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The contamination of gowns in an intensive care unit
Journal of Hospital Infection (1981) 2, 167-l 70
The contamination
of gowns in an intensive care unit Bertil
Nystriim
Department of Clinical Microbiology, Huddinge Hospital, S-141 86 Huddinge, Sweden Summary: The bacterial contamination of protective gowns used for 6 and for 24 h in an intensive care unit has been compared with the contamination of protective gowns used in a normal ward. There was no significant difference in the mean contamination level between the three groups of gowns studied, indicating that a more frequent change to new, clean gowns than every 24 h in the intensive care unit and twice weekly in the normal ward would be of little practical significance. However, on occasional gowns in the intensive care unit very high bacterial to prevent dissemination counts were observed. If it is of practical significance of infection from such heavily contaminated protective gowns, and disposable plastic aprons might be a useful alternative. Introduction
Hambraeus (1973) h as investigated the role of gowns in the dissemination of infection in a burns’ unit. Her reports and others similar have resulted in a widespread use of protective gowns for nursing procedures in many Swedish hospitals. Protective gowns are used by the staff when nursing patients in one room and may not be used in other ward rooms. Thus, in one-patient rooms the gown is used only for one patient. The purpose is to minimize dissemination of infection between patients from the clothes of the staff. Hambraeus (1973) has demonstrated that some dissemination still may occur as some micro-organisms penetrate the gown to the clothes worn under it. As these clothes are not changed between rooms, and micro-organisms on them relatively freely penetrate the gown, the protective gowns do not offer a complete protection against clothes-borne transmission of micro-organisms between patients. However, they should substantially diminish this hazard. The general rule in many Swedish hospitals is that protective gowns should be changed twice weekly, more often if they have been grossly soiled. However, in isolation rooms for infected. patients as well as in intensive care and similar units they should be changed every 24 h, more often if they are grossly soiled. It has been questioned whether this frequency of gown changes is sufficient or whether a more frequent change could further prevent dissemination of infection. The purpose of this investigation has been to study the contamination of protective gowns in an intensive care unit after 6 and after 24 h use and to compare it with the contamination of protective gowns in an ordinary ward. 0
167
1981 Academic
Press
Inc.
(London)
Limited
B. NystrSm
168
Materials
and methods
The study was performed in the intensive care unit of Huddinge hospital, treating surgical as well as internal medicine patients, and an orthopaedic surgery ward at the same hospital. In the intensive care unit most patient rooms are isolation rooms with an anteroom also functioning as an air-lock. In this ante-room everybody entering the patient room puts on a protective gown, which is taken off again in the ante-room when the person leaves. The staff of the unit wear a jacket and trousers, or a dress, during work, and the gown is worn over these clothes. Visitors wear their ordinary clothes under the gown. In the orthopaedic surgery ward all patient rooms, whether for one or for several patients, have an ante-room. No patient room has more than four beds. All members of staff put on a protective gown in the ante-room before carrying out nursing procedures in the patients room. The gown is not usually changed between nursing procedures on several patients in the same room, but it is always taken off when leaving the patient room. The staff wear a jacket and trousers, or a coat, during the working day. The protective gown is worn over these clothes. In the intensive care unit 20 protective gowns were selected at random from various isolation rooms after approximately 6 h of use, and 20 gowns after 24 h of use. In the orthopaedic surgery ward, 10 protective gowns were selected at random from various patient rooms. They had been used for a varying length of time, at least half a day and not more than three days. From each gown a 1 cm2 piece was cut out in the middle of the front side at chest level. The textile square was cut up as finely as possible with sterile scissors into physiological saline containing 5 per cent nutrient broth. The fluid was treated in a homogenizer (Sorvall Omnimixer). Surface viable counts were performed on serial dilutions of the homogenized fluid on blood agar plates. This method of determining the bacterial contamination on pieces of textile was originally described by Jerram (1958). Results
Table I gives the mean number of micro-organisms per cm2, the standard deviation, the median and the range. In brackets are the corresponding figures after the highest count in each of the two series of gowns from the intensive care unit was discarded. Table
I. Contamination Counts
Site Intensive care unit Intensive care unit Normal ward
of gowns of micro-organisms/cm2
Time in use
n
Mean
s.d.
Median
Range
6 h 24 h
20 (19) f; (19)
1351 (133) 4; (228)
5453 (227) 1:;: (191)
63 (55) 1;; (148)
l-24 500 (l-992) ;;%54:0 (18-635)
Mean and median number of micro-organisms/cm2 on protective gowns, standard deviation (s.d.), range and number of observations (n). In brackets the corresponding figures are shown after the highest count observed in each intensive care series was discarded.
Contamination
of gowns
169
The mean count of micro-organisms per cm2 of textile was approximately 10 times higher on gowns used for 6 h in the intensive care unit as on gowns used for up to three days in the orthopaedic surgery ward. However, this mean number was greatly influenced by a single very high value. If the highest count was disregarded, the mean count was very similar for gowns used 6 or 24 h in the intensive care unit and for gowns used in the orthopaedic surgery ward. The differences found were not statistically significant. The highest count in the study was found on one gown used for 6 h in the intensive care unit which carried 24,500 micro-organisms per cm2. On one gown used for 24 h in the intensive care unit 5400 micro-organisms/cm2 were found, but on all other gowns less than lo3 micro-organisms per cm2.
Discussion
The method used in this investigation to study the bacterial contamination on a small piece of textile is reasonably accurate with not more than an approximately fourfold loss. However, the contamination is measured on a 1 cm2 area, cut out at chest level. Whether the contamination level varies between various parts of the gown has not been studied. Neither has it been studied whether the chest area is more representative than, e.g. the ‘apron area’ (Speers et al., 1969). However, it appears likely that the chest area is easily contaminated in intensive care where tracheal suctions, etc., are common procedures. In this investigation the mean contamination level on protective gowns at chest level was some lo2 per cm2, whether they were used for 6 or 24 h in one-patient rooms in the intensive care unit or for up to three days in up to four-bedded rooms in an orthopaedic surgery ward. Among the gowns used in the intensive care unit, however, two out of 40 carried 5 x lo3 and 2.5 x lo* micro-organisms per cm2, respectively. It is difficult or impossible to judge the risks to the patients of a contamination level of this order on the protective gowns. The danger may be higher to a patient in a multi-bedded room where the same gown is often used for several patients than to the patient in the one-patient room. On the other hand the isolated patient in the intensive care unit is often more infection-prone than the patient in the ordinary ward. It cannot, however, be ruled out that a protective gown contaminated with some lo4 micro-organisms per cm2 on an area that is in direct contact with the patient might be a hazard. It appears from this investigation that such a hazard should probaly not be met with more frequent changes of ordinary protective gowns, as contamination of that order was only seen on one gown out of 20 after 6 h use, and more frequent changes than that would hardly be practicable. It may well be that disposable plastic aprons would be a better alternative than ordinary protective gowns in areas where transfer mechanisms of this type are considered a substantial hazard. Lidwell et al. (1974) as well as Ransjij (1979) have indicated their efficiency.
170
B. Nystram References
Hambraeus, A. (1973). Transfer of Staphylococcus aureus via nurses’ uniforms. Journal of Hygiene, Cambridge 71, 799-814. Jerram, P. (1958). An investigation into the ability of laundry processes to kill pathogenic bacteria in soiled articles. Monthly Bulletin of the Ministry of Health and the Public Health Laboratory Service 17, 170. Lidwell, 0. M., Towers, A. G., Ballard, J. & Gladstone, B. (1974). Transfer of microorganisms between nurses and patients in a clean air environment. Journal of Applied Bacteriology 37, 649-656. Ransjij, U. (1979). Attempts to control clothes-borne infection in a bum unit, 3. An openroofed plastic isolator or plastic aprons to prevent contact transfer of bacteria. Journal of Hygiene, Cambridge 82, 385-395. Speers, R., Shooter, R. A., Gaya, H., Patel, N. & Hewitt, J. H. (1969). Contamination of nurses’ uniforms with Staphylococcus aureus. Lancet ii, 233.
The contamination
of gowns in an intensive care unit Bertil
Nystriim
Department of Clinical Microbiology, Huddinge Hospital, S-141 86 Huddinge, Sweden Summary: The bacterial contamination of protective gowns used for 6 and for 24 h in an intensive care unit has been compared with the contamination of protective gowns used in a normal ward. There was no significant difference in the mean contamination level between the three groups of gowns studied, indicating that a more frequent change to new, clean gowns than every 24 h in the intensive care unit and twice weekly in the normal ward would be of little practical significance. However, on occasional gowns in the intensive care unit very high bacterial to prevent dissemination counts were observed. If it is of practical significance of infection from such heavily contaminated protective gowns, and disposable plastic aprons might be a useful alternative. Introduction
Hambraeus (1973) h as investigated the role of gowns in the dissemination of infection in a burns’ unit. Her reports and others similar have resulted in a widespread use of protective gowns for nursing procedures in many Swedish hospitals. Protective gowns are used by the staff when nursing patients in one room and may not be used in other ward rooms. Thus, in one-patient rooms the gown is used only for one patient. The purpose is to minimize dissemination of infection between patients from the clothes of the staff. Hambraeus (1973) has demonstrated that some dissemination still may occur as some micro-organisms penetrate the gown to the clothes worn under it. As these clothes are not changed between rooms, and micro-organisms on them relatively freely penetrate the gown, the protective gowns do not offer a complete protection against clothes-borne transmission of micro-organisms between patients. However, they should substantially diminish this hazard. The general rule in many Swedish hospitals is that protective gowns should be changed twice weekly, more often if they have been grossly soiled. However, in isolation rooms for infected. patients as well as in intensive care and similar units they should be changed every 24 h, more often if they are grossly soiled. It has been questioned whether this frequency of gown changes is sufficient or whether a more frequent change could further prevent dissemination of infection. The purpose of this investigation has been to study the contamination of protective gowns in an intensive care unit after 6 and after 24 h use and to compare it with the contamination of protective gowns in an ordinary ward. 0
167
1981 Academic
Press
Inc.
(London)
Limited
B. NystrSm
168
Materials
and methods
The study was performed in the intensive care unit of Huddinge hospital, treating surgical as well as internal medicine patients, and an orthopaedic surgery ward at the same hospital. In the intensive care unit most patient rooms are isolation rooms with an anteroom also functioning as an air-lock. In this ante-room everybody entering the patient room puts on a protective gown, which is taken off again in the ante-room when the person leaves. The staff of the unit wear a jacket and trousers, or a dress, during work, and the gown is worn over these clothes. Visitors wear their ordinary clothes under the gown. In the orthopaedic surgery ward all patient rooms, whether for one or for several patients, have an ante-room. No patient room has more than four beds. All members of staff put on a protective gown in the ante-room before carrying out nursing procedures in the patients room. The gown is not usually changed between nursing procedures on several patients in the same room, but it is always taken off when leaving the patient room. The staff wear a jacket and trousers, or a coat, during the working day. The protective gown is worn over these clothes. In the intensive care unit 20 protective gowns were selected at random from various isolation rooms after approximately 6 h of use, and 20 gowns after 24 h of use. In the orthopaedic surgery ward, 10 protective gowns were selected at random from various patient rooms. They had been used for a varying length of time, at least half a day and not more than three days. From each gown a 1 cm2 piece was cut out in the middle of the front side at chest level. The textile square was cut up as finely as possible with sterile scissors into physiological saline containing 5 per cent nutrient broth. The fluid was treated in a homogenizer (Sorvall Omnimixer). Surface viable counts were performed on serial dilutions of the homogenized fluid on blood agar plates. This method of determining the bacterial contamination on pieces of textile was originally described by Jerram (1958). Results
Table I gives the mean number of micro-organisms per cm2, the standard deviation, the median and the range. In brackets are the corresponding figures after the highest count in each of the two series of gowns from the intensive care unit was discarded. Table
I. Contamination Counts
Site Intensive care unit Intensive care unit Normal ward
of gowns of micro-organisms/cm2
Time in use
n
Mean
s.d.
Median
Range
6 h 24 h
20 (19) f; (19)
1351 (133) 4; (228)
5453 (227) 1:;: (191)
63 (55) 1;; (148)
l-24 500 (l-992) ;;%54:0 (18-635)
Mean and median number of micro-organisms/cm2 on protective gowns, standard deviation (s.d.), range and number of observations (n). In brackets the corresponding figures are shown after the highest count observed in each intensive care series was discarded.
Contamination
of gowns
169
The mean count of micro-organisms per cm2 of textile was approximately 10 times higher on gowns used for 6 h in the intensive care unit as on gowns used for up to three days in the orthopaedic surgery ward. However, this mean number was greatly influenced by a single very high value. If the highest count was disregarded, the mean count was very similar for gowns used 6 or 24 h in the intensive care unit and for gowns used in the orthopaedic surgery ward. The differences found were not statistically significant. The highest count in the study was found on one gown used for 6 h in the intensive care unit which carried 24,500 micro-organisms per cm2. On one gown used for 24 h in the intensive care unit 5400 micro-organisms/cm2 were found, but on all other gowns less than lo3 micro-organisms per cm2.
Discussion
The method used in this investigation to study the bacterial contamination on a small piece of textile is reasonably accurate with not more than an approximately fourfold loss. However, the contamination is measured on a 1 cm2 area, cut out at chest level. Whether the contamination level varies between various parts of the gown has not been studied. Neither has it been studied whether the chest area is more representative than, e.g. the ‘apron area’ (Speers et al., 1969). However, it appears likely that the chest area is easily contaminated in intensive care where tracheal suctions, etc., are common procedures. In this investigation the mean contamination level on protective gowns at chest level was some lo2 per cm2, whether they were used for 6 or 24 h in one-patient rooms in the intensive care unit or for up to three days in up to four-bedded rooms in an orthopaedic surgery ward. Among the gowns used in the intensive care unit, however, two out of 40 carried 5 x lo3 and 2.5 x lo* micro-organisms per cm2, respectively. It is difficult or impossible to judge the risks to the patients of a contamination level of this order on the protective gowns. The danger may be higher to a patient in a multi-bedded room where the same gown is often used for several patients than to the patient in the one-patient room. On the other hand the isolated patient in the intensive care unit is often more infection-prone than the patient in the ordinary ward. It cannot, however, be ruled out that a protective gown contaminated with some lo4 micro-organisms per cm2 on an area that is in direct contact with the patient might be a hazard. It appears from this investigation that such a hazard should probaly not be met with more frequent changes of ordinary protective gowns, as contamination of that order was only seen on one gown out of 20 after 6 h use, and more frequent changes than that would hardly be practicable. It may well be that disposable plastic aprons would be a better alternative than ordinary protective gowns in areas where transfer mechanisms of this type are considered a substantial hazard. Lidwell et al. (1974) as well as Ransjij (1979) have indicated their efficiency.
170
B. Nystram References
Hambraeus, A. (1973). Transfer of Staphylococcus aureus via nurses’ uniforms. Journal of Hygiene, Cambridge 71, 799-814. Jerram, P. (1958). An investigation into the ability of laundry processes to kill pathogenic bacteria in soiled articles. Monthly Bulletin of the Ministry of Health and the Public Health Laboratory Service 17, 170. Lidwell, 0. M., Towers, A. G., Ballard, J. & Gladstone, B. (1974). Transfer of microorganisms between nurses and patients in a clean air environment. Journal of Applied Bacteriology 37, 649-656. Ransjij, U. (1979). Attempts to control clothes-borne infection in a bum unit, 3. An openroofed plastic isolator or plastic aprons to prevent contact transfer of bacteria. Journal of Hygiene, Cambridge 82, 385-395. Speers, R., Shooter, R. A., Gaya, H., Patel, N. & Hewitt, J. H. (1969). Contamination of nurses’ uniforms with Staphylococcus aureus. Lancet ii, 233.