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Christian Massire

Publications and source records attributed to Christian Massire.

9 recordsLinked to original sources
PubMed2006

Analysis of antibiotic resistance genes in multidrug-resistant Acinetobacter sp. isolates from military and civilian patients treated at the Walter Reed Army Medical Center.

Military medical facilities treating patients injured in Iraq and Afghanistan have identified a large number of multidrug-resistant (MDR) Acinetobacter baumannii isolates. In order to anticipate the impact of these pathogens on patient care, we analyzed the antibiotic resistance genes responsible for the MDR phenotype in Acinetobacter sp. isolates collected from patients at the Walter Reed Army Medical Center (WRAMC). Susceptibility testing, PCR amplification of the genetic determinants of resistance, and clonality were determined. Seventy-five unique patient isolates were included in this study: 53% were from bloodstream infections, 89% were resistant to at least three classes of antibiotics, and 15% were resistant to all nine antibiotics tested. Thirty-seven percent of the isolates were recovered from patients nosocomially infected or colonized at the WRAMC. Sixteen unique resistance genes or gene families and four mobile genetic elements were detected. In addition, this is the first report of bla(OXA-58)-like and bla(PER)-like genes in the U.S. MDR A. baumannii isolates with at least eight identified resistance determinants were recovered from 49 of the 75 patients. Molecular typing revealed multiple clones, with eight major clonal types being nosocomially acquired and with more than 60% of the isolates being related to three pan-European types. This report gives a "snapshot" of the complex genetic background responsible for antimicrobial resistance in Acinetobacter spp. from the WRAMC. Identifying genes associated with the MDR phenotype and defining patterns of transmission serve as a starting point for devising strategies to limit the clinical impact of these serious infections.

Acinetobacter↗
PubMed2006

Identification of Acinetobacter species and genotyping of Acinetobacter baumannii by multilocus PCR and mass spectrometry.

Members of the genus Acinetobacter are ubiquitous in soil and water and are an important cause of nosocomial infections. A rapid method is needed to genotype Acinetobacter isolates to determine epidemiology and clonality during infectious outbreaks. Multilocus PCR followed by electrospray ionization mass spectrometry (PCR/ESI-MS) is a method that uses the amplicon base compositions to genotype bacterial species. In order to identify regions of the Acinetobacter genome useful for this method, we sequenced regions of six housekeeping genes (trpE, adk, efp, mutY, fumC, and ppa) from 267 isolates of Acinetobacter. Isolates were collected from infected and colonized soldiers and civilians involved in an outbreak in the military health care system associated with the conflict in Iraq, from previously characterized outbreaks in European hospitals, and from culture collections. Most of the isolates from the Iraqi conflict were Acinetobacter baumannii (189 of 216 isolates). Among these, 111 isolates had genotypes identical or very similar to those associated with well-characterized A. baumannii isolates from European hospitals. Twenty-seven isolates from the conflict were found to have genotypes representing different Acinetobacter species, including 8 representatives of Acinetobacter genomospecies 13TU and 13 representatives of Acinetobacter genomospecies 3. Analysis by the PCR/ESI-MS method using nine primer pairs targeting the most information-rich regions of the trpE, adk, mutY, fumC, and ppa genes distinguished 47 of the 48 A. baumannii genotypes identified by sequencing and identified at the species level at least 18 Acinetobacter species. Results obtained with our genotyping method were essentially in agreement with those obtained by pulse-field gel electrophoresis analysis. The PCR/ESI-MS genotyping method required 4 h of analysis time to first answer with additional samples subsequently analyzed every 10 min. This rapid analysis allows tracking of transmission for the implementation of appropriate infection control measures on a time scale previously not achievable.

Acinetobacter↗
PubMed2005

SAR by MS: discovery of a new class of RNA-binding small molecules for the hepatitis C virus: internal ribosome entry site IIA subdomain.

A new class of small molecules that bind the HCV RNA IRES IIA subdomain with sub-micromolar affinity is reported. The benzimidazole 'hit' 1 with a KD approximately 100 microM to a 29-mer RNA model of Domain IIA was identified from a 180000-member library using mass spectrometry-based screening methods. Further MS-assisted SAR (structure-activity relationships) studies afforded benzimidazole derivatives with sub-micromolar binding affinity for the IIA RNA construct. The optimized benzimidazoles demonstrated activity in a cellular replicon assay at concentrations comparable to their KD for the RNA target.

Base Sequence↗
PubMed2005

Rapid identification and strain-typing of respiratory pathogens for epidemic surveillance.

Epidemic respiratory infections are responsible for extensive morbidity and mortality within both military and civilian populations. We describe a high-throughput method to simultaneously identify and genotype species of bacteria from complex mixtures in respiratory samples. The process uses electrospray ionization mass spectrometry and base composition analysis of PCR amplification products from highly conserved genomic regions to identify and determine the relative quantity of pathogenic bacteria present in the sample. High-resolution genotyping of specific species is achieved by using additional primers targeted to highly variable regions of specific bacterial genomes. This method was used to examine samples taken from military recruits during respiratory disease outbreaks and for follow up surveillance at several military training facilities. Analysis of respiratory samples revealed high concentrations of pathogenic respiratory species, including Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pyogenes. When S. pyogenes was identified in samples from the epidemic site, the identical genotype was found in almost all recruits. This analysis method will provide information fundamental to understanding the polymicrobial nature of explosive epidemics of respiratory disease.

Bacteria↗
PubMed2005

Recurrent structural RNA motifs, Isostericity Matrices and sequence alignments.

The occurrences of two recurrent motifs in ribosomal RNA sequences, the Kink-turn and the C-loop, are examined in crystal structures and systematically compared with sequence alignments of rRNAs from the three kingdoms of life in order to identify the range of the structural and sequence variations. Isostericity Matrices are used to analyze structurally the sequence variations of the characteristic non-Watson-Crick base pairs for each motif. We show that Isostericity Matrices for non-Watson-Crick base pairs provide important tools for deriving the sequence signatures of recurrent motifs, for scoring and refining sequence alignments, and for determining whether motifs are conserved throughout evolution. The systematic use of Isostericity Matrices identifies the positions of the insertion or deletion of one or more nucleotides relative to the structurally characterized examples of motifs and, most importantly, specifies whether these changes result in new motifs. Thus, comparative analysis coupled with Isostericity Matrices allows one to produce and refine structural sequence alignments. The analysis, based on both sequence and structure, permits therefore the evaluation of the conservation of motifs across phylogeny and the derivation of rules of equivalence between structural motifs. The conservations observed in Isostericity Matrices form a predictive basis for identifying motifs in sequences.

Base Pairing↗
PubMed2005

The Microbial Rosetta Stone Database: a compilation of global and emerging infectious microorganisms and bioterrorist threat agents.

BACKGROUND: Thousands of different microorganisms affect the health, safety, and economic stability of populations. Many different medical and governmental organizations have created lists of the pathogenic microorganisms relevant to their missions; however, the nomenclature for biological agents on these lists and pathogens described in the literature is inexact. This ambiguity can be a significant block to effective communication among the diverse communities that must deal with epidemics or bioterrorist attacks. RESULTS: We have developed a database known as the Microbial Rosetta Stone. The database relates microorganism names, taxonomic classifications, diseases, specific detection and treatment protocols, and relevant literature. The database structure facilitates linkage to public genomic databases. This paper focuses on the information in the database for pathogens that impact global public health, emerging infectious organisms, and bioterrorist threat agents. CONCLUSION: The Microbial Rosetta Stone is available at http://www.microbialrosettastone.com/. The database provides public access to up-to-date taxonomic classifications of organisms that cause human diseases, improves the consistency of nomenclature in disease reporting, and provides useful links between different public genomic and public health databases.

Animals↗
PubMed2005

Rapid identification of emerging pathogens: coronavirus.

We describe a new approach for infectious disease surveillance that facilitates rapid identification of known and emerging pathogens. The process uses broad-range polymerase chain reaction (PCR) to amplify nucleic acid targets from large groupings of organisms, electrospray ionization mass spectrometry for accurate mass measurements of PCR products, and base composition signature analysis to identify organisms in a sample. We demonstrate this principle by using 14 isolates of 9 diverse Coronavirus spp., including the severe acute respiratory syndrome-associated coronavirus (SARS-CoV). We show that this method could identify and distinguish between SARS and other known CoV, including the human CoV 229E and OC43, individually and in a mixture of all 3 human viruses. The sensitivity of detection, measured by using titered SARS-CoV spiked into human serum, was approximate, equals1 PFU/mL. This approach, applicable to the surveillance of bacterial, viral, fungal, or protozoal pathogens, is capable of automated analysis of >900 PCR reactions per day.

Animals↗
PubMed2005

The Microbial Rosetta Stone database: A common structure for microbial biosecurity threat agents.

Infectious microorganisms are important to multiple communities engaged in biodefense and biosecurity, including the agencies responsible for health, defense, law enforcement, agriculture, and drug and food safety. Many agencies have created lists of high priority infectious microorganisms to prioritize research efforts or to formally control the possession and distribution of specific organisms or toxins. However, the biological classification of infectious microorganisms is often complex and ambiguous, leading to uncertainty and confusion for scientists involved in biosecurity work. To address this problem, we created a database, known as the Microbial Rosetta Stone, which resolves many of these ambiguities and includes links to additional information on the microbes, such as gene sequence data and scientific literature. Here we discuss the efforts to coordinate organism names from pathogen lists from various governmental agencies according to biological relatedness and show the overlap of high-priority organisms from multiple agencies. To our knowledge, this is the first comprehensive coordination of pathogens, synonyms, and correct taxonomic names. The organized tables and visual aids are freely available at http://www.microbialrosettastone.com. This website provides a single location where access to information on a broad range of disease-causing organisms and toxins is available to members of the biosecurity community.

Access to Information↗