Case report: A fatal case of aortic and mitral valve endocarditis caused by Streptobacillus moniliformis

Septic arthritis complicating Streptobacillus moniliformis rat bite fever: a case report and review of its pathophysiology and diagnosis

Rat bite fever is characterized by a clinical triad of symptoms, fever, rash and arthritis. It is transmitted by rodents and mainly due to infection by Streptobacillus moniliformis, a fastidious bacterium carried by Rattus norvegicus. This case report presents the case of a patient who developed septic arthritis and fever after a wild rat bite, with subsequent isolation of S. moniliformis from the joint fluid. Upon reviewing 45 other published case reports of S. moniliformis osteoarticular infections following contact with either a rat or its secretions, it was firstly observed that the rat bite fever clinical triad was incomplete in over half of the cases, mainly because rash was infrequently observed among adult patients. Secondly, the clinical presentation of rat bite fever is quite non-specific and rodent exposure is not mentioned by patients in a third of cases upon admission. Altogether, diagnosing rat bite fever is a significant clinical challenge suggesting that it might be significantly underdiagnosed. In addition to these clinical aspects, no evidence was found supporting immunological mechanisms, as suggested in some literature. Instead, when excluding five improperly performed cultures, S. moniliformis was cultured in 25 reported cases and identified twice by direct PCR sequencing amounting to a detection rate of 90% (n = 27/30) on joint fluids. Cultures should be performed in medium containing yeast extract, complete peptic digest of animal tissue and at least 5% blood. Knowing that S. moniliformis is very sensitive to many antibiotics thereby making the culture negative, direct 16S rRNA gene sequencing on joint fluid is an alternative method in the case of clinical and cytological evidence of osteoarticular infections with sterile culture of joint fluid.

[New awareness for zoonoses using the example of rat bite fever : Case report and literature review]

BACKGROUND

Rat bite fever is a rare but potentially fatal bacterial zoonosis. The symptoms can be unspecific, but severe sepsis can be associated with involvement of different organs.

CASE REPORT

A 27-year-old homeless man presented with fever, suspected meningitis, acute renal failure, unclear skin lesions as well as joint problems and muscular pain. Bite wounds were not detected. Meningitis could be excluded after lumbar puncture, and there was no evidence of endocarditis as the cause of the skin lesions. After 72 h, growth of Streptobacillus moniliformis in blood cultures was detected. Clinical symptoms were compatible with the diagnosis of rat bite fever. Calculated antibiosis with ampicillin sulbactam and doxycycline led to regression of the symptoms.

CONCLUSION

Rat bite fever poses a diagnostic challenge due unspecific symptoms, diverse differential diagnostic options, and challenging microbiological detection. Patient history is of the utmost importance. Due to the rarity of the disease, this case report is intended to raise awareness.

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

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.