Distinct patterns of tissue-specific lipid accumulation during the induction of insulin resistance in mice by high-fat feeding.

AIMS/HYPOTHESIS: While it is well known that diet-induced obesity causes insulin resistance, the precise mechanisms underpinning the initiation of insulin resistance are unclear. To determine factors that may cause insulin resistance, we have performed a detailed time-course study in mice fed a high-fat diet (HFD). METHODS: C57Bl/6 mice were fed chow or an HFD from 3 days to 16 weeks and glucose tolerance and tissue-specific insulin action were determined. Tissue lipid profiles were analysed by mass spectrometry and inflammatory markers were measured in adipose tissue, liver and skeletal muscle. RESULTS: Glucose intolerance developed within 3 days of the HFD and did not deteriorate further in the period to 12 weeks. Whole-body insulin resistance, measured by hyperinsulinaemic-euglycaemic clamp, was detected after 1 week of HFD and was due to hepatic insulin resistance. Adipose tissue was insulin resistant after 1 week, while skeletal muscle displayed insulin resistance at 3 weeks, coinciding with a defect in glucose disposal. Interestingly, no further deterioration in insulin sensitivity was observed in any tissue after this initial defect. Diacylglycerol content was increased in liver and muscle when insulin resistance first developed, while the onset of insulin resistance in adipose tissue was associated with increases in ceramide and sphingomyelin. Adipose tissue inflammation was only detected at 16 weeks of HFD and did not correlate with the induction of insulin resistance. CONCLUSIONS/INTERPRETATION: HFD-induced whole-body insulin resistance is initiated by impaired hepatic insulin action and exacerbated by skeletal muscle insulin resistance and is associated with the accumulation of specific bioactive lipid species.

Interleukin-6-deficient mice develop hepatic inflammation and systemic insulin resistance.

AIMS/HYPOTHESIS: The role of IL-6 in the development of obesity and hepatic insulin resistance is unclear and still the subject of controversy. We aimed to determine whether global deletion of Il6 in mice (Il6 (-/-)) results in standard chow-induced and high-fat diet (HFD)-induced obesity, hepatosteatosis, inflammation and insulin resistance. METHODS: Male, 8-week-old Il6 (-/-) and littermate control mice were fed a standard chow or HFD for 12 weeks and phenotyped accordingly. RESULTS: Il6 (-/-) mice displayed obesity, hepatosteatosis, liver inflammation and insulin resistance when compared with control mice on a standard chow diet. When fed a HFD, the Il6 (-/-) and control mice had marked, equivalent gains in body weight, fat mass and ectopic lipid deposition in the liver relative to chow-fed animals. Despite this normalisation, the greater liver inflammation, damage and insulin resistance observed in chow-fed Il6 (-/-) mice relative to control persisted when both were fed the HFD. Microarray analysis from livers of mice fed a HFD revealed that genes associated with oxidative phosphorylation, the electron transport chain and tricarboxylic acid cycle were uniformly decreased in Il6 (-/-) relative to control mice. This coincided with reduced maximal activity of the mitochondrial enzyme ß-hydroxyacyl-CoA-dehydrogenase and decreased levels of mitochondrial respiratory chain proteins. CONCLUSIONS/INTERPRETATION: Our data suggest that IL-6 deficiency exacerbates HFD-induced hepatic insulin resistance and inflammation, a process that appears to be related to defects in mitochondrial metabolism.

A test for 'hygienic' hand disinfection.

A standardised test procedure is described in which finger-tips are inoculated with broth cultures of organisms (Staphylococcus aureus, Staphyloccocus saprophyticus, Escherichia coli, and Pseudomonas aeruginosa): counts are made from washings of hands after disinfection with various antiseptic-detergents, alcoholic solutions, or unmedicated soap. 70% alcohol, with or without chlorhexidine, was the most effective preparation. The two antiseptic detergents showed variable results, but against Gram-negative bacilli neither was significantly more effective than plain soap. Some tests were also made on the death rate of organisms dried on the skin without disinfection.

Bacteriological sampling of postmortem rooms.

Thirty hospital and coroners' postmortem rooms in the West Midlands were visited over two years. The design, environmental facilities, and hygienic practices were investigated and air exchange rates were measured. Microbiological samples were taken from the environment and from gloves, hands, and protective clothing of staff. Glove punctures were also recorded and a plastic isolator evaluated. Bacterial counts in the air were low and related more to the number of people in the room than to the air exchange rate. There was little evidence of the production of aerosol containing bacteria, although splashing occurred while intestines were being washed out. Surfaces often remained contaminated with Gram negative bacilli after cleaning but numbers were considerably reduced on drying. Decontamination of instruments was satisfactory. A wide range of disinfectants and concentrations was used, but none showed evidence of contamination. Gloves were heavily contaminated after use, and occasionally the hands of the wearer after removal of the gloves. Washing the hands effectively removed residual transient organisms, irrespective of the agent used. The incidence of glove punctures was higher among technicians (38%) than pathologists (12%). The plastic isolator reduced smells and limited environmental contamination but visibility and acceptability were poor. The results of the study suggest that there is little evidence of risk of infection to staff, providing basic hygienic precautions are taken, but consideration should be given to the prevention of glove punctures.

Methods of reprocessing complex medical equipment.

The choice as to which of the two gaseous processes is best suited to individual hospital needs is a difficult one. Very few items are unable to tolerate 73 degrees C (LTSF) and these few can withstand 37 degrees C or 55 degrees C (EO). Unfortunately, LTSF is a 'moist' process and sterilizers have a poor history of providing sterilization without modification, and consequently few are used. Ethylene oxide is more reliable, but environmental hazards are greater and running costs high. Both processes are time-consuming and the use of sporicidal disinfectants such as glutaraldehyde is often the only practical alternative. Before purchasing any gaseous sterilizer it is essential to consider throughput and the availability of alternative processes. It may prove sensible to share facilities or at least offer a regional facility. It is certainly not worthwhile purchasing expensive gas sterilizers for reprocessing inexpensive single-use items or for those that require disinfection only. Low temperature steam is safe, inexpensive and no special environmental provisions are necessary. It is, however, not a sterilization process. Disinfectants, hot water and steam will continue to be the only suitable methods for reprocessing items outside the hospital sterile supply department or disinfection unit. Concern over the decontamination of blood-stained instruments following use on patients with hepatitis B or HIV has led to an upsurge of interest in boilers and inexpensive bench top ovens and autoclaves. Such processes are likely to prove more effective than disinfectants but should heat treatment prove impractical then 2% glutaraldehyde or 70% alcohol may be used.(ABSTRACT TRUNCATED AT 250 WORDS)

Endoscope decontamination: automated vs. manual.

Automated endoscope washer disinfectors are widely used for the decontamination of flexible endoscopes. They are more effective than manual techniques and reduce the likelihood of skin contact with irritant disinfectants. Suitable machines are those which effectively clean, disinfect and rinse all channels and external surfaces without damaging the instrument. If glutaraldehyde is used, fumes should be removed or contained to protect endoscopy and processing staff. Machines should also be equipped with a self-disinfect facility and the rinse water should be of a suitable microbiological quality for the instruments processed, i.e. bacteria-free (sterile or filtered) water should be used for bronchoscopes and all invasive endoscopes. The choice of machine and cycle will depend on the following: whether a mobile or fixed unit is required; the type of disinfectant used; instrument throughput; and whether or not it is necessary to process more than one endoscope at a time. Purchasers are advised to request independent test reports which substantiate manufacturers' claims.

Endoscope decontamination: where do we go from here?

Thorough cleaning and disinfection or sterilization of endoscopes and associated equipment will reduce the likelihood of misdiagnosis and post-procedural infection. It will also prevent instrument deterioration and malfunction. With a rapid escalation in demand for endoscopy, particularly that associated with minimally invasive surgery, it is important that we have the processing technology to match the diagnostic and therapeutic value of these instruments without exposing staff and patients to unnecessary risk. Wherever possible staff should purchase heat tolerant endoscopic equipment that is readily accessible for cleaning. Automated processors, e.g. washer disinfectors and ultrasonic cleaners, improve the quality of the decontamination process but machines must have a self-disinfect function to prevent instrument recontamination during processing. Sterile, or filtered bacteria-free, water is essential for bronchoscopes and invasive instruments. Glutaraldehyde is still the most widely used disinfectant, particularly for the heat sensitive flexible endoscopes, but it is irritant and sensitizing and a safer alternative is sought. Peracetic acid is more rapidly efficacious and probably less irritant and, provided it does not damage endoscopes and processing equipment, may prove a suitable alternative. Unfortunately there are no nationally agreed test methods for assessing this and other new endoscope disinfectants and therefore no register of suitable or approved products. There is also no proven safe alternative to ethylene oxide for sterilizing invasive heat labile flexible endoscopes. It is important that, if toxic disinfectants and sterilants are used, staff and patients are suitably protected from exposure. Update training is essential for all processing staff if infection risks are to be minimized and sensitization problems avoided.

The mechanics of endoscope disinfection.

The decontamination of flexible fibreoptic endoscopes has considerably improved in recent years. This is mainly due to the introduction of instruments with more accessible channels, the use of automated washer disinfectors and a greater awareness of the problems associated with disinfection. Unfortunately the most widely used and effective disinfectant is 2% glutaraldehyde and this is toxic, irritant and sensitizing. With the implementation of Control of Substances Hazardous to Health legislation, strict environmental controls are required to reduce skin contact and vapour inhalation. Alcohol is probably the most suitable alternative disinfectant at present but it is flammable and cannot be used in automated systems. Other agents are either insufficiently effective or corrosive. Autoclavable or heat tolerant rigid endoscopes are now available but flexible endoscopes will not tolerate heat disinfection temperatures.

Risk of airborne transmission in an operating theatre containing four ultraclean air units.

This study shows that a single, large, operating theatre (barn) containing four ultraclean operating units (cabins), was highly effective in reducing the number of airborne bacteria in the operating fields providing all occupied ultraclean cabins were functioning correctly. The air flows and bacterial counts during operations within the cabins met the current standard for ultraclean systems (HTM 2025 1994) and there was no evidence of mixing of air between cabins. It is, however, recommended that air flows are regularly checked for compliance with the standard. If failure occurs in any single ultraclean unit, surgery in that cabin should cease as contaminated air may enter from the barn and surrounding cabins. Routine microbiological sampling should not be necessary providing there is no evidence of filter leakage. An operating theatre with several ultraclean operating tables in a single room would appear to be a viable proposition for the future. Considerable savings are likely in revenue costs as much of the air is reused and support services are shared.

An outbreak of candidiasis in a special care baby unit: the use of a resistogram typing method.

An outbreak of candida infections involving 12 neonates in a special care baby unit is reported. An investigation of colonization of all the babies in the unit was made together with the sampling of the environment and hands of staff. Resistogram typing of isolates indicated the presence of several strains with probable cross-infection. Transmission was possibly by the hands of staff, but multiple antibiotic therapy may have played a role in the increased incidence of infection in the unit.

Evaluation of the antimicrobial activity of a new super-oxidized water, Sterilox, for the disinfection of endoscopes.

The antimicrobial activity of a new super-oxidized water, Sterilox, has been tested against Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, Mycobacterium chelonae, Escherichia coli (including type O157), Enterococcus faecalis, Pseudomonas aeruginosa, Bacillus subtilis var niger spores, methicillin-resistant Staphylococcus aureus, Candida albicans, poliovirus type 2 and human immunodeficiency virus HIV-1. Under clean conditions, freshly generated Sterilox was found to be highly active against all these micro-organisms giving a 5 log10 (99.999%) or greater reduction in two minutes or less.

Contamination of protective clothing and nurses' uniforms in an isolation ward.

Staphylococcus aureus was frequently isolated, usually in small numbers, from cotton gowns (12.6 per cent), plastic aprons (9.2 per cent) and nurses' uniforms (15 per cent). Gram-negative bacilli were infrequently isolated. Contamination of the protective clothing did not increase when used over periods of up to 11 days. Fewer organisms were recovered from the front of nurses' uniforms when plastic aprons instead of gowns were worn, but gowns provided better shoulder protection. However, no differences were observed in isolations of Staph, aureus or Gram-negative bacilli from these sites.

Evaluation of the Steris System 1 Peracetic Acid Endoscope Processor.

An automated endoscope sterilizing machine, the Steris System 1 Processor, was tested for bactericidal and sporicidal efficacy. The disinfectant, peracetic acid, was diluted to 0.2% within an enclosed system. The exposure time to the disinfectant was 12 min and the overall cycle time ranged from 25-38 min, mean 29 min. Preliminary suspension tests, with and without yeast or serum, showed a log10 reduction of > 5 with Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus subtilis in 5 min with 0.2% peracetic acid. After a routine cycle in the machine, endoscopes contaminated with the same organisms showed no growth. Two of 24 spore strips, containing 10(6) B. subtilis showed a small number of survivors (less than 10 per strip). No significant damage to the endoscope was observed although the number of cycles tested was small (i.e. 31). The advantage of the system is that staff are not directly exposed to the agent, but the costs per cycle are higher than glutaraldehyde, since peracetic acid is not renewed. Unlike other automated processors the Steris machine has no cleaning cycle.

Infection risk and potential contamination of urine specimens associated with sample port design of catheter leg bags.

The ease of disinfection of the sample ports of three types of urine drainage leg bags with different sampling port systems was assessed using a bladder bag model. The ports were contaminated with Escherichia coli, 'disinfected' using a standard method, then sampled at time intervals up to one week after contamination. It was discovered that leg bags which employ a needle-based sampling system (the 'sample safe port system') were easier to disinfect than those which did not, and that organisms are retained in large enough numbers to lead to misdiagnosis of a urinary tract infection or to pose a retrograde infection risk.

Mycobactericidal activity of selected disinfectants using a quantitative suspension test.

In this study, a quantitative suspension test carried out under both clean and dirty conditions was used to assess the activity of various instrument and environmental disinfectants against the type strain NCTC 946 and an endoscope washer disinfector isolate of Mycobacterium chelonae, Mycobacterium fortuitum NCTC 10,394, Mycobacterium tuberculosis H37 Rv NCTC 7416 and a clinical isolate of Mycobacterium avium-intracellulare (MAI). The disinfectants tested were; a chlorine releasing agent, sodium dichloroisocyanurate (NaDCC) at 1000 ppm and 10,000 ppm av Cl; chlorine dioxide at 1100 ppm av ClO2 (Tristel, MediChem International Limited); 70% industrial methylated spirits (IMS); 2% alkaline glutaraldehyde (Asep, Galan); 10% succinedialdehyde and formaldehyde mixture (Gigasept, Schulke & Mayr); 0.35% peracetic acid (NuCidex, Johnson & Johnson); and a peroxygen compound at 1% and 3% (Virkon, Antec International). Results showed that the clinical isolate of MAI was much more resistant than M. tuberculosis to all the disinfectants, while the type strains of M. chelonae and M. fortuitum were far more sensitive. The washer disinfector isolate of M. chelonae was extremely resistant to 2% alkaline activated glutaraldehyde and appeared to be slightly more resistant than the type strain to Nu-Cidex, Gigasept, Virkon and the lower concentration of NaDCC. This study has shown peracetic acid (Nu-Cidex), chlorine dioxide (Tristel), alcohol (IMS) and high concentrations of a chlorine releasing agent (NaDCC) are rapidly mycobactericidal. Glutaraldehyde, although effective, is a slow mycobactericide. Gigasept and Virkon are poor mycobactericidal agents and are not therefore recommended for instruments or spillage if mycobacteria are likely to be present.

Mycobacterium terrae: a potential surrogate for Mycobacterium tuberculosis in a standard disinfectant test.

The susceptibility of Mycobacterium tuberculosis and Mycobacterium avium-intracellulare to the disinfections used for spillage and heat sensitive instruments has received much attention in recent years. The use of clinical isolates of M. tuberculosis and M. avium-intracellulare as test organisms is considered unsuitable for standard tests due to their hazardous nature (category 3 pathogens and slow growth rates). This has led to much debate in standards committees on the selection and use of a possible surrogate which would be safer and more practical to use and yet mimic the susceptibility of clinical isolates. This study compared the susceptibility of one possible surrogate Mycobacterium terrae NCTC 10856, with that of clinical isolates of M. tuberculosis H37 Rv and M. avium-intracellulare using a quantitative suspension test. The instrument and environmental disinfectants tested were a chlorine-releasing agent, sodium dichloroisocyanyurate (NaDCC) at 1000 ppm and 10,000 ppm av. Cl, chlorine dioxide at 1100 ppm av. ClO2 (Tristel, HayMan MediChem), 0.35% peracetic acid (NuCidex, Johnson & Johnson), 70% industrial methylated spirit (IMS), 2% alkaline glutaraldehyde (Asep, Galen), 10% succine dialdehyde and formaldehyde mixture (Gigasept, Schulke and Mayr). Results showed that the clinical isolate of M. avium-intracellulare was the most resistant of the three test organisms. M. terrae, which is not a category 3 pathogen, was slightly more resistant than M. tuberculosis and this would appear to be a suitable surrogate for establishing tuberculocidal activity. However, with an increase in the clinical significance of M. avium-intracellulare, particularly in human immunodeficiency virus (HIV) and immunocompromised patients, a more resistant surrogate is required. In the absence of such a surrogate, testing with M. avium-intracellulare in a clinical laboratory equipped for handling category 3 pathogens is still advised to establish mycobactericidal activity.

A test procedure for evaluating surgical hand disinfection.

A technique for assessing the immediate and prolonged efficacy of surgical scrubs and alcoholic hand rubs is described. A mean baseline count is obtained from all volunteers and logarithmic reductions in resident skin flora immediately after one or more applications, and after wearing gloves for 3 h, are measured. Loose-fitting surgical gloves are used for sampling resident flora. Preparations were applied using a standard technique for 2 min, apart from one test with 70% isopropanol (IPA) in which the application time was 30 s. Two studies are described, one of which compared four chlorhexidine scrubs, and the second 70% IPA, 7.5% povidone-iodine scrub, 2% triclosan cleanser and unmedicated bar soap. In spite of their constituent similarity, the four chlorhexidine scrubs varied considerably in efficacy and user acceptability. A 2 min application of 70% IPA was the most effective treatment, and gave log10 reductions of 1.65 for immediate and 1.58 for prolonged effect. This was marginally more effective than a 30 s application, but the difference was not significant. 'Hibiscrub' was the most effective aqueous formulation and gave reductions of 1.01 for immediate effect and 1.16 for prolonged effect. The test described could be used by reference centres and manufacturers to assess the efficacy of new and existing surgical hand disinfection formulations.

Comparison of automated systems for the cleaning and disinfection of flexible fibreoptic endoscopes.

A comparison of four cleaning and disinfection machines is described. These varied considerably in design and function and although no single machine possessed all the preferred characteristics, cleaning and disinfection, particularly between patients, was substantially improved. Before purchasing a machine it is recommended that the user ensures that it is convenient to operate, effective in removing soil and bacteria, and adaptable to the range of fibrescopes used within the unit. Infections are often caused by Gram-negative bacilli which are particularly difficult to remove manually from moist narrow channels of the fibrescope and perfusion of all channels including the air channel, is, therefore, recommended. Thorough cleaning and disinfection will not only reduce the likelihood of infection but will also reduce channel blockages and the general deterioration of the fibrescope.

A test for the assessment of 'hygienic' hand disinfection using rotavirus.

A standardized test procedure is described in which finger tips are inoculated with bovine rotavirus. The level of virus recovered after disinfection of artificially contaminated hands with various disinfectant detergents, alcoholic solutions and alcoholic formulations was determined. The method was found to be easy to perform and reproducible. The most efficient method for removal of virus from fingertips was found to be treatment with alcoholic solutions or products. Soap and water and disinfectant detergents were found to be a much less effective method of removing virus from contaminated hands.

A comparison of pre-operative bathing with chlorhexidine-detergent and non-medicated soap in the prevention of wound infection.

In a 60-week cross-over study on 5536 patients in 20 wards of three city hospitals (two general and one orthopaedic), pre-operative bathing with chlorhexidine-detergent failed to influence the incidence of postoperative infection, in spite of the relatively high incidence of infection with skin organisms. Of the patients bathing pre-operatively with chlorhexidine-detergent, 5.4 per cent subsequently became infected (4.0 per cent of clean wounds) and of those bathing with unmedicated soap 4.9 per cent (3.5 per cent of clean wounds). A single pre-operative bath with chlorhexidine-detergent would, therefore, appear to be of dubious value in preventing postoperative wound infection.