Polly H.M. Leung

A Newly Discovered Verotoxin Variant, VT2g, Produced by Bovine Verocytotoxigenic Escherichia coli

ABSTRACT A new verotoxin (VT) variant, designated vt2g, was identified from a bovine strain of verocytotoxigenic Escherichia coli (VTEC) serotype O2:H25. When vt2g was aligned with published sequences of vt2 and vt variants, it exhibited the highest DNA sequence homology with vt2 and vt2c. However, vt2g was not detected by vt2-specific primers and probes, although it was partially neutralized by an antiserum to the VT2A subunit. VT2g was cytotoxic for Vero and HeLa cells and was not activated by mouse intestinal mucus. The vt2g gene was detected in 3 of 409 (0.7%) bovine VTEC strains, including serotypes O2:H25, O2:H45 and Ont:H−.

Ultrasensitive detection of E. coli O157:H7 with biofunctional magnetic bead concentration via nanoporous membrane based electrochemical immunosensor

In this paper, biofunctional magnetic beads were investigated for bacterial cells concentration in a nanoporous alumina membrane based immunosensor for ultra-sensitive detection of E. coli O157:H7. The specific antibody modified magnetic beads were used for concentration of E coli O157:H7 from samples in a small region to enhance sensitivity. The magnetic bead conjugated E. coli O157:H7 cells were then captured on the nanoporous alumina membrane with immobilized antibody via assembled PEG-silane linker. Scanning electron microscopy and fluorescent microscopy were used to demonstrate the magnetic bead-bacteria cell conjugation and bacteria cells magnetic concentration, respectively. Impedance spectroscopy was used to monitor the pure E coli O157:H7 cells and magnetic bead conjugated E coli O157:H7 cells binding on antibody immobilized nanoporous membrane with or without magnetic field. Compared with direct detection of pure bacteria cells, this method via magnetic bead conjugation and concentration demonstrated the ultrasensitivity of 10 CFU/mL for E coli O157:H7 detection.

Mycelium cultivation, chemical composition and antitumour activity of a Tolypocladium sp. fungus isolated from wild Cordyceps sinensis

Aims:  To examine and illustrate the morphological characteristics and growth kinetics of Cs‐HK1, a Tolypocladium fungus, isolated from wild Cordyceps sinensis in solid and liquid cultures, and the major chemical constituents and antitumour effects of Cs‐HK1 mycelium.

Synthesis of 8-hydroxyquinoline derivatives as novel antitumor agents

This letter describes the preparation of quinoline derivatives and their cytotoxic potentials toward human carcinoma cell lines. Among the selected compounds, 8-hydroxy-2-quinolinecarbaldehyde (3) showed the best in vitro cytotoxicity against the human cancer cell lines, including MDA231, T-47D, Hs578t, SaoS2, K562, SKHep1 (with a MTS50 range of 12.5-25 μg/mL) and Hep3B (with a MTS50 range of 6.25±0.034 μg/mL). The in vivo antitumor activity of compound 3 on subcutenaous Hep3B hepatocellular carcinoma xenograft in athymic nude mice was then studied. The results showed that the dose of 10 mg/kg/day of compound 3 with intraperitoneal injection for 9 days totally abolished the growth of the xenograft tumor of Hep3B with no histological damage on vital organs as compared with the control. The experimental results suggested that compound 3 has a good potential as an antitumor agent.

Detection of bacteria with organic electrochemical transistors

Organic electrochemical transistors (OECTs) are successfully used for the detection of bacteria (E. coli O157:H7) in KCl electrolytes. The transfer characteristic of the OECT shifts to higher gate voltage after bacteria are captured on the active layer of the device, which can be attributed to the electrostatic interaction between the bacteria and the transistor. The OECT with a Pt gate electrode shows a voltage shift of up to 55 mV after the capture of bacteria. The influence of the ion concentration of the electrolyte on the device performance is also studied. It is expected that the organic transistors will find promising applications as disposable bacteria sensors.

Water versus antiseptic periurethral cleansing before catheterization among home care patients: A randomized controlled trial

BACKGROUND There is a lack of research studies on periurethral cleansing before catheterization among home care patients. The purpose of this study was to compare the risk of acquiring symptomatic urinary tract infections through the conventional practice of using 0.05% chlorhexidine gluconate (CHG) versus sterile water for periurethral cleansing before insertion of an indwelling urinary catheter. METHODS A randomized controlled trial was used, and subjects were randomly allocated to either the sterile water group or the 0.05% CHG group. Urine specimens for culture were collected 4 times for each subject within 2 weeks. RESULTS Seventy-four urine samples were collected in 20 subjects (sterile water group, 8; 0.05% CHG group, 12). There was no significant difference in colonization count between the 2 groups. In addition, none of the subjects in the 2 groups developed symptomatic bacteriuria. CONCLUSION Using sterile water to clean the periurethral area before catheterization among home care patients will not increase the risk for urinary tract infections.

Impact of Fabric Moisture Transport Properties on Physiological Responses when Wearing Protective Clothing

This purpose of this study was to investigate the impact of fabric moisture transport properties (MTP) on physiological responses when wearing protective clothing. Ten healthy subjects wore two kinds of personal protective equipment (PPE) ensembles and exercised on a treadmill, worked on a computer, and moved a mannequin in an environment that simulated where health carers work. PPE1 consisted of cotton underwear and 100% polyethylene outerwear. PPE2 consisted of cotton underwear with moisture management function and outerwear made of waterproof breathable fabric. The results showed that there were significantly higher cumulative one-way transport capacity, liquid moisture management capacity, and wetting time in PPE2 than in PPE1 underwear. There was significantly higher water vapor permeability (WVP) in PPE2 than in PPE1 outerwear. Deep ear canal temperature, mean skin temperature, and chest wall skin and clothing microclimates (temperature and humidity) were significantly lower with PPE2 than PPE1. The level of plasma oxygen saturation was significantly higher with PPE 2 than PPE1. In the present study, due to the MTP of the fabrics, liquid sweat transferred from the skin surface to the opposite surface quickly and speeded up the processes of evaporation and heat dissipation. It was concluded that the fabrics MTP, when incorporated into protective clothing, is the main physiological mechanism for reduced heat stress.

Detection of methicillin-resistant Staphylococcus aureus using a gold nanoparticle-based colourimetric polymerase chain reaction assay.

We report the use of gold nanoparticles (Au NPs) for direct colourimetric polymerase chain reaction (PCR) detection of methicillin-resistant Staphylococcus aureus (MRSA) in clinical specimens. The colourimetric assay comprised of 2 Au NP probes functionalized with Staphylococcus aureus 23S rRNA- and mecA-specific oligonucleotides. In this study, 72 clinical samples were tested, which included positive blood culture (n=23), urine (n=8), respiratory samples (n=23), as well as wound swabs, pus and body fluid (n=18). Results were recorded qualitatively by direct visual examination and quantitatively by UV-vis spectrophotometry. Using conventional bacterial culture as the gold standard, the sensitivity, specificity, positive predictive value and negative predictive value of this colourimetric assay were 97.14%, 91.89%, 91.89% and 97.14%, respectively, which were comparable to that of commercial real-time PCR assays with a lower cost per reaction. Our assay also showed good agreement with bacterial culture (κ=0.889). The overall detection limit was 500 ng target amplicon, which was comparable to or better than other similar Au NP biosensors. Interestingly, our data revealed the possible relationship between Au NP probe-target hybridization site and assay performance, which might provide hints for design of the Au NP biosensors for nucleic acid detection. To conclude, our study was the first report on the use of Au NP colourimetric assay for direct detection of MRSA in various types of clinical specimens. Further evaluation of the assay is needed in large-scale trials which can also allow for some modifications to streamline the procedures for routine use.

Effects of ammonium feeding on the production of bioactive metabolites (cordycepin and exopolysaccharides) in mycelial culture of a Cordyceps sinensis fungus

Aims: To examine the effects of ammonium feeding on the production of cordycepin (3′‐deoxyadenosine, a nucleoside analogue) and exopolysaccharides (EPS) in mycelial culture of a new Cordyceps sinensis fungus Cs‐HK1.

Effect of storage temperatures and time on the efficacy of multipurpose solutions for contact lenses

Purpose:  To determine the effect of storage time and temperature on the efficacy of four multipurpose solutions for soft contact lenses.