A study of post-operative wound infection in a provincial general hospital

Sources of staphylococcal infection in surgical wound sepsis

1. In two hospitals, post-operative staphylococcal wound sepsis occurred with equal frequency in patients who were and in those who were not nasal carriers of Staph. aureus.

2. Nasal carriage of Staph. aureus was not always associated with skin carriage at the site of operation, but even patients who were skin carriers suffered no more sepsis than non-carriers.

3. Self-infection was a less frequent cause of sepsis than was cross-infection. Other investigations of this type have revealed conflicting findings on the frequency of self-infection. These may be due to differences in the epidemiological properties of staphylococci infesting the hospitals; to different methods of preoperative skin preparation; and to the different types of operation concerned.

4. In one of the hospitals, 31% of probable operating-room infections were with organisms similar to those carried by some member of the surgical team. In infections thought to have occurred in the ward, only 10% showed this similarity. In 11 of 35 presumed operating-room infections, the source may have been a member of the surgical team.

For help and co-operation we are grateful to Mr G. A. Mason, Senior Surgeon, Newcastle Regional Thoracic Surgery Service; and Dr Joan Millar, Miss G. Jones, Miss E. Smith, Mrs Jean Best, Miss Winifred Mahon, Dr K. Hodgkin, Dr W. Stewart, Mr S. Griffin, Mr W. C. Barnsley, Mr R. Dobson, Mr W. H. Bound, and many nurses and other hospital workers. Our especial thanks are due to Professor R. E. O. Williams, who phage-typed many of the staphylococci, and then taught us to do this for ourselves.

Primary postoperative wound infection due to Staphylococcus pyogenes

Using S. pyogenes as a tracer organism, an examination of the importance of air-borne infection of clean wounds in the modern, plenum-ventilated operating room has been made. It appears that, for most surgical procedures, additional ultra-clean air installations are not necessary. It has been shown that even if the air is sterile, the skin remains a possible source of infection. This is especially so as far as the patient's skin is concerned. It will remain so, since the skin cannot be sterilized. Indeed, until the ecology of the skin is better understood, rigorous efforts directed toward its disinfection may compromise its inherent defense mechanisms and its protective bacterial flora. It will be argued by some that operating rooms with ultraclean air should be afforded for certain specialized procedures in sugery; for example, those in which prosthetic materials are being implanted or in which the patient's immune mechanisms are depressed. Although not disagreeing with this, I wish to note that the only controlled trial on this aspect of surgery that exists to date shows no advantage for patients randomly apportioned to have hip arthroplasty, either in an isolator or in the same modern operating room but without the isolator. From this experience, I believe that any further trial of this nature, if it is to be controlled to a similar high level, will require very large numbers of patients to show even a marginal advantage for ultraclean air or isolator installations over the modern, plenum-ventilated and meticulously managed operating suite. The verdict on the need to install ultraclean air plant for operating rooms must, therefore, be couched in the third alternative that exists under Scots Law-- "not proved." I suggest the money could be better spent on devising methods to keep skin pathogens out of surgical wounds. Perhaps more urgently, there is a need to discover how to increase the defense mechanisms of the wound milieu to implanted harmful bacteria. There is also a pressing need to improve the ward environment with the aim of diminishing secondary infections of surgical wounds.

Importance of the carrier state as a source of Staphylococcus aureus in wound sepsis

The relationship of pre-operative nasal and skin carriage of Staphylococcus aureus to wound colonization and sepsis was studied in 269 patients. Thirty-seven per cent of 96 carriers developed wound colonization as compared to 16 % among non-carriers (a statistically significant difference). The wound sepsis rates were 17 % and 9 % respectively. The combination of nasal and skin carriage was an important factor, since the sepsis rate among skin carriers (most of whom were nasal carriers as well) was 22%. Among carriers, the homologous strain was recovered from the majority of wound colonizations and from all instances of wound sepsis. A carrier strain also was recovered from 52% of the wounds colonized and from 50% of septic wounds in the entire study group. Profuse nasal carriage resulted in a significantly greater number of septic wounds (31%) than sparse carriage (9%). Wound cultures before closure, and skin from the initial incision site only once yielded a patient's carrier strain or a strain of Staph. aureus that was later recovered from the wound. The results indicate that measures designed to control the carrier state or to isolate the wound from the external environment should reduce wound sepsis by approximately one half.

Excellent technical aid was furnished by Eleanor Ford, R. N., Edith E. Silverman, Adrienne Marus, M. S., and Patricia Welch.