Topics in Clinical Microbiology:Francisella tularensis

Abstract

In 1911, McCoy discovered an unusual illness among ground squirrels in Tulare County, California. The illness resembled plague but was clearly different because a pathogen could not be isolated on the usual culture media. With the addition of egg yolk to the media, McCoy finally isolated an organism and named it Bacterium tularensis. It was soon recognized that B. tularensis could cause disease in humans, and many investigators, especially Edward Francis, did much of the early work defining the bacteriology, pathology, and epidemiology of tularemia. The name of the organism was eventually changed to Francisella tularensis in honor of Francis.Unlike Pseudomonas aeruginosa and the Enterobacteriaceae which are relatively non-pathogenic in the normal host, F. tularensis can easily cause disease in previously healthy persons. In contrast, F. tularensis has not been implicated in nosocomial infections and person to person spread is rare. The organism is, however, extremely hazardous to workers in the clinical microbiology laboratory. Of all common bacterial and fungal pathogens isolated in the clinical laboratory, F. tularensis is second only to Coccidioides immitis in its potential to infect the laboratory worker. Many experienced investigators claim that it is impossible to work with the pathogen for any length of time without becoming infected. Currently it is highly recommended that persons who routinely work with the organism be immunized.

The Natural History of Aerosolized Francisella tularensis Infection in Cynomolgus Macaques

“…As previously seen in lethal human cases of tularemia [25], in this study, the lung, lymph nodes (particularly the mediastinal and tracheobronchial lymph nodes), spleen, liver, and bone marrow were the most severely affected tissues during F. tularensis infection regardless of exposure dose. Although varying in severity, multifocal and coalescing, necrotizing and pyogranulomatous pneumonia and abscessation with (or without) extensive edema, fibrinous pleuritis, and pleural fibrosis were consistent pathological findings in almost all macaques and corresponded with the intrathoracic histopathologic changes.…”

High-throughput metagenome analysis of the Sarcoptes scabiei internal microbiota and in-situ identification of intestinal Streptomyces sp.

“…For example, the tick Ixodes sp . is a vector for Borrelia burgdorferi causing Lyme’s disease 19 and Dermacentor andersoni is a vector for Francisella tularensis causing Tularemia 20 . It is hypothetically possible that the scabies mite may act as a carrier of pathogenic bacteria, as these have been localized in the mite feces 21 ; however direct transmission of bacteria by mites between hosts has not yet been demonstrated.…”

The AcrAB RND efflux system from the live vaccine strain ofFrancisella tularensisis a multiple drug efflux system that is required for virulence in mice

“…Francisella tularensis is a gram-negative facultative intracellular bacterium that causes the zoonotic disease tularemia. Francisella tularensis infection of humans can occur by a variety of routes, including the handling of infected animals, bites from arthropod vectors (Francis, 1937;Evans, 1985;Tarnvik, 1989), ingestion of contaminated food or water (Karpoff & Antononoff, 1936;Greco et al, 1987;Anda et al, 2001), and by inhalation (Teutsch et al, 1979;Syrjala et al, 1985). Francisella tularensis is a highly infectious bacterium and infection with as few as 10 bacteria can cause disease (Cross, 2000).…”