A method for multiple synchronous collection of airborne organisms and the effects on colony counts of various processing procedures

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.

A comparison of prophylactic antibiotic regimens against airborne orthopaedic wound contamination

Deep infection remains a major complication of joint replacement surgery despite advances in theatre design, surgical technique and antibiotic prophylaxis. Major randomized controlled trials to determine the most effective antibiotic prophylaxis are difficult to construct and interpret. In a conventional theatre, most orthopaedic intra-operative wound contamination arrives by the airborne route. This paper describes a unique method used to compare antibiotics against airborne bacteria. Seven antibiotics were incorporated into blood agar at concentrations equivalent to serum levels. Plates were then exposed to airborne theatre bacteria using a multiple synchronous collection technique. After incubation, the percentage kill was calculated for each antibiotic. At concentrations equivalent to serum level 1h post i.v. dose, all the antibiotics proved highly effective, with kill rates > 95%. Imipenem and co-amoxiclav significantly outperformed the other antibiotics with kill rates of 99.6% and 99.4%, respectively. At trough levels, the antibiotics achieved kill rates from 61% to 97.6%. Future randomized controlled trials comparing large numbers of antibiotics in the setting of an already low infection rate are inappropriate. This technique for comparing antibiotic prophylaxis in quick, inexpensive and repeatable. The superiority of imipenem is not unexpected, but of more interest is the effectiveness of co-amoxiclav over the presently favoured cefuroxime.

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.