Letters
to the
Editor
311
The Working Party emphasized that the most important precautions are appropriate measures to avoid sharps injuries and observance of basic hygiene precautions with all patients. I find difficulty with Dr Stanley’s comparison of HIV with hepatitis B virus in the management of inoculation incidents in health care staff. Indeed, there is no ‘outcry’ for hepatitis testing; rather, testing of the source patient is a routine matter, which is important in deciding the management of the staff member suffering the injury.” Our knowledge of HIV is always advancing and the manifestations of the infection in our society are constantly changing. Changing epidemiology may require different approaches, and we await with interest the conclusions of various groups of surgeons who are discussing precautions for surgical operations. It was the perception of the Working Party that, in the present situation in most parts of this country, a selective system could be maintained, that attitudes to HIV testing had become irrational and that some return to the approach used in the control of all other infectious diseases would be beneficial.
D. C. E. Speller Chairman Hospital Infection Society, AIDS Working Party
Department of Microbiology, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW
References 1. Working Party of the Hospital Infection Society. Acquired Immune Deficiency Syndrome: recommendations. J Hosp Znfect 1990; 15: 7-34. 2. Advisory Committee on Dangerous Pathogens. HIV-The Causatioe Agent of AIDS and Related Conditions. Second revision of guidelines 1990; iv. 3. Breuer J, Jeffries DJ. Control of viral infections in hospitals. J Hasp Infect 1990; 16: 191-221.
Sir,
Safety
and efficacy
of clinical
waste
incineration
Scott & Jones’ confirm the emission of viable bacteria with the exhaust gases from a modern hospital incinerator although in contrast to our own observations2 (which did not involve study of the Hammersmith Hospital incinerator as suggested by Scott & Jones but a newly constructed clinical waste incinerator elsewhere in central London) persistent escape of viable bacteria was not observed when temperatures exceeding 200°C in the primary combustion chamber were achieved.
312
Letters
to the Editor
Effective incinerator operation requires careful appraisal of the composition and calorific value of the load, its density, volume and load rate. In view of the low temperatures recorded by Scott & Jones during initial firing of the incinerator, it may be appropriate initially to charge incinerator chambers with relatively innocuous loads of high calorific value or to establish normal operating temperatures by the use of supplementary fuel input. However, the actual risks associated with the emission of small numbers of viable bacteria with gases from a suitably positioned high exhaust stack may, in reality, be negligible and these operating requirements may thus be considered unnecessarily inconvenient and expensive although such an approach would be essential if air pollution control standards are to be achieved. Incineration of clinical waste, and of pathology laboratory waste also, is clearly the appropriate route for disposal of these difficult materials. The emission of small numbers of viable bacteria with the exhaust gases from modern incinerators seems likely to be more common with the many old and inadequately maintained manually operated incinerators still in use in the United Kingdom. Allen, Brenniman & Logue3 have also observed the emission of viable bacteria with the exhaust gases of a clinical waste incinerator operating at 760°C. These bacteria were distinct from indicator strains previously seeded into the load and it was concluded that such bacteria may originate not from the combustion chamber but from some more distal and cooler part of the exhaust system. Clearly there is need for combined physiochemical and microbiological study of incinerator operation and considerable investment in design and installation of modern incinerator equipment is overdue. Careful segregation of wastes remains appropriate and consideration should be given to the selection of re-usable items where possible as the increasing use of plastic disposable items normally destined for incineration may add significantly to the potentially harmful emissions from clinical waste incinerators.4 Our work was undertaken as part of a larger study of the emission of environmentally hazardous substances including heavy metals, acidic gases and toxic hydrocarbons (chlorinated dioxins and furans). Clearly, consideration must be given to the risks incurred by incinerator operators, service personnel and other unskilled and generally unsupervised ancillary workers involved in waste disposal. The elimination of environmental pollution is an ultimate goal. The observations of Scott & Jones are encouraging in that it appeared their incinerator proved to be effective in sterilizing the entire load, but further work is necessary to identify and clarify the effectiveness of all incinerators. This becomes of increasing importance considering the many relatively inefficient incinerators available within the National Health Service and may be mandatory with the imminent removal of Crown Immunity from such facilities.
Letters
J. I. Blenkharn D. Oakland*
to the Editor
313
Department of Bacteriology, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 ONN *Oakland Calvert Consultants Limited, South Bank Technopark, London SE1 6LN References
Scott GM, Jones GH. Emission of viable bacteria in the exhaust flue from a waste incinerator. J Hosp Infect 1990; 16: 183-l 84. Blenkharn II, Oakland D. Emission of viable bacteria with the exhaust flue gases from hospital incinerators. J Hosp Infect 1989; 14: 73378. Allen RI. Brenniman GR. Loeue RI,. Emission of airborne bacteria from a hosnital incineramr. J Air Poll Co& A&oc 1989; 39: 164-168. Daschner F. Closed disposable suction systems: need, waste or hazard. J Hasp Infect
1990; 15: 396-397.
Sir,
Laboratory
detection
of P-lactamase-negative, Staphylococcusaureus
methicillin-resistant
We read with interest the report of an outbreak of (j-lactamase-negative methicillin-resistant Staphylococcus aureus (MRSA) in a nursery.’ In Dublin, in contrast to London, p-lactamase production is more usually plasmid encoded rather than chromosomally determined.2a” In the last 18 months we have noted distinguishable p-lactamase negative isolates of MRSA on four separate occasions indicating that in Dublin at least, this is not an uncommon phenomenon. As indicated by Richardson et al.,’ p-lactamase-negative MRSA may be missed in the routine laboratory as they may appear sensitive to penicillin, ampicillin, cephradine, and ‘Augmentin’ (amongst the first line agents likely to be tested against Gram-positive organisms in the diagnostic laboratory). To express phenotypic resistance, incubation at 30°C or on salt-containing media is necessary. Bearing in mind the difficulties encountered with determining methicillin resistance’ it is essential that all methicillin testing be subject to careful scrutiny. We found that directing particular attention to erythromycinresistant S. aureus (as a marker) may highlight the existence of beta-lactamase-negative MRSA.
E. B. McNamara, E. C. Moorhouse, E. G. Smyth*
Royal College of Surgeons in Ireland, Dublin 2, *Department of Microbiology, Beaumont Hospital, Dublin 9
to the
Editor
311
The Working Party emphasized that the most important precautions are appropriate measures to avoid sharps injuries and observance of basic hygiene precautions with all patients. I find difficulty with Dr Stanley’s comparison of HIV with hepatitis B virus in the management of inoculation incidents in health care staff. Indeed, there is no ‘outcry’ for hepatitis testing; rather, testing of the source patient is a routine matter, which is important in deciding the management of the staff member suffering the injury.” Our knowledge of HIV is always advancing and the manifestations of the infection in our society are constantly changing. Changing epidemiology may require different approaches, and we await with interest the conclusions of various groups of surgeons who are discussing precautions for surgical operations. It was the perception of the Working Party that, in the present situation in most parts of this country, a selective system could be maintained, that attitudes to HIV testing had become irrational and that some return to the approach used in the control of all other infectious diseases would be beneficial.
D. C. E. Speller Chairman Hospital Infection Society, AIDS Working Party
Department of Microbiology, Bristol Royal Infirmary, Marlborough Street, Bristol BS2 8HW
References 1. Working Party of the Hospital Infection Society. Acquired Immune Deficiency Syndrome: recommendations. J Hosp Znfect 1990; 15: 7-34. 2. Advisory Committee on Dangerous Pathogens. HIV-The Causatioe Agent of AIDS and Related Conditions. Second revision of guidelines 1990; iv. 3. Breuer J, Jeffries DJ. Control of viral infections in hospitals. J Hasp Infect 1990; 16: 191-221.
Sir,
Safety
and efficacy
of clinical
waste
incineration
Scott & Jones’ confirm the emission of viable bacteria with the exhaust gases from a modern hospital incinerator although in contrast to our own observations2 (which did not involve study of the Hammersmith Hospital incinerator as suggested by Scott & Jones but a newly constructed clinical waste incinerator elsewhere in central London) persistent escape of viable bacteria was not observed when temperatures exceeding 200°C in the primary combustion chamber were achieved.
312
Letters
to the Editor
Effective incinerator operation requires careful appraisal of the composition and calorific value of the load, its density, volume and load rate. In view of the low temperatures recorded by Scott & Jones during initial firing of the incinerator, it may be appropriate initially to charge incinerator chambers with relatively innocuous loads of high calorific value or to establish normal operating temperatures by the use of supplementary fuel input. However, the actual risks associated with the emission of small numbers of viable bacteria with gases from a suitably positioned high exhaust stack may, in reality, be negligible and these operating requirements may thus be considered unnecessarily inconvenient and expensive although such an approach would be essential if air pollution control standards are to be achieved. Incineration of clinical waste, and of pathology laboratory waste also, is clearly the appropriate route for disposal of these difficult materials. The emission of small numbers of viable bacteria with the exhaust gases from modern incinerators seems likely to be more common with the many old and inadequately maintained manually operated incinerators still in use in the United Kingdom. Allen, Brenniman & Logue3 have also observed the emission of viable bacteria with the exhaust gases of a clinical waste incinerator operating at 760°C. These bacteria were distinct from indicator strains previously seeded into the load and it was concluded that such bacteria may originate not from the combustion chamber but from some more distal and cooler part of the exhaust system. Clearly there is need for combined physiochemical and microbiological study of incinerator operation and considerable investment in design and installation of modern incinerator equipment is overdue. Careful segregation of wastes remains appropriate and consideration should be given to the selection of re-usable items where possible as the increasing use of plastic disposable items normally destined for incineration may add significantly to the potentially harmful emissions from clinical waste incinerators.4 Our work was undertaken as part of a larger study of the emission of environmentally hazardous substances including heavy metals, acidic gases and toxic hydrocarbons (chlorinated dioxins and furans). Clearly, consideration must be given to the risks incurred by incinerator operators, service personnel and other unskilled and generally unsupervised ancillary workers involved in waste disposal. The elimination of environmental pollution is an ultimate goal. The observations of Scott & Jones are encouraging in that it appeared their incinerator proved to be effective in sterilizing the entire load, but further work is necessary to identify and clarify the effectiveness of all incinerators. This becomes of increasing importance considering the many relatively inefficient incinerators available within the National Health Service and may be mandatory with the imminent removal of Crown Immunity from such facilities.
Letters
J. I. Blenkharn D. Oakland*
to the Editor
313
Department of Bacteriology, Royal Postgraduate Medical School, Hammersmith Hospital, London W12 ONN *Oakland Calvert Consultants Limited, South Bank Technopark, London SE1 6LN References
Scott GM, Jones GH. Emission of viable bacteria in the exhaust flue from a waste incinerator. J Hosp Infect 1990; 16: 183-l 84. Blenkharn II, Oakland D. Emission of viable bacteria with the exhaust flue gases from hospital incinerators. J Hosp Infect 1989; 14: 73378. Allen RI. Brenniman GR. Loeue RI,. Emission of airborne bacteria from a hosnital incineramr. J Air Poll Co& A&oc 1989; 39: 164-168. Daschner F. Closed disposable suction systems: need, waste or hazard. J Hasp Infect
1990; 15: 396-397.
Sir,
Laboratory
detection
of P-lactamase-negative, Staphylococcusaureus
methicillin-resistant
We read with interest the report of an outbreak of (j-lactamase-negative methicillin-resistant Staphylococcus aureus (MRSA) in a nursery.’ In Dublin, in contrast to London, p-lactamase production is more usually plasmid encoded rather than chromosomally determined.2a” In the last 18 months we have noted distinguishable p-lactamase negative isolates of MRSA on four separate occasions indicating that in Dublin at least, this is not an uncommon phenomenon. As indicated by Richardson et al.,’ p-lactamase-negative MRSA may be missed in the routine laboratory as they may appear sensitive to penicillin, ampicillin, cephradine, and ‘Augmentin’ (amongst the first line agents likely to be tested against Gram-positive organisms in the diagnostic laboratory). To express phenotypic resistance, incubation at 30°C or on salt-containing media is necessary. Bearing in mind the difficulties encountered with determining methicillin resistance’ it is essential that all methicillin testing be subject to careful scrutiny. We found that directing particular attention to erythromycinresistant S. aureus (as a marker) may highlight the existence of beta-lactamase-negative MRSA.
E. B. McNamara, E. C. Moorhouse, E. G. Smyth*
Royal College of Surgeons in Ireland, Dublin 2, *Department of Microbiology, Beaumont Hospital, Dublin 9
