Jürgen Gebel

Long-term effects of disinfectants on the community composition of drinking water biofilms

Numerous investigations have demonstrated efficiencies of different disinfection methods, but until now only little is known about long-term effects on community compositions of drinking water biofilms. Changes in the community structure, especially regrowth of hygienically relevant microorganisms could be critical for the drinking water quality. In this study the long-term effect of disinfection methods on biofilm communities in drinking water systems was analysed. Old drinking water biofilms grown in silicone tubes were exposed to different preparations of disinfectants (free chlorine, chlorine dioxide, hydrogen peroxide combined with fruit acid, silver and silver with peracetic acid, respectively) and subsequently further exposed in the original drinking water. The comparison of the treated and regrown biofilm populations with untreated ones by the DNA-fingerprinting method denaturing gradient gel electrophoresis (DGGE) revealed a considerable population shift caused by the disinfectants. The disinfection methods induced a selection pressure on the biofilm populations depending on the composition and concentrations. The similarities between the treated and untreated biofilms were generally low. Compared to preparations with peracetic acid the disinfection with hydrogen peroxide and silver resulted in higher similarities of the treated and untreated biofilms, but the microbial diversity increased. It can be concluded that the disinfectants have a major impact on the drinking water biofilm communities and that possibly the intervention selects persisters and microorganisms, which can live on the residuals of the dead biofilm cells. For the evaluation of the efficiency of disinfection methods in drinking water installations it is necessary not only to consider reduction of certain bacteria but also to pay attention to the biofilm community.

Detection of Helicobacter pylori in biofilms by real-time PCR

Helicobacter pylori is a cause of peptic ulcer disease and a causative agent of gastric cancer. Currently, a possible waterborne route of transmission or a possible survival in drinking water biofilms is discussed. H. pylori, like many other bacterial strains, has the ability to enter the viable but nonculturable state (vbnc) in case of unfavorable conditions. Therefore it is necessary to develop new analysis tools for vbnc bacteria. We established a fast and reliable method to detect H. pylori in drinking water biofilms by quantitative real-time PCR which makes it redundant to use difficult cultivation methods for nonculturable bacteria. With this method it was possible to identify water biofilms as a niche for H. pylori. The real-time PCR analysis targets the ureA subunit of the Helicobacter pylori urea gene which showed high specificity and sensitivity. The quantitative real-time PCR was used to detect H. pylori in biofilms of different age, unspiked and spiked with predetermined levels of cells. The drinking water biofilms were generated in a silicone-tube model. The DNA-sequences for probe and primers showed no cross-homologies to other related bacteria and it was possible to detect less than 10 genomic units of H. pylori. This novel method is a useful tool for a fast screening of drinking water biofilms for H. pylori. The results suggest that drinking water biofilms may act as a reservoir for H. pylori which raises new concerns about the role of biofilms as vectors for pathogens like Helicobacter pylori.

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.

Wasser als Infektionsquelle in medizinischen Einrichtungen, Prävention und Kontrolle

ZusammenfassungAktuelle epidemiologische und hygienisch-mikrobiologische Untersuchungen zeigen, dass dem Hausinstallationssystem in medizinischen Einrichtungen als Infektionsreservoir für nosokomiale Infektionen eine bislang erheblich unterschätzte Bedeutung zukommt. Nach Einführung spezifischer Präventionsmaßnahmen konnte das Risiko einer Übertragung relevanter nosokomialer Infektionserreger wie Legionellen und Pseudomonaden deutlich reduziert werden. Im vorliegenden Beitrag werden Besonderheiten der Wasseranwendung in medizinischen Einrichtungen, die besondere Vulnerabilität bestimmter Patienten, die wichtigsten wasserassoziierten Erreger und deren ökologische Besonderheiten, rechtliche Aspekte und die wichtigsten Maßnahmen zur Prävention und Kontrolle behandelt.AbstractNew epidemiological and microbiological investigations using molecular typing methods to link patient and environmental strains demonstrate a strong association between water-borne pathogens and nosocomial infections. Avoiding patient exposure to these pathogens results in a decreased incidence of water-borne nosocomial infections. There remains a tremendous potential to reduce hospital acquired infections previously viewed as inevitable and unavoidable through intervention and preventive measures. The characteristics of water application in health care facilities, the vulnerability of patients, the spectrum of relevant pathogens and their ecologic aspects, legal issues and important measures for prevention and control are discussed.

Ultra- and microfiltration pilot plant investigations to treat reservoir water☆

Currently the IWW-Rheinisch-Westfaelisches Institut fuer Wasserforschung gemeinnuetzige GmbH, an Institute at the University of Duisburg, the Institute of Hygiene of the University of Bonn and the Wasserwerk des Kreises Aachen (WdKA) are realising a project supported by the German Federal Ministry for Education, Science, Research and Technology (BMBF). This project is to investigate whether membrane filtration (micro-or ultrafiltration) is able to enhance the particle removal efficiency of an existing drinking water treatment plant. The first step of the total investigation programme was to operate three different pilot plants in parallel with a capacity of about 10 m3/h each. This paper presents results concerning the pilot plant investigations.

[Water as a reservoir for nosocomial infections in health care facilities, prevention and control].

ZusammenfassungAktuelle epidemiologische und hygienisch-mikrobiologische Untersuchungen zeigen, dass dem Hausinstallationssystem in medizinischen Einrichtungen als Infektionsreservoir für nosokomiale Infektionen eine bislang erheblich unterschätzte Bedeutung zukommt. Nach Einführung spezifischer Präventionsmaßnahmen konnte das Risiko einer Übertragung relevanter nosokomialer Infektionserreger wie Legionellen und Pseudomonaden deutlich reduziert werden. Im vorliegenden Beitrag werden Besonderheiten der Wasseranwendung in medizinischen Einrichtungen, die besondere Vulnerabilität bestimmter Patienten, die wichtigsten wasserassoziierten Erreger und deren ökologische Besonderheiten, rechtliche Aspekte und die wichtigsten Maßnahmen zur Prävention und Kontrolle behandelt.AbstractNew epidemiological and microbiological investigations using molecular typing methods to link patient and environmental strains demonstrate a strong association between water-borne pathogens and nosocomial infections. Avoiding patient exposure to these pathogens results in a decreased incidence of water-borne nosocomial infections. There remains a tremendous potential to reduce hospital acquired infections previously viewed as inevitable and unavoidable through intervention and preventive measures. The characteristics of water application in health care facilities, the vulnerability of patients, the spectrum of relevant pathogens and their ecologic aspects, legal issues and important measures for prevention and control are discussed.

Antibiotic resistance: What is so special about multidrug-resistant Gram-negative bacteria?

In the past years infections caused by multidrug-resistant Gram-negative bacteria have dramatically increased in all parts of the world. This consensus paper is based on presentations, subsequent discussions and an appraisal of current literature by a panel of international experts invited by the Rudolf Schülke Stiftung, Hamburg. It deals with the epidemiology and the inherent properties of Gram-negative bacteria, elucidating the patterns of the spread of antibiotic resistance, highlighting reservoirs as well as transmission pathways and risk factors for infection, mortality, treatment and prevention options as well as the consequences of their prevalence in livestock. Following a global, One Health approach and based on the evaluation of the existing knowledge about these pathogens, this paper gives recommendations for prevention and infection control measures as well as proposals for various target groups to tackle the threats posed by Gram-negative bacteria and prevent the spread and emergence of new antibiotic resistances.

Environmental resistance, disinfection, and sterilization of poxviruses

The virion of a poxvirus is an enveloped particle that differs significantly from other enveloped viruses. Apart from DNA, proteins and phospholipids, poxvirus virions also contain carbohydrates. They show a high environmental stability and remain contagious over a period of several months in an ambient environment. Poxviruses show an extraordinary high resistance to drying, which is further enhanced by materials in which they are released into the environment (e.g., dermal crusts, serum, blood residues and other excretions). Dried Vaccinia virus can be stored at 4°C over a period of more than 35 weeks without any loss of infectivity. Frozen in buffer at -20°C, a titer reduction of only 3 log-steps is observed within 15 years. In general, virus isolated from patients and/or environment is more resistant to environmental conditions than virus deriving from cell cultures. In addition, poxviruses show a high stability towards different pH values. Due to their low lipid content, they are less sensitive to organic solvents/disinfectants compared to other enveloped viruses. This is the reason for the considerably higher resistance of poxviruses to diethylether in comparison to other enveloped viruses. Despite all of these aspects, poxviruses are highly sensitive to all common approved disinfection regimens. Cell-bound poxvirus may show a higher stability than cell-free virus. This phenomenon is not observed if quaternary ammonium compounds are used. Due to the possible renewed importance of smallpox, e.g., in case of abuse in biological warfare, but also because of the impact of poxviruses in veterinary medicine, representatives of the poxvirus family have been chosen to test the efficacy of common disinfectants. The common sterilization procedures - thermal, chemical, an/or radiation - are usually effective against poxviruses.

Portable UV light as an alternative for decontamination.

We evaluated the capability of a commercially available hand-held device that emits ultraviolet (UV) light to disinfect plain surfaces. Eight bacterial species were tested, including Clostridium difficile ribotype 027 and 3 other spore-forming species. Even bacterial spores could be successfully inactivated within a few seconds of irradiation. UV light may provide an alternative for the decontamination of medical products, such as mobile phones or tablet computers, that cannot be treated otherwise.

Infektionsrisiken im häuslichen Umfeld

ZusammenfassungIn den letzten Jahrzehnten spielten Infektionsrisiken außerhalb medizinischer Einrichtungen in der öffentlichen Risikowahrnehmung nur eine geringe Rolle. Dies trifft insbesondere für den häuslichen Bereich zu. Jedoch haben sich in diesem Zeitraum erhebliche soziodemographische, gesundheitspolitische und technologische Veränderungen vollzogen. So werden in Deutschland immer mehr pflegebedürftige Menschen im Familienhaushalt versorgt. Derzeit liegt diese Zahl bei ca. 1,4 Millionen. Zudem hat die epidemiologische Bedeutung relevanter Krankheitserreger, wie zum Beispiel von Campylobacter oder Noroviren, erheblich zugenommen. Diese Entwicklungen er fordern eine Neubewertung der Infektionsrisiken außerhalb medizinischer Einrichtungen und einen Konsens über notwendige Hygienestrategien. Auf diese Aspekte soll im vorliegenden Beitrag ausführlich eingegangen werden.AbstractWithin the last two decades risks posed by infectious diseases outside of hospitals and nursing homes had no high significance in the public perception. The home environment is regarded as a save shelter from infectious risks. In the mean time there have been dramatic socio-demographic, health policy and technological changes which have increased infectious risks outside medical facilities. In Germany up to 1.4 million people with multiple morbidities are nursed at home. Technological changes with the aim to protect the environment, like reduction of water temperature and water volumes in washing processes has lowered the efficacy to control pathogens. Thus it is time to revise the process of risk assessment in which not only aspects of environmental protection but also those of health protection must be taken into account. The article gives an overview of new risks and epidemiological changes and discusses the necessity of a new risk assessment and risk management approach which hopefully will lead to a changing paradigm.Within the last two decades risks posed by infectious diseases outside of hospitals and nursing homes had no high significance in the public perception. The home environment is regarded as a save shelter from infectious risks. In the mean time there have been dramatic socio-demographic, health policy and technological changes which have increased infectious risks outside medical facilities. In Germany up to 1.4 million people with multiple morbidities are nursed at home. Technological changes with the aim to protect the environment, like reduction of water temperature and water volumes in washing processes has lowered the efficacy to control pathogens. Thus it is time to revise the process of risk assessment in which not only aspects of environmental protection but also those of health protection must be taken into account. The article gives an overview of new risks and epidemiological changes and discusses the necessity of a new risk assessment and risk management approach which hopefully will lead to a changing paradigm.