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Identification of Histophilus somni by a nanomaterial optical fiber biosensor assay.

ABSTRACT: Histophilus somni is an opportunistic pathogen responsible for respiratory and systemic diseases of cattle and sheep. Rapid and accurate detection of H. somni is essential to distinguish H. somni from other potential pathogens for proper control and treatment of infections. Nanomaterial optical fiber biosensors (NOFS) recognize analyte interactions, such as DNA hybridization, with high specificity and sensitivity, and were applied to detect H. somni DNA in culture and clinical samples. An ionic self-assembled multilayer (ISAM) film was fabricated on a long-period grating optical fiber, and a biotinylated, nucleotide probe complementary to the H. somni 16S rDNA gene was coupled to the ISAM film. Exposure of the ISAM::probe to ?100 killed cells of H. somni strain 2336 without DNA amplification resulted in attenuation of light transmission of ?9.4%. Exposure of the complexed fiber to Escherichia coli or non- H. somni species of Pasteurellaceae reduced light transmission by ?3.4%. Exposure of the ISAM::probe to blood, bronchoalveolar fluid, or spleen from mice or calves infected with H. somni resulted in ?24.3% transmission attenuation. The assay correctly detected all 6 strains of H. somni tested from culture, or tissues from 3 separate mice and calves tested in duplicate. Six heterologous strains (representing 6 genera) reacted at below the cutoff value of 4.87% attenuation of light transmission. NOFS detected at least 100 H. somni cells without DNA amplification within 45?min with high specificity. Although different fibers could vary in signal sensitivity, this did not affect the sensitivity or specificity of the assay.

SUBMITTER: Bandara AB

PROVIDER: S-EPMC6505835 | biostudies-literature | 2018 Nov

REPOSITORIES: biostudies-literature

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Identification of Histophilus somni by a nanomaterial optical fiber biosensor assay.

Bandara Aloka B AB Zuo Ziwei Z McCutcheon Kelly K Ramachandran Siddharth S Heflin James R JR Inzana Thomas J TJ

Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc 20180928 6

Histophilus somni is an opportunistic pathogen responsible for respiratory and systemic diseases of cattle and sheep. Rapid and accurate detection of H. somni is essential to distinguish H. somni from other potential pathogens for proper control and treatment of infections. Nanomaterial optical fiber biosensors (NOFS) recognize analyte interactions, such as DNA hybridization, with high specificity and sensitivity, and were applied to detect H. somni DNA in culture and clinical samples. An ionic ...[more]

PMID: 30264658

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Project description:Histophilus somni, a gram-negative coccobacillus, is an obligate inhabitant of bovine and ovine mucosal surfaces, and an opportunistic pathogen responsible for respiratory disease and other systemic infections in cattle and sheep. Capsules are important virulence factors for many pathogenic bacteria, but a capsule has not been identified on H. somni. However, H. somni does form a biofilm in vitro and in vivo, and the biofilm matrix of most bacteria consists of a polysaccharide.Following incubation of H. somni under growth-restricting stress conditions, such as during anaerobiosis, stationary phase, or in hypertonic salt, a polysaccharide could be isolated from washed cells or culture supernatant. The polysaccharide was present in large amounts in broth culture sediment after H. somni was grown under low oxygen tension for 4-5 days (conditions favorable to biofilm formation), but not from planktonic cells during log phase growth. Immuno-transmission electron microscopy showed that the polysaccharide was not closely associated with the cell surface, and was of heterogeneous high molecular size by gel electrophoresis, indicating it was an exopolysaccharide (EPS). The EPS was a branched mannose polymer containing some galactose, as determined by structural analysis. The mannose-specific Moringa M lectin and antibodies to the EPS bound to the biofilm matrix, demonstrating that the EPS was a component of the biofilm. The addition of N-acetylneuraminic acid to the growth medium resulted in sialylation of the EPS, and increased biofilm formation. Real-time quantitative reverse transcription-polymerase chain reaction analyses indicated that genes previously identified in a putative polysaccharide locus were upregulated when the bacteria were grown under conditions favorable to a biofilm, compared to planktonic cells.H. somni is capable of producing a branching, mannose-galactose EPS polymer under growth conditions favorable to the biofilm phase of growth, and the EPS is a component of the biofilm matrix. The EPS can be sialylated in strains with sialyltransferase activity, resulting in enhanced density of the biofilm, and suggesting that EPS and biofilm formation may be important to persistence in the bovine host. The EPS may be critical to virulence if the biofilm state is required for H. somni to persist in systemic sites.

Project description:Histophilus somni is a Gram-negative bacterial organism that acts as an opportunistic pathogen and is a fastidious member of the Pasteurellaceae family associated with diseases of respiratory, reproductive, cardiac, and other tissues of ruminants. We identified an intervening sequence (IVS) embedded in all five copies of the 23S rRNA gene in the closed genome sequence of the H. somni isolate USDA-ARS-USMARC-63250 that may play an important role in affecting the biology of the organism. Sequencing the RNA from this isolate shows that most of the IVS is cleaved from the transcript, resulting in independent fragments of this structural rRNA that remain functional within the bacterial ribosome. The IVS lies between positions 1170 and 1278 bp of the 3,017-bp gene and exhibits self-complementarity between its 5' and 3' ends that predicts a stem-loop structure interrupting helix-45 in the transcribed 23S rRNA. Excision removes a 94-nucleotide (nt) stem-loop structure that displays an unusual 1-nt 3' end overhang instead of the more typical 2-nt overhang commonly observed at the ends of other excised IVS stem-loops. A comparison with genomes of other H. somni isolates indicates that this IVS is highly conserved, with 31 of 32 complete genomes having similar interruptions of canonical 23S rRNA genes. The potential biological effects of either the released IVS or the fragmentation of the functional 23S rRNA are unknown, but fragmentation may enhance rRNA degradation in ways that contribute to the regulation of gene expression. IMPORTANCE The genome biology underlying H. somni virulence, pathogenicity, environmental adaptability, and broad tissue tropism is understood poorly. We identified a novel H. somni 109-nt IVS stem-loop structure, of which the central portion is excised from the 23S rRNA transcript, resulting in the fragmentation of this rRNA in the H. somni isolate USDA-ARS-USMARC-63250 and the release of a 94-nt structured RNA of unknown function. We determined that this peculiar rRNA biology is widespread among sequenced H. somni isolates, suggesting it has importance to organism biology. The fragmented 23S rRNA molecules remain functional in the ribosome, given that the isolate grows in culture. The structured excised portion of the IVS, presumably due to the action of the endoribonuclease III, has an unusual 1-nt 3' end overhang. This newly discovered H. somni 23S rRNA fragmentation may enhance rRNA degradation providing a previously unrecognized avenue for regulating H. somni biological processes.

Project description:Background and aimHistophilus somni is a Gram-negative bacterium belonging to the Pasteurellaceae family that can cause bovine histophilosis. Histophilus may act as a commensal or opportunistic bacterial cattle pathogen. Comparing genomes of the pathogenic strain 2336 with the non-pathogenic preputial 129Pt isolate revealed some putative virulence factors. The study of the complete genomes of H. somni strains circulating in Russia has never been conducted before. This study aimed to identify genetic features of the H. somni strains isolated in Russia and evaluate the possibility of using strains for vaccine development.Materials and methodsThree strains of H. somni were isolated from different sources. Strain 188-VIEV was isolated from a vaginal swab sample of cattle with endometritis. 532-VIEV and 551-VIEV were cultured from the cryopreserved bull semen samples imported from Canada. Histophilus somni strain ATCC 700025 provided by ATCC (American Type Culture Collection) was also used in the study. DNA extraction was performed using QIAamp DNA Mini Kit (QIAGEN, USA). The whole-genome sequencing of the four strains was performed using Illumina Miseq. The comparison of the resulting sequences with the complete genomes of H. somni 2336 and 129Pt, and detection of the resistance genes and virulence factors, was performed using the ResFinder and Virulence Factor Database web services.ResultsThe genome size of the samples varied from 1.9 to 2.3 Mb. The number of coding sequences varied from 1795 to 2256. The average sequence density was 90%. The total guanine-cytosine (GC) content was 36.8%-37.2%, which coincided with data previously obtained for H. somni. Three out of four studied strains encoded putative virulence factors such as filamentous hemagglutinin homologs, lipooligosaccharide biosynthesis proteins, and proteins involved in iron transport and utilization. The Ser83Ile substitution was identified in the DNA topoisomerase II (gyrA) in H. somni strains 532-VIEV and 551-VIEV cultured from bull semen which led to resistance to fluoroquinolones. The gene (AAC-6-Ia + APH-2'') encoding a bifunctional aminoglycoside modification enzyme was detected in strain 551-VIEV.ConclusionStrains with virulence genes identified could be candidates for designing vaccines and potentially represent antigen sources. The results show that antibiotic-resistant H. somni can be spread with semen used for artificial insemination.

Dataset Information

Identification of Histophilus somni by a nanomaterial optical fiber biosensor assay.

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Identification of Histophilus somni by a nanomaterial optical fiber biosensor assay.

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