Gunnar Laurell

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.

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.

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.

Airborne contamination and postoperative infection after total hip replacement

The results of 163 hip replacements at the Uppsala University Hospital are presented. Deep infection occurred in ten cases and was caused by Staphylococcus aureus in four early or intermediate infections and by anaerobes in four late infections. The remaining two infections (both of which were late) were probably associated with Staphylococcus albus--in one case possibly also with alpha streptococci. Two superficial infections not affecting the operative result were caused by Staphylococcus aureus and betahaemolytic streptococci. The results of environmental analyses of staphylococci and the total number of bacteria in the air during 77 operations did not indicate that airborne infection is a major cause of postoperative infections--there was no difference between the number of bacteria found in the air during operations after which infection occurred and uninfected operations, and the use of special zonal ventilation with high rates of air exchange in the operating area had no effect on the infection frequency.

Bacterial contamination in a modern operating suite. 1. Effect of ventilation on airborne bacteria and transfer of airborne particles.

The effect of ventilation on airborne contamination was studied in a new operating suite containing operating rooms with conventional ventilation (17-20 turnovers/h) and operating rooms with zonal ventilation, where the turnover in the central part of the room was approximately 80/h. The efficacy of the ventilation was first examined with gas tracer experiments and found satisfactory. Experiments using potassium iodide particles showed the transfer between adjacent rooms in the suite to be less than 10(-3)% with closed doors and from 1% to 2.5 x 10(-2)% when the doors were opened once a minute. The transfer between two adjacent operating rooms was calculated to be approximately 10(-4)%. There is thus little risk of spread of airborne infection between operating rooms.Experiments with potassium iodide particles showed that in operating rooms with zonal ventilation the particle concentration in the centre of the room was about one-tenth that in the periphery; in conventionally ventilated operating rooms the concentration was about one-half. With bacteria-carrying particles generated by human activity the concentration in the centre of operating rooms with zonal ventilation was about half that in the periphery both during experimental activity and operations; in conventionally ventilated operating rooms it was about equal in both cases. Bacterial counts at the periphery were found to be lower in rooms with zonal ventilation ( approximately 50 c.f.u./m(3)) than in conventionally ventilated ( approximately 70 c.f.u./m(3)).

Identification of Cephalosporin-Resistant Staphylococcus aureus with the Disc Diffusion Method

Methicillin-resistant strains of Staphylococcus aureus, in total 84, representing 16 laboratories in 8 different countries were all resistant to 32 μg of cephalothin per ml with the same typical heteroresistant pattern. With the disc diffusion method, they were easily detected when cephalexin discs were used. With cephalothin discs, on the other hand, 26 to 49% would have been falsely categorized as Group I or II after 24 hr. It is recommended that susceptibility testing of S. aureus to cephalosporins by using the paper disc method be performed with 30-μg cephalexin discs on Mueller-Hinton agar without blood. With an inoculum of 106 bacteria/ml, an incubation temperature of 30 C, and an incubation time of 24 hr, a zone of less than 10 mm indicates presumptive heteroresistance. This corresponds to the international recommendation with a minimal inhibitory concentration of 32 μg/ml as the upper limit of Group II.

Bacterial contamination in a modern operating suite. 4. Bacterial contamination of clothes worn in the suite.

Clean clothes in the staff dressing rooms were heavily contaminated with bacteria, mainly Bacillus sp., but Staphylococcus aureus were found on 14% and Clostridium sp. on 10% of the garments examined. A comparison of the occurrence of Staph. aureus on shirts worn by staff in wards and operating departments showed ward shirts to be contaminated more heavily and with more strains. Examination of sterile gowns worn by surgeons showed that 70% were contaminated with Staph. aureus after operation. Of the strains isolated 31% were identical with those carried by the surgeon or by the patient operated on, but for the remainder no source could be found.

Identification of Enteropathogenic Escherichia Coli 0111: B4 by Means of Fluorescent Antibodies

The fluorescent antibody technique has been tested during a current epidemic of infantile diarrhoea due to E. coli 0111:B4, and has been compared with the conventional bacteriological and serological techniques. Four different modifications have been compared. After enrichment of the faecal specimens in broth the greatest number of positive specimens was obtained by the fluorescent antibody technique. It was possible by means of this technique to demonstrate the organisms in 15 infants and one adult in 35 specimens, whereas conventional culture, all modifications together, revealed them in 12 infants in 26 specimens. The time for putting a diagnosis is greatly reduced by the fluorescent method. The methods didvantages and its use in routine practice are discussed.

Fecal bacterial flora of four nordic population groups with diverse incidence of large bowel cancer.

Fecal samples were collected and biologically examined from 4 population groups, exhibiting a 3-fold range in colon cancer incidence, in Denmark and Finland. Carrier rates and counts per gram feces of several aerobic as well as anaerobic genera, including nuclear dehydrogenase-producing clostridia, were calculated. The results obtained with the described method did not confirm a relationship between colon cancer incidence and carrier rates of intestinal bacteria.

Systematische Impfung mit kombiniertem Impfstoff (Diphtherie, Tetanus, Pertussis) im Säuglingsalter. Serologische und klinische Studien

ZusammenfassungDie Verfasser legen das Ergebnis der Impfung bei Säuglingen mit einem kombinierten Impfstoff (Diphtherie, Pertussis, Tetanus) vor.Serologisch wurden 366 Kinder untersucht, von denen 325 3 Injektionen von je 1 ml und 41 2 Injektionen von je 1 ml Impfstoff mit Beginn im Alter von 3 Monaten erhalten hatten. Bei dreimaliger Verabreichung des Impfstoffs war das serologische Ergebnis, das etwa 3–6 Wochen nach der letzten Impfung festgestellt wurde, besonders befriedigend (mit dem Vaccine Nr. 5, das in 185 Fällen gegeben wurde, zeigten 91% der Kinder einen Diphtherie-Titer von 0,50 E oder mehr je Milliliter und 94% einen Keuchhustentiter von 1/320 oder mehr. Bei nur zweimaliger Verabreichung war das Ergebnis weniger zufriedenstellend (54% Diphtherie-Titer ⪚0,50 E/ml, 54% Keuchhustentiter ⪚1/320).In einer klinischen Untersuchung wurde die Häufigkeit der Erkrankung an Keuchhusten bei 315 geimpften Kindern mit der von 289 nichtgeimpften Kontrollen während einer Zeitspanne von 5 Jahren verglichen. Über die Grundimmunisierung mit 3 Injektionen hinaus hatten 24% der Kinder eine 4. Injektion erhalten. Die Zahl der Erkrankungsfälle je 1000 Beobachtungsmonate war bei den Geimpften 0,57 gegen 4,56 bei den Kontrollkindern, was also einem Verhältnis von 1:8 entspricht.Von besonderer Bedeutung ist es, daß selbst gegen Ende der 5jährigen Beobachtungszeit ein beträchtlicher Unterschied in der Erkrankungsfrequenz vorlag. Die bei den geimpften Kindern nur seltenen Erkrankungen waren fast ohne Ausnahme sehr leicht, während bei den Kontrollkindern viele Fälle von schwerem und mittelschwerem Keuchhusten auftraten.