Mouse Model of Coxiella burnetii Aerosolization.

Coxiella burnetii is mainly transmitted by aerosols and is responsible for multiple-organ lesions. Animal models have shown C. burnetii pathogenicity, but long-term outcomes still need to be clarified. We used a whole-body aerosol inhalation exposure system to mimic the natural route of infection in immunocompetent (BALB/c) and severe combined immunodeficient (SCID) mice. After an initial lung inoculum of 10(4) C. burnetii cells/lung, the outcome, serological response, hematological disorders, and deep organ lesions were described up to 3 months postinfection. C. burnetii-specific PCR, anti-C. burnetii immunohistochemistry, and fluorescent in situ hybridization (FISH) targeting C. burnetii-specific 16S rRNA completed the detection of the bacterium in the tissues. In BALB/c mice, a thrombocytopenia and lymphopenia were first observed, prior to evidence of C. burnetii replication. In all SCID mouse organs, DNA copies increased to higher levels over time than in BALB/c ones. Clinical signs of discomfort appeared in SCID mice, so follow-up had to be shortened to 2 months in this group. At this stage, all animals presented bone, cervical, and heart lesions. The presence of C. burnetii could be attested in situ for all organs sampled using immunohistochemistry and FISH. This mouse model described C. burnetii Nine Mile strain spread using aerosolization in a way that corroborates the pathogenicity of Q fever described in humans and completes previously published data in mouse models. C. burnetii infection occurring after aerosolization in mice thus seems to be a useful tool to compare the pathogenicity of different strains of C. burnetii.

Draft Genome Sequence of Streptomyces specialis Type Strain GW41-1564 (DSM 41924).

Here, we report the draft genome sequence of Streptomyces specialis type strain GW41-1564, which was isolated from soil. This 5.87-Mb genome exhibits a high G+C content of 72.72% and contains 5,486 protein-coding genes.

Yersinia pestis halotolerance illuminates plague reservoirs.

The plague agent Yersinia pestis persists for years in the soil. Two millennia after swiping over Europe and North Africa, plague established permanent foci in North Africa but not in neighboring Europe. Mapping human plague foci reported in North Africa for 70 years indicated a significant location at <3 kilometers from the Mediterranean seashore or the edge of salted lakes named chotts. In Algeria, culturing 352 environmental specimens naturally containing 0.5 to 70 g/L NaCl yielded one Y. pestis Orientalis biotype isolate in a 40 g/L NaCl chott soil specimen. Core genome SNP analysis placed this isolate within the Y. pestis branch 1, Orientalis biovar. Culturing Y. pestis in broth steadily enriched in NaCl indicated survival up to 150 g/L NaCl as L-form variants exhibiting a distinctive matrix assisted laser desorption-ionization time-of-flight mass spectrometry peptide profile. Further transcriptomic analyses found the upregulation of several outer-membrane proteins including TolC efflux pump and OmpF porin implied in osmotic pressure regulation. Salt tolerance of Y. pestis L-form may play a role in the maintenance of natural plague foci in North Africa and beyond, as these geographical correlations could be extended to 31 plague foci in the northern hemisphere (from 15°N to 50°N).

Surface plasmon resonance imaging of pathogens: the Yersinia pestis paradigm.

BACKGROUND: Yersinia pestis, causing deadly plague, is classified as a group A bioterrorism bacterium. Some recent DNA-based methods were used for detection of bioterrorism agents. RESULTS: Y. pestis was used as a model organism to develop an immunosensor based on surface plasmon resonance imaging (SPRi) using monoclonal antibody against Y. pestis F1 antigen. The experimental approach included step-by-step detection of Y. pestis membrane proteins, lysed bacteria, intact bacteria, mock-infected powder and mock-infected clinical specimens. SPRi detected on average 10(6) intact Y. pestis organisms in buffer, in mock-infected powder and in a 1:4 mixture with HEL cells. CONCLUSIONS: This study offers the proof-of-concept of the SPRi-based detection of a human pathogen in both environmental and clinical specimens.

Detection of Rickettsia spp in ticks by MALDI-TOF MS.

BACKGROUND: Matrix Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) has been shown to be an effective tool for the rapid identification of arthropods, including tick vectors of human diseases. METHODOLOGY/PRINCIPAL FINDINGS: The objective of the present study was to evaluate the use of MALDI-TOF MS to identify tick species, and to determine the presence of rickettsia pathogens in the infected Ticks. Rhipicephalus sanguineus and Dermacentor marginatus Ticks infected or not by R. conorii conorii or R. slovaca, respectively, were used as experimental models. The MS profiles generated from protein extracts prepared from tick legs exhibited mass peaks that distinguished the infected and uninfected Ticks, and successfully discriminated the Rickettsia spp. A blind test was performed using Ticks that were laboratory-reared, collected in the field or removed from patients and infected or not by Rickettsia spp. A query against our in-lab arthropod MS reference database revealed that the species and infection status of all Ticks were correctly identified at the species and infection status levels. CONCLUSIONS/SIGNIFICANCE: Taken together, the present work demonstrates the utility of MALDI-TOF MS for a dual identification of tick species and intracellular bacteria. Therefore, MALDI-TOF MS is a relevant tool for the accurate detection of Rickettsia spp in Ticks for both field monitoring and entomological diagnosis. The present work offers new perspectives for the monitoring of other vector borne diseases that present public health concerns.

High-quality genome sequence and description of Bacillus dielmoensis strain FF4(T) sp. nov.

Strain FF4(T) was isolated from the skin flora of a 16-year-old healthy Senegalese female. This strain exhibited a 16S rRNA sequence similarity of 97.5 % with Bacillus fumarioli, the phylogenetically closest species with standing in nomenclature and a poor MALDI-TOF-MS score (1.1 to 1.3) that does not allow any identification. Using a polyphasic study consisting of phenotypic and genomic analyses, strain FF4(T) was Gram-positive, aerobic, rod-shaped, and exhibited a genome of 4,563,381 bp (1 chromosome but no plasmid) with a G + C content of 40.8 % that coded 4,308 protein-coding and 157 RNA genes (including 5 rRNA operons). On the basis of these data, we propose the creation of Bacillus dielmoensis sp. nov.