Rat-bite Fever: A Rare Diagnosis for a Common Pediatric Presentation: Case Report

Introduction: Fever and rash is a common pediatric presentation to the emergency department but can present a diagnostic challenge to the clinician. Here we report the successful identification and treatment of a rare zoonotic exanthem that was facilitated by a thorough history and physical exam. Case Report: Rat-bite fever is a potentially fatal systemic illness characterized by relapsing fever, rash, and migratory polyarthralgias. Treatment includes antibiotics for Streptobacillus moniliformis, the most common pathogen, as well as appropriate hygiene education and prevention strategies. We report a case of S. moniliformis in the absence of an actual rodent bite. Conclusion: Due to the generally non-specific presentation of the illness, as well as the growing trend of caring for domestic rodents, it is crucial that clinicians ask details related to zoonotic and other exposures while obtaining medical histories.

Rat-Bite Fever: Developing and testing a modified time-kill protocol based on Edberg and Edberg 1983 experiemnt in order to test S. moniliformis growth in 0.05% SPS and proposed growth curve

Introduction/Objective Streptobacillus moniliformis is the primary causative agent of rat-bite fever (RBF) and Haverhill fever (HF). Rat-bite fever and Haverhill fever are difficult to diagnose in a clinical setting and are likely severely under-represented and under-reported worldwide. Clinical presentation often includes fever, chills, myalgia, headache, and vomiting. Patients may also develop a maculopapular rash covering their extremities approximately 2-4 days after onset of fever followed by polyarthritis in roughly 50% of patients with a mortality rate of 10-13% if left untreated. This is further complicated by the fact that submission and processing guidelines of clinical samples for the recovery of the organism are based on ‘outdated’ techniques and clinical laboratory methods that are over 50 years removed from current procedures, instrumentation and guidance. Methods/Case Report DNA from collected frozen time-point samples, were collected (n=84) and extracted using an in-house custom protocol utilizing 180 µl of bacterial lysis buffer with 20 µl of PCR grade proteinase K, for a total of 200 µl. The blood culture time-point samples were then thawed on ice, and 200 µl of blood culture sample was then added to the lysis mix, vortexed and incubated at 65°C for 10 minutes (an additional 95°C inactivation step was omitted to avoid whole blood clotting). After incubation, each sample was vortexed briefly again and extracted using the Roche automated MagNA Pure Compact instrument with an initial input volume of 400 µl and stored in a final elution buffer volume of 100 µl. All quantatitive time kill data was colleced via a CDC in-house designed PCR assay developed for S. moniliformis. Results (if a Case Study enter NA) Experimenting with varying amounts of blood inoculum, 10 ml of blood was determined to provide the best results for detection and growth/viability as well as propose a theoretical growth curve for the organism. Conclusion We found that in 100% of the isolates tested (and all the variations of testing within), SPS (up to a concentration of 0.05 % w/v) in commercially available blood culture bottles appeared to be inactivated, allowing for the growth detection and culturing of S. moniliformis using an automated continuous blood culture system when 10 ml of blood was inoculated.

Rat bite fever due to Streptobacillus notomytis complicated by meningitis and spondylodiscitis: a case report

Background Only three other cases of rat bite fever caused by Streptobacillus notomytis in humans have been reported since this species was identified in 2015. Data specific to the differences in clinical features and geographic distribution between S. notomytis infection and S. moniliformis infection are scarce. All previous cases of human S. notomytis infection were reported from Japan. This is the first case of S. notomytis infection reported from outside of Japan. Case presentation A 72-year-old Thai woman was admitted to Siriraj Hospital (Bangkok, Thailand)—Thailand’s largest university-based national tertiary referral center—in August 2020 with fever, myalgia, and polyarthralgia for 3 days, and gradually decreased consciousness for the past 1 day. Physical examination and laboratory investigations revealed septic arthritis of both knee joints, meningitis, and hepatitis. She was initially misdiagnosed as rheumatoid arthritis in the elderly since the initial investigations were unable to detect a causative pathogen. However, S. notomytis infection was later confirmed by polymerase chain reaction amplification of a part of the 16S rRNA gene and sequencing from synovial fluid. Her clinical course was also complicated by spondylodiscitis and epidural abscess caused by S. notomytis, which was detected from tissue biopsy. Therefore, rat bite fever in this patient manifested as meningitis, septic polyarthritis, hepatitis, and spondylodiscitis. The patient was treated with intravenous ceftriaxone then switched to oral amoxicillin with complete recovery. Conclusions The clinical manifestations of S. notomytis infection are similar to those demonstrated in S. moniliformis infection. This case also showed that arthritis caused by S. notomytis mimics rheumatoid arthritis, and that meningitis and spondylodiscitis are potential coexisting complications that can be found in S. notomytis infection.