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CONTAMINATION OF INFANT FEEDS IN A MILTON MILK KITCHEN
559 with water and milk kitchen by
Public Health CONTAMINATION OF INFANT FEEDS IN A MILTON MILK KITCHEN B. J. COLLINS FELICITY PETTIT Research Laboratory, Summerfield Hospital, Hospital Infection
G. A. J. AYLIFFE
Birmingham Summary of
Infant feeds
18
prepared in a milk kitchen
a large maternity hospital
were
be contaminated with Klebsiella aerogenes lesser and, extent, with Escherichia coli, PseudoStrains of monas œruginosa, and other organisms. K. aerogenes and Ps. œruginosa were typed, the former by bacteriocine and the latter by phage and serological methods. The same types of K. aerogenes and Ps. œruginosa were found in milk feeds and in the faces of babies who had received the milk; they were also found in the tap of a mixing container, which was considered to be the major source of contamination of feeds. Mixing containers, dispensers, bottles, and taps were thoroughly cleaned and then disinfected in a solution of hypochlorite: the taps could not be effectively cleaned before disinfection. A safer process of disinfection or terminal sterilisation is recommended.
found
to to a
INTRODUCTION
INFANT-FEEDING bottles, teats, and sometimes mixing and dispensing equipment are still disinfected with hypochlorite solution in many hospital milk kitchens. Although a Medical Research Council report1 indicated that chemical disinfection was satisfactory if correctly performed, some reports suggest that this process is not always effective. Robson and Anderson2 suggested that candida infection may be spread by teats which are not adequately disinfected by hypochlorite. Babies’ feeds, if they are not adequately protected or treated, may be heavily contaminated with a variety of bacteria, including faecal organisms, and it is thought that infantile gastroenteritis may sometimes be spread by contaminated milk.3,4 Following an investigation in a maternity hospital of an outbreak of mild gastroenteritis caused by an enteropathogenic strain of Escherichia coli, the infant feeds were examined and found to be contaminated with gram-negative bacilli. We describe here the results and conclusions of the investigation. DESCRIPTION OF MILK KITCHEN AND PREPARATION OF FEEDS
The maternity hospital contained a total of 166 beds; 28 beds were not in use at the time of the study, 40 were occupied by antenatal patients, and 22 were in the specialcare unit. The milk kitchen supplied approximately 400 feeds per day. Feeds were prepared by mixing sterile tinned milk and tap-water in a polyethylene container; a sterile glucose solution was added when required. After mixing, the feed was passed through a tap into a polyethylene dispenser and from there measured into the feeding-bottles. The bottles were closed with rubber caps, delivered to the wards and stored in a refrigerator until required; feeds were discarded if not used within 24 hours. After use, bottles and caps were thoroughly brushed and washed
detergent in a room separated from the glass partition. The clean bottles, caps, mixing containers, and dispensers were stored overnight in a large tank containing 1% sodium-hypochlorite solution (‘ Milton’) diluted 1 in 80. Taps were dismantled as completely as possible before being placed in the disinfectant, but the interior of the taps of the mixing containers could be cleaned only with difficulty. A separate teat was kept for each baby in a container of diluted milton in a locker a
a
the side of each cot. Feeds were prepared by two nurses, who wore masks and gowns and washed their hands with a povidone-iodine preparation before entering the milk kitchen. Although the milk kitchen was small, the general hygienic standards appeared to be satisfactory. at
.
S Sampling
METHODS
Samples of milk from the milk kitchen were collected from six bottles on three occasions. Samples were also collected from the milk in the mixing containers, dispensers, tap-water, tinned milk, glucose solution, and milton solution after use. After removal from the milton tank, ten bottle-caps and the insides of ten bottles were rinsed in 20 ml. of sterile Ringer’s solution. Samples of fxces were collected for bacterial culture from 9 babies in the specialcare unit and 15 normal, full-term babies in another ward. Bacteriological 0-5 ml. of each fluid was spread on a McConkey plate and allowed to dry, 0-5 ml. was also transferred to 3 ml. of nutrient broth. The milk feeds were cultured within 2 hours of preparation. Fxces were cultured on McConkeys’ medium and in nutrient broth. After 24 hours’ incubation, all broth cultures were subcultured to McConkey agar and improved cetrimide agar.5 Klebsiella spp., isolated from the milk feeds, the taps, and fxces, were identified biochemically, and antibioticsensitivity tests were made by the disc method. Colonies of E. coli were examined serologically to detect the presence of enteropathogenic strains. Klebsiella strains were typed by a bacteriocine method.6 Strains of Pseudomonas aeruginosa were typed by serological and phage-typing methods at the Central Public Health
Laboratory, Colindale. RESULTS
Samples of the milk feed from all bottles examined and from the dispenser showed 100-400 colonies per ml. of K. aerogenes; smaller numbers of E. coli, Ps. aeruginosa, and other organisms were also isolated from most samples. Gram-negative bacilli were not isolated from tap-water, glucose solution, tinned milk, or the milk mixture in the mixing container. After being passed through the tap of the mixing container the milk feed was contaminated with K. aerogenes. This tap appeared to be the immediate source of the heavy contamination. No growth was obtained on primary culture from clean bottles or rubber caps, but, on subculture from nutrient broth, Ps. aeruginosa was isolated from the rubber caps and from one bottle, and K. aerogenes was isolated from another bottle. No organisms were isolated from the milton solutions. K. aerogenes was isolated from 21,24 and Ps. aruginosa from 11/24 samples of fxces. K. aerogenes isolated from milk and facces showed similar biochemical reactions, antibiotic sensitivity, and bacteriocine patterns. Two serotypes of Ps. aruginosa with similar phage patterns were isolated from both milk and fxces. No strains of enteropathogenic E. coli were isolated from the milk.
560 DISCUSSION
Clinical infection due to Klebsiella spp. or Ps. aeruginosa was not observed during the period of study, but a neonate had died of a Ps. ceruginosa infection 1 year previously in the hospital. At that time Ps. ceruginosa was isolated also from the fxces of many babies examined, but the phage types and serotypes were mainly different from those isolated in the present study. Although the feeds were not examined at the time of the fatal infection, these may have been an important source. A greater possible hazard of contamination would be the replacement of the present flora in the milk by Salmonella spp. or enteropathogenic E. coli. Since the milk kitchen supplies feeds for all the babies in the hospital, an extensive outbreak of infection could occur. It was not surprising that similar organisms were isolated from milk and f2eces; but some of the faeces showed heavy and almost pure growths of K. aerogenes, indicating probable colonisation. No follow-up examination of the fseces of these babies was made. Most of the strains of K. aerogenes were resistant only to ampicillin, and, although resistance to this antibiotic was not transferable to E. coli K.12 in vitro, contaminated feeds might account in some instances for the presence of antibiotic-resistant strains of E. coli in babies’ faeces.77 The immediate source of contamination of the feeds appeared to be a polyethylene tap on the mixing container. Replacement of this tap with a rubber bung and tubing, which could be autoclaved daily, was followed by a considerable reduction of bacterial counts in the feeds. However, the system as a whole was still not entirely satisfactory since occasional strains of K. aerogenes and Pseudomonas spp. were isolated from disinfected bottles and teats both before and after the new routine. Milton is a stabilised 1 % hypochlorite solution and is usually diluted 1 in 80 for use. The low content of available chlorine in in-use " solutions is readily inactivated by small amounts of organic matter. The technique of disinfection with milton should be satisfactory if scrupulous attention is paid to cleanliness.8,9 However, the present study indicates that the process using a hypochlorite solution may occasionally be hazardous, even when cleaning appears to be efficient. Chemical disinfection should be replaced in hospitals by a safer method-e.g., terminal heat sterilisation or disinfection,’aseptically prepared "feeds and disposable bottles,’or ready-to-use sterile feeds .12 All processes should be examined bacteriologically at regular intervals. We thank Dr. M. T. Parker and his colleagues for typing the strains of Ps. aeruginosa, Mr. C. Deverill for technical assistance, and the medical and nursing staff of the Maternity Hospital for "
"
their cooperation. REFERENCES 1. Medical Research Council Report. Mon. Bull. Minist. Hlth, 1953, 12, 214. 2. Robson, A., Anderson, K. Med. J. Aust. 1964, i, 519. 3. Cummings, J. G. J. Pediat. 1949, 34, 711. 4. Wright, J. Br. med. J. 1951, ii, 138. 5. Brown, V. I., Lowbury, E. J. L. J. clin. Path. 1965, 18, 752. 6. Pettit, F. Unpublished. 7. Moorhouse, E. C. Br. med. J. 1969, ii, 405. 8. Farquhar, J. W., Gould, J. C., Schutt, W. H. Lancet, 1965, i, 951. 9. Lincoln, P. A., Breach, G. D., Davis, J. G. Med. Offr, 1965, 114, 169. 10. Hughes, K. E. A., Darmady, E. M., Drewett, S. E. J. clin. Path. 1966, 19, 321. 11. Gamsu, H. R., Cawdery, H. M., Taylor, C. G. Lancet, 1969, ii, 1049. 12. Pugh, R. J. ibid. p. 1190.
PSEUDOMONAS ÆRUGINOSA INFECTION IN A NEONATAL
NURSERY,
POSSIBLY TRANSMITTED BY A BREAST-MILK PUMP A. R. THOM
Department of Pathology, Royal Hospital for Sick Children, Bristol 2
KRISTINA WATRASIEWICZ
A. P. COLE
Departments of Pœdiatrics and Pathology, Southmead
Hospital, Bristol
The introduction of a mechanical breast-milk pump into a neonatal was followed nursery by an outbreak of infection by Pseudomonas œruginosa. Investigation revealed that the pump, despite disinfection with a hypochlorite solution, was contaminated by the infecting strain. A simulated " in-use " test showed that, although the hypochlorite was bactericidal and was being used correctly, it failed to disinfect the apparatus. These findings demonstrate once again the unreliability of chemical disinfection. When chemical methods must be used, their efficacy should be checked by realistic " in-use " tests.
Sum ary
INTRODUCTION
Many hospital infections have resulted from the disinfect re-used apparatus. Ita Some have been attributed to lack of potency of the disinfectant against the infecting organisms, but the failure which we here report occurred although the hypochlorite disinfectant (’ Milton’, Vick International Ltd., London) was demonstrably active against the
failure of chemicals
to
organism. THE OUTBREAK
Since June, 1969, the infants in a neonatal nursery had been routinely screened twice weekly for the presence of salmonellae, shigellea, enteropathogenic Escherchia coli, and Pseudomonas ceruginosa. Rectal swabs were plated on standard bacteriological media, and placed in a selective medium for pseudomonasnutrient broth containing 0-1 mg. per ml. of nitrofurantoin. From 5 out of 25 neonates who were swabbed on July 30, 1969, profuse growths of Ps. aeruginosa were isolated on MacConkey agar and the selective medium. Previous batches of swabs had never contained more than one positive. The infected infants were all full-term and had previously progressed normally. Within a day of the isolation 2 developed vomiting and diarrhoea which lasted for about thirty-six hours. No other cause for the symptoms could be found. The other 3 infants were
symptom-free.
On July 31, rectal swabs were again taken from all infants and in addition from their mothers, but only the same 5 infants were positive. Saline-moistened swabs were taken from thermometer pots, sinks, incubators, balance pans, and parts of an’Egnell’ breast-milk pump (Pump AB, Einar Egnell, Sweden) which had been introduced into the nursery some four weeks previously. Swabs were also taken from the two vessels of hypochlorite solution in which these partsbreast cups, safety bottle, milk bottle, and the plastic
Public Health CONTAMINATION OF INFANT FEEDS IN A MILTON MILK KITCHEN B. J. COLLINS FELICITY PETTIT Research Laboratory, Summerfield Hospital, Hospital Infection
G. A. J. AYLIFFE
Birmingham Summary of
Infant feeds
18
prepared in a milk kitchen
a large maternity hospital
were
be contaminated with Klebsiella aerogenes lesser and, extent, with Escherichia coli, PseudoStrains of monas œruginosa, and other organisms. K. aerogenes and Ps. œruginosa were typed, the former by bacteriocine and the latter by phage and serological methods. The same types of K. aerogenes and Ps. œruginosa were found in milk feeds and in the faces of babies who had received the milk; they were also found in the tap of a mixing container, which was considered to be the major source of contamination of feeds. Mixing containers, dispensers, bottles, and taps were thoroughly cleaned and then disinfected in a solution of hypochlorite: the taps could not be effectively cleaned before disinfection. A safer process of disinfection or terminal sterilisation is recommended.
found
to to a
INTRODUCTION
INFANT-FEEDING bottles, teats, and sometimes mixing and dispensing equipment are still disinfected with hypochlorite solution in many hospital milk kitchens. Although a Medical Research Council report1 indicated that chemical disinfection was satisfactory if correctly performed, some reports suggest that this process is not always effective. Robson and Anderson2 suggested that candida infection may be spread by teats which are not adequately disinfected by hypochlorite. Babies’ feeds, if they are not adequately protected or treated, may be heavily contaminated with a variety of bacteria, including faecal organisms, and it is thought that infantile gastroenteritis may sometimes be spread by contaminated milk.3,4 Following an investigation in a maternity hospital of an outbreak of mild gastroenteritis caused by an enteropathogenic strain of Escherichia coli, the infant feeds were examined and found to be contaminated with gram-negative bacilli. We describe here the results and conclusions of the investigation. DESCRIPTION OF MILK KITCHEN AND PREPARATION OF FEEDS
The maternity hospital contained a total of 166 beds; 28 beds were not in use at the time of the study, 40 were occupied by antenatal patients, and 22 were in the specialcare unit. The milk kitchen supplied approximately 400 feeds per day. Feeds were prepared by mixing sterile tinned milk and tap-water in a polyethylene container; a sterile glucose solution was added when required. After mixing, the feed was passed through a tap into a polyethylene dispenser and from there measured into the feeding-bottles. The bottles were closed with rubber caps, delivered to the wards and stored in a refrigerator until required; feeds were discarded if not used within 24 hours. After use, bottles and caps were thoroughly brushed and washed
detergent in a room separated from the glass partition. The clean bottles, caps, mixing containers, and dispensers were stored overnight in a large tank containing 1% sodium-hypochlorite solution (‘ Milton’) diluted 1 in 80. Taps were dismantled as completely as possible before being placed in the disinfectant, but the interior of the taps of the mixing containers could be cleaned only with difficulty. A separate teat was kept for each baby in a container of diluted milton in a locker a
a
the side of each cot. Feeds were prepared by two nurses, who wore masks and gowns and washed their hands with a povidone-iodine preparation before entering the milk kitchen. Although the milk kitchen was small, the general hygienic standards appeared to be satisfactory. at
.
S Sampling
METHODS
Samples of milk from the milk kitchen were collected from six bottles on three occasions. Samples were also collected from the milk in the mixing containers, dispensers, tap-water, tinned milk, glucose solution, and milton solution after use. After removal from the milton tank, ten bottle-caps and the insides of ten bottles were rinsed in 20 ml. of sterile Ringer’s solution. Samples of fxces were collected for bacterial culture from 9 babies in the specialcare unit and 15 normal, full-term babies in another ward. Bacteriological 0-5 ml. of each fluid was spread on a McConkey plate and allowed to dry, 0-5 ml. was also transferred to 3 ml. of nutrient broth. The milk feeds were cultured within 2 hours of preparation. Fxces were cultured on McConkeys’ medium and in nutrient broth. After 24 hours’ incubation, all broth cultures were subcultured to McConkey agar and improved cetrimide agar.5 Klebsiella spp., isolated from the milk feeds, the taps, and fxces, were identified biochemically, and antibioticsensitivity tests were made by the disc method. Colonies of E. coli were examined serologically to detect the presence of enteropathogenic strains. Klebsiella strains were typed by a bacteriocine method.6 Strains of Pseudomonas aeruginosa were typed by serological and phage-typing methods at the Central Public Health
Laboratory, Colindale. RESULTS
Samples of the milk feed from all bottles examined and from the dispenser showed 100-400 colonies per ml. of K. aerogenes; smaller numbers of E. coli, Ps. aeruginosa, and other organisms were also isolated from most samples. Gram-negative bacilli were not isolated from tap-water, glucose solution, tinned milk, or the milk mixture in the mixing container. After being passed through the tap of the mixing container the milk feed was contaminated with K. aerogenes. This tap appeared to be the immediate source of the heavy contamination. No growth was obtained on primary culture from clean bottles or rubber caps, but, on subculture from nutrient broth, Ps. aeruginosa was isolated from the rubber caps and from one bottle, and K. aerogenes was isolated from another bottle. No organisms were isolated from the milton solutions. K. aerogenes was isolated from 21,24 and Ps. aruginosa from 11/24 samples of fxces. K. aerogenes isolated from milk and facces showed similar biochemical reactions, antibiotic sensitivity, and bacteriocine patterns. Two serotypes of Ps. aruginosa with similar phage patterns were isolated from both milk and fxces. No strains of enteropathogenic E. coli were isolated from the milk.
560 DISCUSSION
Clinical infection due to Klebsiella spp. or Ps. aeruginosa was not observed during the period of study, but a neonate had died of a Ps. ceruginosa infection 1 year previously in the hospital. At that time Ps. ceruginosa was isolated also from the fxces of many babies examined, but the phage types and serotypes were mainly different from those isolated in the present study. Although the feeds were not examined at the time of the fatal infection, these may have been an important source. A greater possible hazard of contamination would be the replacement of the present flora in the milk by Salmonella spp. or enteropathogenic E. coli. Since the milk kitchen supplies feeds for all the babies in the hospital, an extensive outbreak of infection could occur. It was not surprising that similar organisms were isolated from milk and f2eces; but some of the faeces showed heavy and almost pure growths of K. aerogenes, indicating probable colonisation. No follow-up examination of the fseces of these babies was made. Most of the strains of K. aerogenes were resistant only to ampicillin, and, although resistance to this antibiotic was not transferable to E. coli K.12 in vitro, contaminated feeds might account in some instances for the presence of antibiotic-resistant strains of E. coli in babies’ faeces.77 The immediate source of contamination of the feeds appeared to be a polyethylene tap on the mixing container. Replacement of this tap with a rubber bung and tubing, which could be autoclaved daily, was followed by a considerable reduction of bacterial counts in the feeds. However, the system as a whole was still not entirely satisfactory since occasional strains of K. aerogenes and Pseudomonas spp. were isolated from disinfected bottles and teats both before and after the new routine. Milton is a stabilised 1 % hypochlorite solution and is usually diluted 1 in 80 for use. The low content of available chlorine in in-use " solutions is readily inactivated by small amounts of organic matter. The technique of disinfection with milton should be satisfactory if scrupulous attention is paid to cleanliness.8,9 However, the present study indicates that the process using a hypochlorite solution may occasionally be hazardous, even when cleaning appears to be efficient. Chemical disinfection should be replaced in hospitals by a safer method-e.g., terminal heat sterilisation or disinfection,’aseptically prepared "feeds and disposable bottles,’or ready-to-use sterile feeds .12 All processes should be examined bacteriologically at regular intervals. We thank Dr. M. T. Parker and his colleagues for typing the strains of Ps. aeruginosa, Mr. C. Deverill for technical assistance, and the medical and nursing staff of the Maternity Hospital for "
"
their cooperation. REFERENCES 1. Medical Research Council Report. Mon. Bull. Minist. Hlth, 1953, 12, 214. 2. Robson, A., Anderson, K. Med. J. Aust. 1964, i, 519. 3. Cummings, J. G. J. Pediat. 1949, 34, 711. 4. Wright, J. Br. med. J. 1951, ii, 138. 5. Brown, V. I., Lowbury, E. J. L. J. clin. Path. 1965, 18, 752. 6. Pettit, F. Unpublished. 7. Moorhouse, E. C. Br. med. J. 1969, ii, 405. 8. Farquhar, J. W., Gould, J. C., Schutt, W. H. Lancet, 1965, i, 951. 9. Lincoln, P. A., Breach, G. D., Davis, J. G. Med. Offr, 1965, 114, 169. 10. Hughes, K. E. A., Darmady, E. M., Drewett, S. E. J. clin. Path. 1966, 19, 321. 11. Gamsu, H. R., Cawdery, H. M., Taylor, C. G. Lancet, 1969, ii, 1049. 12. Pugh, R. J. ibid. p. 1190.
PSEUDOMONAS ÆRUGINOSA INFECTION IN A NEONATAL
NURSERY,
POSSIBLY TRANSMITTED BY A BREAST-MILK PUMP A. R. THOM
Department of Pathology, Royal Hospital for Sick Children, Bristol 2
KRISTINA WATRASIEWICZ
A. P. COLE
Departments of Pœdiatrics and Pathology, Southmead
Hospital, Bristol
The introduction of a mechanical breast-milk pump into a neonatal was followed nursery by an outbreak of infection by Pseudomonas œruginosa. Investigation revealed that the pump, despite disinfection with a hypochlorite solution, was contaminated by the infecting strain. A simulated " in-use " test showed that, although the hypochlorite was bactericidal and was being used correctly, it failed to disinfect the apparatus. These findings demonstrate once again the unreliability of chemical disinfection. When chemical methods must be used, their efficacy should be checked by realistic " in-use " tests.
Sum ary
INTRODUCTION
Many hospital infections have resulted from the disinfect re-used apparatus. Ita Some have been attributed to lack of potency of the disinfectant against the infecting organisms, but the failure which we here report occurred although the hypochlorite disinfectant (’ Milton’, Vick International Ltd., London) was demonstrably active against the
failure of chemicals
to
organism. THE OUTBREAK
Since June, 1969, the infants in a neonatal nursery had been routinely screened twice weekly for the presence of salmonellae, shigellea, enteropathogenic Escherchia coli, and Pseudomonas ceruginosa. Rectal swabs were plated on standard bacteriological media, and placed in a selective medium for pseudomonasnutrient broth containing 0-1 mg. per ml. of nitrofurantoin. From 5 out of 25 neonates who were swabbed on July 30, 1969, profuse growths of Ps. aeruginosa were isolated on MacConkey agar and the selective medium. Previous batches of swabs had never contained more than one positive. The infected infants were all full-term and had previously progressed normally. Within a day of the isolation 2 developed vomiting and diarrhoea which lasted for about thirty-six hours. No other cause for the symptoms could be found. The other 3 infants were
symptom-free.
On July 31, rectal swabs were again taken from all infants and in addition from their mothers, but only the same 5 infants were positive. Saline-moistened swabs were taken from thermometer pots, sinks, incubators, balance pans, and parts of an’Egnell’ breast-milk pump (Pump AB, Einar Egnell, Sweden) which had been introduced into the nursery some four weeks previously. Swabs were also taken from the two vessels of hypochlorite solution in which these partsbreast cups, safety bottle, milk bottle, and the plastic