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Biomedical subjects

J M Ling

Publications and source records attributed to J M Ling.

9 recordsLinked to original sources
PubMed1992

Development of trimethoprim-resistance in Salmonella typhi during therapy.

A typhoid patient was infected with a fully-sensitive, plasmidless strain of Salmonella typhi which acquired resistance to kanamycin, sulfamethoxazole and trimethoprim during cotrimoxazole therapy. The resistant post-treatment strain harboured 4 plasmids of 62, 4.1, 3.8 and 3.0 Md in size. Kanamycin-, sulfamethoxazole- and trimethoprim-resistance were borne on a transferable 62 Md plasmid which was compatible with groups FI, FIme, FII, FIV, H1, H2, B, I1, I2, J, K, M, N, T, X, W and P. Sulfamethoxazole-resistance was also borne on the 4.1 Md plasmid. The 3.8 Md plasmid was not transferable; the 3.0 Md plasmid was transferable but did not confer antibiotic resistance. Excluding the strain described here, only 5 out of 35 other S typhi isolates contained plasmids. This is the first report of trimethoprim-resistant S typhi in Hong Kong.

Adult↗
PubMed1991

Antimicrobial susceptibilities and beta-lactamase production of Hong Kong isolates of gastroenteric salmonellae and Salmonella typhi.

We examined the in-vitro antibiotic susceptibility of 760 gastroenteric salmonellae and 36 strains of Salmonella typhi isolated in Hong Kong between 1985 and 1988. S. typhi remained susceptible to all the antibiotics tested except for one isolate resistant to chloramphenicol, another to kanamycin and co-trimoxazole, and a third to nalidixic acid. In contrast, resistance and multiple resistance has increased significantly in gastroenteric salmonellae over the last ten years. Seventeen percent were resistant to ampicillin, 61% to tetracycline, 23% to chloramphenicol and 8% to gentamicin. Many ampicillin-resistant strains remained resistant to ampicillin even in the presence of sulbactam (69%) or clavulanic acid (25%). More than 50% of isolates were resistant to two or more antibiotics and one isolate was resistant to eleven. Ampicillin-resistance was usually due to the production of TEM-1 or OXA-1 beta-lactamases but a few isolates produced AER-1, PSE-1 or PSE-2. Genetic determinants for these enzymes were usually borne on plasmids ranging in size from 2 to 143.7 Md but half of the OXA-1 genes were chromosomally located.

Ampicillin Resistance↗
PubMed1990

Hong Kong strains of methicillin-resistant and methicillin-sensitive Staphylococcus aureus have similar virulence.

While most authorities agree that methicillin-resistant Staphylococcus aureus (MRSA) are as pathogenic as methicillin-sensitive strains (MSSA), some believe that MRSA are relatively avirulent opportunists, and that their importance has been exaggerated. We present evidence that Hong Kong strains of MRSA and MSSA are equally pathogenic: they have similar virulence in animal models; they are isolated in similar proportions from both deep and superficial clinical sites including blood; in patients with hospital-acquired bacteraemias mortality rates are similar when adjusted for clinical factors; and in both animals and patients with systemic MRSA infection, mortality rates are significantly reduced by vancomycin therapy. Efforts to control the spread of MRSA are justified, and in invasive sepsis early treatment with vancomycin may be life-saving.

Animals↗
PubMed1990

Evaluation of Cathra system for identifying gram negative aerobic bacteria.

The Cathra system is a commercial multipoint inoculation method for the identification of aerobic Gram negative bacteria. The system uses a replicator technique in which 21 different agar media can be inoculated simultaneously with 36 organisms. Identifications are made by use of a special computer database. The performance of this system was compared with that of the API 20E for the identification of 372 clinical isolates of Enterobacteriaceae and 133 miscellaneous Gram negative bacteria. For enterobacteria, the Cathra system was in 97% agreement with API 20E at species level and 98% at genus level. For miscellaneous Gram negative strains the two systems were in 59% agreement at species level and 77% at genus level. The Cathra system is suitable for use in diagnostic laboratories, especially those with a heavy workload and a wish to use break-point sensitivity testing. The identification database for miscellaneous Gram negative organisms, however, needs to be expanded.

Bacteriological Techniques↗
PubMed1989

Antimicrobial susceptibilities of Haemophilus species in Hong Kong.

Altogether 403 Haemophilus spp. were isolated in seven hospital laboratories in Hong Kong during June 1986, mostly from sputum. Of these 73% were Haemophilus influenzae and 27% Haemophilus parainfluenzae. All the isolates of H. influenzae were non-capsulated; Haemophilus spp. were not isolated from blood or cerebrospinal fluid (CSF) during the period of the study. Antimicrobial resistance, including multiple resistance, was common. Of all the strains of H. influenzae, 20% were resistant to 1 mg/l ampicillin, (all except one by production of TEM-1 beta-lactamase), 65% were resistant to 0.5 mg/l erythromycin, 25% to 1 mg/l tetracycline, 14% to 1 mg/l chloramphenicol (mediated by the production of a chloramphenicol-destroying enzyme) and less than 1% to 8 mg/l cefaclor and 0.5 mg/l trimethoprim. All isolates were susceptible to cephamandole and cefuroxime. Haemophilus parainfluenzae showed similar susceptibilities, except that a greater proportion of strains was sensitive to erythromycin and chloramphenicol. Only 50% of the ampicillin-resistant strains of H. influenzae and H. parainfluenzae contained detectable plasmids of 2-55 Mdal arranged in six to nine different plasmid profiles. Resistance to ampicillin and chloramphenicol has increased markedly in isolates of H. influenzae in Hong Kong over the last 5 years. This resistance may be associated with transposable genes.

Ampicillin↗
PubMed1989

Microcomputer program in Chinese to manage and analyze antimicrobial susceptibility results.

A chinese microcomputer program which analyzes the minimal inhibitory concentration (MIC) of antimicrobial susceptibility and presents the results in tabular and chart forms is described. This program also computes MIC50, MIC90, and geometric mean MIC and displays these values for a large number of antimicrobials in a summary table. The set of MIC values used for different groups of organisms or antimicrobial agents can be altered without changing the program. A text file of the results is written into the disk to enable editing before final presentation. The program features several major enhancements over previously published ones.

Anti-Bacterial Agents↗
PubMed1988

Evaluation of the Microbact-24E bacterial identification system.

The Microbact 24E (MB24E) system is a commercial microsystem for the identification of common clinical isolates of Enterobacteriaceae and non-fermenting Gram negative bacilli, and consists of dehydrated substrates distributed in the wells of microtitre trays. This system was compared with the API20E for the identification of 386 bacterial isolates, which included 284 clinical and 102 environmental organisms. There was 97% and 91% agreement for the identification of clinical isolates of Enterobacteriaceae and other Gram negative bacilli, respectively. The identification of environmental isolates by both systems was less satisfactory. The API20E has a more extensive database than the MB24E and is thus more reliable for the identification of rare or unusual organisms, but the MB24E is cheaper, is easy and convenient to use, and is suitable for a routine microbiology laboratory.

Bacteriological Techniques↗
PubMed1987

Observer variability in microcomputer-assisted morphometric study of nuclear parameters.

To evaluate observer variability during microcomputer-assisted planimetry, nuclear features (area, perimeter, and form factor) were studied in a case of malignant lymphoma. Tissue fixed in glutaraldehyde, embedded in plastic and sectioned at 1 micron was studied using a Zeiss Kontron IBAS 2000 image analysis system. Manual tracing of nuclear outline was performed to obtain the parameters. Both interindividual and intraindividual reproducibilities were evaluated, the former among 8 observers and the latter by the observers repeating the measurements. With the present technique, intraindividual reproducibility was high and correlation was excellent for area, perimeter and form factor measurements. A high degree of interindividual inconsistency was demonstrated for all parameters. Interindividual correlation was poor for form factor. It is concluded that poor interindividual reproducibility even when the objective method of morphometry is used may be a significant problem in tissue investigations, especially when results from different laboratories are being compared.

Cell Nucleus↗