Sophie Edouard

From Q Fever to Coxiella burnetii Infection: a Paradigm Change

SUMMARY Coxiella burnetii is the agent of Q fever, or “query fever,” a zoonosis first described in Australia in 1937. Since this first description, knowledge about this pathogen and its associated infections has increased dramatically. We review here all the progress made over the last 20 years on this topic. C. burnetii is classically a strict intracellular, Gram-negative bacterium. However, a major step in the characterization of this pathogen was achieved by the establishment of its axenic culture. C. burnetii infects a wide range of animals, from arthropods to humans. The genetic determinants of virulence are now better known, thanks to the achievement of determining the genome sequences of several strains of this species and comparative genomic analyses. Q fever can be found worldwide, but the epidemiological features of this disease vary according to the geographic area considered, including situations where it is endemic or hyperendemic, and the occurrence of large epidemic outbreaks. In recent years, a major breakthrough in the understanding of the natural history of human infection with C. burnetii was the breaking of the old dichotomy between “acute” and “chronic” Q fever. The clinical presentation of C. burnetii infection depends on both the virulence of the infecting C. burnetii strain and specific risks factors in the infected patient. Moreover, no persistent infection can exist without a focus of infection. This paradigm change should allow better diagnosis and management of primary infection and long-term complications in patients with C. burnetii infection.

Current and Past Strategies for Bacterial Culture in Clinical Microbiology

SUMMARY A pure bacterial culture remains essential for the study of its virulence, its antibiotic susceptibility, and its genome sequence in order to facilitate the understanding and treatment of caused diseases. The first culture conditions empirically varied incubation time, nutrients, atmosphere, and temperature; culture was then gradually abandoned in favor of molecular methods. The rebirth of culture in clinical microbiology was prompted by microbiologists specializing in intracellular bacteria. The shell vial procedure allowed the culture of new species of Rickettsia. The design of axenic media for growing fastidious bacteria such as Tropheryma whipplei and Coxiella burnetii and the ability of amoebal coculture to discover new bacteria constituted major advances. Strong efforts associating optimized culture media, detection methods, and a microaerophilic atmosphere allowed a dramatic decrease of the time of Mycobacterium tuberculosis culture. The use of a new versatile medium allowed an extension of the repertoire of archaea. Finally, to optimize the culture of anaerobes in routine bacteriology laboratories, the addition of antioxidants in culture media under an aerobic atmosphere allowed the growth of strictly anaerobic species. Nevertheless, among usual bacterial pathogens, the development of axenic media for the culture of Treponema pallidum or Mycobacterium leprae remains an important challenge that the patience and innovations of cultivators will enable them to overcome.

Common Epidemiology of Rickettsia felis Infection and Malaria, Africa

This study aimed to compare the epidemiology of Rickettsia felis infection and malaria in France, North Africa, and sub-Saharan Africa and to identify a common vector. Blood specimens from 3,122 febrile patients and from 500 nonfebrile persons were analyzed for R. felis and Plasmodium spp. We observed a significant linear trend (p<0.0001) of increasing risk for R. felis infection. The risks were lowest in France, Tunisia, and Algeria (1%), and highest in rural Senegal (15%). Co-infections with R. felis and Plasmodium spp. and occurrences of R. felis relapses or reinfections were identified. This study demonstrates a correlation between malaria and R. felis infection regarding geographic distribution, seasonality, asymptomatic infections, and a potential vector. R. felis infection should be suspected in these geographical areas where malaria is endemic. Doxycycline chemoprophylaxis against malaria in travelers to sub-Saharan Africa also protects against rickettsioses; thus, empirical treatment strategies for febrile illness for travelers and residents in sub-Saharan Africa may require reevaluation.

Mass gathering and globalization of respiratory pathogens during the 2013 Hajj

Abstract Every year, more than 10 million pilgrims arrive in the Kingdom of Saudi Arabia for the Hajj or Umrah. Crowding conditions lead to high rates of respiratory infections among the pilgrims, representing a significant cause of morbidity and a major cause of hospitalization. Pre- and post-Hajj nasal specimens were prospectively obtained from a paired cohort (692 pilgrims) and from nonpaired cohorts (514 arriving and 470 departing pilgrims) from 13 countries. The countries of residence included Africa (44.2%), Asia (40.2%), the United States (8.4%) and Europe (7.2%). Nasal specimens were tested for 34 respiratory pathogens using RT-PCR. A total of 80 512 PCRs were performed. The prevalence of viruses and bacteria increased, from 7.4% and 15.4% before the Hajj to 45.4% and 31.0% after the Hajj, respectively, due to the acquisition of rhinovirus, coronaviruses (229E, HKU1, OC43), influenza A H1N1, Streptococcus pneumoniae, Haemophilus influenzae and Staphylococcus aureus. We did not identify Middle East respiratory coronavirus carriage. At arrival, the prevalence of several viruses was clearly dependent on the pilgrims country of origin. After Hajj participation, these viruses were isolated among pilgrims from all countries, with few exceptions. No significant differences were observed between paired and nonpaired cohort results. Our results strongly suggest that, given the particularly crowded conditions during the rituals, an international mass gathering such as the Hajj may contribute to the globalization of respiratory pathogens after the cross-contamination of pilgrims harbouring pathogens that easily spread among participants. Influenza and pneumococcal vaccination, face mask use and hand hygiene should be considered in the context of the Hajj.

Effect of rickettsial toxin VapC on its eukaryotic host.

Rickettsia are intracellular bacteria typically associated with arthropods that can be transmitted to humans by infected vectors. Rickettsia spp. can cause mild to severe human disease with a possible protection effect of corticosteroids when antibiotic treatments are initiated. We identified laterally transferred toxin-antitoxin (TA) genetic elements, including vapB/C, in several Rickettsia genomes and showed that they are functional in bacteria and eukaryotic cells. We also generated a plaque assay to monitor the formation of lytic plaques over time and demonstrated that chloramphenicol accelerates host cell lysis of vapB/C-containing Rickettsia. Whole-genome expression, TUNEL and FISH assays on the infected cells following exposure to the antibiotic revealed early apoptosis of host cells, which was linked to over-transcription of bacterial vapB/C operons and subsequent cytoplasmic VapC toxin release. VapC that is expressed in Escherichia coli and Saccharomyces cerevisiae or microinjected into mammalian cells is toxic through RNase activity and is prevented by dexamethasone. This study provides the first biological evidence that toxin–antitoxin elements act as pathogenic factors in bacterial host cells, confirming comparative genomic evidence of their role in bacterial pathogenicity. Our results suggest that early mortality following antibiotic treatment of some bacterial infections can be prevented by administration of dexamethasone.

Human leptospirosis: An emerging risk in Europe?

Leptospirosis has been reemerging in both developed and developing countries including Europe, where, this phenomenon has notably been associated with urban transmission. However, the comprehensive data that are needed to fully understand the ongoing epidemiological trends are lacking. In this article, we report surveillance data from throughout Europe, especially in France, to have an overview of this neglected disease in temperate countries. Our results underline the important role of wild rodents as reservoir of leptospirosis, and highlight the potential danger of a reemergence of this under-reported infectious disease in European cities, associated with the important expansion of the rat population in urban areas.

Bartonella, a Common Cause of Endocarditis: a Report on 106 Cases and Review

ABSTRACT Bartonella spp. are fastidious bacteria that cause blood culture-negative endocarditis and have been increasingly reported. In this study, we included all patients retrospectively and prospectively diagnosed with Bartonella endocarditis in our French reference center between 2005 and 2013. Our diagnosis was based on the modified Duke criteria and microbiological findings, including serological and PCR results. To review the published literature, we searched all human Bartonella endocarditis cases published in the PubMed database between January 2005 and October 2013. We report here a large series of 106 cases, which include 59 cases that had not previously been reported or mentioned. Indirect immunofluorescence assays, Western blotting, and real-time PCR from total blood, serum, and valve tissue exhibited sensitivities of 58%, 100%, 33%, 36%, and 91%, respectively. The number of cases reported in the literature between 2005 and 2013 increased to reach a cumulative number of 196 cases. The number of cases reported in the literature by other centers is increasing more rapidly than that reported by our French reference center (P < 10−2). Currently, there is a lack of criteria for the diagnosis of Bartonella endocarditis. We suggest that a positive PCR result from a cardiac valve or blood specimen, an IgG titer of ≥800 using an immunofluorescence assay, or a positive Western blot assay be considered major Duke criteria for Bartonella endocarditis. There is no real increase in the incidence of these infections but rather a better understanding and interest in the disease resulting from the improvement of diagnostic tools.

The Rise of Tropheryma whipplei: a 12-Year Retrospective Study of PCR Diagnoses in Our Reference Center

ABSTRACT Tropheryma whipplei is the causative agent of classic Whipples disease (WD) and other clinical entities, such as localized infection. Asymptomatic carriers have also been reported, mainly based on the testing of fecal samples. Our objective was to undertake a retrospective analysis of molecular biology usage for the diagnosis of WD over a 12-year period in our reference center. We tested 27,923 samples from 15,473 patients. The number of patients tested and the number of patients with a positive PCR result for T. whipplei have increased significantly over the last 12 years (P < 0.0001). Overall, T. whipplei was more frequently recovered from stools (43%), saliva (15%), duodenal biopsy samples (12.5%), blood (5%), and cerebrospinal fluid (CSF) (6%) and less commonly from cardiac valves (3%), urine (0.5%), skin biopsy samples (1%), lymph nodes (2.5%), aqueous humor (0.5%), and intra-articular fluid (1%). Among all the positive samples, we observed that stool samples and skin biopsy samples exhibited a higher prevalence of positivity by real-time quantitative PCR (qPCR) at 10.07% and 15.4%, respectively. The number of patients with a positive PCR result for T. whipplei has increased significantly over the last 12 years, although the positive ratio has not changed. Improvements in diagnostic tools have contributed greatly toward greater knowledge of WD and, consequently, the interest of physicians in this condition. In addition, we propose here an update of the diagnostic strategy for WD when qPCR is being used.

Emergence of human granulocytic anaplasmosis in France.

In France, only one case of tick-borne human granulocytic anaplasmosis has been described in the literature (in 2003). Here, we report 5 new human cases of Anaplasma phagocytophilum infection from north-eastern France diagnosed in our laboratory in south-eastern France by serology and molecular biology. This increase is directly related to more physician interest in this disease and the implementation of a new PCR tool.

Unique Clone of Coxiella burnetii Causing Severe Q Fever, French Guiana

Acute Q fever is an emergent and severe disease in French Guiana. We obtained 5 Coxiella burnetii isolates from samples of patients from Cayenne and found an epidemic clone circulating in Cayenne. This clone has caused pneumonia and endocarditis and seems to be more virulent than previously described strains.