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Origin of Pseudomonas aeruginosa strains causing chronic colonisation in CF patients
S30
5. Microbiology
113* Multilocus sequence typing (MLST) of Pseudomonas aeruginosa collected from different ecological niches
115* Origin of Pseudomonas aeruginosa strains causing chronic colonisation in CF patients
T.J. Kidd1,2 , P.B. Rainey3 , K.A. Ramsay1,2 , K. Grimwood1,2 , C.E. Wainwright1,2 , S.C. Bell1,4 . 1 University of Queensland, School of Medicine, Brisbane, QLD, Australia; 2 Royal Children’s Hospital, Queensland Children’s Medical Research Institute, Brisbane, QLD, Australia; 3 Massey University, New Zealand Institute for Advanced Study, College of Sciences, Auckland, New Zealand; 4 The Prince Charles Hospital, Thoracic Medicine, Brisbane, QLD, Australia
C. Lucas1 , C. Williams1 , J. Wilkinson1 . 1 Yorkhill Hospital, Glasgow, United Kingdom
Background: Pseudomonas aeruginosa is the most important respiratory pathogen in cystic fibrosis (CF). Although unproven, it is generally thought to be acquired from the environment. However, molecular typing studies indicate person-to-person transmission by some clonal strains may also occur. In Australia, clonal CF strains have not been compared previously with isolates collected from non-CF patients, animals or the environment. Aim: To determine the sequence-based clonality of P. aeruginosa isolates collected from several different ecological niches. Methods: MLST was performed on 509 isolates collected from CF patients (n = 168), non-CF patients (n = 129), animals (n = 106), and the natural environment (n = 106). CF isolates included each of the major and minor clonal Australian strains and a range of unique strains isolated from patients residing in South East Queensland (Qld). Non-CF, animal and environmental isolates were collected from the same region. Results: Of the 280 individual strains detected, 55 (19.6%) were found in more than one niche. Overall, 30 unique and minor clonal CF strains were detected in at least one other niche; including 13 CF strains found in the environment. None of the 3 major Qld CF clonal strains were detected in another niche. Conclusions: In CF, environmental exposure to P. aeruginosa seems important for acquiring unique and minor clonal strains. Finding that the 3 major clonal strains were confined to CF patients further suggests person-to-person transmission is occurring and/or strain associated adaptation to the CF lung. Support: NHMRC, ACFRT, TPCH Foundation.
114 Microarray genotyping of Pseudomonas aeruginosa isolates from CF units A.J. Hall1 , J.L. Fothergill1,2 , K.W. Southern3 , P.S. McNamara3 , M.J. Ledson4 , M.J. Walshaw4 , C. Winstanley1 . 1 Unversity of Liverpool, Medical Microbiology and Genitourinary Medicine, Liverpool, United Kingdom; 2 Biomedical Research Centre, Liverpool, United Kingdom; 3 Alder Hey Children’s Hospital, Liverpool, United Kingdom; 4 Liverpool Heart and Chest Hospital, Liverpool, United Kingdom Background: Pseudomonas aeruginosa is a ubiquitous organism, causing increased morbidity and mortality amongst CF patients. In a clinic with a high prevalence of a well recognised transmissible strain (the Liverpool Epidemic Strain [LES]), our aim was to determine the genotypes of non-LES isolates as a first step to developing a better strategy for the detection of emerging problem strains. Methods: 22 isolates from the Liverpool Childrens CF unit were studied. All isolates were confirmed as Pseudomonas aeruginosa by PCR assays for the oprL gene and as non-LES by using LES-specific PCR assays. The Clondiag tube array genotyping method consists of 77 oligonucleotide probes immobilised onto a microarray chip. Strain genotypes can be obtained by hybridisation to determine single nucleotide polymorphism patterns. These genetic fingerprints can be used to assign clone types by comparison with a previously described database. Results: Of the 22 isolates studied 17 (77%) corresponded with previously reported clone types, of which 5 (22%) were clone D. In comparison a previous study reported only a 2.9% representation of this clone. We are further extending the study to include non-LES P. aeruginosa from the adult CF unit. Conclusion: Although it is possible that clone D may have spread through patient to patient transmission, it is equally conceivable that within the Merseyside area this strain is more prevalent. Our initial study forms the basis of a reference for future comparisons to track the emergence of any new epidemic strains in both the paediatric and adult CF units in Liverpool. We acknowledge funding from the NIHR.
Objective: The origin of Pseudomonas aeruginosa (PSA) strains that successfully establish chronic respiratory colonisation in CF sufferers remains uncertain. The organism is highly adaptable and gene expression is influenced by environmental conditions. In the CF lung, phenotypic changes in PSA enhance its ability to avoid clearance by host defence mechanisms and antibiotic therapy. The objective of this study was to determine whether chronic colonisation is more likely to occur with strains already adapted to respiratory survival. Methods: PFGE typing data on PSA strains isolated from 83 CF sufferers attending a Regional Paediatric CF Centre between 2003 and 2008 were considered in relation to chronicity of carriage. Results: Of all colonised patients, 68% had intermittent carriage and 61% harboured unique PSA strains. Thirteen percent of patients were chronically colonised with unique strains versus 19% chronically colonised with a strain common to more than one patient. Yearly data suggest an increased prevalence of unique strains among all colonised patients, with 60% of chronic carriers harbouring unique strains by 2008. Discussion: The overall data suggested that exposure to CF-adapted strains may influence the risk of chronicity but the impact of historical infection control issues was exposed on examination of yearly data. Following introduction of segregation protocols, the prevalence of shared strains diminished. Conclusion: Having minimised exchange of PSA strains in hospital and social settings, efforts must now be redoubled to identify sources and reduce exposure to unique, presumably environmental PSA, that can equally culminate in chronic infection and pulmonary damage.
116* Predictors of progression to chronic Pseudomonas aeruginosa (Pa) infection in children with CF classified in the intermittent Pa group A. Kotwal1 , M. Denton2 , K.G. Brownlee3 , S.P. Conway3 , T.W. Lee3 . 1 St James’s University Hospital, Leeds Regional Paediatric Cystic Fibrosis Centre, Leeds, United Kingdom; 2 Leeds Teaching Hospital NHS Trust, SJUH, Department of Microbiology, Leeds, United Kingdom; 3 Leeds Teaching Hospital NHS Trust, Regional Cystic Fibrosis Centre, SJUH, Leeds, United Kingdom Background: The “Leeds definition” recognises 4 categories of Pa infection in CF (1). The intermittent Pa group appears diverse, as individuals may revert back to the “free” group, or may progress to “chronic”. Factors predicting progression to chronic infection remain unclear. Aim: To identify factors in the intermittent Pa group predicting progression to “chronic”. Methods: A retrospective study of patients classified as intermittent Pa in 5 cohorts from 1990–2002 was performed. The outcome of each patient 3 years later was recorded as “intermittent Pa”, “free” or “chronic”. Potential predicting factors were studied. Results: Of 105 patients, 12 became chronic, 49 remained intermittent, and 44 became free of infection after 3 years. Patient gender did not predict the outcome. The mean age of children who became free after 3 years was significantly lower (p = 0.038). Negative sputum cultures showed significant association with becoming “free” (p = 0.01), but negative cough swabs did not (p = 0.664). Presence of mucoid strain of Pa was significantly associated with progression to “chronic” (p = 0.009). Conclusions: Younger patients were associated with an improved rate of successful eradication of Pa infection. Negative cough swabs are not as reliable as negative sputum culture in predicting whether a patient will be free of infection 3 years later. The mucoid form of Pa is associated with progression to chronic infection. Reference(s) [1] Lee TWR et al. J Cystic Fibrosis 2003; 2: 29−34.
5. Microbiology
113* Multilocus sequence typing (MLST) of Pseudomonas aeruginosa collected from different ecological niches
115* Origin of Pseudomonas aeruginosa strains causing chronic colonisation in CF patients
T.J. Kidd1,2 , P.B. Rainey3 , K.A. Ramsay1,2 , K. Grimwood1,2 , C.E. Wainwright1,2 , S.C. Bell1,4 . 1 University of Queensland, School of Medicine, Brisbane, QLD, Australia; 2 Royal Children’s Hospital, Queensland Children’s Medical Research Institute, Brisbane, QLD, Australia; 3 Massey University, New Zealand Institute for Advanced Study, College of Sciences, Auckland, New Zealand; 4 The Prince Charles Hospital, Thoracic Medicine, Brisbane, QLD, Australia
C. Lucas1 , C. Williams1 , J. Wilkinson1 . 1 Yorkhill Hospital, Glasgow, United Kingdom
Background: Pseudomonas aeruginosa is the most important respiratory pathogen in cystic fibrosis (CF). Although unproven, it is generally thought to be acquired from the environment. However, molecular typing studies indicate person-to-person transmission by some clonal strains may also occur. In Australia, clonal CF strains have not been compared previously with isolates collected from non-CF patients, animals or the environment. Aim: To determine the sequence-based clonality of P. aeruginosa isolates collected from several different ecological niches. Methods: MLST was performed on 509 isolates collected from CF patients (n = 168), non-CF patients (n = 129), animals (n = 106), and the natural environment (n = 106). CF isolates included each of the major and minor clonal Australian strains and a range of unique strains isolated from patients residing in South East Queensland (Qld). Non-CF, animal and environmental isolates were collected from the same region. Results: Of the 280 individual strains detected, 55 (19.6%) were found in more than one niche. Overall, 30 unique and minor clonal CF strains were detected in at least one other niche; including 13 CF strains found in the environment. None of the 3 major Qld CF clonal strains were detected in another niche. Conclusions: In CF, environmental exposure to P. aeruginosa seems important for acquiring unique and minor clonal strains. Finding that the 3 major clonal strains were confined to CF patients further suggests person-to-person transmission is occurring and/or strain associated adaptation to the CF lung. Support: NHMRC, ACFRT, TPCH Foundation.
114 Microarray genotyping of Pseudomonas aeruginosa isolates from CF units A.J. Hall1 , J.L. Fothergill1,2 , K.W. Southern3 , P.S. McNamara3 , M.J. Ledson4 , M.J. Walshaw4 , C. Winstanley1 . 1 Unversity of Liverpool, Medical Microbiology and Genitourinary Medicine, Liverpool, United Kingdom; 2 Biomedical Research Centre, Liverpool, United Kingdom; 3 Alder Hey Children’s Hospital, Liverpool, United Kingdom; 4 Liverpool Heart and Chest Hospital, Liverpool, United Kingdom Background: Pseudomonas aeruginosa is a ubiquitous organism, causing increased morbidity and mortality amongst CF patients. In a clinic with a high prevalence of a well recognised transmissible strain (the Liverpool Epidemic Strain [LES]), our aim was to determine the genotypes of non-LES isolates as a first step to developing a better strategy for the detection of emerging problem strains. Methods: 22 isolates from the Liverpool Childrens CF unit were studied. All isolates were confirmed as Pseudomonas aeruginosa by PCR assays for the oprL gene and as non-LES by using LES-specific PCR assays. The Clondiag tube array genotyping method consists of 77 oligonucleotide probes immobilised onto a microarray chip. Strain genotypes can be obtained by hybridisation to determine single nucleotide polymorphism patterns. These genetic fingerprints can be used to assign clone types by comparison with a previously described database. Results: Of the 22 isolates studied 17 (77%) corresponded with previously reported clone types, of which 5 (22%) were clone D. In comparison a previous study reported only a 2.9% representation of this clone. We are further extending the study to include non-LES P. aeruginosa from the adult CF unit. Conclusion: Although it is possible that clone D may have spread through patient to patient transmission, it is equally conceivable that within the Merseyside area this strain is more prevalent. Our initial study forms the basis of a reference for future comparisons to track the emergence of any new epidemic strains in both the paediatric and adult CF units in Liverpool. We acknowledge funding from the NIHR.
Objective: The origin of Pseudomonas aeruginosa (PSA) strains that successfully establish chronic respiratory colonisation in CF sufferers remains uncertain. The organism is highly adaptable and gene expression is influenced by environmental conditions. In the CF lung, phenotypic changes in PSA enhance its ability to avoid clearance by host defence mechanisms and antibiotic therapy. The objective of this study was to determine whether chronic colonisation is more likely to occur with strains already adapted to respiratory survival. Methods: PFGE typing data on PSA strains isolated from 83 CF sufferers attending a Regional Paediatric CF Centre between 2003 and 2008 were considered in relation to chronicity of carriage. Results: Of all colonised patients, 68% had intermittent carriage and 61% harboured unique PSA strains. Thirteen percent of patients were chronically colonised with unique strains versus 19% chronically colonised with a strain common to more than one patient. Yearly data suggest an increased prevalence of unique strains among all colonised patients, with 60% of chronic carriers harbouring unique strains by 2008. Discussion: The overall data suggested that exposure to CF-adapted strains may influence the risk of chronicity but the impact of historical infection control issues was exposed on examination of yearly data. Following introduction of segregation protocols, the prevalence of shared strains diminished. Conclusion: Having minimised exchange of PSA strains in hospital and social settings, efforts must now be redoubled to identify sources and reduce exposure to unique, presumably environmental PSA, that can equally culminate in chronic infection and pulmonary damage.
116* Predictors of progression to chronic Pseudomonas aeruginosa (Pa) infection in children with CF classified in the intermittent Pa group A. Kotwal1 , M. Denton2 , K.G. Brownlee3 , S.P. Conway3 , T.W. Lee3 . 1 St James’s University Hospital, Leeds Regional Paediatric Cystic Fibrosis Centre, Leeds, United Kingdom; 2 Leeds Teaching Hospital NHS Trust, SJUH, Department of Microbiology, Leeds, United Kingdom; 3 Leeds Teaching Hospital NHS Trust, Regional Cystic Fibrosis Centre, SJUH, Leeds, United Kingdom Background: The “Leeds definition” recognises 4 categories of Pa infection in CF (1). The intermittent Pa group appears diverse, as individuals may revert back to the “free” group, or may progress to “chronic”. Factors predicting progression to chronic infection remain unclear. Aim: To identify factors in the intermittent Pa group predicting progression to “chronic”. Methods: A retrospective study of patients classified as intermittent Pa in 5 cohorts from 1990–2002 was performed. The outcome of each patient 3 years later was recorded as “intermittent Pa”, “free” or “chronic”. Potential predicting factors were studied. Results: Of 105 patients, 12 became chronic, 49 remained intermittent, and 44 became free of infection after 3 years. Patient gender did not predict the outcome. The mean age of children who became free after 3 years was significantly lower (p = 0.038). Negative sputum cultures showed significant association with becoming “free” (p = 0.01), but negative cough swabs did not (p = 0.664). Presence of mucoid strain of Pa was significantly associated with progression to “chronic” (p = 0.009). Conclusions: Younger patients were associated with an improved rate of successful eradication of Pa infection. Negative cough swabs are not as reliable as negative sputum culture in predicting whether a patient will be free of infection 3 years later. The mucoid form of Pa is associated with progression to chronic infection. Reference(s) [1] Lee TWR et al. J Cystic Fibrosis 2003; 2: 29−34.