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Public Health

ERADICATION OF PSEUDOMONAS

ÆRUGINOSA INFECTION FROM A

SPECIAL-CARE NURSERY

S. E. DREWETT

W. TUKE

D. J. H. PAYNEP. E. VERDON

Portsmouth Control of Infection Team, Portsmouth and Isleof Wight Pathology Service and Public Health Laboratory,St. Mary’s General Hospital, East Wing, Milton Road,

Portsmouth P03 6AQ

Summary 14 eye infections caused by Pseudo-monas œruginosa occurred in neonates in

a nursery over a period of two years. These were tracedto infected resuscitation apparatus. It is suggestedthat every general hospital should have a disinfectionand cleansing service for this and other equipment notrequiring absolute sterility before use. Subatmo-

spheric steam sterilisers give a quick and reliable methodof disinfection.

INTRODUCTION

Pseudomonas aeruginosa has become more commonas a cause of hospital infection, and almost everyaspect of hospital life and equipment has been incri-minated as a source.

Bassett et al. reported neonatal infections associatedwith contaminated resuscitation equipment, and

Phillips and Spencer also found Ps. aruginosa cross-infection caused by contaminated respiratory appara-tus. Their report gave information on the disinfectionof such apparatus. Newell and Tulloch 3 drew atten-tion to humidifiers and suction tubing as possiblereservoirs of infection. 43 infections due to Ps.

ceruginosa in a Glasgow baby-unit were recorded byHenderson et al.4 Of these, 38 were relatively trivial,but in the other 5 the resulting lung lesions werejudged to have contributed to death.

In our hospital pseudomonas has occasionally beenisolated from cases of urinary and respiratory tractinfections, and from pressure sores. It has frequently

been found in urinary-drainage equipment, in sinksand baths, and in suction apparatus.

In 1969 there were 2 severe cases of eye infectionin neonates in a new maternity unit opened in Novem-ber, 1967. These were followed by further cases. Wedescribe the outbreak, the investigations that weremade, and measures taken to eliminate the infection.

THE OUTBREAK

On March 23, 1969, 2 premature babies had eye infec-tions due to Ps. aruginosa. By the next day severe panoph-thalmitis had developed in one of the babies, and the otherbaby had a milder infection which responded to treatmentwith colistin (table i).We suspected that the source of infection was the

incubators, and all eight incubators in use in the unit wereswabbed. Swabs were also taken from the floor, the walls,the humidity vent, and the water in the humidifying tanks.Ps. aruginosa was isolated once from the walls of the incu-bator, and the organism was isolated from the water in thehumidifying tank in four out of eight incubators tested.Bottles of’ Savlon ’ (chlorhexidine and cetrimide) used fordisinfection on the ward were free of pseudomonas.Rubber tubing attached to the suction apparatus was alsonegative.At this time incubators were cleaned with savlon. Tests

indicated that this method was unsatisfactory, and wedecided to clean the incubators with savlon and thendisinfect using chlorhexidine 0.05%, isopropyl-alcohol 4%,and distilled water. This method proved to be satisfactory;after disinfection Ps. aruginosa could not be recoveredfrom an artificially infected incubator.To maintain sterile conditions in the humidifier the

tanks were charged with chlorhexidine solution 1/5000.After this provision had been introduced Ps. ceruginosa wasfound in 4 out of 9 humidifying tanks. Inquiries revealedthat the 1/5000 chlorhexidine was supplied in bulk by thepharmacy in a variety of plastic containers, and 2 out of 8of the containers were contaminated with Ps. ceruginosa.After this discovery the solution was supplied in glass litrebottles which were autoclaved after filling.As we had established an effective disinfection technique

for the incubators and ensured that the humidificationwater was sterile, we hoped that no further action wouldbe needed.

Six months later, however, in September, 1969, one ofthe paediatricians reported that, over a period of someweeks, 5 babies had died of pneumonia, which he suspected

TABLE I-DETAILS OF 14 INFECTED BABIES

Gestation period: full term, 3; less than 35 weeks, 8; between 35 weeks and full term, 3.

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TABLE n—NUMBER OF BABIES ADMITTED TO SPECIAL-CARE NURSERY,AND NUMBER WHO BECAME INFECTED

was caused by Ps. aruginosa. Although there was nobacteriological evidence at necropsy to confirm this view,we thought that the problem of pseudomonas infections inthe special-care nursery must be re-examined.From Sept. 29, 1969, to Jan. 2, 1970, over a period of

twelve weeks, swabs were taken from nose, throat, umbili-cus, and rectum of all infants on admission to the special-care nursery, and at weekly intervals. Of 200 babiesswabbed during this period, 44 gave positive results-acolonisation-rate of 22%. Of these 44 babies, 25 (57%)were thought to have been colonised in the ward, becausepositive cultures were obtained four or more days after anegative culture. Ps. ceruginosa was isolated from theremaining 19 of the 44 infected babies on the first orsecond day after admission, and the source of this infectionwas unknown (table II).At the end of the twelve-week period, the ward disinfec-

tion routine was changed; savlon was replaced by a hypo-chlorite detergent solution which is more effective againstpseudomonas.From Jan. 2, 1970, after the change in disinfection

policy, 110 babies were swabbed and 6 gave positive results,which showed that the infection-rate had dropped to 5°5%.This improvement was not maintained and the infectionbegan to rise again. In March, 1970, there was a severe eyeinfection in a neonate which was followed by a similar in-fection in another baby at the beginning of May.Because of the increase in the number of infants infected,

particularly those with eye infections, a meeting was heldwith the paediatricians and members of the nursing staff todiscuss additional action. There were only 3 nurses in theward to look after and feed 25 infants, and we thought thatlack of nursing staff might have led to a breakdown inward hygiene. At the end of May, 1970, another infanthad a severe infection in both eyes, and it was deemedadvisable to confine all infants harbouring Ps. aruginosa toone room in the nursery.By increasing the nursing staff, and applying the new

measures, we hoped to keep the infection in check. FromMay until December, 1970, 441 babies were routinelyswabbed and 62 (14-1%) had pseudomonas cultures at

some time during their stay in the nursery. 18 (4-1 % ) of these62 were found to be positive on admission to the nurserywithin twenty-four hours of birth. Results of rectal andvaginal swabs from the mothers matched those of the babyin only 1 case; this baby had become colonised withPs. ceruginosa in the rectum after a seven-day stay in thenursery. The baby was breast-fed and both mother andbaby were infected with Ps. ceruginosa, pyocine type 1,subtype C.Between July and November, 1970, 6 babies had eyes

infected with Ps. ceruginosa; 2 had infections in both eyes.The infections were not severe and responded immediatelyto local treatment with colistin.From the beginning of January to the end of April, 1971,

281 babies were swabbed. 33 (11-7%) were positive atsome time during their stay, and of these 16 (5-7%) were

found to be colonised shortly after birth; all 16 babies hadbeen resuscitated. 3 more babies had infected eyes fromwhich Ps. ceruginosa was recovered and all required inten-sive treatment.

Because 16 babies had positive swabs from the nose and/or throat, some within twenty minutes of birth, the figuresfor the previous year were examined, and we decided tocarry out a detailed investigation into the source of theinfections. The infection was often acquired beforeadmission to the nursery, and techniques and equipmentused at the time of delivery of the infants were examined.Two years before, in May and July, 1969, the swan-neckoxygen tubes and face masks of the resuscitation apparatusand the laryngoscopes had been examined; all gave negativeresults. This time all apparatus and equipment used forresuscitation was examined in detail. There are 12 deliveryrooms, all in regular use, and tables III and iv show therange of equipment examined, the number contaminated,and the pyocine type. Before the investigation was com-plete, it was already apparent that the suction apparatuswas heavily infected and immediate action had to be taken.Instructions were given that: (1) suction tubing was to beremoved after use, cleaned, and then disinfected by sub-atmospheric steam before being used for the next baby;(2) a fresh piece of disinfected tubing was to be attachedonly immediately before use; and (3) the catheter pack wasto be opened and the suction catheter attached immediatelybefore use.

Unfortunately there were insufficient suction bottles toallow them to be included in the cleaning/disinfectionservice, but results suggested that this might not benecessary.The hospital has a 16 x 30 in. subatmospheric steam

disinfector/steriliser which could be used for the tubing.An orderly collects the suction tubing from all areas withinthe maternity unit, washes it, and packs it in ’Bripac’boxes, and takes it for disinfection. During the disinfectioncycle the tubing is subjected to steam at 80 °C for sixminutes, and four years’ experience with this apparatus hasshown that, provided cleaning is satisfactory, vegetativeorganisms are always killed within this time-at-temperature.On return to the maternity unit the tubing remains in thebripac boxes until required.

BACTERIOLOGICAL STUDY

Swabs were taken from the nose, throat, umbilicus,and rectum of each child. The nursery is a short distancefrom the laboratory, and there was no delay in inoculatingthe swabs on to the improved cetrimide agar.s Plates wereincubated at 37 °C and examined after twenty-four andforty-eight hours. Any colonies which appeared on thecetrimide plates were examined by fluorescence, usingultraviolet in the dark, and Kovacs’ oxide-test usingtetramethyl-p-phenylenediamine solution.7 We have foundthat growth on cetrimide agar of any organisms, other thanPs. aruginosa or an occasional klebsiella strain, is very rare.Swabs taken from baths and places where residual

chlorhexidine might be present were first placed in nutrientbroth with lecithin-lubrol.28 Where residual hexachlora-phane might be present the nutrient broth contained 0-5%’ Tween ’ 80.8 In each case the broth was incubated over-night at 37 °C and then subcultured on cetrimide agar.Colonies of organisms isolated were examined as alreadydescribed. Where a very mixed bacterial flora was expected,the use of nutrient broth with 0-03% cetrimide enabledalmost pure cultures of Ps. aeruginosa to be grown.

Pyocine typing was carried out on all fresh isolates from1970 onwards using the method of Gillies and Govan.8

Serological and phage typing was done by Dr. M. T.Parker at the Cross-Infection Reference Laboratory,Colindale.

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Results are shown in table I. Pyocine type 22,serotype 6, was the most common strain isolated onor after Oct. 28, 1970, when 5 out of 7 babies wereinfected with this strain. Table ill shows the degreeof contamination of the equipment in the ward deliverysuites, and table IV shows that pyocine type 22 was

TABLE III-TYPE OF APPARATUS EXAMINED AND NUMBER CON-

TAMINATED WITH PS. aeRUGINOSA

TABLE IV-PYOCINE TYPING ON STRAINS OF PS. aeRUGINOSA

ISOLATED FROM RESUSCITATION APPARATUS

0 =not isolated. + =Ps. rugfnosa isolated but not typed.Number (e.g., 22) = pyocine type of strain isolated.

present more frequently than any other strain of

pseudomonas. Not only was pyocine type 22 thepredominant organism, but it was present in 10 out of12 delivery suites in 6 hospital wards. These wardsare on 3 floors, 2 delivery suites to a ward, yet pyocinetype 22 was endemic throughout the hospital. Therewas close correlation between the pyocine, serological,and phage typing, as 44 strains of pyocine type 22 wereserological type 6 and were lysed by phages 7/M4/Col.11.

DISCUSSION

Ps. aeruginosa infection of the eyes can be so severethat, unless it is treated with an effective antibioticwithin twelve hours of onset, there is a high risk thatthe sight will be lost. In adults, and in neonateswith intact conjunctiva, the infection may only causea conjunctivitis lasting a few days; if trauma hasoccurred it may allow the infection to establish itself.Trauma may not necessarily be gross; a breach of thecontinuity of the cell layers may be the setiologicalfactor producing severe panophthahnitis. A babyfrequently rubs its eyes with its hands and this maydamage the conjunctiva.

The virulence of the organism and the susceptibilityof the infant before the development of an adequateimmunological response may explain variations in theseverity of infection.Many factors delayed the detection of the true

source of the infection. These were the infected waterin the humidifiers, inadequate disinfection of theincubators, a disinfection policy which was ineffectiveagainst Ps. aeruginosa, an insufficiency of nurses whichmight lead to short-cuts in nursing techniques, and theubiquity of the organism. When the infection persistedit became apparent that some infants were already in-fected on admission. The resuscitation apparatus wasre-examined when it was discovered that these infantshad all been resuscitated.Not every piece of apparatus in use in hospitals

needs to be sterilised after use; cleaning and disinfec-tion between use by patients is all that is required.Such a service was outside the scope of the centralsterile supply department, which is in another hospitaland already supplies 60 hospitals. Each district generalhospital could provide a disinfection service if it had asubatmospheric steam-steriliser.

We thank Dr. O. A. Okubadejo for his work on the cleansingand disinfection of the incubators; Dr. M. T. Parker for hisadvice and encouragement; Dr. G. M. Lewis and Dr. J. H.Moseley, paediatricians, and Mrs. J. Taylor and the nursing stafffor their patience and cooperation.

Requests for reprints should be addressed to D. J. H. P.

REFERENCES

1. Bassett, D. C. J., Thompson, S. A. S., Page, B. Lancet, 1965, i, 781.2. Phillips, I., Spencer, G. ibid. 1965, ii, 1325.3. Newell, R. E., Tulloch, W. E. Br. med. J. 1967, iv, 548.4. Henderson, A., Maclaurin, J., Scott, J. M. Lancet, 1969, ii, 316.5. Brown, V. I., Lowbury, E. J. L. J. clin. Path. 1965, 18, 752.6. Lowbury, E. J. L., Lilly, H. A., Wilkins, M. ibid. 1962, 15, 329.7. Cowan, S. T., Steel, K. J. Manual for the Identification of Medical

Bacteria; p. 148. London, 1965.8. Rubbo, S. D., Gardner, J. F. A Review of Sterilization and Dis-

infection; p. 130. London, 1956.9. Gillies, R. R., Govan, J. R. W. J. Path. Bact. 1966, 91, 339.

MEDICAL ASPECTS OF LARGEOUTDOOR FESTIVALS

JUSTIN SCHLICHTMaudsley Hospital, London S.E.5

MARTIN MITCHESONUniversity College Hospital Drug Dependence Clinic,

London N.W.1

MEL HENRYGeneral Practitioner, London S.W.14

Summary Four festivals of pop music have beendescribed, and some problems of

special interest and importance were emphasised. The" bad trip" after lysergide usage is one medicalproblem at such festivals, and it is one with whichBritish doctors have relatively little experience. Thevalue of volunteers and their organisations cannot beemphasised too much, and their presence should alwaysbe an integral part of such occasions. The case-loadexperienced at these festivals makes it clear that suchgatherings need general medical cover, and there shouldbe additional facilities to deal with injuries due toviolence or camping accidents.