Rat bite fever caused byStreptobacillus moniliformisin a child: human infection and rat carriage diagnosed by PCR

Abstract

A child owning pet rats developed an eruptive fever with blisters, polyarthritis, and spectacular desquamation of the hands. Streptobacillus moniliformis was identified after culture of the child's blister fluid and was detected in rat samples by molecular methods. Such detection in the pet of a human victim of rat bite fever has not been reported previously.A 7 year old boy presented with fever, rash on the extremities, and intense bilateral arthralgia in the knees, ankles, elbows, and wrists. Physical examination showed maculopapular morbilliform exanthema on the palms and soles, associated with several blisters 3-8 mm in diameter, containing a whitish fluid, on the face and elbows. None of the painful joints was mobilisable. The right knee and both ankles were swollen.Laboratory investigations showed an intense inflammatory syndrome (C reactive protein, 300 mg/litre; erythrocyte sedimentation rate, 60 mm/hour), normal leucocyte count, and normal cerebrospinal fluid examination. Samples of cerebrospinal fluid, blood, and blister fluid were cultured.Possible diagnoses included rat bite fever (RBF). One month before onset the patient had acquired two pet rats. His parents reported frequent physical contact between the boy and his pets, but they were not aware that he had been bitten.Pending the laboratory results, empirical intravenous combination treatment was started with erythromycin (30 mg/kg/day) and amoxicillin (100 mg/kg/day).Serological tests were negative for Mycoplasma pneumoniae, Francisella tularensis, Leptospira spp, and Rickettsia spp. Polymerase chain reaction (PCR) analyses were negative for Rickettsia spp and Leptospira interrogans.Blood and cerebrospinal fluid cultures remained sterile. However, blister fluid samples yielded smooth, shiny, grey colonies 1-2 mm in diameter on horse blood agar plates incubated in aerobic conditions, and on Columbia blood agar incubated in anaerobic conditions, after 48 hours at 36˚C. Microscopic examination showed pleomorphic Gram negative rods. Tests for oxidase, catalase, nitrate reductase, and urease were negative. Because growth was slow, despite serum enrichment, biochemical identification was not possible and antibiotic susceptibility testing was also unsuccessful.The isolate was finally identified using a broad range PCR technique based on amplification and sequencing of bacterial 16S ribosomal DNA.1 The amplified DNA of the isolate showed 99% similarity with the Genbank Streptobacillus moniliformis sequence Z35305 (type strain ATCC16467).After five days of antibiotic treatment, the patient's general status improved. At this time he developed spectacular bilateral desquamation of the fingers and toes (fig 1). The echocardiogram was normal, arguing against atypical Kawasaki disease. Erythromycin and amoxicillin were discontinued after seven and 15 days, respectively, without symptom recurrence. The patient was seen 15 days after discharge, and his physical examination was normal. He admitted at this time that he used to eat his pets' faeces.One of the appar...

Rat‐bite fever identified by polymerase chain reaction detection of Streptobacillus moniliformis DNA

“…1,2 Recently, the use of PCR has made definitive diagnosis possible by allowing identification of S. moniliformis DNA in patients' samples, 1 synovial fluid, blister fluid or cardiac tissue. [3][4][5] In the present case, PCR detected S. moniliformis DNA from the crust of the bite sites but not from the blood. This led to the definitive diagnosis of rat-bite fever.…”

“…The S. moniliformis strain can be isolated using blood or joint fluid culture, but the need for a specific culture medium often makes isolation difficult 1,2 . Recently, the use of PCR has made definitive diagnosis possible by allowing identification of S. moniliformis DNA in patients’ samples, 1 synovial fluid, blister fluid or cardiac tissue 3–5 …”

Streptobacillus moniliformis septic arthritis: a clinical entity distinct from rat-bite fever?

“…These methods include gas-liquid chromatography analyzing the cellular fatty acid profile of the isolate [18,29,30], and molecular methods like 16S rRNA sequencing and polymerase chain reaction (PCR) amplification [23,31,32]. These molecular methods can also be used in typing isolates of S. moniliformis from humans and rodents, and thus identifying the source of infection even in the absence of known rat bite [33]. …”

Rat Bite Fever andStreptobacillus moniliformis

“…The PCR assay generated a 296-bp product which, when discriminated by BfaI restriction enzyme treatment, generated three fragments (128, 92, and 76 bp) specific to S. moniliformis. This assay has been used by others to examine both human-and animal-derived specimens and has been found to distinguish S. moniliformis from other organisms with great accuracy (4,11,85). However, until such an assay becomes more readily available, a diagnosis of S. moniliformis-associated rat bite fever requires a high clinical index of suspicion coupled with the appropriate use of culture and attention to ruling out alternate diagnoses.…”

“…Although these assays are sufficiently sensitive, the increasing demand for rapid, more-sensitive tests likely has detracted from their utility. Molecular methods such as PCR show promise and have been used successfully with humans and laboratory animals (4,7,11,43,85). A PCR assay specific for S. moniliformis has been described by Boot et al (11); it uses primers designed on the basis of 16S rRNA gene base sequence data of human and rodent strains of S. moniliformis (forward primer, 5Ј GCT TAA CAC ATG CAA ATC TAT 3Ј; reverse primer, 5Ј AGT AAG GGC CGT ATC TCA 3Ј).…”