Infection in a Young Immunocompetent Male Caused by Streptobacillus felis, a Putative Zoonotic Microorganism Transmitted by Cats

Development and validation of a triplex real-time qPCR for sensitive detection and quantification of major rat bite fever pathogen Streptobacillus moniliformis

Streptobacillus (S.) moniliformis is the most important pathogen causing rat bite fever (RBF) worldwide. This zoonotic pathogen is understudied mainly due to difficulties in culturing S. moniliformis as a fastidious microorganism. Therefore, advances in molecular detection techniques are highly needed, especially with regard to the widespread availability of real-time quantitative (q) PCR in laboratories. In this study, we aimed to develop a qPCR for the identification of Streptobacillus species and quantification of S. moniliformis in clinical samples, especially those derived from tissue samples of animal origin. We optimized a previously described PCR protocol in order to develop a qPCR, which can detect different Streptobacillus species with high specificity and is simultaneously able to quantitate S. moniliformis in different clinical matrices. The qPCR exhibited a limit of detection (LOD) of 21 copies/reaction representing ~4-5 streptobacilli, while the limit of quantification (LOQ) was 2.1 × 10³ copies/reaction. It was also more sensitive than conventional PCR by two orders of magnitude and proved to have a substantial agreement (Kappa 0.74) compared to it with a superior detection rate in 374 samples from wild rats, laboratory rats and animals from holdings of wild-trapped rats. To conclude, the qPCR described in this study is an important molecular tool that is able to quantify S. moniliformis in tissue samples of animal origin. It represents a suitable tool for future establishment and evaluation of other molecular assays that are highly needed for a better understanding of epidemiology and pathophysiology of RBF. In experimental studies, it will also be useful for titration purposes since the quantification of the organism using classical plate counting technique is problematic and inaccurate.

Rat Bite Fever: Variability in Clinical Presentation and Management in Children

Rat bite fever is a systemic illness most commonly caused by Streptobacillus moniliformis that is classically characterized by fever, rash and migratory polyarthritis. Here, we highlight the highly variable clinical presentations of rat bite fever in children and the importance of maintaining a high degree of suspicion so appropriate treatment can be promptly initiated.

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.

A real-time multiplex PCR assay for detection of the causative agents of rat bite fever, Streptobacillus moniliformis and zoonoticStreptobacillus species

Rat bite fever (RBF) caused by Streptobacillus moniliformis has been described as a diagnostic challenge. While it has a favorable prognosis with treatment, timely diagnosis is hindered by the lack of culture-free identification methods. Here we present a multiplex real-time PCR assay that detects the zoonotic Streptobacillus spp. as well as differentiate the primary causative agent of RBF, Streptobacillus moniliformis. The performance of this assay was evaluated using mock clinical specimens for blood, serum, and urine. Analytical sensitivity was determined to be 3-4 genome equivalents (GE)/µl for the zoonotic Streptobacillus spp. target, and 1-2 GE/µl for the S. moniliformis specific target. The assay correctly detected only the intended targets with no cross-reactivity identified. The pathogen was detected in all spiked matrices and not detected in the negative non-spiked specimens. This rapid diagnostic assay may permit quicker diagnosis of RBF patients.

Streptobacillus felis, a member of the oropharynx microbiota of the Felidae, isolated from a tropical rusty-spotted cat

Streptobacillus felis is a fastidious microorganism and a novel member of the potentially zoonotic bacteria causing rat bite fever. Since its description, this is the second isolation of S. felis in a diseased member of the Felidae. Interestingly, the strain from this study was isolated from a zoo held, rusty-spotted cat (Prionailurus rubiginosus), with pneumonia, thereby indicating a possible broader host range in feline species. A recent preliminary sampling of domestic cats (Felis silvestris forma catus) revealed that this microorganism is common in the oropharynx, suggesting that S. felis is a member of their normal microbiota. Due to unawareness, fastidiousness, antibiotic sensitivity and lack of diagnostics the role of S. felis as a cat and human pathogen might be under-reported as with other Streptobacillus infections. More studies are necessary to elucidate the role of S. felis in domestic cats and other Felidae in order to better estimate its zoonotic potential.