Fluoroquinolone Resistance Mechanisms of Shigella flexneri Isolated in Bangladesh

Objective

To investigate the prevalence and mechanisms of fluoroquinolone resistance in Shigella species isolated in Bangladesh and to compare with similar strains isolated in China.

Methods

A total of 3789 Shigella isolates collected from Clinical Microbiology Laboratory of icddr,b, during 2004–2010 were analyzed for antibiotic susceptibility. Analysis of plasmids, plasmid-mediated quinolone-resistance genes, PFGE, and sequencing of genes of the quinolone-resistance-determining regions (QRDR) were conducted in representative strains isolated in Bangladesh and compared with strains isolated in Zhengding, China. In addition, the role of efflux-pump was studied by using the efflux-pump inhibitor carbonyl cyanide-m-chlorophenylhydrazone (CCCP).

Results

Resistance to ciprofloxacin in Shigella species increased from 0% in 2004 to 44% in 2010 and S. flexneri was the predominant species. Of Shigella spp, ciprofloxacin resistant (Cip^R) strains were mostly found among S. flexneri (8.3%), followed by S. sonnei (1.5%). Within S. flexneri (n = 2181), 14.5% were resistance to ciprofloxacin of which serotype 2a was predominant (96%). MIC of ciprofloxacin, norfloxacin, and ofloxacin were 6–32 mg/L, 8–32 mg/L, and 8–24 mg/L, respectively in S. flexneri 2a isolates. Sequencing of QRDR genes of resistant isolates showed double mutations in gyrA gene (Ser⁸³Leu, Asp⁸⁷Asn/Gly) and single mutation in parC gene (Ser⁸⁰Ile). A difference in amino acid substitution at position 87 was found between strains isolated in Bangladesh (Asp⁸⁷Asn) and China (Asp⁸⁷Gly) except for one. A novel mutation at position 211 (His→Tyr) in gyrA gene was detected only in the Bangladeshi strains. Susceptibility to ciprofloxacin was increased by the presence of CCCP indicating the involvement of energy dependent active efflux pumps. A single PFGE type was found in isolates from Bangladesh and China suggesting their genetic relatedness.

Conclusions

Emergence of fluoroquinolone resistance in Shigella undermines a major challenge in current treatment strategies which needs to be followed up by using empirical therapeutic strategies.     

IP3R3 silencing induced actin cytoskeletal reorganization through ARHGAP18/RhoA/mDia1/FAK pathway in breast cancer cell lines

Cell morphology is altered in the migration process, and the underlying cytoskeleton remodeling is highly dependent of intracellular Ca²⁺ concentration. Many calcium channels are known to be involved in migration. Inositol 1,4,5-trisphosphate receptor (IP₃R) was demonstrated to be implicated in breast cancer cells migration, but its involvement in morphological changes during the migration process remains unclear. In the present work, we showed that IP₃R3 expression was correlated to cell morphology. IP₃R3 silencing induced rounding shape and decreased adhesion in invasive breast cancer cell lines. Moreover, IP₃R3 silencing decreased ARHGAP18 expression, RhoA activity, Cdc42 expression and ^Y861FAK phosphorylation. Interestingly, IP₃R3 was able to regulate profilin remodeling, without inducing any myosin II reorganization. IP₃R3 silencing revealed an oscillatory calcium signature, with a predominant oscillating profile occurring in early wound repair. To summarize, we demonstrated that IP₃R3 is able to modulate intracellular Ca²⁺ availability and to coordinate the remodeling of profilin cytoskeleton organization through the ARHGAP18/RhoA/mDia1/FAK pathway.     

Mortality amongst Patients with Influenza-Associated Severe Acute Respiratory Illness,South Africa, 2009-2013

Introduction

Data on the burden and risk groups for influenza-associated mortality from Africa are limited. We aimed to estimate the incidence and risk-factors for in-hospital influenza-associated severe acute respiratory illness (SARI) deaths.

Methods

Hospitalised patients with SARI were enrolled prospectively in four provinces of South Africa from 2009–2013. Using polymerase chain reaction, respiratory samples were tested for ten respiratory viruses and blood for pneumococcal DNA. The incidence of influenza-associated SARI deaths was estimated at one urban hospital with a defined catchment population.

Results

We enrolled 1376 patients with influenza-associated SARI and 3% (41 of 1358 with available outcome data) died. In patients with available HIV-status, the case-fatality proportion (CFP) was higher in HIV-infected (5%, 22/419) than HIV-uninfected individuals (2%, 13/620; p = 0.006). CFPs varied by age group, and generally increased with increasing age amongst individuals >5 years (p<0.001). On multivariable analysis, factors associated with death were age-group 45–64 years (odds ratio (OR) 4.0, 95% confidence interval (CI) 1.01–16.3) and ≥65 years (OR 6.5, 95%CI 1.2–34.3) compared to 1–4 year age-group who had the lowest CFP, HIV-infection (OR 2.9, 95%CI 1.1–7.8), underlying medical conditions other than HIV (OR 2.9, 95%CI 1.2–7.3) and pneumococcal co-infection (OR 4.1, 95%CI 1.5–11.2). The estimated incidence of influenza-associated SARI deaths per 100,000 population was highest in children <1 year (20.1, 95%CI 12.1–31.3) and adults aged 45–64 years (10.4, 95%CI 8.4–12.9). Adjusting for age, the rate of death was 20-fold (95%CI 15.0–27.8) higher in HIV-infected individuals than HIV-uninfected individuals.

Conclusion

Influenza causes substantial mortality in urban South Africa, particularly in infants aged <1 year and HIV-infected individuals. More widespread access to antiretroviral treatment and influenza vaccination may reduce this burden.     

Reduced brain levels of DHEAS in hepatic coma patients: significance for increased GABAergic tone in hepatic encephalopathy

Increased neurosteroids with allosteric modulatory activity on GABA(A) receptors such as 3α-5α tertrahydroprogesterone; allopregnanolone (ALLO), are candidates to explain the phenomenon of "increased GABAergic tone" in hepatic encephalopathy (HE). However, it is not known how changes of other GABA(A) receptor modulators such as dehydroepiandrosterone sulfate (DHEAS) contribute to altered GABAergic tone in HE. Concentrations of DHEAS were measured by radioimmunoassay in frontal cortex samples obtained at autopsy from 11 cirrhotic patients who died in hepatic coma and from an equal number of controls matched for age, gender, and autopsy delay intervals free from hepatic or neurological diseases. To assess whether reduced brain DHEAS contributes to increased GABAergic tone, in vitro patch clamp recordings in rat prefrontal cortex neurons were performed. A significant reduction of DHEAS (5.81±0.88 ng/g tissue) compared to control values (9.70±0.79 ng/g, p<0.01) was found. Brain levels of DHEAS in patients with liver disease who died without HE (11.43±1.74 ng/g tissue), and in a patient who died in uremic coma (12.56 ng/g tissue) were within the control range. Increasing ALLO enhances GABAergic tonic currents concentration-dependently, but increasing DHEAS reduces these currents. High concentrations of DHEAS (50 μM) reduce GABAergic tonic currents in the presence of ALLO, whereas reduced concentrations of DHEAS (1 μM) further stimulate these currents. These findings demonstrate that decreased concentrations of DHEAS together with increased brain concentrations of ALLO increase GABAergic tonic currents synergistically; suggesting that reduced brain DHEAS could further increase GABAergic tone in human HE.     

Purification, functional characterization, cloning, and identification of mutants of a seed-specific arabinan hydrolase in Arabidopsis

This work describes the purification and characterization of an enzyme that exhibits arabinan hydrolase activity in seeds of Arabidopsis thaliana. The enzyme, designated XYL3, had an apparent molecular mass of 80 kDa when purified to homogeneity, and was identified using MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) as a putative beta-D-xylosidase that belongs to family 3 of glycoside hydrolases encoded by gene At5g09730. XYL3 hydrolysed synthetic substrates such as p-nitrophenyl-alpha-L-arabinofuranoside and p-nitrophenyl-beta-D-xyloside with similar catalytic efficiency. XYL3 released L-arabinose from (1-->5)-alpha-L-arabinofuranobiose, arabinoxylan, sugar beet arabinan, and debranched arabinan. The enzyme hydrolysed both arabinosyl-substituted side group residues and terminal arabinofuranosyl residues (1-->5)-alpha-linked to the arabinan backbone. This indicates that XYL3 is able to degrade all terminal arabinosyl residues and suggests that it participates in the in-vivo hydrolysis of arabinan. Analysis of gene expression patterns by semi-quantitative RT-PCR, in-situ hybridization and a promoter-GUS fusion demonstrated that AtBX3 was specifically expressed in the seed endosperm at the globular stage of the embryo. Immunolocalization using LM6 anti-arabinan antisera found that arabinan, the XYL3 substrate, was also present in this seed tissue. T-DNA null mutants for AtBX3 were identified. The mutant plants lacked the alpha-L-arabinofuranosidase and beta-D-xylosidase activities corresponding to XYL3. Mutants showed reduced seed size and are delayed in seedling germination compared with the wild type.     

Updating the Role of Probiotics,Prebiotics, and Synbiotics for Tilapia Aquaculture as Leading Candidates for Food Sustainability: a Review

Probiotics and Antimicrobial Proteins - Tilapia production has significantly increased over the past few years due to the adoption of semi-intensive and intensive aquaculture technologies. However,...     

Coevolution Analysis of HIV-1 Envelope Glycoprotein Complex

The HIV-1 Env spike is the main protein complex that facilitates HIV-1 entry into CD4⁺ host cells. HIV-1 entry is a multistep process that is not yet completely understood. This process involves several protein-protein interactions between HIV-1 Env and a variety of host cell receptors along with many conformational changes within the spike. HIV-1 Env developed due to high mutation rates and plasticity escape strategies from immense immune pressure and entry inhibitors. We applied a coevolution and residue-residue contact detecting method to identify coevolution patterns within HIV-1 Env protein sequences representing all group M subtypes. We identified 424 coevolving residue pairs within HIV-1 Env. The majority of predicted pairs are residue-residue contacts and are proximal in 3D structure. Furthermore, many of the detected pairs have functional implications due to contributions in either CD4 or coreceptor binding, or variable loop, gp120-gp41, and interdomain interactions. This study provides a new dimension of information in HIV research. The identified residue couplings may not only be important in assisting gp120 and gp41 coordinate structure prediction, but also in designing new and effective entry inhibitors that incorporate mutation patterns of HIV-1 Env.