Identification and characterization of Francisella species from natural warm springs in Utah, USA

Abstract

Aims: To characterize Francisella isolated from two natural warm springs in Utah and compare them to a strain isolated from a patient with probable exposure to one of the springs in 2001. Methods and Results: A total of 39 presumptive Francisella isolates were obtained from two springs, Wasatch Hot Spring and Hobo Warm Spring, just north of Salt Lake City, Utah. All isolates were characterized by a combination of biochemical and molecular analyses, including novel PCR/electrospray ionization‐mass spectrometry (ESI‐MS) typing assays. Thirty‐one were identified as F. philomiragia, while the remaining eight were identified as F. tularensis ssp. novicida. Phylogenetic analysis of the 16S rRNA sequences revealed 27 isolates, which clustered with F. philomiragia, albeit into two distinct clades. The remaining isolates clustered along with other F. tularensis strains including the Utah clinical isolate. Testing with the PCR/ESI‐MS assays confirmed the identities of the isolates, but both yielded DNA signatures distinct from that of the clinical isolate. Conclusion: We were successful in isolating several Francisella strains from natural warm springs; however, none appeared to genetically match the original 2001 clinical isolate. Significance and Impact of the Study: This work highlights the presence of viable, potentially pathogenic Franscisella species living in the unique environmental niche of natural warm springs.

Whole-Genome Relationships among Francisella Bacteria of Diverse Origins Define New Species and Provide Specific Regions for Detection

“…All of the comparisons presented here show that, as of November 2016, the DPG 3A-IS genome sequence accessed at NCBI and used for comparison in this study originated from an F. tularensis isolate. The original DPG 3A-IS isolate was characterized as F. novicida by multiple methods (97). Independent DNA purification and genome sequencing will be important in order to verify whether the original DPG 3A-IS can be confirmed as F. novicida.…”

Comparative review of Francisella tularensis and Francisella novicida

“…F. novicida infection in humans is exceedingly rare and therefore often difficult to diagnose accurately (Brett et al, 2012; Birdsell et al, 2009). Only 12 cases have been documented (Hollis et al, 1989; Clarridge et al, 1996; Leelaporn et al, 2008; Birdsell et al, 2009; Brett et al, 2012; Respicio-Kingry et al, 2012; Sjödin et al, 2012; Whitehouse et al, 2012). An F. novicida -like infection was reported in an Australian patient, however, genome comparisons indicate the strain is more similar to F. hispanensis (Whipp et al, 2003; Sjödin et al, 2012).…”

“…Clinical information available for 11 reported cases indicate that 9 of the F. novicida cases occurred in patients who were immuno-compromised or had underlying health problems (Hollis et al, 1989; Clarridge et al, 1996; Leelaporn et al, 2008; Birdsell et al, 2009; Brett et al, 2012; Respicio-Kingry et al, 2012; Whitehouse et al, 2012). Fever and acute disease, hallmarks of tularemia in healthy individuals, were only observed for F. novicida infections in compromised patients (Hollis et al, 1989; Clarridge et al, 1996; Leelaporn et al, 2008; Brett et al, 2012; Respicio-Kingry et al, 2012; Whitehouse et al, 2012). In the two healthy individuals with F. novicida infection, regional lymphadenopathy, lacking fever or other symptoms, was reported (Hollis et al, 1989; Birdsell et al, 2009).…”

Biofilms

“…However, using molecular methods, Francisella species have been detected in many natural water samples throughout the Northern Hemisphere, 15 , 132 , 133 although the “culturability” of these samples was not always demonstrated. Historically, many older publications regarding the natural history of tularemia also included reference to natural water sources, 7 , 125 , 134 - 136 and water is named as the source of several of the well-studied strains, including F. philomiragia and F. novicida .…”