Biomedical subjects
Publications and source records attributed to D Raoult.
Sera obtained from 274 dairy cows in commercial dairies around Zimbabwe examined by indirect immunofluorescence for antibodies reactive with phase II Coxiella burnetii antigens. Overall, 41 pc of the cows were reactive at a titre of 1/40 or greater with the seroprevalence in dairies varying from 33-75 pc. The implications for human and animal health are discussed.
The authors review the literature concerning the treatment of rickettsiosis including Rocky Mountain spotted fever, Mediterranean spotted fever, murine typhus, and Scrub typhus. They report in vitro antibiotic susceptibilities of the causing organisms and in vivo activity on animal models. They also report their clinical experience and these of the literature in the treatment of rickettsiosis.
Sera were collected from apparently healthy dogs in 3 major centres in Zimbabwe to establish the prevalence of antibodies reactive with Ehrlichia canis by indirect fluorescent antibody (IFA) testing at titres of 1/20 or greater. The overall seroprevalence was 42% (39/93) with dogs from Mutare (40%) and Harare (33%) having similar rates which were lower than those for Bulawayo (68%). The majority of the IFA positive dogs from Harare (67%) had no haematological or biochemical evidence of canine ehrlichiosis. Total protein, albumin and globulin values were determined in sera from blood collected from Bulawayo and Mutare and all values were within normal reference ranges. Western blot profiles of sera from dogs with IFA titres of greater than 1/160 were similar to those using sera from dogs experimentally infected with E. canis Oklahoma strain. Our results indicate that an organism which is antigenically very similar or identical to E. canis is present in Zimbabwe and that dogs are commonly exposed to this organism.
Sera from 494 humans, 180 cattle, 180 goats and 27 dogs, collected from different regions of Zimbabwe, were examined by indirect fluorescence for antibodies reactive with phase II Coxiella burnetii antigen. Overall, 37% of humans were reactive at a titre of 1/40 or greater, and there was no evidence of age- or sex-related differences in seroprevalence. A review of clinical and epidemiological features of Q fever is presented in order to alert health workers to this infection, which apparently occurs frequently in Zimbabwe even though clinical cases have not been reported. In animals, serological evidence of Q fever infection was found in 39% of cattle, but only 15% of dogs and 10% of goats. These results suggest that cattle are important reservoirs of C. burnetii in Zimbabwe.
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The authors report the general epidemiologic features of Mediterranean spotted fever (MSF) in the Marseille area (South France). Age was a risk factor, increasing after 50 years, and annual incidence seemed positively correlated with the average temperature of the preceding year and negatively correlated with the number of days with frost of the preceding year. However, correlations were not significant.
Cases of murine typhus were described in Chalkis, capital town of the island Evia in Greece. In the present work a prospective study on murine typhus was carried out in Chalkis General Hospital in 1985, is presented. During this year 49 cases, serologically confirmed using indirect fluorescence assay, were diagnosed. Signs and symptoms of the patients as well as preliminary epidemiological data are reported in this paper.
PURPOSE: To contribute to the knowledge of epidemiologic and clinical features of patients hospitalized with Q fever in France. METHODS: We conducted a retrospective analysis of 22,496 sera submitted between 1982 and 1990 to the French National Reference Center for Rickettsial Diseases (NRC). The diagnosis of acute Q fever was based on an IgG titer greater than or equal to 1:200 and an IgM titer greater than or equal to 1:25 against phase II Coxiella burnetii antigen on an indirect immunofluorescence test (IFA). Fifteen cases prior to 1985 were diagnosed on the basis of a complement fixation titer greater than or equal to 1:8. A serosurvey of blood donors from Marseille was also conducted in 1988 on 924 sera, using IFA with a cutoff titer of 1:25. RESULTS: The serosurvey conducted in 1988 showed a seroprevalence of 4.03%, without age or sex prediction. The incidence rate of acute Q fever detection at the NRC was 0.58 per 100,000 inhabitants over the 9-year period. Three hundred twenty-three clinical cases were diagnosed, rising from 1 in 1982 to 107 in 1990. In patients hospitalized for acute Q fever, there was a significantly higher sex ratio of males to females (2.3), which, coupled with the age distribution, indicated that elder males, who are overrepresented due to our recruitment bias, are more susceptible to C. burnetii infections. The mean age of the patients was 45.5 years, while the risk was increased in the 30 to 39 age group as well as in the 60 to 69 age group. Usual epidemiologic risk factors were found in 20.1% of the cases. Hepatitis (61.9%) was a more common clinical presentation in our patients with Q fever than pneumonia (45.8%). This might reflect differences in strains of C. burnetii or the biology of the host. However, French farmers and stock breeders commonly drink unpasteurized raw milk from their cattle, which might indicate a relationship between hepatitis and infection via the digestive tract. CONCLUSION: Our results indicate that many cases of acute Q fever are undiagnosed. A greater awareness of the disease and more extensive serologic testing of patients with symptoms compatible with Q fever may improve the situation.
Rhodococcus equi is an emerging opportunistic pathogen of HIV-I infected patients. It is an aerobic, Gram-positive coryneform bacterium which acts as a facultative intracellular micro-organism, multiplying in the phagosome of macrophages. Eighteen cases of R. equi infection in HIV-I positive patients have now been reported. Sixteen of these had pneumonia, of which 12 had cavitating lung lesions. A history of contact with farm animals, which are the primary hosts of R. equi, was found in only three patients. There was a delay in establishing a definite diagnosis in most cases as this depended upon the isolation of R. equi from sputum, bronchoalveolar lavage fluid, or blood. Treatment included surgical resection in five patients and erythromycin with a second antibiotic in 13 cases, but II of the 18 patients died from the infection. In this report we describe our experience of R. equi pneumonia in two AIDS patients and review the published cases of the disease in man.
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Mediterranean spotted fever is endemic in southern France, especially during summer. Clinical diagnosis is generally based upon the presence of a febrile eruption with or without the typical tache noire. Usual laboratory findings, which include thrombocytopenia, elevated levels of hepatic enzymes, and hyponatremia, are not specific to the disease. The diagnosis may be confirmed serologically by obtaining specific western immunoblot results and by isolation of Rickettsia conorii from blood culture with use of the shell vial cell culture technique. We report here the first documented case of spotless boutonneuse fever.
Q fever is caused by Coxiella burnetii, a strictly intracellular bacterium that lives within the phagolysosome of infected cells. We report here five cases of Q fever in patients with cancer. Three of them had a solid tumor, one had a B cell lymphoma, and one had chronic myeloid leukemia. One patient had acute Q fever, and the four others had chronic Q fever endocarditis. Two patients with endocarditis had no previous history of valvulopathy. C. burnetii was isolated from the valves of two patients. One of the patients with endocarditis died. Patients with cancer who have unexplained fever and live in areas in which C. burnetii is endemic should undergo serological testing for infection with this microorganism.
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Rickettsia conorii, an obligate intracellular bacterium that infects vascular endothelial cells, is the etiologic agent of Mediterranean spotted fever (MSF). A new procedure using indirect immunofluorescence was used to directly detect R. conorii in circulating endothelial cells (CEC). CEC were separated from other blood components by using anti-endothelial cell monoclonal antibody-coated magnetic beads. An anti-R. conorii polyclonal rabbit antiserum was used to stain rickettsiae. The entire procedure took 3 h. R. conorii was detected in CEC from 9 of 12 patients ultimately confirmed as having MSF. Among the patients, 5 with R. conorii isolated by centrifugation-shell vial assay were also positive by the new technique. None of 3 patients whose diagnosis was other than MSF had R. conorii detected in CEC. The procedure may be helpful for rapid diagnosis of MSF and may lead to new technical approaches for the diagnosis of infectious diseases caused by intracellular pathogenic microorganisms.
Most infections due to intracellular bacteria respond poorly to antibiotic treatment. The chemical conditions within the subcellular site of bacteria may change antibiotic activity. Coxiella burnetii multiplies within phagolysosomes. The antimicrobial activity of antibiotics combined with the lysosomotropic agents amantadine (1 microgram/mL), chloroquine (1 microgram/mL), and ammonium chloride (1 mg/mL), which alkalinized Coxiella burnetii-containing phagolysosomes from pH 4.8 to 5.3, 5.7, and 6.8, respectively, was evaluated. Percentages of residual viable bacteria (RVB) in cell cultures were significantly reduced after exposure to combinations of doxycycline (4 micrograms/mL) with amantadine (RVB = 18.2% +/- 8.7%, P < .05), chloroquine (RVB = 0.64% +/- 0.38%, P < .01), or ammonium chloride (RVB = 0.29% +/- 0.17%, P < .01); the same was seen with pefloxacin (1 microgram/mL) with chloroquine (RVB = 27.6% +/- 10.8%, P < .05) or ammonium chloride (RVB = 3.72% +/- 1.1%, P < .05). Such bactericidal activity correlated with increased phagolysosomal pH, as determined by Pearson's correlation coefficient, suggesting that phagolysosomal alkalinization is critical for the bactericidal effect of antibiotics.