Wild rodent fleas carrying Bartonella and Rickettsia in an area endemic for vector-borne diseases from Argentina.

Vector-borne diseases account for nearly 20% of all globally recognised infectious diseases. Within the spectrum of flea-borne pathogens, Bartonella and Rickettsia bacteria are prominent, contributing to the emergence and resurgence of diseases on a global scale. This study investigates the presence of species of Bartonella and Rickettsia harboured by fleas collected from wild rodents in northwestern Argentina (NWA). A total of 28 fleas from three genera and seven species were assessed. DNA of Bartonella and Rickettsia spp. was found in 12 fleas (42.8%). Phylogenetic analysis of concatenated sequences of gltA and rpoB genes showed the presence of Bartonella quintana in eight fleas of two species, Craneopsylla minerva minerva and Polygenis acodontis. Phylogenetic analysis of concatenated sequences of gltA, ompA and ompB genes identified Rickettsia felis in ten fleas of five species, C. m. minerva, P. acodontis, Polygenis bohlsi bohlsi, Polygenis byturus and Tiamastus palpalis. These bacterial species mark the first report in all flea species studied. This study represents the first survey of flea-borne bacteria for NWA. The results provide information to address strategies for the control and prevention of bartonellosis and rickettsiosis that could have an impact on public health in one of the geographical areas of Argentina with the highest incidence of infections transmitted to humans by ectoparasites.

Bartonella quintana detection among arthropods and their hosts: a systematic review and meta-analysis.

BACKGROUND: Bartonella quintana is a body louse-borne bacterium causing bacteremia and infective endocarditis. We aimed to describe B. quintana detection among arthropods and their hosts. METHODS: We searched databases in PubMed Central/MEDLINE, Scopus, Embase, and Web of Science from January 1, 1915 (the year of B. quintana discovery) to January 1, 2024, to identify publications containing specific search terms relating to B. quintana detection among arthropods. Descriptive statistics and meta-analysis of pooled prevalence using random-effects models were performed for all arthropods and body and head lice. RESULTS: Of 1265 records, 62 articles were included, describing 8839 body lice, 4962 head lice, and 1692 other arthropods, such as different species of fleas, bedbugs, mites, and ticks. Arthropods were collected from 37 countries, of which 28 had arthropods with B. quintana DNA. Among articles that reported B. quintana detection among individual arthropods, 1445 of 14,088 (0.1026, 95% CI [0.0976; 0.1077]) arthropods tested positive for B. quintana DNA, generating a random-effects model global prevalence of 0.0666 (95% CI [0.0426; 0.1026]). Fifty-six studies tested 8839 body lice, of which 1679 had B. quintana DNA (0.1899, 95% CI [0.1818; 0.1983]), generating a random-effects model pooled prevalence of 0.2312 (95% CI [0.1784; 0.2843]). Forty-two studies tested 4962 head lice, of which 390 head lice from 20 studies originating from 11 different countries had B. quintana DNA (0.0786, 95% CI [0.0713; 0.0864]). Eight studies detected B. quintana DNA exclusively on head lice. Five studies reported greater B. quintana detection on head lice than body lice; all originated from low-resource environments. CONCLUSIONS: Bartonella quintana is a vector-borne bacterium with a global distribution, disproportionately affecting marginalized populations. Bartonella quintana DNA has been detected in many different arthropod species, though not all of these arthropods meet criteria to be considered vectors for B. quintana transmission. Body lice have long been known to transmit B. quintana. A limited number of studies suggest that head lice may also act as possible vectors for B. quintana in specific low-resource contexts.

Bartonella quintana pulmonary native valve endocarditis.

Bartonella quintana is a well-known cause of blood culture-negative endocarditis; however, pulmonary valve involvement is rare. The case of a 40-year-old African male who presented to the Emergency Department with chest pain, cardiac failure, and a 2-week history of fever is presented. Transoesophageal echocardiography confirmed an atrial septal defect, severe pulmonary insufficiency with large vegetations, severe mitral regurgitation due to anterior leaflet prolapse, and right ventricular dysfunction. Empirical antibiotic therapy was started, and urgent surgical intervention was decided. There were vegetations on the three pulmonary valve leaflets and the mitral valve. Closure of the atrial septal defect, mitral and tricuspid valve repair, pulmonary valve replacement with a biological prosthesis, and infundibuloplasty of the right ventricle were performed. The postoperative course was uneventful. Preoperative blood cultures were negative, and B. quintana was detected through 16S rRNA gene amplification and sequencing in mitral and pulmonary implants. Serology showed positive titers of 1/1260 for both B. quintana and B. henselae. Ceftriaxone and gentamicin were administered for 10 days, followed by oral doxycycline for 12 weeks. A one-year echocardiogram showed normal functioning of the pulmonary prosthesis and the mitral and tricuspid repair. Infection caused by B. quintana is a rare cause of endocarditis with negative blood cultures, and multivalvular and pulmonary valve involvement is exceptional. Supplementary Information: The online version contains supplementary material available at 10.1007/s12055-024-01727-4.

Knowledge and practices related to louse- and flea-borne diseases among staff providing services to people experiencing homelessness in the United States.

BACKGROUND AND AIMS: Louse-borne Bartonella quintana infection and flea-borne murine typhus are two potentially serious vector-borne diseases that have led to periodic outbreaks among people experiencing homelessness in the United States. Little is known about louse- and flea-borne disease awareness and prevention among staff who provide services to the population. We surveyed staff in seven US states to identify gaps in knowledge and prevention practices for these diseases. METHODS AND RESULTS: Surveys were administered to 333 staff at 89 homeless shelters and outreach teams in California, Colorado, Georgia, Maryland, Minnesota, New York and Washington from August 2022 to April 2023. Most participants (>68%) agreed that body lice and fleas are a problem for people experiencing homelessness. About half were aware that diseases could be transmitted by these vectors; however, most could not accurately identify which diseases. Less than a quarter of staff could describe an appropriate protocol for managing body lice or fleas. Misconceptions included that clients must isolate or be denied services until they are medically cleared. CONCLUSIONS: Our findings reveal significant knowledge gaps among staff who provide services to people experiencing homelessness in the prevention and control of louse- and flea-borne diseases. This demonstrates an urgent need for staff training to both reduce disease and prevent unnecessary restrictions on services and housing.

Genomic detection and phylogenetic analysis of Bartonella quintana in pet cats from Urmia City, Northwest Iran.

The aim of this study was to investigate the presence and genetic characteristics of Bartonella quintana in pet cats from Urmia City, located in the northwest of Iran. Blood samples were collected from 200 cats, and their age, gender, and breed were noted. Nested-PCR and sequencing were used to identify B. quintana in positive samples, and the ftsZ gene sequences were analyzed using BioEdit software. The gene sequence obtained in this study exhibited 100.00 % similarity to reference sequences in the GenBank® database, and a phylogenetic tree was constructed using MEGA11. The results revealed that 15 % of the cats (30 out of 200 blood samples) tested positive for the B. quintana gene, with a 95 % confidence interval of 10.71 % to 20.61 %.

Molecular detection of Bartonella quintana, Acinetobacter baumannii and Acinetobacter haemolyticus in Pediculus humanus lice in Nigeria, West Africa.

The human lice Pediculus humanus is distributed worldwide but, it thrives and flourishes under conflict situations where people are forced to live in crowded unhygienic conditions. Molecular methods were used to identify and screen human lice for the DNA of pathogens of public health importance in an area that has been under insurgency related to religious and political conflicts with tens of thousands of internally displaced people (IDP). DNA of Bartonella quintana, Acinetobacter baumannii and Acinetobacter haemolyticus was detected in 18.3%, 40.0% and 1.7%, respectively, of human lice collected from children in Maiduguri, Nigeria. More body lice than head lice were positive for pathogen's DNA (64.3% vs. 44.4%; χ2 = 1.3, p = 0.33), but the difference was not significant. Two lice samples were found to harbour mixed DNA of B. quintana and A. baumannii. Phylogenetic analysis of the cytochrome b (cytb) gene sequences of the positive lice specimens placed them into clades A and E. This is the first report on the molecular identification of human lice and the detection of the DNA of pathogens of public health importance in lice in Nigeria, West Africa. The findings of this study will assist policy makers and medical practitioners in formulating a holistic healthcare delivery to IDPs.

Presumed acute posterior multifocal placoid pigmentary epitheliopathy associated with Bartonella infection / Epiteliopatia pigmentar placoide multifocal posterior aguda presumível associada com infecção por Bartonella

ABSTRACT To report a unique case of acute posterior multifocal placoid pigment epitheliopathy (APMPPE) in a patient with positive serology for Bartonella, presenting with ocular signs and symptoms not attributable to other diseases. A 27-year-old woman presented with decreased visual acuity in both eyes. Multimodal fundus image analysis was performed. A color fundus photograph of both eyes revealed peripapillary and macular yellow-white placoid lesions. The fundus autofluorescence of both eyes demonstrated hypo- and hyperautofluorescence of the macular lesions. Fluorescein angiography showed early-stage hypofluorescence and late staining of placoid lesions in both eyes. Spectral domain optical coherence tomography (SD-OCT) of both eyes revealed irregular elevations in the retinal pigment epithelium with the disruption of the ellipsoid zone on the topography of macular lesions. At 3 months after the treatment initiation for Bartonella infection, the placoid lesions became atrophic and hyperpigmented, and SD-OCT revealed loss of both the outer retinal layers and retinal pigment epithelium on the topography of macular lesions in both eyes.

RESUMO Caso de epiteliopatia pigmentada placoide multifocal posterior aguda presumida em paciente com sorologia positiva para Bartonella. Paciente feminina de 27 anos apresentou diminuição da acuidade visual em ambos os olhos. Análise multimodal de imagem foi realizada. A retinografia mostrou revelou lesões placoides amarelo-esbranquiçadas nas áreas peripapilar e macular de ambos os olhos. A autofluorescência demonstrou hipo e hiperautofluorescência em ambos os olhos, na mesma topografia das lesões detectadas na retinografia. A angiofluoresceínografia mostrou hipofluorescência na fase inicial do exame e hiperfluorescência tardia das lesões placoides em ambos os olhos. A tomografia de coerência óptica de domínio espectral de ambos os olhos revelou elevações irregulares do epitélio pigmentado da retina com descontinuação da zona elipsoide na área macular. Três meses após o início do tratamento para infecção por Bartonella, as lesões placoides tornaram-se atróficas e hiperpigmentadas, e a tomografia de coerência óptica revelou perda das camadas externas da retina e do epitélio pigmentado da retina na topografia das lesões maculares em ambos os olhos.

In silico identification of drug targets and vaccine candidates against Bartonella quintana: a subtractive proteomics approach

BACKGROUND The availability of genes and protein sequences for parasites has provided valuable information for drug target identification and vaccine development. One such parasite is Bartonella quintana, a Gram-negative, intracellular pathogen that causes bartonellosis in mammalian hosts. OBJECTIVE Despite progress in understanding its pathogenesis, limited knowledge exists about the virulence factors and regulatory mechanisms specific to B. quintana. METHODS AND FINDINGS To explore these aspects, we have adopted a subtractive proteomics approach to analyse the proteome of B. quintana. By subtractive proteins between the host and parasite proteome, a set of proteins that are likely unique to the parasite but absent in the host were identified. This analysis revealed that out of the 1197 protein sequences of the parasite, 660 proteins are non-homologous to the human host. Further analysis using the Database of Essential Genes predicted 159 essential proteins, with 28 of these being unique to the pathogen and predicted as potential putative targets. Subcellular localisation of the predicted targets revealed 13 cytoplasmic, eight membranes, one periplasmic, and multiple location proteins. The three-dimensional structure and B cell epitopes of the six membrane antigenic protein were predicted. Four B cell epitopes in KdtA and mraY proteins, three in lpxB and BQ09550, whereas the ftsl and yidC proteins were located with eleven and six B cell epitopes, respectively. MAINS CONCLUSIONS This insight prioritises such proteins as novel putative targets for further investigations on their potential as drug and vaccine candidates.

Evidence for Bartonella quintana in Lice Collected from the Clothes of Ethiopian Homeless Individuals.

Human lice, Pediculus humanus, can transmit various pathogens, including Bartonella quintana, Borrelia recurrentis, and Rickettsia prowazekii. Xenosurveillance is an epidemiological approach to assessing human infection risks performed by screening vectors of infectious disease agents. In the proof-of-principle study reported herein, the DNA of 23 human lice was collected from the clothes of 30 homeless Ethiopian individuals. These samples were assessed using 16S rRNA gene-specific pan-eubacterial PCR for screening, followed by Bartonella genus 16S-23S internal transcribed spacer (ITS) sequence-specific PCR, Bartonella genus gltA gene-specific PCR, and 16S rRNA gene PCR with specificity for relapsing-fever-associated Borrelia spp. with subsequent sequencing of the amplicons. In one sample, the pan-eubacterial 16S rRNA gene-specific screening PCR, the Bartonella genus 16S-23S ITS sequence-specific PCR, and the Bartonella genus gltA gene-specific PCR allowed for the sequencing of B. quintana-specific amplicons. In two additional samples, Bartonella genus gltA gene-specific PCR also provided sequences showing 100% sequence identity with B. quintana. In total, 3/23 (13.0%) of the assessed lice were found to be positive for B. quintana. Correlating clinical data were not available; however, the assessment confirmed the presence of B. quintana in the local louse population and thus an associated infection pressure. Larger-sized cross-sectional studies seem advisable to more reliably quantify the infection risk of lice-infested local individuals. The need for prevention by providing opportunities to maintain standard hygiene for Ethiopian homeless individuals is stressed by the reported findings, especially in light of the ongoing migration of refugees.

Exploring the potential role of defensins in differential vector competence of body and head lice for Bartonella quintana.

BACKGROUND: The body and head lice of humans are conspecific, but only the body louse functions as a vector to transmit bacterial pathogens such as Bartonella quintana. Both louse subspecies have only two antimicrobial peptides, defensin 1 and defensin 2. Consequently, any differences in the molecular and functional properties of these two louse subspecies may be responsible for the differential vector competence between them. METHODS: To elucidate the molecular basis of vector competence, we compared differences in the structural properties and transcription factor/microRNA binding sites of the two defensins in body and head lice. Antimicrobial activity spectra were also investigated using recombinant louse defensins expressed via baculovirus. RESULTS: The full-length amino acid sequences of defensin 1 were identical in both subspecies, whereas the two amino acid residues in defensin 2 were different between the two subspecies. Recombinant louse defensins showed antimicrobial activities only against the representative Gram-positive Staphylococcus aureus but not against either Gram-negative Escherichia coli or the yeast Candida albicans. However, they did show considerable activity against B. quintana, with body louse defensin 2 being significantly less potent than head louse defensin 2. Regulatory sequence analysis revealed that the gene units of both defensin 1 and defensin 2 in body lice possess decreased numbers of transcription factor-binding sites but increased numbers of microRNA binding sites, suggesting relatively lower transcription activities of body louse defensins. CONCLUSIONS: The significantly lower antibacterial activities of defensin 2 along with the reduced probability of defensin expression in body lice likely contribute to the relaxed immune response to B. quintana proliferation and viability, resulting in higher vector competence of body lice compared to head lice.

Molecular epidemiology of Bartonella quintana endocarditis in patients from Israel and Eastern Africa.

BACKGROUND: Bartonella quintana is an important cause of culture-negative endocarditis. Although humans have been considered as its only reservoir, recent studies showed that macaque species are also reservoirs of B. quintana. Based on multi-locus sequence typing (MLST) B. quintana strains have been classified into 22 sequence types (STs), with 7 STs exclusively found in humans. Data regarding the molecular epidemiology of B. quintana endocarditis is limited to only 3 STs identified in 4 patients from Europe and Australia. We studied B. quintana endocarditis acquired in Eastern Africa or Israel to investigate the genetic diversity and clinical relatedness of B. quintana from distinct geographic regions. METHODS: Eleven patients with B. quintana endocarditis, 6 from Eastern Africa and 5 from Israel, were studied. DNA was extracted from cardiac tissue or blood specimens and analyzed by MLST based on 9 genetic loci. An evolutionary relationship between STs was visualized by a minimum spanning tree. A phylogenetic tree was constructed with the concatenated sequences (4271 bp) of the 9 loci using the maximum-likelihood method. RESULTS: Six strains were classified into previously described STs while 5 strains were identified for the first time and classified into new STs 23-27 which clustered with the previously reported STs 1-7 from human strains found in Australia, France, Germany, the USA, Russia, and the former Yugoslavia, without indication of geographical structuring. ST2 was the most prevalent ST, found in 5 of 15 patients with endocarditis (33.3%). ST26 appears to be a primary founder of the human lineage. CONCLUSIONS: The new and previously reported human STs form a single human lineage, clearly separated from the other 3 B. quintana lineages of cynomolgus, rhesus, and Japanese macaques. From evolutionary perspectives, these findings support the assumption that B. quintana has co-evolved with host species to form a host-speciation pattern. ST26 is suggested herein as a primary founder of the human lineage and may be key to explore where B. quintana had first originated; ST2 is a dominant genetic type associated with B. quintana endocarditis. To confirm these findings, additional worldwide molecular epidemiological studies are required.

Effects of selected blood-derived factors on innate immunity in the human body louse.

BACKGROUND: The human body louse (Pediculus humanus humanus) is a host-specific hematophagous ectoparasite that frequently infests populations experiencing a breakdown of hygienic conditions. Body lice are also vectors for several bacterial human pathogens, including Bartonella quintana, the agent of trench fever. However, the factors that influence immunity and infection in body lice are poorly understood. Human infection with B. quintana is associated with alcoholism and homelessness and can coincide with elevated circulating levels of the cytokine IL-10 and the inflammatory marker neopterin. Hematophagous arthropods are capable of responding physiologically and immunologically to a variety of biomolecules present in the blood of their hosts. Therefore, we sought to investigate whether ingestion of alcohol, its metabolic product acetaldehyde, IL-10 or neopterin could affect innate immunity and infection in the body louse. METHODS: Groups of lice were provisioned multiple blood meals containing physiological concentrations of alcohol, acetaldehyde, IL-10 or neopterin, and expression of six previously identified immunity-related genes (Defensin 1, Defensin 2, Prophenoloxidase, Hemocytin, Noduler and Dual Oxidase) was examined by qRT-PCR. RESULTS: Alcohol, acetaldehyde and IL-10 had no significant effects on gene expression relative to blood-fed controls while ingestion of neopterin significantly downregulated expression of Defensin 1 and Defensin 2. Nonetheless, ingestion of neopterin concurrent with B. quintana had no significant effect on the load of infection, indicating that neopterin-induced repression of Defensin expression is insufficient to reduce resistance to the pathogen. CONCLUSIONS: Our findings demonstrate that the immune system of body lice can be affected by factors present in the blood of their human hosts and suggest potential conservation of the function of some immune molecules from human host to ectoparasite. Further, the discord between the effects of neopterin on immunity-related gene expression and B. quintana load highlights the complexity of the regulation of pathogen infection in the louse vector.

Bartonella quintana Transmitted by Head Lice: An Outbreak of Trench Fever in Senegal.

BACKGROUND: Louse-borne trench fever caused by Bartonella quintana is a neglected public health concern, known to be transmitted from body louse feces via scratching. No viable B. quintana have ever been isolated from head lice before; therefore, their role as a vector is still poorly understood. METHODS: In Senegal, the implementation of a permanent local surveillance system in a point-of-care laboratory (POC) allows the monitoring of emerging diseases. Here we used culture as well as molecular and genomic approaches to document an outbreak of trench fever associated with head lice in the village of Ndiop. Head lice and blood samples were collected from febrile patients between November 2010 and April 2015. Genomes of 2 isolated strains of B. quintana were sequenced and analyzed. RESULTS: A total of 2289 blood samples were collected in the 2010-2015 period. From 2010-2013, B. quintana DNA was detected by polymerase chain reaction (PCR) in 0.25% (4/1580). In 2014, 228 blood samples were collected, along with 161 head lice from 5 individuals. B. quintana DNA was detected in 4.4% (10/228) of blood samples, and in lice specimens collected from febrile patients (61.7%, 50/81) and non-febrile patients (61.4%, 43/70). Two B. quintana strains were isolated from blood and head lice from 2 different patients. Genomic sequence analysis showed 99.98% overall similarity between both strains. CONCLUSIONS: The presence of live B. quintana in head lice, and the genetic identity of strains from patients' blood and head lice during a localized outbreak in Senegal, supports the evidence of head lice vectorial capacity.

Bartonella quintana infective endocarditis in a homeless man with unexpected positive blood culture.

Bartonella species represent important causative agents of blood culture-negative infective endocarditis (IE). Their diagnosis represents a challenge for microbiologists and often relies on serological and molecular tools. However, even if the sensitivity of blood culture remains low, it should not be definitely ruled out. Indeed, we report the unusual case of a 22 year-old Guinean homeless man diagnosed with an IE due to Bartonella quintana. Unexpectedly, conventional blood cultures were positive after 13 days of incubation. Subculture was obtained on blood and chocolate agar, after 15 days of incubation in a 5 % CO2 atmosphere. Bacterial identification was obtained up to the species level using molecular tools (16S rRNA gene amplification and sequencing). A literature review of B. quintana blood culture-positive IE was conducted and revealed eighteen similar reported cases on a 25-year period. This case illustrates that, despite low sensitivity, Bartonella IE may be diagnosed thanks to prolonged blood culture.

Seroprevalence of Bartonella quintana Infection: A Systematic Review.

Introduction: Bartonella quintana is an anaerobic bacillus whose main target is the erythrocyte. This bacterium transmitted by the body louse notably infected the soldiers of the First World War from where the name of this disease: fever of the trenches. The 90s marked the return of this bacterial infection. B. quintana infection in the homeless was reported in the literature with a high incidence in these populations worldwide. This upsurge of cases justified this study for a better understanding of B. quintana infections. Methods: We conducted a systematic review to evaluate the seroprevalence of B. quintana infection by using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines to collect scientific papers from PubMed and Google Scholar based on combining keywords. Results: The review included 45 articles published from April 1996 to March 2020 with 84 subpopulations of 21 countries from 4 continents; among them, 61 subpopulations had a positive rate from 0.2% to 65%. These subpopulations were divided into four main groups: homeless people, healthy people, blood donors, and symptoms/diseases. Homeless people were the main target of this infection, and three factors related to susceptibility were homeless period, age, and alcoholism. 6/11, 12/20, and 32/41 subpopulations of healthy people, blood donors, symptoms/diseases, respectively, had a positive percentage. However, factors of exposure in these three groups were not mentioned. Other reservoirs, vectors, and transmitted routes were identified to partially explain the worldwide spread of the infection, and it is important to have more further investigations to identify potential risk factors. This will help to limit contamination and prevent effectively. Conclusions: This serological overview indicated the importance of B. quintana infection that has emerged in multiple regions, touched worldwide populations.

Examination of vertical transmission of Bartonella quintana in body lice following multiple infectious blood meals.

Bartonella quintana is a re-emerging louse-borne pathogen. Horizontal transmission from the body louse vector (Pediculus humanus humanus) to a human host occurs through contact with infectious louse feces containing a high concentration of the bacteria. However, questions have remained about whether vertical transmission from infected vectors to their progeny, which could significantly influence the dynamics of transmission to humans, occurs in body lice. To address this subject, we performed a series of controlled laboratory experiments that examined the presence of B. quintana on the surface of and within eggs produced by female body lice that were provisioned multiple infectious blood meals to recapitulate the natural pathogen acquisition process. Our results demonstrate that B. quintana DNA can be detected from the surface of eggs by qPCR due to vertical transfer of infectious feces to the egg sheath during or after oviposition. However, viable B. quintana could not be cultured from the hemolymph of adult female lice or from within eggs that were surface sterilized, indicating a lack of true transovarial transmission. Based on this evidence, vertical transfer of B. quintana from infected adult lice to their eggs probably has a limited impact on the dynamics of transmission to humans.

Bartonella quintana Infection in People Experiencing Homelessness in the Denver Metropolitan Area.

BACKGROUND: Bartonella quintana is an important cause of infection amongst people experiencing homelessness that is underdiagnosed due to its nonspecific clinical manifestations. We reviewed cases identified in the Denver metropolitan area in 2016-2021. METHODS: The electronic medical records from 2 large academic medical centers in Colorado were reviewed for demographic, clinical, and laboratory features of patients with B. quintana infection confirmed by blood culture, serologies, and/or molecular testing from July 2016 to December 2021. RESULTS: Fourteen patients with B. quintana infection were identified. The mean age was 49.5 years (SD 12.7 years) and 92.9% of patients were male. Twelve patients had history of homelessness (85.7%) and 11 were experiencing homelessness at the time of diagnosis (78.6%). Most frequent comorbidities included substance use (78.6%), of which 42.9% had alcohol use disorder. The average time to blood culture positivity was 12.1 days (SD 6.2 days). Three patients with bacteremia had negative B. quintana IgG, and 6 of 14 (42.8%) patients had evidence of endocarditis on echocardiography. CONCLUSIONS: B. quintana is an underrecognized cause of serious infection in individuals experiencing homelessness. Serologic and microbiologic testing, including prolonged culture incubation, should be considered in at-risk patients due to ongoing transmission in homeless populations.