AUTHOR=Kingry Luke C., Petersen Jeannine M.

TITLE=Comparative review of Francisella tularensis and Francisella novicida

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=4

YEAR=2014

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2014.00035

DOI=10.3389/fcimb.2014.00035

ISSN=2235-2988

ABSTRACT=<p><italic>Francisella tularensis</italic> is the causative agent of the acute disease tularemia. Due to its extreme infectivity and ability to cause disease upon inhalation, <italic>F. tularensis</italic> has been classified as a biothreat agent. Two subspecies of <italic>F. tularensis, tularensis</italic> and <italic>holarctica</italic>, are responsible for tularemia in humans. In comparison, the closely related species <italic>F. novicida</italic> very rarely causes human illness and cases that do occur are associated with patients who are immune compromised or have other underlying health problems. Virulence between <italic>F. tularensis</italic> and <italic>F. novicida</italic> also differs in laboratory animals. Despite this varying capacity to cause disease, the two species share ~97% nucleotide identity, with <italic>F. novicida</italic> commonly used as a laboratory surrogate for <italic>F. tularensis</italic>. As the <italic>F. novicida</italic> U112 strain is exempt from U.S. select agent regulations, research studies can be carried out in non-registered laboratories lacking specialized containment facilities required for work with virulent <italic>F. tularensis</italic> strains. This review is designed to highlight phenotypic (clinical, ecological, virulence, and pathogenic) and genomic differences between <italic>F. tularensis</italic> and <italic>F. novicida</italic> that warrant maintaining <italic>F. novicida</italic> and <italic>F. tularensis</italic> as separate species. Standardized nomenclature for <italic>F. novicida</italic> is critical for accurate interpretation of experimental results, limiting clinical confusion between <italic>F. novicida</italic> and <italic>F. tularensis</italic> and ensuring treatment efficacy studies utilize virulent <italic>F. tularensis</italic> strains.</p>