Distribution of Legionella pneumophila serogroups, monoclonal antibody subgroups and DNA sequence types in recent clinical and environmental isolates from England and Wales (2000–2008)

Abstract

Clinical isolates of Legionella pneumophila, obtained from 167 patients, who acquired their illness in the community in England and Wales between January 2000 and March 2008, were compared with 276 environmental isolates of L. pneumophila obtained over the same period as part of the routine sampling of 'managed' water systems. The 443 isolates were typed by monoclonal antibody (mAb) subgrouping and the internationally standardised, seven-gene loci, sequence-based typing (SBT) scheme of the European Working Group for Legionella Infections (EWGLI). Of the clinical isolates, 97.6% were L. pneumophila serogroup (sgp) 1, compared with only 55.8% of environmental isolates (P = 0.0002); 91.6% were subgrouped as mAb3/1+ve, compared with only 8.3% of environmental isolates (P < 0.0001). The isolates were very diverse, with SBT identifying 111 sequence types (STs) (index of diversity [IOD] 0.954). Among the clinical isolates, 42 ST were seen, with one (ST47) accounting for 25.7% and three (ST47, ST37 and ST62) accounting for 46.1% of all isolates. Eighty-two STs were identified among the environmental isolates, with two (ST1 and ST79) accounting for 34.1% of these. Comparison of the STs seen among clinical and environmental isolates showed that there was very little overlap between the two populations (P < 0.0001), with common clinical strains found in the environment very infrequently: 0.4, 0.7 and 0% (ST47, ST37 and ST62, respectively), and common environmental strains rarely causing disease: 4.8 and 1.2% (ST1 and ST79, respectively). Combining phenotypic and genotypic data identified 144 phenons (IOD 0.970); 52 among clinical isolates and 101 among environmental isolates. The most abundant clinical strain, mAb 'Allentown' ST47, accounted for 22.8% of cases, but was only found once in the environment. Conversely, mAb 'Oxford/OLDA' ST1 was the most common environmental strain (17.0%), but only caused two infections. A review of the published data shows that mAb 'Allentown' ST47 is also an important cause of infection in France and possibly in the Netherlands. However, it was not found in a large study of German clinical isolates. This study confirms previous work showing that just a few strains of L. pneumophila cause the majority of community-acquired Legionella infection in England and Wales, and that these clinically significant strains are only rarely found in managed water systems. These data suggest that knowing which particular strain is present in an environment might be at least as important as knowing the quantity in which legionellae are present.

Sequence-based and monoclonal antibody typing of Legionella pneumophila isolated from patients in Portugal during 1987-2008

“…The significant profile diversity we observed is in accordance with reports from the other countries [4,14,16,17]. Due to the relatively low number of isolates in each ST, with the majority (13/23) of the STs being detected only once, it is not possible to establish a correlation between the ST and the infection origin.…”

“…The neuA primers failed to type these three strains, all of which were non-sg1 (one sg 10 and the other two could not be identified with MAbs of Dresden panel),suggesting that neuA primers described by Ratzow et al [12] are not always suitable for serogroups other than sg1. Other teams have also reported amplification problems with the neuA primers [14].…”

“…It is interesting to notice that five of these new allele numbers were detected only in L. pneumophila non-sg1 strains that were non-typable with MAbs from the Dresden panel (see Table). The ST100 (3,8,1,10,14,12,2) was the most frequent allele (32/67). This is a new profile and all of the ST100 strains had been isolated in patients of the same hospital over a period of several years.…”

Prevalence of 7 virulence genes of <i>Legionella</i> strains isolated from environmental water sources of public facilities and sequence types diversity of <i>L. pneumopila</i> strains in Macau

“…In a recent study conducted in the United States, ST1 accounted for 25% and 49% of the number of the sporadic and environmental isolates, respectively (17). In one study conducted in England and Wales, ST1 was the most frequent STs, accounting for 35% of the number of L. pneumophila environmental isolates (18). From the L. pneumophila serogroup 1 isolates from potable systems, cooling towers, and hot springs in China, ST1 were reported to be about 14.3%, to 53.1% and 92.3%, respectively (19).…”

Legionella, légionellose

“…Ces mêmes outils ont révélé que la majorité des isolats cliniques correspond à un nombre très limité de souches présentes dans l'environnement [11,12]. Ainsi, au sein même des L. pneumophila séro-groupe 1, toutes les souches ne semblent pas présenter le même potentiel pathogène vis-à-vis de l'homme.…”