Whole-genome sequencing establishes persistence of biofilm-associated Pseudomonas aeruginosa detected from microbiological surveillance of gastrointestinal endoscopes.

BACKGROUND: An increased incidence of Pseudomonas aeruginosa in microbiological surveillance (MS) cultures from gastrointestinal endoscopes was detected between March 2020 and March 2023 in Tan Tock Seng Hospital Singapore. AIM: To describe the use of whole-genome sequencing (WGS) in this investigation. METHODS: WGS was performed for all P. aeruginosa isolates with pairwise comparison of isolates to assess for genomic linkage. Comprehensive review of reprocessing practices and environmental sampling was performed. FINDINGS: Twenty-two P. aeruginosa isolates were detected from endoscopic MS cultures. Fifteen (68%) isolates were available for WGS. Eighteen pairwise comparisons of isolates were made, of which 10 were found to be genomically linked. One endoscope had P. aeruginosa repeatedly cultured from subsequent MS that were genomically linked and persistent despite repeat endoscopic reprocessing, establishing the persistence of biofilm that could not be eradicated with routine reprocessing. All P. aeruginosa isolates cultured from other different endoscopes were genetically distinct. Investigation into reprocessing practices revealed the use of air/water valves connected to endoscopes during clinical use. Inspection of these valves revealed the presences of cracks and tears. All other environmental samples were negative. CONCLUSION: The WGS findings helped to deprioritize common source contamination and supported the hypothesis of biofilm build-up within endoscopes, leading to repeatedly positive MS cultures that were genomically linked. This was possibly related to incomplete reprocessing of the damaged air/water valves, resulting in biofilm build-up. All faulty valves were changed and subsequently cleaned separately with ultrasonic cleaning followed by sterilization which resolved this incident.

First nosocomial cluster of COVID-19 due to the Delta variant in a major acute care hospital in Singapore: investigations and outbreak response.

OBJECTIVES: The first large nosocomial cluster of coronavirus disease 2019 (COVID-19) in Singapore in April 2021 led to partial closure of a major acute care hospital. This study examined factors associated with infection among patients, staff and visitors; investigated the possible role of aerosol-based transmission; evaluated the effectiveness of BNT162.b2 and mRNA1273 vaccines; and described the successful containment of the cluster. METHODS: Close contacts of patients with COVID-19 and the affected ward were identified and underwent surveillance for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Patient, staff and visitor cohorts were constructed and factors associated with infection were evaluated. Phylogenetic analysis of patient samples was performed. Ward air exhaust filters were tested for SARS-CoV-2. RESULTS: In total, there were 47 cases, comprising 29 patients, nine staff, six visitors and three household contacts. All infections were of the Delta variant. Ventilation studies showed turbulent air flow and swabs from air exhaust filters were positive for SARS-CoV-2. Vaccine breakthrough infections were seen in both patients and staff. Among patients, vaccination was associated with a 79% lower odds of infection with COVID-19 (adjusted odds ratio 0.21, 95% confidence interval 0.05-0.95). CONCLUSIONS: This cluster occurred despite enhancement of infection control measures that the hospital had undertaken at the onset of the COVID-19 pandemic. It was brought under control rapidly through case isolation, extensive contact tracing and quarantine measures, and led to enhanced use of hospital personal protective equipment, introduction of routine rostered testing of inpatients and staff, and changes in hospital infrastructure to improve ventilation within general wards.

An overview of the clinical applications of optical coherence tomography angiography.

Optical coherence tomography angiography (OCTA) has emerged as a novel, non-invasive imaging modality that allows the detailed study of flow within the vascular structures of the eye. Compared to conventional dye angiography, OCTA can produce more detailed, higher resolution images of the vasculature without the added risk of dye injection. In our review, we discuss the advantages and disadvantages of this new technology in comparison to conventional dye angiography. We provide an overview of the current OCTA technology available, compare the various commercial OCTA machines technical specifications and discuss some future software improvements. An approach to the interpretation of OCTA images by correlating images to other multimodal imaging with attention to identifying potential artefacts will be outlined and may be useful to ophthalmologists, particularly those who are currently still unfamiliar with this new technology. This review is based on a search of peer-reviewed published papers relevant to OCTA according to our current knowledge, up to January 2017, available on the PubMed database. Currently, many of the published studies have focused on OCTA imaging of the retina, in particular, the use of OCTA in the diagnosis and management of common retinal diseases such as age-related macular degeneration and retinal vascular diseases. In addition, we describe clinical applications for OCTA imaging in inflammatory diseases, optic nerve diseases and anterior segment diseases. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical applications of this imaging technology.

Hemagglutinin stalk-based universal vaccine constructs protect against group 2 influenza A viruses.

Current influenza virus vaccines contain H1N1 (phylogenetic group 1 hemagglutinin), H3N2 (phylogenetic group 2 hemagglutinin), and influenza B virus components. These vaccines induce good protection against closely matched strains by predominantly eliciting antibodies against the membrane distal globular head domain of their respective viral hemagglutinins. This domain, however, undergoes rapid antigenic drift, allowing the virus to escape neutralizing antibody responses. The membrane proximal stalk domain of the hemagglutinin is much more conserved compared to the head domain. In recent years, a growing collection of antibodies that neutralize a broad range of influenza virus strains and subtypes by binding to this domain has been isolated. Here, we demonstrate that a vaccination strategy based on the stalk domain of the H3 hemagglutinin (group 2) induces in mice broadly neutralizing anti-stalk antibodies that are highly cross-reactive to heterologous H3, H10, H14, H15, and H7 (derived from the novel Chinese H7N9 virus) hemagglutinins. Furthermore, we demonstrate that these antibodies confer broad protection against influenza viruses expressing various group 2 hemagglutinins, including an H7 subtype. Through passive transfer experiments, we show that the protection is mediated mainly by neutralizing antibodies against the stalk domain. Our data suggest that, in mice, a vaccine strategy based on the hemagglutinin stalk domain can protect against viruses expressing divergent group 2 hemagglutinins.

Efficacy of medical therapy in the initial management of acute primary angle closure in Asians.

PURPOSE: Recent studies have advocated the use of laser iridoplasty or paracentesis in the initial management of patients with acute primary angle closure (APAC). The aim of this study was to ascertain the effectiveness of medical treatment consisting of topical and systemic intraocular pressure (IOP)-lowering agents in the initial management of APAC. METHODS: This was an observational case series of consecutive patients presenting with APAC at a Singapore hospital over 2 years. On diagnosis, all subjects received intravenous acetazolamide followed by oral acetazolamide, topical pilocarpine, timolol, and steroid eye drops. Resolution of APAC was defined as IOP <21 mm Hg with no acute symptoms. RESULTS: In all, 134 consecutive APAC subjects were studied. The majority of subjects were Chinese (96.3%) and female (80%), and the mean age was 63.7±9.6 years. The mean presenting IOP was 58±12.7 mm Hg and mean duration of symptoms was 2.8±3.2 days. With medical therapy, APAC attacks resolved within 3, 6, 12, and 24 h in 28 (21.5%), 58 (44.6%), 99 (76.2%), and 116 (89.2%) subjects, respectively. After resolution of APAC, laser iridotomy was performed in 81.6% of the subjects; 16.2% of the subjects underwent cataract extraction. There was failure of resolution of APAC in only 3 subjects (2.2%). No subject suffered any serious side effects as a result of treatment. CONCLUSIONS: Medical therapy resulted in resolution of APAC within 12 h in 76.2% of the subjects and within 24 h in 89.2% of the subjects, showing the effectiveness of medical therapy in the initial management of APAC.

Cerebral hyperperfusion syndrome post-carotid artery stenting.

Cerebral hyperperfusion syndrome is increasingly recognized as a complication in carotid artery stenting for severe internal carotid artery stenosis. This study reviews the cases of hyperperfusion syndrome occurring after this procedure. We reviewed our database of 170 cases of internal carotid artery stenting carried out at our hospital between January 1999 and June 2006. A radiology search was also carried out to identify those who had CT or MRI within 1 month of post-carotid artery stenting. We had four patients who developed cerebral hyperperfusion syndrome. One patient developed cerebral oedema, one patient had petechial intracerebral haemorrhage and two patients had large intracerebral haemorrhages, one of whom died. This gives a risk of 2.3% (95% confidence interval 2.27-2.323). All patients with cerebral haemorrhage presented within 6 h. Both patients with large intracerebral haemorrhage had carotid stenting within 3 weeks after presentation of symptoms and all had critically severe stenosis of 95% or more. In our series, large intracerebral haemorrhage has occurred only in patients who have been treated early. Cerebral hyperperfusion is an uncommon but serious complication post-carotid stenting. Further studies comparing early treatment of endarterectomy and carotid stenting are awaited.

A new flavonol from Sophora tonkinensis.

A new flavonol, tonkinensisol, was isolated from the roots of Sophora tonkinensis, together with three known compounds named as bayin, vitexin and lupeol. Their structures were elucidated on the basis of spectroscopic evidence. Additionally, tonkinensisol showed moderate cytotoxicity suppressing the proliferation of HL-60 cells in vitro.

Visual acuity after acute primary angle closure and considerations for primary lens extraction.

BACKGROUND/AIM: Primary lens extraction has been advocated for acute primary angle closure (APAC), but it is not known if this is warranted in all cases. The aim of this study was to investigate the visual acuity (VA) of APAC eyes shortly after resolution of the acute episode in order to assess the appropriateness of performing such surgery in this condition. METHODS: This was a prospective observational case series. As part of a randomised controlled trial comparing phacoemulsification and laser iridotomy, 135 consecutive APAC subjects over a 2 year period underwent subjective refraction and measurement of Snellen VA once the acute episode had resolved with reduction of intraocular pressure (IOP) and improved corneal clarity. RESULTS: Subjects were predominantly Chinese (95.6%) and female (79.3%), with a mean age of 63.6 (SD 9.6) years. When assessed 1.7 (2.7) days after presentation, the majority of APAC cases (50.4%) had good VA (6/12 or better), with more than a quarter of cases having VA of 6/7.5 or better. Poor VA was associated with duration of symptoms (p = 0.04, OR = 4.1, 95% CI 1.1 to 15.7) and time taken to resolution of APAC (p = 0.04, OR = 2.2, 95% CI 1.02 to 4.6), but not with sex (p = 0.31), age (p = 0.26), duration from presentation to measurement of visual acuity (p = 0.53), or presenting IOP (p = 0.73). CONCLUSION: Within days after APAC, more than half of APAC affected eyes had good VA (6/12 or better). The role of lens extraction in the management of APAC warrants further debate, especially for eyes with good VA.

Intracranial laterally based supratentorial neurenteric cyst.

Neurenteric cysts are rare developmental cysts lined by endodermal derived epithelium. We present the case of a 68-year-old patient presenting with seizures who was found to have an extra-axial low density lesion with associated wall calcification on CT. Aspiration and biopsy of the cyst revealed a neurenteric cyst. Such lesions of the lateral supratentorial convexity are extremely rare and calcification has not been previously reported in these intracranial cysts.

[Determination of tetrandrine in human plasma by high-performance liquid chromatography].

The paper reports the determination of tetrandrine by high performance liquid chromatography (HPLC). A C18 column was used and the mobile phase was methanol-water(80:20) containing 0.03% triethylamine, detective wave was at 282 nm, the internal standard was diazepam, the sample was extracted with ether. The linear range was from 0.289 microgram.ml-1 to 4.618 micrograms.ml-1, the average recovery rate was 95.8%. The coefficients of variation of within-day and day-to-day were less than 5%. This method is simple, rapid and accurate. It can be used in biomedical sample analysis of tetrandrine.

[A study of quality standards for fuyanke granule].

OBJECTIVE: To establish the quality standards for fuyanke(FYK) granule. METHODS: The phellodendron Chinese schneid, polygonum cuspidatum, sieb. et Zucc and glycyrrihza uralensis fisch in FYK granule were identified by thin-layer chromatography(TLC). The contents of berberine were determined by thin-layer chromatographic scanning(TLCs). RESULTS: The average recovery rate was 97.86%, and the relative standard deviation 1.96%. CONCLUSION: The method is simple, accurate and reliable.

Hepatitis B virus variants with lamivudine-related mutations in the DNA polymerase and the 'a' epitope of the surface antigen are sensitive to ganciclovir.

Lamivudine is a new antiviral agent effective against hepatitis B viral (HBV) infections but can result in virus-drug resistance associated with mutations in the conserved 'YM552DD' motif of the HBV DNA polymerase. Due to their overlapping coding regions in the HBV genome, mutations in the DNA polymerase may result in substitutions in the hepatitis B surface antigen (HBsAg), albeit outside the antigenic 'a' epitope. Here we report the identification of a novel type of lamivudine-related mutations located in both the polymerase (YM552DD-->Y1552DD) and the 'a' epitope of HBsAg (Gly130-->Asp130). The same virus carried a HBsAg Gly145-->Arg145 mutation prior to therapy. Both the wild type HBV and lamivudine-related mutants with the Gly145-->Arg145 HBsAg mutation were suppressed following ganciclovir treatment, indicating a beneficial additive effect of both drugs against different forms of HBV mutants.

Comparison of cAMP receptor protein (CRP) and a cAMP-independent form of CRP by Raman spectroscopy and DNA binding.

The secondary structures of the cAMP receptor protein (CRP), a complex of CRP and cAMP, and a cAMP-independent receptor protein mutant (CRP*141 gln) were examined by using Raman spectroscopy. Spectra were obtained from CRP and CRP*141 gln dissolved in 0.3 M NaCl and 30 mM sodium phosphate at protein concentrations of 30-40 mg/mL. CRP and CRP.cAMP1 were compared at lower protein concentrations (10-12 mg/mL) in a solvent of 0.35 M NaCl and 20 mM sodium phosphate. Raman analysis indicates that CRP structural changes induced by one bound cAMP or by the Gly to Gln mutation at residue 141 are small. Spectra of the three CRP samples are essentially identical from 400 to 1900 cm-1. This result differs from the Raman spectroscopy study of CRP and CRP.cAMP2 cocrystals [DeGrazia et al. (1990) Biochemistry 29, 3557]. The latter work showed spectral differences between CRP and CRP.cAMP2 consistent with alterations in the protein conformation. These studies indicate that CRP and CRP.cAMP1 in solution are similar in structure and differ from CRP.cAMP2 cocrystals. Protease digestion and a DNA binding assay were also employed to characterize the wild-type and mutant proteins. CRP*141 gln exhibited the same conformational characteristics of previously reported cAMP-independent mutant proteins. It was sensitive to proteolytic attack in the absence of cAMP, or upon addition of cGMP. In the absence of cAMP, both wild-type and mutant CRPs bound noncooperatively to a 62 bp lac promoter DNA. The equilibrium constants were approximately 10(6) M-1 in 0.1 M Na+. CRP*141 gln had a 2-4-fold higher affinity for the 62 bp DNA than CRP.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of base-pair sequence on the conformations and thermally induced transitions in oligodeoxyribonucleotides containing only AT base pairs.

Tm curves, CD spectra, and kinetics results of the self-complementary DNA dodecamers d(A6T6), d(A3T3A3T3), d(A2T2A2T2A2T2), d(ATATATATATAT), and d(T6A6) demonstrate that the thermal transitions of these oligomers at low salt concentration involve a hairpin intermediate. At high salt concentrations (greater than 0.1 M Na+) only a duplex to denatured-strand transition appears to occur. The temperature and salt-concentration regions of the transitions are very sequence dependent. Alternating-type AT sequences have a lower duplex stability and a greater tendency to form hairpins than sequences containing more nonalternating AT base pairs. Of the two nonalternating sequences, d(T6A6) is significantly less stable than d(A6T6). Both oligomers have CD curves that are very similar to the unusual CD spectrum of poly(dA).poly(dT). The Raman spectra of these two oligomers are also quite similar, but at low temperature, small intensity differences in two backbone modes and three nucleoside vibrations are obtained. The hairpin to duplex transition for the AT dodecamers was examined by salt-jump kinetics measurements. The transition is faster than transitions for palindromic-sequence oligomers containing terminal GC base pairs. Stopped-flow kinetics studies indicate that the transition is second order and has a relatively low activation energy. The reaction rate increases with increasing ionic strength. These results are consistent with a three-step mechanism for the hairpin to duplex reaction: (i) fraying of the hairpin oligomers' terminal base pairs, (ii) a rate-determining bimolecular step involving formation of a cruciform-type intermediate from two hairpin oligomers with open terminal base pairs, and (iii) base-pair migration and formation in the intermediate to give the duplex.

Investigation of the cAMP receptor protein secondary structure by Raman spectroscopy.

Raman spectroscopy was employed to examine the secondary structure of the cAMP receptor protein (CRP). Spectra were obtained over the range 400-1900 cm-1 from solutions of CRP and from CRP-cAMP cocrystals. The spectra of CRP dissolved in 30 mM sodium phosphate and 0.15 M NaCl buffered at either pH 6 or pH 8 or dissolved in 0.15-0.2 M NaCl at protein concentrations of 5, 15, and 30 mg/mL were examined. Estimates of the secondary structure distribution were made by analyzing the amide I region of the spectra (1630-1700 cm-1). CRP secondary structure distributions were essentially the same in either pH and at all protein concentrations examined. The amide I analyses indicated a structural distribution of 44% alpha-helix, 28% beta-strand, 18% turn, and 10% undefined for CRP in solution. Raman spectra of CRP-cAMP cocrystals differed from the spectra of CRP in solution. Some differences were assigned to interfering background bands, whereas other spectral differences were attributed to changes in CRP structure. Differences in the amide III region and in the intensity at 935 cm-1 were consistent with alterations in secondary structure. Analysis of the amide I region of the CRP-cAMP cocrystal spectrum indicated a secondary structure distribution of 37% alpha-helix, 33% beta-strand, 17% turn, and 12% undefined. This result is in agreement with a published secondary structure distribution derived from X-ray analysis of CRP-cAMP cocrystals (37% alpha-helix and 36% beta-strand).(ABSTRACT TRUNCATED AT 250 WORDS)

Solubilities of trace copper and lead species and the complexing capacity of river water in the Linggi River Basin.

Chemical forms of copper and lead in river water of the Linggi River Basin have been fractionated into ASV labile, moderately labile, slowly labile, and inert metal species, based on a previously proposed scheme. Free (hydrated) metal ions were identified by a potentiometric method using an ion selective electrode. Speciation results showed that the soluble copper and lead species occurred mainly in the moderately labile and slowly labile fractions. The speciation results are primarily interpreted in terms of organic interaction due to agricultural based and light industries, and urban discharges. The measured metal complexing capacity (MCC) of the samples reveals consistency of the results with the nature of the discharge. MCC correlates reasonably well with the value from the permanganate test on the river water. In general, the speciation pattern was found to be consistent with the findings of other workers.