Journal of Hospital Infection (1984) 5, 431437 Prevention of bacterial colonization of wounds at operation: comparison of iodine-impregnated (‘Ioban’) drapes with conventional methods D. A. Lewis, D. J. Leaper* and D. C. E. Speller Department of Microbiology and * University Department of Surgery, Bristol Royal Infirmary, Bristol BS2 8HW Accepted for publication 25 May 1984 Summary: Forty-five patients undergoing clean elective inguinal surgery were randomly allocated to receive one of three skin preparations, (1) alcoholic povidone-iodine (‘Betadine’) alone, (2) the same covered with an incise drape (‘Steri-Drape’), or (3) an iodine-containing incise drape (‘Ioban’) alone. The first two preparations were superior in reducing bacter- ial colony counts measured on skin with cotton swabs and impression cultures. There were no clinical postoperative wound infections in any group but it is suggested that although the use of an iodine-containing incise drape alone is attractive, its bactericidal action is inferior to conventional prep- arations. Introduction The use of plastic adhesive skin drapes in surgical practice has been advocated to immobilize skin bacteria and prevent contamination of the wound (French, Eitzen and Ritter, 1976) but other studies have shown that plastic drapes do not significantly influence the number of bacteria in operation wounds (Lilly et al., 1970; Raahave, 1976) or significantly reduce the incidence of wound infection (Maxwell et al., 1969; Jackson, Pollock and Tindal, 1971; Cruse and Foord, 1973). Certainly, if the skin is inadequately dried following conventional skin preparation with aqueous or alcohol based antiseptics, the drapes may not adhere properly and any preventive effect on bacterial migration is thus reduced. ‘Ioban’ drapes (3M United Kingdom plc) are composed of a polyethylene film coated with an iodophor-containing, pressure sensitive adhesive. The manufacturers advocate their use with conventional skin preparation, which alone has been shown to achieve up to a 95 per cent reduction in the bacterial flora of the skin after a single application (Lowbury and Lilly, 1973). As it would be advantageous to the operator if these drapes could be used alone without additional skin antisepsis, we wished to see if their bactericidal action was sufficient to allow this to be done in short elective inguinal surgery. 0195-6701/84/040431+07 $03.00/O 431 0 1984 The Hospital Infection Society
Transcript
Journal of Hospital Infection (1984) 5, 431437
Prevention of bacterial colonization of wounds at operation: comparison of iodine-impregnated
(‘Ioban’) drapes with conventional methods
D. A. Lewis, D. J. Leaper* and D. C. E. Speller
Department of Microbiology and * University Department of Surgery, Bristol Royal Infirmary, Bristol BS2 8HW
Accepted for publication 25 May 1984
Summary: Forty-five patients undergoing clean elective inguinal surgery were randomly allocated to receive one of three skin preparations, (1) alcoholic povidone-iodine (‘Betadine’) alone, (2) the same covered with an incise drape (‘Steri-Drape’), or (3) an iodine-containing incise drape (‘Ioban’) alone. The first two preparations were superior in reducing bacter- ial colony counts measured on skin with cotton swabs and impression cultures. There were no clinical postoperative wound infections in any group but it is suggested that although the use of an iodine-containing incise drape alone is attractive, its bactericidal action is inferior to conventional prep- arations.
Introduction
The use of plastic adhesive skin drapes in surgical practice has been advocated to immobilize skin bacteria and prevent contamination of the wound (French, Eitzen and Ritter, 1976) but other studies have shown that plastic drapes do not significantly influence the number of bacteria in operation wounds (Lilly et al., 1970; Raahave, 1976) or significantly reduce the incidence of wound infection (Maxwell et al., 1969; Jackson, Pollock and Tindal, 1971; Cruse and Foord, 1973). Certainly, if the skin is inadequately dried following conventional skin preparation with aqueous or alcohol based antiseptics, the drapes may not adhere properly and any preventive effect on bacterial migration is thus reduced.
‘Ioban’ drapes (3M United Kingdom plc) are composed of a polyethylene film coated with an iodophor-containing, pressure sensitive adhesive. The manufacturers advocate their use with conventional skin preparation, which alone has been shown to achieve up to a 95 per cent reduction in the bacterial flora of the skin after a single application (Lowbury and Lilly, 1973). As it would be advantageous to the operator if these drapes could be used alone without additional skin antisepsis, we wished to see if their bactericidal action was sufficient to allow this to be done in short elective inguinal surgery.
0195-6701/84/040431+07 $03.00/O
431
0 1984 The Hospital Infection Society
432 D. A. Lewis et al.
Patients, materials and methods
Forty-five patients undergoing clean elective inguinal surgery, including inguinal and femoral herniorrhaphies and saphenofemoral ligations for varicose veins were entered into the trial. They all had a general anaesthetic. The skin was closed with interrupted fat sutures using plain catgut and a subcuticular continuous proline suture. The patients were randomly allocated to receive one of three skin preparations, (1) alcoholic 10 per cent w/v povidone-iodine containing 1 per cent available iodine (‘Betadine’, Napp Laboratories), (2) povidone-iodine with an incise drape (‘Steri- Drape’, 3M United Kingdom plc), (3) ‘Ioban’ drape with no skin preparation.
Microbiological investigations Two types of microbiological sample were taken to quantitate skin flora: impression cultures and cotton wool swabs. These methods were selected for their practicability. The impression cultures consisted of standard dip- inoculum spoons (Medical Wire and Equipment Ltd), as used for urine culture, which were loaded with 5 per cent horse blood agar containing 0.5 per cent sodium thiosulphate, to neutralize any remaining iodine (Rubbo and Gardner, 1965). Preliminary experiments were performed to ensure that the iodine was neutralized by the sodium thiosulphate. Plastic surfaces were either left untreated or coated with povidone-iodine; the surfaces were inoculated with broth cultures of clinical isolates of Staphylococcus aweus and Escherichia coli; impression cultures were then taken with the thiosulphate-containing medium and the counts of bacteria recovered were compared. In the trial, impression cultures were taken by placing the spoon, agar-side down, on to the skin and applying gentle pressure for 5 s. All samples were taken by the same operator throughout and were taken on two occasions during the operation, (1) at the site of proposed skin incision before skin preparation, (2) at approximately the same site at the edge of the wound after skin closure. The other specimens taken were plain cotton swabs (Medical Wire and Equipment Ltd) soaked in sterile saline and rubbed five times backwards and forwards across 3 cm of skin or subcutaneous tissue. The swabs were than turned over and the process repeated. Swabs were placed in modified Stuart’s transport medium (Oxoid) with 0.5 per cent sodium thiosulphate and sent immediately to the laboratory. Swabs were taken at the same times as the impression cultures, and additional intraincisional swabs were taken following skin incision and before skin closure.
On receipt in the laboratory the swabs were plated by the M-technique (Figure l), devised by Dr V. G. Alder and Dr R. A. Simpson (personal communication), on to 5 per cent horse blood agar and MacConkey’s bile salt-lactose agar, for aerobic incubation, and 5 per cent horse blood agar, for anaerobic incubation, all at 37°C. Colony counts were made at 1 and 3 days
Wound contamination at operation 433
Figure 1. M-plating technique. The swab is streaked on the plate in the first quadrant in the form of an M, the swab being rotated as this is done (a). The second quadrant is then inoculated from the first with four separate streaks with a sterile loop (b). The third quadrant is inoculated from the second (c) and the fourth from the third (d) in the same way. Tenfold reductions in colony numbers occur in the successive quadrants. Colony counts are made from the appropriate quadrant (approximately 10-50 colonies).
and anaerobic counts repeated after 7 days to account for slow growing anaerobic organisms. Impression cultures were incubated aerobically at 30°C a lower temperature being chosen to facilitate counting when there was a heavy growth. Colony counts were performed after overnight incubation.
The Wilcoxon’s signed ranks test was used throughout for statistical analysis.
Results
The ‘Ioban’ drapes were easy to use and adhered well to the skin. Bacteria grown from swabs and impression cultures were predominantly
normal skin flora, coagulase-negative staphylococci and corynebacteria. Figure 2 shows the colony counts obtained from the impression cultures, taken before and at the end of the operation. In all three groups there was a decline in counts, a statistically significant fall in the two groups receiving skin disinfection with ‘Betadine’, and a less marked reduction in the group receiving ‘Ioban’ drapes. The results from the swabs (Figures 3 and 4) showed similar trends but invariably there was not a statistically significant reduction from pre-operative counts in the ‘Ioban’ drape group.
434 D. A. Lewis et al.
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Figure 2. Colony counts from impression cultures taken before and at the end of operation (medians and semi-quartile ranges).
Figures 5 and 6 show the colony counts from the intraincisional swabs taken after skin incision and again before skin closure. Although 28 per cent of these specimens were sterile, and from those that did produce bacterial growth the numbers of colonies were often very small, there was a tendency in all groups for counts to increase during the operation. The effect was
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Figure 3. Colony counts from swabbing by M-technique on blood agar, incubated aerobically; swabs taken before and at the end of operation (medians and ranges).
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Figure 4. Colony counts from swabbing by M-technique on blood agar, incubated anaerobically; swabs taken before and at the end of operation (medians and ranges).
most marked in the group with ‘Ioban’ drapes. The results for counts obtained on MacConkey’s agar are not shown but were similar to those obtained on aerobic and anaerobic culture.
None of the 45 patients had clinical evidence of a wound infection postoperatively.
Figure 5. Colony counts from intraincisional swabs plated by M-technique on to blood agar, incubated aerobically; swabs taken at beginning and end of operation.
436 D. A. Lewis et al.
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Figure 6. Colony counts from intraincisional swabs plated by M-technique on to blood agar, incubated anaerobically; swabs taken at beginning and end of operation.
Discussion
The attraction to us of an incise drape impregnated with an antiseptic was that-it might be possible to use it without additional skin preparation. This would make the pre-operative preparation far quicker and simpler.
Previous work (J. A. Ulrich, unpublished data for 3M United Kingdom plc) showed that ‘Ioban’ drapes caused a marked reduction in numbers of bacteria on the skin when compared with standard adhesive drapes. It showed that after 25 min on the skin ‘Ioban’ drapes caused a 3.8 log reduction of Staph. UUY~US and a 2.7 log reduction of E. coli whereas adhesive drapes without iodophor caused only a 1 log reduction of organisms over this period.
In our study we compared ‘Ioban’ drapes alone with conventional methods of skin preparation: povidone-iodine with and without ‘Steri- Drape’. ‘Ioban’ drapes proved to be inferior to the other two methods in terms of reducing bacterial colony counts of the skin. The reason for the inferior performance of ‘Ioban’ drapes may have been that there was less iodine available on the skin to produce a bactericidal effect. We saw no clinical postoperative wound infections but this was to be expected in a group of patients undergoing clean surgery of this kind.
It has been suggested that incise drapes may prevent bacterial migration from the skin into the wound during the operation (French et al., 1976) but their current popularity cannot really be attributed to this and is probably mainly due to the protection and support that they offer when applied to the wound postoperatively. In fact our study showed that, despite the use of incise drapes, there was a tendency for bacterial colony counts from
Wound contamination at operation 437
intraincisional swabs to increase during the operation, suggesting bacterial migration into the wound. It is possible, however, that multiplication of bacteria was responsible for some of the small increases in colony counts observed during longer operations. The increase in counts was most marked when ‘Ioban’ drapes were used and occurred in spite of their good adherence to the skin. Raahave (1976) obtained similar findings in a study comparing standard skin preparation with skin preparation plus an incise drape. The standard skin preparation in that study was two applications of 0.5 w/v per cent alcoholic chlorhexidine.
In one patient we observed a very large increase in numbers of organisms in anaerobic culture (mainly propionibacteria) that occurred in the wound during the operation (Figure 6). Although we have no proof, this could have been explained perhaps by an accidental puncture of the surgeon’s glove or some other factor allowing the release of a large number of skin organisms into the wound.
Our results do not support the use of ‘Ioban’ drapes alone, because the deficiency of antibacterial activity outweighs the practicality and ease of the method.
We are grateful to Dr R. A. Simpson for the M-plating method of bacterial counting.
References
Cruse, P. J. E. & Foord, R. (1973). A five-year prospective study of 23,649 surgical wounds. Archives of Surgery 107. 206-210.
French, M. L.-V., E&en, H. E. & Ritter, M. A. (1976). The plastic surgical adhesive drape: an evaluation of its efficacy as a microbial barrier. Annals of Surgery 184, 46-50.
Jackson, D. W., Pollock, A. V. & Tindal, D. S. (1971). The value of a plastic adhesive drape in the prevention of wound infection. A controlled trial. British journal of Surgery 58, 340-342.
Lilly, H. A., Lowbury, E. J. L., London, P. S. & Porter, M. F. (1970). Effects of adhesive drapes on contamination of operation wounds. Lancet 2. 431432.
Lowbury, E. J. L. & Lilly, H. A. (i973). Use of 4% detergent’solution (Hibiscrub) and other methods of skin disinfection. British Medical Yournal 1. 510-515.
Maxwell, J. G., Ford, C. R., Peterson, D. E. & R&chards, R. C. (1969). Abdominal wound infection and plastic drape protectors. American Journal of Surgery 118, 844-848.
Raahave, D. (1976). Effect of plastic skin and wound drapes on the density of bacteria in operation wounds. British Journal of Surgery 63, 421426.
Rubbo, S. D. & Gardner, J. F. (1965). A Review of Sterilisation and Disinfection. Lloyd- Luke, London.
