Active and Passive Immunization Protects against Lethal, Extreme Drug Resistant-Acinetobacter baumannii Infection

Extreme-drug-resistant (XDR) Acinetobacter baumannii is a rapidly emerging pathogen causing infections with unacceptably high mortality rates due to inadequate available treatment. New methods to prevent and treat such infections are a critical unmet medical need. To conduct a rational vaccine discovery program, OmpA was identified as the primary target of humoral immune response after intravenous infection by A. baumannii in mice. OmpA was >99% conserved at the amino acid level across clinical isolates harvested between 1951 and 2009 from cerebrospinal fluid, blood, lung, and wound infections, including carbapenem-resistant isolates, and was ≥89% conserved among other sequenced strains, but had minimal homology to the human proteome. Vaccination of diabetic mice with recombinant OmpA (rOmpA) with aluminum hydroxide adjuvant markedly improved survival and reduced tissue bacterial burden in mice infected intravenously. Vaccination induced high titers of anti-OmpA antibodies, the levels of which correlated with survival in mice. Passive transfer with immune sera recapitulated protection. Immune sera did not enhance complement-mediated killing but did enhance opsonophagocytic killing of A. baumannii. These results define active and passive immunization strategies to prevent and treat highly lethal, XDR A. baumannii infections

Phage therapy efficacy: a review of the last 10 years of preclinical studies

Due to the rise of multidrug-resistant infections in humans, phage therapy is gaining renewed attention in Western medicine. Despite the increasing number of publications focussed on the isolation, characterization and in vitro performance of different phages, there is still a lack of concise pre-clinical information to guide the application of phage therapy in clinical practice. Nevertheless, over the last decade, efforts have been made to conduct more detailed studies of the in vivo efficacy of phages. Here, we review the most relevant in vivo studies performed in the last decade covering phage efficacy in both preclinical and clinical trials. We compare different routes of administration, dosage effect and different animal models of distinct types of infections. Moreover, insights into case studies and results from clinical trials are presented. Challenges and limitations of phage use as evidenced by the current state of research are also discussed in order to improve both the trustworthiness and success of the implementation of phage therapy.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 [POCI-01-0145-FEDER-006684] and Projects PTDC/SAU-PUB/29182/2017 [POCI-01-0145-FEDER-029182] and PTDC/CVTCVT/29628/2017 [POCI-01-0145-FEDER-029628]. This work was also supported by BioTecNorte operation [NORTE-01- 0145-FEDER-000004] funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. DPP was supported by a FCT grant [SFRH/BPD/116187/2016]. KD is the recipient of the National Science Centre in Poland grant [UMO-2018/29/B/NZ6/01659]. The funding bodies had no role in study design, data collection and analysis, preparation of the manuscript, or the decision to publish.info:eu-repo/semantics/publishedVersio

The antimicrobial polymer PHMB enters cells and selectively condenses bacterial chromosomes

To combat infection and antimicrobial resistance, it is helpful to elucidate drug mechanism(s) of action. Here we examined how the widely used antimicrobial polyhexamethylene biguanide (PHMB) kills bacteria selectively over host cells. Contrary to the accepted model of microbial membrane disruption by PHMB, we observed cell entry into a range of bacterial species, and treated bacteria displayed cell division arrest and chromosome condensation, suggesting DNA binding as an alternative antimicrobial mechanism. A DNA-level mechanism was confirmed by observations that PHMB formed nanoparticles when mixed with isolated bacterial chromosomal DNA and its effects on growth were suppressed by pairwise combination with the DNA binding ligand Hoechst 33258. PHMB also entered mammalian cells, but was trapped within endosomes and excluded from nuclei. Therefore, PHMB displays differential access to bacterial and mammalian cellular DNA and selectively binds and condenses bacterial chromosomes. Because acquired resistance to PHMB has not been reported, selective chromosome condensation provides an unanticipated paradigm for antimicrobial action that may not succumb to resistance

Non-adherence to antimicrobial treatment guidelines results in more broad-spectrum but not more appropriate therapy

Mortality in patients admitted with sepsis is high and the increasing incidence of infections with multiresistant bacteria is a worldwide problem. Many hospitals have local antimicrobial guidelines to assure effective treatment and limit the use of broad-spectrum antibiotics, thereby reducing the selection of resistant bacteria. We evaluated adherence to the antimicrobial treatment guidelines of our hospital in patients presenting to the emergency department (ED) with sepsis and assessed the in vitro susceptibility of isolated pathogens to the guideline-recommended treatment and the prescribed treatment. We included all adult patients with a known or suspected infection and two or more extended systemic inflammatory response syndrome (SIRS) criteria. Patients who did not receive antimicrobial treatment, presented with infections not included in the guidelines, or had more than one possible focus of infection were excluded. A total of 276 ED visits (262 patients) were included. Guideline-concordant treatment was prescribed in 168 visits (61%). In the case of guideline-disconcordant treatment, 87% was more broad-spectrum than guideline-recommended treatment. A microbiological diagnosis was established in 96 visits (35%). The susceptibility of the pathogens isolated from patients treated with guideline-concordant treatment (n = 68) and guideline-disconcordant treatment (n = 28) to guideline-recommended treatment (91% versus 89%) and to prescribed treatment (91% versus 93%) was similar (p = 0.77 and p = 0.79, respectively). In conclusion, non-adherence to the guidelines occurred frequently and resulted in more broad-spectrum empirical therapy. This did not result in a higher rate of susceptibility of the isolated pathogens to the prescribed empirical therapy

Fungal iron availability during deep seated candidiasis is defined by a complex interplay involving systemic and local events

Peer reviewedPublisher PD

Validation of the Tetracycline Regulatable Gene Expression System for the Study of the Pathogenesis of Infectious Disease

Understanding the pathogenesis of infectious disease requires the examination and successful integration of parameters related to both microbial virulence and host responses. As a practical and powerful method to control microbial gene expression, including in vivo, the tetracycline-regulatable system has recently gained the favor of many investigative groups. However, some immunomodulatory effects of the tetracyclines, including doxycycline, could potentially limit its use to evaluate host responses during infection. Here we have used a well-established murine model of disseminated candidiasis, which is highly dependent on both the virulence displayed by the fungal cells and on the host immune status, to validate the use of this system. We demonstrate that the pathogenesis of the wild type C. albicans CAF2-1 strain, which does not contain any tet-regulatable element, is not affected by the presence of doxycycline. Moreover levels of key cytokines, chemokines and many other biomarkers, as determined by multi-analyte profiling, remain essentially unaltered by the presence of the antibiotic during infection. Our results indicate that the levels of doxycycline needed to control the tetracycline regulatable promoter gene expression system have no detectable effect on global host responses during candidiasis. Because tet-regulatable systems are now being increasingly used in a variety of pathogenic microorganisms, these observations have wide implications in the field of infectious diseases

A live weight-heart girth relationship for accurate dosing of east African shorthorn zebu cattle

The accurate estimation of livestock weights is important for many aspects of livestock management including nutrition, production and appropriate dosing of pharmaceuticals. Subtherapeutic dosing has been shown to accelerate pathogen resistance which can have subsequent widespread impacts. There are a number of published models for the prediction of live weight from morphometric measurements of cattle, but many of these models use measurements difficult to gather and include complicated age, size and gender stratification. In this paper, we use data from the Infectious Diseases of East Africa calf cohort study and additional data collected at local markets in western Kenya to develop a simple model based on heart girth circumference to predict live weight of east African shorthorn zebu (SHZ) cattle. SHZ cattle are widespread throughout eastern and southern Africa and are economically important multipurpose animals. We demonstrate model accuracy by splitting the data into training and validation subsets and comparing fitted and predicted values. The final model is weight0.262 =0.95 + 0.022 × girth which has an R2 value of 0.98 and 95 % prediction intervals that fall within the ±20 % body weight error band regarded as acceptable when dosing livestock. This model provides a highly reliable and accurate method for predicting weights of SHZ cattle using a single heart girth measurement which can be easily obtained with a tape measure in the field setting

Seeking Clarity within Cloudy Effluents: Differentiating Fungal from Bacterial Peritonitis in Peritoneal Dialysis Patients

Fungal peritonitis is a serious complication of peritoneal dialysis (PD) therapy with the majority of patients ceasing PD permanently. The aims of this study were to identify risk factors and clinical associations that may discriminate between fungal from bacterial peritonitis.We retrospectively identified episodes of fungal peritonitis from 2001-2010 in PD patients at Liverpool and Westmead Hospitals (Australia). Fungal peritonitis cases were matched in a 1:2 ratio with patients with bacterial peritonitis from each institution's dialysis registry, occurring closest in time to the fungal episode. Patient demographic, clinical and outcome data were obtained from the medical records.Thirty-nine episodes of fungal peritonitis (rate of 0.02 episodes per patient-year of dialysis) were matched with 78 episodes of bacterial peritonitis. Candida species were the commonest pathogens (35/39; 90% episodes) with Candida albicans (37%), Candida parapsilosis (32%) and Candida glabrata (13%) the most frequently isolated species. Compared to bacterial peritonitis, fungal peritonitis patients had received PD for significantly longer (1133 vs. 775 catheter-days; p = 0.016), were more likely to have had previous episodes of bacterial peritonitis (51% vs. 10%; p = 0.01), and to have received prior antibacterial therapy (51% vs. 10%; p = 0.01). Patients with fungal peritonitis were less likely to have fever and abdominal pain on presentation, but had higher rates of PD catheter removal (79% vs. 22%; p<0.005), and permanent transfer to haemodialysis (87% vs. 24%; p<0.005). Hospital length of stay was significantly longer in patients with fungal peritonitis (26.1 days vs. 12.6 days; p = 0.017), but the all-cause 30-day mortality rate was similar in both groups. Fluconazole was a suitable empiric antifungal agent; with no Candida resistance detected.Prompt recognition of clinical risk factors, initiation of antifungal therapy and removal of PD catheters are key considerations in optimising outcomes

Increased Recruitment but Impaired Function of Leukocytes during Inflammation in Mouse Models of Type 1 and Type 2 Diabetes

BACKGROUND: Patients suffering from diabetes show defective bacterial clearance. This study investigates the effects of elevated plasma glucose levels during diabetes on leukocyte recruitment and function in established models of inflammation. METHODOLOGY/PRINCIPAL FINDINGS: Diabetes was induced in C57Bl/6 mice by intravenous alloxan (causing severe hyperglycemia), or by high fat diet (moderate hyperglycemia). Leukocyte recruitment was studied in anaesthetized mice using intravital microscopy of exposed cremaster muscles, where numbers of rolling, adherent and emigrated leukocytes were quantified before and during exposure to the inflammatory chemokine MIP-2 (0.5 nM). During basal conditions, prior to addition of chemokine, the adherent and emigrated leukocytes were increased in both alloxan- (62±18% and 85±21%, respectively) and high fat diet-induced (77±25% and 86±17%, respectively) diabetes compared to control mice. MIP-2 induced leukocyte emigration in all groups, albeit significantly more cells emigrated in alloxan-treated mice (15.3±1.0) compared to control (8.0±1.1) mice. Bacterial clearance was followed for 10 days after subcutaneous injection of bioluminescent S. aureus using non-invasive IVIS imaging, and the inflammatory response was assessed by Myeloperoxidase-ELISA and confocal imaging. The phagocytic ability of leukocytes was assessed using LPS-coated fluorescent beads and flow cytometry. Despite efficient leukocyte recruitment, alloxan-treated mice demonstrated an impaired ability to clear bacterial infection, which we found correlated to a 50% decreased phagocytic ability of leukocytes in diabetic mice. CONCLUSIONS/SIGNIFICANCE: These results indicate that reduced ability to clear bacterial infections observed during experimentally induced diabetes is not due to reduced leukocyte recruitment since sustained hyperglycemia results in increased levels of adherent and emigrated leukocytes in mouse models of type 1 and type 2 diabetes. Instead, decreased phagocytic ability observed for leukocytes isolated from diabetic mice might account for the impaired bacterial clearance

A systematic review and critical assessment of incentive strategies for discovery and development of novel antibiotics

Despite the growing threat of antimicrobial resistance, pharmaceutical and biotechnology firms are reluctant to develop novel antibiotics because of a host of market failures. This problem is complicated by public health goals that demand antibiotic conservation and equitable patient access. Thus, an innovative incentive strategy is needed to encourage sustainable investment in antibiotics. This systematic review consolidates, classifies and critically assesses a total of 47 proposed incentives. Given the large number of possible strategies, a decision framework is presented to assist with the selection of incentives. This framework focuses on addressing market failures that result in limited investment, public health priorities regarding antibiotic stewardship and patient access, and implementation constraints and operational realities. The flexible nature of this framework allows policy makers to tailor an antibiotic incentive package that suits a country’s health system structure and needs