The genus Erysipelothrix has 2 species, Erysipelothrix rhusiopathiae and Erysipelothrix tonsillarum. Erysipelothrix rhusiopathiae has a long history as a pathogen of humans and animals, especially pigs. These small gram-positive bacilli are facultative anaerobes, nonspore forming, and non-acid-fast.1 Three forms of human disease have been recognized. These include a localized cutaneous form, erysipeloid, a generalized cutaneous form, and a septicemic form often associated with endocarditis.1,2 Invasive infections with this organism are unusual and more serious and manifested primarily as infective endocarditis. All reported cases of endocarditis, except 1 recent case of infection involving a Starr-Edwards prosthetic aortic valve, have involved native valves. To date, a literature search revealed 56 case reports of E. rhusiopathiae endocarditis.3-7 Only 1 case report of E. rhusiopathiae endocarditis has been documented from India.8 Hence, we report a case of cerebral artery aneurysm associated with E. rhusiopathiae endocarditis involving native mitral valve.
A 37-year-old man was admitted in the neurosurgery department with a history of sudden onset of severe headache, altered sensorium, and left-sided hemiparesis. There was a history of fever with cough and expectoration on and off for 3 months. There were no skin lesions, nor was there any history suggestive of them. The occupational history was that he was a cinematographer. There was no history of animal handling other than having a pet dog at home. He lives on a tiny island off the coast of Kochi in Kerala, predominantly inhabited by fishermen.
Clinical examination revealed him to be afebrile, conscious, well oriented, with normal blood pressure (140/70 mm Hg), and heart rate (75 beats per minute). The pupils were equal and reacting to light. Left upper motor neuron (grade 2) facial paresis and left hemiplegia (grade 0/5) were present. Laboratory investigations revealed the following: white blood cell count, 14.2 K/μL; neutrophil, 84.8%; lymphocyte, 6.66%; hemoglobin, 10 g/dL; erythrocyte sedimentation rate, 34 mm/h; urea, 21 mg/dL; creatinine, 0.5 mg/dL; sodium, 137 mmol/L; bilirubin, 0.1 mg/dL; total protein, 6.4 g/dL. Computed tomographic (CT) scan of the brain showed hemorrhage in the right putamen with midline shift and mass effect. He was treated with antiedemic measures and antiepileptics. A repeat CT of the brain done after 11 days of treatment showed resolving hematoma with decreasing mass effect. The patient was discharged after 14 days of hospitalization with advice to continue medications and physiotherapy and was asked to come back for a review a month later. However, after 1 week, he presented with an episode of seizure lasting for 30 minutes, followed by worsening of left hemiparesis. Physical examination revealed him to be afebrile, drowsy, and with left hemiparesis (grade 2). Pupils were equal and reactive to light. The CT scan was performed that showed right temporoparietal hematoma with perilesional edema. Four-vessel digital subtraction angiogram done on the seventh day of hospitalization revealed right middle cerebral artery saccular multiloculate aneurysm measuring 21 × 16 mm, arising from M3 segment, in the intrasylvian region, suggestive of mycotic aneurysm (Fig. 1). Hence, he was referred to cardiology for evaluation. Clinical examination revealed pansystolic murmur at apex. Echocardiogram showed severe mitral regurgitation with vegetations over anterior and posterior mitral leaflets (Figs. 2, 3).
Five blood culture samples collected on different days grew gram-positive bacilli. Intravenous ampicillin and gentamicin therapy were initiated. Aneurysm clipping was done by neurosurgery team 3 days after initiation of antibiotics (11 days of hospitalization). Histopathology of the biopsy specimen showed acute on chronic inflammatory lesion with granulation tissue formation, blood clot, and organizing thrombus. After 3 weeks of ampicillin and gentamicin, he developed rashes, necessitating their discontinuation and starting of ceftriaxone. He completed 6 weeks of antibiotic course. Repeat blood cultures done after completion of antibiotic course were negative. He was discharged with advice to continue physiotherapy and prophylaxis for infective endocarditis. The patient was reviewed after 2 months; blood cultures repeated were negative, and echocardiogram done showed linear healed vegetation on posterior mitral leaflet.
A Gram stain of positive blood culture bottles (Aerobic BACTEC) showed gram-positive bacilli. Subculture was done on MacConkey agar, chocolate agar, and sheep blood agar. After 24 hours, tiny smooth colonies appeared on blood agar and chocolate agar. MacConkey agar showed small pinpoint colonies. Plates were further incubated for 24 hours. Nonhemolytic small translucent colonies were noted on blood agar and chocolate agar. Gram smear from colony showed gram-positive thin bacilli and a few filamentous forms (Fig. 4). Metachromatic granules were absent. It was nonmotile at 37°C and 4°C, catalase, and oxidase negative. Hydrogen sulfide production was noted on triple sugar iron slant after 48 hours of incubation. It fermented glucose and lactose with no gas. Mannitol, sucrose, salicin, and xylose fermentation were negative. Nitrate, methyl red, Voges-Proskauer, gelatinase, esculin hydrolysis, and arginine hydrolysis were also negative. Based on the morphology, cultural characteristics, and biochemical reactions, the organism was identified as E. rhusiopathiae. Sensitivity test was done by Kirby-Bauer method on Mueller Hinton agar.9 It was sensitive to penicillin, ampicillin, ceftriaxone, cefotaxime, vancomycin, erythromycin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, gentamicin, clindamycin, and ofloxacin.
Erysipelothrix rhusiopathiae is a commensal or pathogen in a wide variety of wild and domestic animals, birds, and fish. Most human cases are related to occupational exposure. Individuals at the greatest risk of infection include butchers, fish handlers, veterinarians, abattoir workers, and housewives. Most cases in humans and animals probably occur via scratches or puncture wounds of the skin. Human disease can originate from an animal or environmental source. Human-to-human infection has not been documented.1,2 Erysipelothrix rhusiopathiae endocarditis is associated with the characteristic skin lesion (erysipeloid) at the site of inoculation in 40% of patients. Etiologic diagnosis is made on the basis of blood cultures, which are always positive. In this case, there was no history suggestive of occupational exposure. The exact source of infection could not be located; 1 possible source is the environment because the patient, although not a fisherman himself, hails from an island where fishing is the main occupation, and the other possible source is a pet dog he had at home.
Erysipelothrix rhusiopathiae is a gram-positive bacterium but easily decolorized. Two distinct morphological forms grow on solid media. Smooth colonies are bluish, transparent, and convex. Microscopically, these appear as small slightly curved slender rods with rounded ends approximately 0.8- to 2-μm long and 0.2- to 0.4-μm wide. Rough colonies are larger and have a flat rough surface with irregular edges; on microscopy, long filaments longer than 60 μm predominate. Most strains exhibit a narrow zone of α-hemolysis on blood agar, and β-hemolysis is never observed.1,2
Erysipelothrix rhusiopathiae can be differentiated from other gram-positive bacilli, in particular, from Arcanobacterium (Corynebacterium) haemolyticum and Arcanobacterium (Actinomyces) pyogenes, which are β-hemolytic on blood agar and do not produce hydrogen sulfide in triple sugar iron agar slants, and from Listeria monocytogenes, which is catalase positive, motile, and sensitive to neomycin.10
Neurological manifestations occur in 16% to 23% of patients with infective endocarditis, and intracranial aneurysms have been noted among 2% to 10% of these. Most often, they are located on the distal branches of middle cerebral artery and are multiple and bilateral.11,12 During initial admission, he presented with sudden onset of neurological manifestations. Although detailed clinical evaluation and laboratory investigations were done, blood cultures were not drawn. The second time he was admitted, he presented with left-sided hemiparesis. Investigations revealed cerebral artery aneurysm, and, on evaluation, infective endocarditis of native mitral valve origin was detected. Multiple blood culture samples collected during this period grew E. rhusiopathiae.
The clinical picture of an E. rhusiopathiae septicemia, often associated with endocarditis, includes fever, peripheral skin stigmata of endocarditis, emboli, splenomegaly, hematuria, and mycotic aneurysm. Congestive cardiac failure is the common complication in 80% of the patients. Myocardial abscesses and aortic valve perforation, diffuse glomerular nephritis, and meningitis have also been reported. Endocarditis caused by E. rhusiopathiae carries high mortality rate of 38%, and valve replacement is necessary in one third of the patients.2
Erysipelothrix rhusiopathiae is highly susceptible to penicillin G, ampicillin, erythromycin, oleandomycin, cephalosporins, and clindamycin. Most strains are resistant to aminoglycosides, trimethoprim-sulfamethoxazole, polymyxins, sulfonamides, streptomycin, neomycin, novobiocin, and vancomycin. Penicillin G is the drug of choice. In penicillin-allergic patients, cephalosporins are the appropriate choice. It is extremely useful to perform minimal inhibitory concentrations for antibiotics of choice in treating the patient. The duration of therapy recommended is 4 to 6 weeks.2,3 Our isolate was multisensitive. Surgical management of aneurysm in addition to appropriate antibiotic therapy helped to improve his condition, although he had a lengthy hospital stay (65 days).
When a young patient presents with hemiparesis, it is crucial to rule out an infective cause. Only proper evaluation of the case helps in detection of causative agent for appropriate treatment, as in this case.
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