Therapeutic impact of the correlation of doxycycline serum concentrations and the decline of phase I antibodies in Q fever endocarditis.

BACKGROUND: Endocarditis is the main clinical manifestation of chronic Q fever, a challenging disease due to Coxiella burnetii. The recommended treatment for Q fever endocarditis is a combination of doxycycline and hydroxychloroquine for at least 18 months. However, there is considerable heterogeneity in the biological response to this regimen as measured by the rate of decrease of dilutions of phase I antibodies against C. burnetii. Previous studies have demonstrated that this response heterogeneity was due to variations in the serum concentration of doxycycline in patients when compared with MICs for the isolates. OBJECTIVES: The objective of this study was to evaluate retrospectively the evolution of phase I antibodies in patients with an initial slow serological change, who received higher doses of doxycycline. RESULTS: Among 17 patients with definitive diagnosis of Q fever endocarditis, 12 were defined as slow responders [mean (+/- SD) decrease of dilutions of phase I antibodies of 0.42 +/- 0.51 and mean (+/-SD) serum doxycycline level of 3.44 +/- 1.06 mg/L after 1 year of treatment] and received increased doses of doxycycline. After 1 year of treatment with increased dose, the mean (+/-SD) serum doxycycline concentration increased to 4.86 +/- 1.14 mg/L (P<0.05) and the mean (+/-SD) decrease of dilutions of phase I antibodies increased to 3.42 +/- 1.78 (P<0.05). CONCLUSIONS: During the treatment of Q fever endocarditis, serum concentrations of doxycycline should be monitored concomitantly with phase I antibodies in order to adjust the dose of doxycycline to achieve a higher concentration for patients with slow serological evolution.

Prevotella massiliensis sp. nov. isolated from human blood.

We report a bacterial isolate (Marseille isolate) recovered from the blood of a patient hospitalized in an intensive care unit, presenting with severe trauma, fever and mechanical ventilation. Colonies appeared at 37 degrees C on blood agar after 72 h incubation. This isolate was a strictly anaerobic, Gram-negative rod phenotypically related to other Prevotella species described to date: non-motile, catalase-negative, oxidase-positive, non-glucose fermenting, resistant to vancomycin and susceptible to kanamycin. Cells exhibited a trilamellar membrane under electron microscopy. The fatty acid methyl ester profile was marginally related to that of Clostridium botulinum group A (distance: 26.27%) and Bifidobacterium bifidum GC subgroup B (distance: 26.38%). 16S rRNA gene sequence similarity was 90.0% with that of Prevotella oris and 89.1% with that of Prevotella melaninogenica. Partial rpoB gene sequence similarity was 84.5 and 86.4% with P. oris and P. melaninogenica, respectively. According to current standards, phenotypic traits, 16S rRNA and rpoB gene sequence analyses indicated that the Marseille isolate belonged to a previously unrecognized species of the genus Prevotella, and we propose classifying it in the new taxon "Prevotella massiliensis" sp. nov.

Bacteroides massiliensis sp. nov., isolated from blood culture of a newborn.

Gram-negative anaerobic rods were isolated from blood culture of a healthy baby born at term. Based on phylogenetic analysis and specific phenotypic characteristics, this strain was included within the Bacteroides cluster. The novel bile-resistant anaerobic species was designated Bacteroides massiliensis and it has 92.8 % 16S rRNA similarity to Bacteroides vulgatus and a DNA G + C content of 49 mol%. The major cellular fatty acid is anteiso-branched C(15 : 0). The type strain of B. massiliensis sp. nov. is B84634(T) (=CIP 107942(T) = CCUG 48901(T)).

Correlation between ratio of serum doxycycline concentration to MIC and rapid decline of antibody levels during treatment of Q fever endocarditis.

Endocarditis is the major clinical manifestation of chronic Q fever. Although doxycycline along with hydroxychloroquine remains the mainstay of medical therapy for Q fever endocarditis, there are wide variations in the rapidity of the patient's decline of antibody levels during such therapy. We undertook a retrospective examination of whether there was any correlation between the ratio of serum concentration to MIC of doxycycline and response to treatment in patients with Q fever endocarditis. Included herein are 16 patients from whom Coxiella burnetii was isolated from cardiac valve materials. Serology and measurement of doxycycline and hydroxychloroquine serum levels were performed and recorded after 1 year of treatment. The MIC of doxycycline for C. burnetii isolates was determined using the shell vial assay in a real-time quantitative PCR assay. At the completion of a year-long therapy with doxycycline-hydroxychloroquine, all those that showed a low decline of antibody levels (n = 6) (i.e., <2-fold decrease in antibody titer to phase I C. burnetii antigen) had a ratio of serum doxycycline concentration to MIC between 0.5 and 1. In contrast, those having a ratio of > or =1 showed a rapid decline of phase I antibody levels (n = 9; P < 0.05). The only patient who died had a serum doxycycline-to-MIC ratio of <0.5, and the isolate of C. burnetii cultured from this patient was resistant to doxycycline (MIC = 8 microg/ml). The ratio of serum doxycycline concentration to MIC should be monitored during the course of therapy in patients with Q fever endocarditis.

Description of Afipia birgiae sp. nov. and Afipia massiliensis sp. nov. and recognition of Afipia felis genospecies A.

On the basis of phenotypic characterization and DNA relatedness, two novel species are proposed, Afipia birgiae sp. nov. (type strain 34632T = CIP 106344T = CCUG 43108T) and Afipia massiliensis sp. nov. (type strain 34633T = CIP 107022T = CCUG 45153T). A new genospecies is described, named Afipia felis genospecies A, closely related to Afipia felis. The complexity encountered in the taxonomy of the Bradyrhizobiaceae group within the alpha-2 subgroup of the Proteobacteria is discussed and the description of these novel species highlights the need for new tools for phylogenetic analysis in the group. The novel species herein described are fastidious bacteria isolated from a hospital water supply in co-culture with amoebae. It is hypothesized that this group of bacteria are a potential cause of nosocomial infections.

Bosea eneae sp. nov., Bosea massiliensis sp. nov. and Bosea vestrisii sp. nov., isolated from hospital water supplies, and emendation of the genus Bosea (Das et al. 1996).

On the basis of phenotypic and DNA relatedness data, three novel species of the genus Bosea are proposed, Bosea massiliensis (63287T =CIP 106336T =CCUG 43117T), Bosea vestrisii (34635T =CIP 106340T =CCUG 43114T) and Bosea eneae (34614T =CIP 106338T =CCUG 43111T). The original description of the genus Bosea included thiosulphate oxidation as a phenotypic feature, when the sole and type species of the genus, Bosea thiooxidans, was proposed. The three novel species described herein were not able to oxidize thiosulphate; thus, it is proposed that this characteristic be removed from the description of the genus and considered as specific for B. thiooxidans. The novel species of the genus Bosea proposed here form a well-separated cluster in the Bradyrhizobium group of the alpha-2 subclass of the Proteobacteria, on the basis of 16S rDNA gene sequence analysis. However, 16S rDNA gene sequence analysis was not sufficient to delineate the species; hence, DNA-DNA relatedness and phenotypic data were also required. All of the novel species described in this study are fastidious bacteria isolated from a hospital water supply, using co-cultivation with amoebae. This group of bacteria are hypothesized to be a potential cause of nosocomial infections. For treatment of infections caused by these novel bacteria, doxycycline appears to be the sole antibacterial compound with a consistently low MIC value.

Culture and antibiotic susceptibility of Bartonella quintana in human erythrocytes.

Bartonella quintana, the agent of trench fever, has recently been implicated in various diseases, in particular, bacteremia and endocarditis in homeless people. The host cell of Bartonella spp. is believed to be the erythrocyte, and in the present study we demonstrate that B. quintana can be cultured in vitro in human erythrocytes. The bacteria were found to be intraerythrocytic by laser confocal microscopy with Bartonella species-specific monoclonal antibodies. Infections with B. quintana decreased the life span of erythrocytes in culture from 8.6 to 4.8 days. In the culture system we found that most of the antibiotics that we tested (doxycycline, fluoroquinolone compounds, and beta-lactams) were not bactericidal. Gentamicin was bactericidal at 4 micro g/ml, as was rifampin, but to a lesser extent. At this concentration, gentamicin has been shown to enter erythrocytes slowly and to reach a peak level of 0.26 micro g/ml after 24 h. At 0.26 micro g/ml, however, we found that gentamicin was not able to kill extracellular B. quintana, even after 96 h of incubation. We hypothesize that erythrocytes may be a reservoir for B. quintana and that the bactericidal activity of gentamicin that we observed occurs mainly when the bacteria emerge from the erythrocytes and are found extracellularly. It would appear that gentamicin should be administered for at least 5 days to cure patients infected with B. quintana.