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RESEARCH PAPER
 
 

Sequence based typing and pre-absorption test in retrospective analysis of a pseudo-outbreak of [i]Legionella[/i] infections differentiates true cases of legionellosis

 
1
National Institute of Public Health-National Institute of Hygiene, Warsaw, Poland
2
Department of Immunology and Clinical Allergology, Military Institute of Medicine, Warsaw, Poland
3
Serum Production, SSI Diagnostica, Statens Serum Institute, Hillerod, Denmark
Ann Agric Environ Med 2012;19(3):437–443
KEYWORDS:
ABSTRACT:
The aim of this study was elimination of false positive results obtained by the Chlamylege kit. Two serological kits (IgM ELISA [i]L.pneumophila[/i] sgs1-7; ImmuView[sup]TM[/sup] [i]L.pneumophila[/i] sg1/sg3) and pre-absorption tests (with [i]L.pneumophila[/i] 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[sup]TM[/sup] (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 [i]L.pneumophila[/i] sg3 (7 patients) and [i]L.pneumophila[/i] sg1 (5 patients) was based on the results of pre-absorption tests. The correlation between ELISA and ImmuView[sup]TM[/sup] tests of pre-absorbed sera was statistically significant (Po=0.0389). Moreover, genotyping of [i]L.pneumophila[/i] (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 [i]Legionella[/i] 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.
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eISSN:1898-2263
ISSN:1232-1966