Hans-Günther Sonntag

Disinfection of surfaces by photocatalytic oxidation with titanium dioxide and UVA light

Particularly in microbiological laboratories and areas in intensive medical use, regular and thorough disinfection of surfaces is required in order to reduce the numbers of bacteria and to prevent bacterial transmission. The conventional methods of disinfection with wiping are not effective in the longer term, cannot be standardized, are time- and staff-intensive and use aggressive chemicals. Disinfection with hard ultraviolet C (UVC) light is usually not satisfactory, as the depth of penetration is inadequate and there are occupational medicine risks. Photocatalytic oxidation on surfaces coated with titanium dioxide (TiO2) might offer a possible alternative. In the presence of water and oxygen, highly reactive OH-radicals are generated by TiO2 and mild ultraviolet A (UVA). These radicals are able to destroy bacteria, and may therefore be effective in reducing bacterial contamination. Direct irradiation with UVC however can produce areas of shadow in which bacteria are not inactivated. Using targeted light guidance and a light-guiding sheet (out of a UVA-transmittant, Plexiglas, for example), as in the method described in the present study, bacterial inactivation over the entire area is possible. The effectiveness of the method was demonstrated using bacteria relevant to hygiene such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecium. For these bacteria, a reduction efficiency (RE) more than 6log10 steps in 60 min was observed. Using Candida albicans, a RE of 2log10 steps in 60 min was seen. Light and scanning electron microscopic examinations suggest that the germ destruction achieved takes place through direct damage to cell walls caused by OH-radicals.

The endogenous pathway is a major route for deep sternal wound infection

OBJECTIVE Deep wound infections pose an increasing problem in cardiac surgery patients. Prospective infection monitoring is thus a means of identifying possible risk factors. METHODS Within a period of 5 months, a total of 376 adult patients, 260 men and 116 women, with a mean age of 62.6 years (range 18-88), underwent coronary bypass grafting (n=281) or other cardiac surgery procedures (n=95). Nasal cultures were taken preoperatively from every patient, as well as cultures of the wound during surgery and when dressings were changed thereafter. In addition, nasal cultures were taken from all the medical and nursing staff. To differentiate endogenous and exogenous infection pathways, DNA fingerprint analysis was performed. RESULTS A total of 38 patients (10.1%) developed a wound infection, in 14 patients this happened to be a deep wound infection, in 24 patients a superficial one. Five sternal wound infections were associated with mediastinitis (1.3%). The occurrence of a wound infection overall resulted in prolonged hospitalization (29.4+/-24 vs. 11.9+/-6.9 days, P=0.001), but not in increased hospital mortality (4.4% vs. 3.9%). Obesity, diabetes mellitus and nasal carriage of Staphylococcus aureus proved to be independent risk factors with an odds ratio of 2.07, 2.26 and 2.28, respectively. In all but one of the sternal colonizations with S. aureus, DNA fingerprint analysis demonstrated an identical pattern of S. aureus from the patients nose and sternum, indicating an endogenous infection pathway. CONCLUSIONS The determination of the endogenous pathway for severe wound infection makes prevention possible by means of preoperative local S. aureus eradication.

Molecular probes for the detection of pathogenic fungi in the presence of human tissue

Four primer systems, amplifying fragments of the gene coding for the small ribosomal subunit (18S rRNA) were characterised with pure cultures of 65 medically relevant fungal species plus two mushrooms. A primer cocktail (TR1/CA1-TR2/AF2) amplified 59 of 67 fungal species; the universal fungal primer 1 (UF1) in combination with the eukaryotic primers S3 or EU1 amplified 64 and 65 of 67 fungal species, respectively. The design of an additional primer (RZY1) enabled the amplification of the missing members of the zygomycetes. The primer systems amplified all the medically relevant fungi tested. These included eight Candida spp. and seven other yeast species, 13 dermatophytes, 32 moulds (including six zygomycetes and five dimorphic fungi) and two mushrooms. Eleven controls including DNA from Schistosoma mansoni, Escherichia coli, Mycobacterium tuberculosis and man were not amplified. The oligonucleotide CA hybridised with C. albicans, C. tropicalis and C. parapsilosis; the oligonucleotide TR hybridised with the 13 dermatophytes; the oligonucleotide AF hybridised with Aspergillus fumigatus, A. flavus, A. terreus, A. nidulans, A. versicolor, A. tamarii, A. clavatus, A. fischeri, but not with A. niger or A. versicolor; and the oligonucleotide HC hybridised with three varieties of Histoplasma capsulatum. These oligonucleotides did not hybridise with the other fungi nor the controls. The specificity of the newly designed primer systems was confirmed by selective amplification of fungal DNA from human lung tissue spiked with fungal biomass and from vitrectomy fluid of a patient with candida endophthalmitis.

Evaluation of eight antibody tests and one antigen test for the diagnosis of invasive aspergillosis.

Summary. Eight Aspergillus antibody detection assays — three indirect haemagglutination assays (IHA‐LD, IHA‐Roche, IHA‐Fumouze), three enzyme immunoassays (EIA‐IgG, EIA‐IgM, EIA‐IgA, DDV) and two complement fixation tests (CF‐metabolic and CF‐somatic, Virion — and one latex agglutination test (LAT) for Aspergillus galac‐tomannan antigen detection (Sanofi Pasteur) were evaluated in 14 patients with proven invasive aspergillosis (a total of 47 serum samples and one cerebrospinal fluid sample) and in 68 selected control individuals (one selected serum sample each). For the antibody tests, sensitivity ranged from 14% to 36% and specificity from 72% to 99%. The antigen detection test had a sensitivity of 36% and a specificity of 100%. Currently commercially available antibody detection assays for the serodiagnosis of invasive aspergillosis are inadequate. The antigen detection test appears to be highly specific, but lacks sufficient sensitivity.

The role of surface disinfection in infection prevention.

Background: The Rudolf Schuelke Foundation addresses topics related to hygiene, infection prevention and public health. In this context a panel of scientists from various European countries discussed “The Role of Surface Disinfection in Infection Prevention”. The most important findings and conclusions of this meeting are summarised in the present consensus paper. Aim: Although the relevance of surface disinfection is increasingly being accepted, there are still a number of issues which remain controversial. In particular, the following topics were addressed: Transferral of microbes from surface to patients as a cause of infection, requirements for surface disinfectants, biocidal resistance and toxicity, future challenges. Methods and findings: After discussion and review of current scientific literature the authors agreed that contaminated surfaces contribute to the transmission of pathogens and may thus pose an infection hazard. Targeted surface disinfection based on a risk profile is seen as an indispensable constituent in a multibarrier approach of universal infection control precautions. Resistance and cross-resistance depend on the disinfectant agent as well as on the microbial species. Prudent implementation of surface disinfection regimens tested to be effective can prevent or minimize adverse effects. Conclusions: Disinfection must be viewed as a holistic process. There is a need for defining standard principles for cleaning and disinfection, for ensuring compliance with these principles by measures such as written standard operating procedures, adequate training and suitable audit systems. Also, test procedures must be set up in order to demonstrate the efficacy of disinfectants including new application methods such as pre-soaked wipes for surface disinfection.

Implementation of Practice Guidelines for Antifungal Therapy in a Surgical Intensive Care Unit and Its Impact on Use and Costs

Background: Considering the complexity of diagnosis, high costs of therapy and high morbidity and mortality of systemic fungal infections, antifungal therapy of intensive care patients should follow clearly defined guidelines. We outline the impact of a standardised practice of antifungal treatment in an interdisciplinary surgical intensive care unit of a university hospital. Methods: Therapy was intended to be optimised by implementation of standardised practice guidelines supported by the clinical pharmacist. Costs for antifungal agents during a period of 18 months before and after implementation of the practice guidelines were compared, respectively. Results: The intervention was associated with a significant decrease in use of antifungal agents. Analysis of data revealed a reduction in costs by 50%. This could substantially be attributed to the implementation of the practice guidelines. Conclusion: The implementation of standardised practice guidelines for antifungal therapy in intensive care units decreased the use of selected antifungal agents and resulted in substantial reduction in expenditure on antifungal agents.

Comparative Investigations of Klebsiella Species of Clinical Origin: Plasmid Patterns, Biochemical Reactions, Antibiotic Resistances and Serotypes

A total of 124 K. pneumoniae and 52 K. oxytoca isolates obtained from clinical specimens was investigated for plasmid patterns, biochemical reactions, antibiotic resistances and serotypes regarding to the distribution and relationships of these characters. A great diversity of plasmid patterns, bio/serotypes and resistance patterns was revealed. About 90% of strains contained plasmid DNA and up to seven plasmid bands per isolate could be shown. For K. pneumoniae, serotype 7 and for K. oxytoca, type 55 were most common. In general, little difference between both species was found and characters were similarly distributed. With respect to the site of isolation, serotype 7 was predominating in K. pneumoniae strains from the respiratory tract. Highly multiple-resistant organism were found in the largest number in specimens from the urogenital tract, in the lowest in specimens from wounds. Extensive statistical analyses did not detect any relationship among the characters investigated.

Survey of attitudes towards curriculum reforms among medical teachers in different socio-economic and cultural environments

Background: Curriculum reforms in medical schools require cultural and conceptual changes from the faculty. Aims and Methods: We assessed attitudes towards curriculum reforms in different academic, economic, and social environments among 776 teachers from 2 Western European medical schools (Belgium and Denmark) and 7 medical schools in 3 countries in post-communist transition (Croatia, Slovenia, Bosnia and Herzegovina). The survey included a 5-point Likert-type scale on attitudes towards reforms in general and towards reforms of medical curriculum (10 items each). Results: Teaching staff from medical schools in Bosnia and Herzegovina had a more positive attitude towards reforms of medical curriculum (mean score 36.8 out of maximum 50 [95% CI 36.1 to 37.3]) than those from medical schools in Croatia or Slovenia (30.7 [29.8 to 31.6]) or Western Europe (27.7 [27.1 to 28.3]) (P < 0.001, ANOVA). Significant predictors of positive attitudes towards medical curriculum reform in post-communist transition countries, but not in Western European schools, was younger age, as well as female gender in Bosnia and Herzegovina. Conclusions: Factors influencing faculty attitudes may not be easy to identify and may be specific for different settings. Their identification and management is necessary for producing sustainable curriculum reform.

Autovaccination of dairy cows to treat post partum metritis caused by Actinomyces pyogenes

Autovaccines are therapeutic vaccines manufactured from a disease causing micro-organism for individual treatment of patients, animals, or sometimes herds to treat chronic or recurrent infections. Despite the common use of autovaccines in veterinary medicine, their mechanism of action, i.e. the immunologic effector mechanism activated after administration, has never been investigated. Here we present data concerning the use of autovaccines to treat metritis infection in a group of dairy cows. Following autovaccination we observed a significant decrease in CD4+ cells paralleled by an increase in T-cells expressing the gammadelta-T-cell receptor (gammadelta-TCR) in the peripheral blood of the treated animals. Lymphocyte proliferation assays showed an initial increase in antigen-specific responsiveness followed by a decrease in this responsiveness during autovaccination treatment. We therefore conclude that administration of an autovaccine leads to the activation of immunologic effector mechanisms which contribute to recovery of the diseased animals.

Western blot analysis of the immune response to Candida albicans antigens in 391 long-term intensive care patients.

Summary. The aim of this study was to determine, using Western blot, the prevalence of anti‐Candida albicans antibodies in long‐term intensive care patients and to characterize specific immune responses that may only occur in patients with invasive candidosis. A total of 1751 serum samples from 391 patients of a German multicentre study, which was designed to determine the incidence of systemic candidosis, was examined. Significantly enhanced antibody production against specific antigens was observed in several subgroups of patients, i.e. those with underlying disease of the pancreas (29 kDa, P=0.006), cholecystolithiasis (47 kDa, P=0.029), gastrointestinal tract disease (47 kDa, P=0.03), steroid therapy (58 kDa, P=0.02), thrush (58 kDa, P=0.032), urogenital infection (58 kDa, P=0.034), Candida antigen titre 1:4 (58 kDa, P=0.002) and positive fungal culture (36 kDa, P=0.033) and those who had died (36 kDa, P=0.011). In contrast to earlier publications, an immune response against the 29 and 47 kDa antigens was relatively common among long‐term intensive care patients (37% and 70% antibody positive respectively). A single antigen that provided satisfactory sensitivity and specificity for the discrimination between fungal infection and no fungal infection or between superficial and invasive fungal infection was not identified in this study.