Assessment of airborne bacterial contamination of clean wounds: results in a tissue model

Antibacterial effect of antibiotic-loaded SBA-15 on biofilm formation by Staphylococcus aureus and Staphylococcus epidermidis

Staphylococcus aureus and Staphylococcus epidermidis are human pathogens involved in implant-related infections. During those diseases, they are able to form biofilms showing resistance to the effect of many different antibiotics. Drug delivery systems allow a local and effective delivery of antibiotics at high concentrations in the infected tissue without causing the cytotoxic effects commonly linked to systemic administration. We report the use of a porous ceramic biomaterial, such as SBA-15 loaded with antibiotics, to deliver them directly to the infected tissue. SBA-15 discs were loaded with Vancomycin, Rifampin and a combination of both, introduced in a suspension of S. aureus 15981 and S. epidermidis ATCC 35984 and incubated during 6 and 24 h. A statistically significant decrease in the biofilm density and the number of viable bacteria was detected for all antibiotics at 6 h in both bacteria. Rifampin showed an increase in the biofilm density and the number of viable bacteria at 24 h. No differences were detected between Vancomycin and the combination of antibiotics. S. epidermidis was more sensitive to the effect of the antibiotics than S. aureus. Here we have demonstrated that SBA-15 is able to act as an effective drug delivery system not only from a pharmaceutical point of view, but also from a biological one.

Intraoperative contamination influences wound discharge and periprosthetic infection

Intraoperative bacterial contamination increases risk for postoperative wound-healing problems and periprosthetic infection, but to what extent remains unclear. We asked whether bacterial contamination of the instruments and bone during primary prosthesis insertion was associated with prolonged wound discharge and subsequent periprosthetic infection. During 100 total hip arthroplasties, four intraoperative cultures were taken from the instruments and two portions of removed bone. Postoperatively, the duration of wound discharge was monitored, with Day 5 as the cut-off point. All patients were followed for 2 years to determine whether periprosthetic infection occurred. Bacterial contamination occurred in 36 operative procedures (36%). We found an association between intraoperative contamination and prolonged wound discharge, with a relative risk of 2.5. The culturing of removed bone had a positive predictive value of 81% to 90%. Other factors associated with prolonged wound discharge were rheumatoid arthritis (relative risk, 6.4), use of cement (relative risk, 1.6), and increased blood loss (relative risk, 1.5).

Wound ventilation with carbon dioxide: a simple method to prevent direct airborne contamination during cardiac surgery?

Carbon dioxide (CO2) insufflation in the cardiothoracic wound cavity is used in open-heart surgery for prevention of arterial air embolism. The objective of this study was to investigate if CO2 insufflation may influence the rate of airborne contamination of the cardiothoracic wound. This was studied in a cardiothoracic wound cavity model that contained two 9 cm blood agar plates. Contamination rates were compared between a control without insufflation and insufflation with: (1) a thin open-ended tube or a gas-diffuser, (2) air or CO2, and (3) CO2 flows of 5 or 10 L/min. CO2 insufflation at 5 L/min with an open-ended tube resulted in a contamination rate almost four times that of the control (P = 0.01), whereas with the gas-diffuser the contamination rate decreased (P = 0.01). With the gas-diffuser, air insufflation at 5 L/min markedly reduced the contamination rate compared with the control (P < 0.001), but was less protective than CO2 insufflation at the same flow (P < 0.001). With both gases, the contamination rate was particularly low close to the gas-diffuser (P < 0.001). Increasing the CO2 flow from 5 to 10 L/min reduced the average contamination rate in the model from 30% to 22% (P < 0.001) of the control. At a CO2 flow of 10 L/min the contamination rate within 9 cm of the gas-diffuser was 14% of the control. Intraoperative wound ventilation with CO2 using a gas-diffuser may not only prevent air embolism, but may also significantly reduce the risk of airborne contamination and postoperative wound infection in cardiac surgery. In contrast, insufflation with an open-ended tube substantially increases these risks.

Importance of air quality and related factors in the prevention of infection in orthopaedic implant surgery

Small numbers of organisms can cause orthopaedic implant infections, which give rise to a considerable degree of morbidity and also mortality. The periprosthetic infection rates have been shown to correlate with the number of airborne bacteria within 30 cm of the wound. This is influenced by factors such as the number of operating theatre personnel, their clothing and the type of ventilation system used. Guidance on routine bacteriological monitoring of ultraclean air theatres, based on the Department of Health document Health Technical Memorandum 2025, is discussed. Factors important in minimizing the number of postoperative implant infections such as the use of ultraclean air, ultraviolet radiation, different types of surgical clothing, prophylactic antibiotics and host-related factors are also discussed. The importance of proper scientific investigation into the effectiveness of practical preventative measures in the operating room is emphasized.

Wound disinfection with ultraviolet radiation

Bacteria were counted concurrently in the air and wounds during the first 20 min of total joint arthroplasty procedures in two theatres: a conventional plenum ventilated theatre with ultraviolet C (UVC) tubes installed and a filtered vertical laminar flow theatre. Four theatre environments were tested: conventional theatre and clothing; conventional theatre with UVC protective clothing, with UVC set to produce 100 or 300 microW cm-2 s-1 irradiation; and filtered vertical laminar flow air with staff wearing cuffed cotton/polyester clothing. When used, the UVC was activated 10 min after starting an operation to assess the effect of UVC clothing alone, and of UVC radiation on bacteria already present in the wound. Compared with conventional theatres, UVC clothing reduced air counts by 38%, UVC at 100 microW cm-2 s-1 by 81%, at 300 microW cm-2 s-1 by 91%, and laminar flow by 92%. Wounds counts fell correspondingly by 66% with UVC clothing, 87% with UVC at 100 microW cm-2 s-1 and 92% both with UVC at 300 microW cm-2 s-1 and laminar flow. In conventional and laminar flow theatres air and wound counts correlated closely but in UVC theatres wound counts were lower than levels expected from prevailing air counts suggesting that UVC kills bacteria in wounds as well as in air.