Last data update: Sep 23, 2024. (Total: 47723 publications since 2009)
Records 1-3 (of 3 Records) |
Query Trace: Benson RF [original query] |
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Legionella nagasakiensis sp. nov., isolated from water samples in Japan and Australia and from a patient with pneumonia in the United States
Yang PG , Benson RF , Ratcliff R , Brown EW , Steigerwalt AG , Thacker LW , Daneshvar M , Morey RE , Saito A , Fields BS . Int J Syst Evol Microbiol 2011 62 284-288 A novel Legionella species was identified based on 16S rRNA and mip (macrophage infectivity potentiator) gene sequencing analysis, cellular fatty acids, isoprenoid quinones, biochemical reactions, antigens, and quantitative DNA-DNA hybridization. The strain CDC-1796-JAP-E(T) was isolated from well water at the Nagassaki Municipal Medical Center, Japan. Two strains, CDC-3041-AUS-E and CDC-3558-AUS-E, were isolated from water samples during an outbreak of legionellosis in South Australia. The strain CDC-5427-OH-H was isolated from a 66-year-old female patient diagnosed with Legionnaires' disease in the U.S. The cells from these four strains were gram-negative, non-fluorescent, rod-shaped, and positive for alkaline phosphatase, esterase, leucine arylamidase, catalase, gelatinase, beta-lactamase, and tyrosine browning assay. Phylogenetic analysis of 16S rRNA and mip genes revealed that the four strains formed a distinct cluster within the genus Legionella. The bacteria contained branched-chain fatty acids and quinones that are typical of the genus Legionella. Slide agglutination tests demonstrated no cross-reaction with 52 previously described Legionellaceae. DNA hybridization studies indicated DNAs from the four strains were highly related (78-84%) but showed 29% relatedness to L. oakridgensis (ATCC 33761(T)) and less than 10% to other Legionella species tested. These characterizations suggest that the isolates represent a novel species, for which the name Legionella nagasakiensis sp. nov is proposed, for the type strain CDC-1796-JAP-E(T) (=ATCC BAA-1557(T)=JCM 15315(T)). |
Virulence factors encoded by Legionella longbeachae identified on the basis of the genome sequence analysis of clinical isolate D-4968
Kozak NA , Buss M , Lucas CE , Frace M , Govil D , Travis T , Olsen-Rasmussen M , Benson RF , Fields BS . J Bacteriol 2009 192 (4) 1030-44 Legionella longbeachae causes most cases of legionellosis in Australia and may be under-reported worldwide due to the lack of L. longbeachae-specific diagnostic tests. L. longbeachae displays distinctive differences in intracellular trafficking, caspase-1 activation, and infection of mouse models compared to L. pneumophila, yet both species have an indistinguishable clinical presentation in humans. Unlike other legionellae, which inhabit fresh water systems, L. longbeachae is found predominantly in moist soil. In this study, we sequenced and annotated the genome of a L. longbeachae clinical isolate, D-4968, from Oregon, US, and compared it to the published genomes of L. pneumophila. The study revealed that the D-4968 genome is larger with a gene order that is different from L. pneumophila. Genes encoding structural components of type II, type IV Lvh, and type IV Icm/Dot secretion systems are conserved. In contrast, only 42/140 homologs of L. pneumophila Icm/Dot substrates have been found in the D-4968 genome. L. longbeachae encodes numerous proteins with eukaryotic motifs and eukaryotic-like proteins unique to this species, including 16 ankyrin repeat-containing proteins and a novel U-box protein. We predict that these proteins are secreted by the L. longbeachae Icm/Dot secretion system. In contrast to L. pneumophila, the L. longbeachae D-4968 genome does not carry flagellar biosynthesis genes, yet contains a chemotaxis operon. The lack of a flagellum explains the failure of L. longbeachae to activate caspase-1 and trigger pyroptosis in murine macrophages. These unique features of the L. longbeachae genome may reflect adaptation of this species to life in soil. |
Distribution of lag-1 alleles and sequence-based types among Legionella pneumophila serogroup 1 clinical and environmental isolates in the United States
Kozak NA , Benson RF , Brown E , Alexander NT , Taylor TH Jr , Shelton BG , Fields BS . J Clin Microbiol 2009 47 (8) 2525-35 Approximately 84% of legionellosis cases are due to Legionella pneumophila serogroup 1. Moreover, a majority of L. pneumophila serogroup 1 clinical isolates react positively with monoclonal antibody 2 (MAb2) of the international standard panel. Over 94% of the legionellosis outbreaks investigated by the Centers for Disease Control and Prevention are due to this subset of L. pneumophila serogroup 1. To date, there is no complete explanation for the enhanced ability of these strains to cause disease. To better characterize these organisms, we subtyped 100 clinical L. pneumophila serogroup 1 isolates and 50 environmental L. pneumophila serogroup 1 isolates from the United States by (i) reactivity with MAb2, (ii) presence of a lag-1 gene required for the MAb2 epitope, and (iii) sequence-based typing analysis. Our results showed that the MAb2 epitope and lag-1 gene are overrepresented in clinical L. pneumophila serogroup 1 isolates. MAb2 recognized 75% of clinical isolates but only 6% of environmental isolates. Similarly, 75% of clinical isolates but only 8% of environmental isolates harbored lag-1. We identified three distinct lag-1 alleles, referred to as Philadelphia, Arizona, and Lens alleles, among 79 isolates carrying this gene. The Arizona allele is described for the first time in this study. We identified 59 different sequence types (STs), and 34 STs (58%) were unique to the United States. Our results support the hypothesis that a select group of STs may have an enhanced ability to cause legionellosis. Combining sequence typing and lag-1 analysis shows that STs tend to associate with a single lag-1 allele type, suggesting a hierarchy of virulence genotypes. Further analysis of ST and lag-1 profiles may identify genotypes of L. pneumophila serogroup 1 that warrant immediate intervention. |
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