Biomedical subjects
Publications and source records attributed to Didier Raoult.
Mimivirus, the largest virus known to date, is an amebal pathogen-like Legionella sp. When Mimivirus was used as an antigen in a microimmunofluorescense assay, seroconversion was found in patients with both community- and hospital-acquired pneumonia. Mimivirus DNA was found in respiratory samples of a patient with hospital-acquired pneumonia.
Coxiella burnetii is a strict intracellular bacterium with potential as a bioterrorism agent. To characterize different isolates of C. burnetii at the molecular level, we performed multispacer sequence typing (MST). MST is based on intergenic region sequencing. These regions are potentially variable since they are subject to lower selection pressure than the adjacent genes. We screened 68 spacers in 14 isolates and selected the 10 that exhibited the most variation. These spacers were then tested in 159 additional isolates obtained from different geographic areas or different hosts or were implicated in different manifestations of human disease caused by C. burnetii. The sequence analysis yielded 30 different allelic combinations. Phylogenic analysis showed 3 major clusters. MST allows easy comparison and exchange of results obtained in different laboratories and could be a useful tool for identifying bacterial strains.
We recovered Bartonella quintana DNA from dental pulp of a domestic cat. This study, the first to detect B. quintana in a nonhuman mammal, changes our understanding of the epidemiology of this infection and proposes that cats may be an emerging source of human infection.
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We detected Rickettsia felis DNA in Ctenocephalides felis and Bartonella quintana DNA in 3 Pulex irritans fleas taken from a pet Cercopithecus cephus monkey in Gabon, sub-Saharan Africa. This is the first report of B. quintana in the human flea.
We report the first cases of human infection by Rickettsia felis in the Canary Islands. Antibodies against R. felis were found in 5 adsorbed serum samples from 44 patients with clinically suspected rickettsiosis by Western blot serology. Fleas from 1 patient's dog were positive for R. felis by polymerase chain reaction.
Bartonella quintana is a fastidious microorganism associated with blood culture negative endocarditis. In this study, 40 sera with cross-reactivity between Chlamydia species from patients from Sfax, Tunisia, were serologically tested for Bartonella. Thirteen sera were positive for Bartonella with IgG titers >/=1:800. Western blot and cross-absorption confirmed the diagnosis of Bartonella quintana endocarditis in 12 cases and Bartonella henselae endocarditis in 1 case. These sera were also positive by LightCycler nested PCR amplification for the rnpb (7 of 13) and fur (11 of 13) genes. Eleven patients had a definite diagnosis of endocarditis, which represents 9.8% of all endocarditis. Because Bartonella endocarditis seems to be very common in Tunisia, we suggest that its serology be performed systematically whenever endocarditis is suspected.
Trench fever, a louse-borne disease caused by Bartonella quintana, is reemerging in homeless persons. Epidemic typhus is another life-threatening louse-borne disease caused by Rickettsia prowazekii and known to occur in conditions of war, famine, refugee camps, cold weather, poverty, or lapses in public health. We report the first case of seroconversion to R. prowazekii in a homeless person of Marseilles, France. This was associated with B. quintana bacteremia. Although no outbreaks of typhus have been notified yet in the homeless population, this disease is likely to reemerge in such situation.
Although Plasmodium falciparum malaria and Q fever are both prevalent in Africa, there have been no reports of co-infection to date. We report a case who returned from the Comoros archipelago diagnosed by serologic analysis as well as detection of Coxiella burnetii DNA in acute-phase serum. Thus, Q fever may be associated with malaria infection in travelers returning from disease-endemic countries. This diagnosis should be considered when the response to malaria treatment is incomplete.
A Japanese traveler returning from Kenya became ill, presenting with fever and a prominent, generalized rash without an eschar. Results of the immunofluorescence antibody assay of the patient's sera performed in Japan were compatible with illness due to a spotted fever group (SFG) rickettsia, and a presumptive diagnosis of African SFG rickettsiosis, probably either Mediterranean spotted fever (MSF) or African tick-bite fever (ATBF), was rendered. To further define the disease diagnosis, sera were examined in France by Western immunoblotting combined with cross-adsorption, which confirmed the diagnosis of MSF but not of ATBF. Because of the need to further characterize the epidemiologic and clinical features of the two African SFG rickettsioses, clinicians are encouraged to contact a specialized laboratory when encountering such cases.
To date, 14 tick-borne diseases have been reported in international travellers, the majority of cases being Lyme borreliosis caused by Borrelia burgdorferi sensu lato in North America and Eurasia, African tick bite fever caused by Rickettsia africae in sub-Saharan Africa and eastern Caribbean, and Central European encephalitis caused by tick-borne encephalitis virus in Europe. The clinical presentation is frequently non-specific, and tick-borne diseases should always, in the absence of other likely diagnoses, be suspected in travellers with flu-like symptoms following a recent visit to tick-infested areas. Feasible microbiological diagnostic tests are widely unavailable, at least outside areas of endemicity where many infected travellers present. Empiric treatment with doxycycline should be considered in suspected cases of tick-borne bacterial diseases. Since ecotourism and adventure travel are increasingly popular worldwide, the incidence of travel-associated tick-borne diseases is likely to increase in the future.
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Rickettsia conorii is an obligate intracellular bacterium transmitted to humans by Rhipicephalus sanguineus ticks. The success of this microorganism at surviving in nature implicates the ability to efficiently adapt to different environments, including the arthropod vector and the mammalian host. Numerous bacterial species possess a highly evolved system for stress adaptation. This so-called stringent response is mediated by guanosine 3',5'-bispyrophosphate and guanosine 3'-diphosphate 5'-triphosphate which are under spoT control in some Gram-negative bacteria. Interestingly, annotation of the R. conorii genome evidenced 5 spoT paralogs. We hypothesized that these spoT genes play a role in adaptation to environmental changes specifically encountered by rickettsiae during their different life cycles. Transcription of the spoT paralogs was examined by RT-PCR from infected Vero cells maintained in rich or deficient culture media, from infected C6/36 insect cells cultured at various temperatures and from infected ticks. Our results demonstrated that the 5 spoT genes can be transcribed. SpoT1 (RC0374) is only transcribed upon stringent response. Transcription of spoT3 (RC0888) was never observed in arthropod cells or ticks, but was specific to R. conorii RNA extracted from infected Vero cells. These results indicate that rickettsial spoT paralogs are independently transcribed, depending on the different infected hosts and the adaptive capacity of the pathogen. Bioinformatics analysis of these possibly encoded proteins is also reported.
Bartonella henselae causes chronic bacteremia in cats. To test if B. henselae DNA can be recovered from the dental pulp of cats buried a year previously, we used PCR with primers for a sequence of the conserved groEL to test 104 teeth from 11 cats. Seven of the cats were found positive; canine teeth were more frequently positive than molar teeth. Where PCR sequences could be determined, they were identical to those of B. henselae Marseille (four cats), B. henselae Houston (one cat) or similar to those of B. grahamii (one cat). Our study indicates that dental pulp from the teeth of cats, especially the canine teeth, may be used for the PCR detection of Bartonella in animals buried for a year.
The rickettsioses--zoonotic bacterial infections transmitted to humans by arthropods--were for many years considered to be oddities in travel medicine. During the previous 2 decades, however, reports of >450 travel-associated cases have been published worldwide, the vast majority being murine typhus caused by Rickettsia typhi, Mediterranean spotted fever caused by Rickettsia conorii, African tick bite fever caused by Rickettsia africae, and scrub typhus caused by Orientia tsutsugamushi. Most patients present with a benign febrile illness accompanied by headache, myalgia, and cutaneous eruptions, but severe complications and fatalities are occasionally seen. Current microbiological tests include culture, polymerase chain reaction, and serological analysis, of which only the latter method is widely available. Tetracyclines are the drugs of first choice and should be prescribed whenever a case of rickettsiosis is suspected. Preventive measures rely on minimizing the risk of arthropod bites when traveling in areas of endemicity.
We recently reported the discovery and preliminary characterization of Mimivirus, the largest known virus, with a 400-nanometer particle size comparable to mycoplasma. Mimivirus is a double-stranded DNA virus growing in amoebae. We now present its 1,181,404-base pair genome sequence, consisting of 1262 putative open reading frames, 10% of which exhibit a similarity to proteins of known functions. In addition to exceptional genome size, Mimivirus exhibits many features that distinguish it from other nucleocytoplasmic large DNA viruses. The most unexpected is the presence of numerous genes encoding central protein-translation components, including four amino-acyl transfer RNA synthetases, peptide release factor 1, translation elongation factor EF-TU, and translation initiation factor 1. The genome also exhibits six tRNAs. Other notable features include the presence of both type I and type II topoisomerases, components of all DNA repair pathways, many polysaccharide synthesis enzymes, and one intein-containing gene. The size and complexity of the Mimivirus genome challenge the established frontier between viruses and parasitic cellular organisms. This new sequence data might help shed a new light on the origin of DNA viruses and their role in the early evolution of eukaryotes.
Bartonella species are responsible for chronic bacteremia in domestic cats, which raises a question about the antiquity of the relationship between Bartonella species and cats that act as reservoirs for the organism. The sequencing of Bartonella pap31 and groEL genes from the dental pulp of cats dating from the 13th to 16th centuries identified the presence of B. henselae genotype Houston; the observation of a unique mutation in the results of PCR assays for Bartonella species ruled out modern DNA contamination of the dental pulp samples. We conclude that cats had bacteremia due to B. henselae 800 years ago.
Q fever is caused by Coxiella burnetii, a bacterium that survives in monocytes/macrophages by resisting their natural microbicidal activity. Because the link between bacterial killing and phagosome maturation has yet to be demonstrated, we evaluated responses in monocytes from both immunologically naive control subjects and patients with various manifestations of Q fever. Monocytes from patients with chronic Q fever in evolution, who do not control the infection, exhibited defective phagosome maturation and impaired C. burnetii killing. Both responses were stimulated in patients recovering from Q fever. Phagosome maturation and C. burnetii killing were significantly correlated. Defective phagosome maturation and impaired C. burnetii killing were induced by adding interleukin (IL)-10 to monocytes from convalescent patients and were restored by IL-10 neutralization in chronic Q fever in evolution. We show that phagosome maturation and microbial killing are linked in Q fever and that IL-10 regulates both features of microbicidal activity.