STAPHYLOCOCCIC WOUND INFECTIONS

Recovery of microorganisms shed by humans into a sterilized environment

An appartus and technique for quantitative comparison of the aerobic bacterial flora disseminated by human subjects has been developed. Dissemination from three healthy subjects was studied weekly for 3 weeks. Viable particles recovered ranged from 100,000 for one subject during a 30-min period to 620,000 for another subject during a 10-min period. One of the three subjects showed appreciably less variation in numbers of organisms shed than did the other two subjects. When the subjects were examined on consecutive days while wearing sterilized clothing, total particles recovered were reduced and variations in recoveries from run to run were slightly lessened. Three consistent nasal carriers of S. aureus were measured for dissemination. No viable Staphylococcus aureus was recovered from two of the carriers. However, 460,000 typable S. aureus particles were recovered during a 60-min period from the third carrier.

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.

Wound infection following laryngectomy. The effect of topical ampicillin and carbenicillin

A study of twenty-two consecutive laryngectomies performed in one unit is reported. In eleven controls, seven (67%) developed a wound infection. In eleven patients, IG of Ampicillin and IG of Carbenicillin were used topically, and three (18%) developed a wound infection (P less than 0-04). Studies of the bacterial flora at the time of operation suggest that the major source of wound contamination is colonization of the upper gastrointestinal and respiratory tract. The ease with which a small innoculum of pathogens produces wound infection in these patients is discussed, and it is suggested that the underlying defect is depression of host cellular immunity resulting in failure of bacterial destruction by activated macrophages.

The effect of topical ampicillin on wound-infection rate after cholecystectomy

No carefully controlled trial of the use of topical ampicillin in cholecystectomy wounds has been described. A series of 100 consecutive cholecystecomies performed by one surgeon using this drug in a double-blind manner is reported. The efficacy of topical ampicillin in lowering the wound-infection rate as shown by other authors is not confirmed.

A bacteriological study of the immediate environment of a surgical wound

In an attempt to assess the importance of different aspects of the immediate wound environment during an operation, detailed bacteriological data were obtained in the operating theatre from 1000 patients operated upon in two different theatres.

Nasal and skin carriage of Staphylococcus pyogenes were found to be associated with a small number of autogenous infections, but no significant increase in the staphylococcal wound infection incidence could be shown in these groups. Skin carriage of other pathogens seemed to be of no importance with the disinfection methods used in the present study.

Settle-plate studies showed no apparent difference in the bacteriological hazard of the two operating theatre environments, neither appearing to constitute any real danger. Samples at the end of operation confirmed the importance of endogenous contamination with intestinal organisms during potentially dirty operations. Apart from the few autogenous infections, there was little evidence of staphylococcal wound sepsis arising as a result of contamination in the operating theatre. Hands and masks of members of the operating team could not be demonstrated as sources of contamination during operation.

There was no apparent difference in the bacteriological findings as they related to the different operating theatre environments.

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.

Wound infections acquired from a disperser of an unusual strain of Staphylococcus aureus

Seven post-operative wounds were infected with a strain of Staphylococcus aureus, probably acquired from a theatre orderly who suffered from a dry generalized eczema. The orderly was a nasal and heavy skin carrier, and was shown to be a disperser of the epidemic strain. Infection was probably acquired from airborne contamination in the operating theatre, since the orderly did not scrub-up. The epidemic strain (phage type 80/81 at 1,000 routine test dilution) was sensitive to penicillin and resistant to tetracycline and novobiocin. Neomycin resistance was variable. This strain was found to lose resistance to neomycin when subcultured in the absence of the antibiotic.