C.A. Mackintosh

Design and execution

Summary A study to determine the prevalence of infection among patients in hospital in England and Wales was designed during 1979. The methods to be used were tested in a pilot study. After the hospitals to be involved had been selected and the personnel concerned trained, a survey involving 43 hospitals and 18,186 patients was completed in mid-1980. The methods that were employed are described, and where necessary simplifications or improvements are suggested. The level of comparability in the methods used and the results achieved by the teams from different hospitals is discussed.

An evaluation of surveillance methods for detecting infections in hospital inpatients

Eight selective surveillance methods were compared with a reference method for their ability to detect hospital infections in patients was also assessed. In the reference method, case records were reviewed three times a week, and during the 11-month period of study, 668 infections were identified amongst 3326 patients. Three hundred and thirty-eight were community acquired infections (CAI) and 330 were hospital acquired infections (HAI). The time for data collection was 18.1 h per 100 beds per week. Of the selective surveillance methods, those based on the review of treatment and temperature charts detected the highest proportion (70%) of CAI; and the review of microbiology reports with regular ward liaison identified the highest proportion (71%) of HAI. The time for data collection in the eight methods ranged from 1.2 h per 100 beds per week to 6.5 h per 100 beds per week. After considering the sensitivity for identifying patients with HAI and time for data collection, the review of microbiology reports with regular ward liaison was judged to be an effective and efficient method of surveillance.

A survey of methicillin-resistant Staphylococcus aureus affecting patients in England and Wales

For a six-month period between October 1987 and March 1988, 660 isolates of methicillin-resistant Staphylococcus aureus (MRSA) from 570 patients were sent to the Staphylococcus Reference Laboratory at Colindale to supplement the National reporting survey of MRSA in England and Wales. The isolates were characterized by phage typing, antibiotic susceptibility and by selected biochemical tests. Patient details were also surveyed. Fourteen strains affected more than one hospital and were called multi-hospital epidemic strains. One strain, EMRSA-1, accounted for more than 40% of isolates and of patients. Other epidemic strains were defined. Ten additional strains were restricted to single hospitals. Only 25 primary isolates were non-typable but 67 sporadic typable strains occurred. The patients affected were approximately equally either infected or colonized. The sexes were represented equally. Orthopaedic and geriatric wards were over-represented. Epidemic strains were clumping factor positive while some sporadic strains were weak producers. Urea alkalinization and protein A production could supplement phage typing and antibiotic resistance in strain recognition.

Urinary Tract Infection

Summary Infection of the urinary tract was the most prevalent of the hospital acquired infections recorded in the survey, and the second most prevalent among all that were detected. It was diagnosed in 809 cases, representing 22 per cent of all infections, or 30·3 per cent of cases of hospital acquired and 14·5 per cent of community acquired infections, respectively. Eight point six per cent of patients were found to be catheterized at the time of the survey, and of these, 21·2 per cent were infected. Only 2·9 per cent of the non-catheterized population was infected.

An 11-month incidence study of infections in wards of a district general hospital

Between March 1988 and January 1989, an incidence study of infections in patients occupying 122 beds in a district general hospital was undertaken. Nursing notes, medical notes, temperature charts, drug prescription charts and laboratory information were reviewed three times a week to determine if patients had infection which met strict case definitions. In addition, the surveyor consulted with ward nursing and medical staff for clarification of symptoms and signs indicative of infection. During the study, 668 infections were identified amongst 3326 patients. Three hundred and thirty-eight (51%) were community-acquired infections (CAI) and 330 hospital-acquired infections (HAI). Excluding 24 HAI acquired in other hospitals, the incidence rates were 9.2 HAI per 100 discharges, and 1.1 HAI per 100 patient days. The common types of CAI were pneumonia, abdominal infection and urinary tract infection. The main types of HAI were urinary tract infection, surgical wound infection and pneumonia. The microorganisms most frequently associated with CAI and HAI were Gram-negative bacilli.

Surveillance of methicillin-resistant Staphylococcus aureus in England and Wales, 1986–1990

The incidence of methicillin-resistant Staphylococcus aureus in England and Wales was monitored by a weekly reporting scheme from early 1986 to March 1990. Potential coverage was approximately two-thirds of hospital beds. Reporting centres fell from a peak of 210 in 1986 to a low of 101 centres early in 1989 with later recovery. There were 2367 positive reports in 1986, 2174 in 1987, 1700 in 1988, 1701 in 1989 and 632 in the first quarter of 1990. Colonizations outnumbered infections by 2:1. There were marked regional differences: North-East Thames was dominant in 1986 and 1987, and then declined; South-East Thames showed a dramatic increase in 1988 which continued. Other regions showed less significant changes but there were continuing problems in the South-Western Region and in the West Midlands. Some of these changes were related to the decline of EMRSA-1, possibly due to the introduction of effective control measures, and to the emergence of EMRSA-3 in South-East Thames and its spread to Wessex.

Microbiological aspects of the 1980 national prevalence survey of infections in hospitals

The records of the 1980 national prevalence survey of infection in hospitals were re-assessed from a microbiological point of view. Of 407 records of Escherichia coli, 71 per cent came from the urinary tract while the commonest source of Staphylococcus aureus was from skin infections. These yielded only 41 per cent of the 303 records. Proteus spp. were recorded 166 times, Pseudomonas spp. 115 times and Klebsiella spp. 101 times. These came mainly from the urinary tract but other sources were important. Streptococcus pneumoniae, Haemophilus influenzae, Mycobacterium tuberculosis and the viruses were associated with community infections while E. coli, Proteus spp., Pseudomonas spp., Klebsiella spp., Str. faecalis and non-aureus staphylococci were associated with hospital-acquired infections. The prevalence of bacteraemia was re-assessed.

The general distribution of infection

Summary A study to determine the prevalence of infection among patients in hospital in England and Wales was conducted in mid-1980. Of 18,163 patients studied, 19·1 per cent were infected, about half of the infections being acquired before entry into hospital. Overall, respiratory infection was the most prevalent, though the larger part of this was brought into hospital from the community. Among hospital acquired infections the most common was that of the urinary tract (2·8 per cent of all patients). This was followed in frequency by infection of wounds (1·7 per cent) and the lower respiratory tract (1·5 per cent). Nearly all the infections recorded were of the sporadic or endemic variety. An unknown proportion of these infections is preventable.

A testing time for gowns

There has been ample demonstration that contamination, in the form of skin scales with attendant bacteria, is generated through the physical activity of humans. In regularly cleaned places, such as hospitals, this contamination provides the majority of airborne bacteria. A sensible approach seems to be the use of protective clothing to prevent organisms passing from staff to patient and patient to staff, yet demonstration of the efficacy of such clothing in the prevention of infections has proved difficult. It has been known for some time that conventional cotton gowns do not act as substantial barriers to dispersion of micro-organisms from the body surface (Duguid and Wallace, 1948; Hare and Thomas, 1956). Hambraeus (1973) showed that nurses’ clothing worn under a cotton barrier gown could still become contaminated with bacteria from one patient and these organisms could be dispersed into the rooms of other patients, even though a fresh, sterile gown may have been put on. The ability to resist penetration of moist contamination poses further constraints as it is likely that, under wet conditions, it is the individual bacterial cells that penetrate. More closely woven and waterproof, or at least splashproof, garments would seem to be necessary. This requirement is not always compatible with other factors considered desirable in clothing-comfort, economy, safety, particularly electrostatic safety, and aesthetic appeal. There are many makes and types of protective clothing available and the number is increasing. In addition to conventional ‘balloon’ cottons and Ventiles (tightly woven cottons whose fibres swell when wet, preventing the further passage of water), the American equivalent of which is known as Pima cotton, there are disposable fabrics, all non-woven, in cellulose (e.g. Protek theatre wear, Southalls Ltd., Birmingham), cellulose plus man-made fibres (e.g. Johnson and Johnson’s ‘450’, 60 per cent terylene, 40 per cent cellulose) or completely man-made fibres (e.g. Du Pont’s Tyvek, a high density, spunbonded polythylene). Some non-woven fabrics incorporate a plastic film bonded to them for extra water repellancy. Gowns produced by Molnlycke, for instance, have the plastic film at critical sites, such as the front panel or the lower part of the sleeves. As an extension of this concept Gore-tex make woven fabrics bonded to a complete plastic film, either as a double layer or with the film sandwiched between two layers of woven fabric and have announced their intention of marketing operating room gowns based on these products. They would be re-usable and are intended to be re-autoclavable at least 50 times. How effective are these different gowns likely to be ? How is one to choose between them ? It is possible to obtain complete elimination of dispersion of organisms using PVC fabric (Lidwell, Mackintosh and Towers, 1978), polythene (Bernard et al.,

Respiratory tract infections

Summary Respiratory tract infections were the most prevalent of those found in the survey, being diagnosed in 30·2 per cent of the 3473 infected patients. They were divided into upper respiratory infections (in 4·8 per cent of infected patients, a rate of 0·9 per cent overall) and lower respiratory infections (24·5 and 4·7 per cent). Most of the latter were acquired in the community (16·4 and 3·1 per cent). The distribution of these infections by sex, age and speciality is presented, and the organisms found in association with them are recorded.