Targeted Versus Shotgun Metagenomic Sequencing-based Detection of Microorganisms in Sonicate Fluid for Periprosthetic Joint Infection Diagnosis.

BACKGROUND: Next-generation sequencing (NGS) is increasingly used for periprosthetic joint infection (PJI) diagnosis, but its clinical utility is poorly defined. Shotgun metagenomic sequencing (sNGS) has been reported to identify PJI pathogens undetected by culture in sonicate fluid. However, sNGS is complex and costly. Here, 16S ribosomal RNA (rRNA) gene-based targeted metagenomic sequencing (tNGS) was compared to sNGS of sonicate fluid for microbial detection and identification in patients with total hip arthroplasty (THA) and total knee arthroplasty (TKA) failure. METHODS: A convenience sample of sonicate fluids derived from patients who had undergone THA or TKA removal, enriched with culture negative PJI cases, was tested. Samples had been previously tested by sNGS. For tNGS, samples were extracted, amplified by polymerase chain reaction targeting the V1 to V3 regions of the 16S rRNA gene, and sequenced on an Illumina MiSeq. RESULTS: A total of 395 sonicate fluids, including 208 from subjects with PJI, were studied. Compared with sonicate fluid culture, tNGS had higher positive percent agreement (72.1 vs 52.9%, P < .001), detecting potential pathogens in 48.0% of culture-negative PJIs. There was no difference between the positive percent agreement of tNGS (72.1%) and sNGS (73.1%, P = .83). CONCLUSIONS: 16S rRNA gene-based tNGS is a potential diagnostic tool for PJI pathogen identification in sonicate fluid from failed THAs and TKAs in culture-negative cases, with similar performance characteristics to sNGS.

Mycoplasma genitalium Endocarditis in Prosthetic Aortic Valve.

We report a case of Mycoplasma genitalium endocarditis in a prosthetic heart valve of a woman who sought care in Switzerland for acute aortic valve dysfunction 3 years after valve replacement. This unusual manifestation of infection with this bacterium was diagnosed using broad-range PCR despite suspicion of a mechanical disinsertion.

Culture-negative Capnocytophaga canimorsus meningitis diagnosed by 16s ribosomal RNA polymerase chain reaction in an immunocompetent veterinarian and a review of the literature.

Capnocytophaga canimorsus is a fastidious, capnophilic and facultative anaerobic Gram-negative rod found commonly in the oral flora of dogs that may cause zoonotic infections such as cellulitis and eye infections. In immunocompromised patients, it may cause fulminant sepsis. Meningitis due to C. canimorsus is, however, a rare manifestation. This is the first reported case of C. canimorsus meningitis in Australia in an immunocompetent veterinarian diagnosed by 16s ribosomal RNA polymerase chain reaction.

Pathogen Detection in Infective Endocarditis Using Targeted Metagenomics on Whole Blood and Plasma: a Prospective Pilot Study.

Initial microbiologic diagnosis of infective endocarditis (IE) relies on blood cultures and Bartonella and Coxiella burnetii serology. Small case series and one prospective study have preliminarily reported application of metagenomic sequencing on blood or plasma for IE diagnosis. Here, results of a prospective pilot study evaluating targeted metagenomic sequencing (tMGS) for blood-based early pathogen detection and identification in IE are reported. Subjects diagnosed with possible or definite IE at a single institution were prospectively enrolled with informed consent from October 2020 to July 2021. Blood was drawn and separated into whole blood and plasma. Both specimen types were subjected to nucleic acid extraction and PCR targeting the V1-V3 region of the 16S ribosomal RNA gene, followed by next-generation sequencing on an Illumina MiSeqTM platform. 35 subjects, 28 (80%) with definite and 7 (20%) with possible IE were enrolled, including 6 (17%) with blood culture-negative endocarditis (BCNE). Overall, 20 whole blood (59%) and 16 plasma (47%) samples tested positive (P = 0.47). When results of whole blood and plasma testing were combined, a positive tMGS result was found in 23 subjects (66%). tMGS identified a potential pathogen in 5 of 6 culture-negative IE cases. Although further study is needed, the results of this pilot study suggest that blood-based tMGS may provide pathogen identification in subjects with IE, including in culture-negative cases.

Routine use of 16S rRNA PCR and subsequent sequencing from blood samples in septic shock: about two case reports of Capnocytophaga canimorsus infection in immunocompetent patients.

BACKGROUND: Capnocytophaga canimorsus infection happens frequently in immunosuppressed patients with reported domestic animal bites. Clinical presentation ranges from simple cellulitis to fulminant septic shock with disseminated intravascular coagulopathy, with an overall mortality of 30%. Conventional blood culture is often negative as this is a slow-growing pathogen. Nevertheless, the increasing use of 16S rRNA gene amplification and Sanger sequencing allows a much more rapid diagnostic confirmation. We present two case reports where 16S rRNA gene sequencing helped to diagnose Capnocytophaga canimorsus infection. CASE PRESENTATION: Case 1: A 53-year-old man with a history of non-cirrhotic chronic alcohol consumption was admitted to the intensive care unit (ICU) for septic shock and disseminated intravascular coagulopathy (DIC) of unknown origin. Blood cultures remained negative and a 16S rRNA PCR was performed leading to the identification of Capnocytophaga Canimorsus on day 4. Targeted antibiotic therapy with ceftriaxone for 14 days lead to overall recovery. Afterwards, the patient recalled a dog bite 2 days before hospitalization with a punctiform necrotic wound localized on a finger, which was not obvious at admission. Case 2: A 38-year-old man arrived to the emergency department for acute alcohol intoxication and history of a dog bite 2 days before. At admission, septic shock with purpura fulminans was diagnosed and required ICU hospitalization, invasive mechanical ventilation, vasopressor support and renal replacement therapy due to the rapid clinical deterioration. In the context of septic shock with purpura fulminans, DIC and recent dog bite, the diagnosis of Capnocytophaga canimorsus septic shock was suspected, and early confirmed by 16S rRNA PCR coupled to Sanger sequencing on day 2. Blood cultures became only positive for Capnocytophaga canimorsus 5 days after admission. Ceftriaxone alone was infused for 10 days in total, and the patient was discharged from the ICU on day 25. CONCLUSIONS: 16S rRNA gene PCR proves an important diagnostic tool when facing a sepsis of unknown origin. In these two cases of septic shock related to Capnocytophaga canimorsus, initial blood cultures remained negative at 24 h, whereas the diagnosis was achieved by 16S rRNA PCR sequencing performed from blood samples obtained at admission.

A case of infective endocarditis caused by Arthrobacter woluwensis.

Corynebacteria are rare causative agents of infective endocarditis. This is a reported case of a destructive aorto-mitral infective endocarditis caused by Arthrobacter woluwensis. Microbial identification was achieved by 16S rRNA polymerase chain reaction on valve tissue samples. Outcome was favorable after surgical valve replacement and 4-week antibiotic treatment.

Case report: first symptomatic Candidatus Neoehrlichia mikurensis infection in Slovenia.

BACKGROUND: Candidatus Neoehrlichia mikurensis (CNM) is an emerging tick-born pathogen and usually causes symptomatic infection only in immunocompromised patients. Apart from one described case found in the literature where cultivation was successful, all cases so far were diagnosed by using broad-range 16S rDNA PCR. CASE PRESENTATION: Our patient presented with a prolonged febrile state of unknown origin. Clinical presentation, extensive medical workup and classic microbiologic testing were non-conclusive. Several infectious agents and other causes for the febrile state were excluded. In the end, a broad-range 16S rDNA PCR was to be performed to confirm the diagnosis of CNM infection. Treatment was successful with doxycycline. CONCLUSIONS: Due to the obscurity of the pathogen, diagnostic workup in CNM is prolonged and challenging. More awareness is need about this emerging infectious disease in countries with high prevalence of tick-borne diseases as standard microbiological methods are not successful in confirming the diagnosis.

Molecular Approach to Diagnosis of Cardiovascular Implantable Electronic Device Infection.

BACKGROUND: Sonicate fluid (SF), a solution derived from vortexing and sonication of explanted cardiovascular implantable electronic devices (CIEDs), is a higher-yield specimen compared with swabs or tissues for culture-based detection of microorganisms associated with CIED infection. Despite this, SF culture fails to identify a causative organism in ~50% of cases. We aimed to evaluate the diagnostic performance of 16S ribosomal RNA gene (rRNA) polymerase chain reaction (PCR)/sequencing of SF and compare it with that of SF culture. METHODS: We identified 322 SF specimens from extracted CIEDs and reviewed clinical data for each patient. Subjects were classified as having or not having CIED infection. Cases were subcategorized as culture negative if no significant growth was reported from SF cultures and as culture positive if an organism was detected above predefined thresholds. 16S rRNA PCR/sequencing was performed, with the organisms identified reported according to Clinical and Laboratory Standards Institute guidelines for sequence data interpretation. RESULTS: A total of 278 SF samples corresponded to infected cases, of which 160 were culture positive and 118 culture negative. The remaining 44 were from noninfected cases, of which 2 were culture positive. Compared with SF culture, the sensitivity of 16S rRNA PCR/sequencing was higher (64% vs 57.5%, P = .003). 16S rRNA PCR/sequencing detected a potential pathogen in 28 of 118 culture-negative cases, identifying staphylococci in the majority (18/28). CONCLUSIONS: 16S rRNA PCR/sequencing has higher sensitivity to detect bacteria in SF from extracted CIEDs than does SF culture.

Impact of pre-operative antimicrobial treatment on microbiological findings from endocardial specimens in infective endocarditis.

Treatment of infective endocarditis (IE) should be initiated promptly. This might hamper the chances to identify the causative organism in blood cultures. Microbiological sampling of infected valve in patients undergoing surgery might identify the causative organism. The impact of pre-operative antimicrobial treatment on the yield of valve samples is not known. This study evaluated the impact of the duration of the pre-operative antibiotic treatment on valve culture and 16S rRNA PCR findings from resected endocardial samples. Patients meeting the modified Duke criteria of definite or possible IE and undergoing valve surgery due to IE during 2011-2016 were included from Southern Finland. Eighty-seven patients were included. In patients with shorter than 2 weeks of pre-operative antimicrobial treatment, PCR was positive in 91% (n = 42/46) and valve culture in 41% (n = 19/46) of cases. However, in patients who had 2 weeks or longer therapy before operation, PCR was positive in 53% (n = 18/34) and all valve cultures were negative. In 14% of patients, PCR had a diagnostic impact. In blood-culture negative cases (n = 13), PCR could detect the causative organism in ten patients (77%). These included five cases of Bartonella quintana, one Tropheryma whipplei, and one Coxiella burnetii. Long pre-operative antimicrobial treatment was shown to have a negative impact on microbiological tests done on resected endocardial material. After 2 weeks of therapy, all valve cultures were negative, but PCR was positive in half of the cases. PCR aided in diagnostic work-up, especially in blood culture negative cases.

The clinical presentation of Legionella arthritis reveals the mode of infection and the bacterial species: case report and literature review.

BACKGROUND: While Legionella is a common cause of pneumonia, extrapulmonary infections like arthritis are scarce. Here, we describe a case of monoarthritis due to Legionella bozemanii, with no history of pneumonia. We provide a literature review of the 9 previously published Legionella arthritis and highlight a dichotomous epidemiology suggesting different physiopathological pathways leading to joint infection. CASE PRESENTATION: A 56-year old woman under immunosuppressive treatment by oral and intra-articular corticosteroids, methotrexate, and tocilizumab for an anti-synthetase syndrome was hospitalized for worsening pain and swelling of the left wrist for 3 days. Clinical examination showed left wrist synovitis and no fever. The arthritis occurred a few days after an accidental fall on wet asphalt responsible for a cutaneous wound followed by a corticosteroid intra-articular injection. Due to both the negativity of conventional culture of articular fluid and suspicion of infection, 16S rRNA and specific PCRs were performed leading to the identification of L. bozemanii. Legionella-specific culture of the articular fluid was performed retrospectively and isolated L. bozemanii. The empiric antibiotic therapy was switched for oral levofloxacin and rifampin and the patient recovered after a 12-week treatment. CONCLUSION: We report a case of L. bozemanii monoarthritis in an immunosuppressed woman, following a fall on wet asphalt and intra-articular corticosteroid injection. The review of the literature found that the clinical presentation reveals the mode of infection and the bacterial species. Monoarthritis more likely occurred after inoculation in patients under immunosuppressive therapy and were associated with non-Legionella pneumophila serogroup 1 (Lp1) strains that predominate in the environment. Polyarthritis were more likely secondary legionellosis localizations after blood spread of Lp1, the most frequently found in pneumonia. In both settings, 16S rRNA and Legionella-specific PCR were key factors for the diagnosis.

Use of staged molecular analysis to determine causes of unexplained central nervous system infections.

No agent is implicated in most central nervous system (CNS) infections. To investigate cerebrospinal fluid samples from patients with CNS infections of unknown cause in 1 hospital in Taiwan, we used a staged molecular approach, incorporating techniques including multiplex MassTag PCR, 16S rRNA PCR, DNA microarray, and high-throughput pyrosequencing. We determined the infectious agent for 31 (24%) of 131 previously negative samples. Candidate pathogens were identified for 25 (27%) of 94 unexplained meningitis cases and 6 (16%) of 37 unexplained encephalitis cases. Epstein-Barr virus (18 infections) accounted for most of the identified agents in unexplained meningitis cases, followed by Escherichia coli (5), enterovirus (2), human herpesvirus 2 (1), and Mycobacterium tuberculosis. Herpesviruses were identified in samples from patients with unexplained encephalitis cases, including varicella-zoster virus (3 infections), human herpesvirus 1 (2), and cytomegalovirus (1). Our study confirms the power of multiplex MassTag PCR as a rapid diagnostic tool for identifying pathogens causing unexplained CNS infections.

Use of 16s rRNA Gene Sequencing for the Identification of Viridans Group Streptococci.

Streptococci belonging to the viridans group are gram-positive bacteria residing as commensals in the upper respiratory, gastrointestinal, and genital tracts in humans. Though they are largely known to be commensals, they may also cause life-threatening infections like infective endocarditis, septicemia, pyogenic infections, pneumonia, and meningitis. The viridans group streptococci (VGS) are usually identified by biotyping; however, species discrimination is not always possible by phenotypic characterization. We identified 53 isolates from blood cultures of patients with infective endocarditis and compared the results of biotyping with 16s rRNA gene sequencing for species identification. Organisms belonging to the mitis group were the most common. 16s rRNA gene polymerase chain reaction and sequencing were useful in identifying the etiological agents at the species level. S.oralis was the most common etiological agent.

Metagenomic data reveals microbiome characteristics of culture-negative brain abscess samples.

A brain abscess is a focal collection of pus in the brain parenchyma surrounded by a well-vascularized collagenous capsule in response to an infection. The microbiome of brain abscesses has been shown to be polymicrobial, dominated by uncultivable and anaerobic organisms of odontogenic origin. The data provided in this article includes the sequences of bacterial 16S rRNA gene from three culture-negative brain abscess samples suspected to have poly-microbial aetiology based on Sanger sequencing. DNA was extracted from brain abscess samples, and targeted-metagenomics sequencing was done by amplifying the full-length bacterial 16S rRNA followed by a nested PCR for V3-V4 regions using universal and specific primers. The barcoded amplicons were sequenced on Illumina MiSeq V2 instrument to generate 0.5M, 250bp paired-end reads/sample. The total sequencing reads were 455966, 345746, and 438658 for samples P32, P49, and P8, respectively. Bioinformatics tools such as FLASH, VSEARCH, and QIIME1 were used to process the reads generated for Operational Taxonomic Unit analysis (OTU). Bacterial species belonging to phyla Firmicutes, Bacteroidetes, and Fusobacteria were abundant in samples P49 and P8, which are mainly anaerobic and microaerophilic bacteria. These are typical of the human oral/gut microbiota and are implicated in brain abscess formation. Sample P32 showed the abundance of bacterial species belonging to phyla Proteobacteria and Actinobacteria, which are commonly found in the environment. Raw data files are available at the Sequence Read Archive (SRA), National Center for Biotechnology Information (NCBI), and data information can be found at the BioProject, PRJNA785100 under the accession numbers SRX13271109, SRX13271110, SRX13295897. The data shows the microbiome constitution, including several anaerobic and unculturable bacterial species from culture-negative brain abscess samples. This dataset will be useful for future research on comparative genomics and management of patients with culture-negative brain abscesses.

Culture-negative endocarditis caused by Stenotrophomonas maltophilia: a report of two cases.

Stenotrophomonas maltophilia, an aerobic, non-fermenting, Gram-negative bacterium, is an emerging nosocomial pathogen. It is considered to be a low-grade pathogen, and infections due to S. maltophilia are uncommon. However, in the recent past, S. maltophilia infections have been on the rise, particularly in patients who are either immunocompromised, aged or on long-term antibiotic therapy. Endocarditis due to S. maltophilia is extremely rare. This is a report of two patients with S. maltophilia endocarditis who were diagnosed by 16S rRNA gene sequencing.

Clinical Use of a 16S Ribosomal RNA Gene-Based Sanger and/or Next Generation Sequencing Assay to Test Preoperative Synovial Fluid for Periprosthetic Joint Infection Diagnosis.

Preoperative pathogen identification in patients with periprosthetic joint infection (PJI) is typically limited to synovial fluid culture. Whether sequencing-based approaches are of potential use in identification of pathogens in PJI, and if so which approach is ideal, is incompletely defined. The objective of the study was to analyze the accuracy of a 16S rRNA (rRNA) gene-based PCR followed by Sanger sequencing and/or targeted metagenomic sequencing approach (tMGS) performed on synovial fluid for PJI diagnosis. A retrospective study was conducted, analyzing synovial fluids tested between August 2020 and May 2021 at a single center. Subjects with hip, knee, shoulder, and elbow arthroplasties who had synovial fluid aspirated and clinically subjected to sequence-based testing and conventional culture were studied. A total of 154 subjects were included in the study; 118 had noninfectious arthroplasty failure (NIAF), while 36 had PJI. Clinical sensitivity and specificity for diagnosis of PJI were 69% and 100%, respectively, for the sequencing-based approach and 72% and 100%, respectively, for conventional culture (P = 0.74). The combination of both tests was more sensitive (83%) than culture alone (P = 0.04). Results of sequencing-based testing led to changes in treatment in four of 36 (11%) PJI subjects. Microbial identification was achieved using Sanger and next generation sequencing in 19 and 6 subjects, respectively. When combined with culture, the described 16S rRNA gene sequencing-based approach increased sensitivity compared to culture alone, suggesting its potential use in the diagnosis of PJI when synovial fluid culture is negative. IMPORTANCE Periprosthetic joint infection (PJI) is a dreadful complication of joint replacement. Noninvasive identification of infectious pathogens has been traditionnally limited to culture-based testing of synovial fluid which has poor sensitivity. Sanger and Next-generation sequencing (NGS) may be used for synovial fluid testing in PJI, but experience in routine practice is sparse. We used a targeted metagenomic sequencing approach for routine testing of synovial fluid involving NGS when Sanger sequencing had failed or was likely to fail. The objective of this study was to analyze the approach's performance for diagnosis of PJI in comparison to culture for testing synovial fluid. Overall, the sequencing-based approach was not superior to culture for diagnosis of PJI, but yielded positive results in some culture-negative samples.

Evaluation of a syndromic panel polymerase chain reaction (spPCR) assay for the diagnosis of device-associated bone and joint infections (BJI).

OBJECTIVE: Pathogen detection is crucial for diagnosis and targeted therapy in implant-associated bone and joint infections (BJI). Culture-based microbiology regularly fails to identify causative pathogens. This study evaluated the diagnostic accuracy and clinical usefulness of a syndromic panel polymerase chain reaction (spPCR) assay targeting common BJI pathogens in tissue specimens from patients with implant-associated BJI. METHODS: Results obtained by spPCR assay and a 16S rDNA PCR were compared with results obtained from a standard of care (SOC) culture-based diagnostics, serving as a gold standard. In total, 126 specimens obtained from 73 patients were analyzed. RESULTS: The spPCR assay correctly identified 33/40 culture-positive samples (82.5 %) and was positive in 9/86 (10.5 %) culture-negative samples, resulting in an overall sensitivity of 84.6 % (95% confidence interval [CI] 68.79-93.59%) and specificity of 89.35% (95% CI 80.6-94.81%). The spPCR was more sensitive compared with the 16S rDNA PCR (37.5%). The spPCR identified pathogens in 7/51 (13.7%) SOC-negative patients. Re-evaluation of spPCR results in clinical context suggested their clinical significance. CONCLUSION: An spPCR assay targeting common pathogens causing implant-associated BJI may help to identify causative agents in culture-negative cases. As false-negative results are possible, spPCR assays appear as an add-on approach for pathogen detection in implant-associated BJI.

Bacillus Cereus bacteremia complicated by brain abscess in a severely immunocompromised patient: Addressing importance of early recognition and challenges in diagnosis.

Bacillus cereus (B. cereus) is a known cause of a food poisoning in the general population. However, it can cause life-threatening sepsis and shock in severely immunocompromised patients with hematologic malignancies, which frequently lead to central nervous system (CNS) infections associated with high mortality and morbidity. In this case report, we describe a patient with a newly diagnosed acute myeloid leukemia that underwent induction chemotherapy and developed B. cereus infection that was associated with septic shock and brain abscesses. Definitive diagnosis of multiple brain abscesses was not manifested with routine microbiological investigation but required the use of 16S ribosomal (rRNA) gene polymerase chain reaction (PCR) sequencing of the resected brain lesion. The patient was eventually treated with 8-week course of intravenous vancomycin and high-dose ciprofloxacin which led to a full recovery. This report highlights the significant risk posed by B. cereus infection in neutropenic patients, the use of 16S rRNA PCR sequencing test for definitive diagnosis and use of combination therapy for successful treatment of B. Cereus CNS infection.

Clinical utility of 16S rRNA PCR in pleural infection.

Pleural infections cause major morbidity and mortality, particularly amongst paediatric and elderly populations. The aetiology is broad, but pleural culture fails to yield a causative pathogen in approximately 40 % of cases. Alternative pathogen identification methods are therefore required. The aim of the study was to investigate the yield from and impact on patient care when performing 16S rRNA PCR on culture-negative pleural fluid specimens and to determine whether any individual laboratory parameters were associated with a positive 16S rRNA PCR result. We conducted a study on 90 patients with suspected pleural infection, who had a culture-negative pleural fluid specimen, which underwent 16S rRNA PCR analysis between August 2017 and June 2019. This study was undertaken at a large NHS Trust in London, UK. Thirty-one per cent of culture-negative pleural fluid specimens tested by 16S rRNA PCR yielded a positive PCR result. Our data demonstrated that 16S rRNA PCR detected a significantly higher proportion of Streptococcus pneumoniae (P<0.0001) and fastidious, slow-growing and anaerobic pathogens (P=0.0025) compared with culture-based methods. Of the 25 16S rRNA PCR results that were positive for a causative pathogen, 76 % had a direct impact on clinical management. No single laboratory variable was found to be associated with a positive 16S rRNA PCR result. The findings from our real-world evaluation highlight the importance of 16S rRNA PCR in confirming pleural infection when the aetiology is unknown, and its direct, positive impact on clinical management.

Septic arthritis due to Mycoplasma orale in a young patient with hypogammaglobulinemia.

Mycoplasma orale is an obligate intracellular bacterium usually found as a commensal in the human oral cavity. Symptomatic infections with this organism are rare, but severe disease has been described in the setting of impaired humoral immunity. Here, we describe a case in which M. orale was identified from the joint fluid of a patient with septic arthritis, splenic lesions, and agammaglobulinemia. A 15-year-old boy was admitted to the hospital with fever, progressive left knee swelling, and pain. His medical history was significant for Burkitt's lymphoma, the treatment of which had included rituximab 6 years earlier. M. orale was identified in the synovial fluid using 16S ribosomal RNA gene sequencing. He was also found to be hypogammaglobulinemic, and imaging revealed multiple splenic lesions. He was treated with doxycycline and intravenous immunoglobulin, which resulted in complete resolution of his arthritis and other symptoms. Mycoplasma species should be suspected in patients with humoral immunodeficiency and compatible findings.

Le Mycoplasma orale est une bactérie intracellulaire obligatoire généralement observée dans la flore commensale de la cavité orale. Les infections symptomatiques par ces organismes sont rares, mais une maladie grave a été décrite en cas de perturbation de l'immunité humorale. Dans le présent document, les auteurs décrivent un cas de M orale décelé dans le liquide articulaire d'un patient atteint d'arthrite septique, de lésions spléniques et d'agammaglobulinémie. Un garçon de 15 ans a été hospitalisé parce qu'il faisait de la fièvre, avait un œdème évolutif du genou gauche et de la douleur. Son histoire médicale incluait un lymphome de Burkitt, dont le traitement comprenait du rituximab six ans plus tôt. Le M orale a été décelé dans le liquide synovial au moyen du séquençage du gène d'ARN ribosomique 16S. Il était également hypogammaglobulinémique, et l'imagerie a révélé de multiples lésions spléniques. Il a reçu un traitement à la doxycycline et aux immunoglobulines intraveineuses, qui ont favorisé une résolution complète de son arthrite et de ses autres symptômes. Il faut envisager des espèces de Mycoplasma chez les patients ayant une immunodéficience humorale et des observations compatibles.

Lawsonella clevelandensis is a rare cause of infected chronic contained rupture of abdominal aortic aneurysm.

Lawsonella clevelandensis is an anaerobic, partially acid-fast, Gram-positive bacillus associated with abscess formation. We present the case of a 70-year-old male with chronic contained rupture of abdominal aortic aneurysm (CCR-AAA) complicated by intra-abdominal abscess formation. An abdominal computed tomography scan revealed a rim-enhancing retroperitoneal collection tracking into the subcutaneous layer of the left flank and buttock, suggestive of CCR-AAA with infected haematoma. He underwent ultrasound-guided needle aspiration of the intra-abdominal collection. Conventional culture techniques failed to isolate L. clevelandensis , and the diagnosis was only confirmed by means of 16S rRNA PCR. The patient underwent branched endovascular repair of his aneurysm, and was commenced on treatment with co-amoxiclav, resulting in significant reduction in the size of the infected collection. This is only the second reported case of infection with L. clevelandensis in the UK, and the first reported case of this organism causing infected CCR-AAA.