Characterization of florfenicol resistance genes in the coagulase-negative Staphylococcus (CoNS) isolates and genomic features of a multidrug-resistant Staphylococcus lentus strain H29

Background With the wide use of florfenicol to prevent and treat the bacterial infection of domestic animals, the emergence of the florfenicol resistance bacteria is increasingly serious. It is very important to elucidate the molecular mechanism of the bacteria’s resistance to florfenicol. Methods The minimum inhibitory concentration (MIC) levels were determined by the agar dilution method, and polymerase chain reaction was conducted to analyze the distribution of florfenicol resistance genes in 39 CoNS strains isolated from poultry and livestock animals and seafood. The whole genome sequence of one multidrug resistant strain, Staphylococcus lentus H29, was characterized, and comparative genomics analysis of the resistance gene-related sequences was also performed. Results As a result, the isolates from the animals showed a higher resistance rate (23/28, 82.1%) and much higher MIC levels to florfenicol than those from seafood. Twenty-seven animal isolates carried 37 florfenicol resistance genes (including 26 fexA, 6 cfr and 5 fexB genes) with one carrying a cfr gene, 16 each harboring a fexA gene, 5 with both a fexA gene and a fexB gene and the other 5 with both a fexA gene and a cfr gene. On the other hand, all 11 isolates from seafood were sensitive to florfenicol, and only 3 carried a fexA gene each. The whole genome sequence of S. lentus H29 was composed of a chromosome and two plasmids (pH29-46, pH29-26) and harbored 11 resistance genes, including 6 genes [cfr, fexA, ant(6)-Ia, aacA-aphD, mecA and mph(C)] encoded on the chromosome, 4 genes [cfr, fexA, aacA-aphD and tcaA] on pH29-46 and 1 gene (fosD) on pH29-26. We found that the S. lentus H29 genome carried two identical copies of the gene arrays of radC-tnpABC-hp-fexA (5671 bp) and IS256-cfr (2690 bp), of which one copy of the two gene arrays was encoded on plasmid pH29-46, while the other was encoded on the chromosome. Conclusions The current study revealed the wide distribution of florfenicol resistance genes (cfr, fexA and fexB) in animal bacteria, and to the best of our knowledge, this is the first report that one S. lentus strain carried two identical copies of florfenicol resistance-related gene arrays.

Characterization of florfenicol resistance genes in the coagulase-negative Staphylococcus (CoNS) isolates and genomic features of a multidrug-resistant Staphylococcus lentus strain H29

Background: With the wide use of florfenicol to prevent and treat the bacterial infection of domestic animals, the emergence of the florfenicol resistance bacteria is increasingly serious. It is very important to elucidate the molecular mechanism of the bacteria’s resistance to florfenicol. Methods: The minimum inhibitory concentration (MIC) levels was determined by the agar dilution method, and polymerase chain reaction (PCR) was conducted to analyze the distribution of florfenicol resistance genes in 39 CoNS strains isolated from poultry and livestock animals and seafood. The whole genome sequence of one multidrug-resistant strain, Staphylococcus lentus H29, was characterized, and comparative genomics analysis of the resistance gene-related sequences was also performed. Results: As a result, the isolates from the animals showed a higher resistance rate (23/28, 82.1%) and much higher MIC levels of florfenicol than those from seafood. Twenty-seven animal isolates carried 37 florfenicol resistance genes (including 26 fexA , 6 cfr and 5 fexB genes), of which 1 carried a cfr gene, 16 carried a fexA gene, 5 carried both fexA and fexB genes and 5 carried both fexA and cfr genes. On the other hand, all 11 isolates from seafood were sensitive to florfenicol, and only 3 carried a fexA gene each. The whole genome sequence of S. lentus H29 was composed of a chromosome and two plasmids ( pH29-46 , pH29- 26) and harbored 11 resistance genes, including 6 genes [ cfr, fexA, ant(6)-Ia , aac A -aph D , mecA and mph(C) ] encoded on the chromosome, four genes [ cfr, fexA, aac A -aph D and tcaA ] on pH29-46 and one gene ( fosD ) on pH29-26. It was interested to find that the S. lentus H29 genome carried two identical copies of the gene arrays of radC - tnpABC - hp - fexA (5,671 bp) and IS 256 - cfr (2,690 bp), of which one copy of the two gene arrays was encoded on plasmid pH29-46, while the other was encoded on the chromosome. Conclusions : The current study revealed the wide distribution of florfenicol resistance genes ( cfr, fexA and fexB ) in animal bacteria, and to the best of our knowledge, this is the first report of one CoNS strain carrying two identical copies of florfenicol resistance-related gene arrays.

Characterization of florfenicol resistance genes in the coagulase-negative Staphylococcus (CoNS) isolates and genomic features of a multidrug-resistant Staphylococcus lentus strain H29

Background: With the wide use of florfenicol to prevent and treat the bacterial infection of domestic animals, the emergence of the florfenicol resistance bacteria is increasingly serious. It is very important to elucidate the molecular mechanism of the bacteria’s resistance to florfenicol.Methods: The minimum inhibitory concentration (MIC) levels were determined by the agar dilution method, and polymerase chain reaction (PCR) was conducted to analyze the distribution of florfenicol resistance genes in 39 CoNS strains isolated from poultry and livestock animals and seafood. The whole genome sequence of one multidrug resistant strain, Staphylococcus lentus H29, was characterized, and comparative genomics analysis of the resistance gene-related sequences was also performed.Results: As a result, the isolates from the animals showed a higher resistance rate (23/28, 82.1%) and much higher MIC levels to florfenicol than those from seafood. Twenty-seven animal isolates carried 37 florfenicol resistance genes (including 26 fexA, 6 cfr and 5 fexB genes) with one carrying a cfr gene, 16 each harboring a fexA gene, 5 with both a fexA and a fexB genes and the other 5 with both a fexA and a cfr genes. On the other hand, all 11 isolates from seafood were sensitive to florfenicol, and only 3 carried a fexA gene each. The whole genome sequence of S. lentus H29 was composed of a chromosome and two plasmids (pH29-46, pH29-26) and harbored 11 resistance genes, including 6 genes [cfr, fexA, ant(6)-Ia, aacA-aphD, mecA and mph(C)] encoded on the chromosome, 4 genes [cfr, fexA, aacA-aphD and tcaA] on pH29-46 and 1 gene (fosD) on pH29-26. We found that the S. lentus H29 genome carried two identical copies of the gene arrays of radC-tnpABC-hp-fexA (5,671 bp) and IS256-cfr (2,690 bp), of which one copy of the two gene arrays was encoded on plasmid pH29-46, while the other was encoded on the chromosome.Conclusions: The current study revealed the wide distribution of florfenicol resistance genes (cfr, fexA and fexB) in animal bacteria, and to the best of our knowledge, this is the first report that one S. lentus strain carried two identical copies of florfenicol resistance-related gene arrays.

Characterization of florfenicol resistance genes in the coagulase-negative Staphylococcus (CoNS) isolates and genomic features of a multidrug-resistant Staphylococcus lentus strain H29

BackgroundWith the wide use of florfenicol to prevent and treat the bacterial infection of domestic animals, the emergence of the florfenicol resistance bacteria is increasingly serious. It is very important to elucidate the molecular mechanism of the bacteria’s resistance to florfenicol. MethodsThe minimum inhibitory concentration (MIC) levels was determined by the agar dilution method, and polymerase chain reaction (PCR) was conducted to analyze the distribution of florfenicol resistance genes in 39 CoNS strains isolated from poultry and livestock animals and seafood. The whole genome sequence of one multidrug-resistant strain, Staphylococcus lentus H29, was characterized, and comparative genomics analysis of the resistance gene-related sequences was also performed. ResultsAs a result, the isolates from the animals showed a higher resistance rate (23/28, 82.1%) and much higher MIC levels of florfenicol than those from seafood. Twenty-seven animal isolates carried 37 florfenicol resistance genes (including 26 fexA , 6 cfr and 5 fexB genes), of which 1 carried a cfr gene, 16 carried a fexA gene, 5 carried both fexA and fexB genes and 5 carried both fexA and cfr genes. On the other hand, all 11 isolates from seafood were sensitive to florfenicol, and only 3 carried a fexA gene each. The whole genome sequence of S. lentus H29 was composed of a chromosome and two plasmids ( pH29-46 , pH29- 26) and harbored 11 resistance genes, including 6 genes [ cfr, fexA, ant(6)-Ia , aac A -aph D , mecA and mph(C) ] encoded on the chromosome, four genes [ cfr, fexA, aac A -aph D and tcaA ] on pH29-46 and one gene ( fosD ) on pH29-26. It was interested to find that the S. lentus H29 genome carried two identical copies of the gene arrays of radC - tnpABC - hp - fexA (5,671 bp) and IS 256 - cfr (2,690 bp), of which one copy of the two gene arrays was encoded on plasmid pH29-46, while the other was encoded on the chromosome. ConclusionsThe current study revealed the wide distribution of florfenicol resistance genes ( cfr, fexA and fexB ) in animal bacteria, and to the best of our knowledge, this is the first report of one CoNS strain carrying two identical copies of florfenicol resistance-related gene arrays.

Drosophila histone locus body assembly and function involves multiple interactions

By using a histone gene replacement platform in Drosophila, we show that interactions among multiple factors contribute to HLB formation, and that the large number of genes at the endogenous histone locus sequesters available factors from attenuated transgenic histone gene arrays, thereby preventing HLB formation and histone gene expression from these arrays.

Molecular and histologic outcomes following spinal cord injury in spiny mice, Acomys cahirinus

The spiny mouse (Acomys cahirinus) appears to be unique among mammals by showing little scarring or fibrosis after skin or muscle injury, but the Acomys response to spinal cord injury (SCI) is unknown. We tested the hypothesis that Acomys would have molecular and immunohistochemical evidence of reduced spinal inflammation and fibrosis following SCI as compared to C57BL/6 mice (Mus), which similar to all mammals studied to date exhibits spinal scarring following SCI. Initial experiments used two pathway-focused RT-PCR gene arrays (“wound healing” and “neurogenesis”) to evaluate tissue samples from the C2-C6 spinal cord 3-days after a C3/C4 hemi-crush injury (C3Hc). Based on the gene array, specific genes were selected for RT-qPCR evaluation using species-specific primers. The results supported our hypothesis by showing increased inflammation and fibrosis related gene expression (Serpine 1, Plau, Timp1) in Mus as compared to Acomys (P<0.05). RT-qPCR also showed enhanced stem cell and axonal guidance related gene expression (Bmp2, GDNF, Shh) in Acomys compared to Mus (P<0.05). Immunohistochemical evaluation of the spinal lesion at 4-wks post-injury indicated reduced collagen IV immunostaining in Acomys (P<0.05). Glial fibrillary acidic protein (GFAP) and ionized calcium binding adaptor molecule 1(IBA1) immunostaining indicated morphological differences in the appearance of astrocytes and macrophages/microglia in Acomys. Collectively, the molecular and histologic results support the hypothesis that Acomys has reduced spinal inflammation and fibrosis following SCI. We suggest that Acomys may be a useful comparative model to study adaptive responses to SCI.HighlightsSpiny mice (Acomys cahirinus) and C57BL/6 (Mus) were studied after spinal injuryRT-PCR gene arrays suggested different molecular response in AcomysRTq-PCR with species-specific primers showed increased neurogenesis-related signalingHistology indicates reduced scarring and fibrosis in AcomysAcomys may be a useful comparative model to study SCI

The nucleolus

The nucleolus forms at nucleolus organizer regions (NORs) that consist of clusters of repeated rRNA genes. Transcription of the rRNA genes and processing of the transcripts yields the three types of RNAs necessary for the biogenesis of ribosomes. Only subsets of the rRNA genes present in cells are transcribed. The linker histone H1 plays a specific role in the repression of inactive rRNA genes and in many of the other functions of the nucleolus. One of these functions is gene silencing—the nucleolus is surrounded by a zone of heterochromatin consisting of silenced rRNA gene arrays, DNA repeats that flank the centromeres and chromatin domains that include gene-poor, as well as silent, regions of the genome; any gene associating with this zone is subjected to repression. Other functions include the assembly of telomerase, the regulation of p53 stability and the synthesis of 5S and tRNAs whose genes form clusters in the nucleolus.