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Biomedical subjects

A E Ling

Publications and source records attributed to A E Ling.

At least 37 records · Page 2Linked to original sources
PubMed1999

Retrospective study of Western blot profiles in immune sera of natural dengue virus infections.

The Western blot (WB) assay was used to determine dengue virus antibodies present in human immune sera arising from recent primary and secondary dengue virus infections in Singapore. Cell lysates of dengue-2 virus-infected C6/36 and Vero cells were used. Antibodies directed against structural proteins of dengue-2 virus including envelope (E, gp60/50), capsid-premembrane (C-PrM, gp35), and premembrane (PrM, gp20) were detected, with antibody against envelope protein being most dominant. Similar WB profiles were detected in both primary and secondary dengue virus infections. The reactivity rate of antibodies to dengue-2 virus proteins was higher in infected Vero cell lysate than in infected C6/36 cell lysate, with the exception of antibodies to nonstructural proteins of NS1 and NS3, which were detected predominantly in infected C6/36 cell lysate. More than 75% of "normal" individuals (with no complaint of recent dengue virus infection) examined had low levels of dengue virus antibodies, but all presented with similar WB profiles as patients with recent dengue virus infections. This finding reflects a high seroprevalence of dengue virus infections and the long lasting nature of E, C-PrM, and PrM antibodies. Results from this study indicate that in natural dengue virus infections, native E, C-PrM, and PrM antigens of dengue virus are immunogenic and elicit long-lasting antibodies.

Animals↗
PubMed1998

Seasonal trends of viral respiratory tract infections in the tropics.

To evaluate the seasonal trends of viral respiratory tract infections in a tropical environment, a retrospective survey of laboratory virus isolation, serology and immunofluorescence microscopy in two large general hospitals in Singapore between September 1990 and September 1994 was carried out. Respiratory tract viral outbreaks, particularly among infants who required hospitalization, were found to be associated mainly with respiratory syncytial (RSV) infections (72%), influenza (11%) and parainfluenza viruses (11%). Consistent seasonal variations in viral infections were observed only with RSV (March-August) and influenza A virus (peaks in June, December-January). The RSV trends were associated with higher environmental temperature, lower relative humidity and higher maximal day-to-day temperature variation. Although the influenza A outbreaks were not associated with meteorological factors, influenza B isolates were positively associated with rainfall. These data support the existence of seasonal trends of viral respiratory tract infections in the tropics.

Adolescent↗
PubMed1998

Gonorrhoea treatment failure and ciprofloxacin resistance.

Ciprofloxacin-resistant strains of Neisseria gonorrhoeae have been on the increase over the past few years in Singapore and worldwide. The aim of this study is to correlate treatment failures with in vitro ciprofloxacin resistance of N. gonorrhoeae. A total of 694 patients attending the Department of STD Control (DSC) clinic in 1996 who were diagnosed to have gonococcal infection confirmed by culture were analysed. Treatment failure rates for ciprofloxacin were determined and the minimum inhibitory concentration (MIC) of ciprofloxacin were traced for all cases of treatment failure. The case notes of all patients who had strains with MICs of ciprofloxacin in the resistant (> or = 1 microg/ml) and less sensitive (0.125-0.5 microg/ml) range were also reviewed to determine the clinical outcome. Ciprofloxacin treatment failure rate was 1.7% (8/461) which was lower than the percentage of ciprofloxacin-resistant strains isolated in the laboratory. Of these 8 cases, 6 were resistant and 2 were less sensitive to ciprofloxacin. Cure rates with ciprofloxacin for resistant and less sensitive strains were 40% and 92% respectively. In conclusion, in vitro resistance to ciprofloxacin may not translate into clinical treatment failure. Clinical treatment failures, on the other hand, are also seen in less sensitive strains.

Anti-Infective Agents↗
PubMed1997

The effect of polyethylene glycol (PEG) on the isolation of Chlamydia trachomatis in H-1 HeLa cells.

One hundred and ninety-six urethral and endocervical swabs were processed for isolation of C. trachomatis, using H-1 HeLa cells on shell vials, in the presence and absence of 7% PEG in the chlamydial overlay medium. The results were divided into three evaluable groups based on the number of inclusions per coverslip in the shell vials without PEG. The number of inclusions were compared with that of PEG-treated cultures using the paired t-test. The ranges for the three evaluable groups were one to ten, 11-100 and 101-1000 inclusions per coverslip. All three groups showed a significant increase (2.8- to 3.8-fold) in the number of inclusion bodies in the PEG-treated cultures compared to the untreated cultures.

Chlamydia trachomatis↗
PubMed1997

CMV colitis masquerading as colon cancer--an unusual presentation of acquired immunodeficiency syndrome.

We present a case-report of a patient with a typical history and a barium enema study diagnostic of right-sided colonic cancer. Laparotomy and right hemicolectomy was carried out. Histological examination revealed Cytomegalovirus (CMV) colitis and the patient was subsequently tested positive for Human immunodeficiency Virus (HIV). Gastrointestinal symptoms are common in patients with Acquired Immune Deficiency Syndrome (AIDS) and up to 10% of all AIDS patients have CMV colitis. The diagnostic criteria for CMV colitis is reviewed. AIDS is likely to become more common and we stress the awareness of this condition as well as the need for preoperative colonoscopy and histological diagnosis in patients with radiological diagnosis of colorectal carcinoma.

AIDS-Related Opportunistic Infections↗
PubMed1997

Surveillance of legionellosis and Legionella bacteria in the built environment in Singapore.

During the period 1986 to 1996, a total of 258 sporadic cases of community-acquired legionellosis was reported, giving a mean annual morbidity rate of 0.9 per 100,000 population. Majority of the cases (91.5%) was serologically diagnosed by the indirect fluorescent antibody (IFA) test against Legionella pneumophila based on single sera with a titre of > or = 1:1024. The others were confirmed by a four-fold increase in IFA titre to a minimum of 1:128 (7.4%) and by culture (1.1%). Cases were reported predominantly among males, ethnic Indians, the elderly and those with concurrent medical conditions. The overall case-fatality rate was 14.7%, with the rate significantly higher among those aged > or = 45 years (21%), smokers (20.4%) and those with concurrent medical conditions (22.5%). Seroepidemiological studies among the healthy population based on an IFA titre of > or = 1:32 showed a prevalence of between 10.3% and 21.9%. Of the various occupational groups investigated, high seroprevalence rates were found in foreign construction workers (52.6%) and occupants of a building investigated for an unusual building-related illness (76.1%). Environmental surveillance of Legionella bacteria showed that 36% of cooling towers, 15% to 19% of decorative fountains and waterfalls and 2% of spa pools were positive. The majority (85%) of environmental isolates was identified as Legionella pneumophila: 54.8% of serogroup 1 and 5% of Pontiac subtype.

Adolescent↗
PubMed1995

PCR as a confirmatory test for human immunodeficiency virus type 1 infection in individuals with indeterminate western blot (immunoblot) profiles.

A combination of two PCR systems which amplify human immunodeficiency virus type 1 (HIV-1) gag and pol DNA was used to elucidate the HIV-1 infection status of a group of individuals screening positive for anti-HIV but having indeterminate Western blot (immunoblot) profiles. The results obtained suggest PCR could be used to resolve such cases.

Blotting, Western↗
PubMed1995

Two cases of lower respiratory tract infection due to Chlamydia pneumonia in Singapore.

Chlamydia pneumoniae, previously known as Chlamydia psittaci strain TWAR, causes both upper and lower respiratory tract infection. We report the first two cases of culture-positive Chlamydia pneumoniae lower respiratory infection in Singapore. Both patients had underlying fibrosing alveolitis and presented with a history of prolonged productive cough and fever. Chlamydia pneumoniae was isolated from the bronchoalveolar lavage fluid in the absence of other pathogens. The patients responded clinically to three weeks of oral doxycycline therapy. Infection due to Chlamydia pneumoniae should be considered when a patient with community-acquired pneumonia fails to respond to the usual standard antimicrobial therapy.

Anti-Bacterial Agents↗
PubMed1995

Dual therapy with doxycycline and ketoprofen compared to doxycycline in the treatment of uncomplicated non-gonococcal urethritis.

The aim of this study was to compare a combination of doxycyline and ketoprofen, and doxycycline alone in treating non-gonococcal urethritis (NGU), with particular emphasis on reducing recurrent or persistent disease. Sixty-five men with first episode acute NGU were enrolled between November 1992 and November 1994. The men were randomly assigned to either the doxycycline plus ketoprofen group, group A (doxycycline 100 mg twice daily for 10 days plus ketoprofen 200 mg daily for 10 days, n = 34), or the doxycycline group, group B (100 mg twice daily for 10 days, n = 31). Out of the 65 patients studied, Chlamydia trachomatis was isolated from 9 patients (13.8%), Ureaplasma urealyticum from 6 patients (9.2%) and Mycoplasma hominis from 2 patients (3.1%). At 6 weeks in group A, 16 patients (47%) were cured, one patient had a recurrence (2.9%), and 4 patients had persistent infection (11.8%). Eleven patients defaulted follow-up (32.4%) and 2 patients were dropped from the trial. In contrast, for group B, 13 patients (42%) were cured, 5 patients (16%) had a recurrence, 2 patients (6.5%) had persistent infection and 3 patients (9.7%) were reinfected. Eight patients (25.8%) defaulted follow-up. At 12 weeks, for group A, 14 patients (41.2%) remained cured, one patient (2.9%) had a recurrence, 4 patients (11.8%) had persistent infection and one patient (2.9%) was reinfected. Twelve patients (35.3%) defaulted follow-up. For group B, 8 patients (25.8%) remained cured, 6 patients (19.4%) had recurrence, 2 patients (6.5%) had persistent infection and 5 patients (16.1%) were reinfected. Ten patients (32.2%) defaulted follow-up. There were no statistically significant differences between the two groups except for patients with recurrent NGU where the difference (1 versus 6 patients) was statistically significant (P = 0.019).

Anti-Bacterial Agents↗
PubMed1995

A comparative study of the Abbott and Murex enzyme immunoassay, and cell culture in the detection of cervical chlamydial infection in female sex workers in Singapore.

Endocervical smears from 200 female sex workers were tested for Chlamydia trachomatis infection using the Abbott and Murex enzyme immunoassay (EIA) kits and the standard cell culture technique to compare the performance of these tests. The Abbott test had a sensitivity, specificity, predictive value of a positive result (PVP) and predictive value of a negative result (PVN) of 83.3%, 97.8%, 78.9% and 98.3% respectively. The corresponding figures for the Murex system were 77.8%, 98.4%, 82.4% and 97.8%; and of the standard culture test were 55.6%, 100% and 95.8%. EIA tests were more sensitive but slightly less specific than cell culture in the detection of Chlamydia trachomatis cervical infection in female sex workers in Singapore.

Bacteriological Techniques↗
PubMed1993

Comparative analysis of the restriction endonuclease profiles of the Dumas and Singapore strains of varicella-zoster virus.

The incidence of varicella in Singapore has been increasing since 1984. In 1991, 17,930 cases were reported in a population of about 3 million. A serological survey completed in 1990 demonstrated that only 43% of the cohort had antibodies to varicella-zoster virus (VZV), indicating inadequate herd immunity. To exclude novel VZV strains, representative VZV isolates from 9 chicken pox and 4 zoster patients were characterised by restriction endonuclease analysis. DNAs were extracted from viral isolates propagated in MRC5 human embryo lung cells and were digested separately with BglII, EcoRI, PstI, SalI, and XbaI enzymes. The cleavage profiles of these VZV strains derived from both chicken pox and zoster lesions revealed no distinct differences. This observation implies that the current upsurge of chicken pox most likely stems from closely related VZV genotypes infecting a susceptible population with insufficient herd immunity. Comparison of the restriction fragments of the Singapore and the Dumas strains revealed polymorphisms of the SalI-D, SalI-E, and XbaI-I fragment lengths, which correlated with variable regions I, II, and III of the VZV genome, thereby representing geographically distinct genotypic variants of VZV.

Chickenpox↗
PubMed1992

Prevalence of varicella-zoster virus infection in Singapore.

The incidence of chickenpox in Singapore has been increasing since 1984. A seroepidemiological survey was conducted in 1989-90 to determine the prevalence of varicella-zoster virus-specific IgG antibody in the healthy population in Singapore aged from 6 months to over 45 years. Overall, 42.8% of 500 samples assayed qualitatively by the ELISA method were positive, with less than one fifth of those aged under 15 years and less than half of the 15-24 year olds possessing antibody to the virus. However, antibody prevalence increased markedly to between 86% and 98% in those over 25 years of age. No significant sex or ethnic difference was noted. The survey confirmed the low herd immunity and the higher susceptibility of the young adult population to varicella infection in a tropical city compared to that of temperate countries.

Adolescent↗
PubMed1990

Clinical and laboratory study of first episode genital herpes in Singapore.

A prospective study of the epidemiology, clinical aspects and laboratory features of first episode genital herpes was carried out in Middle Road Hospital, Singapore between June 1986 and December 1987. A total of 68 patients were studied. There were more women than men in the study population with a female to male ratio of 7.5 to 1. The peak incidence of first episode genital herpes was between 20 and 29 years of age. Specimens from 63 patients yielded positive culture for herpes simplex virus (HSV). HSV-1 was isolated from 21 patients (30.9%), HSV-2 from 41 patients (60.3%) and untyped HSV from one patient (1.5%). True primary genital herpes was diagnosed in 43 patients (68.3%) using a test for complement fixing antibodies to HSV. HSV-1 was found to be the causative agent in 18 (41.9%) of the true primary infections, HSV-2 in 24 (55.8%) and untyped HSV in one (2.3%). In comparison, HSV-1 was isolated in only 2 (10%) of the 20 patients with non-primary first episode genital herpes; HSV-2 was found in 13 patients (65%) and the culture was negative in 5 (25%).

Adolescent↗
PubMed1990

The rationale for the use of diagnostic tests in herpes simplex virus infection.

All suspect herpes simplex lesions should be diagnosed by isolation methods where possible. Rapid tests ulitise antigen detection methods. The enzyme immunoassay method is the most sensitive of these, and the immunofluorescence method has the advantage of being able to type the virus, but has slightly lower sensitivity. Serological methods are only useful to exclude a herpes simplex infection in the past, and to establish a primary infection. They cannot be used to type an infection or give evidence of past infection to a particular type.

Antigens, Viral↗
PubMed1988

Comparison of tube cultures of Madin Darby canine kidney cells with shell-vial cultures after low-speed centrifugation for influenza virus isolation.

The efficacy of isolation of influenza viruses was compared in two systems--conventional tube cultures of Madin Darby canine kidney cells, and shell-vial cultures after low-speed centrifugation. One hundred and fifty eight throat and nasal swabs were inoculated and cultures screened by hemagglutination on days 1, 2, 3 and 5 post-inoculation. Twenty-four shell-vial cultures (15.2%) and 6 tube cultures (3.8%) were positive for influenza virus type B, indicating that shell-vial cultures with low-speed centrifugation are superior to tube cultures for influenza virus type B isolation (p less than 0.005 by McNemar's test for analysis of matched pairs data).

Animals↗