Reported mortality of hospitalised Coronavirus Disease-2019 (COVID-19) patients varies substantially, particularly in critically ill patients. So far COVID-19 in-hospital mortality and modes of death ...under state of the art care have not been systematically studied.
This retrospective observational monocenter cohort study was performed after implementation of a non-restricted, dynamic tertiary care model at the University Medical Center Freiburg, an experienced acute respiratory distress syndrome (ARDS) and extracorporeal membrane-oxygenation (ECMO) referral center. All hospitalised patients with PCR-confirmed SARS-CoV-2 infection were included. The primary endpoint was in-hospital mortality, secondary endpoints included major complications and modes of death. A multistate analysis and a Cox regression analysis for competing risk models were performed. Modes of death were determined by two independent reviewers.
Between February 25, and May 8, 213 patients were included in the analysis. The median age was 65 years, 129 patients (61%) were male. 70 patients (33%) were admitted to the intensive care unit (ICU), of which 57 patients (81%) received mechanical ventilation and 23 patients (33%) ECMO support. Using multistate methodology, the estimated probability to die within 90 days after COVID-19 onset was 24% in the whole cohort. If the levels of care at time of study entry were accounted for, the probabilities to die were 16% if the patient was initially on a regular ward, 47% if in the intensive care unit (ICU) and 57% if mechanical ventilation was required at study entry. Age ≥65 years and male sex were predictors for in-hospital death. Predominant complications-as judged by two independent reviewers-determining modes of death were multi-organ failure, septic shock and thromboembolic and hemorrhagic complications.
In a dynamic care model COVID-19-related in-hospital mortality remained very high. In the absence of potent antiviral agents, strategies to alleviate or prevent the identified complications should be investigated. In this context, multistate analyses enable comparison of models-of-care and treatment strategies and allow estimation and allocation of health care resources.
Owing to increasing resistance and the limited arsenal of new antibiotics, especially against Gram-negative pathogens, carefully designed antibiotic regimens are obligatory for febrile neutropenic ...patients, along with effective infection control. The Expert Group of the 4(th) European Conference on Infections in Leukemia has developed guidelines for initial empirical therapy in febrile neutropenic patients, based on: i) the local resistance epidemiology; and ii) the patient's risk factors for resistant bacteria and for a complicated clinical course. An 'escalation' approach, avoiding empirical carbapenems and combinations, should be employed in patients without particular risk factors. A 'de-escalation' approach, with initial broad-spectrum antibiotics or combinations, should be used only in those patients with: i) known prior colonization or infection with resistant pathogens; or ii) complicated presentation; or iii) in centers where resistant pathogens are prevalent at the onset of febrile neutropenia. In the latter case, infection control and antibiotic stewardship also need urgent review. Modification of the initial regimen at 72-96 h should be based on the patient's clinical course and the microbiological results. Discontinuation of antibiotics after 72 h or later should be considered in neutropenic patients with fever of unknown origin who are hemodynamically stable since presentation and afebrile for at least 48 h, irrespective of neutrophil count and expected duration of neutropenia. This strategy aims to minimize the collateral damage associated with antibiotic overuse, and the further selection of resistance.
A major contribution of the resistance-nodulation-cell division (RND)-transporter AcrB to resistance to oxazolidinones and pleuromutilin derivatives in
was confirmed. However, we discovered ...significant differences in efflux inhibitor activities, specificities of the homologous pump YhiV (MdtF), and the impact of AcrB pathway mutations. Particularly, entrance channel double-mutation I38F I671T and distal binding pocket mutation F615A revealed class-specific transport routes of oxazolidinones and pleuromutilin derivatives. The findings could contribute to the understanding of the RND-type multidrug transport pathways.
Staphylococcus aureus is among the leading causes of community-acquired as well as healthcare-associated and hospital-acquired bacteremia and endocarditis. The purpose of this review was to analyze ...most recent data relevant to the clinical management of S. aureus bacteremia (SAB) and endocarditis.
Population-based studies have shown that the incidence of SAB has not decreased in the last years and that healthcare-associated and nosocomial cases continue to account for at least half of SAB. In some areas where methicillin-resistant S. aureus (MRSA) now has become common, MRSA strains with reduced vancomycin susceptibility may have emerged and account for a significant proportion. These strains increase the likelihood of treatment failures, though overall outcomes may often be similarly poor in drug-susceptible S. aureus, which must not be neglected as a pathogen causing potentially lethal infection. Many aspects of drug therapy such as continuous versus intermittent infusion of antibiotics or combination therapy continue to be discussed controversially. Few major progresses in the clinical management have been made in the last few years, but there is evidence that the case fatality can be modestly reduced by efforts focussed on sustained high-quality clinical management.
SAB remains a serious, potentially lethal infection, which is too often nosocomial and healthcare-associated. A threat has been the increasing drug resistance of S. aureus seen in many parts of the world and spreading among community isolates. Improved outcomes with new drugs have not been shown convincingly. Large clinical trials assessing the benefits of combination therapies are needed.
Summary
It is more than two decades ago that a European Union conference on “The Microbial Threat” hosted by the Danish Government in Copenhagen in September 1998 issued recommendations to encourage ...good practice in the use of antimicrobial agents and reduce inappropriate prescribing. Essential components of those recommendations were antimicrobial teams in hospitals and the use of feedback to prescribers as well as educational activities. Two decades later, important surveillance systems on both antimicrobial resistance as well as on antibiotic consumption are functioning at the European level and in most European countries; European Committee on Antimicrobial Susceptibility Testing (EUCAST) has thoroughly re-evaluated, standardized and harmonized antibiotic susceptibility testing and breakpoints; there have been educational activities in many countries; and stewardship teams are now included in many guidelines and policy papers and recommendations. Yet, antimicrobial resistance problems in Europe have shifted from methicillin-resistant
Staphylococus aureus
(MRSA) to vancomycin-resistent
Enterococcus faecium
(VRE) and to multidrug-resistant gramnegative bacteria, while antibiotic consumption volumes, trends and patterns across countries do not show major and highly significant improvements. The way to go further is to recognize that better prescribing comes at a cost and requires investment in expert personnel, practice guideline drafting, and implementation aids, and, secondly, the setting of clear goals and quantitative targets for prescribing quality.
Efflux pumps of the resistance nodulation cell division (RND) transporter family, such as AcrB of Escherichia coli, play an important role in the development of multidrug resistance, but the ...molecular basis for their substrate promiscuity is not yet completely understood. From a collection of highly clarithromycin-resistant AcrB periplasmic domain mutants derived from in vitro random mutagenesis, we identified variants with an unusually altered drug resistance pattern characterized by increased susceptibility to many drugs of lower molecular weight, including fluoroquinolones, tetracyclines, and oxazolidinones, but unchanged or increased resistance to drugs of higher molecular weight, including macrolides. Sequencing of 14 such "divergent resistance" phenotype mutants and 15 control mutants showed that this unusual phenotype was associated with mutations at residues I38 and I671 predominantly to phenylalanine and threonine, respectively, both conferring a similar susceptibility pattern. Reconstructed I38F and I671T single mutants as well as an engineered I38F I671T double mutant with proved efflux competence revealed an equivalent phenotype with enhanced or unchanged resistance to many large AcrB substrates but increased susceptibility to several lower-molecular-weight drugs known to bind within the distal binding pocket. The two isoleucines located in close vicinity to each other in the lower porter domain of AcrB beneath the bottom of the proximal binding pocket may be part of a preferential small-drug entrance pathway that is compromised by the mutations. This finding supports recent indications of distinct entrance channels used by compounds with different physicochemical properties, of which molecular size appears to play a prominent role.
Efflux by resistance nodulation cell division transporters, such as AcrAB-TolC in
, substantially contributes to the development of Gram-negative multidrug resistance. Therefore, the finding of ...compounds that counteract efflux is an urgent goal in the fight against infectious diseases. Previously, an efflux inhibitory activity of the antimalarials mefloquine and artesunate was reported. In this study, we have investigated further antimalarials regarding efflux by AcrB, the pumping part of AcrAB-TolC, and their drug-enhancing potency in
. We show that 10 of the 24 drugs tested are substrates of the multidrug efflux pump AcrB. Among them, tafenoquine and proguanil, when used at subinhibitory concentrations, caused an at least 4- and up to 24-fold enhancement in susceptibility to 6 and 14 antimicrobial agents, respectively. Both antimalarials are able to increase the intracellular accumulation of Hoechst 33342, with proguanil showing similar effectiveness as the efflux inhibitor 1-(1-naphthylmethyl)piperazine. In the case of proguanil, AcrB-dependent efflux inhibition could also be demonstrated in a real-time efflux assay. In addition to presenting new AcrB substrates, our study reveals two previously unknown efflux inhibitors among antimalarials. Particularly proguanil appears as a promising candidate and its chemical scaffold might be further optimized for repurposing as antimicrobial drug enhancer.
Background. Recent population-based cohort studies have questioned the role of pneumococci as the most frequent pathogen causing severe infection in patients after splenectomy. The aim of the study ...was to define the causative pathogens and clinical presentation of patients with overwhelming postsplenectomy infection (OPSI). Methods. In a prospective cohort study in 173 German intensive care units, we searched for patients with and without asplenia and community-acquired severe sepsis/septic shock. Clinical and laboratory variables and survival of patients were assessed. Results. Fifty-two patients with severe sepsis or septic shock with asplenia and 52 without asplenia were included. OPSI patients more often had a history of malignancy (38% vs 17%; P= 0.16) and had a lower body mass index (24 kg/m2 vs 28 kg/m2; P= .004). Streptococcus pneumoniae was detected more frequently in OPSI patients (42% vs 12% without asplenia; P< .001) and more frequently manifested as bloodstream infection (31% vs 6%; P= .002). Gram-negative infection was similar in both groups (12% vs 19%; P = .157). Pneumococcal vaccine coverage of OPSI patients was low overall (42% vs 8% among patients without asplenia; P < .001). Purpura fulminans was a frequent complication, developing in 19% of OPSI patients vs 5% of patients without asplenia (P = .038). The interval between splenectomy and OPSI was 6 years (range, 1 month-50 years). On multivariable Poisson regression, asplenia was the only predictive variable independently associated with pneumococcal sepsis (adjusted relative risk, 2.53 95% confidence interval, 1.06-6.08). Conclusions. Pneumococcal infections remain the most important cause of severe sepsis and septic shock following splenectomy.
AcrAB-TolC is the major efflux protein complex in Escherichia coli extruding a vast variety of antimicrobial agents from the cell. The inner membrane component AcrB is a homotrimer, and it has been ...postulated that the monomers cycle consecutively through three conformational stages designated loose (L), tight (T), and open (O) in a concerted fashion. Binding of drugs has been shown at a periplasmic deep binding pocket in the T conformation. The initial drug-binding step and transport toward this drug-binding site has been elusive thus far. Here we report high resolution structures (1.9–2.25 Å) of AcrB/designed ankyrin repeat protein (DARPin) complexes with bound minocycline or doxorubicin. In the AcrB/doxorubicin cocrystal structure, binding of three doxorubicin molecules is apparent, with one doxorubicin molecule bound in the deep binding pocket of the T monomer and two doxorubicin molecules in a stacked sandwich arrangement in an access pocket at the lateral periplasmic cleft of the L monomer. This access pocket is separated from the deep binding pocket apparent in the T monomer by a switch-loop. The localization and conformational flexibility of this loop seems to be important for large substrates, because a G616N AcrB variant deficient in macrolide transport exhibits an altered conformation within this loop region. Transport seems to be a stepwise process of initial drug uptake in the access pocket of the L monomer and subsequent accommodation of the drug in the deep binding pocket during the L to T transition to the internal deep binding pocket of the T monomer.
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