Increased alcohol dehydrogenase 1 activity promotes longevity

Several molecules can extend healthspan and lifespan across organisms. However, most are upstream signaling hubs or transcription factors orchestrating complex anti-aging programs. Therefore, these molecules point to but do not reveal the fundamental mechanisms driving longevity. Instead, downstream effectors that are necessary and sufficient to promote longevity across conditions or organisms may reveal the fundamental anti-aging drivers. Toward this goal, we searched for effectors acting downstream of the transcription factor EB (TFEB), known as HLH-30 in C. elegans, because TFEB/HLH-30 is necessary across anti-aging interventions and its overexpression is sufficient to extend C. elegans lifespan and reduce biomarkers of aging in mammals including humans. As a result, we present an alcohol-dehydrogenase-mediated anti-aging response (AMAR) that is essential for C. elegans longevity driven by HLH-30 overexpression, caloric restriction, mTOR inhibition, and insulin-signaling deficiency. The sole overexpression of ADH-1 is sufficient to activate AMAR, which extends healthspan and lifespan by reducing the levels of glycerol-an age-associated and aging-promoting alcohol. Adh1 overexpression is also sufficient to promote longevity in yeast, and adh-1 orthologs are induced in calorically restricted mice and humans, hinting at ADH-1 acting as an anti-aging effector across phyla.

Immunostaining of intact C. elegans using polyacrylamide embedding

A major barrier to immunostaining Caenorhabditis elegans is the permeabilization of the worm's cuticle without distorting or damaging its body. We present here a gel-based immobilization protocol for fixed worms coupled with chemical and enzymatic permeabilization. The permeabilization is followed by antibody staining and fluorescent imaging. This protocol can be modified for different fixatives, permeabilizing reagents, or molecular readouts. Unlike previous immunostaining approaches, such as freeze cracking or dissection, this protocol enables immunostaining across the whole body of a well-preserved C. elegans.

Dietary serine-microbiota interaction enhances chemotherapeutic toxicity without altering drug conversion

The gut microbiota metabolizes drugs and alters their efficacy and toxicity. Diet alters drugs, the metabolism of the microbiota, and the host. However, whether diet-triggered metabolic changes in the microbiota can alter drug responses in the host has been largely unexplored. Here we show that dietary thymidine and serine enhance 5-fluoro 2'deoxyuridine (FUdR) toxicity in C. elegans through different microbial mechanisms. Thymidine promotes microbial conversion of the prodrug FUdR into toxic 5-fluorouridine-5'-monophosphate (FUMP), leading to enhanced host death associated with mitochondrial RNA and DNA depletion, and lethal activation of autophagy. By contrast, serine does not alter FUdR metabolism. Instead, serine alters E. coli's 1C-metabolism, reduces the provision of nucleotides to the host, and exacerbates DNA toxicity and host death without mitochondrial RNA or DNA depletion; moreover, autophagy promotes survival in this condition. This work implies that diet-microbe interactions can alter the host response to drugs without altering the drug or the host.

The Ancient Genetic Networks of Obesity: Whole-Animal Automated Screening for Conserved Fat Regulators

Caenorhabditis elegans is the first and only metazoan model that enables whole-body gene knockdown by simply feeding their standard laboratory diet, E. coli, carrying RNA interference (RNAi)-expressing constructs. The simplicity of the RNAi treatment, small size, and fast reproduction rate of C. elegans allow us to perform whole-animal high-throughput genetic screens in wild-type, mutant, or otherwise genetically modified C. elegans. In addition, more than 65% of C. elegans genes are conserved in mammals including human. In particular, C. elegans metabolic pathways are highly conserved, which supports the study of complex diseases such as obesity in this genetically tractable model system. In this chapter, we present a detailed protocol for automated high-throughput whole-animal RNAi screening to identify the pathways promoting obesity in diet-induced and genetically driven obese C. elegans. We describe an optimized high-content screening protocol to score fat mass and body fat distribution in whole animals at large scale. We provide optimized pipelines to automatically score phenotypes using the open-source CellProfiler platform within the context of supercomputer clusters. Further, we present a guideline to optimize information workflow from the automated microscope to a searchable database. The approaches described here enable unveiling the whole network of gene-gene and gene-environment interactions that define metabolic health or disease status in this proven model of human disease, but similar principles can be applied to other disease models.

A lysosome-centered view of nutrient homeostasis

Lysosomes are highly acidic cellular organelles traditionally viewed as sacs of enzymes involved in digesting extracellular or intracellular macromolecules for the regeneration of basic building blocks, cellular housekeeping, or pathogen degradation. Bound by a single lipid bilayer, lysosomes receive their substrates by fusing with endosomes or autophagosomes, or through specialized translocation mechanisms such as chaperone-mediated autophagy or microautophagy. Lysosomes degrade their substrates using up to 60 different soluble hydrolases and release their products either to the cytosol through poorly defined exporting and efflux mechanisms or to the extracellular space by fusing with the plasma membrane. However, it is becoming evident that the role of the lysosome in nutrient homeostasis goes beyond the disposal of waste or the recycling of building blocks. The lysosome is emerging as a signaling hub that can integrate and relay external and internal nutritional information to promote cellular and organismal homeostasis, as well as a major contributor to the processing of energy-dense molecules like glycogen and triglycerides. Here we describe the current knowledge of the nutrient signaling pathways governing lysosomal function, the role of the lysosome in nutrient mobilization, and how lysosomes signal other organelles, distant tissues, and even themselves to ensure energy homeostasis in spite of fluctuations in energy intake. At the same time, we highlight the value of genomics approaches to the past and future discoveries of how the lysosome simultaneously executes and controls cellular homeostasis.

Guidelines for monitoring autophagy in Caenorhabditis elegans

The cellular recycling process of autophagy has been extensively characterized with standard assays in yeast and mammalian cell lines. In multicellular organisms, numerous external and internal factors differentially affect autophagy activity in specific cell types throughout the stages of organismal ontogeny, adding complexity to the analysis of autophagy in these metazoans. Here we summarize currently available assays for monitoring the autophagic process in the nematode C. elegans. A combination of measuring levels of the lipidated Atg8 ortholog LGG-1, degradation of well-characterized autophagic substrates such as germline P granule components and the SQSTM1/p62 ortholog SQST-1, expression of autophagic genes and electron microscopy analysis of autophagic structures are presently the most informative, yet steady-state, approaches available to assess autophagy levels in C. elegans. We also review how altered autophagy activity affects a variety of biological processes in C. elegans such as L1 survival under starvation conditions, dauer formation, aging, and cell death, as well as neuronal cell specification. Taken together, C. elegans is emerging as a powerful model organism to monitor autophagy while evaluating important physiological roles for autophagy in key developmental events as well as during adulthood.

ω-6 Polyunsaturated fatty acids extend life span through the activation of autophagy

Adaptation to nutrient scarcity depends on the activation of metabolic programs to efficiently use internal reserves of energy. Activation of these programs in abundant food regimens can extend life span. However, the common molecular and metabolic changes that promote adaptation to nutritional stress and extend life span are mostly unknown. Here we present a response to fasting, enrichment of ω-6 polyunsaturated fatty acids (PUFAs), which promotes starvation resistance and extends Caenorhabditis elegans life span. Upon fasting, C. elegans induces the expression of a lipase, which in turn leads to an enrichment of ω-6 PUFAs. Supplementing C. elegans culture media with these ω-6 PUFAs increases their resistance to starvation and extends their life span in conditions of food abundance. Supplementation of C. elegans or human epithelial cells with these ω-6 PUFAs activates autophagy, a cell recycling mechanism that promotes starvation survival and slows aging. Inactivation of C. elegans autophagy components reverses the increase in life span conferred by supplementing the C. elegans diet with these fasting-enriched ω-6 PUFAs. We propose that the salubrious effects of dietary supplementation with ω-3/6 PUFAs (fish oils) that have emerged from epidemiological studies in humans may be due to a similar activation of autophagic programs.

An image analysis toolbox for high-throughput C. elegans assays

We present a toolbox for high-throughput screening of image-based Caenorhabditis elegans phenotypes. The image analysis algorithms measure morphological phenotypes in individual worms and are effective for a variety of assays and imaging systems. This WormToolbox is available through the open-source CellProfiler project and enables objective scoring of whole-worm high-throughput image-based assays of C. elegans for the study of diverse biological pathways that are relevant to human disease.

C. elegans major fats are stored in vesicles distinct from lysosome-related organelles

Genetic conservation allows ancient features of fat storage endocrine pathways to be explored in C. elegans. Multiple studies have used Nile red or BODIPY-labeled fatty acids to identify regulators of fat mass. When mixed with their food, E. coli bacteria, Nile red, and BODIPY-labeled fatty acids stain multiple spherical cellular structures in the C. elegans major fat storage organ, the intestine. However, here we demonstrate that, in the conditions previously reported, the lysosome-related organelles stained by Nile red and BODIPY-labeled fatty acids are not the C. elegans major fat storage compartment. We show that the major fat stores are contained in a distinct cellular compartment that is not stained by Nile red. Using biochemical assays, we validate oil red O staining as a method to assess major fat stores in C. elegans, allowing for efficient and accurate genetic and functional genomic screens for genes that control fat accumulation at the organismal level.

Whole-animal high-throughput screens: the C. elegans model

The nematode Caenorhabditis elegans shows a high degree of conservation of molecular pathways related to human disease, yet is only 1-mm long and can be considered as a microorganism. Because of the development of a simple but systematic RNA-interference (RNAi) methodology, C. elegans is the only metazoan in which the impact of "knocking-down" nearly every gene in the genome can be analyzed in a whole living animal. Both functional genomic studies and chemical screens can be carried out using C. elegans in vivo screens in a context that preserves intact cell-to-cell communication, neuroendocrine signaling, and every aspect of the animal's metabolism necessary to survive and reproduce in lab conditions. This feature enables studies that are impossible to undertake in cell-culture-based screens. Although genome-wide RNAi screens and limited small-molecule screens have been successfully performed in C. elegans, they are typically extremely labor-intensive. Furthermore, technical limitations have precluded quantitative measurements and time-resolved analyses.In this chapter, we provide detailed protocols to carry out automated high-throughput whole-animal RNAi and chemical screens. We describe methods to perform screens in solid and liquid media, in 96 and 384-well format, respectively. We describe the use of automated handling, sorting, and microscopy of worms. Finally, we give information about worm-adapted image analysis tools to quantify phenotypes. The technology presented here facilitates large-scale C. elegans genetic and chemical screens and it is expected to help shed light on relevant biological areas.

Fat metabolism links germline stem cells and longevity in C. elegans

Fat metabolism, reproduction, and aging are intertwined regulatory axes; however, the mechanism by which they are coupled remains poorly understood. We found that germline stem cells (GSCs) actively modulate lipid hydrolysis in Caenorhabditis elegans, which in turn regulates longevity. GSC arrest promotes systemic lipolysis via induction of a specific fat lipase. Subsequently, fat mobilization is promoted and life span is prolonged. Constitutive expression of this lipase in fat storage tissue generates lean and long-lived animals. This lipase is a key factor in the lipid hydrolysis and increased longevity that are induced by decreased insulin signaling. These results suggest a link between C. elegans fat metabolism and longevity.

Helicobacter pylori genes involved in avoidance of mutations induced by 8-oxoguanine

Chromosomal rearrangements and base substitutions contribute to the large intraspecies genetic diversity of Helicobacter pylori. Here we explored the base excision repair pathway for the highly mutagenic 8-oxo-7,8-dihydroguanine (8-oxoG), a ubiquitous form of oxidized guanine. In most organisms, 8-oxoG is removed by a specific DNA glycosylase (Fpg in bacteria or OGG1 in eukaryotes). In the case where replication of the lesion yields an A/8-oxoG base pair, a second DNA glycosylase (MutY) can excise the adenine and thus avoid the fixation of the mutation in the next round of replication. In a genetic screen for H. pylori genes complementing the hypermutator phenotype of an Escherichia coli fpg mutY strain, open reading frame HP0142, a putative MutY coding gene, was isolated. Besides its capacity to complement E. coli mutY strains, HP0142 expression resulted in a strong adenine DNA glycosylase activity in E. coli mutY extracts. Consistently, the purified protein also exhibited such an activity. Inactivation of HP0142 in H. pylori resulted in an increase in spontaneous mutation frequencies. An Mg-dependent AP (abasic site) endonuclease activity, potentially allowing the processing of the abasic site resulting from H. pylori MutY activity, was detected in H. pylori cell extracts. Disruption of HP1526, a putative xth homolog, confirmed that this gene is responsible for the AP endonuclease activity. The lack of evidence for an Fpg/OGG1 functional homolog is also discussed.

Evidence for the active role of a novel nuclease from Helicobacter pylori in the horizontal transfer of genetic information

Helicobacter pylori is a gram-negative bacterium that colonizes the human stomach, causes gastritis, and is associated with ulcers and gastric cancer. H. pylori is naturally competent for transformation. Natural genetic transformation is believed to be essential for the genetic plasticity observed in this species. While the relevance of horizontal gene transfer in H. pylori adaptiveness and antibiotic resistance is well documented, the DNA transformation machinery components are barely known. No enzymatic activity associated with the transformation process has been determined experimentally and described. We isolated, microsequenced, and cloned a major DNA nuclease from H. pylori. This protein, encoded by the open reading frame hp0323, was expressed in Escherichia coli. The purified protein, NucT, has a cation-independent thermostable nuclease activity that preferentially cleaves single-stranded DNA. NucT is associated with the membrane. NucT-deficient H. pylori strains are one or more orders of magnitude less efficient than the parental strain for transformation with either chromosomal or self-replicating plasmid DNA. To the best of our knowledge, NucT is the first nuclease identified in a gram-negative natural transformation system, and its existence suggests that there is a mechanism of DNA processing and uptake similar to the mechanisms in well-studied gram-positive systems.

Crystal structures of 3-methyladenine DNA glycosylase MagIII and the recognition of alkylated bases

DNA glycosylases catalyze the excision of chemically modified bases from DNA. Although most glycosylases are specific to a particular base, the 3-methyladenine (m3A) DNA glycosylases include both highly specific enzymes acting on a single modified base, and enzymes with broader specificity for alkylation-damaged DNA. Our structural understanding of these different enzymatic specificities is currently limited to crystal and NMR structures of the unliganded enzymes and complexes with abasic DNA inhibitors. Presented here are high-resolution crystal structures of the m3A DNA glycosylase from Helicobacter pylori (MagIII) in the unliganded form and bound to alkylated bases 3,9-dimethyladenine and 1,N6-ethenoadenine. These are the first structures of a nucleobase bound in the active site of a m3A glycosylase belonging to the helix-hairpin-helix superfamily. MagIII achieves its specificity for positively-charged m3A not by direct interactions with purine or methyl substituent atoms, but rather by stacking the base between two aromatic side chains in a pocket that excludes 7-methylguanine. We report base excision and DNA binding activities of MagIII active site mutants, together with a structural comparison of the HhH glycosylases.

Pathogen DNA as target for host-generated oxidative stress: role for repair of bacterial DNA damage in Helicobacter pylori colonization

Helicobacter pylori elicits an oxidative stress during host colonization. This oxidative stress is known to cause lesions in the host DNA. Here we addressed the question as to whether the pathogen DNA is subject to lethal or mutational damage by the host-generated oxidative response. H. pylori Hpnth mutants unable to repair oxidized pyrimidines from the bacterial DNA were generated. H. pylori strains lacking a functional endonuclease III (HpNth) showed elevated spontaneous and induced mutation rates and were more sensitive than the parental strain to killing by exposure to oxidative agents or activated macrophages. Although under laboratory conditions the Hpnth mutant strain grows as well as the wild-type strain, in a mouse infection the stomach bacterial load gradually decreases while the population in the wild-type strain remains stable, showing that endonuclease III deficiency reduces the colonization capacity of the pathogen. In coinfection experiments with a wild-type strain, Hpnth cells are eradicated 15 days postinfection (p.i.) even when inoculated in a 1:9 wild-type:mutant strain ratio, revealing mutagenic lesions that are counterselected under competition conditions. These results show that the host effectively induces lethal and premutagenic oxidative DNA adducts on the H. pylori genome. The possible consequences of these DNA lesions on the adaptability of H. pylori strains to new hosts are discussed.

A novel 3-methyladenine DNA glycosylase from Helicobacter pylori defines a new class within the endonuclease III family of base excision repair glycosylases

The cloning, purification, and characterization of MagIII, a 3-methyladenine DNA glycosylase from Helicobacter pylori, is presented in this paper. Sequence analysis of the genome of this pathogen failed to identify open reading frames potentially coding for proteins with a 3-methyladenine DNA glycosylase activity. The putative product of the HP602 open reading frame, reported as an endonuclease III, shares extensive amino acid sequence homology with some bacterial members of this family and has the canonic active site helix-hairpin-helix-GPD motif. Surprisingly, this predicted H. pylori endonuclease III encodes a 25,220-Da protein able to release 3-methyladenine, but not oxidized bases, from modified DNA. MagIII has no abasic site lyase activity and displays the substrate specificity of the 3-methyladenine-DNA glycosylase type I of Escherichia coli (Tag) because it is not able to recognize 7-methylguanine or hypoxanthine as substrates. The expression of the magIII open reading frame in null 3-methyladenine glycosylase E. coli (tag alkA) restores to this mutant partial resistance to alkylating agents. MagIII-deficient H. pylori cells show an alkylation-sensitive phenotype. H. pylori wild type cells exposed to alkylating agents present an adaptive response by inducing the expression of magIII. MagIII is thus a novel bacterial member of the endonuclease III family, which displays biochemical properties not described for any of the members of this group until now.

Perforated appendicitis: prospective outcome analysis for 150 children

BACKGROUND/PURPOSE

Controversy persists in the management of perforated appendicitis with regard to antibiotic choice and duration, operative timing, drain utilization, and wound closure. For 2 decades at the authors' institution, patients were treated with ampicillin, gentamicin, and clindamycin for 10 inpatient days, with drains in the abdomen, resulting in lower complication rates than most other published series. Managed care pressures have led to less aggressive medical management regimens with length of stay and financial factors viewed as principal outcome measures with little emphasis on clinical outcomes. In addition, there are little prospective data on clinical outcomes. The authors sought to determine whether our previously documented excellent quality outcomes could be maintained when modifications aimed at decreasing cost and length of stay in our protocol were instituted.

METHODS

The authors monitored prospectively clinical outcomes in patients with perforated appendicitis treated according to their clinical practice guidelines over a 43-month period. Patients received a single antibiotic, piperacillin-tazobactam, intravenously for 10 days. They were permitted to go home with a percutaneous intravenous catheter for the final 5 days if medical and social criteria were met. Other practices from our earlier protocol were continued, including immediate operation, placement of Penrose drains, and primary wound closure.

RESULTS

Of 150 patients treated on our protocol, major complications included intraabdominal abscess in 5 (3.3%), cecal fistula in 2 (1.3%), phlegmon in 3 (2.0%), wound infection in 4 (2.7%), and no small bowel obstructions requiring operation. None of these complications, nor their aggregate, were significantly more common than those reported in 373 patients treated over 11 years on the authors' prior protocol (chi2, P > .05).

CONCLUSIONS

Prospective outcome analysis of our protocol shows that a single broad-spectrum antibiotic (allowing portions of therapy to be delivered less expensively on an outpatient basis) effectively can treat postoperative appendicitis with very few infectious complications. These outcome data provide baseline against which future protocols can be compared. All treatment modifications aimed at decreasing costs must be analyzed to ensure quality of care is not unduly compromised.

Hospital infection prevention and control: a model for improving the quality of hospital care in low- and middle-income countries

Continuous quality improvement (CQI) is a powerful methodology for improving clinical outcomes and patient satisfaction while reducing inefficiency and costs. However, most hospitals in low- and middle-income countries have little experience with CQI methods. Hospital infection prevention is an ideal model for nascent efforts to improve the quality of hospital care because of its proven efficacy in reducing the occurrence of infections that compromise patient outcomes and increase costs. This article describes the design and implementation of a demonstration project to reduce the incidence of surgical-site infections (SSIs) for hospitals with little experience with quality-improvement methods. The project has a high likelihood of producing measurable reductions in SSI rates and hospital costs related to inefficient use of perioperative antimicrobial prophylaxis. Moreover, participating staff will gain experience that can be applied to efforts to improve the quality of other aspects of hospital care.

Osteomyelitis in children: gadolinium-enhanced MR imaging

Fifteen pediatric patients with biopsy- or culture-proved nonspinal osteomyelitis were studied with magnetic resonance (MR) imaging. Osteomyelitis was acute in seven patients, subacute in three, and chronic in five. Four patients had subperiosteal abscesses, one had a large associated soft-tissue abscess, and one had an intraosseous (Brodie) abscess. Areas of active inflammation had decreased marrow signal intensity on T1-weighted images, increased signal intensity on T2-weighted images, and enhancement on T1-weighted images obtained after gadopentetate dimeglumine administration (n = 10). Abscesses were rim enhancing (n = 3) or not (n = 2) with gadolinium-enhanced MR imaging. Nonenhancing areas presumably represented necrotic material. Gadolinium-enhanced MR imaging assisted in definition of the presence and extent of nonvascularized fluid collections within the bone and/or adjacent soft tissues and the extent of bone involvement in patients with chronic osteomyelitis. It also helped guide surgical debridement of intraosseous disease (n = 7) and open or percutaneous drainage of subperiosteal or soft-tissue fluid collections (n = 5).

Outpatient treatment of febrile infants 28 to 89 days of age with intramuscular administration of ceftriaxone

STUDY OBJECTIVE

To determine the outcome of outpatient treatment of febrile infants 28 to 89 days of age with intramuscular administration of ceftriaxone.

DESIGN

Prospective consecutive cohort study.

SETTING

Urban emergency department.

PATIENTS

Five hundred three infants 28 to 89 days of age with temperatures greater than or equal to 38 degrees C who did not appear ill, had no source of fever detected on physical examination, had a peripheral leukocyte count less than 20 x 10(9) cells/L, had a cerebrospinal fluid leukocyte count less than 10 x 10(6)/L, did not have measurable urinary leukocyte esterase, and had a caretaker available by telephone. Follow-up was obtained for all but one patient (99.8%).

INTERVENTION

After blood, urine, and cerebrospinal fluid cultures had been obtained, the infants received 50 mg/kg intramuscularly administered ceftriaxone and were discharged home. The infants returned for evaluation and further intramuscular administration of ceftriaxone 24 hours later; telephone follow-up was conducted 2 and 7 days later.

RESULTS

Twenty-seven patients (5.4%) had a serious bacterial infection identified during follow-up; 476 (94.6%) did not. Of the 27 infants with serious bacterial infections, 9 (1.8%) had bacteremia (8 of these had occult bacteremia and 1 had bacteremia with a urinary tract infection), 8 (1.6%) had urinary tract infections without bacteremia, and 10 (2.0%) had bacterial gastroenteritis without bacteremia. Clinical screening criteria did not enable discrimination between infants with and those without serious bacterial infections. All infants with serious bacterial infections received an appropriate course of antimicrobial therapy and were well at follow-up. One infant had osteomyelitis diagnosed 1 week after entry into the study, received an appropriate course of intravenous antimicrobial therapy, and recovered fully.

CONCLUSIONS

After a full evaluation for sepsis, outpatient treatment of febrile infants with intramuscular administration of ceftriaxone pending culture results and adherence to a strict follow-up protocol is a successful alternative to hospital admission.

Adaptation of the Centers for Disease Control guidelines for the prevention of nosocomial infection in a pediatric intensive care unit in Jakarta, Indonesia

We attempted to implement a nosocomial infection control program based on the Centers for Disease Control (CDC) guidelines in an urban Indonesian public hospital at the request of Project Hope. Adoption of unmodified CDC guidelines was impeded by a substandard physical plant, absence of an infection control infrastructure, limited sterilization capabilities, lack of clinical microbiologic laboratory support, and the expense of single use medical devices. After on-site evaluations, CDC guidelines were extensively modified so that they were appropriate for local conditions and culture. Strategies included inexpensive architectural modifications, addition of sinks and a commode, introduction of disinfection procedures for reuse of disposable medical devices, and adaptation of available supplies for maintenance of aseptic technique. On subsequent site visits, many physical changes had been accomplished, and handling of reusable and disposable medical devises had improved considerably but adoption of clinical practice policies was incomplete. We conclude that it may be difficult to implement and sustain improvements in clinical practice in the absence of an infection control infrastructure and a strong commitment by hospital clinicians and administrators. Additional research is needed to refine flexible methods for rapidly assessing the specific infection control needs of institutions with widely disparate resources, patient populations, environments, and cultures.

False resistance to imipenem with a microdilution susceptibility testing system

Routine monitoring of antibiotic resistance at Children's Hospital, Boston, detected a dramatic increase in the prevalence of imipenem-resistant strains of Pseudomonas aeruginosa. Further studies documented that false resistance to imipenem was due, in part, to the loss of imipenem potency in customized MIC microdilution trays supplied by Sensititre Ltd. (West Sussex, United Kingdom). Recognition of the problem was delayed by use of the quality control standard recommended by the manufacturer, which were higher and broader than those suggested by the National Committee for Clinical Laboratory Standards.

Scedosporium inflatum: clinical spectrum of a newly recognized pathogen

The clinical course of 11 patients is reported: a newly-described species, Scedosporium inflatum, was isolated from each. Infections were primarily focally invasive and involved musculoskeletal tissues. All but one followed penetrating trauma, often minor, or surgery. Two cases, one fatal, occurred in immunosuppressed patients. In only one case was there presumptive hematogenous spread. In three cases colonization with S. inflatum could not reliably be distinguished from infection. In vitro susceptibility testing of isolates from all patients showed that all were resistant to amphotericin B, miconazole, and ketoconazole and most were resistant to fluconazole and itraconazole. The optimum management of S. inflatum infection is not apparent: Although several patients recovered without antifungal therapy, progressive unremitting infection occurred in an immunocompromised patient and in a previously healthy child despite aggressive antifungal chemotherapy and surgical debridement.

Genetic relatedness among structural protein genes of dengue 1 virus strains

The structural protein-coding genomic regions of dengue virus type 1 (DEN-1) strains representing three distinct topotypes (Thailand, Philippines and Caribbean) were cloned and sequenced. In addition the envelope (E) nucleotide sequences of two recent Caribbean topotype DEN-1 isolates were obtained by direct RNA sequencing. The nucleotide sequence of the DEN-1 viruses in the structural gene region was found to be highly conserved with greater than 95% nucleotide sequence homology and with less than 4% change in the amino acid sequence. Although there was a less than 2% change in the nucleotide sequence of DEN-1 E proteins, strains could be differentiated by the clusters of nucleotide changes. Furthermore, the deduced amino acid changes in the E protein were clustered primarily within the proposed immunologically reactive regions. Genomic nucleotide sequence comparisons did not define geographical or virulence markers but located unique clusters of nucleotide/amino acid changes for each of the three topotypes of DEN-1 viruses examined.

Impact of rapid antigen tests for group A streptococcal pharyngitis on physician use of antibiotics and throat cultures

Using case scenarios and an interview guided by a decision tree diagram, the clinical strategies of 150 physicians (50 private pediatricians, 50 health maintenance organization pediatricians and 50 pediatric residents) were assessed for the management of pharyngitis under three conditions: (1) no rapid antigen detection test available for diagnosing Group A streptococcal disease; (2) antigen test result available in 20 minutes; and (3) antigen test result available in 4 hours. The sensitivity of the antigen test was designated as 0.95 if the growth of rare or few Group A streptococci on throat culture was discounted and 0.82 if any growth was considered significant, and the specificity was set at 0.98. In a standardized pediatric case with a prior probability of Group A streptococcal disease of 0.58, 84% of clinicians would order a 20-minute test and 39% would order a 4-hour test. The 20-minute test would reduce throat culture use by 54%, reduce the proportion of patients exposed to antibiotics from 86% to 65% and reduce total antibiotic treatment days by 13.8%. Effects would be less pronounced for a low probability case or if results of antigen testing were not available for 4 hours. Provided a test with a documented high sensitivity and specificity were used, a rapid antigen test with results promptly available would substantially reduce throat culture use and unnecessary antibiotic exposures in children with a moderate prior probability of streptococcal disease.

Effects of transport inhibitors on the generation and transport of a soluble viral glycoprotein

The generation and transport of the soluble glycoprotein (Gs) of wild-type vesicular stomatitis virus (VSV) were studied using cell fractionation and transport inhibitors. Gs was found in the rough endoplasmic reticulum (RER) and the Golgi-enriched membrane fractions of infected Chinese hamster ovary cells. The identity of intracellular Gs was confirmed by its precipitation with a monoclonal antibody to the ectodomain but not with a anti-peptide antibody directed against the first 15 amino acids at the carboxy terminus of the VSV transmembrane glycoprotein G. Their extracellular appearance was affected in a concentration-dependent manner by monensin and carbonyl cyanide m-chlorophenylhydrazone (CCCP) and was completely inhibited by incubation at 20 degrees. Inhibitors failed to dissociate the transport of Gs from G. These experiments indicate that in fibroblast cells Gs can be generated intracellularly, probably in the RER, and that Gs, like G, is transported from there to the Golgi complex and then presumably to the extracellular environment.

Antibody-induced modulation of proteins in vesicular stomatitis virus-infected fibroblasts

When vesicular stomatitis virus-infected baby hamster kidney cells were treated with rabbit anti-vesicular stomatitis virus serum, there was a loss of the viral glycoprotein G into acid-soluble products. This degradation occurred within minutes at 37 degrees C and required the presence of G protein at the cell surface. The degree of degradation depended on antiserum concentration. The antiserum, also, prevented maturation of extracellular virions and induced partial degradation of the intracellular viral proteins, without affecting host proteins. The degradation could not be prevented by the presence of lysosomotropic agents, protease inhibitors, colchicine, or cytochalasin B. Similar kinetics and specificity of degradation was obtained with cells infected with vesicular stomatitis virus mutants that were less cytopathic. These results characterize a model system for studying the parameters and consequences of antigenic modulation as well as for studying the fate of viral antigens during persistent infections.

Enhancement of dengue virus infection in monocytes by flavivirus antisera

Enhanced dengue 2 virus (D2V) infection in suspension cultures of human peripheral blood mononuclear phagocytes (PBL) produced by subneutralizing concentrations of dengue antisera has been described previously. In this study, the enhancement phenomenon was found to be a general property of representative flavivirus antisera. All except one of 24 antisera, which had been raised by 1-3 injections of flaviviruses in rabbits, enhanced the growth of dengue 2 virus in human PBL. Flavivirus antisera showing the greatest level of cross-reactivity against a battery of 42 flavivirus antigens in the hemagglutination-inhibition test were most potent in enhancing dengue replication in PBL cultures. Cross-neutralizing reactivity did not relate to enhanced D2V infection. However nearly one-half of studied flavivirus antisera neutralized D2V at dilutions of 1:10 or 1:20. Heterotypic D2V neutralizing antibody could serve as a "brake" on infection enhancement in vivo. Observations should be made in the field to look for possible enhancement of dengue infection in heterotypic flavivirus immunes.

Specific lethality of silica for human peripheral blood mononuclear phagocytes, in vitro

Human peripheral blood mononuclear cells, cultured in the presence of 100 microgram/ml protein-coated silica particles, were studied to determine changes in number and function of monocytes, immunoglobulin bearing (B), sheep red blood cell rosetting (T) lymphocytes and the effector cells of antibody dependent cell-mediated cytotoxicity (ADCC). After 24-48 h, phagocytic cells were effectively eliminated from culture but there was no significant reduction in number or function of T or B lymphocytes or in ADCC to cell line targets. ADCC to erythrocyte targets was inhibited but not completely blocked. It is concluded that silica is a specific toxin for human peripheral blood mononuclear phagocytes and may be useful in in vitro immunological studies as a means of eliminating or determining the role of these cells without resort to separation methods which result in losses of cells other than monocytes.

Dengue viruses and mononuclear phagocytes. I. Infection enhancement by non-neutralizing antibody

Cultured mononuclear peripheral blood leukocytes (PBL) from nonimmune human beings and monkeys are nonpermissive to dengue 2 virus (D2V) infection at multiplicities of infection of 0.001-0.1, but become permissive when non-neutralizing dengue antibody is added to medium. D2V infection occurred in PBL prepared from anti-coagulated but not from defibrinated plasma. Infection enhancement was produced by multiple lots of heterotypic anti-dengue raised in several mammalian species. Homotypic anti-dengue neutralized D2V at high concentrations but enhanced at low concentrations; enhancement end point in one serum was 1:320,000. The infection-enhancing factor was a noncytophilic antibody of the IgG class. D2V infection occurred in the absence of heat-labile complement components but did not occur when complexes were prepared with anti- dengue F(ab)(2). Treatment of PBL with several proteases increased permissiveness to D2V infection by immune complexes but not by virus alone. Two rhesus monkey serums collected 14 days after D2V infection contained an IgG antibody with high-titered enhancing activity but with no hemagglutination-inhibition or neutralizing activity. Virus-antibody complexes are irreversibly attached to PBL within 15 min and completely internalized in 60 min. There was considerable variation in cellular infection in different experiments, however, maximum virus yields usually exceeded 1,000 plaque-forming units per 1 x 10(6) PBL occurring between 2 and 4 days in culture. In vitro antibody-dependent infection of PBL provides a possible model for study of pathogenetic mechanisms in infants with dengue shock syndrome who passively acquire maternal anti-dengue IgG.

Dengue viruses and mononuclear phagocytes. II. Identity of blood and tissue leukocytes supporting in vitro infection

Studies were made on the identity of human and monkey mononuclear leukocytes permissive to antibody-enhanced dengue 2 virus (D2V) infection. In cultures of peripheral blood leukocytes (PBL) inoculated immediately after separation, it was concluded that only mononuclear phagocytes support dengue infection. This is based upon observations that D2V-permissive cells were resistant to 1,200 rads, were both plastic adherent and nonadherent, were removed when passed through nylon wool columns in 10 percent fetal bovine serum or 100 percent autologous serum, and were destroyed by incubation with 100 mug/ml particulate silica. On direct immunofluorescence staining, perinuclear dengue antigen was visualized at 24 h, becoming maximal at 60 h. Antigen-containing cells had ample cytoplasm, ruffled cytoplasmic membrane, and 73 percent were actively phagocytic. As further evidence of the infection of mononuclear phagocytes, antibody-enhanced D2V replication was observed in bone marrow cultures from five of five rhesus monkeys, but not in cell cultures of spleen, thymus, or lymph nodes prepared from the same animals. It is hypothesized that dengue virus complexed with non-neutralizing antibody is internalized by immune phagocytosis in a mononuclear phagocyte with a defective virus-destroying mechanism. Dengue permissiveness may depend upon cellular immaturity since bone marrow leukocytes could be infected even when held for 4 days before infection while PBL held for this time decreased in permissiveness. In vitro antibody-dependent infection of mononuclear phagocytes should prove useful as a model for study of immunopathologic mechanisms in human dengue.