Annals of Burns and Fire Disasters - vol. XIII - n. 3 - September 2000

PREVENTION OF HOSPITAL-ACQUIRED INFECTIONS IN THE PALERMO BURNS CENTRE*

Torregrossa M.V.,¹ Valentino L.,¹ Cucchiara P.,² Masellis M.,² Sucameli M.²

¹ Department of Hygiene and Microbiology, Palermo University, Palermo, Italy
² Department of Plastic Surgery and Burns Therapy, Palermo Civic Hospital, Palermo

Hospital-acquired infections are a considerable problem for health services in all countries, with serious effects on the survival of high-risk patients, such as burn patients. In a burns centre, primary bloodstream infections, pneumonia, and infection of burn sites are very dangerous complications that can compromise the patients survival and the outcome of reconstructive treatment. We stress the importance of emerging pathologies involving opportunistic micro-organisms. In many patients we have detected infections caused by Pseudomonas spp. The isolation of Pseudomonas spp., Bacillus cereus, Achromobacter, Acinetobacter, and Proleus spp. in some patients in the Palermo Burns Centre was the warning signal that prompted an investigation for the presence of opportunistic bacteria in the environment (water, air, supplies) as a "reservoir" of bacteria. Our research team is engaged in identifying the risk factors linked to hospital infection and is carrying out procedures to control infection as well as programmes to guarantee "safe treatment" in the hospital. We also observed staff behaviour during ward activities (e.g., changes in medical and health procedures) and on the basis of these observations we suggested a microbiological surveillance programme for patients, medical and nursing staff, and the environment regarding all the factors that contribute to the circulation of germs around the patient.

Environmental water sampling

The Palermo Burns Centre (Fig. 1) receives municipal chlorinated water and water from private wells. The survey of the level of microbiological environmental pollution was carried out for water supplies, heating-tanks, tap water, tap mixers, bath water, running water, and surface sanitary areas.

When chlorine was < 0.2 mg/1, water samples (tap water, tank water, and bath water) were collected in sterile glass bottle and analysed to assess the concentration of heterotrophic opportunist bacteria. For quantitative analysis, appropriate dilutions and 10, 50, 100, and 200 ml water
samples were filtered through sterile cellulose acetate filters (0.45 nm). The filters were placed on agar nutrient, McConkey agar, and cetrimide agar (agar containing 3% anionic detergent cetyltrimethyl ammonium bromide) and incubated at 22 and 36 °C. The isolated strains were identified using "Standard methods of water and waste water guidelines" (APHA, 1985).

Environment air sampling

Microbial contamination of the air was assessed by determining the air microbe index (AMI). A total number of 396 AMI measurements were performed in the intensive care unit rooms in the patients absence and in the course of routine department activities. Three 10-cm petri dishes containing nutrient agar, blood agar, and Sabouraud's agar were exposed in every room for 1 h at a distance of 1 m from every obstacle (Fischer's 1-1-1 scheme). The dishes were incubated at 36 °C for 48 h and for every room the mean dish values were taken as the colony forming unit (CFU). A further determination of the bacterial charge in the air was made by the RCS-Biotest sampler: in each room 160 1 of air were removed and examined and the results calculated in CFU/cubic m.

Clinical sampling

Monitoring of the patients was performed on hospitalized subjects with deep burns in 10-70% body surface area by means of surface swabs from burned and immediately adjacent areas, biopsies, and haemocultures inoculated into culture media: blood agar, simple and tryptose agar, bromothymol blue lactosate agar, and Pseudomonas agar plates and incubated at 36 °C for 48 h.

Staff sampling

With regard to the health personnel, monitoring was carried out every three months by a culture test of nasal and pharyngeal swabs to test for pathogens and by examination of surgical gloves before and after contact with patients and the patients environment.

Results

Some methicillin-resistant Staphylococcus aureus (MRSA) strains were found in patients in our burns centre: this was the warning signal that prompted a survey of the environment and staff. Three hundred and ninety-six AMI measurements were performed in the intensive care unit rooms; during the study, strains of multi-resistant Staphylococcus aureus were isolated in the nurses' room, the doctors' meeting room, and the laboratory. Many of the strains were MRSA and one of them, which showed the same biochemical characteristics and sensitivity to antibiotics, was isolated from the blood of a young patient with primary blood stream infection (Table I). During the study period the same micro-organisms were found in four staff members by means of nasal and oropharyngeal swabs.

Environmental sampling was performed on water from taps, baths, and the heating tank.
Thirty-five strains of opportunistic bacteria were isolated from skin lesions and blood cultures on burn patients: 24 strains of Pseudomonas aeruginosa, 5 of Acinetobacter spp., 3 of Bacillus cereus, 2 of Achromobacterium spp., and one of Alcaligenes spp. Tap and tank water were always negative for faecal indicators (Table II) but strains of Pseudomonas aeruginosa, Alcaligenes, Pseudomonas stutzeri, and Bacillus cereus (Table III) were isolated from unchlorinated waters. The same strain of Bacillus cereus was isolated from the skin lesions and the blood of two burn patients and in the hot water tank serving the ward.

Pseudomonas aeruginosa strains were isolated in thePseudomonas aeruginosa strains were isolated in the sanitary services of the patients and medical staff rooms, hydrotherapy, and the swilling tank.
Strains of serotype 0:11 Pseudomonas aeruginosa were isolated from patient A. The same strains were found after 24 h in bath water, with water and acqueous quaternary ammonium compound, after the patient's hydrotherapy. Other strains of 0:6 serotype Pseudomonas aeruginosa were isolated from patient B. 0:6-0:11 serotype strains were found in the bath water and later in the blood culture from patient A, after a new bath (Table IV).

The investigation gave rise to a number of considerations. There is certainly a circulation of selected, multiresistant strains capable of causing pathologies in patients who have been undergone invasive manoeuvres and in severely burned patients in whom the damaged skin barrier allows the entry of any micro-organism in circulation.
Most of the cases of sepsis occurring in our burns centre were due to the circulation of strains of MRSA in patients subjected to continuous infusion therapy using intravenous catheters. The observation of sediment germs in the culture dishes of a strain that had good resistance to the air and was always present in different periods of the survey prompted us to perform a mapping in time of the air-person-patient system involved in the re-circulation of the micro-organism, without underestimating the importance of "alerting" germs even in the absence of a high environmental microbic charge.
A large number of gram-negative bacteria and emerging pathogens such as Pseudomonas, Klebsiella, and Enterobacter species may also show the comparative resistance to some disinfectants and antiseptic solutions.
Pseudomonas aeruginosa can cause sepsis, pneumonia, and infection in burned skin. Pseudomonas aeruginosa occupies multiple ecological niches in nature by virtue of its minimal growth requirements and its ability to produce a large number of extracellular protective and toxic substances. Some of these substances, such as slime glycoliprotein, haemolysis, fibrinolysin, lecithinase, elastase, Dnase, and phospholinase, may contribute to the pathogenicity of this opportunistic micro-organism, which is multi-resistant to the most commonly used antiseptics, disinfectants, and antibiotics.
Despite the large amount of information that is available regarding the distribution of Pseudomonas aeruginosa and other micro-organisms in the hospital environment, the routes of infection and transmission remain controversial.
Many investigators have suggested that these opportunistic micro-organisms, especially Pseudomonas aeruginosa, can readily contaminate the hands of personnel, presumably by water splashed from sinks during washing procedures. Other researchers deny this transmission route and believe that a pre-existing colonization of patients leading to endogenous infection is the major source of Pseudomonas aeruginosa.
Our results confirm that water taps in the hospital environment can represent a reservoir of micro-organisms with low nutritional requirements, such as Pseudomonas aeruginosa. This micro-organism can colonize water supply systems, especially when the tap water is particularly rich in calcium and magnesium carbonate, and can spread from this source to the patient environment. Our results showed environmental strains presenting a profile identical to that of clinical strains, suggesting a link between bath water and the patients.
A programme of routine microbiological monitoring effectively minimized the risk in particular patients.
Appropriate nursing techniques are of particular importance for burn patients. There is an increasing awareness of the importance of personal factors in preventing hospital infection and of the need of proper understanding of the facts by all members of the hospital staff. Although the issue is complex and involves many disciplines, the basic ideas are simple, and many of the details of asepsis can be made easier by forms of standardization based on the evidence of effectiveness and practicability.

RESUME. Les Auteurs présentent les résultats d'une enquête approfondie épidémiologique sur le monitorage microbiologique de l'environnement, du personnel, et des patients dans le Service de Réanimation du Centre des Brûlés à Palerme (Italie). Le but de l'enquête était d'évaluer la présence et la distribution des sources environnementales des pathogènes et des agents bactériens opportunistes de l'infection nosocomiale dans les hôtes immunocompromis. Des souches prélevées sur fair, l'eau de robinet et le personnel médical et paramédical ont été comparées à des souches isolées dans les patients brûlés pour étudier les routes possibles de transmission des bactéries. Les résultats de l'enquête ont indiqué la présence de souches environnementales qui possédaient un profil identique à celui des souches cliniques, ce qui suggérait un rapport entre l'environnement, le personnel et les patients. Un programme de monitorage microbien de routine s'est révélé efficace comme système de contrôle pour la réduction de l'infection nosocomiale.

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