Infective Endocarditis Due to Neisseria elongata Amit Noheria, MBBS, SM, Peter W. Anderson,MD, Gino G. Tapia-Zegarra, MD, Larry M. Baddour, MD, and Walter R. Wilson, MD Abstract: We present 2 cases of prosthetic valve endocarditis due to Neisseria elongata subspecies nitroreducens and elongata. Neisseria elongata is a fastidious, immotile, oxidase-positive, gram-negative bacil- lus found in the human oropharyngeal flora that is a rare cause of infec- tive endocarditis. It is distinguished from Kingella kingae, Eikenella corrodens, and other organisms based on extended biochemical testing and 16S recombinant DNA sequencing. We review the literature on N. elongata endocarditis and highlight the similarities between N. elongata and HACEK organisms regarding their biochemical profiles and clinical features of infective endocarditis. (Infect Dis Clin Pract 2010;00: 00Y00) N eisseria elongata is a commensal human oropharyngeal organism first described in 1970. 1 It is a nonmotile, oxidase- positive, short, and slender rod arranged as diplobacilli or short chains, with some coccoid forms. It is gram negative with a slight tendency to retain the first stain. It has limited ability to survive on blood agar at room temperature. Neisseria elongata is closely related to Kingella, Eikenella, Moraxella, Centers for Disease Control (CDC) group EF4, and a group of other diffi- cult to identify organisms, apart from similarities with other Neisseria species. 2 Although most Neisseria species are gram- negative diplococci, a few bacillary forms occur and include N. elongata, N. weaveri (formerly CDC group M5), N. bacilli- formis, and group AK105. Although it is rare for N. elongata to cause infective endocarditis, it is the most common cause of infective endocarditis among all Neisseria species; others include N. mucosa, N. sicca, N. subflava, and occasionally N. cinerea, N. flavescens, N. gonorrhea, and group AK105. 3,4 The subspecies nitroreducens (formerly CDC group M6) has been most frequently linked to infective endocarditis; it also can cause septicemia and osteomyelitis. 2,5,6 Neisseria elongata subspe- cies elongata and glycolytica have been rarely reported to cause infective endocarditis. 3,5 We present 2 cases of prosthetic valve endocarditis due to N. elongata subspecies nitroreducens and elongata and highlight the similarities between N. elongata and HACEK organisms regarding their biochemical profiles and the clinical features of infective endocarditis. CASE REPORTS Patient 1 A 65-year-old woman presented to the emergency depart- ment with a 4-day history of mild headache, malaise, moderate- grade fever, and dyspnea. Levofloxacin was initiated after 2 sets of blood cultures grew gram-variable coccobacilli the next day. She had a history of bicuspid aortic valve endocarditis due to Haemophilus aphrophilus 24 years ago and had aortic valve homograft placement 15 years ago. Three years ago, she had mechanical mitral and composite aortic root replacement and tricuspid annuloplasty with subsequent anticoagulation and a single ventricular lead pacemaker implantation for atrial fibrilla- tion and heart block. She was admitted to our hospital 2 days later. Medica- tions included levofloxacin, warfarin, levothyroxine, aspirin, and multivitamins. She had a grade 3/6 midsystolic murmur at the left upper sternal border without any clinical evidence of embolic phenomenon. There was slight leukocytosis (10.7 Â 10 9 leukocytes per liter, 83% neutrophils) with elevated erythro- cyte sedimentation rate (75 mm/h) and C-reactive protein level (349 mg/L). Vancomycin, cefepime, rifampin, and gentamicin were started instead of levofloxacin. Rifampin and gentamicin were discontinued the next day when the blood culture isolate was reported to be a gram-negative oxidase-positive bacillus. A two-dimensional transesophageal echocardiogram (TEE) with Doppler imaging on day 2 of inpatient antibiotic therapy showed a homogenous crescentic echodensity (È1.4 Â 3.6 cm) sur- rounding the aortic root consistent with perivalvular extension of infection and mobile echodensities on the pacing lead 1-cm proximal to the superior vena cavaYright atrial junction sug- gestive of thrombus or vegetation. Repeated TEE on day 7 showed the crescentic echodensity to be slightly smaller, pacing lead densities no longer seen, and no fistulous connections or vegetations. The culture isolate was procured. Preliminary report suggested it to be Kingella kingae but was later confirmed as N. elongata subspecies nitroreducens: nonmotile, biochemical profile positive for oxidase and nitrate reductase and negative for catalase, urease, lysine decarboxylase, arginine dihydrolase, ornithine decarboxylase, and oxidative fermentation of glucose, maltose, and xylose. The identification was confirmed by 16S recombinant DNA (rDNA) sequencing. Following in vitro anti- biotic susceptibility results, vancomycin and cefepime were discontinued, and ceftriaxone was started to complete a total antibiotic course of 42 days. Repeated TEE on day 42 and blood cultures on days 50 and 72 were unremarkable, and the patient had no signs of endocarditis relapse. REVIEW ARTICLE Infectious Diseases in Clinical Practice & Volume 00, Number 00, Month 2010 www.infectdis.com 1 From the Division of Infectious Diseases, Department of Medicine, Mayo Clinic College of Medicine, Rochester, MN. Correspondence to: Dr. Walter R. Wilson, MD, Division of Infectious Diseases, Mayo Clinic, 200 First St. SW, Rochester, MN 55905. E-mail: wilson.walter@mayo.edu. The authors have no funding or conflicts of interest to disclose. Ethics review/informed consent is not applicable. Copyright * 2010 by Lippincott Williams & Wilkins ISSN: 1056-9103 Copyright © 2010 Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.