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Biomedical subjects

T K Ng

Publications and source records attributed to T K Ng.

At least 19 recordsLinked to original sources
PubMed2006

Clinical outcomes of bacteremic pneumococcal infections in an area with high resistance.

In a retrospective study designed to gather information in a region with high antimicrobial resistance, the outcomes of 216 episodes of laboratory-confirmed pneumococcal bacteremia treated in Hong Kong between 1995 and 2001 were assessed. The patients had a mean age (+/-standard deviation) of 40+/-33.7 years. In all patients, the clinical diagnosis was confirmed by isolation of Streptococcus pneumoniae from blood (n=216), cerebrospinal fluid (n=7) and/or other sterile sites (n=12). Penicillin nonsusceptibility was found in 37.5% of the isolates (20.8% intermediate and 16.7% resistant). Penicillin nonsusceptibility was not a risk factor for inpatient mortality (p=0.7), nor did it affect duration of fever (p=0.4), requirement for intensive care unit admission (p=0.4) or development of suppurative complications (p=0.2). Advanced age (OR 11.3, 95%CI 4.5-28.2, p<0.01), critical illness (OR 11.3, 95%CI 4.5-28.2, p<0.001) and discordant therapy (OR 4.3, 95%CI 1.7-10.9, p<0.002) involving agents with poor anti-pneumococcal activity (but not penicillins and broad-spectrum beta-lactam agents) were significantly associated with mortality.

Adolescent↗
PubMed2006

Retrospective prevalence of snakebites from Hospital Kuala Lumpur (HKL) (1999-2003).

A hospital based retrospective study of the prevalence of snakebite cases at Hospital Kuala Lumpur was carried out over a five-year period from 1999 to 2003. A total of 126 snakebite cases were recorded. The highest admission for snakebites was recorded in 2001 (29 cases). The majority of cases were admitted for three days or less (79%). Most of the snakebite cases were reported in the 11-30 years age group (52%). The male:female ratio was 3:1. The majority of cases were Malaysians (80%, 101 cases). Of the non-Malaysians, Indonesians constituted the most (56%, 14 cases). Bites occurred most commonly on the lower limbs (49%), followed by upper limbs (45%) and on other parts of the body (6%). No fatal cases were detected and complications were scarce. In 60% (70 cases) the snake could not be identified. Of the four species of snakes that were identified, cobra (both suspected and confirmed) constituted the largest group (25%), followed by viper (10%), python (4%) and sea snake (1%). The most common clinical presentations were pain and swelling, 92% (116 cases). All patients were put on snakebite charts and their vital signs were monitored. Of the snakebite cases, 48% (61 cases) were treated with cloxacillin and 25% (32 cases) were given polyvalent snake antivenom.

Adolescent↗
PubMed2005

Contemporary methicillin-resistant Staphylococcus aureus clones in Hong Kong.

Two hundred non-duplicate methicillin-resistant Staphylococcus aureus (MRSA) isolates causing bacteremia in patients in four major Hong Kong hospitals during the period 2000 to 2001 were characterized by antibiogram, pulsed-field gel electrophoresis (PFGE) using SmaI restriction enzymes, and determination of staphylococcal cassette chromosome mec (SCCmec) types. Nine PFGE types, A to I, were obtained. PFGE type A constituted 50% (99/200) of all isolates and was present in isolates from all four hospitals. PFGE types A to E, had previously been identified as the major types at one of the hospitals from 1988 to 2000. The majority had a resistance profile to tetracycline (T), erythromycin (E), clindamycin (D), gentamicin (G), tobramycin (To), and ciprofloxacin (Ci), and belonged to SCCmec type III; and representatives belonged to clonal complex 239 (CC 239) (MRSA with SCCmec type III and sequence type 239, designated ST 239-MRSA-III). PFGE types F to I were new patterns that had not been previously identified in isolates from Hong Kong. PFGE type F constituted 18% (35/200) of MRSAs, had resistance profile TEGToCi, and belonged to CC 5 (ST 5-MRSA-II). PFGE type G included 13% (26/200) of MRSAs, had resistance profile TECi, and belonged to CC 45 with SCCmec type I or II. PFGE type H had characteristics similar to those of CC 239, while PFGE type I included three isolates, two of which expressed resistance to oxacillin and fusidic acid only. Two of these strains had SCCmec IVa and carried sequence type 389, with a multilocus sequence typing allelic profile of 3-35-19-2-20-26-39. Contemporary MRSAs causing bacteremia in Hong Kong hospitals belong to three clonal complexes (CC 5, CC 45, and CC 239). The most prevalent MRSA clone in Hong Kong belongs to CC 239, with PFGE types A to E and H, SCCmec type III, ST 239, and a resistance profile of TEDGToCi.

Anti-Bacterial Agents↗
PubMed2004

Re-emergence of fatal human influenza A subtype H5N1 disease.

Human disease associated with influenza A subtype H5N1 re-emerged in January, 2003, for the first time since an outbreak in Hong Kong in 1997. Patients with H5N1 disease had unusually high serum concentrations of chemokines (eg, interferon induced protein-10 [IP-10] and monokine induced by interferon gamma [MIG]). Taken together with a previous report that H5N1 influenza viruses induce large amounts of proinflammatory cytokines from macrophage cultures in vitro, our findings suggest that cytokine dysfunction contributes to the pathogenesis of H5N1 disease. Development of vaccines against influenza A (H5N1) virus should be made a priority.

Animals↗
PubMed2004

Evaluation of a peptide-based enzyme immunoassay for anti-SARS coronavirus IgG antibody.

High throughput assays for anti-SARS-CoV IgG antibody detection are need for large-scale epidemiologic studies. The performance of a microplate enzyme immunoassay, DETECT-SARS was evaluated for the detection of anti-SARS-CoV IgG antibody. This assay is based on synthetic peptides derived from the nucleocapsid and spike proteins. The results showed that the assay provided a high degree of sensitivity (95.9%) for convalescent serum samples. The level of specificity was close to 90%, and did not show significant variation among different control groups. The high degree of sensitivity together with the high-throughput nature makes it advantageous as a screening assay for studies where handling of a large number of specimens is required.

Adolescent↗
PubMed2004

Arterial embolisation in intractable primary post-partum haemorrhage: case series.

OBJECTIVE: To evaluate the efficacy and safety of arterial embolisation in the management of intractable primary post-partum haemorrhage. DESIGN. Retrospective case series. SETTING: Regional hospital, Hong Kong. PATIENTS: Nine patients aged 28 to 39 years who were treated for severe primary post-partum haemorrhage between October 2000 and January 2003. INTERVENTION: Emergency transcatheter arterial embolisation. MAIN OUTCOME MEASURES: Clinical outcome and complications. RESULTS: All nine arterial embolisations successfully arrested the haemorrhage. The main cause of primary post-partum haemorrhage was uterine atony. No serious complication arose, although one patient experienced slight numbness of the right leg. Normal menstruation resumed in all patients, except for the one who had had a hysterectomy as initial treatment. One patient became pregnant 1 year after embolisation. Patients were followed up for 10 months. CONCLUSION: In our experience, arterial embolisation is safe and efficacious, and is the treatment of choice for patients with intractable primary post-partum haemorrhage.

Adult↗
PubMed2003

Effectiveness of precautions against droplets and contact in prevention of nosocomial transmission of severe acute respiratory syndrome (SARS).

We did a case-control study in five Hong Kong hospitals, with 241 non-infected and 13 infected staff with documented exposures to 11 index patients with severe acute respiratory syndrome (SARS) during patient care. All participants were surveyed about use of mask, gloves, gowns, and hand-washing, as recommended under droplets and contact precautions when caring for index patients with SARS. 69 staff who reported use of all four measures were not infected, whereas all infected staff had omitted at least one measure (p=0.0224). Fewer staff who wore masks (p=0.0001), gowns (p=0.006), and washed their hands (p=0.047) became infected compared with those who didn't, but stepwise logistic regression was significant only for masks (p=0.011). Practice of droplets precaution and contact precaution is adequate in significantly reducing the risk of infection after exposures to patients with SARS. The protective role of the mask suggests that in hospitals, infection is transmitted by droplets.

Case-Control Studies↗
PubMed2003

Coronavirus as a possible cause of severe acute respiratory syndrome.

BACKGROUND: An outbreak of severe acute respiratory syndrome (SARS) has been reported in Hong Kong. We investigated the viral cause and clinical presentation among 50 patients. METHODS: We analysed case notes and microbiological findings for 50 patients with SARS, representing more than five separate epidemiologically linked transmission clusters. We defined the clinical presentation and risk factors associated with severe disease and investigated the causal agents by chest radiography and laboratory testing of nasopharyngeal aspirates and sera samples. We compared the laboratory findings with those submitted for microbiological investigation of other diseases from patients whose identity was masked. FINDINGS: Patients' age ranged from 23 to 74 years. Fever, chills, myalgia, and cough were the most frequent complaints. When compared with chest radiographic changes, respiratory symptoms and auscultatory findings were disproportionally mild. Patients who were household contacts of other infected people and had older age, lymphopenia, and liver dysfunction were associated with severe disease. A virus belonging to the family Coronaviridae was isolated from two patients. By use of serological and reverse-transcriptase PCR specific for this virus, 45 of 50 patients with SARS, but no controls, had evidence of infection with this virus. INTERPRETATION: A coronavirus was isolated from patients with SARS that might be the primary agent associated with this disease. Serological and molecular tests specific for the virus permitted a definitive laboratory diagnosis to be made and allowed further investigation to define whether other cofactors play a part in disease progression.

Adult↗
PubMed2002

Occurrence of hepatitis E virus IgM, low avidity IgG serum antibodies, and viremia in sporadic cases of non-A, -B, and -C acute hepatitis.

Serum samples were taken from 57 patients with sporadic non-A, -B, and -C (Non A, B, C) acute hepatitis at different times after onset of the disease and tested for the presence of the hepatitis E virus (HEV) RNA, IgM, and low avidity IgG antibodies. The viral antibodies were detected using two ELISA. One assay (GL) was produced using a mixture of recombinant peptides specified by ORF2 and ORF3 of the viral genome. The other was produced with an ORF2 specified peptide, pE2. The latter occurs naturally as homodimer, it is recognized strongly in its dimeric form by human sera and, in the primate model, it confers protection against experimental HEV infection. Nineteen samples were positive for one or more of these acute markers of HEV infection, 14 of which were acute sera with elevated ALT levels and 5 were convalescent sera with normal ALT level. The results showed that icteric phase of sporadic hepatitis lasts for about 17 days and it coincides with a period when viremia is subsiding as HEV antibodies are developing. Viremia was intermittent and all but one of the 5 instances were confined to the icteric phase with elevated ALT levels. On two of these occasions, viremia preceded detection of HEV antibody, on another 2 occasions it was concurrent with the detection of pE2 specific IgM and/or low avidity IgG and only in one case of protracted viremia was the viral genome detected concurrently with avid pE2 IgG antibody. Ten (71%) of the 14 acute sera were reactive for pE2 IgM, eight (57%) were reactive for low avidity pE2 IgG, and six (43%) for the GL IgM. The sensitivity for the diagnosis of acute hepatitis E may be increased to 87% by combining pE2 IgM and viremia. GL IgM was detected later, but persisted for a longer period of time than the pE2 antibodies, and it was the only acute antibody detected in the convalescent sera.

Acute Disease↗
PubMed2001

Subpopulations of neurons in rat substantia nigra display GABA(B)R2 receptor immunoreactivity.

A functional gamma-aminobutyric acid (GABA) B receptor is the first metabotropic receptor known to be composed of two heteromeric subunits, GABA(B)R1 and GABA(B)R2. Our previous report [Neuroscience 99 (2000) 65] has demonstrated that subpopulations of neurons in the rat substantia nigra display distinct patterns of distribution of GABA(B)R1 receptor immunoreactivity. A robust level of GABA(B)R1 receptor is only found in the dopaminergic neurons of the substantia nigra pars compacta (SNc). The objective of the present study was to determine the precise cellular localization of GABA(B)R2 subunit in the rat substantia nigra using double immunofluorescence. Neuropilar elements in the SNc and the substantia nigra pars reticulata (SNr) were found to display GABA(B)R2 immunoreactivity. In addition, the tyrosine hydroxylase-immunoreactive dopaminergic neurons and the parvalbumin-immunoreactive GABAergic neurons in the SNr were also found to display GABA(B)R2 immunoreactivity. The present results thus demonstrate that a functional GABA(B) receptor may be expressed by the dopaminergic neurons in the SNc. It is less clear whether neurons in the SNr express a functional GABA(B) receptor. The present findings have important functional implications in GABA neurotransmission in the substantia nigra.

Animals↗
PubMed2001

Differential expression of GABA(B)R1 and GABA(B)R2 receptor immunoreactivity in neurochemically identified neurons of the rat neostriatum.

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the neostriatum. Functions of GABA are known to mediate GABA(A) and GABA(B) receptors. A functional GABA(B) receptor is known to compose of heteromeric subunits, namely the GABA(B)R1 and GABA(B)R2 subunits. Our previous report (Yung et al. [1999] Brain Res. 830:345-352) has demonstrated that all major subpopulations of striatal neurons express GABA(B)R1 immunoreactivity. The cellular localization of the second subunit of GABA(B) receptor protein, i.e., GABA(B)R2 immunoreactivity, in the rat neostriatum is not yet known. By using a new commercially available specific antibody against GABA(B)R2, immunofluorescence was performed to investigate the cellular expression of GABA(B)R2 in neurochemically identified subpopulations of neurons in the rat neostriatum. Immunoreactivity for GABA(B)R2 was primarily found in the neuropil of the rat neostriatum. Double labeling revealed that those perikarya that expressed immunoreactivity for parvalbumin, choline acetyltransferase, nitric oxide synthase, glutamate receptor two, N-methyl-D-aspartate receptor one, or GABA(A)alpha1 receptor, respectively, did not express GABA(B)R2 immunoreactivity. In addition, perikarya and most of the neuropilar elements in the neostriatum that expressed glutamic acid decarboxylase 67 immunoreactivity were found to be GABA(B)R2-negative. In contrast, immunoreactivity for GABA(B)R1 was found to be expressed by all of the above neuronal subpopulations. Moreover, a vast number of SV2-immunoreactive profiles and a number of tyrosine hydroxylase-immunoreactive profiles in the neuropil of the neostriatum were found to display GABA(B)R2 immunoreactivity. The present results indicate that there is a differential expression of GABA(B)R2 and GABA(B)R1 immunoreactivity in different subpopulations of striatal neurons that are identified by their specific neurochemical markers. Immunoreactivity for GABA(B)R2 is likely to localize in neuropilar elements of the neostriatum that may belong to non-GABAergic elements. These findings provide anatomical evidence of GABA(B)R2 receptor localization in the neostriatum that may have an important functional implication of the GABA(B)-mediated functions in neurons of the neostriatum.

Animals↗
PubMed2001

Co-localization of AMPA-type glutamate receptor immunoreactivity in neurons of the rat subthalamic nucleus.

In order to determine the precise cellular localization of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA)-type glutamate receptor subunit immunoreactivity in the rat subthalamic nucleus, single and double immunofluorescence was performed. Intense level of GluR1, GluR2, GluR2/3 and GluR4 immunoreactivity was found in almost all neurons of the subthalamic nucleus. By double immunofluorescence, the subthalamic neurons in the same sections that displayed a strong immunoreactivity for GluR1 were found to display a robust GluR2 immunoreactivity and the subthalamic neurons that displayed GluR2 immunoreactivity were also found to express GluR4 immunoreactivity. The present results thus demonstrate that individual neurons of the subthalamic nucleus are likely to co-express GluR1 and GluR2, and GluR2 and GluR4 immunoreactivity. The native AMPA channels in the subthalamic neurons may, therefore, be composed of heteromeric subunits. The present results provide information of the neuroanatomical localization of AMPA receptor subunits in neurons of the subthalamic nucleus. The localization of AMPA receptor subunits may be related to functional characteristics of AMPA channels in the subthalamic neurons.

Animals↗
PubMed2001

Risk factors for acquisition of levofloxacin-resistant Streptococcus pneumoniae: a case-control study.

A case-control study was conducted to identify the risk factors associated with levofloxacin-resistant Streptococcus pneumoniae (LRSP) colonization or infection. Twenty-seven case patients (patients with LRSP) were compared with 54 controls (patients with levofloxacin-susceptible S. pneumoniae). Risk factors that were significantly associated with LRSP colonization or infection, according to univariate analysis, included an older age (median age, 75 years for case patients versus 72.5 years for controls), residence in a nursing home (odds ratio [OR], 7.2), history of recent (OR, 4.6) and multiple (OR, 4.4) hospitalizations, prior exposure to fluoroquinolones (OR, 10.6) and beta-lactams (OR, 8.6), presence of chronic obstructive pulmonary disease (COPD; OR, 5.9), and nosocomial origin of the bacteria (OR, 5.7). Multivariate analysis showed that presence of COPD (OR, 10.3), nosocomial origin of the bacteria (OR, 16.2), residence in a nursing home (OR, 7.4), and exposure to fluoroquinolones (OR, 10.7) were independently associated with LRSP colonization or infection. Thus, a distinct group of patients with COPD is the reservoir of LRSP.

Aged↗
PubMed2001

Target site modifications and efflux phenotype in clinical isolates of Streptococcus pneumoniae from Hong Kong with reduced susceptibility to fluoroquinolones.

Ciprofloxacin-susceptible (n = 7) and -resistant (MIC >or=4 mg/L) (n = 15) clinical isolates of Streptococcus pneumoniae from diverse sources in Hong Kong were studied for target site modifications and efflux phenotype. Reserpine-inhibited efflux of ciprofloxacin and/or levofloxacin was common in both susceptible and non-susceptible isolates. The ParC substitutions K137N and/or S79F or Y were associated with increased ciprofloxacin MICS. The GyrA substitution S81F was only found in isolates with full resistance to ciprofloxacin (MIC >or=16 mg/L) and levofloxacin (MIC >or=8 mg/L). Among clinical isolates of S. pneumoniae, accumulation of target site mutations in strains with an efflux mechanism was associated with increasing MICs of fluoroquinolones.

Amino Acid Substitution↗