Ultraclean ventilation in operating theatres--beyond laminar flow.
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Humans↗
Biomedical subjects
A P Fraise
Publications and source records attributed to A P Fraise.
'Lesson learnt--do not panic'.
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Attitude of Health Personnel↗
Biocide abuse and antimicrobial resistance--a cause for concern?
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Anti-Infective Agents↗
Susceptibility of antibiotic-resistant cocci to biocides.
Biocide resistance has hitherto been a poorly studied subject, possibly due to the belief that such resistance was rare and clinically insignificant. Various recent findings, however, have underlined the importance of biocide resistance as a clinically relevant phenomenon. Outbreaks of biocide-resistant organisms in hospitals have been described and the genetic mechanism for resistance to quaternary ammonium compounds (QACs) in Staphylococcus aureus has now been elucidated. Mycobacteria resistant to commonly used endoscope disinfectants are now commonly reported and have caused numerous adverse clinical events. Cross-resistance between triclosan and antituberculous drugs has been demonstrated in other strains of mycobacteria. This is related to a common mechanism of action. The work presented here describes studies into the biocide resistance of antibiotic-resistant cocci and attempts to create biocide-resistant strains in vitro. Strains of staphylococci (including methicillin-resistant Staph. aureus (MRSA)) and enterococci (including vancomycin-resistant enterococci (VRE)) had their susceptibility to biocides assayed using broth macro dilution methods and resistant strains were selected by serial subculture on biocide-containing media. Mutants were created with relative ease; for instance, triclosan minimal bactericidal concentrations (MBCs) increased from 0.002 to 3.12 mg l(-1). Some strains of MRSA which have intermediate resistance to glycopeptides were demonstrated to have decreased susceptibility to some biocides. Biocide resistance amongst enterococci was demonstrated although there was no clear correlation between biocide and antibiotic resistance. The exact mechanisms of resistance in these strains are still being studied but it is clear that biocide resistance is an important clinical phenomenon.
Anti-Infective Agents, Local↗
Susceptibility of antibiotic-resistant cocci to biocides.
Biocide resistance has hitherto been a poorly studied subject, possibly due to the belief that such resistance was rare and clinically insignificant. Various recent findings, however, have underlined the importance of biocide resistance as a clinically relevant phenomenon. Outbreaks of biocide-resistant organisms in hospitals have been described and the genetic mechanism for resistance to quaternary ammonium compounds (QACs) in Staphylococcus aureus has now been elucidated. Mycobacteria resistant to commonly used endoscope disinfectants are now commonly reported and have caused numerous adverse clinical events. Cross-resistance between triclosan and antituberculous drugs has been demonstrated in other strains of mycobacteria. This is related to a common mechanism of action. The work presented here describes studies into the biocide resistance of antibiotic-resistant cocci and attempts to create biocide-resistant strains in vitro. Strains of staphylococci (including methicillin-resistant Staph. aureus (MRSA)) and enterococci (including vancomycin-resistant enterococci (VRE)) had their susceptibility to biocides assayed using broth macro dilution methods and resistant strains were selected by serial subculture on biocide-containing media. Mutants were created with relative ease; for instance, triclosan minimal bactericidal concentrations (MBCs) increased from 0.002 to 3.12 mg l(-1). Some strains of MRSA which have intermediate resistance to glycopeptides were demonstrated to have decreased susceptibility to some biocides. Biocide resistance amongst enterococci was demonstrated although there was no clear correlation between biocide and antibiotic resistance. The exact mechanisms of resistance in these strains are still being studied but it is clear that biocide resistance is an important clinical phenomenon.
Anti-Bacterial Agents↗
Otitis media with effusion: the role of Alloiococcus otitidis.
Otitis media with effusion (OME) is a common condition that can cause deafness as well as speech and behavioural disturbance. It has long been considered to be a noninfective process resulting from Eustachian tube dysfunction; however, molecular biological techniques have implicated bacteria in the aetiology of this condition. One such organism is Alloiococcus otitidis, which has been detected in middle ear fluid of patients with OME which has not yielded micro-organisms with conventional microbiological culture methods. The exact role of this infectious agent in the pathogenesis of otitis media has yet to be elucidated.
Ear, Middle↗
Nature of transposon-mediated high-level gentamicin resistance in Enterococcus faecalis isolated in the United Kingdom.
Forty-two high-level gentamicin-resistant (MIC > 1000 mg/L) strains of Enterococcus faecalis, isolated from diverse geographical locations throughout the UK between 1993 and 1995, were studied to identify the nature of the high-level gentamicin-resistant determinants and the possibility of these determinants being associated with a transposon. High-level gentamicin resistance was attributed to the synthesis of the bifunctional (AAC6'-APH2") aminoglycoside-modifying enzyme. The aac6'-aph2" gene, which was present on a 70 kb plasmid in all 42 isolates, could be transferred by conjugation in association with the 70 kb plasmid in 39 of the isolates studied. In three E. faecalis isolates, however, the high-level gentamicin resistance was transferable independent of the 70 kb plasmid, suggesting the presence of a conjugative transposon. Long-PCR studies showed that all 42 clinical isolates harboured a transposon similar to Tn5281, originally identified in E. faecalis strain HH22 isolated in the USA. Restriction endonuclease and Southern hybridization analysis of the UK transposon showed that it is closely related to the high-level gentamicin resistance-conferring transposon Tn5281. However, the UK transposon lacks the HaeIII site identified in Tn5281. Pulsed-field gel electrophoresis analysis identified seven different patterns. Further studies with nine restriction endonucleases showed that the aac6'-aph2" gene was associated with nine different plasmid types in E. faecalis.
Anti-Bacterial Agents↗
Detection of Alloiococcus otitis in mixed bacterial populations from middle-ear effusions of patients with otitis media.
BACKGROUND: Otitis media is a potentially serious disorder, since there is a risk of permanent hearing loss. Culture methods are not useful in characterisation of populations of bacteria in the middle ear. We have used a PCR-based method that does not depend on prior knowledge of the bacteria identified by culture. METHODS: Middle-ear effusion fluid was obtained from 12 patients with chronic otitis media with effusion. Total DNA was extracted from the samples, and the hypervariable regions of bacterial 16S rRNA genes were amplified by means of broad-range PCR primers. Individual PCR products were segregated by cloning to allow analysis of mixed bacterial populations. FINDINGS: Many bacterial species were detected by PCR, whereas with culture-based approaches, no bacterial growth was detected for ten of the 12 patients. The gram-positive bacterium Alloiococcus otitis (A. otitidis) was detected by 16S rDNA amplification in six of the twelve samples, but not by culture techniques. Interpretation The method may have general usefulness in characterising bacterial populations at the site of infection and may indicate, from small sample numbers, organisms that are candidates for further investigation.
Adult↗
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.
Aldehydes↗
Choosing disinfectants.
Disinfectant choice is an important part of the role of the infection control team. Its importance has increased due to concern over transmission of blood-borne viruses and the need to identify alternatives to gluteraldehyde. Factors to be taken into account when choosing disinfectants include compliance with COSHH regulations, user acceptability, instrument compatibility and antimicrobial activity. Compounds vary in their suitability for different uses and an agent's properties must be fully evaluated before adopting it for a particular purpose. This review outlines the main properties that need to be established and covers the major characteristics of main classes of disinfectants.
Cross Infection↗
Plasmid heterogeneity and identification of a Tn5281-like element in clinical isolates of high-level gentamicin-resistant Enterococcus faecium isolated in the UK.
Ten clinical isolates of high-level gentamicin-resistant (HLGR) Enterococcus faecium, collected from six hospitals throughout the UK, were studied to determine whether HLGR was attributed to widespread dissemination of a single plasmid or whether different plasmid types were implicated in the dissemination of this phenotype. HLGR was attributed to the presence of the AAC6'-APH2" bifunctional aminoglycoside modifying enzyme. The aac6'-aph2" gene was present on a 70 kb plasmid in all ten isolates. Conjugation studies indicated that the HLGR marker could transfer with varying frequency, with or without the associated 70 kb plasmid. Detailed molecular genetic analysis suggested that four of the isolates harboured a transposon similar to Tn5281, originally identified in Enterococcus faecalis strain HH22 isolated in the USA. The UK transposon, however, lacked the two symmetrically located HaeIII sites found in Tn5281. The six remaining isolates appeared to have a Tn5281-truncated structure in which the aac6'-aph2" gene is flanked by an IS256 element at the 5' end. Further studies with nine restriction endonucleases showed that the aac6'-aph2" gene was associated with two different plasmid types in E. faecium. Pulsed-field gel electrophoresis (PFGE) analysis identified three different patterns. The four E. faecium isolates harbouring the Tn5281-like structure were indistinguishable from each other, while the remaining six isolates exhibited two distinct PFGE patterns. This is the first study to indicate that there is heterogeneity among the plasmids that confer the HLGR phenotype in E. faecium isolates in the UK and to report on the presence of a transposon, similar to Tn5281, in E. faecium harbouring the aac6'-aph2" gene.
Acetyltransferases↗
Reduced glutaraldehyde susceptibility in Mycobacterium chelonae associated with altered cell wall polysaccharides.
Glutaraldehyde-resistant Mycobacterium chelonae have been isolated from endoscope washer disinfectors and endoscope rinse water. The mechanism of glutaraldehyde resistance is not well understood. Two spontaneous, glutaraldehyde-resistant mutants of the sensitive type strain, NCTC 946, were investigated. The colony morphology of the two mutants differed from that of the the type strain: colonies of the former were dry and waxy whereas those of the latter were smooth and shiny. Increased resistance to glutaraldehyde of the mutants was matched by small increases in the MICs of rifampicin and ethambutol but not isoniazid. Both mutants showed increased surface hydrophobicity. No changes were identified in the extractable fatty acids or the mycolic acid components of the cell wall but a reduction in each of the resistant strains in the arabinogalactan/arabinomannan portion of the cell wall was detected.
Aldehydes↗
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.
Chlorine Compounds↗
Guidelines for the control of methicillin-resistant Staphylococcus aureus.
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Anti-Bacterial Agents↗
How useful are microbial filters in respiratory apparatus?
Following an outbreak of hepatitis C in surgical patients in Australia, it has been suggested that transmission can take place as a result of contaminated anaesthetic circuits. It has therefore been recommended that filters should be placed between patients and breathing systems with a new filter being used for each patient. Although nosocomial pneumonia is a major manifestation of hospital-acquired infection, it is unclear whether contamination of ventilator circuits is implicated in the aetiology of this condition. Some data suggest that bacteria cannot survive well in anaesthetic circuits and several studies have failed to demonstrate significant contamination of circuits in clinical situation. Several outbreaks of pneumonia related to contaminated anaesthetic equipment have been described, but many of these were controlled by appropriate decontamination of the respiratory equipment. Although ventilator filters are used by the majority of intensive care units and filters do have the ability to filter bacteria and viruses, there are few data suggesting that the use of filters reduce the rate of pulmonary infections in long-term ventilated patients. Furthermore, to change filters between operations would have significant financial implications, and there is no conclusive evidence that they would reduce cross infection. Until more data are available on the role of filters in both long-term ventilated patients and operations, standard hygienic measures such as appropriate disinfection protocols are still the most effective way of reducing ventilator-associated infections.
Cross Infection↗
Methicillin-resistant Staphylococcus aureus (MRSA) in nursing homes in a major UK city: an anonymized point prevalence survey.
An anonymized point-prevalence survey of methicillin-resistant Staphylococcus aureus (MRSA) carriage was conducted amongst a stratified random sample of nursing home residents in Birmingham, UK, during 1994. Microbiological sampling from noses, fingers and the environment was undertaken. Information about potential risk factors for the acquisition of MRSA was gathered. MRSA was isolated from cultures of the nose or fingers of 33 of the 191 residents who took part in the study (17%) but only 1 of the 33 positive residents had a clinical infection. Although just 10 of the 87 environmental samples were MRSA positive, there was some environmental contamination in most homes. Risk factors for MRSA carriage were hospital admission within the last year (relative prevalence 2.09, 95% CI 1.13-3.88; P < 0.05) and surgical procedures within the last year (relative prevalence 4.02, 95% CI 2.18-7.43; P = 0.002). Phage-typing of the strains revealed similarities with those circulating in Birmingham hospitals. These findings suggest that the prevalence of MRSA in nursing homes in Birmingham was high, and that the strains may have originated in hospitals.
Bacteriophage Typing↗
Glutaraldehyde-resistant Mycobacterium chelonae from endoscope washer disinfectors.
Glutaraldehyde is used to disinfect flexible and other heat-sensitive endoscopes often with the aid of automated systems. Mycobacterium chelonae is being isolated with increasing frequency from these washer disinfectors and processed endoscopes. This has, on occasions, led to misdiagnosis and iatrogenic infections. Recent reports suggest that disinfecting machines, on a sessional or regular basis, with 2% glutaraldehyde may have selected and therefore encouraged the growth of strains of Myco. chelonae, possibly in biofilm, with decreasing susceptibility to glutaraldehyde. In view of this, the resistance of three strains of Myco. chelonae var. chelonae (the type strain NCTC 946 and two machine isolates) was tested against 2% glutaraldehyde and a wide range of alternative disinfectants. Disinfectants tested were a chlorine releasing agent, sodium dichloroisocyanurate at 1000 ppm and 10,000 ppm av Cl, 0.35% peracetic acid (NuCidex, Johnson & Johnson), 70% industrial methylated spirit (IMS), 1% peroxygen compound ('Virkon', Antec International) and 10% succine dialdehyde ('Gigasept', Sanofi Winthrop). Suspension and carrier tests were carried out in the presence and absence of an organic load. Results showed the type strain, which had not been exposed to the selective pressure of disinfectant usage, to be very sensitive to most disinfectants with the exception of 1% Virkon. The washer disinfector isolates, on the other hand, were extremely resistant to 2% glutaraldehyde and showed greater resistance to 1% Virkon and 1000 ppm NaDCC. Purchasing machines in which the entire fluid pathways, including those for delivering rinse water, are disinfected with an appropriate agent during each cycle are preferred. If this is not possible then sessional cleaning and disinfection at the start of each day and regular maintenance should prevent biofilm formation and contamination with disinfectant-resistant strains of mycobacteria. In addition to machine disinfection, the use of sterile or bacteria-free (filtered < 0.45 microm) water is essential for bronchoscopes and all invasive endoscopes. If there is doubt that the effectiveness of the machine disinfection procedure or water quality, the channels and surfaces of endoscopes may be rinsed with 70% IMS after automated processing.
Disinfectants↗
Activity of a new glycopeptide antibiotic (LY333328) against enterococci and other resistant gram-positive organisms.
A new semi-synthetic glycopeptide, LY333328, was tested for in-vitro activity against 197 strains of enterococci including strains resistant to other glycopeptides. Activity was also assessed against species with intrinsic resistance to glycopeptides. For strains of enterococci tested the LY333328 MIC90s were < or = 0.5 mg/L. Enterococcus faecalis was less susceptible to LY333328 than other enterococci with a maximum MIC of 2.0 mg/L. Glycopeptide-resistant strains of enterococci were not more resistant to LY333328 than glycopeptide-susceptible strains but intrinsically resistant species had MICs between 4 and 8 mg/L.
Ampicillin↗