Multidrug Intrinsic Resistance Factors in Staphylococcus aureus Identified by Profiling Fitness within High-Diversity Transposon Libraries.

UNLABELLED: Staphylococcus aureus is a leading cause of life-threatening infections worldwide. The MIC of an antibiotic against S. aureus, as well as other microbes, is determined by the affinity of the antibiotic for its target in addition to a complex interplay of many other cellular factors. Identifying nontarget factors impacting resistance to multiple antibiotics could inform the design of new compounds and lead to more-effective antimicrobial strategies. We examined large collections of transposon insertion mutants in S. aureus using transposon sequencing (Tn-Seq) to detect transposon mutants with reduced fitness in the presence of six clinically important antibiotics-ciprofloxacin, daptomycin, gentamicin, linezolid, oxacillin, and vancomycin. This approach allowed us to assess the relative fitness of many mutants simultaneously within these libraries. We identified pathways/genes previously known to be involved in resistance to individual antibiotics, including graRS and vraFG (graRS/vraFG), mprF, and fmtA, validating the approach, and found several to be important across multiple classes of antibiotics. We also identified two new, previously uncharacterized genes, SAOUHSC_01025 and SAOUHSC_01050, encoding polytopic membrane proteins, as important in limiting the effectiveness of multiple antibiotics. Machine learning identified similarities in the fitness profiles of graXRS/vraFG, SAOUHSC_01025, and SAOUHSC_01050 mutants upon antibiotic treatment, connecting these genes of unknown function to modulation of crucial cell envelope properties. Therapeutic strategies that combine a known antibiotic with a compound that targets these or other intrinsic resistance factors may be of value for enhancing the activity of existing antibiotics for treating otherwise-resistant S. aureus strains. IMPORTANCE: Bacterial resistance to every major class of antibiotics has emerged, and we are entering a "post-antibiotic era" where relatively minor infections can lead to serious complications or even death. The utility of an antibiotic for a specific pathogen is limited by both intrinsic and acquired factors. Identifying the repertoire of intrinsic resistance factors of an antibiotic for Staphylococcus aureus, a leading cause of community- and hospital-acquired infections, would inform the design of new drugs as well as the identification of compounds that enhance the activity of existing drugs. To identify factors that limit the activity of antibiotics against S. aureus, we used Tn-Seq to simultaneously assess fitness of transposon mutants in every nonessential gene in the presence of six clinically important antibiotics. This work provides an efficient approach for identifying promising targets for drugs that can enhance susceptibility or restore sensitivity to existing antibiotics.

Environmental and occupational interventions for primary prevention of cancer: a cross-sectorial policy framework.

BACKGROUND: Nearly 13 million new cancer cases and 7.6 million cancer deaths occur worldwide each year; 63% of cancer deaths occur in low- and middle-income countries. A substantial proportion of all cancers are attributable to carcinogenic exposures in the environment and the workplace. OBJECTIVE: We aimed to develop an evidence-based global vision and strategy for the primary prevention of environmental and occupational cancer. METHODS: We identified relevant studies through PubMed by using combinations of the search terms "environmental," "occupational," "exposure," "cancer," "primary prevention," and "interventions." To supplement the literature review, we convened an international conference titled "Environmental and Occupational Determinants of Cancer: Interventions for Primary Prevention" under the auspices of the World Health Organization, in Asturias, Spain, on 17-18 March 2011. DISCUSSION: Many cancers of environmental and occupational origin could be prevented. Prevention is most effectively achieved through primary prevention policies that reduce or eliminate involuntary exposures to proven and probable carcinogens. Such strategies can be implemented in a straightforward and cost-effective way based on current knowledge, and they have the added benefit of synergistically reducing risks for other noncommunicable diseases by reducing exposures to shared risk factors. CONCLUSIONS: Opportunities exist to revitalize comprehensive global cancer control policies by incorporating primary interventions against environmental and occupational carcinogens.

Harmonization of rat fetal external and visceral terminology and classification. Report of the Fourth Workshop on the Terminology in Developmental Toxicology, Berlin, 18-20 April 2002.

This article is a report on the Fourth Berlin Workshop on Terminology in Developmental Toxicology, which was held in April 2002. The workshop is part of an international project in the field of harmonization of terminology in developmental toxicology supported by IPCS. The goal of the Harmonization Project is to ensure better chemical risk assessment. The aim of this Fourth Workshop was to discuss the results of a previously conducted survey on classification of external and visceral anomalies, which are listed in the international glossary, developed under the auspices of IFTS (1997 glossary). The discussions among experts from research institutions, regulatory agencies, and industries were mainly focussed on terms for which there was disagreement and/or uncertainties and the possible reasons. For the illustration of "gray-zone" anomalies, pictures were provided by the participants, which constituted the basis for detailed discussions. There was high agreement that most of the external anomalies (>66%) should be classified as malformations. The few external anomalies for which there was low agreement to classify as a malformation were discussed in detail. None of the external findings, which had in the survey a high agreement, were categorized as a variation.A high agreement regarding the classification of approximately one-third of visceral anomalies was achieved with 34 and 2% being described as malformation and variation, respectively. Most of the visceral findings had low agreement indices and there appeared to be several reasons for this. Thus, the response, 'Not known/not used in the laboratory' (N) was often given. A couple of reasons for difficulties in the classification of an anomaly were that it is only rarely seen upon fetal examination or tends to be species specific. Furthermore, the classification of some anomalies as malformation or variation will remain vague as the decision must be made on a case-by-case basis. Factors affecting the decision include: the availability of appropriate historical control data, description of the grading and severity, whether the anomaly occurs in isolation or whether there is a relationship with an abnormal process, and finally, if the change represents an irreversible one, affecting human and/or animal health. It was concluded that a severity grading, supported by pictures of the anomaly, would be especially helpful to classify certain changes as malformation or as variation. Several of the soft tissue changes were considered likely to be the consequence of functional disorders and thus not strictly developmental anomalies. The possibility to describe a finding as 'Not Malformation' (Unclassified) was agreed upon. As a general conclusion it was emphasized that the observation of a permanent structural change should be considered to be a warning of possible consequences to humans, even when there is no apparent adverse effect on health and survival in adult animals of the species under investigation. Therefore, research is needed to further investigate postnatal consequences. Future collaboration in the field of reproductive and developmental toxicology should aim to further develop and implement a harmonized approach to the interpretation of study data. Therefore, this terminology work will continue in close cooperation with the IPCS Harmonization Project. A Steering Group should be established to facilitate the implementation of harmonized terminology into daily scientific work and its regulatory application.