Staphylococcus aureus bacteriuria: implications and management.

Background: Staphylococcus aureus is isolated in around 0.2%-4% of positive urinary cultures, more commonly in the contexts of long-term care, urological abnormalities and procedures, male sex, older age and comorbidities. Isolation may represent contamination, colonization, urinary tract infection or bacteraemic seeding from another site, and may be linked to S. aureus bacteraemia. However, there is little guidance on investigation and management of S. aureus bacteriuria. We performed a retrospective analysis of cases in our service, including clinical characteristics, investigations and treatment. Methods: Data were collected on all urine samples taken from adult patients over a 5-year period from which S. aureus was isolated. Detailed analysis including investigations and management was conducted in those collected over a 1-year period. Results: From 511 patients, 668 urine cultures positive for S. aureus were identified; 6.5% of cases were positive for MRSA. Of 93 patients who had blood cultures taken, there were 6 cases of S. aureus bacteraemia, 4 of which were associated with urological instrumentation. Of 94 cases analysed in detail, 57% were treated with antibiotics, and 49% had repeat urine cultures. Factors associated with recurrence were urinary catheterization, urological abnormality, diabetes and inpatient status. Conclusions: Our experience does not support the routine taking of blood cultures or treatment of asymptomatic bacteriuria in well patients with S. aureus bacteriuria in this setting. However, repeat urine culture, and investigation and treatment of higher risk patients, for example, prior to bladder instrumentation, may be warranted. We propose a simple algorithm to guide clinicians.

Gut Commensal Bacteroidetes Encode a Novel Class of Vitamin B12-Binding Proteins.

Human gut commensal Bacteroidetes rely on multiple transport systems to acquire vitamin B12 and related cobamides for fitness in the gut. In addition to a set of conserved transport proteins, these systems also include a diverse repertoire of additional proteins with unknown function. Here, we report the function and structural characterization of one of these proteins, BtuH, which binds vitamin B12 directly via a C-terminal globular domain that has no known structural homologs. This protein is required for efficient B12 transport and competitive fitness in the gut, demonstrating that members of the heterogeneous suite of accessory proteins encoded in Bacteroides cobamide transport system loci can play key roles in vitamin acquisition. IMPORTANCE The gut microbiome is a complex microbial community with important impacts on human health. One of the major groups within the gut microbiome, the Bacteroidetes, rely on their ability to capture vitamin B12 and related molecules for fitness in the gut. Unlike well-studied model organisms, gut Bacteroidetes genomes often include multiple vitamin B12 transport systems with a heterogeneous set of components. The role, if any, of these components was unknown. Here, we identify new proteins that play key roles in vitamin B12 capture in these organisms. Notably, these proteins are associated with some B12 transport systems and not others (even in the same bacterial strain), suggesting that these systems may assemble into functionally distinct machines to capture vitamin B12 and related molecules.

Development and internal validation of clinical prediction models for outcomes of complicated intra-abdominal infection.

BACKGROUND: Complicated intra-abdominal infections (cIAIs) are associated with significant morbidity and mortality. The aim of this study was to describe the clinical characteristics of patients with cIAI in a multicentre study and to develop clinical prediction models (CPMs) to help identify patients at risk of mortality or relapse. METHODS: A multicentre observational study was conducted from August 2016 to February 2017 in the UK. Adult patients diagnosed with cIAI were included. Multivariable logistic regression was performed to develop CPMs for mortality and cIAI relapse. The c-statistic was used to test model discrimination. Model calibration was tested using calibration slopes and calibration in the large (CITL). The CPMs were then presented as point scoring systems and validated further. RESULTS: Overall, 417 patients from 31 surgical centres were included in the analysis. At 90 days after diagnosis, 17.3 per cent had a cIAI relapse and the mortality rate was 11.3 per cent. Predictors in the mortality model were age, cIAI aetiology, presence of a perforated viscus and source control procedure. Predictors of cIAI relapse included the presence of collections, outcome of initial management, and duration of antibiotic treatment. The c-statistic adjusted for model optimism was 0.79 (95 per cent c.i. 0.75 to 0.87) and 0.74 (0.73 to 0.85) for mortality and cIAI relapse CPMs. Adjusted calibration slopes were 0.88 (95 per cent c.i. 0.76 to 0.90) for the mortality model and 0.91 (0.88 to 0.94) for the relapse model; CITL was -0.19 (95 per cent c.i. -0.39 to -0.12) and - 0.01 (- 0.17 to -0.03) respectively. CONCLUSION: Relapse of infection and death after complicated intra-abdominal infections are common. Clinical prediction models were developed to identify patients at increased risk of relapse or death after treatment, these now require external validation.

Imaging in the investigation and management of Staphylococcus aureus bacteraemia: a role for advanced imaging techniques.

Staphylococcus aureus bacteraemia (SAB) continues to affect ∼25,000 patients in the UK per year with a high crude mortality of 30% at 90 days. Prompt source control improves outcomes in sepsis and SAB and is included in sepsis guidelines. A recent clinical trial of adjunctive antibiotic treatment in SAB found that the majority of recurrences of SAB were associated with a failure of source management. In this condition, the ability to control the source of infection may be limited by the ability to detect a focus of infection. Echocardiogram is now a routinely used tool to detect such unknown foci in the form of unexpected infectious vegetations. We review the literature to explore the utility of advanced imaging techniques, such as [18F]fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and magnetic resonance imaging (including whole-body MRI), to detect foci which may otherwise be missed. As unknown foci are associated with increased mortality, we propose that increasing the detection of foci could enable improved source control and result in improved outcomes in SAB.

A Screen for Antibiotic Resistance Determinants Reveals a Fitness Cost of the Flagellum in Pseudomonas aeruginosa.

The intrinsic resistance of Pseudomonas aeruginosa to many antibiotics limits treatment options for pseudomonal infections. P. aeruginosa's outer membrane is highly impermeable and decreases antibiotic entry into the cell. We used an unbiased high-throughput approach to examine mechanisms underlying outer membrane-mediated antibiotic exclusion. Insertion sequencing (INSeq) identified genes that altered fitness in the presence of linezolid, rifampin, and vancomycin, antibiotics to which P. aeruginosa is intrinsically resistant. We reasoned that resistance to at least one of these antibiotics would depend on outer membrane barrier function, as previously demonstrated in Escherichia coli and Vibrio cholerae This approach demonstrated a critical role of the outer membrane barrier in vancomycin fitness, while efflux pumps were primary contributors to fitness in the presence of linezolid and rifampin. Disruption of flagellar assembly or function was sufficient to confer a fitness advantage to bacteria exposed to vancomycin. These findings clearly show that loss of flagellar function alone can confer a fitness advantage in the presence of an antibiotic.IMPORTANCE The cell envelopes of Gram-negative bacteria render them intrinsically resistant to many classes of antibiotics. We used insertion sequencing to identify genes whose disruption altered the fitness of a highly antibiotic-resistant pathogen, Pseudomonas aeruginosa, in the presence of antibiotics usually excluded by the cell envelope. This screen identified gene products involved in outer membrane biogenesis and homeostasis, respiration, and efflux as important contributors to fitness. An unanticipated fitness cost of flagellar assembly and function in the presence of the glycopeptide antibiotic vancomycin was further characterized. These findings have clinical relevance for individuals with cystic fibrosis who are infected with P. aeruginosa and undergo treatment with vancomycin for a concurrent Staphylococcus aureus infection.

Translocation of a gut pathobiont drives autoimmunity in mice and humans.

Despite multiple associations between the microbiota and immune diseases, their role in autoimmunity is poorly understood. We found that translocation of a gut pathobiont, Enterococcus gallinarum, to the liver and other systemic tissues triggers autoimmune responses in a genetic background predisposing to autoimmunity. Antibiotic treatment prevented mortality in this model, suppressed growth of E. gallinarum in tissues, and eliminated pathogenic autoantibodies and T cells. Hepatocyte-E. gallinarum cocultures induced autoimmune-promoting factors. Pathobiont translocation in monocolonized and autoimmune-prone mice induced autoantibodies and caused mortality, which could be prevented by an intramuscular vaccine targeting the pathobiont. E. gallinarum-specific DNA was recovered from liver biopsies of autoimmune patients, and cocultures with human hepatocytes replicated the murine findings; hence, similar processes apparently occur in susceptible humans. These discoveries show that a gut pathobiont can translocate and promote autoimmunity in genetically predisposed hosts.

Does gender or mode of HIV acquisition affect virological response to modern antiretroviral therapy (ART)?

OBJECTIVES: Previous UK studies have reported disparities in HIV treatment outcomes for women. We investigated whether these differences persist in the modern antiretroviral treatment (ART) era. METHODS: A single-centre cohort analysis was carried out. We included in the study all previously ART-naïve individuals at our clinic starting triple ART from 1 January 2006 onwards with at least one follow-up viral load (VL). Time to viral suppression (VS; first viral load < 50 HIV-1 RNA copies/mL), virological failure (VF; first of two consecutive VLs > 200 copies/mL more than 6 months post-ART) and treatment modification were estimated using standard survival methods. RESULTS: Of 1086 individuals, 563 (52%) were men whose risk for HIV acquisition was sex with other men (MSM), 207 (19%) were men whose risk for HIV acquisition was sex with women (MSW) and 316 (29%) were women. Median pre-ART CD4 count and time since HIV diagnosis in these groups were 298, 215 and 219 cells/µL, and 2.3, 0.3 and 0.3 years, respectively. Time to VS was comparable between groups, but women [adjusted hazard ratio (aHR) 2.32; 95% confidence interval (CI) 1.28-4.22] and MSW (aHR 3.28; 95% CI 1.91-5.64) were at considerably higher risk of VF than MSM. Treatment switches and complete discontinuation were also more common among MSW [aHR 1.38 (95% CI 1.04-1.81) and aHR 1.73 (95% CI 0.97-3.16), respectively] and women [aHR 1.87 (95% CI 1.43-2.46) and aHR 3.20 (95% CI 2.03-5.03), respectively] than MSM. CONCLUSIONS: Although response rates were good in all groups, poorer virological outcomes for women and MSW have persisted into the modern ART era. Factors that might influence the differences include socioeconomic status and mental health disorders. Further interventions to ensure excellent response rates in women and MSW are required.

Comparative assessment of transmission-blocking vaccine candidates against Plasmodium falciparum.

Malaria transmission-blocking vaccines (TBVs) target the development of Plasmodium parasites within the mosquito, with the aim of preventing malaria transmission from one infected individual to another. Different vaccine platforms, mainly protein-in-adjuvant formulations delivering the leading candidate antigens, have been developed independently and have reported varied transmission-blocking activities (TBA). Here, recombinant chimpanzee adenovirus 63, ChAd63, and modified vaccinia virus Ankara, MVA, expressing AgAPN1, Pfs230-C, Pfs25, and Pfs48/45 were generated. Antibody responses primed individually against all antigens by ChAd63 immunization in BALB/c mice were boosted by the administration of MVA expressing the same antigen. These antibodies exhibited a hierarchy of inhibitory activity against the NF54 laboratory strain of P. falciparum in Anopheles stephensi mosquitoes using the standard membrane feeding assay (SMFA), with anti-Pfs230-C and anti-Pfs25 antibodies giving complete blockade. The observed rank order of inhibition was replicated against P. falciparum African field isolates in A. gambiae in direct membrane feeding assays (DMFA). TBA achieved was IgG concentration dependent. This study provides the first head-to-head comparative analysis of leading antigens using two different parasite sources in two different vector species, and can be used to guide selection of TBVs for future clinical development using the viral-vectored delivery platform.

Gut microbiota. Antimicrobial peptide resistance mediates resilience of prominent gut commensals during inflammation.

Resilience to host inflammation and other perturbations is a fundamental property of gut microbial communities, yet the underlying mechanisms are not well understood. We have found that human gut microbes from all dominant phyla are resistant to high levels of inflammation-associated antimicrobial peptides (AMPs) and have identified a mechanism for lipopolysaccharide (LPS) modification in the phylum Bacteroidetes that increases AMP resistance by four orders of magnitude. Bacteroides thetaiotaomicron mutants that fail to remove a single phosphate group from their LPS were displaced from the microbiota during inflammation triggered by pathogen infection. These findings establish a mechanism that determines the stability of prominent members of a healthy microbiota during perturbation.

CMV in the gut: a critical review of CMV detection in the immunocompetent host with colitis.

As scientific techniques for the detection of cytomegalovirus (CMV) improve, we are able to detect small amounts of CMV in the mucosal wall. As clinicians, we are unsure how to interpret the results of this novel test. There is controversy in the literature as to the significance of the detection of CMV in the gut. Whilst the importance of CMV and reactivation of the virus is clear in those patients such as allograft recipients with established immune compromise, the role is less clear in patients with less damaged immune systems. We explore whether the detection of CMV in such cases influences outcome and how it should be optimally managed. We discuss the optimal management of such cases, according to current guidelines, with a review of the literature.

Blood-stage malaria vaccines - recent progress and future challenges.

Plasmodium falciparum malaria is a major global health problem, responsible for up to 1 million deaths each year. Major efforts have been made to develop an effective vaccine against this disease, to reduce the associated morbidity and mortality. There has already been considerable progress, with the first vaccine against the pre-erythrocytic stages of P. falciparum now en route to licensure. There remains, however, a strong scientific rationale for the development of a highly effective additional vaccine component against the blood stages of the parasite, which could be deployed in conjunction with partially effective control measures against the pre-erythrocytic stages. Here, recent progress in the clinical development of blood-stage vaccines is reviewed, including methods of antigen selection, the limitations of in-vitro assays for selecting vaccines for clinical development, and the results of recently published clinical trials. This review seeks to summarize recent developments in our understanding of immunity to blood-stage parasites, as well as the relevant key advances made in vaccine technologies over the last decade. The future challenges that face this field of vaccine research are also described.

Disparate actions of mifepristone (RU 486) on glands and stroma in the primate endometrium.

Besides being an antiprogestin, mifepristone (RU 486) was recently shown to antagonize oestrogen-dependent growth in the endometrium. To explore the molecular mechanisms for this phenomenon, we investigated whether or not the morphological effects of mifepristone are mediated by the progesterone receptor (PR) and whether mifepristone has disparate effects on the glandular epithelium and stroma. Six groups of hypogonadal, oestrogen-primed cynomolgus monkeys were treated for 2 weeks with: vehicle only (group I); mifepristone (group II); mifepristone plus progesterone at 0.2 mg/kg (group III), 1.0 mg/kg (group IV) or 5.0 mg/kg (group V); and progesterone only (5.0 mg/kg) (group VI). Histomorphological evaluation showed strikingly compacted stroma in the mifepristone-exposed endometria (group II), which was partially reversible by additional progesterone treatment (groups III-V). Glandular proliferation (pseudostratification, glandular mitoses) in mifepristone-treated monkeys was not significantly different from that in vehicle (oestradiol)-treated monkeys, but was inhibited by progesterone-only treatment. Cells containing vacuoles were scarce in the mifepristone-exposed endometrium, but detected frequently in progesterone-exposed endometria, indicating the strong antisecretory effect of mifepristone on glands. We conclude that oestrogen-dependent oedema in the stroma is antagonized by mifepristone. The reversal of this effect by progesterone suggests a PR-mediated mechanism. In glands, mifepristone is antiprogestogenic, but not antioestrogenic. Thus, stromal cells may be the target of antiprogestin-induced inhibition of oedema and endometrial growth.

Vascular endothelial growth factor in primate endometrium is regulated by oestrogen-receptor and progesterone-receptor ligands in vivo.

We investigated hormonal regulation of endometrial angiogenesis in menstruating primates. This study was designed to demonstrate: (i) that cell-specific vascular endothelial growth factor (VEGF) production and expression in monkey endometrium are regulated by steroid receptor ligands; and (ii) mifepristone (RU 486) alters VEGF production even in the absence of a progestin agonist. Endometrial VEGF production was compared by computer-assisted immunohistochemical analysis during induced hypoestrogenism and after oestradiol, progestin, or antiprogestin (mifepristone) treatment. VEGF gene expression was estimated by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR) in endometrial samples from castrate cynomolgus monkeys, from intact monkeys in the luteal phase, and from monkeys treated for 20 days with levonorgestrel (LNG) or mifepristone. VEGF staining intensities in glandular epithelium and VEGF mRNA expression were highest in hypoestrogenic monkeys. Progestin treatment induced intense VEGF staining in the stroma. Gene expression of VEGF-189, but not other isoforms, was higher in progesterone- and progestin (LNG)-exposed endometria compared to mifepristone-exposed endometria or endometria from anovulatory cycles (P < 0.04). Mifepristone abolished VEGF staining in glandular epithelium almost completely. We conclude that VEGF protein and VEGF mRNA expression levels in primate endometrium depend on the steroidal milieu. Anti-angiogenic effects of mifepristone via suppression of VEGF production might represent a mechanism for its quelling effects on endometrium.

GnRH antagonists and antiprogestins: novel contraceptive options.

PIP: Gonadotropin releasing hormone (GnRH) antagonists prevent endogenous GnRH from binding to and activating its receptor-mediated signal transduction pathway. Specifically, they inhibit pituitary gonadotropin production, which in turn immediately suppresses luteinizing hormone/follicle stimulating hormone secretion. GnRH antagonists suppress testosterone secretion and produce azoospermia in nonhuman primates, but also cause loss of libido and impotence. When testosterone (e.g., 25 mg testosterone enanthate) is replaced after GnRH antagonist treatment begins, azoospermia is still achieved without affecting libido. A GnRH antagonist administered by nasal spray in postpartum Marmoset monkeys was effective at preventing pregnancy. The GnRH antagonist found in the breast milk was not bioactive in the infants, probably because it is broken down in the infant gut. GnRH antagonists may help women with a family history of breast cancer or other medical contraindications to oral contraceptives. Antiprogestins prevent pregnancy by blocking ovulation and by suppressing implantation. The evidence suggests that antiprogestins interrupt or delay endometrial maturation. The antiprogestin RU-486 has been used as a postcoital contraceptive agent. Preliminary evidence shows that both GnRH antagonists and antiprogestins may someday be added to the mix of contraceptive offerings.^ieng

Ovarian angiogenesis in rabbits: endotheliotrophic chemoattractant activity from isolated follicles and dispersed granulosa cells.

To test the hypothesis that angiogenesis is an important variable in ovarian folliculogenesis, we measured endothelial cell migration (chemotaxis) in media conditioned by rabbit ovarian cells. Endothelial cell migration, a reliable predictor of angiogenesis in vivo, was stimulated by media conditioned by isolated intact follicles (0.4-2.2 mm in diameter) from either unstimulated or hCG-stimulated (pseudopregnant) rabbits. In separate experiments, endothelial cell migration was also stimulated by granulosa cell-conditioned media. Follicular chemoattractant activity was associated with a molecular weight greater than 30,000 but was not correlated with follicular size or steroid concentrations in the media, although there was no evidence to suggest that the biological activity detected in media conditioned by either intact follicles or dispersed granulosa cells was the same. Demonstration of nonsteroidal chemoattractant activity in media conditioned by intact follicles or by dispersed granulosa cells provides evidence that follicles secrete a vascular chemotactic factor, and is consistent with a role for angiogenesis in follicle growth.

Evidence for the production of a nonsteroidal endotheliotropic factor by human granulosa cells in culture.

OBJECTIVE: To determine the cellular source of the angiogenic activity displayed by follicular fluid (FF). DESIGN: Human granulosa cells were harvested from 27 follicular aspirates obtained 34 to 36 hours after eight patients, previously treated with human menopausal gonadotropin (hMG), follicle-stimulating hormone plus hMG, or clomiphene citrate and hMG received human chorionic gonadotropin (10,000 IU intramuscularly). Granulosa cells from individual follicles were plated at 50,000 cells/cm2 in Medium 199 (Sigma, St. Louis, MO) supplemented with either 5% calf serum or 0.1% bovine serum albumin; media collected 24 hours later was assayed in vitro measuring endothelial cell migration. Fractions depleted of steroids by reversed phase C1 chromatography were assayed as well. RESULTS: Granulosa cell-conditioned media from 18 of 27 follicles significantly stimulated endothelial cell migration (P less than 0.05). Chemoattractant activity did not appear to be related to steroid accumulation in the media and was not diminished in steroid depleted fractions. CONCLUSIONS: These findings suggest that human granulosa cells are a source of (nonsteroidal) endotheliotropic-angiogenic activity in FF.

Use of the levator scapulae muscle flap in head and neck reconstruction.

There are numerous techniques available for reconstruction of defects following composite resection of oral cavity and oropharyngeal tumors. No single technique is applicable in all situations. The levator scapulae muscle flap is well known for its application in carotid protection. Little attention is paid to its usefulness in other aspects of head and neck reconstruction. We have been using the levator scapulae muscle flap for a variety of reconstructive problems. The flap is useful for buttressing intraoral suture lines, closing intraoral defects, and providing soft tissue to fill in dead spaces and bulk out lateral and anterior oral defects. The levator flap was found to be easy to elevate, safe, and reliable with a minimum of wound complications. A review of 18 patients, representative case studies, and a discussion of surgical technique and relevant anatomy and blood supply is presented.