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. 2023 Apr 10;13:e2023423. doi: 10.4322/acr.2023.423

A Rodential Reckoning: A Case Report and Systematic Review of Streptobacillary Endocarditis

Ashwin Mahesh 1,✉, Eduardo Messias Hirano Padrao 1, Ravneet Randhawa 1, Christi Oommen 1, Johanna Romo 1, Ramachandra Illindala 2, Henry Anyimadu 3
PMCID: PMC10124564  PMID: 37101553

ABSTRACT

Introduction

Endocarditis is a rare, often fatal complication of rat bite fever caused by Streptobacillus moniliformis. Only 39 cases have been reported (including this case) as of 2022. We describe a case and aim to perform this entit’s first systematic literature review.

Methods

We performed a systematic review in CENTRAL, EMBASE, MEDLINE, SciELO, and LILACS. The terms used were terms used were (but not limited to) rat bite fever, Streptobacillus moniliformis, Spirillum minus, and endocarditis. We included all abstracts and articles with patients with echocardiographic or histologic-proven endocarditis. In case of discordance, a third reviewer was involved. Our protocol was submitted to PROSPERO (CRD42022334092). We also performed searches for studies on the reference list of included articles.

Results

We retrieved 108 and included 36 abstracts and articles. A total of 39 patients (including our report) were identified. The mean age was 41.27, and 61.5% were males. The most common findings were fever, murmur, arthralgias, fatigue, splenomegaly, and rash. Underlying heart disease was present in 33%. Exposure to rats was noted in 71.8% of patients, with 56.4% recalling a rat bite. Anemia was seen in 57%, leukocytosis in 52%, and elevated inflammatory markers in 58% that had lab work performed. The mitral valve was most affected, followed by the aortic, tricuspid, and pulmonary valves. Surgical intervention was required in 14 (36%) cases. Of those, 10 required valve replacement. Death was reported in 36% of cases. Unfortunately, the literature available is limited to case series and reports.

Conclusion

Our review allows clinicians to suspect better, diagnose, and manage Streptobacillary endocarditis.

Keywords: Rat Bite Fever, Streptobacillus moniliformis, Spirillum minus, Endocarditis

INTRODUCTION

Rat bites have historically been associated with febrile disease, with rat bite fever (RBF) being an entity described in medical literature for about 2300 years, first reported in India.1 Rodents carry microorganisms in their oral and nasopharyngeal membranes, which can inoculate humans through bites or transdermal contact with urine or feces.2

These diseases were initially identified amongst rural communities and populations traditionally exposed to rodents. The advent of pet-keeping and the rise of occupations involving contact with rats, notably laboratory and pet shop workers, in the 21st century led to recent shifts in epidemiological trends in the western world.3 The disease has also been noted among snake-keepers, and some authors suggest that rat-consuming snakes could be temporary reservoirs for human infections.4 RBF has been attributed to two species of bacteria, Streptobacillus moniliformis, and Spirillum minus.1Spirillum minus has been documented in Asian countries, causing the Sodoku disease, which roughly translates to “rat-poison”.2Streptobacillus moniliformis has been documented in North America5 causing streptobacillary RBF if transmitted through bites. The disease transmitted via contaminated food or water has been described as Haverhill fever, a name derived from a town in Massachusetts wherein contamination of the raw milk at a local dairy farm gave rise to an epidemic among schoolchildren in 1926.6Streptobacillus moniliformis is a non-motile, microaerophilic, Gram-negative rod-shaped bacterium that is a member of the family Leptotrichiaceae. It exhibits slow growth on anaerobic blood cultures, making laboratory identification challenging.3,7

RBF is a rare disease with a mortality rate of 13%.1 The mortality rate is higher with complications like septic shock and endocarditis. The data on endocarditis is limited owing to the rarity of the disease, possible underdiagnosis, and underreporting. To our knowledge, only 38 cases have been reported between 1915 and 2022. We describe a patient who presented with an acute stroke weeks after she said being bitten by a rat and was later found to have infective endocarditis of her native mitral valve with cultures yielding Streptobacillus moniliformis. We also present a systematic review of all the cases of Streptobacillus moniliformis endocarditis reported to date.

CASE REPORT

A 75-year-old healthy, independent Caucasian female presented from home, endorsing worsening back pain for a week that limited her ability to walk around the house. She mentioned being bitten by a pet rat a few weeks prior, with subjective fevers and chills lasting for a few days after the bite without accompanying rashes or skin changes. She denied a personal history of intravenous drug use. She did not have previous valvular surgeries or any previous valvular lesions. Her medical history included osteoarthritis and hypertension.

At the emergency room, vitals were significant for a temperature of 37.6C, and pulse was measured at 86 beats per minute, respirations at 18 breaths per minute, blood pressure at 110/64 mm Hg with 97% oxygen saturation on room air. Her physical exam was significant for a systolic 2+ high-pitched murmur on the left fifth intercostal space on the midclavicular line. Her oral exam revealed poor dentition with caries, and the site of her reported rat bite on her right index finger showed a small well-healed wound. Labs on admission revealed a white blood cell count of 11.8x103/mm3 (reference range [RR]: 4-11.8x103/mm3), hemoglobin 10.1 g/dL (RR: 13-17.7g/dL), platelets 220x103/mm3 (RR: 150-450x103/mm3), sodium 138 mEq/L (RR: 136-145 mEq/L), potassium 3.5 mEq/L (RR: 3.4-5.3 mEq/L), blood urea nitrogen 15 mg/dL (RR: 8-21mg/dL), creatinine 0.5 mg/dL (RR: 0.5-1.3 mEq/L). High-sensitivity troponins were initially measured at 59.22 ng/L (RR: <14ng/L), with a repeat drawn a few hours later measured at 57.78 ng/L. An electrocardiogram on admission revealed sinus rhythm with no concerning ST-T wave changes with a few premature atrial contractions at a rate of 98 beats per minute. A chest X-ray revealed bibasilar opacities concerning atelectasis.

Cardiology was consulted for the troponin leak and recommended a transthoracic echocardiogram that revealed a preserved ejection fraction with no regional wall abnormalities. Valvular vegetations were initially not discerned. Given the absence of clinical features of the acute coronary syndrome, conservative management was pursued with plans for an outpatient ischemic evaluation.

On day three of hospitalization, she underwent a spine MRI that revealed a herniated disc at T11/T12. Following the scan, she experienced a new onset of verbal aphasia. CT imaging and angiography of the head and neck were unremarkable. She spiked a fever of 39.3C later that day. After repeat blood cultures, she was started on ceftriaxone and azithromycin for suspicion of lobar pneumonia based on new infiltrates on a repeat chest x-ray. Given persistent aphasia, she underwent a brain MRI that showed acute infarcts in the left parietal and frontal lobes and cerebellum (Figure 1), consistent with an embolic etiology. A transesophageal echocardiogram revealed marked thickening of the posterior mitral leaflet with a 12 mm complex echodensity adherent to the atrial surface (Figure 2). This was accompanied by moderate eccentric and posteriorly directed mitral regurgitation.

Figure 1. FLAIR MRI section showing in A - strokes in the left cerebellar; and in B - left parietal (B) regions of the brain, concerning an embolic etiology. (FLAIR: Fluid Attenuated Inverse Recovery; MRI: Magnetic Resonance Imaging).

Figure 1

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Figure 2. Trans-esophageal echocardiography showing a 12 mm-sized mobile atrial vegetation with marked thickening of the posterior mitral leaflet.

Figure 2

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Blood cultures later revealed Gram-negative rods on the Gram stain in one of four bottles, speciated as Streptobacillus moniliformis. A peripherally inserted central line was subsequently placed, and she was prescribed a 6-week course of IV ceftriaxone at 1g/day. Her aphasia improved, and she was safely discharged with outpatient follow-up with Infectious disease.

METHODS

Two independent reviewers (AM and EMHP) performed a search in CENTRAL (Cochrane database), EMBASE, MEDLINE (PubMed), SciELO (Scientific Electronic Library Online), and LILACS (Latin American and Caribbean Health Sciences Literature). Terms used were, but not limited to “rat bite fever” (“rat-bite”, “rat bite”, “rat-bite fever”[Mesh], “ratbite”, “Sodoku”, “Haverhill”), Streptobacillus moniliformis, Spirillum minus, and endocarditis (“endocarditis” and “endocarditides”). Further details regarding the keywords have been provided in the Supplement Appendix.

The search was performed between April 28th to 30th, 2022. We included all abstracts and articles describing characteristics of patients with echocardiographic or histologic-proven (biopsy or autopsy) endocarditis due to Streptobacillus moniliformis or Spirillum minus. The pediatric and adult populations were included. Duplicated retrievals were excluded. In case of discordance, a third reviewer (CO) was involved in a final decision. We excluded articles, not in English, Portuguese, French, or Spanish. We also searched for studies on the reference list of the included articles.

The information was extracted by AM and EMHP. It included sex, age, symptoms, laboratory findings, diagnosis of endocarditis, echocardiogram findings, involved valves, vegetation size, treatment and surgery performed, complications, and outcomes. Since this was a qualitative and systematic review, we did not perform a meta-analysis. Our protocol was submitted to PROSPERO (CRD42022334092).

RESULTS

We retrieved 108 results, and we included 36 abstracts and articles. Figure 3 shows the flow diagram according to PRISMA guidelines.

Figure 3. Flow diagram.

Figure 3

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There were a total of 39 cases reported7-41 (including our case). We excluded one duplicated case42. Table 1 presents the initial findings and work-up of rat bite endocarditis, while Table 2 presents the complications, treatment, and outcomes.

Table 1. Initial findings and work-up of rat bite endocarditis.

Year Age, Sex Heart Disease Rat Exposure Presentation Exam Work-up Echo Blood Cultures
19158 67; F None Rat Bite Fever Fever, rash, murmur NR None None
19349 18; M RHD NR NR NR NR None None
194010 14; F None Rat Bite Fever Fever, murmur Anemia None None
194411 43; M RHD Rat exposure without known bite Fever, rash Fever, rash, murmur NR None None
194512 22; M RHD NR NR Murmur, petechiae NR None None
194713 17; F NR NR NR NR NR None None
194912 40; M RHD Rat exposure without known bite Fever, fatigue, weight loss Murmur, splenomegaly, Osler nodes, water-hammer pulse, Duroziez sign Hg 11 g/dL, WBC 6500 x108 cells/L (PMN predominance), ESR 13 mm/hr, EKG with PVCs, LVH None None
194914 27; M RHD Handled a dead rat Fever, anemia Fever, murmur, splenomegaly, Osler nodes Anemia None None
195215 54; M None Rat Bite Fever, rash, headache, arthralgia, chest discomfort Fever, murmur, Osler nodes, nausea, documented rat bite WBC 17500 x108 cells/L, Hg 13.5 g/dL (PMN predominance) None None
196716 70; F Calcific Aortic Stenosis Unknown Fever, nausea and weight loss Murmur, splenomegaly Hg 8.8 g/dL, WBC 12300 x108 cells/L (PMN predominance) None None
196716 43; M NR Rat Bite Fever, arthritis, with pleuritic chest pain, heart failure Fever, murmur, cardiac tamponade (atrial fibrillation on EKG) Hg 13.8 g/dL, WBC 16500 x109 cells/L, None NR
196717 60; M RHD Rat exposure without known bite Fever, tonic-clonic generalized seizures, weight loss, altered mental status Fever, murmur, clubbing Hg 13.5 g/dL, WBC 14200 x108 cells/L (PMN predominance), CSF with 521 cells. None None
197418 55; F NR NR Anorexia, weakness and myalgia NR WBC 17,900 x108 cells/L with 76% PMN. None Positive
198119 41; M None Rat Bite Fevers, murmur, and heart failure NR NR None None
198520 3m; M None Rat Bite Fevers, lethargy, and arthritis Fever, hepatosplenomegaly, and indentation at site of reported rat bite Hg 11.3 g/dL, WBC 9800 x108 cells/L, interstitial pneumonia on chest imaging None None
198520 63; F None Rat Bite Fever, arthritis, paresis Fever, murmur NR None None
198621 8; M RHD None Fever, lethargy, weight loss Murmur, hepatosplenomegaly, clubbing WBC 12,500 x108 cells/L (PMN predominance) first degree AV block Aortic stenosis with regurgitation without vegetations None
198922 2m; M None Rat Bite Fever, pneumonia, “symptoms concerning for meningitis” Hepatosplenomegaly Electrolytes WNL on basic chemistry panel None None
199223 46; M None Rat Bite Fevers, back pain, arthralgia/arthritis Fever, murmur, hepatosplenomegaly Hg 10g/dL, WBC 8200 x108 cells/L (PMN predominance), ventricular bigeminism Thickened aortic valve Positive
200024 37; M None Rat Bite Arthralgia, fever and history of HIV Fever, pustules on skin Hg 9.3g/dL, WBC 6700 x108 cells/L, PMN predominance, platelets 195 x108 cells/L Vegetation on mitral valve with rupture Positive
200425 24; M None Patient reportedly scratched finger on a rat cage Fever, chills, myalgia, arthralgia, shortness of breath, vomiting, wound Wound on physical exam, murmur, and pericardial effusion WBC 16100 x108 cells/L, PMN predominance Aortic Valve Regurgitation Positive
200626 18; M Small VSD Rat Bite Fevers, cough, epistaxis, palpitations, and arthralgia Fever WBC 7,600 x108 cells/L, platelets 127,000 x108 cells/L, ESR 70 mm/hr Tricuspid Valve vegetation with small VSD Positive
200727 29; M None Rat Bite Fevers, dyspnea, dizziness, and somnolence Fever NR Large vegetations on the aortic valve. Severe Aortic regurgitation and LV dysfunction Negative
200728 74; F None NR Fever and murmur NR NR Severe Mitral Valve regurgitation with vegetation Negative
Positive mitral valve culture
200729 60; F Mechanical Mitral Valve Rat Bite Fever, leg wounds, weakness, and weight loss NR WBC 15,100 x109 cells/L, PMN predominance; Hg 8.2 g/dl; Platelets 134,000 x109 cells/L. CRP 162.9 mg/l, ESR 14 mm/h Mechanical mitral valve dehiscence with severe mitral regurgitation and vegetations Negative
201030 35; M Tetralogy of Fallot Rat Bite Vomiting and diarrhea followed by the development of debilitating migratory, asymmetric polyarthralgia, irregularly relapsing fevers Rash involving palms and soles A 2 cm vegetation on tricuspid valve and a 0.5 cm vegetation on the aortic valve Negative
201131 45; M None No Rash and right ankle pain Erythema WBC 28,760 x109 cells/L, PMN predominance Vegetation on mitral valve Negative
201332 44; M None Rat Bite Fever NR NR Mitral valve vegetation with severe regurgitation Positive
201433 49; M None None Fever, rash, leg swelling Pansystolic murmur, splinter hemorrhage Hb 10.5 g/dL, WBC WNL, CRP 117 mg/dL, HIV serology negative Mitral valve vegetation and thickening Positive
201734 19; M Tetralogy of Fallot Rat Bite Fever, chest pain, myalgias, weight loss NR NR Large fistula between right sinus of Valsalva and RV. Vegetations on VSD and tricuspid valve Negative blood culture, operative cultures positive
201835 52; F None Rat bite Lethargy, fever, sepsis, right knee and ankle arthritis Punctate opening in the heel of right foot WBC 22,600 x109 cells/L with PMN predominance, ESR 85 mm/hr, CRP >270 mg/dL Mitral valve vegetation with perforation and regurgitation Negative blood cultures, positive synovial fluid cultures, mitral valve cultures
201836 33; F None Rat Exposure Fever, arthralgia, myalgia, flu-like symptoms, dyspnea, murmur NR WBC 11,700, PMN predominance Left atrial mass with severe mitral regurgitation Positive
201837 7m; M Tetralogy of Fallot Rat bite Fever, hypoxia NR The initial blood work WNL, but mild elevation of CRP. Pulmonary valve vegetation, destruction of native pulmonary valve and pulmonary artery with aneurysm Negative
201938 47; M None None Pain and fever NR WBC elevation, inflammatory marker elevation Mitral and aortic insufficiency and vegetation Negative
201939 24; F None NR Bilateral lower extremity hemiparesis, bowel and urinary incontinence, weight loss, fever, dysarthria, limb ischemia Decubitus ulcer NR A 4.5 cm mitral vegetation Negative
202040 65; M None Rat bite Fevers, Myalgias, splenic abscess NR CRP 135 mg/L, Hb 7.3 g/dL, WBC 6400, Platelets 167,000 EKG with sinus rhythm and RBBB Severe mitral and Aortic vegetations with aortic root abscess Positive
20207 24; F None Rat Bite Pregnant women Murmur, splenomegaly Anemia, WBC WNL, arterial popliteal thrombosis, renal and splenic infarcts on imaging 2 cm mitral valve vegetation Negative
2021Our case 75; F None Rat bite Stroke, fever Murmur, rat bite on finger Hg 10.1 g/dL WBC 11.8 x108 cells/L, EKG with PACs 12 mm Mitral vegetation moderate mitral regurgitation Positive
202241 44; M None Rat Bite Arthralgias, lethargy, fevers, and rigors Fever NR 13 mm mitral valve mobile mass, mitral regurgitation Positive
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AV - atrioventricular; CRP - C-reactive protein; CSF - cerebral spinal fluid; EKG - electrocardiogram; ESR - erythrocyte sedimentation rate; Hg - hemoglobin; HIV - Human immunodeficiency virus infection; LV - left ventricle; LVH - left ventricle hypertrophy; m - month; NR - not reported; PAC - premature atrial contraction; PMN - polymorphonuclear; PVC - premature ventricular complex; RBBB - right bundle branch block; RHD - rheumatic heart disease; TOF - tetralogy of fallot; VSD - ventricular septal defect; WBC - white blood cell; WNL- within normal limits.

Table 2. Complications, treatments offered and outcomes.

Year Age, Sex Antibiotic Treatment Surgery Outcome
19158 67; F None None Died
19349 18; M None None Died
194010 14; F None None Died
194411 43; M Penicillin None Died
194512 22; M Penicillin None Died
194713 17; F Penicillin None Died
194912 40; M Penicillin None Cured
194914 27; M Penicillin and Chloramphenicol None Cured
195215 54; M Penicillin and Streptomycin for 3 weeks None Cured
196716 70; F Penicillin None Cured
196716 43; M Penicillin None Died
196717 60; M Penicillin None Cured
197418 55; F Cephalothin and gentamicin None Died
198119 41; M Penicillin, gentamycin None Sudden death 4 months after treatment
198520 3m; M No treatment None Died
198520 63; F Penicillin, amikacin None Cured
198621 8; M Penicillin per day None Cured, but died 2 months later due to rheumatic heart disease
198922 2m; M None None Died
199223 46; M Penicillin, tetracycline None Cured
200024 37; M Ceftriaxone for 3 weeks, gentamycin for 2 weeks and penicillin for 1 week None Cured
200425 24; M Ceftriaxone Debridement, aortic valve replacement Died
Second approach with new debridement and mitral valve repair
200626 18; M Penicillin, gentamycin for 4 weeks None Cured
200727 29; M Ampicillin, ceftriaxone, gentamicin Aortic Valve Replacement Cured
Post-operative Fosfomycin and gentamycin
200728 74; F Penicillin G for 4 weeks Mitral valve replacement Cured
200729 60; F Levofloxacin daily, ceftriaxone, gentamycin, oral doxycycline Mitral valve replacement Cured
201030 35; M Ampicillin, sulbactam and gentamicin None Cured
201131 45; M Cloxacillin, ampicillin and gentamicin, ampicillin for 5 days followed by piperacillin-tazobactam and vancomycin completing for 10 days. Mechanical mitral valve repair Cured
201332 44; M Doxycycline oral for two days, amoxicillin for one day, penicillin for 6 weeks with for 2 weeks None Cured
201433 49; M Penicillin and oral doxycycline Bioprosthetic mitral valve replacement Cured
201734 19; M 6 weeks of penicillin and two weeks of gentamicin Surgical repair, debridement, aortic mechanical valve replacement and bioprosthetic pulmonary valve replacement Cured
201835 52; F Vancomycin and piperacillin-tazobactam initially for septic arthritis, ceftriaxone for 6 weeks after Mitral valve repair Cured
201836 33; F Ceftriaxone Mitral valve repair Cured
201837 7m; M Ceftriaxone for 6 weeks None Cured
201938 47; M Piperacillin Tazobactam, azithromycin, clotrimazole followed by ceftriaxone and ampicillin with daptomycin. Mitral and Aortic Valve replacement Cured
201939 24; F Not mentioned antibiotic course, but received antibiotics Mitral valve replacement Cured
202040 65; M Cefuroxime, later switched to meropenem Bioprosthetic valve replacement of aortic, mitral valves, debridement of aortic root abscess Died
20206 24; F Penicillin for 6 weeks, amoxicillin-clavulanate for 2 weeks Mitral valve repair with band Cured
2021Our case 75; F Ceftriaxone for 6 weeks None Cured
202241 44; M NR Vegetectomy and mitral valve repair with bovine patch Cured
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NR - not reported.

The mean age was 41±17 years, and 61.5% of the patients were males. Four of them were younger than 18-year-old. Underlying heart diseases accounted for 13 cases (33%), and rheumatic heart disease was the most common (20.5%). Rat exposure history was present in 71.8%; however, only 56.4% of the patients were able to profess a history of a bite. The rat bite indentation was only seen in 3 cases (7.7%). Most common symptoms included fever (84.6%), murmur (54%), arthralgia/arthritis (31%), fatigue (31%), splenomegaly (20.5%), and skin findings (25.6%). When available, anemia was seen in 57%, leukocytosis in 52%, and elevated inflammatory markers were seen in 58%. The most common valve affected was the mitral valve (63.6%), followed by the aortic (31.8%), tricuspid (9%), and pulmonary (4.5%) valves. Embolization was reported in 6 cases. The most commonly used antibiotic was penicillin (48.7%), followed by ceftriaxone (23%). Other antibiotics include chloramphenicol, streptomycin, cephalothin, gentamicin, amikacin, tetracycline, doxycycline, piperacillin-tazobactam, ampicillin, levofloxacin, and others. In our review, surgical intervention was required in 14 (36%) cases; of those, 10 required valve replacement. Death was reported in 36% of cases. Table 3 summarizes the most common presentations, laboratory work-up, complications, echocardiogram findings, and mortality.

Table 3. Summary of findings.

Characteristic Frequency
Age (Mean - SD years) 41.27±17.4 years
Male Sex 24/39 (61.5%)
Rat Exposure 28/39 (71.8%)
Rat Bite 22/39 (56.4%)
Underlying Heart Disease 13/39 (33.3%)
Rheumatic Heart Disease 7/39 (17.9%)
Tetralogy of Fallot 3/39 (7.6%)
Ventricular Septal Defect 1/39 (2.5%)
Mechanical Valve 1/39 (2.5%)
Calcific Aortic Stenosis 1/39 (2.5%)
Signs and Symptoms
Fever 33/39 (84.6%)
Weight Loss 7/39 (17.9%)
Fatigue 12/39 (30.8%)
Murmur 21/39 (53.8%)
Myalgia 6/39 (15.4%)
Arthralgia/Arthritis 12/39 (30.8%)
Hepatomegaly 5/39 (12.8%)
Splenomegaly 8/39 (20.5%)
Rat Bite Punctate Lesion 3/39 (7.7%)
Skin Findings 10/39 (25.6%)
Laboratory Work-up
Anemia - Hemoglobin (Mean - SD) 12/21 (57.1%) 10.6±2.1g/dL
Leukocytosis - Mean WBC (Mean - SD) 11/23 (52.2%) 13550±5943/mm3
Inflammatory Markers Elevation* 7/12 (58.3%)
Embolization 6/23 (17.1%)
Echocardiogram Findings Valve Affected
Aortic Valve 7/22 (31.8%)
Mitral Valve 14/22 (63.6%)
Tricuspid Valve 2/22(9.1%)
Pulmonary Valve 1/22 (4.5%)
Mortality 14/39 (35.9%)
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SD - standard deviation.

*

Either CRP or ESR elevation.

DISCUSSION

The clinical features of RBF encompass a variety of non-specific symptoms, challenging the diagnosis. Notable symptoms documented were fevers in 30% of patients, arthralgias and arthritis in 49%, lymphadenopathy in 25%, and morbilliform or petechial rash in 75%.1,2 The onset of symptoms is usually as early as 3 days and up to 2-3 weeks after exposure.1,2 Endocarditis is a rare complication of RBF, and only 39 cases have been reported.7-42 Per our review, the mean age is 41 years, males are more affected, and children are affected in 50% of patients. As opposed to uncomplicated rat bite fever, streptobacillary endocarditis seems to have more specific symptoms. Rat bite fever usually manifests with fever, migratory polyarthralgia, and a rash, maculopapular or purpuric. Most patients with rat bite endocarditis present with a murmur, and almost one-fourth present with splenomegaly.2 Arthralgia, arthritis, and skin lesions are also common in rat bite endocarditis. The skin rash may also show findings typical of endocarditis, such as Osler nodes and splinter hemorrhages. As with any endocarditis,43 underlying heart disease seems to be a risk factor. Interestingly there were 2 case reports of Streptobacillus moniliformis leading to endocarditis in patients with Tetralogy of Fallot,30,37 and only one case in a patient with a mechanical valve.29

Unfortunately, concerning laboratory workup, almost one-third of the cases were reported in the first half of the 20th century [Cases Reported prior to1950], and many did not provide any laboratory workup. Anemia, leukocytosis, and elevated inflammatory markers are common findings.

The mitral valve is the most commonly affected valve accounting for 63.6% of the cases, followed by the aortic (31.8%), tricuspid (9%), and pulmonary (4.5%) valves. A similar pattern of valve involvement is seen in other infective endocarditis. Embolization does not seem to be a common phenomenon since there are only 4 cases, although the overall incidence of embolization in infective endocarditis, it is up to 44%.44 Organs affected in our series included the spleen, kidney, and brain.

Given the limited number of cases, there was variability in antibiotic choices for the treatment. The most commonly used antibiotic was penicillin. Ceftriaxone was the second most used antibiotic. Other antibiotics include chloramphenicol, streptomycin, gentamicin, amikacin, tetracycline, doxycycline, amoxicillin, piperacillin-tazobactam, cefuroxime, and meropenem. For our patient, we used ceftriaxone since it is considered one of the first-line antibiotics for rat bite fever with no endocarditis1 and has been extensively and successfully studied for other etiologies of endocarditis.43,45 The role of surgical intervention is based on factors like abscess formation >1cm, poor response to antibiotics, large vegetations with embolic events, and heart failure or the development of cardiogenic shock.43,45 In our review, surgical intervention was required in 14 cases. Of those, 10 required valve replacement.

Death has been reported in 13 cases (36%); however, 6 of them occurred in the first half of the 20th century, and only 7 of the deaths were patients who failed antibiotic therapy. The mortality of rat bite endocarditis is much higher when compared to uncomplicated rat bite fever, which, when untreated, can cause death in up to 13% of patients.1

CONCLUSION

This case comprises an interesting series of events that began with a rat bite and eventually culminated with the identification of vegetation on the valves of the heart and Streptobacillus moniliformis in the blood. Our systematic review aims to shed light on a rare complication of a disease with high morbidity and mortality. Understanding clinical profiles may help clinicians better suspect, diagnose, and manage Streptobacillary endocarditis.

ACKNOWLEDGEMENTS

Thomas Lane, MD; Madura Saravanan, MD; Rupal Panchal, MD; Kathryn Goldman, MD; Robert Levitz, MD.

Supplementary Material

Supplementary material accompanies this paper.

Supplement Appendix - Keywords
Click here for additional data file. (62.2KB, pdf)

This material is available as part of the online article from https://doi.org/10.4322/acr.2023.423

Footnotes

How to cite: Mahesh A, Padrao EMH, Randhawa R, et al. A Rodential Reckoning: A Case Report and Systematic Review of Streptobacillary Endocarditis. Autops Case Rep [Internet]. 2023;13:e2023423. https://doi.org/10.4322/acr.2023.423

This study was carried out at University of Connecticut.

Ethics statement: Consent was obtained from patient's power of attorney

Financial support: None.

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