Fever and Rash

Authors: Mayer JK 1 , Sundac L 2 , Derrington P 3 and Gerrard JG 4 1 Advanced Trainee, Infectious Diseases, Gold Coast University Hospital In a Rat Breeder 2Advanced Trainee, Infectious Diseases, Princess Alexandra Hospital Queensland 3Pathology Queensland, Gold Coast University Hospital Government 4Director, Infectious Diseases, Gold Coast University Hospital Gold Coast Health

Rat bite fever (RBF) caused by moniliformis is an emerging zoonotic . Classically, the disease is described in children living in poverty. Increasingly, it is recognised in rat owners and breeders, pet store workers and laboratory personnel. The clinical manifestations may be highly non-specific and the laboratory identification often difficult, therefore a history of potential rat exposure is often crucial for making the diagnosis.

ASE Arginine + C Oxidase - A 55-year old injection drug user presented to our service with a one-week history of fever, rigors, migratory Catalase - polyarthralgia and acral rash. On presentation, he was hypotensive and febrile. The most striking abnormality Urea - on examination was a tender, purpuric rash of the extremities including the palms and soles (figure 1). PYR - There was small joint tenderness without synovitis. Notably, there was no cardiac murmur. Indole - Initial investigations were remarkable only for a mild lymphopaenia. Blood cultures became positive at 63 hours, Nitrate - demonstrating pleomorphic gram negative bacilli (figure 2), which were identified as S. moniliformis based on Lactose - gram stain and biochemical characteristics (Table 1). The Vitek® 2 automated system was unable to identify the Sucrose - organism. Subsequent targeted history revealed that the patient bred rats for a living. ONPG - He was treated with a 14-day course of and made a full recovery. TABLE 1 BIOCHEMICAL CHARACTERISTICS

FIGURE 1 TENDER, PURPURIC RASH

Blue layered box theme

DISCUSSION

RBF was first described in 1839 and the causative pathogen, FIGURE 2 GRAM STAIN OF STREPTOBACILLUS MONILIFORMIS, 2 S. moniliformis, was identified in 1914. S. moniliformis is a fastidious, ISOLATED FROM PATIENT DAY INCUBATION ON AGAR slow growing organism, making culture diagnosis challenging. 6- CHOC S. moniliformis is a gram negative, highly pleomorphic, filamentous, non acid fast bacillus which is frequently fusiform with lateral bulbous swellings.(figure 2) These microscopic finding are quite characteristic.

RBF usually presents with non-specific clinical features and a broad differential diagnosis, which can delay directed therapy. Classically two syndromes are described; Haverhill fever, which is associated with outbreaks and is believed to be related to ingestion of contaminated food or drink 1; and RBF as in the above case, which results from percutaneous inoculation. Exposure to rat saliva, urine or faeces through bites, scratches or simple handling can result in infection. Clinically these are very similar, however in Haverhill fever, vomiting and other gastrointestinal symptoms are a much more prevalent feature.2 A history of exposure to rats is often missed unless specifically elicited, further delaying diagnosis. Mortality rate ranges from 7-13%, usually due to complications such as endovascular infection, pneumonitis and overwhelming sepsis. However, institution of appropriate therapy with penicillin leads to rapid cure. Cephalosporins, carbapenems, lincosamides and tetracyclines are also effective. 3

Special thanks to Dr Michael Thomas at RBWH Microbiology laboratory for gram stain photos, and Sharon at GCUH Microbiology laboratory

REFERENCES 1. Washburn RG. Rat-Bite Fever: Streptobacillus moniliformis and Spirillim minus. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice if Infectious Diseases. New York: Churchill Livingstone, 2010: 2965-2968 2. Elliott SP. Rat bite fever and Streptobacillus moniliformis. Clin Microbiol Rev 2007; 20: 13-22 3. Edwards R, Finch RG. Characterisation and antibiotic susceptibilities of Streptobacillus moniliformis. Journal of Med Microbiol. – Vol. 21 (1986), 39-42