ABSTRACT
OBJECTIVE: Q fever epidemic outbreaks have been reported in French Guiana and in The Netherlands. To determine whether the C. burnetii strains involved in these epidemics had a peculiar virulence pattern, we compared the pathogenicity of the Guiana and the German strain (a clone of The Netherlands strain), in silico, in vitro, and in vivo versus the Nine Mile strain. METHOD: The pan-genomes of the Guiana (Cb175), German (Z3055), and the referent Nine Mile (RSA 493) C. burnetii strains were compared. In vitro, the growth rate and the morphological presentation were compared. In vivo (SCID and Balb/c mice), weight loss, histological lesions, C. burnetii bacterial load in deep organs, and serological response were reported according to each C. burnetii strain studied. RESULTS: The Guiana strain had 77 times more missing genes and 12 times more unique genes than the German strain. The Guiana strain presented as large cell variants (LCVs) and led to the most pronounced fatality rate in SCID mice (100% at 4 weeks). The German strain presented as small cell variants (SCVs), and had an intermediate fatality rate (75% at 4 weeks). Both the Guiana and the German strains led to a significant higher serological response at 2 and 4 weeks post infection (p <0.05). CONCLUSION: The Guiana strain was the most virulent strain, followed by the German strain and the referent Nine Mile strain. Unique and missing genes could be implicated but further investigations are necessary to specify their role.
Subject(s)
Coxiella burnetii/pathogenicity , Disease Outbreaks , Q Fever/epidemiology , Q Fever/microbiology , Animals , Antibodies, Bacterial/blood , Coxiella burnetii/classification , Coxiella burnetii/genetics , Coxiella burnetii/growth & development , DNA, Bacterial/analysis , Disease Models, Animal , French Guiana/epidemiology , Genetic Variation , Genome, Bacterial/genetics , Mice, Inbred BALB C , Mice, SCID , Netherlands/epidemiology , Q Fever/blood , Q Fever/pathology , Survival Analysis , VirulenceABSTRACT
OBJECTIVES: Cytomegalovirus (CMV) reactivation in intensive care unit patients may increase mortality and favour bacterial pneumonia. We developed a murine model to compare the severity of staphylococcal pneumonia after CMV reactivation and in CMV-negative mice. METHODS: Balb/c mice were primo-infected with murine cytomegalovirus (MCMV n=90) or received saline (control n=90). After latency, all mice underwent caecal ligation and puncture to trigger MCMV reactivation in MCMV primary-infected mice. Surviving animals received an intra-nasal inoculation with methicillin-susceptible Staphylococcus aureus (MSSA) to induce pneumonia. Mortality, lung bacterial count, histology and interferon-alpha and gamma serum levels were compared in MCMV reactivated and control mice 2, 5 and 15 days after pneumonia. RESULTS: After MSSA pneumonia, MCMV mice showed a trend towards a higher mortality (9.4% versus 0%; p 0.09) and a higher weight loss (2.2 (0.6-4.1 g) versus 0.7 (-0.3 to 1.3 g); p 0.005). The lung bacterial count was higher in MCMV mice 2 days (5×103 (103 to 3×105) versus 102 (0 to 4×102) CFU/lung; p 0.007) and 5 days (2.5×104 (1.6×104 to 6.5×105) versus 15 (10-40) CFU/lung; p 0.005) after MSSA pneumonia. 8/40 (20%) MCMV mice developed lung abscesses compared to 0% in control (p 0.011). Interferon-alpha serum levels 2 days after staphylococcal pneumonia were higher in MCMV mice. CONCLUSIONS: MCMV reactivation decreased lung bacterial clearance and favoured the development of staphylococcal abscessing pneumonia. CMV reactivation may be responsible for a higher susceptibility to bacterial sepsis.
