Displaying publications 1 - 20 of 47 in total

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  1. Tang MY, Cheong YM, Zainuldin T
    Med J Malaysia, 1994 Sep;49(3):217-22.
    PMID: 7845269
    From April 1992 to September 1992, 280 samples of 10 different fresh vegetables, bought from four different market outlets in Kuala Lumpur were examined for the presence of Listeria spp. Most of the market produce were locally grown with the exception of carrots. The isolation procedure was based on the Food & Drug Administration method (modified) used for the detection of Listeria spp. Isolation media used were Listeria Selective medium and LiCl- phenylethanol-Moxalactam agars. The identification of isolates was by means of conventional biochemical tests and API Listeria identification system. Five out of the 280 samples showed Listeria contamination, Listeria monocytogenes was isolated in lettuce, sengkuang (Pachyrrhizus erosus) and selom Oenanthe javanica) and Listeria innocua was isolated from sengkuang (Pachyrrhizus erosus) and pegaga (Hydrocotyle asiatica).
  2. Koay AS, Tay ST, Cheong YM, Yasin RM
    PMID: 8629074
    An IgM dot-immunobinding assay (IgM-DIA) was developed for the diagnosis of scrub typhus infection. The whole cell antigens of Karp, Kato and Gilliam strains of Rickettsia tsutsugamushi were immobilized onto nitrocellulose paper and reacted with patients sera. The presence of IgM R. tsutsugamushi specific antibody in the patient sera could be detected by the observation of a visible brown dot on the nitrocellulose paper. The IgM-DIA has a sensitivity of 90.4% and specificity of 81.4% as compared to the indirect immunoperoxidase test. The IgM-DIA is rapid, simple, cost-effective, does not require microscope or incubator. It is recommended as a rapid screening test for the diagnosis of scrub typhus infection in the field or rural area within the hyperendemic region.
  3. Chin CS, Cheong YM, Wong YH
    Med J Malaysia, 1989 Sep;44(3):194-8.
    PMID: 2696871
    Thirty six clinical isolates of Cryptococcus neoformans were tested for their susceptibility to 5-fluorocytosine and amphotericin B by the determination of minimum inhibitory concentrations and minimum fungicidal concentrations. 22.2% of the isolates were resistant to 5-fluorocytosine and 36.1% indicated 5-fluorocytosine tolerance. All strains were sensitive to amphotericin B.
  4. Dhanoa A, Rajasekaram G, Lean SS, Cheong YM, Thong KL
    J Pathog, 2015;2015:789265.
    PMID: 26819759 DOI: 10.1155/2015/789265
    Introduction. Acinetobacter calcoaceticus-baumannii complex (ACB complex) is a leading opportunistic pathogen in intensive care units (ICUs). Effective control of spread requires understanding of its epidemiological relatedness. This study aims to determine the genetic relatedness and antibiotic susceptibilities of ACB complex in an ICU in Malaysia. Methodology. Pulsed field gel electrophoresis (PFGE), E-test, and disk diffusion were used for isolates characterization. Results. During the study period (December 2011 to June 2012), 1023 patients were admitted to the ICU and 44 ACB complex (blood, n = 21, and blind bronchial aspirates, n = 23) were recovered from 38 ICU patients. Six isolates were from non-ICU patients. Of the 44 ICU isolates, 88.6% exhibited multidrug-resistant (MDR) patterns. There was high degree of resistance, with minimum inhibitory concentration90 (MIC90) of >32 μg/mL for carbapenems and ≥256 μg/mL for amikacin, ampicillin/sulbactam, and cefoperazone/sulbactam. Isolates from the main PFGE cluster were highly resistant. There was evidence of dissemination in non-ICU wards. Conclusion. High number of clonally related MDR ACB complex was found. While the ICU is a likely reservoir facilitating transmission, importation from other wards may be important contributor. Early identification of strain relatedness and implementation of infection control measures are necessary to prevent further spread.
  5. Cheong YM, Ng YP, Chin CS, Thambu J
    Med J Malaysia, 1992 Mar;47(1):44-50.
    PMID: 1387449
    Vaginal discharge is a common complaint of women attending gynaecological clinics. The purpose of this study was to compare the occurrence of commonly implicated microorganisms in vaginal discharge amongst women with or without the complaint, attending a gynaecological and family planning clinic. The association of Gardnerella vaginalis with bacterial vaginosis was also studied. It was found that there were no significant differences between the cases and controls in the isolation rate of Gardnerella vaginalis, Torulopsis glabrata, Ureaplasma urealyticum, Mycoplasma ssp and Group B streptococcus (p greater than 0.05). Only the isolation rate of Candida albicans was significantly higher in the cases than controls (p less than 0.01). However, there was a significant association of G. vaginalis with bacterial vaginosis.
  6. Ahmad N, Cheong YM, Tahir HM
    Malays J Pathol, 1994 Jun;16(1):63-7.
    PMID: 16329578
    Moraxella catarrhalis has gained reputation as a pathogen in the lower respiratory tract especially in patients with underlying chronic lung diseases. It is considered significant when isolated from sputum specimens of adults with respiratory tract infections. A study was carried out to determine the prevalence of Moraxella catarrhalis isolated in sputum specimens and beta-lactamase production of these isolates. Sputum specimens sent to the Bacteriology division, Institute for Medical Research from April 1990 until April 1993 were screened for Moraxella catarrhalis. A total of 1678 sputum specimens were processed and Moraxella catarrhalis was isolated from 15 (0.89%) of the sputum specimens. Six out of 15 (40%) were isolated from patients with chronic lung disease. Eight out of 15 (47%) were beta-lactamase producers. Moraxella catarrhalis isolated in good-quality sputum must not be disregarded and should be looked for especially in patients with chronic obstructive pulmonary disease. Beta-lactamase production should be tested on all isolates so that appropriate treatment can be given. All the isolates in this study were sensitive to cotrimoxazole.
  7. Keah KC, Jegathesan M, Tan SC, Chan SH, Chee OM, Cheong YM, et al.
    Med J Malaysia, 1995 Dec;50(4):291-7.
    PMID: 8668045
    A study to determine contamination of diluted disinfectants at different points in preparation and use in 6 Malaysian hospitals was done using the in-use test. A growth of > or = 250 organisms/ml was taken as an indication of contamination. A total of 342 (7.9%) of the 4316 freshly diluted samples collected from disinfectant bottles in the pharmacy were found to be contaminated. The bacterial isolates obtained were Pseudomonas spp. (42.4%), Moraxella spp. (22.0%), Flavobacterium spp. (11.6%) and Enterobacter spp. (4.2%). Three hundred and sixty seven out of 2278 ward stock were contaminated. The isolates were Pseudomonas spp. (48.6%), Moraxella spp. (17.8%), Acinetobacter spp. (8.9%) and Flavobacterium spp. (7.0%). Of the 9265 disinfectants in-use, 1519 (16.4%) were contaminated. Among the organisms isolated were Pseudomonas spp. (44.3%), Bacillus spp. (13.0%), Enterobacter spp. (9.5%) and Acinetobacter spp. (7.3%). The results indicated a high level of contamination of diluted disinfectants prepared in the pharmacy, stored and used in the wards. This gave a high index of suspicion that recommendations for cleaning of disinfectant containers before refilling, handling of diluted stock solutions and using of disinfectants were not closely adhered to. Standard disinfection procedures outlined in the disinfection and sterilization policy by the Ministry of Health should therefore be followed.
  8. Lim VK, Cheong YM, Suleiman AB
    PMID: 7667716
    A survey on the use of antibiotics in surgical prophylaxis was carried out in seven Malaysian hospitals. Details of antibiotic prescriptions were obtained through questionnaires completed by the prescriber. A total of 430 such prescriptions was analysed. A large number of different antibiotic regimens were used for a variety of surgical procedures. The majority of prescriptions (70%) were issued for procedures where such prophylaxis was probably not necessary. Antibiotics were also often prescribed for durations that were longer than necessary. There is an urgent need to educate surgeons and standardize surgical prophylactic regimens in order to reduce cost and combat the emergence of antibiotic resistance.
  9. Cheong YM, Lim VK, Jegathesan M, Suleiman AB
    Med J Malaysia, 1994 Dec;49(4):317-26.
    PMID: 7674966
    Knowledge of local antimicrobial resistance patterns of bacteria is a valuable guide to empirical antimicrobial therapy. This paper reports the resistance patterns of more than 36,000 bacteria isolated between August 1991 and July 1992 in six Malaysian hospitals and discusses the implications of the results. A customized menu driven software programme was developed to analyse the results. Generally, resistance to the commonly used antibiotics like ampicillin, cloxacillin, cephalosporins, gentamicin, cotrimoxazole and tetracycline was high. Some differences in resistance rate amongst the six hospitals were also noted. Continuous surveillance of antimicrobial resistance in hospitals is encouraged for the effective control of the emergence of antimicrobial resistance.
  10. Keah KC, Jegathesan M, Tan SC, Chan SH, Chee OM, Cheong YM, et al.
    PMID: 9139397
    Basic practices on disinfection was surveyed in 6 hospitals using an observation and interview checklist. Two surveys were done, one pre-(first survey) and one post-intervention (second survey). The disinfection and sterilization policy of the Ministry of Health was not available in 66 (70.2%) and 12 (13%) of the units in the first and second survey respectively. In the second survey, staff in all the units washed disinfectant containers before refilling compared with 41.5% of the units in the first survey. Dilution of disinfectants not recommended was found to be used in the first survey. Storing cleaned and sterile items in disinfectants, using disinfectant as a substitute for sterilization of autoclavable items and not decontaminating spillages were some of the wrong practices observed. Considerable improvements were made in the second survey. Improper usage of disinfectants was also indicated by failure of the in-use test. Rate of failure of disinfectants in-use decreased from 11.6% in the first survey to 5.0% in the second survey. To ensure proper disinfection practices, a comprehensive training program on disinfection is required for nurses and attendants.
  11. Keah KC, Jegathesan M, Tan SC, Chan SH, Che OM, Cheong YM, et al.
    PMID: 8525420
    Awareness of the disinfection and sterilization policy among hospital staff and their knowledge in basic principles and methods of disinfection and sterilization were studied before and after intervention using a self-administered questionnaire. Survey results showed that awareness (56.2%) before intervention was unsatisfactory. The nurses were more aware of the policy than other groups of medical personnel. Those unaware of the policy perform duties from memory or verbal instructions. A significant increase in awareness to 73.3% was observed after intervention (p < 0.05). Knowledge on methods of decontamination, disinfection and sterilization of equipment varies widely from 28.8% to 90.1%. 23.1% were unaware of the temperature used for sterilization while 72.4% did not know how containers of disinfectant should be refill. Only 14.7% knew the recommended method for washing containers. With education improvement was observed. The average knowledge improved from 44.4% to 57.3%. Our results indicated that continuous in-service education is needed to improve, supplement and update knowledge in this field after basic training. In addition orientation programs for new staff should also be aimed at creating awareness and providing information on guidelines and policies related to their duties.
  12. Lim VK, Cheong YM, Suleiman AB
    Singapore Med J, 1993 Dec;34(6):525-8.
    PMID: 8153716
    A prospective survey of antibiotic prescribing patterns in six Ministry of Health general hospitals in Malaysia was undertaken. Information on antibiotic prescriptions including the types of antibiotics used and the purposes for prescription was obtained through the use of questionnaires. A total of 1,918 antibiotic prescriptions were available for analysis. About two-thirds of prescriptions were for therapeutic purposes. The most common infections treated were lower respiratory infection (31%), followed by skin and soft tissue infection (17%), and urinary tract infection (8%). Only 20% of the therapeutic prescriptions were based on microbiological test results. Prophylactic prescriptions were issued for a variety of indications, the most common being toilet and suture of wounds. Only 5% of prophylactic prescriptions were of less than 3 days duration. There was great diversity in antibiotics and antibiotic regimens employed. It was evident that there was a lack of compliance with guidelines on antibiotic use issued by the Ministry of Health.
  13. Rohani MY, Cheong YM, Rani JM
    Malays J Pathol, 1995 Dec;17(2):67-71.
    PMID: 8935128
    The diagnostic value of adenosine deaminase (ADA) activity was studied to evaluate its use in the differential diagnosis of tuberculous meningitis in the local setting. Cerebrospinal fluid (CSF) from 119 patients with meningitis and other conditions with central nervous system symptoms were collected and ADA activity determined by the colorimetric method of Guisti read at 628 nm. The CSF was also subjected to other laboratory examinations so as to provide the aetiological diagnosis. All 14 tuberculous meningitis patients had ADA activity greater than the cut off value of 9.0 IU/L. High ADA activity was also seen in 13 of 105 non-tuberculous cases giving a specificity of 87.6%. Even though the ADA activity determination is sensitive for tuberculosis, it was not specific enough to be used as a rapid diagnostic test. However when interpreted together with clinical signs and symptoms and other laboratory tests, it is a useful adjunctive rapid marker for tuberculosis.
  14. Lachumanan R, Devi S, Cheong YM, Rodda SJ, Pang T
    Infect Immun, 1993 Oct;61(10):4527-31.
    PMID: 7691753
    Binding studies of 160 overlapping, synthetic octapeptides from the hydrophilic regions of the Sta58 major outer membrane protein of Rickettsia tsutsugamushi with sera from patients with scrub typhus revealed 15 immunodominant peptides which are recognized by all the sera tested. Further analysis of the specificity of peptide binding with five of these peptides indicated that the peptides showed significantly stronger binding to scrub typhus patients' sera than they did to sera from patients with other febrile illnesses common in the region, i.e., malaria, dengue fever, typhoid fever, and leptospirosis. The main antibody class binding to these peptides appears to be immunoglobulin M, and there appears to be little correlation between reactivity with peptides and antibody titers measured by the indirect immunoperoxidase test.
  15. Mahalingam S, Cheong YM, Kan S, Yassin RM, Vadivelu J, Pang T
    J Clin Microbiol, 1994 Dec;32(12):2975-9.
    PMID: 7883885
    Isolates of Vibrio cholerae O1 El Tor from two well-defined cholera outbreaks in Malaysia were analyzed by using pulsed-field gel electrophoresis (PFGE). Isolates from sporadic cases occurring during the same time period were also studied. Digestion of chromosomal DNA from these isolates of V. cholerae O1 with restriction endonucleases NotI (5'-GCGGCCGC-3') and SfiI (5'-GGCCNNNN-3'), followed by PFGE, produced restriction endonuclease analysis (REA) patterns consisting of 13 to 24 bands (ranging in size from 46 to 398 kbp). Analysis of the REA patterns generated by PFGE after digestion with NotI and SfiI suggested the clonal nature and close genetic identity of the isolates obtained during each of the two outbreaks (Dice coefficient, 0.93 to 1.0). Although they had very similar REA patterns, the two outbreak clones were not identical. Isolates of V. cholerae O1 from sporadic cases, on the other hand, appeared to be much more heterogeneous (five different REA patterns detected in the five isolates tested; Dice coefficient, 0.31 to 0.81) than those obtained during the two outbreaks. We conclude that PFGE of V. cholerae O1 chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for molecular typing of V. cholerae isolates for epidemiological purposes.
  16. Thong KL, Cheong YM, Puthucheary S, Koh CL, Pang T
    J Clin Microbiol, 1994 May;32(5):1135-41.
    PMID: 7914202
    Pulsed-field gel electrophoresis (PFGE) was used to compare and analyze 158 isolates of Salmonella typhi from five well-defined outbreaks of typhoid fever in Malaysia and also isolates involved in sporadic cases of typhoid fever occurring during the same period. Digestion of chromosomal DNAs from these S. typhi isolates with the restriction endonucleases XbaI (5'-TCTAGA-3'), SpeI (5'-ACTAGT-3'), and AvrII (5'-CCTAGG-3') and then PFGE produced restriction endonuclease analysis (REA) patterns consisting of 11 to 24 DNA fragments ranging in size from 20 to 630 kbp. Analysis of the REA patterns generated by PFGE after digestion with XbaI and SpeI indicated that the S. typhi isolates obtained from sporadic cases of infection were much more heterogeneous (at least 13 different REA patterns were detected; Dice coefficient, between 0.73 and 1.0) than those obtained during outbreaks of typhoid fever. The clonal nature and the close genetic identities of isolates from outbreaks in Alor Setar, Penang, Kota Kinabalu, Johor Bahru, and Kota Bahru were suggested by the fact that only a limited number of REA patterns, which mostly differed by only a single band, were detected (one to four patterns; Dice coefficient, between 0.82 and 1.0), although a different pattern was associated with each of these outbreaks. Comparison of REA patterns with ribotyping for 18 S. typhi isolates involved in sporadic cases of infection showed a good correlation, in that 72% of the isolates were in the same group. There was no clear correlation of phage types with a specific REA pattern. We conclude that PFGE of s. typhi chromosomal DNA digested with infrequently cutting restriction endonucleases is a useful method for comparing and differentiating S. typhi isolates for epidemiological purposes.
  17. Cheong YM, Jegathesan M, Ansary A, Othman M
    Med J Malaysia, 1990 Mar;45(1):42-8.
    PMID: 2152068
    The prevalence of Enterotoxigenic Escherichia coli (ETEC) in 433 stool samples from diarrhoeal cases of all ages was studied using two commercially available test kits for the detection of heat labile toxin (LT) and the infant mouse assay for the heat stable toxin (ST). 16 samples (3.7%) were positive for ETEC, of which nine were producing ST alone, six LT alone and only one was producing both LT and ST. Although the percentage of isolation rate was low, its occurrence was almost as common as the Shigella spp and Salmonella spp in the same study. Of the two test kits examined, the Phadebact ETEC-LT Test 50 (Pharmacia Diagnostics, Uppsala, Sweden) was found to be more suitable for use in a routine diagnostic laboratory. Ten out of 12 (83%) of the strains tested were resistant to one or more antibiotics.
  18. Cheong YM, Jegathesan M, Singh M, Wong S, Ong L
    Malays J Pathol, 1985 Aug;7:51-2.
    PMID: 3939616
  19. Cheong YM, Wong WK, Ngeow YF
    Singapore Med J, 1993 Aug;34(4):352-3.
    PMID: 8266214
    A first case of Chlamydia pneumoniae pneumonia in Malaysia is reported. The diagnosis was made by a significant change in C. pneumoniae antibody titre. The infection responded well to a course of erythromycin.
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