which the death of individual cells benefits survival of the population. Important elements for programmed cell death in bacteria are proteinaceous toxin-antitoxin systems. While the toxin generally resides dormant in the bacterial cytosol in complex with its antitoxin, conditions such as impaired de novo synthesis of the antitoxin or nutritional stress lead to antitoxin degradation and toxin activation. A widespread toxin-antitoxin family consists of the ε/ζ systems, which are distributed over plasmids and chromosomes of various pathogenic bacteria. In its inactive state, the bacteriotoxic ζ toxin protein is inhibited by its cognate antitoxin ε. Upon degradation of ε, the ζ toxin is released allowing this enzyme to poison bacterial cell wall synthesis, which eventually triggers autolysis. ε/ζ systems ensure stable plasmid inheritance by inducing death in plasmid-deprived offspring cells. In contrast, chromosomally encoded ε/ζ systems were reported to contribute to virulence of pathogenic bacteria, possibly by inducing autolysis in individual cells under stressful conditions. The capability of toxin-antitoxin systems to kill bacteria has made them potential targets for new therapeutic compounds. Toxin activation could be hijacked to induce suicide of bacteria. Likewise, the unique mechanism of ζ toxins could serve as template for new drugs. Contrarily, inhibition of virulence-associated ζ toxins might attenuate infections. Here we provide an overview of ε/ζ toxin-antitoxin family and its potential role in the development of new therapeutic approaches in microbial defense.

A clinical study on the effects and mechanism of xuebijing injection in severe pneumonia patients

OBJECTIVE

To observe the effects of Xuebijing Injection in patients with severe pneumonia, and to explore the mechanism.

METHODS

Eighty cases of severe pneumonia are randomly assigned to the Xuebijing treatment (forty cases) and the control group (forty cases), with the same routine therapy provided in both groups. Clinical effective rates, inflammatory factors and organ function were observed in both groups.

RESULTS

The effective rate was higher in Xuebijing group than that of the control group (80.0% vs. 67.5%, P < 0.05). As compared with the control group, the LDH, alpha1-AG, alpha1-AT levels and the peak body temperature decreased markedly with the Xuebijing treatment going, and the secretion of TNF-alpha, IL-6, IL-8 was suppressed in Xuebijing group; but no significant difference was found in leptin level.

CONCLUSION

Xuebijing Injection may show a protective effect in patients with severe pneumonia. The mechanism is possibly with the decreased secretion of TNF-alpha, IL-6, and IL-8.

Why should we measure bacterial load when treating community-acquired pneumonia?

PURPOSE OF REVIEW

We focus on a number of studies in the past 2 years that herald a dramatic shift in how we treat patients with not just community-acquired pneumonia (CAP), but potentially all sepsis.

RECENT FINDINGS

Recent studies report that high bacterial load, and specifically pneumococcal load in CAP, appears to be significantly associated with worse outcomes. These findings change the sepsis paradigm. Bacterial load may identify potential candidates for adjunctive therapy, ICU admission and more aggressive management.

SUMMARY

Whereas we all acknowledge the importance of the virulence of the pathogen in the outcome of CAP, microbiological tests currently play little role in management of patients. Whereas molecular tests such as polymerase chain reaction have promised to deliver accurate results in a clinically useful period of time, apart from a few niche situations they have yet to enter routine practice. In particular the ability to calculate the bacterial load in blood, and specifically pneumococcal load in CAP, appears to have significant clinical utility. Not only does bacterial load predict clinical outcome, the data so far available challenge some of our fundamental assumptions about optimal antibiotic therapy and the pathogenesis of severe sepsis.

Pharmacological inhibition of inflammatory pathways for the prevention of preterm birth

The major cause of spontaneous preterm birth (sPTB) at less than 32 weeks of gestation is intrauterine inflammation as a consequence of colonisation of the gestational membranes by pathogenic microorganisms which trigger activation of the local innate immune system. This results in release of inflammatory mediators, leukocytosis (chorioamnionitis), apoptosis, membrane rupture, cervical ripening and onset of uterine contractions. Recent PCR evidence suggests that in the majority of cases of inflammation-driven preterm birth, microorganisms are present in the amniotic fluid, but these are not always cultured by standard techniques. The nature of the organism and its cell wall constituents, residence time in utero, microbial load, route of infection and extent of tissue penetration are all factors which can modulate the timing and magnitude of the inflammatory response and likelihood of progression to sPTB. Administration of anti-inflammatory drugs could be a viable therapeutic option to prevent sPTB and improve fetal outcomes in women at risk of intrauterine inflammation. Preventing fetal inflammation via administration of placenta-permeable drugs could also have significant perinatal benefits in addition to those related to extension of gestational age, as a fetal inflammatory response is associated with a range of significant morbidities. A number of potential drugs are available, effective against different aspects of the inflammatory process, although the pathways actually activated in spontaneous preterm labour have yet to be confirmed. Several pharmacological candidates are discussed, together with clinical and toxicological considerations associated with administration of anti-inflammatory agents in pregnancy.

We should be measuring genomic bacterial load and virulence factors

OBJECTIVE

To describe relevant pathogen-related characteristics and their impact on sepsis pathogenesis and prognosis.

DATA SOURCE

Current literature regarding genomic bacterial load and virulence factors, with an emphasis on the impact of these factors on pathophysiology and prognosis of sepsis.

DATA EXTRACTION AND SYNTHESIS

The current paradigm on sepsis pathophysiology and management overlooks aspects concerning the nature and characteristics of the infecting pathogen. Our findings suggest that evaluation of genomic bacterial load might be useful to assess severity and predict prognosis in septic patients; its use during treatment for monitoring clinical response is another interesting potential application. Virulence factors identification might help to develop pathogen-specific therapeutic strategies for higher-risk septic patients.

CONCLUSIONS

The recognition of the importance of quantifying the pathogen has major clinical implications and will open up a new field of exploration of therapies targeted at anticipating development and appropriate treatment in severe sepsis. The improved detection and understanding of bacterial virulence factors may lead to specific therapies.

Clinical and microbial efficacy of antimicrobial treatments of experimental avian colibacillosis

The clinical and microbial efficacy of antimicrobial treatments of avian colibacillosis was studied, using an experimental model on chickens previously inoculated with multiresistant commensal Escherichia coli strains. One E. coli with pMG252 plasmid containing bla(FOX5) and qnrA1 genes and another E. coli with pMG298 plasmid containing bla(CTX-M15) and qnrB1 genes were first orally inoculated to chickens Both isolates were also resistant to chloramphenicol, sulphamethoxazole, trimethoprim, streptomycin, gentamicin, kanamycin, and tetracycline. The birds were then experimentally infected with an avian pathogenic E. coli (APEC), via the air sac. Treatments (oxytetracycline (OTC), trimethoprim-sulfadimethoxin (SXT), amoxicillin (AMX) or enrofloxacin (ENR) were then offered at the therapeutic doses. Symptoms, lesions in dead or sacrificed birds, and isolation and characterization of APEC from internal organs were studied. Results showed that OTC, SXT or ENR treatments could control the pathology. AMX worsened the disease, possibly due to endotoxin shock. All APEC re-isolated from internal organs showed the same antimicrobial susceptibility as the APEC inoculated strain, except for one APEC isolate from an infected OTC-treated bird, which acquired tetracycline resistance only, and one APEC isolate recovered from the air sacs of a chicken in the infected SXT-treated group, which acquired the pMG252 plasmid and became multi-resistant. Thus three antimicrobials could control the disease but the experimental model enabled, to our knowledge, the first observation of plasmid transfer from a bacterium of the intestinal tract to a pathogenic isolate from the respiratory tract.

The role of proteomics in the diagnosis of chorioamnionitis and early-onset neonatal sepsis

Intrauterine infection is a unique pathologic process that raises the risk for early-onset neonatal sepsis (EONS). By acting synergistically with prematurity, EONS increases the risk for adverse neonatal outcomes, including intraventricular hemorrhage and cerebral palsy. Although several pathways for the pathogenesis of fetal damage have been proposed, the basic molecular mechanisms that modulate these events remain incompletely understood. Discovery of clinically and biologically relevant biomarkers able to reveal key pathogenic pathways and predict pregnancies at risk for antenatal fetal damage is a priority. Proteomics provides a unique opportunity to fill this gap.

Clinical aspects of invasive candidiasis: endocarditis and other localized infections

Candida endocarditis was previously considered a rare disease. However, its incidence is increasing, partly as a consequence of increased use of prosthetic intravascular devices. In patients with prosthetic valve endocarditis, Candida infection may occur via a two-step process; firstly, post-operative transitory candidaemia occurs during the intensive care unit stay, leading to colonization of the prosthetic valve and subsequent biofilm formation, with reduced susceptibility to antifungal agents. This theory lends support for pre-emptive antifungal therapy with agents that display activity against biofilm-associated Candida in patients with prosthetic heart valves at risk of candidaemia. Current guidelines recommend treatment with amphotericin B with or without 5-fluorocytosine, or an echinocandin, with valve replacement where possible. Recent data suggest that amphotericin B shows reduced activity against Candida biofilm, and poor penetration into vegetations and blood clots in experimental models of infectious endocarditis, whereas echinocandins, and in particular anidulafungin, display potent in vitro activity against sessile Candida cells within biofilms. The incidence of ocular candidiasis has been decreasing among inpatients with candidaemia, possibly because of earlier identification and treatment of candidaemia. The therapeutic approach includes prolonged treatment with fluconazole or voriconazole. The role of systemic echinocandins may be limited since they achieve undetectable vitreous concentrations. Vitrectomy with local instillation of amphotericin B, azoles or echinocandins may play a role in the treatment of chronic complications such as epiretinal membrane formation. The role of Candida in CNS infections is unclear. Diffuse encephalitis in candidaemia is misleading, since alterations of the mental status are generally attributed to candidaemia-associated sepsis syndrome, and neuroimaging studies and cerebrospinal fluid cultures are rarely performed as part of the diagnostic work-up. Osteomyelitis caused by Candida is considered infrequent. In contrast, Candida is frequently implicated in nosocomial non-postneurosurgery spondylodiscitis. Optimal management of such cases may require surgical debridement and, after initial intravenous antifungal therapy, prolonged administration of oral azoles. The role of Candida in endocarditis is fairly well established. With the increasing numbers of patients at risk of Candida endocarditis, there is a need for agents with potent efficacy against Candida biofilms. Echinocandins represent a potential therapeutic option in this setting. Antifungal agents may also be of use in the treatment of complications in patients with ocular candidiasis and in CNS infections.

The antigenome: from protein subunit vaccines to antibody treatments of bacterial infections?

New strategies are needed to master infectious diseases. The so-called "passive vaccination", i.e., prevention and treatment with specific antibodies, has a proven record and potential in the management of infections and entered the medical arena more than 100 years ago. Progress in the identification of specific antigens has become the hallmark in the development of novel subunit vaccines that often contain only a single immunogen, frequently proteins, derived from the microbe in order to induce protective immunity. On the other hand, the monoclonal antibody technology has enabled biotechnology to produce antibody species in unlimited quantities and at reasonable costs that are more or less identical to their human counterparts and bind with high affinity to only one specific site of a given antigen. Although, this technology has provided a robust platform for launching novel and successful treatments against a variety of devastating diseases, it is up till now only exceptionally employed in therapy of infectious diseases. Monoclonal antibodies engaged in the treatment of specific cancers seem to work by a dual mode; they mark the cancerous cells for decontamination by the immune system, but also block a function that intervenes with cell growth. The availability of the entire genome sequence of pathogens has strongly facilitated the identification of highly specific protein antigens that are suitable targets for neutralizing antibodies, but also often seem to play an important role in the microbe's life cycle. Thus, the growing repertoire of well-characterized protein antigens will open the perspective to develop monoclonal antibodies against bacterial infections, at least as last resort treatment, when vaccination and antibiotics are no options for prevention or therapy. In the following chapter we describe and compare various technologies regarding the identification of suitable target antigens and the foundation of cognate monoclonal antibodies and discuss their possible applications in the treatment of bacterial infections together with an overview of current efforts.

The effect of a multispecies probiotic on the composition of the faecal microbiota and bowel habits in chronic obstructive pulmonary disease patients treated with antibiotics

Short-term antibiotic treatment profoundly affects the intestinal microbiota, which may lead to sustained changes in microbiota composition. Probiotics may restore such a disturbance. The objective of the present study was to investigate the effect of a multispecies probiotic on the faecal microbiota during and after antibiotic intake in patients with a history of frequent antibiotic use. In this randomised, placebo-controlled, double-blind study, thirty chronic obstructive pulmonary disease (COPD) patients treated with antibiotics for a respiratory tract infection received 5 g of a multispecies probiotic or placebo twice daily for 2 weeks. Faecal samples were collected at 0, 7, 14 and 63 d. Changes in the composition of the dominant faecal microbiota were determined by PCR-denaturing gradient gel electrophoresis (DGGE). Changes in bacterial subgroups were determined by quantitative PCR and culture. Bowel movements were scored daily according to the Bristol stool form scale. During and after antibiotic treatment, DGGE-based similarity indices (SI) were high ( ≥ 84 %) and band richness was relatively low, both remaining stable over time. No difference in SI was observed between patients with and without diarrhoea-like bowel movements. The multispecies probiotic had a modest effect on the bacterial subgroups. Nevertheless, it affected neither the composition of the dominant faecal microbiota nor the occurrence of diarrhoea-like bowel movements. The dominant faecal microbiota was not affected by antibiotics in this COPD population, suggesting an existing imbalance of the microbiota, which may also have contributed to the lack of effect by probiotic intake.

Clinical review: a review and analysis of heart rate variability and the diagnosis and prognosis of infection

Bacterial infection leading to organ failure is the most common cause of death in critically ill patients. Early diagnosis and expeditious treatment is a cornerstone of therapy. Evaluating the systemic host response to infection as a complex system provides novel insights: however, bedside application with clinical value remains wanting. Providing an integrative measure of an altered host response, the patterns and character of heart rate fluctuations measured over intervals-in-time may be analysed with a panel of mathematical techniques that quantify overall fluctuation, spectral composition, scale-free variation, and degree of irregularity or complexity. Using these techniques, heart rate variability (HRV) has been documented to be both altered in the presence of systemic infection, and correlated with its severity. In this review and analysis, we evaluate the use of HRV monitoring to provide early diagnosis of infection, document the prognostic implications of altered HRV in infection, identify current limitations, highlight future research challenges, and propose improvement strategies. Given existing evidence and potential for further technological advances, we believe that longitudinal, individualized, and comprehensive HRV monitoring in critically ill patients at risk for or with existing infection offers a means to harness the clinical potential of this bedside application of complex systems science.

Candida infective endocarditis: report of 15 cases from a prospective multicenter study

Candida species are an uncommon cause of infective endocarditis (IE). Given the rarity of this infection, the epidemiology, prognosis, and optimal therapy of Candida IE are poorly defined. We conducted a prospective, observational study at 18 medical centers in Italy, including all consecutive patients with a definite diagnosis of IE admitted from January 2004 through December 2007.A Candida species was the causative organism in 8 cases of prosthetic valve endocarditis (PVE), 5 cases of native valve endocarditis (NVE), 1 case of pacemaker endocarditis, and 1 case of left ventricular patch infection. Candida species accounted for 1.8% of total cases, and for 3.4% of PVE cases. Most patients (86.6%) had a health care-associated infection. PVE associated with a health care contact occurred after a median of 225 days from valve implantation. Ten patients (66.6%) were treated with caspofungin alone or in combination with other antifungal drugs. The overall mortality rate was 46.6%. Mortality was higher in patients with PVE (5 of 8 cases, 62.5%) than in patients with NVE (2 of 5 patients, 40%). A better outcome was observed in patients treated with a combined medical and surgical therapy.Candida IE should be classified as an emerging infectious disease, usually involving patients with intravascular prosthetic devices, and associated with substantial related morbidity and mortality. Candida PVE usually is a late-onset disease, which becomes clinically evident even several months after an initial episode of transient candidemia.

Mechanism of action of vitamin C in sepsis: ascorbate modulates redox signaling in endothelium

Circulating levels of vitamin C (ascorbate) are low in patients with sepsis. Parenteral administration of ascorbate raises plasma and tissue concentrations of the vitamin and may decrease morbidity. In animal models of sepsis, intravenous ascorbate injection increases survival and protects several microvascular functions, namely, capillary blood flow, microvascular permeability barrier, and arteriolar responsiveness to vasoconstrictors and vasodilators. The effects of parenteral ascorbate on microvascular function are both rapid and persistent. Ascorbate quickly accumulates in microvascular endothelial cells, scavenges reactive oxygen species, and acts through tetrahydrobiopterin to stimulate nitric oxide production by endothelial nitric oxide synthase. A major reason for the long duration of the improvement in microvascular function is that cells retain high levels of ascorbate, which alter redox-sensitive signaling pathways to diminish septic induction of NADPH oxidase and inducible nitric oxide synthase. These observations are consistent with the hypothesis that microvascular function in sepsis may be improved by parenteral administration of ascorbate as an adjuvant therapy.

Anti-infective antibodies: a novel tool to prevent and treat nosocomial diseases

The emergence of multidrug-resistant bacteria is a growing challenge for healthcare in the treatment of infectious diseases. In particular, nosocomial infections are getting out of control and reduce the likelihood to recover without, sometimes lethal, complications and long-term damage. Current antibiotics are unable to keep nosocomial infections in check and novel ones move only reluctantly forward and are expected to only delay the problem of multidrug resistance. Progress made in the identification of suitable pathogen targets, a better understanding of host-parasite interactions and the recent inclusion of monoclonal antibodies into the arsenal of novel therapies has provoked the interest to revitalize a historical concept of medicine to treat and prevent bacterial infections with antibodies.

The effect of a multispecies probiotic on the intestinal microbiota and bowel movements in healthy volunteers taking the antibiotic amoxycillin

BACKGROUND

One of the side effects of antimicrobial therapy is a disturbance of the intestinal microbiota potentially resulting in antibiotic-associated diarrhea (AAD). In this placebo-controlled double-blind study, the effect of a multispecies probiotic on the composition and metabolic activity of the intestinal microbiota and bowel habits was studied in healthy volunteers taking amoxycillin.

METHODS

Forty-one healthy volunteers were given 500 mg amoxycillin twice daily for 7 days and were randomized to either 5 g of a multispecies probiotic, Ecologic AAD (10(9) cfu/g), or placebo, twice daily for 14 days. Feces and questionnaires were collected on day 0, 7, 14, and 63. Feces was analyzed as to the composition of the intestinal microbiota, and beta-glucosidase activity, endotoxin concentration, Clostridium difficile toxin A, short chain fatty acids (SCFAs), and pH were determined. Bowel movements were scored according to the Bristol stool form scale.

RESULTS

Mean number of enterococci increased significantly from log 4.1 at day 0 to log 5.8 (day 7) and log 6.9 (day 14) cfu/g feces (P < 0.05) during probiotic intake. Although no other significant differences were observed between both intervention groups, within each group significant changes were found over time in both microbial composition and metabolic activity. Moreover, bowel movements with a frequency >or=3 per day for at least 2 days and/or a consistency >or=5 for at least 2 days were reported less frequently in the probiotic compared to the placebo group (48%vs 79%, P < 0.05).

CONCLUSIONS

Apart from an increase in enterococci no significant differences in microbial composition and metabolic activity were observed in the probiotic compared with the placebo group. However, changes over time were present in both groups, which differed significantly between the probiotic and the placebo arm, suggesting that the amoxycillin effect was modulated by probiotic intake. Moreover, the intake of a multispecies probiotic significantly reduced diarrhea-like bowel movements in healthy volunteers receiving amoxycillin.

Synthetic lipopeptides: a novel class of anti-infectives

Lipopeptide daptomycin is one of the few recently approved antibiotics based on the novel mechanism of action. Recent advances in synthetic lipopeptides, driven by the biochemical and biophysical research, expanded their spectrum of antimicrobial activity and reduced their size to achieve economically viable production. Lipopeptides, consisting of a short peptide chain conjugated with an acyl chain, form a structurally defined conformation, which inserts into the bacterial membrane and dissipates its transmembrane potential. In addition to antimicrobial activity, synthetic lipopeptides also suppress inflammation through the neutralization of bacterial agonists of the innate immune response, synergize with conventional antibiotics and have improved proteolytic stability. Activities in animal models indicate that synthetic lipopeptides may surpass the natural lipopeptides as the perspective class of anti-infective agents.

Bacteriophages: an appraisal of their role in the treatment of bacterial infections

Bacteriophages were first used successfully to treat bacterial infections a decade before penicillin was discovered. However, the excitement that greeted those initial successes was short-lived, as a lack of understanding of basic phage biology subsequently led to a catalogue of clinical failures. As a consequence, bacteriophage therapy was largely abandoned in the West in favour of the newly emerging antibiotics. Now, as the problem of antibiotic resistance becomes ever more acute, a number of scientists and clinicians are looking again at bacteriophages as a therapeutic option in the treatment of bacterial infections. The chances of success second time round would appear to be much better given our current extensive knowledge of bacteriophage biology following their important role in underpinning the advances in molecular biology. We also have available to us the experience of nearly 80 years of clinical usage in the countries of the former Soviet Union and Eastern Europe as well as a political climate that encourages sharing of that knowledge. This review outlines those features of bacteriophages that contribute to their utility in therapy and explores the potential for their re-introduction into Western medicine. An abundance of clinical evidence is available in the Soviet literature but much of this is technically flawed and a more realistic appraisal of the clinical value of phages can be obtained from animal studies conducted in the West. As interest in bacteriophages increases, a number of companies throughout the world have begun investing in phage technology and this has led to novel approaches to therapy, some of which will be discussed.

In vitro activities of tachyplesin III against Pseudomonas aeruginosa

The in vitro activities of tachyplesin III were investigated against 20 multidrug-resistant Pseudomonas aeruginosa clinical isolates. Methods included minimal inhibitory concentrations, minimal bactericidal concentrations, time-kill studies, checkerboard titration method, endotoxin-binding activity and cytotoxicity assay. Overall the organisms were susceptible to the peptide at concentrations of 0.50-4 mg/l. Tachyplesin III completely inhibits the endotoxin procoagulant activity at 22.36 mg/l concentration. Fractional inhibitory concentration indexes demonstrated synergy between the peptide and betalactams or colistin. In conclusion, the intrinsic antibacterial and antiendotoxin activities and the synergistic interactions demonstrated with clinically used antibiotics make tachyplesin III valuable as potential candidate for new therapeutic strategies aimed to treat P. aeruginosa infection.

Rapid three-dimensional biointerfaces for real-time immunoassay using hIL-18BPa as a model antigen

With the goal of designing a rapid and affordable system of real-time immune monitoring for future diagnostic applications in sepsis, we have developed a biointerface composed of polyethyleneimine (PEI) and carboxymethylcellulose (CMC) to provide a means of prompt and facile immunoassay. Biointerface assembly is complete within 30 min, with all preparation performed and monitored within the measurement chamber of a quartz crystal microgravimetry with dissipation (QCM-D) sensor. Optimised biointerface composition, as determined by the mass of antibody immobilised, the level of antigen detection, and the amount of non-specific binding of human serum albumin, was determined to consist of a 4.0 mg/mL CMC hydrogel layer cross-linked to a 0.5 mg/mL PEI sub-layer. Tapping mode atomic force microscopy (AFM) in liquid demonstrates highly uniform and smooth surfaces using these hydrogels. Sensitivity of the biointerface for rhIL-18BPa is 400 ng/mL, with detection of 1 microg/mL achievable following 25 surface regenerations. Performance of the biointerface is verified using surface plasmon resonance (SPR), demonstrating the ability of the biointerface to be applied across platforms.

Combination of antimicrobial and endotoxin-neutralizing activities of novel oleoylamines

A combination of antimicrobial and endotoxin-neutralizing activities is desired in order to prevent progression from infection to sepsis due to the release of lipopolysaccharide from dying gram-negative bacteria. Lipopolyamines have emerged as a new type of endotoxin-neutralizing compound, but their antimicrobial activity has not been investigated. We synthesized a series of 10 oleoylamines differing in the polyamino head group, particularly in the number and separation between nitrogen atoms and the position of the oleoyl moiety. Compounds showed activity against both gram-negative and gram-positive bacteria in the micromolar range. Compounds were able to provide penetration of ethidium bromide into bacteria, indicating effects on the bacterial membrane. Oleoylamines neutralized endotoxin in Limulus amoebocyte lysate assays and by neutralization of tumor necrosis factor alpha release in human blood. Comparison of biological activities of compounds identified structural properties responsible for antimicrobial activity, and quantitative structure-property relationship analysis provided a quantitative model for prediction of activity of oleoylamines.

Clinical laboratory differentiation of infectious versus non-infectious systemic inflammatory response syndrome

OBJECTIVE

To evaluate the accuracy of C-reactive protein (CRP), procalcitonin (PCT), neopterin, and endotoxin in the differential diagnosis of sepsis and non-infectious systemic inflammatory response syndrome (SIRS).

METHODS

A Medline database and references from identified articles were used to perform a literature search relating to the differential diagnosis of sepsis versus non-infectious SIRS.

RESULTS

CRP, PCT, and neopterin are released both in sepsis and in non-infectious inflammatory disease. CRP and PCT are equally effective, although not perfect, in differentiating between sepsis and non-infectious SIRS. However, CRP and PCT have different kinetics and profiles. The kinetics of CRP is slower than that of PCT, and CRP levels may not further increase during more severe stages of sepsis. On the contrary, PCT rises in proportion to the severity of sepsis and reaches its highest levels in septic shock. PCT tends to be higher in nonsurvivor than in survivor. Therefore, PCT demonstrated a closer correlation with the severity of sepsis and outcome than CRP. Unlike CRP and PCT, neopterin is increased in viral infection as well as bacterial infection, and neopterin is also a useful indicator of sepsis. Endotoxemia was detected in no more than half of patients with Gram-negative bacteremia, and Gram-negative bacteremia was detected in half of patients with endotoxemia.

CONCLUSIONS

The diagnostic capacity of PCT is superior to that of CRP due to the close correlation between PCT levels and the severity of sepsis and outcome. Neopterin is very useful in the diagnosis of viral infection. The endotoxin assay in combination with CRP, PCT, or neopterin may help as a diagnostic marker for Gram-negative bacterial infection.

Bacterial Biofilms and Ocular Infections

Serious bacterial infections of the eye are often associated with abiotic prosthetic materials, such as contact lenses, intraocular lenses, and scleral buckles. In recent years, microbiologists have recognized substantial differences between bacteria growing in a sessile community attached to a surface and free-living or planktonic bacteria. These sessile surface-attached communities are known as biofilms, whose properties have important consequences for clinical medicine. As a population, bacteria in biofilms are more resistant to antimicrobial agents and the immune system, and they are more persistent than planktonic bacteria in hostile environments. These characteristics are likely the result of both biofilm-specific phenotypes and increased phenotypic diversity within biofilms as compared with planktonic communities of bacteria. Bacterial biofilm formation has been observed on human tissues, as well as on abiotic prosthetic devices. A better understanding of biofilm formation may lead to the development of novel antimicrobial agents as well as prosthetic devices that are resistant to bacterial colonization.

Whole blood-mediated endothelial permeability and adhesion molecule expression: a model study into the effects of bacteria and antibiotics

AIM

To investigate whether the inflammatory response of cultured endothelial cells, as induced by conditioned plasma, depends on the bacterial species or type of antibiotic used for incubation with whole blood.

MATERIALS AND METHODS

Blood from healthy volunteers was stimulated ex vivo with different microorganisms, and with bacteria killed with different antibiotics. The resultant plasmas were incubated on monolayers of cultured human endothelial cells, followed by measurement of their permeability to albumin and expression of E-selectin and intercellular adhesion molecule-1.

RESULTS

Incubation of Escherichia coli in blood yielded plasmas that induced a marked increase in endothelial permeability and E-selectin expression. The response to Bacteroides fragilis or Enterococcus faecalis was generally weaker. Similar effects were observed after incubation of whole blood with lipopolysaccharide (LPS). Much of the permeability and adhesion molecule response to E. coli remained after removal of intact microorganisms from the culture. Whereas antibiotic treatment of E. coli with imipenem or cefuroxime resulted in a divergent production of tumour necrosis factor-alpha (TNF-alpha) in blood, no significant differences between these treatments were observed with respect to the plasma-induced endothelial response.

CONCLUSION

Bacteria differ in their capacity to generate a whole blood-mediated increase of endothelial permeability and adhesion molecule expression; this response depends, at least in part, on the presence of soluble bacterial components, such as LPS. Whereas treatment with various antibiotics may generate varying amounts of TNF-alpha, these differences are not translated into differences in endothelial permeability or adhesion molecule expression.

Comparative effects of ciprofloxacin and ceftazidime on cytokine production in patients with severe sepsis caused by gram-negative bacteria

In the present study the effect of ciprofloxacin versus ceftazidime on concentrations of pro- and anti-inflammatory cytokines in the sera of patients with severe sepsis was evaluated. The study included 58 previously healthy patients suffering from severe sepsis caused by gram-negative bacteria, treated with either ciprofloxacin or ceftazidime after thorough clinical and microbiological evaluation and followed up for clinical outcome. Levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1b (IL-1b), IL-6, and IL-8 and of the anti-inflammatory cytokine IL-10, as well as of IL-1 receptor antagonist and soluble TNF receptors I and II, in serum were measured at baseline and 24 and 48 h after the first antimicrobial dose. Mean SAPS-II scores, development of septic shock, and mortality rates were similar in the two groups (43.2 +/- 9.2, 21.4%, and 14.3% in the ceftazidime group versus 49.8 +/- 11.3, 20%, and 13.3% in the ciprofloxacin group). Serum TNF-alpha and IL-6 levels at 24 and 48 h were significantly lower in the ciprofloxacin group, while the IL-10/TNF-alpha ratio was significantly higher, than those for the ceftazidime group. Among patients with high baseline TNF-alpha levels, there were significant increases in the IL-10/TNF-alpha ratio at both 24 and 48 h over that at admission for the ciprofloxacin group, while no differences were noted in the ceftazidime group. These results indicate that ciprofloxacin may have an immunomodulatory effect on septic patients by attenuating the proinflammatory response, while there is no evidence that differences in the cytokines measured have any impact on the final outcome.

Tumor necrosis factor-alpha allele lymphotoxin-alpha+250 is associated with the presence and severity of placental inflammation among preterm births

Histologic inflammation of placenta has been associated with increased risk for bronchopulmonary dysplasia and periventricular leukomalacia among preterm infants. Tumor necrosis factor-alpha (TNF-alpha) plays a central role in the regulation of inflammation. Some alleles of TNF (LT-alpha+250, TNF-alpha-308, and TNF-alpha-238) have been associated with susceptibility and/or severity of many diseases characterized by inflammation and/or involving the immune system. To determine whether alleles of TNF-alpha affect the risk and/or the severity of chorioamnionitis, we examined the placentas of 101 preterm births (birth weight <or=1250 g) for the presence of inflammation. Maternal and fetal chorioamnionitis (MCA and FCA, respectively) were graded for severity and staged for location of inflammatory infiltrate. Analysis for TNF-alpha alleles was done using PCR-restriction fragment length polymorphism technique on DNA extracted from infants' whole blood. MCA and FCA were seen in 45 and 38 placentas, respectively (p = 0.64). Genotypes of TNF-alpha-308 did not affect the development or the severity of placental inflammation. However, the AA genotype of LT-alpha+250 occurred more often when MCA and FCA were present compared with placentas without inflammation (p = 0.016 and p = 0.007, respectively). The GA genotype of TNF-alpha-238 was more common in placentas with severe MCA than with mild MCA (p = 0.015). The number of A alleles of LT-alpha+250 (GG = 0, GA = 1, AA = 2) correlated directly and significantly with grades and stages of MCA and FCA (p < 0.05). The AA genotype of LT-alpha+250 is associated with the development of chorioamnionitis among preterm births. The A allele of LT-alpha+250 seems to worsen the degree of placental inflammation.

Endotoxin challenge increases xanthine oxidase activity in cattle: effect of growth hormone and vitamin E treatment

In addition to its basic role in the metabolism of purine nucleotides, xanthine oxidoreductase (XOR) is involved in the generation of oxygen-derived free radicals and production and metabolic fate of nitric oxide (NO). Growth hormone (GH) and Vitamin E (E) have been shown previously to modify immune response to infection. Our objective was to determine in heifers the effect of endotoxin challenge (LPS; 3.0 microg/kg BW, i.v. bolus, Escherichia coli 055:B5) on xanthine oxidase (XO) activity in plasma and liver and the modification of this response by daily treatment with recombinant GH (0.1 mg/kg BW, i.m., for 12 days) or GH+E (E: mixed tocopherol, 1000 IU/heifer, i.m., for 5 days). In experiment 1, 16 heifers ( 348.7 +/- 6.1 kg) were assigned to control (C, daily placebo injections), GH, or GH+E treatments and were challenged with two consecutive LPS injections (LPS1 and LPS2, 48 h apart). After LPS1, plasma XO activity increased 290% (P < 0.001) at 3 h, reached peak (430%) at 24 h and returned to basal level by 48 h after LPS2. XO responses (area under the time x activity curve, AUC) were greater after LPS1 than LPS2 (P< 0.001). Total plasma XO responses to LPS (AUC, LPS1+LPS2) were augmented 55% (P < 0.05) over C with GH treatment but diminished to C responses in GH+E. There was a linear relationship (r2 = 0.605, P < 0.001) between total response in plasma XO activity and plasma nitrate + nitrate concentration. In experiment 2, 24 heifers ( 346 +/- 6 kg) were assigned to C or GH treatments and liver biopsy samples were obtained at 0, 3, 6, and 24h after a single LPS challenge. Hepatic XO activities increased 63.3% (P < 0.05) 6 h after single LPS challenge and remained elevated at 24 h (100.1%, P < 0.01) but were not affected by GH treatment. Results indicate that LPS-induced increases in plasma XO activity could be amplified by previous GH treatment but attenuated by E administration. The data also suggest that E may be effective in controlling some mediators of immune response associated with increased production of NO via the effect on XO activity and its production of superoxide anion as well as uric acid.

Frequency of Gram-negative bacterial pathogens in bloodstream infections and their resistance to antibiotics in the Czech Republic

A study performed at 12 hospitals in the Czech Republic in 2001 evaluated the Gram-negative bacterial pathogens most frequently associated with bloodstream infections and their susceptibility to a selection of antimicrobial agents. Of 831 Gram-negative strains, the most frequently isolated organisms were Escherichia coli (32%), Klebsiella pneumoniae (24%) and Pseudomonas aeruginosa (10%). E. coli isolates were relatively susceptible to the antibiotics tested, whereas K. pneumoniae were relatively resistant to all agents except meropenem, and P. aeruginosa to all agents except gentamicin and amikacin. Other agents showed variable rates of resistance to penicillins, third-generation cephalosporins, aminoglycosides and ciprofloxacin.

Determinants of Candidemia and Candidemia-Related Death in Cardiothoracic ICU Patients

STUDY OBJECTIVES

To develop and prospectively validate models of independent predictors of candidemia and candidemia-related death in cardiothoracic ICU (CICU) patients.

DESIGN

(1) An initial, prospective, one-center, case-control, independent predictor-model determining study; and (2) a prospective, two-center, model-validation study.

SETTING

The initial study was performed at the 14-bed CICU of the Onassis Cardiac Surgery Center, Athens, Greece; the model-validation study was performed at the Onassis Cardiac Surgery Center CICU and the 12-bed CICU of Henry Dunant General Hospital, Athens, Greece.

PATIENTS

In the initial study, 4,312 patients admitted to the Onassis Center CICU between March 1997 and October 1999 were considered for enrollment; 30 candidemic and 120 control patients (case/control ratio, 1/4) matched according to potential confounders were ultimately enrolled. In the model-validation study, 2,087 patients admitted to the Onassis and Henry Dunant CICUs between November 1999 and May 2002 were prospectively enrolled.

MEASUREMENTS AND RESULTS

Models of predictors of candidemia and associated death were constructed with stepwise logistic regression and subsequently validated. Independent candidemia predictors were ongoing invasive mechanical ventilation (IMV) > OR =10 days, hospital-acquired bacterial infection and/or bacteremia, cardiopulmonary bypass duration > 120 min, and diabetes mellitus. Model performance was as follows: sensitivity, 53.3%/57.9%; specificity, 100%/100%; positive predictive value (PPV), 100%/100%; negative predictive value (NPV), 88.9%/99.6%; and accuracy, 90.1%/99.6% (initial/model-validation study values, respectively). IMV > or =10 days and hospital-acquired bacterial infection/bacteremia were the two strongest candidemia predictors. APACHE (acute physiology and chronic health evaluation) II score > or =30 at candidemia onset independently predicted candidemia-related death with 80.0%/85.7% sensitivity, 80%/75% specificity, 66.7%/66.7% PPV, 88.9%/88.9% NPV, and 80.0%/78.9% accuracy (initial/model-validation study values, respectively).

CONCLUSIONS

We provided a set of easily determinable independent predictors of the occurrence of candidemia in CICU patients. Our results provide a rationale for implementing preventive measures in the form of independent predictor control, and initiating antifungal prophylaxis in high-risk CICU patients.

Antiendotoxin activity of antimicrobial peptides and glycopeptides

An animal study was performed to investigate the efficacy of two glycopeptides and two cationic peptides in the prevention of lethality in a septic shock rat model. Adult Wistar rats were given an intraperitoneal injection of 2x10(10) CFU of Escherichia coli ATCC 25922, with the exception of an uninfected control group (C0). Animals were randomized to receive, immediately after bacterial challenge, intraperitoneally isotonic sodium chloride solution (control group C1), 3 mg/Kg teicoplanin (group 1), 7 mg/Kg vancomycin (group 2), 1 mg/Kg colistin (group 3), 1 mg/Kg buforin II (group 4), or 60 mg/Kg piperacillin (group C(PIP)). In addition, four groups (1a, 2a, 3a, and 4a) received the above mentioned drugs in combination with piperacillin. All compounds and combinations significantly reduced the lethality and the number of E. coli in abdominal fluid compared with C1 group, with the exception of the glycopeptides. Colistin and buforin II combined with piperacillin significantly decreased the lethality compared with piperacillin alone. Finally, colistin, buforin II, and teicoplanin significantly reduced plasma endotoxin concentration in comparison with piperacillin and saline treatment. Antimicrobial peptides and teicoplanin act as antiendotoxin agents and enhance the efficacy of piperacillin.