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Prevention of Cross-Infection in Cystic Fibrosis
How relatively simple initiatives have improved the prognosis for people with CF in DenmarkBy Claus Moser, MD phD and Niels Hoiby, MD The majority of adult patients with cystic fibrosis (CF) have chronic bacterial lung infection. The most common pathogens in CF around the world are:
Prevalence (or the number of people infected) with these bacteria, varies greatly between different CF centers around the world. Dr. Claus Moser Once the chronic infection is established, it can only rarely be eradicated from the lungs of CF patients, due to the ability of the bacteria to form protected microcolonies called bio-films. Some of the bacteria may become very slimy (mucoid) making them even more difficult to treat. The bio-film mode of growth, and the propensity to become mucoid, protects the bacteria from the immune system of the CF patient and the antibiotics given to the patient to treat the infection. Furthermore, it is now widely accepted that the ongoing inflammatory response to the chronic lung infections, is responsible for damage of the lung tissue and loss of lung function observed in patients with CF.
The major contributor to prolonged life expectancy in recent years, and markedly improved prognoses in CF, is improved treatment of chronic lung infections. Other initiatives such as prompt treatment of diabetes, physiotherapy and treatment with DNase (Pulmozyme) also add to the increased quality of life for CF patients. If CF patients could escape the chronic lung infection or at least delay the onset of chronic infection as long as possible, this would dramatically add to their life expectancy. This article describes how relatively simple initiatives implemented in Denmark have improved the prognosis in patients with CE Mode of acquisitionTo avoid lung infection, the mode of acquisition (how you get infected) has to be taken into consideration. Since this varies with the kind of organism that is present, we will describe the mode of acquisition of the three most common and most feared infections in people with CE Acquisition of Pseudomonas aeruginosaIn general, P aeruginosa can be acquired from both the environment and from infected patients. In nature, .P aeruginosa is present in fresh water and soil contaminated by humans and animals. Other environmental sources are inadequately chlorinated swimming pools and whirlpools. More potential sources of P aeruginosa have also been recognized in intensive care units, dentists, sinks, toys and hand-soaps in CF wards. A possible explanation for the relatively high presence of P. aeruginosa in the CF wards is that P. aeruginosa in sputum can survive for up to 8 days on dry surfaces. Therefore, hospital locations and the immediate surroundings of CF patients must be considered contaminated until they are properly cleaned, if chronically infected patients have been attending. Dr Niels Hoibv "The most important evidence of cross infection is the dramatic reduction in Pseudomonas aeruginosa incidence which has resulted from segregation of non- infected from chronically infected patients" Cross-infection with P. aeruginosa from other patients is considered likely due to the fact that siblings often carry the same strain and the transmission of specific strains during social events like summer and winter camps from chronically infected to previously uninfected patients. The epidemic spread of antibiotic resistant strains and the relationship between the increase in the number of chronically infected patients and time spent in the CF center, also points to cross-infection between patients. The most important evidence of cross infection is the dramatic reduction in P. aeruginosa incidence, which has resulted from segregation of non-infected from chronically infected patients. Although not the major topic of this article, it should be mentioned that the early aggressive treatment upon isolation of P. aeruginosa has significantly reduced numbers of chronically infected CF patients, further resulting in decreased transmission of Acquisition of Staphylococcus aureusIn contrast to P aeruginosa, a relatively high frequency, up to 10-30% of healthy carriers of S. aureus can be observed, and the most important route of transmission to CF patients is thought to be from healthy carriers or non-CF patients, although transmission of methicillin resistant S. aureus between CF patients has been reported. The major mode of transmission is believed to be by hand contact. In the pre-antibiotic era the majority of patients with CF died before 10 years of age, and most patients actually succumbed due to S. auretis lung infections. Regular microbiological examinations followed by aggressive antibiotic treatment can possibly reduce the prevalence of CF patients with chronic S. aureus lung infection below 10%. Furthermore, the risk of acquiring methicillin resistant S. aureus in the CF center is reduced in this way. "An important reason seems to be cross-injection, and there are several reports on spread among CF patients, including by social Acquisition of Burkholderia cepacia complexThe B. cepacia complex consists of different so-called genomovars of which some occasionally can lead to chronic lung infections in CF patients. The most common is B. cenocepacia and B. multivorans but in addition B. cepacia, B. vietnamensis and B. gladioli have also been recognized as CF pathogens. B. cepacia complex is responsible for different clinical patterns of lung infections, the most serious being the B. cepacia syndrome. The B. cepacia complex is a common part of the microflora in soil and can act as a plant pathogen. In addition, the B. cepacia complex has been isolated from food stores, salad bars, and greenhouses, and it may be more common in rural than in urban environments. Even though the overall prevalence of B. cepacia complex in CF centers is relatively low, some centers have higher prevalence (e.g. over 31 % of CF patients in Toronto have been reported to be diagnosed with B. cepacia complex)2. An important reason seems to be cross-infection, and there are several reports of spread among CF patients, including by social contact outside the CF centers. A famous outbreak was reported from UK in 1990-92, where the index patients acquired the B. cepacia complex strain in Canada during a summer camp, and subsequently spread it while attending weekly fitness classes. Intensive investigations have identified routes of transmission by direct contact between infected and non-infected patients, as well as through contaminated equipment, and an important observation is that CF centers which do not segregate these patients have had ongoing transmission of B. cepacia complex. Control of cross-infection by interventionIntervention by cohorting of CF patients and improved hygiene precautions were implemented in Denmark in 1981, in order to avoid transmission of pathogens from infected to non-infected CF patients by physical contact or coughing at close range2. Cohorting means dividing CF patients into separate subgroups according to their infection status, and also segregating the patients geographically (different wards or rooms) and/or segregating the patients by time (different days). The "being infective" status is based on bacteriological findings, and on whether the patient is intermittently infected (pathogen is eradicated at later controls,- and the patient does not develop an immune response) or chronically infected (the pathogen is currently being isolated over a 6 month period and/or the patient does develop an immune response). Seeing the patients frequently allows rapid detection of infection, giving the opportunity for early aggressive treatment and thereby reducing the risk for transmission of the pathogen. Cohort segregation (patients with the same bacterial species) inhibits transmission of the bacteria by physical contact or coughing to unaffected persons. Indeed, the mean time from first isolation of P aeruginosa to onset of chronic P aeruginosa lung infection increased from 1 to 3 years after implementation of cohorting of CF patients in Denmark. The CF patients in the Copenhagen CF center in Denmark are segregated based on identification of the following bacteria from the lower airways of the patients:
Five wards are ideal but not possible in most hospitals. Patients in cohort 2 can be hospitalized with patients from cohort 1, however in different rooms, since intermittent colonized patients have low number of bacteria and often do not produce sputum. Cohort 1) and 2) can also been seen in out-patient clinic on the same days, since cohort 2) is either free of P. aeruginosa in the last sputum sample taken 4 weeks earlier or on anti- P aeruginosa treatment. Cohorts 3) and 4) are seen on separate days and all clinic rooms are cleaned using hypochlorite disinfectants every morning. Patients with B. cepacia complex are seen in separate rooms, which are cleaned after every patient. Furthermore, the staff must disinfect hands with chlorhexidine-ethanol and change gowns between patients belonging to different cohorts, and between each patient with B. cepacia complex. Following lung function, elbow-piece, mouthpiece and nose clip are changed after each patient and sterilized in ethanol. For the first four cohorts separate camps and social events are advised, where each patient with B. cepacia complex is considered unique, and they are therefore advised against contact with any other CF patient. If a chronically infected patient (cohort 3) or 4)) get rid of the bacteria as judged by negative culture results and antibody response normalizes they can attend camps if they remain culture negative for 6 months. In addition to general universal precautions for preventing cross-infection, cohorting has proven efficient in preventing cross-infection with P aeruginosa and B. cepacia complex. Seeing patients on different days and disinfecting the clinic thoroughly between cohorts enables cohorting in the out-patient clinic, and cohort patients who are admitted to hospital can be seen in separate wards. Claus Mose; MD, Ph.D specializes in Clinical Microbiology He has worked with Professor Hoiby for more than ten years. His research interests include chronic injections especial/v chronic Pseudomonas aeruginosa lung injections in patients with CF urinary tract infection in patients with spinal cord injuries, and the significance of immune responses during chronic infections. Niels Hoibi; MD is the Chairman of the Department of Clinical Microbiology at the University of Copenhagen,Denmark. He is the President of the 2006 European Cystic Fibrosis Society Conference, and was recently honored with the Richard C.Talamo Distinguished Clinical Achievement Award. Editor's Note References
[Keyword: Cystic Fibrosis] |
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