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Biomedical subjects

M L Ling

Publications and source records attributed to M L Ling.

At least 19 recordsLinked to original sources
PubMed2002

An outbreak of multidrug-resistant Salmonella enterica subsp. enterica serotype Typhimurium, DT104L linked to dried anchovy in Singapore.

Multidrug-resistant Salmonella enterica subsp. enterica serotype Typhimurium DT104L was first reported in Singapore from mid-July to mid-October 2000. Salmonella strains isolated from clinical laboratories were submitted to a reference laboratory for serotyping, phage-typing and pulsed-field gel electrophoresis (PFGE) using XbaI restriction endonuclease. An epidemiological investigation was conducted to determine the source of infection and mode of transmission using a structured questionnaire. A total of 33 cases involving mainly infants and toddlers were detected in the 3-month long outbreak. The outbreak strain was of the R-type ACGSTSu, i.e. resistant to ampicillin, chloramphenicol, gentamicin, streptomycin, tetracycline and sulphonamide. PFGE showed all isolates had an indistinguishable pattern, indicating a common source of infection. Consumption of imported dried anchovy was found to be the vehicle of transmission after adjusting for all confounding variables in the case-control study using stepwise logistic regression (OR 25.6; 95% CI 3.9-167.9; P = 0.001). Imported dried seafood should be properly processed, packed, labelled, and thoroughly cooked to prevent transmission of multidrug-resistant S. Typhimurium.

Adolescent↗
PubMed2001

Microsporidial keratoconjunctivitis in a healthy contact lens wearer without human immunodeficiency virus infection.

PURPOSE: To present a rare case of microsporidial keratoconjunctivitis in an otherwise healthy contact lens wearer without human immunodeficiency virus infection who responded to treatment with systemic albendazole and topical fumagillin. DESIGN: Interventional case report. METHOD: A cornea epithelial scraping from a man with unilateral keratoconjunctivitis previously treated with topical steroids was evaluated by modified trichome staining. MAIN OUTCOME MEASURES: The patient was evaluated for his symptoms, visual acuity, clinical observations, and pathologic examination of corneal scrapes. RESULTS: Modified trichome staining of an epithelial corneal scraping revealed pinkish to red organisms characteristic of microsporidia. Results of a human immunodeficiency virus (HIV) enzyme-linked immunosorbent assay test were negative. The symptoms of ocular discomfort and clinical signs of keratoconjunctivitis resolved after 2 months of treatment with albendazole and topical fumagillin. CONCLUSIONS: Ocular infection with microsporidia, although classically occurring in patients with HIV infection, may occur rarely in healthy individuals, especially if previously treated with systemic immune suppression or topical steroids. Microsporidial keratoconjunctivitis should be considered in the differential diagnosis of a contact lens wearer with atypical multifocal diffuse epithelial keratitis.

Adult↗
PubMed2001

Epidemiological analysis of Salmonella enteritidis isolates in Singapore.

OBJECTIVES: Salmonella enteritidis is the most common non-typhoidal Salmonella species isolated in Singapore causing gastroenteritis and occasional bacteremia with secondary complications. The number of S. enteritidis isolates rose in 1993 and since then, it was the commonest Salmonella sp. isolated. In 1997, a total of 139 S. enteritidis was isolated and this comprised 19.2% of all non-typhoidal Salmonella sp. isolated. METHODS: We studied the antimicrobial susceptibilities, phage types and molecular epidemiology of 89 of these S. enteritidis strains. Fifty per cent were stool isolates whilst 33.3% were isolated from blood samples. RESULTS: All the isolates were susceptible to cephalothin, ceftriaxone, ciprofloxacin, aztreonam, gentamicin, amikacin, kanamycin, neomycin, streptomycin and nalidixic acid; whilst 75.3% were resistant to sulphonamide, 15.7% to tetracycline, 7.9% to co-trimoxazole, 6.7% to trimethoprim, 2.2% to ampicillin and 2.2% to chloramphenicol. The most frequent phage types were phage type 4 (64%), followed by phage type 1 (12.4%) and phage type 8 (2.2%). Seventy four of the 89 (83.1%) S. enteritidis isolates analysed by pulsed-field gel electrophoresis showed an indistinguishable pattern A when digested by restriction enzyme Xba I suggesting the presence of a predominant clone of S. enteritidis circulating in Singapore in 1997.

Animals↗
PubMed2001

In vitro activity of moxifloxacin against local bacterial isolates.

INTRODUCTION: The emergence of resistance to common antimicrobials in bacteria has been increasingly reported in various countries. Empirical antimicrobial therapy of various infections would therefore need to be reviewed. The introduction of new fluoroquinolones has created an interest in the use of these as possible agents in the empirical treatment of respiratory tract infections. MATERIALS AND METHODS: The minimum inhibitory concentration (MIC) of the new fluoroquinolone, moxifloxacin, against 400 clinical bacterial isolates was determined by the E-test method. RESULTS: All Streptococcus pneumoniae isolates (penicillin sensitive or resistant) were susceptible to moxifloxacin. Similarly, both beta-lactamase and non beta-lactamase producing Haemophilus influenzae and Moraxella catarrhalis isolates were susceptible to moxifloxacin. As for Enterobacteriaceae, 88.6% of the isolates tested were susceptible to moxifloxacin with MIC < 8 mg/L, but resistance was noted for some of Proteus mirabilis, Klebsiella spp. and Escherichia coli. Enterococci and Acinetobacter baumannii were resistant to moxifloxacin, whilst the anaerobes tested were susceptible to moxifloxacin. CONCLUSION: Moxifloxacin has good in vitro activity against common organisms associated with community and nosocomial infections, with the exception of enterococci, methicillin-resistant Staphylococcus aureus and ciprofloxacin-resistant gram-negative bacteria. There was good anti-anaerobic activity against Bacteroides fragilis and Clostridum spp. Results of this study are consistent with other similar published in vitro studies.

Anti-Infective Agents↗
PubMed2000

Sharps and needlestick injuries: the impact of hepatitis B vaccination as an intervention measure.

INTRODUCTION: This paper studies the epidemiology of sharps and needlestick injuries amongst health care workers and the effectiveness of intervention measures implemented at a regional hospital, Singapore. MATERIALS AND METHODS: A retrospective review of sharps and needlestick injuries among healthcare workers of a regional hospital at Singapore between 1992 and 1997. Various interventions namely education, policy changes and a hospital-wide hepatitis B immunisation programme were reviewed for effectiveness of programmes implementation. RESULTS: Of the 347 reported sharps and needlestick injuries, 45.7% occurred in the nursing staff, 25.1% medical staff, 7.5% health attendants, 5.2% hospital cleaners and 3.7% laboratory technicians. A steady rise in reporting was noted amongst the doctors from 1994 and this correlated with the implementation of educational talks given to new medical staff in May 1993. The number of healthcare workers with no previous history of hepatitis B immunisation decreased significantly from 17 in 1996 to 9 in 1997 (P < 0.001, odds ratio = 1.806 with 95% CI 1.443 to 2.261) after the implementation of the hospital-wide hepatitis B immunisation programme. CONCLUSIONS: Levels of awareness may contribute towards changes seen in the number of reporting of injuries. In our experience, we contend that education and appropriate policy changes towards easier reporting help to decrease sharps and needlestick injuries in healthcare workers. The hospital-wide hepatitis B immunisation programme helped to raise the immune status of the staff so as to reduce the costly prophylactic usage of hepatitis B immunoglobulin.

Allied Health Personnel↗
PubMed2000

A case series of acanthamoeba keratitis in Singapore.

Acanthamoeba keratitis has become an important cause of severe ocular inflammation and visual loss in the past two decades. Its prevalence has been linked to the increasing use of contact lens. Early diagnosis, effective treatment regimes and education on proper contact lens wear are important in the management and prevention of visual loss from this debilitating disease. We described a series of two cases of culture positive acanthamoeba keratitis and their subsequent management.

Acanthamoeba Keratitis↗
PubMed1997

Bacteraemia in the elderly.

The aims of the study were to describe community-acquired and nosocomial bacteraemia in elderly patients and to determine the factors associated with increased mortality in these patients attending a tertiary hospital in Singapore. A consecutive series of 191 patients aged more than 60 years of age admitted in 1995 was studied retrospectively. All of them had positive blood culture results obtained from the Department of Pathology and the case notes were reviewed and entered into a standard clinical protocol. They were analysed for age, sex, place of origin, race, sites of infection, clinical parameters and bacteriology. The mean age of the study population was 75 years (SD = 8.9 years). Bacteraemia was acquired from the community in 57.5% of patients, 33% was nosocomial in origin and 9.5% acquired it in chronic long term care facilities. The common organisms cultured in community-acquired infections were Escherichia coli (26.1%), Klebsiella species (25.4%), Streptococcus species (11.1%), methicillin sensitive Staphylococcus aureus (7.6%) and Proteus mirabilis (4.8%). The common organisms cultured in nosocomial infections were Klebsiella species (19.8%), Enterobacter species (14.6%), E. coli (11.8%), Acinetobacter baumanii (9.2%), methicillin sensitive Staphylococcus aureus (7.9%) and methicillin-resistant Staphylococcus aureus (7.9%). Whilst most cases of bacteraemia were single organism cultures, 13.5% were polymicrobial. The common sources of bacteraemia were chest (27.5%), urinary tract (24.5%), skin (12.5), hepatic (8.8%), gut (4.3%), cardiovascular system (1%) and others (3.6%). In 12.5% of cases, the sources were multiple and in 5.3% of cases, the source could not be identified. Twenty-one per cent of patients with bacteraemia died. The following factors were associated with increased mortality rate: older age (median age of those that died was 78.5 years compared to survivors with a median age of 73 years, P = 0.011), patient's place of origin (patients in nursing home at higher risk of death, P = 0.04), patient's mobility status (immobile patients at higher risk, P = 0.00297), source of bacteraemia--respiratory infection at increased risk of death (P = 0.00009) but urinary tract infection had a better survival rate (P = 0.03935) and multiple sites of infection (patients with multiple sites of infection had higher risk, P = 0.00897). Methicillin-sensitive Staphylococcus aureus bacteraemia was associated with a mortality rate of 35.3%, followed by Klebsiella species 28.6%, Pseudomonas aeruginosa 28.6%, methicillin-resistant Staphylococcus aureus 25%, Proteus mirabilis 25% and E. coli 19.1%. Important clinical parameters which indicated a poor clinical outcome were: high pulse rate, hypotension, increased respiratory rate, low total white cell count, coagulopathy, hypoalbuminaemia and increased creatinine level.

Aged↗
PubMed1996

Molecular biology in medicine: laboratory diagnosis of tuberculosis.

Clinical mycobacteriology has benefited much from the application of molecular biology techniques. Early detection and identification of Mycobacterium tuberculosis are achieved by the combined use of the BACTEC system and deoxyribonucleic acid (DNA) probes. High-performance liquid chromatography is the other alternative used in some laboratories. Polymerase chain reaction is still a research tool because of its many problems and limitations. Other promising techniques for rapid diagnosis of Mycobacterium tuberculosis, for example, the serological diagnosis by enzyme-linked immunosorbent assay (ELISA), the Gen-Probe Amplified Mycobacterium tuberculosis Direct Test, DNA hybridization, the Mycobacteria Growth Indicator Tubes System and the strand displacement amplification system are currently under evaluation. The discovery of drug resistant genes such as katG and apoB has important implications for the development of new tests for the rapid detection of resistance to anti-tuberculous drugs.

Bacteriological Techniques↗
PubMed1996

Haemophilus parainfluenzae infective endocarditis.

Gram-negative endocarditis was uncommon in the past, accounting for 1% to 3% of cases. With the advent of antibiotics, immunosuppressive agents and narcotic abuse, the number has increased to 5% to 10% in the native valves and as high as 17% in the prosthetic valves, with Haemophilus species as the commonest aetiological agent, accounting for about 1% of the cases. We report a case of Haemophilus parainfluenzae endocarditis in a 39-year-old man who presented with heart failure and persistent fever. Echocardiography showed bi-leaflet mitral valve prolapse and severe mitral regurgitation. A small vegetation was seen at the flail anterior valve leaflet. He responded well to 4 weeks of intravenous ampicillin at 9 g/day and 2 weeks of gentamicin at 4 mg/kg/day, and subsequently underwent valve replacement.

Adult↗
PubMed1994

Editing of the mitochondrial small subunit rRNA in Physarum polycephalum.

Post-transcriptional insertion, substitution or deletion of nucleotides in RNA (RNA editing) has been observed in RNAs from a number of organisms but always in messenger RNA or transfer RNA. We report here that the 17S rRNA of the mitochondrial ribosome of Physarum polycephalum is edited at 40 sites with single cytidine insertions. The locations of the editing sites are fairly evenly distributed throughout the RNA and do not correspond to any obvious feature of the primary sequence or secondary structure. In addition to these cytidine editing sites are editing sites in which a nucleotide other than cytidine is inserted. At two sites a uridine is inserted and at two sites adenosine residues are inserted. This is the first report of mixed nucleotide insertional editing. These results imply that the editing mechanism in Physarum may be different from those proposed for the kinetoplastid protozoa.

Animals↗
PubMed1994

Update of systemic antimicrobials: emphasis on oral agents.

There has been a proliferation of antimicrobial agents in the market and we can expect many more new agents to be available for use in the hospital and community later. In the outpatient setting, the number of oral antimicrobial agents are varied, providing greater flexibility in managing community acquired infections. Unfortunately, the extensive use of antimicrobial agents has contributed to the development of resistance of some bacteria to multiple antimicrobials. This paper will review the basis of activity of antimicrobial agents commonly used in the outpatient clinic. The spectrum of antibacterial activity of these agents is discussed in relation to the common organisms encountered in general practice. Guidelines for the control of the development of bacterial antimicrobial resistance are also given.

Administration, Oral↗
PubMed1994

Update of the rapid diagnosis of infectious diseases. I: Bacteria, fungi and parasites.

The application of monoclonal antibodies and DNA probes in the clinical microbiology laboratory has resulted in an array of rapid diagnostic tests. The immunofluorescent assay or enzyme-linked immunoassay is widely used in the rapid diagnosis of bacteria eg Group A streptococcus, Legionella pneumophila, Mycoplasma pneumoniae, Bordetella pertussis; parasites eg Chlamydia tachomatis, Cryptosporidium species; and fungi eg Pneumocystis carinii. The BACTEC system was first introduced to detect bacteraemia pathogens. It has been further developed to detect Mycobacterium species in clinical specimens and this has greatly reduced turn-around time in the laboratory diagnosis of Mycobacterium species. The discovery of the polymerase chain reaction has led to hopes of using it as a potential diagnostic tool in the microbiology laboratory.

Bacterial Infections↗