Phenotypic variation amongst genotypically homogeneous<i>Legionella pneumophila</i>serogroup 1 isolates: implications for the investigation of outbreaks of Legionnaires' disease

Harrison, Timothy G.; Saunders, Nicholas A.; Haththotuwa, A.; Hallas, Gillian; Birtles, Richard J.; Taylor, A. G.

doi:10.1017/s0950268800059331

Cited by 37 publications

(27 citation statements)

References 16 publications

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“…The latter strain differed from the strain from hospital water only at markers Lpms1 and Lpms4, which could mean that the strain is of a different origin or that it is a variant of the strain isolated from water. This is reminiscent of the results of Harrison et al (9), who suggested that phenotypic variation of a single parent organism could account for the phenotypically different strains isolated from a single cooling tower. A larger number of colonies isolated from water could have been analyzed by tandem repeat typing at the time of the infection (as shown in Fig.…”

Section: Discussionsupporting

confidence: 53%

Characterization of a Tandem Repeat Polymorphism inLegionella pneumophilaand Its Use for Genotyping

Pourcel¹,

Vidgop²,

Ramisse

et al. 2003

J Clin Microbiol

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We have analyzed the variability of minisatellite sequences (also called variable-number tandem repeats [VNTRs]) in the genome of Legionella pneumophila. Based upon the genome sequence of the Philadelphia-1 strain (serogroup 1), 25 minisatellites were selected and their polymorphisms were analyzed by PCR with the DNA of serogroup 1 to 14 reference strains. For 22 markers, a PCR product of the expected size was found with the DNA of the Philadelphia-1 strain. Most of these markers did not amplify the DNA of other Legionella species or other bacteria used as controls. A polymorphism was observed for seven markers among the L. pneumophila strains tested. To check whether these markers could be used to compare strains of L. pneumophila, we analyzed two groups of isolates from clinical and environmental samples which had been independently genotyped by other methods. The results showed that, for the isolates in these two sets of samples, VNTR typing is as informative as pulsed-field gel electrophoresis for comparison of strains. Sequencing of one minisatellite from 14 reference strains was performed. Comparison of the sequences allowed a classification and confirmed the existence of subspecies of L. pneumophila. We also tested the usefulness of one very polymorphic marker as a tool for the rapid screening of colonies grown from water samples. This allowed the rapid identification of the L. pneumophila colonies and gave a first hint as to the presence of several strains in a single sample.

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Section: Discussionsupporting

confidence: 53%

Characterization of a Tandem Repeat Polymorphism inLegionella pneumophilaand Its Use for Genotyping

Pourcel¹,

Vidgop²,

Ramisse

et al. 2003

J Clin Microbiol

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“…There was, however, no difference in the PFGE and AFLP patterns, even in a single band. Such serologic subtype variations have been reported earlier (11,18,30). The question whether these different phenoms represent an environmentally induced phenotypic expression or are caused by a true genetic event preceding the serologic change (14,20,34) could for the first time be answered in the present (16,34).…”

Section: Discussionmentioning

confidence: 72%

A Hospital-Associated Outbreak of Legionnaires' Disease Caused by Legionella pneumophila Serogroup 1 Is Characterized by Stable Genetic Fingerprinting but Variable Monoclonal Antibody Patterns

et al. 2003

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An outbreak of 18 pneumonia cases caused by Legionella pneumophila serogroup 1 occurred at a Swedish university hospital 1996 to 1999. Eight clinical isolates obtained by culture from the respiratory tract were compared to 20 environmental isolates from the hospital and to 21 epidemiologically unrelated isolates in Sweden, mostly from patients, by using pulsed-field gel electrophoresis (PFGE), amplified fragment length polymorphism analysis (AFLP), and monoclonal antibody (MAb) typing. All patients and most environmental isolates from the outbreak hospital belonged to the same genotypic cluster in both PFGE and AFLP. This genotype was distinctly different from other strains, including a cluster from a second hospital in a different part of the country. The MAb subtype of the outbreak clone was Knoxville except for three isolates that were Oxford. A variation in the MAb reactivity pattern was also found in a second genotypic cluster. These changes in the MAb reactivity pattern were due to the absence or presence of the lag-1 gene coding for an Oacetyltransferase that is responsible for expression of the lipopolysaccharide epitope recognized by MAb 3/1 of the Dresden Panel. In all MAb 3/1-positive strains, the lag-1 gene was present on a genetic element that was bordered by a direct repeat that showed a high degree of sequence homology. Due to this homology, the lag-1 gene region seemed to be an unstable element in the chromosome. MAb patterns are thus a valuable adjunct to genotyping methods in defining subgroups inside a genotypic cluster of L. pneumophila sg 1.

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“…The method has been used widely in the investigation of outbreaks and clusters of legionellosis in the UK [15, 17, 181. Although the discriminatory power of the RFLP technique appears to be good, giving an index of discrimination (IOD) [19] of 0.909, in practice it has been found that some RFLP patterns are seen more frequently than others (e.g., RFLP type 1 [15]). In 1995, Luck and colleagues [20] demonstrated that a panel of isolates obtained from a single source, and considered to be indistinguishable by RFLP typing [21], could be discriminated hrther by PFGE with S' I .…”

Section: Introductionmentioning

confidence: 99%

Molecular typing of Legionella pneumophila serogroup 1 by pulsed-field gel electrophoresis with Sfil and comparison of this method with restriction fragment-length polymorphism analysis

Zoysa¹,

Harrison²

1999

Journal of Medical Microbiology

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A panel of 131 well-characterised Legionella pneumophila serogroup 1 strains, previously used to evaluate a restriction fragment-length polymorphisms (RFLP) typing scheme, was examined by pulsed-field gel electrophoresis (PFGE) with the restriction endonuclease SfiI. The data obtained show that PFGE with SfiI is a highly discriminatory method yielding an index of discrimination (IOD) of 0.992 and 0.975, with 100% and, 90% similarity thresholds respectively, compared with an IOD of 0.909 for the RFLP typing method. Reproducibility of PFGE profiles within gels was excellent and it was possible to compare the profiles visually. However, the reproducibility of the technique between gels was poor and visual comparison of the patterns was extremely difficult. Computer-aided analysis assisted the assessment of inter-gel reproducibility. Of 11 duplicates examined only four pairs showed 100% similarity, although 9 of 11 showed 390% similarity. In an attempt to determine if the PFGE banding patterns were sufficiently unambiguous to allow the method to be used as a definitive typing method, 20 coded strains were examined. At a 90% similarity level, 16 of these were placed in the correct PFGE type and four were not allocated to a type. Partial digestion of DNA by SfiI was noted despite careful control of DNA and enzyme concentrations, suggesting that an alternative enzyme might give more reproducible results.

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Phenotypic variation amongst genotypically homogeneousLegionella pneumophilaserogroup 1 isolates: implications for the investigation of outbreaks of Legionnaires' disease

Cited by 37 publications

References 16 publications

Characterization of a Tandem Repeat Polymorphism inLegionella pneumophilaand Its Use for Genotyping

Characterization of a Tandem Repeat Polymorphism inLegionella pneumophilaand Its Use for Genotyping

A Hospital-Associated Outbreak of Legionnaires' Disease Caused by Legionella pneumophila Serogroup 1 Is Characterized by Stable Genetic Fingerprinting but Variable Monoclonal Antibody Patterns

Molecular typing of Legionella pneumophila serogroup 1 by pulsed-field gel electrophoresis with Sfil and comparison of this method with restriction fragment-length polymorphism analysis

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