Short-Term and Long-Term Survival and Virulence of Legionella pneumophila in the Defined Freshwater Medium Fraquil.

Legionella pneumophila (Lp) is the etiological agent responsible for Legionnaires' disease, a potentially fatal pulmonary infection. Lp lives and multiplies inside protozoa in a variety of natural and man-made water systems prior to human infection. Fraquil, a defined freshwater medium, was used as a highly reproducible medium to study the behaviour of Lp in water. Adopting a reductionist approach, Fraquil was used to study the impact of temperature, pH and trace metal levels on the survival and subsequent intracellular multiplication of Lp in Acanthamoeba castellanii, a freshwater protozoan and a natural host of Legionella. We show that temperature has a significant impact on the short- and long-term survival of Lp, but that the bacterium retains intracellular multiplication potential for over six months in Fraquil. Moreover, incubation in Fraquil at pH 4.0 resulted in a rapid decline in colony forming units, but was not detrimental to intracellular multiplication. In contrast, variations in trace metal concentrations had no impact on either survival or intracellular multiplication in amoeba. Our data show that Lp is a resilient bacterium in the water environment, remaining infectious to host cells after six months under the nutrient-deprived conditions of Fraquil

Survival of <i>Lp</i> at different trace metal concentrations and subsequent intracellular multiplication (ICM).

<p><b>A)</b> The JR32 strain of <i>Lp</i> was exposed to Fraquil at four different metal concentrations: no addition of trace metals (0X), standard Fraquil (1X), double the quantity of trace metals (2X) and 10 times the quantity of trace metals (10X) than in standard Fraquil. Weekly CFU counts were performed to track survival. DL, detection limit. <b>B)</b><i>A</i>. <i>castellanii</i> was infected with JR32 that had been exposed to the respective levels of trace metals tested for 30 days at an MOI of 0.1. Daily CFU counts monitored the ICM inside amoeba and are presented as the ratio over CFU counts at day 0. JR32 from BCYE was used as the positive control and <i>dotA</i>^- was used as the negative control.</p

Impact of pH on the short-term survival of <i>Lp</i> in Fraquil and intracellular multiplication (ICM) after exposure to different pH.

<p><b>A)</b> The JR32 strain of <i>Lp</i> was exposed to Fraquil at four different pH. Weekly CFU counts were performed to track survival. DL, detection limit. At pH 4 and pH 5, CFU counts from 2 days are statistically different (<i>P</i>≤0.05) than CFU counts at pH 7. At pH 6, CFU counts from 38 days are statistically different than CFU counts at pH 7. <b>B)</b><i>A</i>. <i>castellanii</i> was infected with JR32 that had been exposed to the respective pH tested for either 1 day or 7 days at an MOI of 0.1. Daily CFU counts monitored the ICM inside amoeba and are presented as the ratio over CFU counts at day 0. JR32 from BCYE was used as the positive control and <i>dotA</i>^- was used as the negative control. *** <i>P</i>≤ 0.005 versus control.</p

Descriptive study of 896 Oral squamous cell carcinomas from the only University based Oral Pathology Diagnostic Service in Sri Lanka

The study sample comprised of eight hundred and ninety six biopsies diagnosed as OSCC. The clinical and histopathological features were analyzed using the Chi-square test

Presence of selected Icm/Dot effectors in strains isolated in Quebec City.

a<p>Patient isolates related to the outbreak (patient), a subset of environmental isolates with different PFGE pattern than the epidemic strain (environment), isolates from a former outbreak in the same area in 1996 and other clinical strains (Lens, Corby, Lorraine, Philadelphia-1, Paris and HL06041035).</p