The method used to dry washed hands affects the number and type of transient and residential bacteria remaining on the skin.

BACKGROUND: Widespread antibiotic resistance has led to fears that we are entering a post-antibiotic era and the relatively simple premise of hand washing to reduce transfer of bacteria and viruses has never been more important. Much of the emphasis has been on hand-washing technique, type of soap, and maintaining compliance but effective drying of the hands is just as important. AIM: To compare the efficacy of drying washed hands with a jet air dryer or paper towels to remove transient bacterial contamination and to determine the effect on residential flora. METHODS: Eighty volunteers were recruited. The entire surfaces of volunteers' hands were artificially contaminated with Escherichia coli before being washed and dried; then bacteria remaining on the skin were recovered and enumerated. In the second part of the study the number and types of bacteria comprising the natural flora remaining on washed and dried hands were determined. FINDINGS: Significantly fewer transient and residential bacteria remained on the skin if hands were dried with a jet air dryer (P < 0.001). Drying hands with paper towels increased the number of resident bacteria, including potentially pathogenic species, released from the volunteers' skin, compared to a jet air dryer. CONCLUSION: The number and types of bacteria remaining on washed hands were affected by the drying method. Hands dried with a jet air dryer harboured fewer viable bacteria, reducing the risk of infection transmission via touch. This could be especially important for healthcare workers who are constantly in contact with large numbers of vulnerable patients.

Mechanism of copper surface toxicity in Escherichia coli O157:H7 and Salmonella involves immediate membrane depolarization followed by slower rate of DNA destruction which differs from that observed for Gram-positive bacteria.

We have reported previously that copper I and II ionic species, and superoxide but not Fenton reaction generated hydroxyl radicals, are important in the killing mechanism of pathogenic enterococci on copper surfaces. In this new work we determined if the mechanism was the same in non-pathogenic ancestral (K12) and laboratory (DH5α) strains, and a pathogenic strain (O157), of Escherichia coli. The pathogenic strain exhibited prolonged survival on stainless steel surfaces compared with the other E. coli strains but all died within 10 min on copper surfaces using a 'dry' inoculum protocol (with approximately 10(7) cfu cm(-2) ) to mimic dry touch contamination. We observed immediate cytoplasmic membrane depolarization, not seen with enterococci or methicillin resistant Staphylococcus aureus, and loss of outer membrane integrity, inhibition of respiration and in situ generation of reactive oxygen species on copper and copper alloy surfaces that did not occur on stainless steel. Chelation of copper (I) and (II) ionic species still had the most significant impact on bacterial survival but protection by d-mannitol suggests hydroxyl radicals are involved in the killing mechanism. We also observed a much slower rate of DNA destruction on copper surfaces compared with previous results for enterococci. This may be due to protection of the nucleic acid by the periplasm and the extensive cell aggregation that we observed on copper surfaces. Similar results were obtained for Salmonella species but partial quenching by d-mannitol suggests radicals other than hydroxyl may be involved. The results indicate that copper biocidal surfaces are effective for Gram-positive and Gram-negative bacteria but bacterial morphology affects the mechanism of toxicity. These surfaces could not only help to prevent infection spread but also prevent horizontal gene transmission which is responsible for the evolution of virulent toxin producing and antibiotic resistant bacteria.

Mechanism of copper surface toxicity in vancomycin-resistant enterococci following wet or dry surface contact.

Contaminated touch surfaces have been implicated in the spread of hospital-acquired infections, and the use of biocidal surfaces could help to reduce this cross-contamination. In a previous study we reported the death of aqueous inocula of pathogenic Enterococcus faecalis or Enterococcus faecium isolates, simulating fomite surface contamination, in 1 h on copper alloys, compared to survival for months on stainless steel. In our current study we observed an even faster kill of over a 6-log reduction of viable enterococci in less than 10 min on copper alloys with a "dry" inoculum equivalent to touch contamination. We investigated the effect of copper(I) and copper(II) chelation and the quenching of reactive oxygen species on cell viability assessed by culture and their effects on genomic DNA, membrane potential, and respiration in situ on metal surfaces. We propose that copper surface toxicity for enterococci involves the direct or indirect action of released copper ionic species and the generation of superoxide, resulting in arrested respiration and DNA breakdown as the first stages of cell death. The generation of hydroxyl radicals by the Fenton reaction does not appear to be the dominant instrument of DNA damage. The bacterial membrane potential is unaffected in the early stages of wet and dry surface contact, suggesting that the membrane is not compromised until after cell death. These results also highlight the importance of correct surface cleaning protocols to perpetuate copper ion release and prevent the chelation of ions by contaminants, which could reduce the efficacy of the surface.

Biocidal efficacy of copper alloys against pathogenic enterococci involves degradation of genomic and plasmid DNAs.

The increasing incidence of nosocomial infections caused by glycopeptide-resistant enterococci is a global concern. Enterococcal species are also difficult to eradicate with existing cleaning regimens; they can survive for long periods on surfaces, thus contributing to cases of reinfection and spread of antibiotic-resistant strains. We have investigated the potential use of copper alloys as bactericidal surfaces. Clinical isolates of vancomycin-resistant Enterococcus faecalis and Enterococcus faecium were inoculated onto copper alloy and stainless steel surfaces. Samples were assessed for the presence of viable cells by conventional culture, detection of actively respiring cells, and assessment of cell membrane integrity. Both species survived for up to several weeks on stainless steel. However, no viable cells were detected on any alloys following exposure for 1 h at an inoculum concentration of

Therapy of human T-cell acute lymphoblastic leukaemia with a combination of anti-CD7 and anti-CD38-SAPORIN immunotoxins is significantly better than therapy with each individual immunotoxin.

Severe combined immunodeficient (SCID) mice injected i.v. with the human T-ALL cell line CCRF CEM (SCID-CEM mice) develop within 50 days life-threatening multi-organ growth of leukaemia cells. The development of leukaemia in SCID-CEM mice treated with three 10 microg i.v. doses of the anti-CD7 immunotoxin (IT) HB2-SAPORIN or the anti-CD38 IT OKT10-SAPORIN was significantly delayed compared with PBS sham-treated animals but 90% of animals treated with either IT eventually developed disseminated leukaemia cell growth. In contrast treatment of SCID-CEM mice with a combination of both ITs led not only to a significantly greater delay in time to leukaemia development but also in the numbers of animals remaining leukaemia free (60%). The native HB2 and OKT10 antibodies (both murine IgG1antibodies) exerted significant, though relatively weak therapeutic effects, probably mediated through an antibody-dependent cellular cytotoxicity (ADCC) mechanism. Moreover, there was no in vivo additivity of therapeutic effect when both antibodies were used in combination. Apparent, however, was that the combination of HB2-SAPORIN IT with OKT10 antibody led to an intermediate therapeutic effect that was significantly greater than that obtained when either was used alone but significantly less than that obtained when the two IT combination was utilized. This was similarly the case for the combination of OKT10-SAPORIN IT with HB2 antibody though the effect was less pronounced in this instance. This result suggests that the therapeutic effect of IT + antibody treatment results from an additivity between antibody-mediated delivery of saporin combined with a SCID mouse NK cell-mediated ADCC attack on the target cell directed through target cell bound antibody Fc engagement with FcgammaRIII on the NK cell surface. The combination of both ITs however gave the best therapeutic outcome in SCID-CEM mice probably as the result of (i) delivery of greater amounts of saporin to target CEM cells positive for both CD7 and CD38, (ii) delivery of an effective dose of saporin to CEM cells downregulated or negative for one of the target antigens and (iii) through ADCC mechanisms that interact additively with IT action. We have previously proposed that combination IT therapy would be one means of overcoming the problem of heterogeneity of antigen expression within a global tumour cell population and these additional findings support this and provide a further strengthening of the rationale for employing cocktails of ITs for the treatment of human malignancies.

Anti-CD7 antibody and immunotoxin treatment of human CD7(+)T-cell leukaemia is significantly less effective in NOD/LtSz-scid mice than in CB.17 scid mice.

Groups of 8 to ten SCID (CB.17 scid/scid) or NOD/SCID (NOD/LtSz- scid/scid) mice were injected i.v. with two million human HSB-2 T-ALL cells on day 1 (SCID-HSB-2 and NOD/SCID-HSB-2 mice) and treated later with 3 i.v. 10 microg doses of the anti-CD7 antibody HB2 on days 7, 9 and 11 or with a single 10 microg dose of HB2-SAPORIN or a 7.4 microg dose of HB2-F(ab)(2)-SAPORIN immunotoxin (IT) on day 7. Treatment of SCID-HSB-2 mice with HB2-SAPORIN led to a significant prolongation in the time to development of signs and symptoms of disease compared with PBS sham-treated controls with 80% of animals surviving disease-free. In contrast treatment with HB2-F(ab)(2)-SAPORIN was significantly less effective in SCID-HSB-2 mice with 80% of animals in this treatment group developing leukaemia over the course of the study. HB2 antibody treatment of SCID-HSB-2 mice also led to a significant prolongation in time to leukaemia development compared with sham-treated controls with 37% of animals in this treatment group disease-free at termination of the study. In contrast HB2 antibody treatment of NOD/SCID-HSB-2 mice had no therapeutic effect in these animals and the therapeutic effectiveness of both HB2-SAPORIN and HB2-F(ab)(2)-SAPORIN ITs was similar and significantly reduced compared to the effect observed in SCID-HSB-2 mice. It was initially thought that the lack of therapeutic effect of antibody and IT in NOD-SCID-HSB-2 mice might relate to their putative lack of NK cells but flow cytometric and functional studies with NOD-SCID mouse splenocytes revealed that these animals do have some functional NK cells though fewer in number and possibly lower in functionality than those of SCID mice. We reason that the complete lack of therapeutic effect of HB2 antibody and the reduced effect of HB2-SAPORIN in NOD/SCID mice is due to the reduced cytolytic activity of NOD/SCID NK cells which is probably below a certain critical threshold value in these animals. We conclude from this that immunotherapeutics like HB2-SAPORIN would be more accurately assessed for intrinsic potency in NOD/SCID mice where the effects of NK cell and possibly other non-adaptive immune mechanisms would not have a significant influence.

Contribution of host-derived growth factors to in vivo growth of a transplantable murine mammary carcinoma.

The contribution of host-derived growth factors to tumour growth in vivo was studied using the transplantable murine mammary carcinoma, MT1, grown in syngeneic mice. Promotion of growth of the mammary carcinoma by a factor(s) from the host was evident in experiments in which the carcinoma cells were inoculated intraperitoneally. In this environment, tumours develop as multiple solid nodules, each probably arising from an individual cell or a small cluster of cells. Tumour growth was found to occur in the peritoneal cavity following inoculation of 10(3) cells, but an inoculum of as few as ten cells grew if a leucocyte-rich exudate had first been induced. To determine which host-derived growth factors might contribute to growth of MT1, extracts of the tumour were first examined for growth factor activity. Fractionation of tumour extracts by either ion-exchange chromatography or gel filtration revealed several peaks of mitogenic activity, but none of this could be attributed to epidermal growth factor (EGF). Accordingly, an anti-EGF antibody was tested as a putative inhibitor of tumour growth as any effect of this antibody could be ascribed to removal of EGF derived from the host. The antibody was found to have potent anti-tumour activity when tested against MT1 tumours that had been inoculated into the peritoneal cavity. In contrast, the antibody had little effect on growth of the discrete tumour mass which formed when MT1 was transplanted subcutaneously. The results suggest that host-derived EGF contributes to establishment of microcolonies of MT1 carcinoma within the peritoneal cavity. This may be directly, by providing growth factors to supplement those produced by the tumour until it reaches a certain critical mass to sustain autocrine growth, or indirectly, by affecting the production of other growth-stimulatory factors or cytokines.