Single-Molecule Pycnometry and Shape Analysis of Ions in the Gas Phase

The analysis of ions and clusters by mobility-classified mass spectrometry provides information on the mobility of analytes in the drift gas and the analyte mass. Mass equivalent and mobility equivalent diameters of globular analytes, such as ions, poly(ethylene glycol) (PEG), and ionic liquid nanodroplets, can be correlated with good accuracy by the Stokes-Millikan mobility model. A prerequisite to such an analysis is, however, the assumption of a globular analyte shape, which then allows determination of material density for globular ions. We show that the analyte density can be evaluated with high precision, independent of any assumptions on the analyte shape, by careful analysis of analyte-PEG-cluster ions following the concept of classical pycnometry. In particular, the analyte is entrapped in a globular PEG-analyte droplet. Based on the now independently derived mobility diameter and volume equivalent diameter, it is possible to attribute two parameters, size and shape, to the analyte molecule. We demonstrate the approach for lysozyme, cyano-cobalamin (vitamin B12), and glucose, which cover two orders of magnitude in analyte mass (180···14 300 Da). The derived densities for these analytes are highly accurate, i.e., they deviate less than 1% from literature values. Our method can be applied to newly synthesized molecules, supramolecular assemblies, isolated biomolecules, and molecular clusters, where only minor amounts of materials are available. The obtained shape parameters of lysozyme and cyano-cobalamin agree well with the expected molecular shapes. Data evaluation relies only on locations of the species in the mass-mobility plane and is in principle independent of any mobility theory. Our approach is thus robust with respect to experimental uncertainties and produces identical results irrespective of the type of mobility classification and drift gas.

Efficient quenching sheds light on early stages of gold nanoparticle formation

The formation mechanism of plasmonic gold nanoparticles (Au NPs) by fast NaBH₄ induced reduction of the precursors is still under debate. In this work we introduce a simple method to access intermediate species of Au NPs by quenching the solid formation process at desired time periods. In this way, we take advantage of the covalent binding of glutathione on Au NPs to stop their growth. By applying a plethora of precise particle characterization techniques, we shed new light on the early stages of particle formation. The results of in situ UV/vis measurements, ex situ sedimentation coefficient analysis by analytical ultracentrifugation, size exclusion high performance liquid chromatography, electrospray ionization mass spectrometry supported by mobility classification and scanning transmission electron microscopy suggest an initial rapid formation of small non-plasmonic Au clusters with Au₁₀ as the main species followed by their growth to plasmonic Au NPs by agglomeration. The fast reduction of gold salts by NaBH₄ depends on mixing which is hard to control during the scale-up of batch processes. Thus, we transferred the Au NP synthesis to a continuous flow process with improved mixing. We observed that the mean volume particle sizes and the width of the particle size distribution decrease with increasing flow rate and thus higher energy input. Mixing- and reaction-controlled regimes are identified.

Characterization of Electrospray Drop Size Distributions by Mobility-Classified Mass Spectrometry: Implications for Ion Clustering in Solution and Ion Formation Pathways

One of the outcomes of electrospray ionization is the size distribution of the droplets, which determines, together with the solvent composition and the source gas temperature, the minimum distance from the sprayer tip to the mass spectrometer inlet and therefore the ion transfer efficiency. Even more importantly, the average number of analyte molecules and, if present, contaminant species per droplet depend on the drop size. Consequently, the drop size distribution is a key parameter in nonspecific ion clustering in solution and ion suppression. The finding that small droplet sizes improve the mass spectral quality led to the development of nanoelectrospray sources, which dispense liquid flow rates below 0.1 μL/min and can generate drops with diameters smaller than 100 nm. However, current discussions on the effect of drop size on ion formation pathways and efficiencies remain qualitative because the exact drop size distributions are unknown. Here, we show that ion mobility-classified mass spectrometry of raffinose cluster ions allows us to determine very precisely the drop size distribution generated by the electrospray source in positive- and negative-ion modes. Based on the derived drop size distributions, we can quantitatively predict nonspecific ion clustering and can extract accurate probabilities for emission of species from parent drops upon Coulomb fission.

Structure and adsorption behavior of high hydrostatic pressure-treated β-lactoglobulin

HYPOTHESIS

High hydrostatic pressure treatment causes structural changes in interfacial-active β-lactoglobulin (β-lg). We hypothesized that the pressure-induced structural changes affect the intra- and intermolecular interactions which determine the interfacial activity of β-lg. The conducted experimental and numerical investigations could contribute to the mechanistic understanding of the adsorption behavior of proteins in food-related emulsions.

EXPERIMENTS

We treated β-lg in water at pH 7 with high hydrostatic pressures up to 600 MPa for 10 min at 20 °C. The secondary structure was characterized with Fourier-transform infrared spectroscopy (FTIR) and circular dichroism (CD), the surface hydrophobicity and charge with fluorescence-spectroscopy and ζ-potential, and the quaternary structure with membrane-osmometry, analytical ultracentrifugation (AUC) and mass spectrometry (MS). Experimental analyses were supported through molecular dynamic (MD) simulations. The adsorption behavior was investigated with pendant drop analysis.

FINDINGS

MD simulation revealed a pressure-induced molten globule state of β-lg, confirmed by an unfolding of β-sheets with FTIR, a stabilization of α-helices with CD and loss in tertiary structure induced by an increase in surface hydrophobicity. Membrane-osmometry, AUC and MS indicated the formation of non-covalently linked dimers that migrated slower through the water phase, adsorbed more quickly due to hydrophobic interactions with the oil, and lowered the interfacial tension more strongly than reference β-lg.

Probing sedimentation non-ideality of particulate systems using analytical centrifugation

Analytical centrifugation is a versatile technique for the quantitative characterization of colloidal systems including colloidal stability. The recent developments in data acquisition and evaluation allow the accurate determination of particle size, shape anisotropy and particle density. High precision analytical centrifugation is in particular suited for the study of particle interactions and concentration-dependent sedimentation coefficients. We present a holistic approach for the quantitative determination of sedimentation non-ideality via analytical centrifugation for polydisperse, plain and amino-functionalized silica particles spanning over one order of magnitude in particle size between 100 nm and 1200 nm. These systems typically behave as neutral hard spheres as predicted by auxiliary lattice Boltzmann simulations. The extent of electrostatic interactions and their impact on sedimentation non-ideality can be quantified by the repulsion range, which is the ratio of the Debye length and the average interparticle distance. Experimental access to the repulsion range is provided through conductivity measurements. With the experimental repulsion range at hand, we estimate the effect of polydispersity on concentration-dependent sedimentation properties through a combination of lattice Boltzmann and Brownian dynamics simulations. Finally, we determine the concentration-dependent sedimentation properties of charge-stabilized, fluorescently-labeled silica particles with a nominal particle size of 30 nm and reduced interparticle distance, hence an elevated repulsion range. Overall, our results demonstrate how the influence of hard-sphere type and electrostatic interactions can be quantified when probing sedimentation non-ideality of particulate systems using analytical centrifugation even for systems exhibiting moderate sample heterogeneity and complex interactions.

Mobility-Classified Mass Spectrometry Reveals a Complete Picture of the Electrospray Outcome

Electrospray ionization mass spectrometry supported by mobility classification (ESI-DMA-MS) is a strong technique for a comprehensive analysis of organic and inorganic clusters and small nanoparticles. In-depth understanding and optimization of the electrospray process are key for unlocking new fields of application and for extension of the accessible range of data. We show that the combination of mobility-classified mass spectrometry (DMA-MS) with an electrospray operated in a well-defined cone-jet mode is capable of providing a full picture of the outcome of the electrospray process including the evaporation residues of the parent droplets. Based on ESI-DMA-MS measurements of lysozyme, we find that clusters up to almost 1 MDa (around 60 lysozyme molecules per cluster) formed as evaporation residues of the parent droplets can be detected. The escape probability of lysozyme molecules from the parent droplets is polarity-dependent. A quantitative analysis of clusters is possible at analyte concentrations where the likeliness of finding more than a single molecule in the generated droplet is low. At higher concentrations, one can, however, quantify the analyte concentration from the detected size of the droplet evaporation residues. The approach is widely applicable for organic and inorganic nanostructures. The results allow clear statements on the conditions under which mixtures of larger molecules, clusters, and nanoparticles are accessible to quantitative analysis by mass spectrometry.

[Antibiotic stewardship (ABS). Part 1: Basics]

Against the background of increasing antimicrobial resistance, antibiotic stewardship (ABS) is an important measure to counteract the spread of resistant pathogens and multidrug resistance. For Germany and Austria, a comprehensive S3 guideline is available, which was last updated in 2018. The control of antibiotic or anti-infective use in hospitals should be guided by specialized ABS teams. At the hospital level, ABS also includes a structured ongoing analysis of local antibiotic use and resistance data. Recommendations for locally adapted therapy regimens should be derived and implemented from this data analysis. ABS consists of regular ward rounds ("ABS visits"), during which members of the ABS team review the indication, dosage, route of administration and duration of antimicrobial therapy at the bedside. Here, the key challenge is to save antibiotics without compromising the individual patient. Digitalization and artificial intelligence offer new options for ABS, while the adaption of inpatient concepts to outpatient care is also important.

[Antibiotic stewardship (ABS). Part 2: Application]

Antibiotic stewardship (ABS) is an important measure to counteract the spread of resistant pathogens and multidrug resistance. The most important ABS tools include the implementation of local guidelines, the development of a house-related list of anti-infective agents, regular ABS visits and practice-oriented internal training events. Effective strategies for therapy optimization include indication testing and therapy evaluation, dose optimization as well as determining an appropriate duration of therapy. Oralization of anti-infectives (sequence therapy) should be supported by consistent clinical criteria in in-house guidelines. The incidence of Clostridioides difficile infections (CDI) can be more than halved by restricting the so-called "4C antibiotics". Point-of-care tests help to minimize the use of antibiotics in the outpatient setting. Vaccination reduces the need for antibiotic therapy.

How to avoid interfering electrochemical reactions in ESI-MS analysis

The presence of electrochemical reactions occurring in an electrospray processes at the point where the current enters the liquid is discussed since the early 1990's. This current transfer to the liquid results in oxidation or reduction of either electrolyte species in the liquid sprayed or of the electrode material in contact with the liquid. As a result, new chemical species are generated. These products of the electrochemical reaction might be detected as altered species in mass spectra; they might be volatile and not recognized at all or accumulate on the electrode surface and cause cross contamination later on. In other cases, it might happen that the products of the electrochemical reactions are the only detectable species formed from an otherwise nondetectable analyte. An electrospray setup in which electrochemical reactions do not interfere with the analyte under investigation excludes the electrochemical reaction as source of sample contamination and sample altering and may serve as reference setup for experiments focused on the electrochemical reaction itself. We present a simple and inexpensive current coupling approach and specify operation conditions for which any impact of the electrochemical reaction on the sample under investigation is inherently excluded. On the basis of a practical example, we show the impact of the electrochemical reaction on sample composition and demonstrate the benefit of using the proposed current coupling method. Because of the obvious benefit of this method and its simple realization, it has the potential to be employed as standard feeding approach, especially for electrosprays operated at small flow rates.

Ionomer and protein size analysis by analytical ultracentrifugation and electrospray scanning mobility particle sizer

By combining analytical ultracentrifugation (AUC) in liquid phase and scanning mobility particle sizer (SMPS) in the gas phase, additional information on the particle size and morphology has been obtained for rigid particles. In this paper, we transfer this concept to soft particles, allowing us to analyze the size and molar mass of the short side chain perfluorosulfonic acid ionomer Aquivion^® in a dilute aqueous suspension. The determination of the primary size and exact molar mass of this class of polymers is challenging since they are optically transparent and due to the formation of different aggregate structures depending on the concentration and solvent properties. First, validation of AUC and SMPS measurements was carried out using the well-defined biopolymers bovine serum albumin (BSA) and lysozyme (LYZ) to confirm the reliability of the results of the two unique and independent classifying methods. Then, the ionomer Aquivion^® was studied using both techniques. From the mean molar mass of 185 ± 14 kDa obtained by AUC, a mean hydrodynamic diameter of 7.6 ± 0.5 nm was calculated. The particle size obtained from SMPS (7.1 nm) agrees very well with the results from AUC showing that the molecule was transferred into the gas phase without significantly changing its structure. In conclusion, the Aquivion^® is molecularly dispersed in the used aqueous buffer solution without any aggregate formation in the investigated concentration range (< 2 g l^-1).

Determination of the length and diameter of nanorods by a combination of analytical ultracentrifugation and scanning mobility particle sizer

A combination of orthogonal measurement techniques is utilized in this study to predict the average lengths and diameters of colloidal nanorods. Sedimentation coefficient distributions and electrical mobility distributions obtained from analytical ultracentrifugation and a scanning mobility particle sizer, respectively, are used for the hydrodynamic correlation. The method is validated theoretically and application to Au and ZnO nanorod samples is shown. The results demonstrate that the combination of both measurement techniques is an excellent method for the two-dimensional characterization of nanorods.

[Gastrointestinal infections]

Infectious diarrhea is one of the most common diseases. This article summarizes the current state of the diagnostics and treatment and includes the most important pathogens, i.e. Norovirus, Rotavirus, Campylobacter, Salmonella, Shigella and pathogenic Escherichia coli. Infections caused by toxin-producing strains of Clostridium difficile are described in more detail due to the increasing importance. Symptomatic therapy is still the most important component of treatment. Empirical antibiotic therapy is reserved for severely ill patients with a high stool frequency, fever, bloody diarrhea, underlying immune deficiency or significant comorbidities. Increasing bacterial resistance (in particular against fluoroquinolones) has to be considered. Motility inhibitors are not recommended for infections due to Shiga toxin-producing E. coli, C. difficile infections (CDI) and severe enterocolitis caused by other pathogens. The macrocyclic antibiotic fidaxomicin can reduce the recurrence rate of CDI. Fecal microbiota transplantation (FMT) currently provides a reserve treatment option for multiple recurrences of CDI and is subject to the Medicines Act (Arzneimittelgesetz, AMG) in Germany.

[Clinical impact of infections with carbapenem-resistant enterobacteriaceae in liver transplant recipients]

Infections with carbapenem-resistant Enterobacteriaceae (CRE) are an emerging cause of morbidity and mortality among liver transplant recipients (LTR) worldwide, particularly Klebsiella pneumoniae carbapenemase (KPC)-producing organisms. Approximately 3 - 13 % of solid organ transplant recipients in CRE-endemic areas develop CRE infections, and the infection site correlates with the transplanted organ. The cumulative 30-day mortality rate of LTR infected with carbapenem-resistant K. pneumoniae is 36 %, and the 180-day mortality rate is 58 %. Awareness of the high vulnerability of LTR to fatal bacterial infection leads to the more frequent use of ultrabroad-spectrum empirical antibiotic therapy, which further contributes to the selection of extreme drug resistance. Moreover, it comprises a relevant risk of failure to initiate adequate empirical treatment due to the fact that culture-based techniques used to identify CRE imply a 48- to 72-hour delay from blood culture collection until administration of the targeted therapy. This vicious circle is difficult to avoid and leads to increased clinical intricacy and narrowed antimicrobial therapeutic options. Because available options are extremely limited, infection prevention measures have gained outstanding importance, particularly in the phase after liver transplant requiring intense immunosuppression early on. Improving clinical outcomes is a major challenge and involves a multi-targeted approach combining strictly applied hygiene measures, active surveillance tests, the use of modern, time-saving methods of molecular biology, and enforced antibiotic stewardship. This article reviews the current literature regarding the incidence and outcome of CRE infections in LTR, and it summarises current preventive and therapeutic recommendations to minimise the threat by CRE in real-life clinical transplant settings.

On the mechanism of Zn4O-acetate precursors ripening to ZnO: How dimerization is promoted by hydroxide incorporation

We report on a combined experimental and molecular modelling study on Zn4O ion clusters stabilized by acetate molecules (OAc). In particular, ab initio calculations of acetate substitution by hydroxide ions are compared with mass spectrometry data. Though quantum calculations in the gas phase indicate strong energetic preference, no experimental evidence of stable Zn4O(OAc)6-x(OH)x clusters in ethanolic solutions could be observed. This apparent contradiction is rationalized by identifying the supportive role of hydroxide ions for the association of (OAc(-) → OH(-) substituted) Zn4O(OAc)6 and Zn4O(OAc)5 (+) clusters. Mass spectrometry and quantum calculations hint at the stability of (Zn4O)2(OAc)12-x(OH)x dimers with x = 1, 2. Therein, the hydroxide ions establish salt-bridges that allow for the formation of additional Zn3 motifs with the OH above the triangle center-a structural motif close to that of the ZnO-crystal. The association of Zn4O(OAc)6 clusters is thus suggested to involve OAc(-) → OH(-) substitution as an activation step, quickly followed by dimerization and the subsequent agglomeration of oligomers.

Large hospital outbreak of KPC-2-producing Klebsiella pneumoniae: investigating mortality and the impact of screening for KPC-2 with polymerase chain reaction

BACKGROUND

Multi-drug-resistant Klebsiella pneumoniae carbapenemase (KPC)-2-producing K. pneumoniae are an increasing cause of healthcare-associated infections worldwide.

AIMS

To investigate the impact of clinical infection on mortality, and examine the effect of use of KPC-2-specific polymerase chain reaction (PCR) on the time to contact isolation during an outbreak.

METHODS

Cases were defined as patients clinically infected or colonized with KPC-2-producing K. pneumoniae between June 2010 and July 2012. Cases were described by demographic and health characteristics, and the association between infection and mortality, adjusted for comorbidities and demographic characteristics, was determined using Poisson regression with robust standard errors. A comparison was made between the time to contact isolation with a culture-based method and PCR using Wilcoxon's rank sum test.

FINDINGS

Of 72 cases detected, 17 (24%) had undergone transplantation and 21 (29%) had a malignancy. Overall, 35 (49%) cases were clinically infected, with pneumonia and sepsis being the most common infections. Infection was an independent risk factor for mortality (risk ratio 1.67, 95% confidence interval 0.99-2.82). The median time to contact isolation was 1.5 days (range 0-21 days) using PCR and 5.0 days (range 0-39 days) using culture-based methods (P = 0.003). Intermittent negative tests were observed in 48% (14/29) of cases tested using culture-based methods.

CONCLUSION

KPC-2-producing K. pneumoniae mainly affect severely ill patients. Half of the cases developed clinical infection, associated with increased risk of death. As PCR accelerates isolation and provides the opportunity for preventive measures in colonized cases, its use should be implemented promptly during outbreaks. Further studies are needed to enhance knowledge about KPC detection patterns and to adjust screening guidelines.

[Can the antibiotic prescription practice in a hospital be influenced by in-house guidelines? An interventional study at the University Hospital Halle (Saale), Germany]

BACKGROUND

In-house guidelines are an essential tool of antibiotic stewardship (ABS) programs to guide antimicrobial therapy. We studied the effect of in-house guidelines adapted to the local pathogen and resistance epidemiology on prescribing behavior.

METHODS

At the University Hospital Halle (Saale) guidelines for the antimicrobial therapy and essential microbiological diagnostics were introduced. Main objectives were reducing the use of third generation cephalosporines and fluoroquinolones, decreasing selection pressure for enterococci and multidrug-resistant Gram-negative bacteria, minimizing Clostridium difficile infections (CDI), and improving microbiological diagnostics to enhance de-escalation strategies. 12 months thereafter a comparison of antibiotic consumption, pathogen and resistance statistics and use of blood cultures was performed.

RESULTS

There was a decrease of third-generation cephalosporines (-18.6%) and fluoroquinolones (-9.8%), while consumption of broad- and intermediate-spectrum penicillins (+23.8% and +37%) as well as carbapenems (+11.9%) increased. The total volume of prescribed anti-infectives remained unchanged. The number of enterococcal isolates (-18.3%) and CDI (-26.3%) decreased considerably. Gram-negatives, particulary ESBL-producing Enterobacteriaceae, were detected more frequently due to an expanded screening program. The rate of blood cultures/1000 patient-days was unaffected.

CONCLUSION

In-house guidelines for the empiric antiinfective therapy appear to be suitable to influence the prescribing behavior and the selection pressure on individual pathogen groups. The total volume of antibiotic prescriptions was not affected in this study.

[Drug therapy of infectious diarrhea. Part 2: Chronic diarrhea]

Diarrheal diseases are among the most common diseases worldwide. In this review the current treatment recommendations for acute (Part 1) and chronic (Part 2) infectious diarrhea are summarized and typical enteropathogens are discussed. The second part of the article describes chronic diarrhea, its related pathogens and treatment. In contrast to acute diarrhea which is mainly caused by viral and typical bacterial pathogens, chronic diarrhea has mainly non-infectious origins. Protozoal pathogens, such as Giardia lamblia and Entamoeba histolytica in particular are found and more rarely bacterial pathogens, such as Tropheryma whipplei. Opportunistic pathogens cause diarrhea in immunocompromised patients, such as in HIV patients. In these patients cytomegalovirus (CMV) colitis or infections with Cryptosporidium spp., Cyclospora cayetanensis, Isospora belli or microsporidia have to be considered. Besides targeted specific antimicrobial therapy, anti-retroviral drugs improving the underlying immunosuppression and thus the reconstitution of the adaptive immune response remain a cornerstone of the treatment in HIV-positive patients.

Invasive cardiac aspergillosis after orthotopic liver transplantation

Invasive aspergillus infection occurs in 5 - 42 % of liver-transplanted recipients and is a dangerous complication, associated with high mortality if untreated. However, the early diagnosis of invasive aspergillosis can be elusive, as clinical signs are unspecific and the pathogenic agent is difficult to demonstrate. We here report about a 58-year-old man with acute liver failure caused by newly diagnosed chronic hepatitis B infection who underwent liver transplantation. The postoperative course was uneventful, and the patient was discharged after 30 days. After 105 days the patient was readmitted because of fever, recurrent chest and abdominal pain. Computed tomography revealed a cardiac lesion; other diagnostic steps including bone-marrow and endomycordial biopsy, virological and microbiological investigations gave no clear findings. To exclude a malignant process, thoracotomy with mass and simultaneous lower left lobe resection were performed. Histopathological findings revealed an invasive perimyocardial aspergillosis. Immediate intravenous therapy with voriconazole and caspofungin was initiated and monitoring of the mass was performed with transesophageal echocardiography and Cardio-MRI. Due to slightly increase of the lesion, medication was switched to posaconazole and caspofungin. Under this dual fungal treatment the lesion regressed and the patient could be discharged after two months in good clinical condition. Frequent Cardio-MRI scan after discharge showed further mass-regression. Therefore antifungal treatment was switched to oral posaconazole mono-therapy. After one year, complete reduction of the mass was achieved and antifungal therapy was discontinued. Recent diagnostic imaging follow-up showed no pathological finding.

[Clostridium difficile infection (CDI) in the course of time - an issue only for the internist?]

BACKGROUND

Toxigenic strains of Clostridium (C.) difficile are the most prevalent pathogens of antibiotic associated intestinal disease and nosocomial diarrhoea. During the last 10 years, incidences of C. difficile infection (CDI) have increased worldwide.

MATERIALS AND METHODS

With clinical and microbiological original data for 2002-2012 from the University Hospitals Leipzig and Halle (Saale), Germany, the authors illustrate the current situation regarding CDI in the states of Saxony and Saxony-Anhalt and exemplify the latest developments in terms of incidence, prevalence of resistance, diagnosis and treatment strategies regarding CDI with an emphasis on surgical options.

RESULTS

Following the general trend, at the University Hospitals of Leipzig and Halle (Saale) there was also an increase in incidence of CDI, especially of severe clinical courses. In primary and secondary care facilities, prevention of CDI is based on hygiene management and restricted usage of antibiotics, preferably as "Antibiotic Stewardship" programmes. In 2012, the new macrocyclic antibiotic Fidaxomicin was approved in the European Union for the treatment of CDI. The therapeutic armamentarium, previously based on metronidazole or vancomycin, has now been enriched by a substance that presumably will reduce the rate of recurrence of CDI. Moreover, early data from case series and controlled trials suggest that the re-establishment of eubiosis in the colon of patients with recurrent CDI by stool transplantation from healthy donors is an alternative to antibiotics. Standard surgical intervention for refractory CDI is subtotal colectomy with terminal ileostomy. In patients with adequate life expectancy and without organ dysfunction, a colon-saving surgical technique should be considered.

CONCLUSION

Taking antibiotics for most remains the main risk factor for suffering from symptomatic CDI. With the introduction of Fidaxomicin there is hope for an improvement in the conservative treatment of CDI. Stool transplants from healthy donors are now considered to be better than giving antibiotics for severe CDI, but this treatment has not found broad acceptance yet. In cases with a lack of early treatment success, the surgeon must be consulted. Here, the evidence for preferably colon-saving surgical procedures is so far unfortunately low.

[Pitfalls in Diagnosis and Therapy for CMV Colitis in a 30-Year-Old HIV-Positive Patient]

We report on a 30-year-old patient who presented with bloody diarrhoea. After initially, assuming a previously not diagnosed ulcerative colitis, an immunosuppressive therapy was initiated, a week later an HIV infection stage C2 according to the CDC classification, complicated by CMV viraemia, was diagnosed. In this case report the course of treatment with highly active antiretroviral therapy (HAART), ganciclovir and prednisolone is reported and discussed on the basis of histological, immunohistochemical and microbiological findings. The case illustrates the difficulty to distinguish between ulcerative colitis, immune reconstitution syndrome, CMV colitis and HIV-associated diarrhoea.

[Immunosuppressive treatment as a risk factor for the occurrence of clostridium difficile infection (CDI)]

BACKGROUND

Toxigenic Clostridium difficile strains are known as the most common infectious cause of antibiotic-associated intestinal disease and nosocomial diarrhoea. The increased incidence of hypervirulent strains gives rise to worldwide concern. In particular, courses with multiple recurrences are observed in the presence of immunosuppression.

METHODS

In this retrospective controlled observational study we aimed to determine immunosuppression as an independent risk factor for symptomatic CDI and to identify characteristics and differences of immunocompromised patients with respect to disease severity, disease progression, intestinal manifestations, recurrence rates and other factors. We compared symptoms and clinical features of 55 immunosuppressed patients with confirmed CDI with those of 50 patients without immunosuppressive medication (mean age 59.3 years ± 16.2 vs. 69.2 years ± 15.0) who were treated at the Departments of Internal Medicine I and IV of the University Hospital Halle (Saale), Germany, between 2006 and 2009. Multivariate analysis using binary logistic regression was performed for a control group of 105 patients without CDI. In this group, there were 62 patients without evidence of immunosuppression and 43 immunosuppressed patients (mean age 66.9 years ± 12.4 vs. 56.0 years ± 13.7).

RESULTS

The clinical courses of the two groups differed considerably. Immunosuppressed patients were significantly more frequently colonised with Clostridium difficile without clinically detectable manifestation or only mild clinical symptoms not requiring therapy (22 vs. 2 %, p = 0.003), while there were similar numbers of moderate (46 vs. 52 %, p = 0.503) but less severe CDI cases (27 vs. 40 %, p = 0.167). Relapses were observed more frequently in the group of immunosuppressed patients (15 vs. 6 %, p = 0.153). Multivariate analysis using logistic regression identified immunosuppression as an independent risk factor for CDI (OR = 2.75), in addition to prior antibiotic therapy (OR = 10.15) and PPI intake (OR = 2.93).

CONCLUSION

We conclude that immunosuppression has to be regarded as an independent risk factor for CDI. Immunosuppressive treatment increases the risk of colonisation and infection with Clostridium difficile and leads to a higher relapse rate in patients with CDI.

[Antibiotic treatment of enterococcal infections in gastroenterology with daptomycin - first experiences from the EU-CORE registry study (European Cubicin® Outcomes Registry and Experience)]

Enterococci are a frequent cause of nosocomial infections in gastroenterology. The increase of Enterococcus faecium infections with development of resistance to gentamicin and vancomycin as well as possible linezolid resistance require alternative antibiotic therapies. Study data show that daptomycin, a highly bactericidal antibiotic is effective in enterococcal infections. However, in Germany daptomycin is so far only approved for the treatment of complicated skin and soft tissue infections, bacteremia and infective endocarditis caused by Staphylococcus aureus. In the Department of Internal Medicine I, University Hospital Halle (Saale) from May 2 009 to April 2 010 all gastroenterological patients with evidence of invasive enterococcal infection received intravenous daptomycin treatment at inclusion in the European Cubicin® Outcomes Registry and Experience (EU-CORE). Gastroenterological diseases treated were necrotising pancreatitis, infected pancreatic pseudocysts, abscesses, obstructive cholangitis and sepsis. The clinical outcome was retrospectively detected by protocol-defined criteria. A total of 13 patients (8 male, 5 female, median age 59 years) with microbiologically assured enterococcal infections (10 × E. faecium, including 1 × VRE, 6 × E. faecalis, including double infections) were treated with intravenous daptomycin (6 mg per kg body weight). In the presence of polymicrobial infections (10 of 13 patients), an additional anti-infective therapy was initiated according to sensitivity testing. Concomitantly a direct focus approach with stenting, puncture or drainage was performed. The clinical cure rate was 92 % (12 of 13 patients). One patient died from a non-surgically uncontrollable malignancy (Klatskin tumour Bismuth IIIb). There were no adverse events. These results allow us to conclude that antibiotic therapy with daptomycin in invasive or bacteraemic enterococcal infections leads to high cure rates (up to 90 % and more) when concomitant and adequate focus relief is performed. Larger clinical studies to obtain an extended drug approval are desirable.

[Unexplained fever and B-symptoms in a young male Black African]

An immunocompetent Nigerian developed a fulminant hemophagocytic lymphohistiocytosis due to Epstein-Barr virus reactivation. The patient initially presented with fever, hepatosplenomegaly and pancytopenia. The clinical status of our patient deteriorated quickly despite treatment with corticoids. Escalation of immunosuppressive treatment was not possible. He died of lung, liver and circulatory failure in our intensive care unit.Hemophagocytic lymphohistiocytosis is a rare disease characterized by inflammation due to prolonged and excessive activation of antigen-presenting cells. High plasma ferritin levels and phagocytosis of hematopoetic cells in bone marrow, spleen and liver lead to the diagnosis. Hemophagocytic lymphohistiocytosis should therefore be included in the differential diagnosis in patients with persistent fever, hepatosplenomegaly and cytopenia.

[37-year old patient with fever, diarrhea and lymphadenopathy]

A 37-year-old homosexual man was admitted because of oropharyngeal pain, fever, diarrhea, loss of weight and lymphadenopathy since one week. Acute retroviral syndrome (ARS) in primary HIV type 1 infection was diagnosed, associated with Giardia lamblia infection. Antiinfective and combined antiretroviral treatment was established, and the general condition of the patient rapidly improved. The presented report demonstrates that in case of acute HIV-infection with diarrhea other infections should be considered, particularly with regard to enteropathogens like Giardia lamblia.

[Small bowel diverticula – diagnosis and complications]

Aquired diverticula of the small bowel (not Meckel?s diverticulum) have a prevalence of 1 to 5 % and are relatively common. They are usually asymptomatic. However, in rare cases they can cause unspecific abdominal symptoms and even critical complications that require surgical intervention. Patients with diverticula of the small bowel were selected from all patients treated at an university hospital of maximal care in a retrospective study covering nine years. In 72 patients with diverticula, 47 % were asymptomatic, 47 % had unspecific abdominal symptoms and 6 % presented acute complications. In 83 % diverticula were localised in the duodenum and proximal jejunum. More distal parts of the small intestine were affected with decreasing frequency. A disseminated affection of the entire small bowel was found in 4 % of all patients. Diagnosis was made by endoscopic techniques in most cases (87 %) and to a smaller extent by CT- and MR-imaging and by other methods. The pattern of complications found is similar to earlier studies. Endoscopic techniques have replaced enteroclysis as the most widespread diagnostic technique in diagnosis of small bowel diverticula.

[Small bowel diverticula - unknown disease]

Diverticula of the small bowel are quite frequent (about 5 %), but being a differential diagnosis of abdominal complaints they may still be underdiagnosed. One reason for the low level of suspicion for a complication of small bowel diverticula might be that the small bowel was out of the gastroenterologists' focus until recently when small bowel endoscopy became available as a reliable and practical diagnostic tool. Diverticula of the jejunum and the ileum may lead to diverticulitis, abscess, obstruction, bleeding, and perforation. Small intestinal bacterial overgrowth syndrome due to small bowel diverticula is a common complication and involves meteorism and malassimilation syndrome. Meckel's diverticulum sometimes provokes bleeding even in the young adult and resection of the diverticulum is clearly indicated. Contrariwise, incidental detection of a Meckel's diverticulum during abdominal laparotomy does not necessarily imply resection of the diverticulum. The juxtapapillary duodenal diverticula appear to be a risk factor for gallbladder stones, bile duct stones, and their recurrence. Moreover, the complication rate of endoscopic interventions of the bile system might be increased. In this review, we highlight the historical background of small bowel diverticular disease, present the epidemiological and pathophysiological implications and provide information on the diagnostic modalities that are available. Diseases of the primary acquired and congential small bowel diverticula are described in detail.

Ikterus und schwere Leberfunktionsst�rung bei der hormonablativen Behandlung des Prostatakarzinoms

Flutamide is an antiandrogen and frequently used for the treatment of prostatic cancer. Severe hepatotoxicity occurs in few patients but may be fatal. We report on two patients with prostatic cancer who received a therapy with flutamide. They showed different degrees of liver damage. One patient recovered completely after withdrawal of Flutamide under medication with steroids. Clinical symptoms and laboratory findings returned to normal within four weeks. Despite immediate withdrawal of Flutamide, the other patient showed a severe course with progressive liver dysfunction and hepatorenal syndrome. He finally died under the clinical picture of fulminant hepatic coma. This case represents the first death associated with flutamide in Germany. The literature concerning the metabolism of flutamide and the published cases of hepatotoxicity of this drug are reviewed.

Effective object recognition for automated counting of colonies in Petri dishes (automated colony counting)

Determination of the number of colonies (colony forming units, CFU) is a standard method in microbiological analysis to ensure the quality of drinking water. Normally this tedious work is still performed manually. A PC-based method for the automated counting of digitized images of Petri dishes is presented. The method includes highly specific and effective object recognition algorithms that ensure very high detection accuracy. The processing sequence implies internal controls therefore enabling reliable automated evaluations of series of images. Use of the Fuzzy formalism and the high adaptivity of the algorithms lead to an extraordinary user-friendliness. For digitization different devices like flatbed scanners or CCD-cameras can be used. Due to the highly adaptive algorithms samples from the routine standard preparation process in laboratories can be evaluated. The accuracy and quality of the method aim at advancement in objectivity of colony counting and quality control and assurance. The algorithms and the evaluation of the method are presented.

A human cDNA library for high-throughput protein expression screening

We have constructed a human fetal brain cDNA library in an Escherichia coli expression vector for high-throughput screening of recombinant human proteins. Using robot technology, the library was arrayed in microtiter plates and gridded onto high-density filter membranes. Putative expression clones were detected on the filters using an antibody against the N-terminal sequence RGS-His(6) of fusion proteins. Positive clones were rearrayed into a new sublibrary, and 96 randomly chosen clones were analyzed. Expression products were analyzed by SDS-PAGE, affinity purification, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, and the determined protein masses were compared to masses predicted from DNA sequencing data. It was found that 66% of these clones contained inserts in a correct reading frame. Sixty-four percent of the correct reading frame clones comprised the complete coding sequence of a human protein. High-throughput microtiter plate methods were developed for protein expression, extraction, purification, and mass spectrometric analyses. An enzyme assay for glyceraldehyde-3-phosphate dehydrogenase activity in native extracts was adapted to the microtiter plate format. Our data indicate that high-throughput screening of an arrayed protein expression library is an economical way of generating large numbers of clones producing recombinant human proteins for structural and functional analyses.

Evaluation of the AmpliSensor PCR and the SHARP signal detection system for the early prediction of symptomatic CMV infection in solid transplant recipients

BACKGROUND

Cytomegalovirus (CMV) is associated with high morbidity and mortality in transplant patients. Specific antiviral treatment at an early stage of CMV infection may effectively ameliorate, but not eliminate CMV disease in these patients. Presently, the pp65 antigenemia test on peripheral leukocytes is the method most widely used for predicting and monitoring transplant patients for active CMV infection. Nucleic acid amplification methods are less well defined since they lack standardisation.

OBJECTIVE

A seminested fluorometric PCR assay (AmpliSensor-CMV, BAG, Germany) and a one-step PCR with a signal-amplification step (SHARP, Abbott, Germany) specific for the fragments of the CMV UL 122 and UL 123 genes, respectively, were evaluated for the early diagnosis of CMV infection.

DESIGN

A total of 26 recipients of heterogeneous solid organs were monitored prospectively for a median of 99 days after transplantation. By testing 371 clinical samples parallel with the pp65-antigen assay and IgM and IgG EIA assays the sensitivity, specificity, correlation and quantitation potential of both PCRs was evaluated.

RESULTS

Eight out of 26 patients developed active CMV infection. A total of 48 samples of these patients exceeded a CMV-DNA load threshold of 15 genome equivalents/10(5) leukocytes (AmpliSensor-CMV) and 41 samples exceeded the critical cut-off for the SHARP system. The AmpliSensor PCR exceeded its threshold consistently before the clinical onset of CMV disease (median 8 days). There was very good agreement between symptomatic CMV infection in patients and AmpliSensor-PCR, SHARP PCR, and pp65-antigen results (kappa-coefficient > 0.900). IgM and IgG EIA showed moderate agreement (kappa-coefficient = 0.591 and 0.552, respectively).

CONCLUSION

Both PCRs and pp65 antigen assay correlated significantly better with CMV disease than serodiagnosis. The AmpliSensor PCR allowed more precisely than the SHARP system a quantitative determination of viral load and an early and reliable prediction of active CMV infection. The use of AmpliSensor PCR may improve the diagnosis and management of active CMV infection in organ transplant recipients.

[Results of pacing after acute myocardial infarction (author's transl)]

Indications for electrical pacing were present in 58 of 665 patients with acute myocardial infarction (8.7%). Posterior-wall infarction had occurred in 34, anterior-wall infarction in 20, while two had combined infarction and in a further two precise localisation was not possible. There were 16 deaths (27.6%), six of them with posterior-wall and nine with anterior-wall infarction. Bradycardic arrhythmias with A-V block predominated among posterior-wall infarctions, hemiblocks and bifascicular block in anterior-wall infarctions. Permanent pacing was practised in 14 patients, 11 with posterior and three with anterior-wall infarctions, i.e. permanent pacing was four times as common after posterior than anterior-wall infarctions, the proportion being 2:1 for temporary pacing, largely due to a higher mortality-rate after anterior-wall infarction. Old anterior-wall scars were present in nine of eleven patients with permanent pacing. Because of the danger of late bradycardia or A-V block patients with posterior-wall infarction should be carefully followed in the late phase (from about the third week onwards), especially if it is known that they have an old anterior-wall infarct.