Skin Bacteriology and Surgical Wound Infection

Abstract

Transient and resident skin bacteria constitute a potent source of surgical wound contamination. Present methods of skin disinfection are efficient enough to result in 80% temporary sterility of the human skin. A study was underaken in search of further information on the skin bacteriology in relation to postoperative wound infection. The clinical series consists of 103 patients (63 male and 40 female) treated operatively at the Clinic for Thoracic Surgery, University of Helsinki, in February-March, 1966. Their average age was 41 years, with a range of 17–76 years. Of the operations, 28 were performed for various cardiac conditions, 35 for other intrathoracic diseases and 40 for abdominal and other disorders. Different preoperative skin treatments were applied in the three groups. Cardiac patients were prepared by local pHisohex washing during several preoperative days and the other thoracotomy patients were usually likewise treated on the last day preceding operation. Ordinary immediate skin disinfection was carried out in all three groups. The skin bacteriology was studied on the basis of three specimens from each patient: (1) a swab specimen taken from the skin surface prior to immediate skin disinfection before operation; (2) a skin biopsy; and (3) a swab specimen from the wound surface immediately after wound closure. Bacterial growth occurred in 61, 14.5 and 55% of the specimens of type (1), (2) and (3), respectively. Staphylococcus aureus was isolated from 20 patients, Escherichi coli or Bac. paracoli from eight, Staph. albus from 42, Bac. subtilis from 20 and Gaffkya tetragena from ten patients. Pathogenic bacteria seemed to have a tendency to be associatd with increased risk of exudative wound reactions and delayed healing. The incidence of wound complications was highest in the group of cardiac operations and lowest in that of abdominal and general surgery. Major operations involving prolonged exposure and longer period of tissue damage owing to compression, diathermy, etc. are more likely to be complicated by disturbances of wound healing, which may lead to accumulation of unresorbable exudate and to its external drainage. The exudate is sterile at the beginning, but may become secondarily infected and cause bacterial invasion of the wound area. It seems appropriate to continue the practice of cumulative skin disinfection in such cases. Surgical trauma produces inflammatory reaction in every incision. Its strength depends on the degree of tissue damage and of necrosis caused by various associated, e.g. physical, chemical or bacterial factors. High standard of caution in surgical technique may be of even greater significance than initial bacterial contamination. The two main groups of skin bacteria, resident flora and transient flora, may both constitute the source of microorganisms responsible for surgical wound infections. Aseptic conditions have been shown to be of essential importance to successful surgical treatment and it is, therefore, interesting to note that present methods of skin disinfection enable only about 80 per cent of temporary sterility of the human skin to be achieved. The majority of all wounds are bac-teriologically contaminated at the end of the operation (Rubbo & Gardner, 1965). Morris, Barnes & Burke (1966) speak of an “irreducible minimum” of wound infections because a 2–6 per cent incidence of wound sepsis occurs despite high aseptic standards in clean operations. They discuss whether this incidence might be further lowered by reducing the bacterial contamination or by altering the host-bacterial balance in the patient's favour. The present study was undertaken in order to gain information on skin bacteriology and on its relations to various methods of preoperative skin preparation and to postoperative wound infections.