Statistical method for testing the neutral mutation hypothesis by DNA polymorphism.

Metabolomics studies hold promise for the discovery of pathways linked to disease processes. Cardiovascular disease (CVD) represents the leading cause of death and morbidity worldwide. Here we used a metabolomics approach to generate unbiased small-molecule metabolic profiles in plasma that predict risk for CVD. Three metabolites of the dietary lipid phosphatidylcholine—choline, trimethylamine N-oxide (TMAO) and betaine—were identified and then shown to predict risk for CVD in an independent large clinical cohort. Dietary supplementation of mice with choline, TMAO or betaine promoted upregulation of multiple macrophage scavenger receptors linked to atherosclerosis, and supplementation with choline or TMAO promoted atherosclerosis. Studies using germ-free mice confirmed a critical role for dietary choline and gut flora in TMAO production, augmented macrophage cholesterol accumulation and foam cell formation. Suppression of intestinal microflora in atherosclerosis-prone mice inhibited dietary-choline-enhanced atherosclerosis. Genetic variations controlling expression of flavin monooxygenases, an enzymatic source of TMAO, segregated with atherosclerosis in hyperlipidaemic mice. Discovery of a relationship between gut-flora-dependent metabolism of dietary phosphatidylcholine and CVD pathogenesis provides opportunities for the development of new diagnostic tests and therapeutic approaches for atherosclerotic heart disease.

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Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease

Extended-spectrum β-lactamases (ESBLs) are a rapidly evolving group of β-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these β-lactamases. This extends the spectrum of β-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

Extended-spectrum beta-lactamases: a clinical update.

https://stacks.cdc.gov/view/cdc/6674/cdc_6674_DS1.pdf

Guideline for Hand Hygiene in Health-Care Settings. Recommendations of the Healthcare Infection Control Practices Advisory Committee and the HIPAC/SHEA/APIC/IDSA Hand Hygiene Task Force.

Transcription of the c-fos proto-oncogene is greatly increased within minutes of administering purified growth factors to quiescent 3T3 cells. This stimulation is the most rapid transcriptional response to peptide growth factors yet described, and implies a role for c-fos in cell-cycle control. Transformation by c-fos may result from a temporal deregulation of this control.

Stimulation of 3T3 cells induces transcription of the c- fos proto-oncogene

We have compared the ability of beta-lactam antibiotics to induce beta-lactamase synthesis and antagonize the in-vitro activity of other beta-lactams and also to select mutants with derepressed beta-lactamase synthesis amongst representative Gram-negative bacilli that produce inducible beta-lactamases. Both imipenem and cefoxitin were potent inducers of beta-lactamase and were able to antagonize the activity of other beta-lactams against isolates of Enterobacter cloacae, Citrobacter freundii and Pseudomonas aeruginosa when the two beta-lactams were present simultaneously. However, there was no antagonism for any compound against any of the organisms when the imipenem or cefoxitin was removed immediately before susceptibility to the other compounds was measured. Cefotaxime was a less potent inducer of beta-lactamase and failed to antagonize the activity of other compounds, even when present concurrently with them. Neither imipenem nor cefoxitin induced beta-lactamase synthesis in a strain of Escherichia coli, nor did they antagonize the activity of other beta-lactams against this strain. Imipenem was compared with cefotaxime and cefoxitin as an agent for the selection of beta-lactam-resistant variants. Resistant variants were obtained from isolates of Ent. cloacae, C. freundii and P. aeruginosa when cefotaxime or cefoxitin was used as the selective agent. Most of them synthesized beta-lactamase constitutively and showed reduced susceptibility to a wide range of beta-lactams, but not to imipenem. Variants with reduced susceptibility to imipenem were obtained only from the two isolates of P. aeruginosa. They did not show cross resistance to other beta-lactams and were not distinguishable from the parent strains in beta-lactamase production.

The effects on ß-lactam susceptibility of phenotypic induction and genotypic derepression of ß-lactamase synthesis

Importance of the field: Flavin-containing monooxygenases (FMOs) metabolize a number of therapeutic drugs. However, their role in drug metabolism has been overlooked compared with that of the cytochromes P450 (CYPs). Genetic variants of FMOs are expected to influence drug response and/or contribute to adverse drug reactions.Areas covered in the review: We review tissue-specific expression of FMOs and genetic variation that may influence drug metabolism. We discuss how the use of mouse lines in which Fmo genes have been deleted can demonstrate the role an FMO plays in the metabolism of a drug, particularly if the drug is subject to metabolism by other enzymes, for example, CYPs, or undergoes retro-reduction. We cite seminal papers and review articles to give the reader an appreciation of the FMO field.What the reader will gain: Insights into the problems associated with determining the contribution of an FMO to the metabolism of a drug and how an Fmo-knockout mouse line has revealed the role of FMO1 in the...

The potential of knockout mouse lines in defining the role of flavin-containing monooxygenases in drug metabolism

We agree with Gould’s comments about the shortcomings of the Stokes’ method and the need for the ‘comparability of data between different centres across the country so that resistance surveillance data can be reliably compared’. In fact we would go further and suggest that, since bacteria do not respect national borders, there should be worldwide comparability of data. Where we part company with Gould is in how we approach that goal. In his paper, Gould outlines the relative merits of agar disc diffusion and breakpoint MIC methods and, in doing so, indicates many of the factors that affect the reproducibility of the former method. These include inoculum, temperature, atmosphere and generation time of the bacterium. Surely, however, these affect both methods? Furthermore, we would not agree with the view that only the broth dilution method lends itself well to automation: automatic plate readers, with their data collation system, have a lot in their favour. Other than on these points we would not disagree with Gould’s precis of the pros and cons of the different approaches. The thrust of Gould’s paper is to argue for the worldwide use of the NCCLS method for susceptibility testing and here we disagree. We believe that the US-derived method, although having a number of creditable features, is too rigid in its concept to be recommended for use in the UK (or for many other EU countries). Our reasons can be listed:

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Towards a common susceptibility testing method

We have isolated a cDNA clone that codes for human cytochrome b 5 reductase. The cDNA was used to analyse, by Southern‐blot hybridization, DNA isolated from a panel of 11 independent human‐rodent somatic cell hybrids. The results indicate that cytochrome b 5 reductase is encoded by a single gene located on human chromosome 22. Copyright © 1988, Wiley Blackwell. All rights reserved

Ian Phillips

Papers

The effects on ß-lactam susceptibility of phenotypic induction and genotypic derepression of ß-lactamase synthesis

The potential of knockout mouse lines in defining the role of flavin-containing monooxygenases in drug metabolism

Towards a common susceptibility testing method

Cloning and chromosomal mapping of human cytochrome b5 reductase (DIA1).

Aminoglycoside resistance among Enterobacteriaceae and Acinetobacter species