Anna Hambraeus

Bacterial contamination in a modern operating suite. 3. Importance of floor contamination as a source of airborne bacteria.

The redispersal factor for bacteria-carrying particles from a contaminated floor was determined after mopping, blowing and walking activity. Walking gave the highest redispersal factor, 3.5 X 10(-3) m-1, which was three times higher than for blowing and 17 times higher than for mopping. The mean die-away rate for the bacteria-carrying particles used was 1.9/h without ventilation and 14.3/h with ventilation. It was calculated that in the operating rooms less than 15% of the bacteria found in the air were redispersed floor bacteria.

Nasal and hand carriage of Staphylococcus aureus in staff at a Department for Thoracic and Cardiovascular Surgery: endogenous or exogenous source?

OBJECTIVE To investigate the rates of Staphylococcus aureus carriage on the hands and in the noses of healthcare workers (HCWs) and the relatedness of S. aureus isolates found in the two sites. DESIGN Point-prevalence study. SETTING Department for Thoracic and Cardiovascular Surgery at the University Hospital of Uppsala, Uppsala, Sweden. SUBJECTS AND METHODS Samples were obtained from 133 individuals, 18 men and 115 women, using imprints of each hand on blood agar and a swab from the nose. S. aureus isolates were identified by standard methods and typed by pulsed-field gel electrophoresis. RESULTS S. aureus was found on the hands of 16.7% of the men and 9.6% of the women, and in the noses of 33.3% of the men and 17.4% of the women. The risk ratio for S. aureus carriage on the hands with nasal carriage was 7.4 (95% confidence interval, 2.7 to 20.2; P < .001). Among the 14 HCWs carrying S. aureus on their hands, strain likeness to the nasal isolate was documented for 7 (50%). CONCLUSIONS Half of the HCWs acquired S. aureus on the hands from patients or the environment and half did so by apparent self-inoculation from the nose. Regardless of the source of contamination, good compliance with hand hygiene is needed from all HCWs to protect patients from nosocomial infections. The moderate rate of S. aureus carriage on hands in this setting could be the result of the routine use of alcoholic hand antisepsis.

Methicillin-resistant Staphylococcus aureus in two burn units: Clinical significance and epidemiological control

Routine isolation adequately controlled MRSA strains in two burns units with a restrictive antibiotic policy. Ventilation control and more rigorous change of clothing offered no further advantage. No carriers among staff were found, but some suffered minor skin lesions that were the source of further MRSA spread. Spread of MRSA from the unit to other parts of the hospital was prevented by early identification of colonized patients and by restricting patient and staff movement.

An investigation of occlusive polyester surgical clothing

The bacterial dispersion rate of people wearing operating room clothing made from several types of polyester fabric was compared to conventional cotton clothing, total-body exhaust gowns and disposable clothing. Airborne bacteria were measured in a chamber, three ultra-clean air operating rooms and a conventionally ventilated operating room. The polyester clothing was demonstrated to be much superior to conventional cotton clothing and at least as good as the total-body exhaust gowns and disposable clothing.

The influence of the total body exhaust suit on air and wound contamination in elective hipoperations

An evaluation of the effect of total body exhaust clothing on air and wound contamination was made in an operating theatre with a zonal ventilation system. Sixty-four patients who underwent total hip replacement using the Charnley-Müller prosthesis were studied. The members of the surgical team wore total body exhaust suits (TBE-suit), or conventional theatre clothing (C-clothing) at alternate operations. Nearly half of the patients in each group were given prophylactic antibiotics. Both the mean and median values of airborne bacteria in the operating theatre were significantly lower during operations with TBE-suits than with conventional theatre clothing. The lowest number, 4.0 cfu/m3, was found at the site of the operation wound. Cultures from adhesive drapes showed growth in 46 per cent of the C-group and in 43 per cent of the TBE-group samples. Wound washouts showed growth in 43 per cent of the C-group and in 10 per cent of the TBE-group samples. Staphylococcus epidermidis was the most frequently isolated bacteria both from adhesive drapes and from wound washouts. The rate of superficial infections was slightly higher when C-clothing was used. Deep infections were found in one patient in the TBE-group and in two patients in the C-group. None of the infected patients had received prophylactic antibiotics.

Dispersal and transfer of Staphylococcus aureus in an isolation ward for burned patients

The dispersal of Staphylococcus aureus from burned patients, the relation between nasal carriage by the staff and exposure to airborne Staph. aureus, and the transfer of Staph. aureus-carrying particles within the ward have been studied. The dispersal of Staph. aureus from burned patients was correlated to the size of the burn wound. The median values varied from 21 c.f.u./m.(2)/hr. for patients with small burns to 453 c.f.u./m.(2)/hr. for extensively burned patients. The size of the dispersed particles appeared to be smaller than that usually found in hospital wards. Carriage of nasal strains by the staff was correlated to the air counts; the number of patient sources did not seem to be of great importance. The transfer of Staph. aureus within the ward was at least 6 to 20 times that which would have been expected if transfer was due to air movement only.

Protection of the patient in the operating suite

Hospital infection is still an important problem and numerous investigations have been published in this field. According to the National Research Council of Canada about 2450 papers had been published on hospital infection caused by Staphylococcus aureus or other bacteria up to 1962. As many have probably been published since then, and many of them deal with postoperative wound infection. The frequency of postoperative wound infection differs from time to time, but in several large and well controlled studies during the last 15 years infection rates between 7 and 9 per cent have been reported (Ad Hoc Committee, National Research Council, 1964; Altemeier, 1971; Brote, 1976; Bengtsson, Hambraeus & Laurell, 1979). Attempts have been made to correlate the frequency of infection with improvement of the physical environment in operating suites or with new working routines. Many researchers have placed particular importance on the prevention of airborne transmission (Hart, 1936; Wells & Wells, 1936; Bourdillon & Colebrook, 1946; Blowers, Mason, Wallace W Charnley, 1964, 1972; Charnley & Eftekhar, 1969). The importance of the general layout of an operating suite in the maintainance of high hygienic standards has interested architects, surgeons and microbiologists, but few systematic studies have been done in this field. In Sweden the design of many new operating suites has been greatly influenced by the recommendations of the Operating Theatre Hygiene Subcommittee of the Medical Research Council in England (1962). According to their recommendations an operating suite can be divided into four different zones: (a) protective zone including entrance lobby, recovery rooms and changing rooms; (b) clean zone including anaesthetic rooms, scrub-up rooms and inner lobby; (c) sterile zone including operating rooms, sterilizing rooms and lay-up rooms; (d) disposal zo12e including sink rooms. The influence of these recommendations on the layout of a modern operating suite in Sweden will be discussed as will the significance of different hygienic routines used in this suite and those reported by other workers.

Studies on transmission of Staphylococcus aureus in an isolation ward for burned patients.

A one-year epidemiological investigation was made in an isolation ward for burned patients. The transmission of Staphylococcus aureus was mainly studied. In spite of the design of the ward the cross-infection rate was high. In all, 49 of 69 patients were infected 114 times. Twenty-six of the strains causing infection were found in a patient only, 10 in a member of the staff only and 23 in both patients and staff the week before they caused a new infection. There were three epidemic outbreaks caused by three strains of Staph. aureus all belonging to phage group III; one was resistant to methicillin. Environmental studies with settle plates showed that the number of staphylococci dispersed by a burned patient was often very high. In 8% of the observations in occupied bedrooms the air count of Staph. aureus was more than 1800 col./m.(2) hr. However, the counts of Staph. aureus in the corridor and service areas were low. This seems to indicate a rather good protection against airborne transfer of bacteria. Other routes of infection were probably of greater importance.

The control by ventilation of airborne bacterial transfer between hospital patients, and its assessment by means of a particle tracer: III. Studies with an airborne-particle tracer in an isolation ward for burned patients

Airborne-particle transfer has been studied in a burns unit using potassium iodide particles. The observed rates of transfer were in good agreement with the values predicted by a theoretical model.An estimate of the average transfer between rooms under conditions of normal activity and with correctly functioning ventilation showed that the isolation system was highly efficient, the proportion transferred being probably less than 1 in 10(5). However, the ventilation often did not function as designed and under these conditions the efficiency was reduced by a maximum of a factor of ten. These rates of transfer do not seem great enough to account for the high rate of cross-infection found in this unit.

Dispersal of non-sporeforming anaerobic bacteria from the skin

Dispersal of non-sporeforming anaerobic bacteria was studied. Skin samples were taken from the subjects, and dispersed from different parts of the body was examined. The number of anaerobic bacteria dispersed was not correlated to their density on the surface of skin area exposed. The highest density of anaerobic bacteria on the skin was found in the face and upper trunk, but the highest yield of anaerobic bacteria dispersed came from the lower trunk. The dominant anaerobic bacteria dispersed were Propionibacterium acnes, but Propionibacterium avidum, Propionibacterium granulosum and Gram-positive cocci were also isolated from the dispersal samples. Peptococcus magnus was the most common coccus isolated. For the less frequently isolated bacteria, the best correlation was found between the perineal flora and airborne bacteria. A comparison was also made of bacterial dispersal by naked and dressed subjects. The dispersal of both aerobic and anaerobic bacteria was higher when the subjects were dressed in conventional operating theatre cotton clothing than when they were naked. The increased dispersal of anaerobic bacteria when the subjects were dressed was mainly due to increased dispersal of Propionibacterium sp.