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Biomedical subjects

P D Meers

Publications and source records attributed to P D Meers.

At least 19 recordsLinked to original sources

Partial characterization of an endemic strain of a methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA) homogeneously resistant to beta-lactam antibiotics.

Selected strains of methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA) were subjected to a preliminary examination. They were representative of a larger group collected in a routine clinical microbiology laboratory over a period of 2 years. MARSA was endemic in the associated hospital. The characteristics investigated were antimicrobial resistance, the production of beta-lactamase, free and bound coagulase, protein A, DNA-ase, urease, lipase and pigment. The MARSA strains were generally indistinguishable, other than in their antimicrobial resistances. The resistance to methicillin was completely homogeneous. Except with imipenem, growth extended to the edge of discs containing methicillin and the other beta-lactam antibiotics tested when the strains were cultured at 37 degrees C on media without added salt. Homogeneous resistance may confer an epidemiological advantage on strains of this phenotype.

Aminoglycosides

Community-acquired legionellosis in Singapore.

Patients admitted to hospital with chest infections were examined serologically to see if these were due to Legionella pneumophila. Each of the 219 samples of serum collected from 177 patients was examined by two standard tests. The tests, which generally agreed, identified three individuals (1.7% of the group) who had sufficient antibody to suggest that they were suffering from current legionellosis. Serological evidence of previous infection was discovered (with differing degrees of certainty) in 26 (14.7%) of the others. The study showed that legionellosis is endemic in Singapore, and so must be taken into account in the differential diagnosis of cases of pneumonia.

Adult

The impact of methicillin- and aminoglycoside-resistant Staphylococcus aureus on the pattern of hospital-acquired infection in an acute hospital.

Infections due to methicillin- and aminoglycoside-resistant Staphylococcus aureus (MARSA) appeared in a new teaching hospital shortly after it opened. The effect this had on the pattern of hospital-acquired infections in the four years that followed is described. No control measures were applied and MARSA became endemic. New infections appeared at a rate of about four for each 1000 patients discharged. It established itself at different levels of incidence in various specialist units, patients under intensive care being most severely affected. MARSA was implicated in half of all hospital-acquired infections due to S. aureus but it was not more pathogenic than its more sensitive counterpart. It had little impact on the life of the hospital.

Aminoglycosides

Bacteriostatic and bactericidal actions of boric acid against bacteria and fungi commonly found in urine.

Boric acid has been used for over 20 years to preserve urine while in transit for bacteriological examination. It has been suggested that it may be toxic for some urinary pathogens. To investigate this several strains of bacteria and fungi commonly found in urine were exposed to different concentrations of boric acid in nutrient broth. Viable counts were made at the outset and at intervals for up to 24 hours at room temperature to detect bacteriostatic or bactericidal effects. At concentrations between 10 and 20 g/l boric acid was bacteriostatic or fungistatic for very nearly all the common urinary pathogens. At 10 g/l boric acid was weakly bactericidal for some strains of Acinetobacter calcoaceticus and Pseudomonas aeruginosa, though higher concentrations were bacteriostatic only. Group B streptococci varied in their response to boric acid, but for most of them 10 or 20 g/l was satisfactorily bacteriostatic. It is concluded that boric acid is rarely toxic, and when it is, the effect is usually sufficiently delayed to be of only theoretical importance.

Acinetobacter

Boric acid converts urine into an effective bacteriostatic transport medium.

Results of an experiment designed to assess the usefulness of boric acid for preserving urine before its bacteriological examination are reported. Boric acid at a concentration of 20 g/l was found to be usefully bacteriostatic, largely eliminating the false positive results obtained with unpreserved specimens when delay before culture was more than 90 min. The effect lasted for up to 48 h. There was no evidence that borate is toxic to the urinary pathogens encountered in naturally infected urine. Borate also preserves white blood cells in urine and thereby marginally improved the diagnosis of pyuria. The results confirm that boric acid may with benefit be added to bottles used for transporting specimens of urine to the laboratory.

Bacteria

The specificity of a rapid method of assay for the presence of Legionella species in water.

A rapid method of assay, using a monoclonal antibody linked to alkaline phosphatase, was used for the detection of the Pontiac subgroup of Legionella pneumophila serogroup 1. It was tested for its specificity against 53 strains of Legionella recently isolated from the environment in Singapore and Malaysia. The specificity and sensitivity of this method of assay was confirmed, though there is some concern that the specificity was too narrow, and there are reservations about the criteria suggested for interpreting the results.

Bacteriological Techniques

Legionella species, serogroups and subgroups found in the environment in Singapore.

Over a period of seven months, 87 samples of water collected from 48 air-conditioning cooling-towers on 15 sites in Singapore yielded 19 strains of Legionella. Legionellas were found in 7 of the 15 sites. The strains isolated fell into 7 species, serogroups or subgroups of the genus Legionella. Only 11% of them belonged to the more pathogenic Pontiac subgroup of Legionella pneumophila serogroup 1.

Disease Outbreaks

Infection control in developing countries.

The level of socio-political and economic development achieved by a country determines the quality and quantity of the health care its citizens receive. These factors also govern the amount of attention given to hospital-acquired infection. The problems of infection control in 'developing' countries include, first, the international problems that arise from clashes of personality and viewpoint among those responsible for it, exacerbated in some places by ethnic or religious traditions. Second are problems imposed by factors that affect the spectrum of infectious disease, and third is a variable deficiency of human and financial resources. In the search for solutions, an analysis suggests that nurses are particularly suited to take the lead in the prevention of infection, so that a special initiative directed towards their education in the rapidly developing science of hospital infection and its control is likely to be the most cost effective and appropriate initial approach. This needs to be accompanied by parallel improvements in the education of medical undergraduates. Anything else should be applied in response to measured need, and then only as money and manpower permit. Careful thought is required to avoid squandering scarce resources by applying inappropriate infection control technology.

Communicable Disease Control

Facts and fancies in hospital infection.

The history of infection in hospitals reveals that a surprising number of the practices that have been introduced at various times as control measures were based on original misconceptions. Curiously in this modern era, a significant number of these infections control practices, lacking a scientific basis, are still widely employed, and some of them have developed into increasingly expensive rituals. The escalating cost of medical care suggests that the time has come to examine these rituals to assess their cost-effectiveness and so decide on their future.

Cost-Benefit Analysis

Yellow fever in Swansea, 1865.

A cargo of copper ore from Cuba was discharged at Swansea in mid-September 1865, during a spell of exceptionally hot weather. A small number of mosquitoes infected with the yellow fever virus, disembarking at the same time, established an epidemic of yellow fever in the town. In the next 25 days, at least 27 inhabitants were infected and 15 of them died. The quality of contemporary observation and recording has encouraged a re-examination of the events in the light of knowledge unavailable at the time. It cannot be assumed that the episode will not be repeated.

Animals

Shedding of bacteria and skin squames after handwashing.

Particles released into the air by wringing the hands together were collected in a slit sampler before and after washing with bar soap, with three surgical scrubs, and after rubbing them with a spirit-based lotion. The particles were identified, their number estimated, those that bore bacteria counted, and the bacteria themselves classified. It was found that there was a significant increase, averaging 17-fold, in the number of particles carrying viable bacteria released after washing with soap. The increase in bacterial dissemination was suppressed if a surgical scrub was used in place of soap, or when the lotion was used without washing. The number of skin squames released increased by 18-fold or more after washing with soap or a surgical scrub, but not after using the lotion. This suggests that a surgical scrub should be used more widely in clinical practice, and that a spirit-based hand lotion might with advantage become a partial substitute for handwashing, particularly in areas where handwashing is frequent and iatrogenic coagulase-negative staphylococcal infection common.

Chlorhexidine