title: Sequence based typing and pre-absorption test in retrospective analysis of a pseudo-outbreak of Legionella infections differentiates true cases of legionellosis.
abstract: The aim of this study was elimination of false positive results obtained by the Chlamylege kit. Two serological kits (IgM ELISA L. pneumophila sgs1-7; ImmuView(TM) L. pneumophila sg1/sg3) and pre-absorption tests (with L. pneumophila sg1 and sg3 reference strains antigens) were used. 153 sera (79 patients) were examined. The high correlations were found between the results by both tests. Positive results by ELISA (sgs1-7) were found in 19/79 patients; by ImmuView(TM) (sg1+sg3) in 16/63. In 8 patients, the dynamics of the IgM in pairs of sera was high (ratio ≥2). In 5/8 of those patients seroconversion was determined. Selected pre-absorbed sera (15 pairs) were tested simultaneously by the same tests. In 8/15 pairs of sera, the reduction of IgM levels in pre-absorbed sera was higher than 10. The reduction of IgM differed in sg1 and sg3 tests. The probability of infections due to L. pneumophila sg3 (7 patients) and L. pneumophila sg1 (5 patients) was based on the results of pre-absorption tests. The correlation between ELISA and ImmuView(TM) tests of pre-absorbed sera was statistically significant (Po=0.0389). Moreover, genotyping of L. pneumophila (SBT) directly in the sera of selected 15 patients (high IgM reduction) was carried out. Completed 7 alleles profile (ST36) was determined in one patient. However, a second patient had the same profile of 5 alleles, and similar reactions in pre-absorption tests. At least 4 sources of infections were suggested on the base of genotyping and pre-absorption results.
  
  
  CONCLUSIONS
  Positive results obtained by molecular techniques (eg.PCR) in the diagnosis of Legionella infections should be supplemented by other tests for confirmation of legionellosis. The sequence based typing carried out directly in clinical specimens seems to be a promising method.
authors.affiliation: National Institute of Public Health-National Institute of Hygiene, Warsaw, Poland. kpancer@pzh.gov.pl
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Pancer
authors.forename: Karina
authors.initials: K
authors.lastname: Jahnz-Różyk
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Kucharczyk
authors.forename: Włodzimierz
authors.initials: W
authors.lastname: Gut
authors.forename: Piotr
authors.initials: P
authors.lastname: Kucharczyk
authors.forename: Pernille L
authors.initials: PL
authors.lastname: Elverdal
authors.forename: Bogumiła
authors.initials: B
authors.lastname: Litwińska
mesh_terms: D000328:Adult; D000369:Aged, 80 and over; D000372:Agglutination Tests / Q000379:methods*; D000907:Antibodies, Bacterial / Q000097:blood; D001426:Bacterial Proteins / Q000235:genetics; D015373:Bacterial Typing Techniques; D002846:Chromatography, Affinity; D004269:DNA, Bacterial / Q000032:analysis; D004196:Disease Outbreaks; D004797:Enzyme-Linked Immunosorbent Assay; D005189:False Positive Reactions; D005260:Female; D005838:Genotype; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood; D007875:Legionella / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D016952:Legionella pneumophila / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D007876:Legionellosis / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D007877:Legionnaires' Disease / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D008297:Male; D008875:Middle Aged; D011044:Poland / Q000453:epidemiology; D016133:Polymerase Chain Reaction; D012189:Retrospective Studies; D017422:Sequence Analysis, DNA; D012703:Serotyping; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007075:Immunoglobulin M