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. 2024 Jun 21;12(7):1253.
doi: 10.3390/microorganisms12071253.

Characterisation of Legionella Clinical Isolates in Spain from 2012 to 2022

Juana María González-Rubio  1 , Almudena Cascajero  1 , Beatriz Baladrón  1 , Fernando González-Camacho  1
Affiliations

Characterisation of Legionella Clinical Isolates in Spain from 2012 to 2022

Juana María González-Rubio et al. Microorganisms. .

Abstract

Although cases of Legionnaires' disease are notifiable, data on the phenotypic and genotypic characterisation of clinical isolates are limited. This retrospective study aims to report the results of the characterisation of Legionella clinical isolates in Spain from 2012 to 2022. Monoclonal antibodies from the Dresden panel were used for phenotypic identification of Legionella pneumophila. Genotypic characterisation and sequence type assignment were performed using the Sequence-Based Typing scheme. Of the 1184 samples, 569 were identified as Legionella by culture. Of these, 561 were identified as L. pneumophila, of which 521 were serogroup 1. The most common subgroups were Philadelphia (n = 107) and Knoxville (n = 106). The SBT analysis revealed 130 different STs, with the most common genotypes being ST1 (n = 87), ST23 (n = 57), ST20 (n = 30), and ST42 (n = 29). Knoxville has the highest variability with 32 different STs. ST23 is mainly found in Allentown/France (n = 46) and ST42 in Benidorm (n = 18), whereas ST1 is widely distributed. The results demonstrate that clinical isolates show high genetic diversity, although only a few sequence types (STs) are responsible for most cases. However, outbreaks can also occur with rare genotypes. More data on LD and associated epidemiological studies are needed to establish the risk of an isolate causing outbreak in the future.

Keywords: Legionella; Legionnaires’ disease; clinical isolates; outbreaks; public health; sequence-based typing.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
A temporal analysis of the distribution of clinical isolates caused by L. pneumophila SG1 throughout the 2012–2022 period.
Figure 2
Figure 2
Distribution of the most frequent isolates by phenotype and sequence type.
Figure 3
Figure 3
(A) Minimum-spanning tree analysis of 561 isolates obtained with PHYLOViZ for the ST allelic profiles. The pie charts represent the STs, with the size of each circle proportional to the number of isolates. The different colours of the pie charts refer to the phenotypic characteristics. The ST numbers are shown in black. The numbers on the branches represent the number of difference loci (in red). SLVs are indicated by red outlines, and non-SG1 are indicated by shaded backgrounds. (B) Enlarged image of SLV 1.
Figure 4
Figure 4
Distribution of isolates with phenotype and sequence type more frequently described in the study and their relationship with the number of isolates obtained in sporadic cases and outbreaks.
See this image and copyright information in PMC

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