Subacute Bacterial Endocarditis with Leptotrichia goodfellowii in a Patient with a Valvular Allograft: A Case Report and Review of the Literature

Leptotrichia Bacteremia: 10-Year Retrospective Clinical Analysis and Antimicrobial Susceptibility Profiles

Leptotrichia species are anaerobic, Gram-negative bacilli increasingly recognized as pathogens capable of causing invasive infections such as bloodstream infection (BSI), particularly among immunocompromised patients. However, there is a paucity of data regarding epidemiology, antimicrobial susceptibility, optimal treatment, and clinical outcomes among patients with Leptotrichia bacteremia. Patient risk factors, treatment approaches, and outcomes of a retrospective cohort of adult patients with Leptotrichia BSI at a tertiary medical center (Mayo Clinic Rochester [MCR]) were evaluated. Concurrently, species, temporal trends, and antimicrobial susceptibility testing (AST) results of Leptotrichia isolates submitted to a reference laboratory (Mayo Clinic Laboratories) over the past 10 years were examined. We identified 224 blood culture isolates of Leptotrichia species, with 26 isolates from patients treated at MCR. The most frequent species included L. trevisanii (49%), L. buccalis (24%), and L. wadei (16%). Leptotrichia species demonstrated >90% susceptibility to penicillin, metronidazole, ertapenem, and piperacillin-tazobactam. However, 96% (74/77) of isolates were resistant to moxifloxacin. For patients treated at MCR, the mean patient age was 55 years (standard deviation [SD], 17), with 9 females (35%), and all were neutropenic at the time of BSI. The primary sources of infection were gastrointestinal (58%), intravascular catheter (35%), and odontogenic (15%). Patients were treated with metronidazole (42%), piperacillin-tazobactam (27%), or carbapenems (19%). The mean duration of treatment was 11 days (SD, 4.5), with a 60-day all-cause mortality of 19% and no microbiologic relapse. Leptotrichia species are rare but important causes of BSI in neutropenic patients. Due to evolving antimicrobial susceptibility profiles, a review of AST results is necessary when selecting optimal antimicrobial therapy.

Salivary dysbiosis in Sjögren's syndrome and a commensal-mediated immunomodulatory effect of salivary gland epithelial cells

Salivary gland epithelial cells (SGECs) have been implicated in the pathogenesis of Sjögren's syndrome due to aberrant antigen-presentation function. This study examined the hypothesis that oral dysbiosis modulates the antigen-presentation function of SGECs, which regulates CD4 T cell proliferation in primary Sjögren's syndrome (pSS). Saliva samples from 8 pSS patients and 16 healthy subjects were analyzed for bacterial 16S ribosomal DNA. As a result, 39 differentially abundant taxa were identified. Among them, the phylum Proteobacteria comprised 21 taxa, and this phylum was mostly enriched in the healthy controls. The proteobacterium Haemophilus parainfluenzae was enriched in the healthy controls, with the greatest effect size at the species level. Treatment of A253 cells in vitro with H. parainfluenzae upregulated PD-L1 expression, and H. parainfluenzae-pretreated A253 cells suppressed CD4 T cell proliferation. The suppression was partially reversed by PD-L1 blockade. Among low-grade xerostomia patients, salivary abundance of H. parainfluenzae decreased in pSS patients compared to that in non-pSS sicca patients. Our findings suggest that H. parainfluenzae may be an immunomodulatory commensal bacterium in pSS.

Identification of Leptotrichia goodfellowii infective endocarditis by next-generation sequencing of 16S rDNA amplicons

The oral aerotolerant anaerobe Leptotrichia goodfellowii is an unusual cause of endocarditis and is amenable to treatment with β-lactam antibiotics. Because this organism is difficult to identify by conventional methods, molecular detection is a key diagnostic modality. Broad-range 16S rDNA PCR followed by Sanger sequencing constitute the first-line molecular approach, yet poor DNA quality, contaminating DNA, or low template quantity make identification challenging. Here we report a case of culture-negative, aortic and mitral valve endocarditis in a 66-yr-old woman with a history of cardiomyopathy, atrial fibrillation with intracardiac pacer, poor dentition, and recent tooth infection. In this case, 16S rDNA amplicon Sanger sequencing was not sufficient for pathogen identification because of interfering DNA, but deconvolution of the clinical sample using reflexive next-generation amplicon sequencing enabled confident identification of a single pathogenic organism, L. goodfellowii. The patient developed a sigmoid colon perforation and died despite additional surgical treatment. Most Leptotrichia endocarditis cases have been subacute and have been successfully treated with antibiotics, with or without valve replacement. This case highlights both an unusual etiologic agent of endocarditis, as well as the rational utilization of advanced molecular diagnostics tools for characterizing serious infections.

Smoking and microbiome in oral, airway, gut and some systemic diseases

The human microbiome harbors a diverse array of microbes which establishes a mutually beneficial relation with the host in healthy conditions, however, the dynamic homeostasis is influenced by both host and environmental factors. Smoking contributes to modifications of the oral, lung and gut microbiome, leading to various diseases, such as periodontitis, asthma, chronic obstructive pulmonary disease, Crohn’s disease, ulcerative colitis and cancers. However, the exact causal relationship between smoking and microbiome alteration remains to be further explored.

Leptotrichia species in human infections II

Leptotrichia species are non-motile facultative anaerobic/anaerobic bacteria that are found mostly in the oral cavity and some other parts of the human body, in animals, and even in ocean sediments. Valid species include L. buccalis, L. goodfellowii, L. hofstadii, L. honkongensis, L. shahii, L. trevisanii, and L. wadei. Some species require serum or blood for growth. All species ferment carbohydrates and produce lactic acid that may be involved with tooth decay. Acting as opportunistic pathogens, they are involved in a variety of diseases, and have been isolated from immunocompromised but also immunocompetent individuals. Mucositis, oral lesions, wounds, and abscesses may predispose to Leptotrichia septicemia. Because identification of Leptotrichia species by phenotypic features occasionally lead to misidentification, genetic techniques such as 16S rRNA gene sequencing is recommended. Early diagnosis and treatment of leptotrichia infections is important for positive outcomes. Over the last years, Leptotrichia species have been associated with several changes in taxonomy and new associations with clinical diseases. Such changes are reported in this updated review.