Peter Heeg

Infectivity of prion protein bound to stainless steel wires: a model for testing decontamination procedures for transmissible spongiform encephalopathies

OBJECTIVES To establish an animal model to study transmissible spongiform encephalopathy using hamsters and steel wires contaminated with infectious brain materials as transfer vehicles, and, based on this model, to test decontamination procedures against the infectious prion proteins on the steel wires as a near real situation bioassay. DESIGN Infectious brain materials were given to healthy hamsters intracerebrally either as a suspension or as dried materials on the surface of steel wires. The animals were observed for 18 months. During this period, animals showing definitive clinical signs were euthanized. Decontamination studies were performed by reprocessing contaminated steel wires with different disinfection agents and procedures before implantation. RESULTS Pathological prion proteins were able to bind to the steel wires and caused disease after the contaminated wires were implanted in the brains of hamsters. When the contaminated wires were treated with different reprocessing procedures before implantation, infectivity was reduced, which was manifested directly by prolonged survival time of the test animals. These results show that this model can be used as a bioassay to validate reprocessing procedures for surgical instruments. CONCLUSIONS At the time of submission of this article, only the group of hamsters incubated with wires reprocessed with an alkaline detergent, followed by sterilization with a modified cycle in a hydrogen peroxide gas plasma sterilizer (4 injections), showed no clinical signs of disease and remained alive. Two animals from the group receiving sodium hydroxide followed by autoclaving (at 134 degrees C for 18 minutes) died. Furthermore, the tested enzymatic cleaning agent seemed to have no positive effect.

Decontaminated Single-Use Devices: An Oxymoron That May Be Placing Patients at Risk for Cross-Contamination

OBJECTIVE To determine whether reprocessed single-use devices would meet regulatory standards for sterility and meet the same materials standards as a new device. DESIGN The study included single-use and reusable biopsy forceps and papillotomes and a reusable stone retrieval basket. The suitability of these devices for cleaning and disinfection or sterilization was examined. METHODS Testing of cleanability was conducted on devices contaminated with technetium 99-radiolabeled human blood. Instruments were cleaned using hospital recommended practices for manual cleaning. Gamma counts per second were determined before and after cleaning to localize contaminants, which were additionally visualized using light and scanning electron microscopy. X-ray photoelectron spectroscopy was used to quantify contamination elements on the materials tested. Residual bioburden testing on instruments contaminated with microorganisms suspended in coagulable sheep blood was carried out to establish the efficacy of disinfection and sterilization. RESULTS All devices remained contaminated after cleaning, but single-use devices and the stone basket tended to be more heavily contaminated than reusable forceps and papillotomes. Cleaning procedures facilitated distribution of contaminants further into the lumens of the disposable forceps. Decreased concentrations of silicon and increased concentrations of carbon and nitrogen suggested that layers of silicon lubricant had been removed and contaminants were organic material. Reusable devices were effectively disinfected, but single-use devices were not. Sterilization could not eliminate the challenge microorganisms completely. CONCLUSIONS None of the reprocessed single-use instruments were effectively cleaned, disinfected, or sterilized. This condition may provide an opportunity for the viability of nonresistant or nosocomial organisms and viruses. Additionally, reprocessing procedures may result in material destruction of fragile devices. Cost-saving initiatives that have inspired reprocessing of single-use devices, despite the absence of data establishing the efficacy of decontamination and the durability of materials throughout reprocessing, should be pushed into the background.

Increased interleukin-6 in collected drainage blood after total knee arthroplasty: An association with febrile reactions during retransfusion

We determined interleukin-6 (IL-6) concentrations in collected shed drainage blood intended for retransfusion in a prospective study in 81 patients after total knee replacement. We found large increases in IL-6 levels, averaging 6.5 (SD 3.9) ng/mL, in shed blood collected in the first 6 postoperative hours. 3 patients had febrile reactions after collected blood was retransfused. The IL-6 levels in the drainage blood of these patients were very high (9.6-13.4 ng/mL). In the blood collected after 6 hours, IL-6 concentrations increased to 47 (SD 33) ng/mL (p < 0.001). These results suggest a relation between increased interleukin-6 concentrations in shed drainage blood and the occurrence of febrile reactions after retransfusion of such blood.

Two episodes of vancomycin-resistant Enterococcus faecium outbreaks caused by two genetically different clones in a newborn intensive care unit.

In 2001 two outbreak episodes (January-March and June-July) caused by vancomycin-resistant E. faecium (VRE) of the VanA-type were observed at a neonatal intensive care unit (NICU) of a university hospital in south-west Germany. To identify the initial source and the route of transmission environmental samples were examined as well as stool samples from patients and the staff. VRE was not found in environmental samples. However, stool samples from 24 hospitalised children tested positive and bacterial clonality was assessed by Sma1-based macro restriction analysis. Furthermore, esp gene and vancomycin resistance gene carriage were examined as well as bacteriocin production. PCR analysis showed that all 24 isolates carried vanA gene cluster, encoding resistance to vancomycin and teicoplanin. However, five of the vanA-positive isolates were resistant to vancomycin but not to teicoplanin. Only these five isolates produced bacteriocin, but in none of the isolates esp gene was detected. PFGE revealed that both outbreaks were caused by two different clones. The patient initiating the first episode, was identified whereas the origin of the second episode remained unknown. From one of the 40 staff stool samples VRE was isolated. This strain was related to the clone of the summer outbreak. In conclusion there were two independent episodes of self limiting VRE outbreaks and transmission on the ward is highly probable.

Specific hygiene issues relating to reprocessing and reuse of single-use devices for laparoscopic surgery

Objective: To determine whether reprocessed single-use devices (SUD) would (1) meet regulatory standards for sterility, and (2) meet the same material standards as new devices or if they pose an infection risk to other patients. Design: The study included in the first stage single-use laparoscopic dissection devices and in the second stage a variety of clinically used and reprocessed SUDs. The suitability of these devices for cleaning, disinfection, and sterilization was examined.Methods: Testing of cleanability was conducted on devices contaminated with radioactively labeled blood. Instruments were cleaned using hospital recommended practices. Gamma counts/second were determined before and after cleaning to localize contaminants, which were additionally visualized using light and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) was used to quantify contamination elements on the materials tested. Residual bioburden testing on instruments contaminated with microorganisms suspended in blood prior to reprocessing was carried out to establish the efficacy of disinfection and sterilization.Results: During the first stage of the study all devices remained contaminated after cleaning, but were effectively disinfected. Sterilization could not eliminate the challenge microorganisms completely. The findings during the second stage — examination of clinically used devices — were as follows: 11% of the sterile packages were damaged; 33% of the devices were incomplete and parts were missing; 54% did not meet the criteria for functionality; light microscopy, SEM, and XPS showed contamination on the outside and inside of all devices. Of the tested SUDs, 40% remained unsterile following resterilization.Conclusions: None of the reprocessed SUDs were effectively cleaned or sterilized. This may provide an opportunity for survival and growth of non-resistant or nosocomial organisms and viruses. The use of such inadequately reprocessed SUDs increases the risk for the patient, and can lead to nosocomial infection and to legal consequences for the health care facility.

Vancomycin-Resistant Enterococci Outbreak, Germany, and Calculation of Outbreak Start

On the basis of a large outbreak of vancomycin-resistant Enterococcus faecium in a German university hospital, we estimated costs (≈1 million Euros) that could have been avoided by early detection of the imminent outbreak. For this purpose, we demonstrate an easy-to-use statistical method.

Microbiological, microstructure, and material science examinations of reprocessed Combitubes® after multiple reuse

UNLABELLED Reprocessing (repeated cleaning, disinfection, and sterilization) and reuse of single-use medical devices has been performed safely with some devices. The aim of our study was to analyze whether reprocessing of the Combitubes (Kendall-Sheridan, Argyll, NY) airway device, used for emergency endotracheal intubation and difficult airway management, is possible and can be performed appropriately and safely. Microbiological, microstructure, and material science examinations were performed with unused, as well as multiple reused and reprocessed Combitubes. The reprocessing procedure consisted of a cleaning, a disinfection, a final inspection, and a sterilization. Microbiological examinations of multiple reused and reprocessed Combitubes found no test organisms in quantitative cultures. A microbial reduction between four and five log levels compared with nonreprocessed tubes was found. Microstructure analysis for the examination of topographical alterations and changes in the chemical composition of the surface demonstrated nonsignificant alterations between new and reprocessed medical devices. In material science examinations, cuff burst pressures were not different between unused and multiple reprocessed Combitubes. The results of all examinations proved that the decontamination process is adequately effective, and that no significant superficial alterations are generated by the multiple reuse and reprocessing of the Combitubes. To assure uniformly good results, a quality management system must be established and only validated methods should be used. IMPLICATIONS Reprocessing of single-use medical devices offers the opportunity of significant savings and is already performed with some devices. Microbiological, microstructure, and material science examinations proved that reprocessing of multiple reused Combitubes (Kendall-Sheridan, Argyll, NY), mainly used for emergency airway management, is possible and safe.

Surveillance of Pseudomonas aeruginosa-isolates in a neonatal intensive care unit over a one year-period.

Outbreaks of gram-negative bacteria such as Pseudomonas aeruginosa in neonatal intensive care units (NICU) can be life-threatening to pre-term infants, which are highly susceptible to serious infections with bacteria. Forty-two ventilated neonates in the NICU of the University Childrens Hospital of Tuebingen were found to be colonized (n = 40) or infected (n = 2) with P. aeruginosa within a sampling period of one year. To investigate the colonization patterns and identify potential outbreak sources, epidemiological investigations, environmental surveillance and typing by serotyping and pulsed-field gel electrophoresis of the recovered isolates were performed. The investigation demonstrated a genetically related cluster of P. aeruginosa isolates during the surveillance period in 39 neonates and a second cluster at the end of the period in two neonates. A third strain representing a genetically distinct group was found in only one patient. Environmental investigations demonstrated the presence of P. aeruginosa in the ventilation equipment of 22 patients: binasal prongs (n = 22), water reservoir (n = 9), and heater (n = 1). In one case, P. aeruginosa was found in breast milk. Other environmental investigations revealed no P. aeruginosa. Although no evidence for a unique source was found, a series of intervention steps were initiated by the NICU personnel, medical microbiologists and infection control experts. The intervention steps included reinforced training of health care staff and a change from chemical to thermal disinfection of binasal prongs. Implementation of these measurements successfully stopped the recurrent occurrence of P. aeruginosa colonization.

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.

Disinfection of pumice

Pumice is a potential source of infection for the dental technician and of cross-contamination between different dentures and patients. In this study, the number of microorganisms in two different combinations of pumice and disinfectant was compared with a conventional mixture of pumice and water. The results revealed that under practical conditions the mix of Steribim (pumice containing benzoic acid added by the manufacturer) with water reduced the number of bacteria by 99% compared with a mix of a conventional pumice and water. The addition of an antiseptic product that contained octenidine as active agent to conventional pumice reduced the number of microorganisms by 99.999%.