Cell death induction facilitates egress of Coxiella burnetii from infected host cells at late stages of infection.

Intracellular bacteria have evolved mechanisms to invade host cells, establish an intracellular niche that allows survival and replication, produce progeny, and exit the host cell after completion of the replication cycle to infect new target cells. Bacteria exit their host cell by (i) initiation of apoptosis, (ii) lytic cell death, and (iii) exocytosis. While bacterial egress is essential for bacterial spreading and, thus, pathogenesis, we currently lack information about egress mechanisms for the obligate intracellular pathogen C. burnetii, the causative agent of the zoonosis Q fever. Here, we demonstrate that C. burnetii inhibits host cell apoptosis early during infection, but induces and/or increases apoptosis at later stages of infection. Only at later stages of infection did we observe C. burnetii egress, which depends on previously established large bacteria-filled vacuoles and a functional intrinsic apoptotic cascade. The released bacteria are not enclosed by a host cell membrane and can infect and replicate in new target cells. In summary, our data argue that C. burnetii egress in a non-synchronous way at late stages of infection. Apoptosis-induction is important for C. burnetii egress, but other pathways most likely contribute.

Molecular mechanisms of Coxiella burnetii formalin-fixed cellular vaccine reactogenicity.

Local and systemic reactogenic responses to Q-VAX have prevented licensing of this vaccine outside of Australia. These reactogenic responses occur in previously sensitized individuals and have not been well defined at the cellular level, in part because many studies have been done in guinea pigs that have limited molecular tools. We previously characterized a mouse model of reactogenicity where local reaction sites showed an influx of CD8+ and IFNγ-expressing IL17a+ CD4+ T cells consistent with a Th1 delayed-type hypersensitivity. In this study, we determined, using depletion and adoptive transfer experiments, that both anti-Coxiella antibodies and CD4+ T cells were essential for localized reactions at the site of vaccination. Furthermore, IFNγ depletion showed significant histological changes at the local reaction sites demonstrating the essential nature of this cytokine to reactogenicity. In addition to the cells and cytokines required for this response, we determined that whole cell vaccine (WCV) material remained at the site of vaccination for at least 26 weeks post-injection. Transmission electron microscopy (TEM) of these sites demonstrated intact rod-shaped bacteria at 2 weeks post-injection and partially degraded bacteria within macrophages at 26 weeks post-injection. Finally, because small cell variants (SCVs) are an environmentally stable form, we determined that local reactions were more severe when the WCV material was prepared with higher levels of SCVs compared to typical WCV or with higher levels of large cell variant (LCV). These studies support the hypothesis that antigen persistence at the site of injection contributes to this reactogenicity and that anti-Coxiella antibodies, CD4+ T cells, and IFNγ each contribute to this process.

Cross-Sectional Study of Q Fever Seroprevalence among Blood Donors, Israel, 2021.

We evaluated Q fever prevalence in blood donors and assessed the epidemiologic features of the disease in Israel in 2021. We tested serum samples for Coxeilla burnetii phase I and II IgG using immunofluorescent assay, defining a result of >200 as seropositive. We compared geographic and demographic data. We included 1,473 participants; 188 (12.7%) were seropositive. The calculated sex- and age-adjusted national seroprevalence was 13.9% (95% CI 12.2%-15.7%). Male sex and age were independently associated with seropositivity (odds ratio [OR] 1.6, 95% CI 1.1-2.2; p = 0.005 for male sex; OR 1.2, 95% CI 1.01-1.03; p<0.001 for age). Residence in the coastal plain was independently associated with seropositivity for Q fever (OR 1.6, 95% CI 1.2-2.3; p<0.001); residence in rural and farming regions was not. Q fever is highly prevalent in Israel. The unexpected spatial distribution in the nonrural coastal plain suggests an unrecognized mode of transmission.

Serosurveillance of Coxiella burnetii in feral swine populations of Hawai'i and Texas identifies overlap with human Q fever incidence.

Feral swine are invasive in the United States and a reservoir for infectious diseases. The increase in feral swine population and the geographic range are a concern for the spread of zoonotic diseases to humans and livestock. Feral swine could contribute to the spread of Coxiella burnetii, the causative agent of human Q fever. In this study, we characterized the seroprevalence of C. burnetii in feral swine populations of Hawai'i and Texas, which have low and high rates of human Q fever, respectively. Seropositivity rates were as high as 0.19% and 6.03% in Hawai'i and Texas, respectively, indicating that feral swine cannot be ruled out as a potential reservoir for disease transmission and spread. In Texas, we identified the overlap between seropositivity of feral swine and human Q fever incidence. These results indicate that there is a potentially low but detectable risk of C. burnetii exposure associated with feral swine populations in Hawai'i and Texas.

The integration of Coxiella burnetii PCR testing in serum into the diagnostic algorithm of suspected acute Q fever in an endemic setting.

Serum polymerase chain reaction (PCR) for the detection of Coxiella burnetii DNA has been suggested for rapid Q fever diagnosis. We evaluated the role of PCR testing in serum in the diagnosis of acute Q fever in an endemic setting. We examined patients suspected of acute Q fever tested for C. burnetii-specific serum real-time PCR in a tertiary hospital between January 2019 toand December 2022. In the first half, PCR orders were consultation-based by infectious diseases specialists, while in the second half, they were guided by serology, positive IgM2, and negative IgG1 and IgG2, indicating early acute infection. Logistic regression analyzed independent predictors for positive PCR. PCR positivity rates were calculated using various clinical criteria in the diagnostic algorithm. Out of 272 patients, 13 (4.8%) tested positive and 130 exhibited serologically suspected early infection. Presentation during April-July and aspartate aminotransferase (AST) > 3× upper normal limit (UNL) were independently associated with positive PCR with an odds ratio (OR) = 15.03 [95% confidence interval (CI), 1.58-142.46], P = 0.018 and OR = 55.44 [95% CI, 6.16-498.69], P < 0.001, respectively. PCR positivity rate was 8.5% in serologically suspected early infection vs 1.4% in other serology, yielding OR = 6.4 [95% CI, 1.4-29.7], P = 0.009. Adding AST > 3× UNL increased OR to 49.5 [95% CI, 5.9-408.7], P ≤ 0.001 reducing required PCR tests for a single acute Q fever case from 11.8 to 3. Elevated AST in serologically suspected early Q fever is proposed to be used in a diagnostic stewardship algorithm integrating PCR in serum in an endemic setting. IMPORTANCE: Our study suggests in a diagnostic stewardship approach the integration of molecular testing (Coxiella burnetii targeted PCR) for the diagnosis of acute Q fever in a reliable time in the endemic setting. Integrating PCR detecting Coxiella burnetii in serum in routine testing of suspected early acute Q fever based on serology result increased the PCR positivity rate significantly. Adding increased transaminases optimizes PCR utility which is highly requested particularly in endemic areas.

Embracing multiple infection models to tackle Q fever: A review of in vitro, in vivo, and lung ex vivo models.

Multiple animal and cell culture models are employed to study pathogenesis of Coxiella burnetii, the causative agent of acute and chronic human Q fever. C. burnetii is a lung pathogen that is aerosolized in contaminated products and inhaled by humans to cause acute disease that can disseminate to other organs and establish chronic infection. Cellular models of Q fever include a variety of tissue-derived cell lines from mice and humans such as lung alveolar ex vivo cells. These models have the advantage of being cost-effective and reproducible. Similarly, animal models including mice and guinea pigs are cost-effective, although only immunocompromised SCID mice display a severe disease phenotype in response to Nine Mile I and Nine Mile II isolates of C. burnetii while immunocompetent guinea pigs display human-like symptoms and robust immune responses. Non-human primates such as macaques and marmosets are the closest model of human disease but are costly and largely used for adaptive immune response studies. All animal models are used for vaccine development but many differences exist in the pathogen's ability to establish lung infection when considering infection routes, bacterial isolates, and host genetic background. Similarly, while cellular models are useful for characterization of host-pathogen mechanisms, future developments should include use of a lung infection platform to draw appropriate conclusions. Here, we summarize the current state of the C. burnetii lung pathogenesis field by discussing the contribution of different animal and cell culture models and include suggestions for continuing to move the field forward.

Prevalence and risk factors for Q fever, spotted fever group rickettsioses, and typhus group rickettsioses in a pastoralist community of northern Tanzania, 2016-2017.

BACKGROUND: In northern Tanzania, Q fever, spotted fever group (SFG) rickettsioses, and typhus group (TG) rickettsioses are common causes of febrile illness. We sought to describe the prevalence and risk factors for these zoonoses in a pastoralist community. METHODS: Febrile patients ≥2 years old presenting to Endulen Hospital in the Ngorongoro Conservation Area were enrolled from August 2016 through October 2017. Acute and convalescent blood samples were collected, and a questionnaire was administered. Sera were tested by immunofluorescent antibody (IFA) IgG assays using Coxiella burnetii (Phase II), Rickettsia africae, and Rickettsia typhi antigens. Serologic evidence of exposure was defined by an IFA titre ≥1:64; probable cases by an acute IFA titre ≥1:128; and confirmed cases by a ≥4-fold rise in titre between samples. Risk factors for exposure and acute case status were evaluated. RESULTS: Of 228 participants, 99 (43.4%) were male and the median (interquartile range) age was 27 (16-41) years. Among these, 117 (51.3%) had C. burnetii exposure, 74 (32.5%) had probable Q fever, 176 (77.2%) had SFG Rickettsia exposure, 134 (58.8%) had probable SFG rickettsioses, 11 (4.8%) had TG Rickettsia exposure, and 4 (1.8%) had probable TG rickettsioses. Of 146 participants with paired sera, 1 (0.5%) had confirmed Q fever, 8 (5.5%) had confirmed SFG rickettsioses, and none had confirmed TG rickettsioses. Livestock slaughter was associated with acute Q fever (adjusted odds ratio [OR] 2.54, 95% confidence interval [CI] 1.38-4.76) and sheep slaughter with SFG rickettsioses case (OR 4.63, 95% CI 1.08-23.50). DISCUSSION: Acute Q fever and SFG rickettsioses were detected in participants with febrile illness. Exposures to C. burnetii and to SFG Rickettsia were highly prevalent, and interactions with livestock were associated with increased odds of illness with both pathogens. Further characterisation of the burden and risks for these diseases is warranted.

Delayed diagnosis of persistent Q fever: a case series from China.

BACKGROUND: Q fever, caused by the zoonotic pathogen Coxiella burnetii, exhibits a worldwide prevalence. In China, Q fever is not recognized as a notifiable disease, and the disease is overlooked and underestimated in clinical practice, leading to diagnostic challenges. CASE PRESENTATION: We present a case series of three patients diagnosed with persistent Q fever between 2022 and 2023. The average age of our three cases was 63.33 years old, consisting of two males and one female. The medical history of the individuals included previous valve replacement, aneurysm followed by aortic stent-graft placement and prosthetic hip joint replacement. At the onset of the disease, only one case exhibited acute fever, while the remaining two cases were devoid of any acute symptoms. The etiology was initially overlooked until metagenomic next-generation sequencing test identified Coxiella burnetii from the blood or biopsy samples. Delayed diagnosis was noted, with a duration ranging from three months to one year between the onset of the disease and its confirmation. The epidemiological history uncovered that none of the three cases had direct exposure to domestic animals or consumption of unpasteurized dairy products. Case 1 and 2 resided in urban areas, while Case 3 was a rural resident engaged in farming. All patients received combination therapy of doxycycline and hydroxychloroquine, and no recurrence of the disease was observed during the follow-up period. CONCLUSION: Q fever is rarely diagnosed and reported in clinical practice in our country. We should be aware of persistent Q fever in high-risk population, even with unremarkable exposure history. Metagenomic next-generation sequencing holds great potential as a diagnostic tool for identifying rare and fastidious pathogens such as Coxiella burnetii.

The epidemiological and infectious characteristics of novel types of Coxiella burnetii co-infected with Coxiella-like microorganisms from Xuyi County, Jiangsu province, China.

Coxiella burnetii (C. burnetii) is the causative agent of Q fever, a type of zoonoses withwidespread distribution. In 2019, a case of Q fever was diagnosed by metagenomic next-generation sequencing (mNGS) method in Xuyi County (Jiangsu province, China). The seroprevalence of previous fever patients and the molecular epidemiology of Coxiella in wild hedgehogs and harbouring ticks around the confirmed patient were detected to reveal the genetic characteristics and pathogenicity of the Coxiella strains. Four of the 90 serum samples (4.44%) were positive for specific C. burnetii IgM antibody, suggesting that local humans are at risk of Q fever. The positive rates of C. burnetii in hedgehogs and ticks were 21.9% (7/32) and 70.5% (122/173), respectively. At least 3 strains of Coxiella were found prevalent in the investigated area, including one new genotype of pathogenic C. burnetii (XYHT29) and two non-pathogenic Coxiella-like organisms (XYHT19 and XYHT3). XYHT29 carried by ticks and wild hedgehogs successfully infected mice, imposing a potential threat to local humans. XYHT19, a novel Coxiella-like microorganism, was first discovered in the world to co-infect with C. burnetii in Haemaphysalis flava. The study provided significant epidemic information that could be used for prevention and control strategies against Q fever for local public health departments and medical institutions.

Q fever endocarditis of the tricuspid valve transmitted in an urban setting with no livestock exposure: Case report.

BACKGROUND: Coxiella burnetii is a bacterium with extreme tenacity and contagiousness that is mainly transmitted by inhalation of contaminated aerosols. Nevertheless, a transmission by ticks is under discussion. We report a case of Q fever in an urban environment and far away from sheep breeding that caused a rare right-sided endocarditis. CASE PRESENTATION: A 55-year-old man who was in good health before the event developed a C. burnetii -endocarditis of the tricuspid valve. He had no contact with sheep and no recent travel in a rural or even endemic area. The infection originated in a strictly urban environment, and the patient's occupation as a cemetery gardener in Berlin, coupled with the close temporal and local exposure to wild boar, made a transmission by these animals a plausible hypothesis. The infection was confirmed by the German Reference Laboratory, and the patient recovered completely after treatment with doxycycline and hydrochlorquine. CONCLUSIONS: The specialities of this case report are the right-sided endocarditis and the transmission of C. burnetii in a metropolitan area without sheep contact. We think that this case should serve to increase awareness of the potential for Q fever infection even in non-rural areas.

Acute Q fever in individuals with acute febrile illness & exposure to farm animals: Clinical manifestations & diagnostic approaches.

Background & objectives Q fever is an important zoonotic disease affecting humans as well as animals. The objective of this study was to assess the burden of Q fever in individuals with acute febrile illness, particularly those in close contact with animals. Various diagnostic methods were also evaluated in addition to clinical examination analysis and associated risk factors. Methods Individuals presenting with acute febrile illness who had animal exposure were enrolled (n=92) in this study. Serum samples were tested using IgG and IgM phase 2 enzyme linked immunosorbent assay (ELISA) and immunofluorescence assay (IFA). The PCR targeting the com1 and IS1111 genes was performed on blood samples. PCR amplicons were sequenced and phylogenetically analysed. Demographic data, symptoms, and risk factors were collected through a structured questionnaire. Results Among individuals with acute febrile illness, 34.7 per cent (32 out of 92) were found to be infected with Coxiella burnetii. PCR exhibited the highest sensitivity among the diagnostic methods employed. The most common clinical manifestations included headache, chills, arthralgia, and fatigue. Individuals engaged in daily livestock-rearing activities were found to be at an increased risk of infection. Interpretation & conclusions Q fever is underdiagnosed due to its varied clinical presentations, diagnostic complexities, and lack of awareness. This study underscores the importance of regular screening for Q fever in individuals with acute febrile illness, particularly those with animal exposure. Early diagnosis and increased awareness among healthcare professionals are essential for the timely management and prevention of chronic complications associated with Q fever.

Case report: membranoproliferative glomerulonephritis associated with Q fever causing chronic endocarditis.

BACKGROUND: Membranoproliferative glomerulonephritis is a rare entity which can be a result from autoimmune diseases, caused by various medications and infections. CASE PRESENTATION: We herein present the case of a 62-year-old male patient who presented with fatigue and was found to have severe anemia, impaired renal function, and nephrotic syndrome. A renal biopsy revealed membranoproliferative glomerulonephritis (MPGN) of the immune complex type with activation of the classical complement pathway. Further investigations led to the diagnosis of a chronic Coxiella burnetii-infection (Q fever), likely acquired during cycling trips in a region known for intensive sheep farming. Additionally, the patient was found to have a post endocarditic destructive bicuspid aortic valve caused by this pathogen. Treatment with hydroxychloroquine and doxycycline was administered for a duration of 24 months. The aortic valve was replaced successfully and the patient recovered completely. CONCLUSIONS: Early detection and targeted treatment of this life-threatening disease is crucial for complete recovery of the patient.

Occupational exposure to Coxiella burnetii during cardiac surgery: A case report and review of the literature.

We report a case of exposure to Coxiella burnetii in a surgical nurse who underwent an injury of her finger with a scalpel blade during a native aortic valve replacement with a bio-prosthetic cardiac valve conducted on a patient suffering from C. burnetii aortic endocarditis. Given the positivity of C. burnetii culture and PCR from the patient's aortic valve, she was prescribed prophylactic doxycycline 100 mg twice a day for 10 days. Q fever is an occupational zoonosis resulting usually of exposure to infected animals by inhalation of infected aerosols or consumption of contaminated raw milk. Apart from materno-foetal transmission, about 180 cases of human-to-human C. burnetii transmission have been published from 1949 to today, including transmission by blood transfusion, sexual relations, transmission in the healthcare setting to staff, patient attendants and other patients that were likely infected from inhalation of aerosol from respiratory or placental products, transmission to staff during autopsies of patients with Q fever and transmission in familial settings. As C. burnetii is a highly infectious bacterium, that may cause infection with a low inoculum, it should be added to the list of organisms which may be of concern following blood exposure among healthcare professionals.

Epidemiology of Q fever in humans in four selected regions, Spain, 2016 to 2022.

BackgroundQ fever is a bacterial zoonosis caused by Coxiella burnetii. Spain has the highest number of notified human cases in Europe. Small ruminants are a key reservoir for the pathogen, transmission from animals to humans is usually airborne.AimWe aimed at exploring temporal and spatial epidemiological patterns of sporadic and outbreak cases of Q fever in four Spanish regions with the highest number of notified cases.MethodsWe extracted data on Q fever cases in the Canary Islands, Basque Country, La Rioja and Navarre between 2016 and 2022 from the Spanish National Epidemiological Surveillance Network. We calculated standardised incidence ratios (SIR), spatial relative risks (sRR) and posterior probabilities (PP) utilising Besag-York-Mollié models.ResultsThere were 1,059 notifications, with a predominance of males aged 30-60 years. In Basque Country, La Rioja and Navarre area, 11 outbreaks were reported, while no in the Canary Islands. A seasonal increase in incidence rates was observed between March and June. In the Canary Islands, elevated sRR was seen in La Palma, Gran Canaria, Lanzarote and Fuerteventura. In Basque Country, La Rioja and Navarre area, the highest sRR was identified in the south of Biscay province.ConclusionGoats were the main source for humans in outbreaks reported in the literature. Seasonal increase may be related to the parturition season of small ruminants and specific environmental conditions. Local variations in sRR within these regions likely result from diverse environmental factors. Future One Health-oriented studies are essential to deepen our understanding of Q fever epidemiology.

Molecular detection of Coxiella burnetii in tick and blood samples from small ruminants in northwest of Iran.

This survey sought to molecularly detect Coxiella burnetii in Argasidae and Ixodidae ticks attached to small ruminants in the region of West Azerbaijan (Northwest of Iran) and blood samples collected from the same animals. 451 tick samples and 927 blood samples were obtained from sheep (n = 536) and goats (n = 391) and tested by nested PCR for detection of C. burnetii insertion sequence IS1111 or icd gene sequence. The collected ticks were morphologically classified as Rhipicephalus sanguineus, Rhipicephalus turanicus, Hyalomma asiaticum, Hyalomma anatolicum, or Argas reflexus. 14% of ticks (65 in total 43 for IS1111 and 22 for icd gene) tested positive for C. burnetii, none of which were from the Argas genus. Among the 927 blood samples, 218 (23.5%) tested positive for C. burnetii. The positive result from analysis targeting the genes IS1111 and icd were 131 and 87 respectively. As Q fever is a tickborne zoonosis and endemic to Iran, such information is critical for creating effective, coordinated, and strategic tick and pathogen control programs to prevent disease outbreak in domestic animals and humans.

Molecular detection of Coxiella burnetii in blood and hard tick-infested Egyptian camels and the possibility of coinfections.

Coxiella burnetii, a bacterium that causes Q fever. It can infect mammals and has a global geographical distribution, but data on its occurrence in Egyptian dromedaries and the associated ticks are limited. Therefore, this study aims to detect C. burnetii in the blood of infested camels and associated ticks collected from Egypt by using molecular techniques and to examine the possibility of coinfections with C. burnetii. A total of 133 blood samples and 1260 hard ticks infesting these camels were collected from Egyptian slaughterhouses. Nested PCR and sequencing were used based on the IS1111 gene for molecular detection of C. burnetii. The identification of tick species at the molecular level was performed using the COX1 gene. C. burnetii was detected in Hyalomma (H) dromedarii, H. anatolicum, H. marginatum, Amblyomma (Am) lipidium, and Am. cohaerens with an overall prevalence rate of 1.3% (16/1260), while in the camel blood samples, it was 15.8% (21/133). Out of C. burnetii-positive ticks, there were double infections by Borrelia species and C. burnetii in H. dromedarii and Am. lipidium and triple infections at one Am. cohaerens tick (C. burnetii, Borrelia spp., and Babesia microti). In addition, two positive camel blood samples were found to carry C. burnetii with Borrelia spp. Our research findings indicate the presence of Coxiella burnetii among camels and their associated ticks in Egypt and emphasize the potential of having coinfection. To prevent the transmission of this infection to other animal species or humans, appropriate control measures should be implemented.

Prevalence and associated risk factors of anti-Coxiella burnetii antibodies in dairy cattle herds using bulk tank milk analysis in Kabylia area, north Algeria.

Coxiella burnetii, or Q fever agent, has notable implications for human and livestock health. Infections in cattle primarily manifest through reproductive issues where infected animals shed the bacterium in birth fluids, placental tissues, and milk, serving as potential sources of transmission. Bovine herds become reservoirs, contributing to the environmental contamination of farming areas. Comprehensive studies on the prevalence, transmission routes, and associated risk factors among cattle contribute to the development of effective control strategies, ultimately safeguarding both livestock and public health.Here we determine the prevalence of Coxiella burnetii antibodies against in dairy cattle farms from Kabylia (northern Algeria) and identify the associated risk factors. Bulk tank milk samples from 184 farms were analyzed by indirect ELISA technique, 49 of them were tested positive which corresponds to a prevalence rate of 26.63% (95% CI 20.25-33.01%). Multivariate analysis by logistic regression showed that the risk factors associated with detection of anti-Coxiella burnetii antibodies are: cohabitation of cattle with small ruminants(OR = 3.74 95% CI [1.41-8.92]), exposure to prevailing winds (OR = 5.12 95% CI [2.11-13.45]), and the veterinarian visits frequency(OR = 5.67 95% CI [2.55-13.60]). These findings underscore the susceptibility of dairy cattle to Q fever in the Kabylia region, highlighting practices that pose risks. We recommend the implementation of hygienic measures and adherence to proper farming conditions to mitigate the transmission of Q fever and reduce the associated zoonotic risk.

Bivalvular Endocarditis Due to Polymicrobial Coinfection with Enterococcus faecalis and Coxiella burnetii: A Case Report and Review of the Literature.

Polymicrobial endocarditis is uncommon, and polymicrobial endocarditis in combination with Coxiella burnetii is very rare. We herein describe an extremely rare case of polymicrobial bivalvular endocarditis due to coinfection with Enterococcus faecalis and Coxiella burnetii in a 62-year-old male patient, and extensively review the relevant medical literature. To the best of our knowledge, only three similar cases have been previously reported. Q fever is a worldwide endemic bacterial zoonosis, but it and its most common chronic complication, endocarditis, are still underestimated and underdiagnosed worldwide. This situation reflects the paucity of reported cases of polymicrobial endocarditis in combination with Coxiella burnetii. Clinical presentation of Q fever endocarditis is highly nonspecific, and diagnosis may be delayed or missed, leading to severe and potentially fatal disease. Our case and the previously reported similar cases emphasize the need for further evaluation of infective endocarditis due to Coxiella burnetii, in all cases of culture-negative endocarditis, and in prolonged oligo-symptomatic inflammatory syndrome, particularly in the presence of valvular heart disease. This approach should be applied even when typical pathogens are isolated, especially in endemic areas of Q fever, and with atypical presentation.

Spinning sugars in antigen biosynthesis: characterization of the Coxiella burnetii and Streptomyces griseus TDP-sugar epimerases.

The sugars streptose and dihydrohydroxystreptose (DHHS) are unique to the bacteria Streptomyces griseus and Coxiella burnetii, respectively. Streptose forms the central moiety of the antibiotic streptomycin, while DHHS is found in the O-antigen of the zoonotic pathogen C. burnetii. Biosynthesis of these sugars has been proposed to follow a similar path to that of TDP-rhamnose, catalyzed by the enzymes RmlA, RmlB, RmlC, and RmlD, but the exact mechanism is unclear. Streptose and DHHS biosynthesis unusually requires a ring contraction step that could be performed by orthologs of RmlC or RmlD. Genome sequencing of S. griseus and C. burnetii has identified StrM and CBU1838 proteins as RmlC orthologs in these respective species. Here, we demonstrate that both enzymes can perform the RmlC 3'',5'' double epimerization activity necessary to support TDP-rhamnose biosynthesis in vivo. This is consistent with the ring contraction step being performed on a double epimerized substrate. We further demonstrate that proton exchange is faster at the 3''-position than the 5''-position, in contrast to a previously studied ortholog. We additionally solved the crystal structures of CBU1838 and StrM in complex with TDP and show that they form an active site highly similar to those of the previously characterized enzymes RmlC, EvaD, and ChmJ. These results support the hypothesis that streptose and DHHS are biosynthesized using the TDP pathway and that an RmlD paralog most likely performs ring contraction following double epimerization. This work will support the elucidation of the full pathways for biosynthesis of these unique sugars.

New Genotype of Coxiella burnetii Causing Epizootic Q Fever Outbreak in Rodents, Northern Senegal.

In Senegal, Coxiella burnetii, which causes Q fever, has often been identified in ticks and humans near livestock, which are considered to be reservoirs and main sources of infection. We describe the emergence of C. burnetii in rodents, not previously known to carry this pathogen, and describe 2 new genotypes.