Considerations for the Use of Phage Therapy in Clinical Practice.

Increasing antimicrobial resistance and medical device-related infections have led to a renewed interest in phage therapy as an alternative or adjunct to conventional antimicrobials. Expanded access and compassionate use cases have risen exponentially but have varied widely in approach, methodology, and clinical situations in which phage therapy might be considered. Large gaps in knowledge contribute to heterogeneity in approach and lack of consensus in many important clinical areas. The Antibacterial Resistance Leadership Group (ARLG) has convened a panel of experts in phage therapy, clinical microbiology, infectious diseases, and pharmacology, who worked with regulatory experts and a funding agency to identify questions based on a clinical framework and divided them into three themes: potential clinical situations in which phage therapy might be considered, laboratory testing, and pharmacokinetic considerations. Suggestions are provided as answers to a series of questions intended to inform clinicians considering experimental phage therapy for patients in their clinical practices.

The African Green Monkey Model of Pneumonic Plague and US Food and Drug Administration Approval of Antimicrobials Under the Animal Rule.

BACKGROUND: Additional treatment options for pneumonic plague, the most severe form of infection by Yersinia pestis, are needed, as past US Food and Drug Administration (FDA) approvals were not based on clinical trials that meet today's standards, and multiple drugs are sought to counter resistance or use in special populations. Due to the sporadic nature of outbreaks and the low number of pneumonic cases of disease, we sought FDA approval of antimicrobials for treatment under the Animal Efficacy Rule, where efficacy can be demonstrated in 1 or more well-characterized animal models that sufficiently represent human disease. METHODS: A model was developed in African green monkeys (AGMs) after challenge with a lethal dose of Y. pestis delivered as an aerosol, in 4 independent studies in 3 laboratories. The primary data points were bacteremia (daily), body temperature and heart rate (continuously monitored by telemetry), and survival. In antimicrobial efficacy studies, human-equivalent doses of gentamicin, ciprofloxacin, levofloxacin, and doxycycline were administered upon fever onset for 10 days. RESULTS: Disease in AGMs was similar to case reports of human disease. Fever was determined to be a reliable sign of disease and selected as a treatment trigger. Gentamicin was 60%-80% effective depending on the dose given to animals. Ciprofloxacin and levofloxacin were found to be >90% efficacious. These data were submitted to FDA and plague indications were approved. Doxycycline was less effective. CONCLUSIONS: The AGM model of pneumonic plague is reproducible, well-characterized, and mimics human disease. It has been used to support plague indications for fluoroquinolones and to test the efficacy of additional antimicrobials.

Effect of Delaying Treatment on Efficacy of Ciprofloxacin and Levofloxacin in the African Green Monkey Model of Pneumonic Plague.

BACKGROUND: Ciprofloxacin and levofloxacin, 2 fluoroquinolone antimicrobials, are ≥90% effective for the treatment of inhalational plague when administered within 2-6 hours of fever onset in African green monkeys (AGM). Based on data in the AGM model, these antimicrobials were approved under the Food and Drug Administration's Animal Efficacy Rule. However, that data did not address the issue of how long treatment with these antimicrobials would remain effective after fever onset. METHODS: The AGM model of pneumonic plague was used to explore the effect of delaying treatment with ciprofloxacin and levofloxacin on efficacy. In 2 studies, AGMs were challenged with inhaled lethal doses of Yersinia pestis. Treatment with ciprofloxacin and levofloxacin was initiated from 0 to up to 30 hours after fever onset. RESULTS: Challenged animals all developed fever within 78 hours and were treated with ciprofloxacin (n = 27) or levofloxacin (n = 29) at various predetermined time points postfever. When administered 10 hours after fever onset, 10 days of ciprofloxacin and levofloxacin treatment remained very effective (90 or 100%, respectively). The efficacy of both antimicrobials declined as treatment initiation was further delayed. Statistical analyses estimated the treatment delay times at which half of the AGMs were no longer expected to survive as 19.7 hours for ciprofloxacin and 26.5 hours for levofloxacin. CONCLUSIONS: This study demonstrates that there is a narrow window following fever onset during which ciprofloxacin and levofloxacin are fully effective treatment options for pneumonic plague in AGMs. Since the timing of disease is similar in humans and AGMs, these AGM data are reasonably likely to predict response times for treatment in humans.

Genetic effects in Drosophila on the potency of diverse general anesthetics: a distinctive pattern of altered sensitivity.

Mutations that influence the sensitivity of an organism to a volatile general anesthetic can be divided into two classes. In one, sensitivity to all other volatile agents is affected to a similar degree. Although this class may contain mutations of interest for understanding anesthesia, it is also likely to contain mutations that merely alter general health. In the second class, mutations confer non-uniform effects on potency (NEP), i.e., larger effects for some volatile anesthetics than for others. Members of this class are of special interest for studies of arousal and its pharmacological suppression because they not only avoid the pitfall of effects on global health, but also imply the existence of drug targets that are preferentially affected by particular agents. In this work, we provide the first systematic investigation of the relative frequency and diversity of NEP mutations in Drosophila. As a first step, we isolated and characterized a set of P element insertion mutations that confer altered sensitivity of the fruit fly to the clinical anesthetic halothane. Then we tested the members of this collection for their effect on the sensitivity of flies to five other volatile agents. Not only do we find that most of the mutations show non-uniform effects, they also share a characteristic arrangement of altered potencies (halothane > >desflurane >or= enflurane approximately isoflurane approximately methoxyflurane > sevoflurane). From this result, although we do not know how direct or indirect are the effects of the mutations, we infer the existence of a biologically relevant target for anesthetic action that has a distinct preference for halothane over other agents. Intriguingly, P element insertions that co-map with several NEP loci have been shown to alter the fly's response to cocaine and ethanol, suggesting that common genetic elements are involved in the response to all three drugs.

Yeast nuclear envelope subdomains with distinct abilities to resist membrane expansion.

Little is known about what dictates the round shape of the yeast Saccharomyces cerevisiae nucleus. In spo7Delta mutants, the nucleus is misshapen, exhibiting a single protrusion. The Spo7 protein is part of a phosphatase complex that represses phospholipid biosynthesis. Here, we report that the nuclear protrusion of spo7Delta mutants colocalizes with the nucleolus, whereas the nuclear compartment containing the bulk of the DNA is unaffected. Using strains in which the nucleolus is not intimately associated with the nuclear envelope, we show that the single nuclear protrusion of spo7Delta mutants is not a result of nucleolar expansion, but rather a property of the nuclear membrane. We found that in spo7Delta mutants the peripheral endoplasmic reticulum (ER) membrane was also expanded. Because the nuclear membrane and the ER are contiguous, this finding indicates that in spo7Delta mutants all ER membranes, with the exception of the membrane surrounding the bulk of the DNA, undergo expansion. Our results suggest that the nuclear envelope has distinct domains that differ in their ability to resist membrane expansion in response to increased phospholipid biosynthesis. We further propose that in budding yeast there is a mechanism, or structure, that restricts nuclear membrane expansion around the bulk of the DNA.

Chromosome cohesion: ring around the sisters?

Sister chromatid cohesion is a key aspect of accurate chromosome transmission during mitosis, yet little is known about the structure of cohesin, the protein complex that links the two sister chromatids. Recent studies shed light on the structure of the cohesin complex, leading to intriguing models that could explain how sister chromatids are held together.