Hepatic deficiency of the pioneer transcription factor FoxA restricts hepatitis B virus biosynthesis by the developmental regulation of viral DNA methylation.

The FoxA family of pioneer transcription factors regulates hepatitis B virus (HBV) transcription, and hence viral replication. Hepatocyte-specific FoxA-deficiency in the HBV transgenic mouse model of chronic infection prevents the transcription of the viral DNA genome as a result of the failure of the developmentally controlled conversion of 5-methylcytosine residues to cytosine during postnatal hepatic maturation. These observations suggest that pioneer transcription factors such as FoxA, which mark genes for expression at subsequent developmental steps in the cellular differentiation program, mediate their effects by reversing the DNA methylation status of their target genes to permit their ensuing expression when the appropriate tissue-specific transcription factor combinations arise during development. Furthermore, as the FoxA-deficient HBV transgenic mice are viable, the specific developmental timing, abundance and isoform type of pioneer factor expression must permit all essential liver gene expression to occur at a level sufficient to support adequate liver function. This implies that pioneer transcription factors can recognize and mark their target genes in distinct developmental manners dependent upon, at least in part, the concentration and affinity of FoxA for its binding sites within enhancer and promoter regulatory sequence elements. This selective marking of cellular genes for expression by the FoxA pioneer factor compared to HBV may offer the opportunity for the specific silencing of HBV gene expression and hence the resolution of chronic HBV infections which are responsible for approximately one million deaths worldwide annually due to liver cirrhosis and hepatocellular carcinoma.

PGC1α Transcriptional Adaptor Function Governs Hepatitis B Virus Replication by Controlling HBcAg/p21 Protein-Mediated Capsid Formation.

In the human hepatoma cell line Huh7, the coexpression of the coactivators peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), cyclic AMP-responsive element binding protein binding protein (CBP), steroid receptor coactivator 1 (SRC1), and protein arginine methyltransferase 1 (PRMT1) only modestly increase hepatitis B virus (HBV) biosynthesis. However, by utilizing the human embryonic kidney cell line HEK293T, it was possible to demonstrate that PGC1α alone can support viral biosynthesis independently of the expression of additional coactivators or transcription factors. In contrast, additional coactivators failed to support robust HBV replication in the absence of PGC1α. These observations indicate that PGC1α represents a novel adaptor molecule capable of recruiting the necessary transcriptional machinery to the HBV nucleocapsid promoter to modestly enhance viral pregenomic 3.5-kb RNA synthesis. Although this change in transcription is associated with a similar modest change in hepatitis B virus core antigen polypeptide (HBcAg/p21) synthesis, it mediates a dramatic increase in viral capsid production and robust viral replication. Therefore, it is apparent that the synthesis of cytoplasmic HBcAg/p21 above a critical threshold level is required for the efficient assembly of HBV replication-competent viral capsids.IMPORTANCE Hepatitis B virus (HBV) is a major human pathogen, and novel targets for the development of additional therapeutic agents are urgently needed. Here we demonstrate that the coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) serves as a unique adaptor molecule for the recruitment of additional coactivator proteins, which can finely regulate HBV transcription. The consequence of this precise regulation of viral RNA levels by PGC1α is a subtle increase in cytoplasmic HBcAg/p21 polypeptide translation, which shifts the equilibrium from dimer formation dramatically in favor of viral capsid assembly. These findings suggest that both PGC1α and capsid assembly may represent attractive targets for the development of antiviral agents against chronic HBV infection.

Nasal and perirectal colonization of vancomycin sensitive and resistant enterococci in patients of paediatrics ICU (PICU) of tertiary health care facilities.

BACKGROUND: Enterococci normally inhabit the intestinal tract of humans and are also a potential pathogen in causing nosocomial infections. The increase in antibiotic resistance and transfer of antibiotic resistance gene to Staphylococcus aureus (S. aureus) due to co-colonization has increased its importance in research. The aim of the study was to evaluate local epidemiology of nasal and rectal colonization with Enterococcus faecalis (E. faecalis) and Enterococcus faecium (E. faecium) in patients of Paediatrics Intensive Care Unit (PICU) and correlation with clinical and socioeconomic factors. METHODS: The nasal and perirectal swab samples were collected from 110 patients admitted in PICUs of three tertiary care hospitals of Rawalpindi Medical College, Pakistan. The identification of enterococci was done by biochemical tests and by PCR for ddl, vanA and vanB genes. Antibiotic susceptibility testing was performed by disc diffusion and MICs were determined for vancomycin, tetracycline, ciprofloxacin and oxacillin only. RESULTS: Out of 220 nasal and perirectal samples, 09 vancomycin-resistant enterococci (VRE) and 76 vancomycin-susceptible enterococci (VSE), consisting of 40 E. faecalis and 45 E. faecium were isolated. PCR successfully identified both species with ddl primers and VRE with vanA primer. With disc diffusion method, all isolates were resistant to most of the antibiotics tested except linezolid, quinupristin/dalfopristin, teicoplanin and vancomycin. VRE showed resistance to teicoplanin and vancomycin both and none was resistant to linezolid and quinupristin/dalfopristin. Generally, E. faecium isolates were more resistant than E. faecalis. MICs of vancomycin for nasal and perirectal VRE were 512 mg/L and 64 to 512 mg/L respectively. VRE were more in patients with prolonged hospitalization, from urban localities and those having pneumonia. CONCLUSION: Present study reveals high colonization and antibiotic resistance in enterococcal isolates from nasal and perirectal area. Nasal colonization by enterococci in PICU is more alarming as VRE may cause infection and can transfer this resistance gene to other microorganisms like S. aureus.

Peroxisome proliferator-activated receptor γ coactivator family members competitively regulate hepatitis b virus biosynthesis.

Transcriptional coactivators represent critical components of the transcriptional pre-initiation complex and are required for efficient gene activation. Members of the peroxisome proliferator-activated receptor gamma coactivator 1 (PGC1) family differentially regulate hepatitis b virus (HBV) biosynthesis. Whereas PGC1α has been shown to be a potent activator of HBV biosynthesis, PGC1ß only very poorly activates HBV RNA and DNA synthesis in human hepatoma (HepG2) and embryonic kidney (HEK293T) cells. Furthermore, PGC1ß inhibits PGC1α-mediated HBV biosynthesis. These observations suggest that a potential competition between human hepatoma (HepG2) and embryonic kidney (HEK293T) cells PGC1α and PGC1ß for common transcription factor target(s) may regulate HBV transcription and replication in a context and signal transduction pathway dependent manner.

Draft Genome Sequences of Two Methicillin-Resistant Clinical Staphylococcus aureus Isolates.

Here, we report the draft genome sequences of two methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates, hospital-associated perirectal isolate 32S (ST 239) from a colitis tracheostomy patient and community-associated MRSA isolate 42S (ST 772) from a hepatic-splenomegaly patient in Rawalpindi, Pakistan.

Enhancing the Anti-Enterococci Activity of Different Antibiotics by Combining With Metal Oxide Nanoparticles.

BACKGROUND: Enterococci have emerged as more virulent and multidrug-resistant in community and hospital settings. The emergence of vancomycin resistant enterococci (VRE) in hospitals has posed a serious threat to public health. The widespread use of antibiotics to treat VRE infections has resulted in the development of resistant forms of these organisms. OBJECTIVES: Present study deals with the efficacy of antibiotic-nanoparticle combination against clinical isolates of VRE. This study has effectively evaluated the anti-enterococcal activity of metallic nanoparticles and their combination with antibiotics with the aim to search for new biocidal combinations. MATERIALS AND METHODS: Initially, the isolates were identified by various biochemical tests and also by PCR, targeting ddl, vanA and vanB genes. Antibiotic susceptibility testing was carried out by disc diffusion method. Minimum inhibitory concentration (MIC) of both antibiotics and metal nanoparticles against VRE was done using broth dilution method. On the basis of MICs, a combination of both antibiotics and nanoparticles was used by physical mixing of antibiotics and different concentrations of nanoparticles. RESULTS: The MIC of metal nanoparticles were found in the range of 0.31 - 30 mM. The combination of both antibiotics and nanoparticles has effectively reduced the MICs of ciprofloxacin from 16 - 256 µg/mL to 2 - 16 µg/mL, erythromycin 1024 - 2048 µg/mL to 128 - 512 µg/mL, methicillin 32 - 256 µg/mL to 8 - 64 µg/mL and vancomycin 2 - 512 µg/mL to 0.5 - 64 µg/mL. CONCLUSIONS: Among the nanoparticles, ZnO was found as a potent metallic nanoparticle which effectively reduced the MIC upon combination with the antibiotics. The combination exhibited enhanced bactericidal activity against multidrug resistant clinical strains of VRE with dose dependency. Further extensive study on this aspect can prove their beneficial clinical use against resistant pathogens to combat increasing resistance to antibiotics.

Draft Genome Sequence of Methicillin-Resistant Clinical Staphylococcus aureus Isolate 51S (Sequence Type 291).

We report the draft genome sequence of a methicillin-resistant clinical Staphylococcus aureus isolate with a novel spa type and sequence type (ST291), isolated from a renal failure patient in Rawalpindi, Pakistan.

Draft Genome Sequence of a Methicillin-Resistant Staphylococcus aureus ST1413 Strain for Studying Genetic Mechanisms of Antibiotic Resistance.

Here we report the whole draft genome sequence of a methicillin-resistant Staphylococcus aureus ST1413 strain. Determining the distribution and arrangement of various genes associated with drug resistance, toxicity, and diseases will enhance our understanding about its adaptability to thrive in different ecological niches and help in the development of effective treatments for enterotoxigenic staphylococcal infections.