E. J. L. Lowbury

Comparison of two methods for assessing the removal of total organisms and pathogens from the skin.

A standard hand-wash sampling technique was compared with a simple finger-streak sampling method in assessing the relative effectiveness of a number of alternative preparations used for disinfecting the surgeons hands (alcoholic 0.5% chlorhexidine, alcoholic 0.1% tetrabrom-o-methyl phenol, a 4% chlorhexidine detergent solution, aqueous 0.5% chlorhexidine, 2% Irgasan detergent solution and, as control, bar soap). There was a fairly good correlation between the results of assessment by the two methods after a single disinfection and after six disinfections, three on one day and three on the next. Significant differences were shown in 21 comparisons between treatments when the hand-wash sampling test was used, and 16 of these comparisons also showed a significant difference by the finger-streak test. Staphylococcus aureus was found in hand samplings from 5 out of 8 nurses in the Burns Unit of Birmingham Accident Hospital by the hand-wash sampling method and from 2 of the same 8 nurses by the finger-streak method; the numbers were small, and no Staph. aureus were isolated from the same hands after 1 min. wash in 70% ethyl alcohol. Similar sampling on 29 nurses in other wards showed Staph. aureus on 3 nurses (one in large numbers) by the hand-wash technique and on 1 nurse by the finger-streak test; in only 1 nurse whose hands showed Staph. aureus before disinfection was the organism found, by hand-wash sampling, after disinfection. Parallel sampling of nurses hands after washing with soap and water and after disinfection with 95% ethanol showed larger numbers of Staph. aureus in a hospital for skin diseases than in a general hospital, and a lower incidence and somewhat lower density of Staph. aureus after ethanol treatment than after washing with soap and water; Gram-negative bacilli, on the other hand, were commoner on hands in the general than in the skin hospital, and present in much smaller numbers after disinfection with ethanol than after washing with soap and water. Antibiotic sensitivity tests showed the frequent recurrence on the hands of some nurses of multi-resistant Staph. aureus with resistance patterns similar to those found in infective lesions in some of the patients; different sensitivity patterns were usually found in staphylococci isolated from the nose. Even in wards where many patients were infected, carriage by nurses hands of a particular strain of Staph. aureus did not seem to last for more than a few days.

The epidemiology of infection with Pseudomonas pyocyanea in a burns unit

A bacteriological study of burned patients and of the staff and environment in a burns unit was made with the purpose of discovering the principal reservoirs and routes of transfer of Ps. pyocyanea . Infected burns appeared to be the most important reservoirs. About 3 % of the stools of normal subjects and of patients with intestinal symptoms carried the organism, which was also isolated from the nose, throat, nasopharynx, skin and ear of a small proportion of patients and staff in the burns wards. The hands of nurses in the wards were often contaminated with Ps. pyocyanea , and presented a likely vector in the transfer of the organism by contact—e.g. from the bandages of infected patients, and from furniture and other objects near to their beds. It was shown by slide agglutination that a new type of Ps. pyocyanea admitted to one of the wards spread freely in that ward but hardly at all to the other ward. Since patients from both wards used the same dressing station and operating theatres, it seemed from this finding that a large proportion of the cross-infection occurred in the wards. Polymyxin dusting powder was shown in a controlled trial to protect exposed burns against contamination by Ps. pyocyanea . These results are discussed in relation to the mechanism of transfer of the organism and the methods of preventing cross-infection. The need to use several methods concurrently is emphasized, since none of those which have been investigated contributes more than a partial effect. Cubicle wards are advocated, since much cross-infection is shown to occur in open wards. We are much indebted to Dr G. T. Cook for kindly letting us use results obtained by him at the Oxford Public Health Laboratory. We also wish to thank Prof. J. F. D. Shrewsbury of Birmingham University and our colleagues at the Birmingham Accident Hospital for their valuable co-operation, and Dr A. C. Cunliffe of Kings College Hospital for information on the typing of Proteus from patients in our wards.

Neomycin-resistant Staphylococcus aureus in a burns unit

Early in 1963 neomycin-resistant Staph. aureus appeared in the burns of patients in a burns unit; after a period of 7 weeks three-quarters of the strains of Staph. aureus isolated from patients in the unit were resistant to neomycin, and after 22 weeks almost half of the patients in the burns wards were carrying the organism on their burns. When treatment with neomycin and kanamycin was stopped in the Burns Unit, neomycin-resistant strains gradually diminished in numbers and were no longer found in the ward after 6 months. The neomycin-resistant staphylococci appeared during controlled trials of local neomycin and systemic kanamycin, and were much more frequently isolated from the burns of patients treated with these antibiotics than from patients in the control series. During the previous 9 years local neomycin application had been used on many patients; though all staphylococci were tested for sensitivity to neomycin for a considerable part of this time, no resistant staphylococci were found. All the neomycin-resistant staphylococci showed a pattern of inhibition by phages 6, 47, 54 and 77, and many also by phages 7, 53, 75 and 75B at 1000 R.T.D. No neomycin-sensitive staphylococci with this phage pattern were found at the time when resistant strains first appeared (though two such strains were found later); it seemed likely, therefore, that the resistant strain was introduced from outside the hospital. Preliminary tests of habituation to neomycin of sensitive strains with the phage inhibition pattern are described. Back mutation to sensitivity was not found in tests on neomycin-resistant staphylococci.

The sources of hospital infection of wounds with Clostridium welchii.

Although gas gangrene is a rare disease in peace time, the organisms responsible for the condition are widely distributed, Clostridtum welchfi in particular being found commonly in soil, faeces, dust, air, milk and various foods (Weinberg, Nativelle & Prevot, 1937; Colebrook & Cawston, 1948; Smith, 1955); C7l. wetchii often colonizes open wounds without causing gas gangrene (McLennan, 1943; Williams & Miles, 1945). This variety of habitat is of particular importance in relation to the much dreaded post-operative incidence of gas gangrene (e.g. Meleney, 1948; Sevitt, 1953). In the study reported here we have used a selective medium (Lowbury & Lilly, 1955) to obtain some quantitative data on the presence of 01. welchii in the air of operating theatres, of an air-conditioned dressing station and of other parts of the hospital. We have also examined the distribution of the organism in burns and other wounds, and obtained some evidence from these and other studies on the relative importance of self-infection and of infection from the environment.

Transfer areas and clean zones in operating suites.

It is generally assumed that floors in the aseptic zone of operating suites should be protected against contamination with bacteria brought in from other parts of the hospital. The use of plastic overshoes and theatre boots are convenient measures against contamination from the soles of shoes, but it is harder to devise practical methods of preventing contamination from the wheels and other surfaces of trolleys. The use of tacky mats or disinfectant dips for this purpose is of rather doubtful value (Ayliffe et al. 1967; Medical Research Council, 1968). A design of operating suites has been recommended in which the aseptic (sterile) zone, including the operating and sterilizing rooms, is approached through a clean zone, where theatre clothes are worn; the clean zone is approached through a protective zone, where the staff changes into theatre clothes, footwear, etc. (Medical Research Council, 1962). Between the protective and clean zones in some operating suites a transfer area is provided, where patients are transferred from the hospital trolleys, on which they are brought from the wards, to clean theatre trolleys; this arrangement is thought to have some value in protecting the aseptic zone against contamination from trolleys (Weeks, 1964; Barron, 1964). The presence of such an area with clean trolleys requires a considerable addition to the floor space allocated for the operating suite; transfer to fresh trolleys involves additional handling of sick patients, and also some congestion and delay in conveying patients to the operating room. The inclusion of transfer areas in plans of new hospitals can be justified only if it is shown to reduce the hazards of infection by reducing the levels of bacterial contamination in the aseptic zone. In the study reported here we attempted to answer three questions: (1) does the presence of a transfer area reduce the amount of contamination introduced into the clean and aseptic zones of operating suites ? (2) are the clean and aseptic zones of operating suites provided with transfer areas cleaner than those without transfer areas? (3) is the presence of a clean zone associated with less contamination in the aseptic zone than that which is found in theatre suites with no clean zone? The role of the environment as a source of infection with Glostridium welchii is also discussed.

THE EGG YOLK REACTION OF STAPHYLOCOCCUS AUREUS ISOLATED FROM BURNS.

A large majority of strains of Staphylococcu,s aureus were found by Gillespie dZ; Alder (1952) to produce opacity when grown in egg yolk broth, apparently through the action of a lipase on certain triglycerides. Of the strains isolated from outpatients, 82 °/O were egg yolk positive (EY+), but only 45 °/O of those isolated from in-patients gave a positive reaction; there was a strong association between penicillin-resistance and a negative egg yolk (EY-) reaction. Parker (1958) confirmed the association of negative egg yolk reaction with penicillin resistance, and found that such strains were particularly common in superficial lesions, including wounds; strains which caused deep lesions usually showed a positive egg yolk reaction. We have tested strains of Staph. avreus isolated from burns in three periods (195S, 1960 and 1962) and from several other sources for egg yolk reaction; the association of this reaction with some other features, including phage type, antibiotic sensitiivity and mercuric chloride resistance (Moore, 1960) has been examined. The relevance of these data to the epidemiology of staphylococcal infection is discussed.

The growth and death of wound bacteria in serum, exudate and slough.

When pathogenic bacteria have been implanted in the tissues for e2cample, by a penetrating wound at an autopsy or some other accident it can hardly be a matter of indifference to the host whether these organisms are able to multiply rapidly in the extracellular fluid at the site of injury or in his circulating plasma. The subject, however, receives little attention in text-books of pathology or surgery. During the First World War, Wright, Fleming & Colebrook (1918) reported experiments which suggested that bacteria from wounds could be classified in two groups, those which grow freely from small inocula in fresh human serum and those which will not grow in this environment. The former, which they called serophytes , included certain strains of streptococci (in all probability Streptococcus pyoyenes) and Staphylococcus aureus; the latter, described as sero-saprophytes, included strains of coliform bacilli. Both groups of bacteria were found to grow well in fresh serurn after it had been treated with trypsin; that is, in conditions not very different from those in the exudate of an infected wound in which proteolytic enzymes were being set free from leucocytes. To explain these phenomena Wright and his colleagues suggested that sero-saprophytic organisms required for their growth some of the breakdown products derived from proteolytic digestion of serum protein when enough trypsin was added to overcome its normal antitryptia power. An alternative hypothesis to account for the difference between serophytes and sero-saprophytes is that the latter fail to grow in fresh serum because they are killed by bactericidal substances, and in particular by the properdin system which is known to be active against many coliform bacilli but inactive against streptococci and staphylococci (Pillemer, Blum, Lepow, Ross, Todd & Wardlaw, 1954; Wardlaw & Pillemer, 1956). On this hypothesis tryptic digestion might, by the destruction of such bactericidal components, convert fresh serum into a suitable culture medium for the organisms which are killed by them. To throw light on this problem we have repeated some of the experiments of Wright et al. (1918) using more conventional techniques, and examined the effect of tryptic digestion of serum on its ability to kill or to support the growth of certain

A source isolator for infected patients.

A plastic, mechanically ventilated source isolator with filters in the air effluent was designed to enable infected patients to be nursed and treated in a general ward or to be transported without risk to staff or other contacts. Two models of isolator were developed. Their potential value was tested by the challenge of heavy dispersal, inside the isolator, of bacteria (a) from patients with burns, during the change of dressings, (b) from contaminated bedding during simulated bed-making, and (c) from the dispersal of a suspension of Bacillus subtilis var. globigii. Sampling of air by slit samplers outside the isolator and, in comparable control patients, from the air of the room in which dressings were changed, showed consistently lower counts of bacteria and of Staph. aureus during dressings when the isolator was used; on removal of the isolator canopy there was, in some experiments, a considerable increase in airborne bacteria, due to residual bacteria in the isolator of to the re-dispersal of bacteria which settled on the patient and his bedding during the dressing. Simultaneous sampling with slit samplers inside and outside the isolator during and after bed-making or dispersal of B. subtilis var. globigii showed an almost complete protection of the air outside the isolator against contamination by bacteria released inside the isolator.

CLEANING OF HOSPITAL FLOORS WITH OILED MOPS.

A comparison was made of three methods for the removal of dust from a hospital ward floor. The viable bacterial counts of impression plates from the floor showed a mean reduction of 51 % after cleaning with fresh oiled mops, 40 % after cleaning with a tank model vacuum cleaner and 5 % after sweeping with a broom. The mean proportions of airborne bacteria, compared with viable counts before cleaning, were 192 % during and 194 % after cleaning with a broom; 128 % during and 103 % after cleaning with an oiled mop, and 82 % during and 48 % after cleaning with a vacuum cleaner. On repeated use the oiled mop dispersed almost as much dust as a broom, but this settled rapidly from the air. The effects of these cleaning methods on counts of presumptive Staph. aureus on the floor and in the air were similar to those found in counts of total organisms. We wish to thank Mr M. D. Wilkins for valuable assistance, the Domestic Superintendent and staff and the nursing staff for their co-operation, and Messrs Leeming Brothers Limited for supplies of ‘Kex’ mops and equipment.