The incubation period for the bacteria generally lasts from three-ten days. As the disease progresses. almost half the patients experience migratory polyarthralgias. Mechanism
Although the specific form of pathogenesis is still a subject of ongoing research, the bacteria has been observed to result in morphological symptoms that are atypical of bacterial infection. Autopsy of the victims vividly exhibit erythrophagocytosis, hepatosplenomegaly, interstitial pneumonia, and lymph node sinus hyperplasia. In addition, Myocarditis and Endocarditis have also been demonstrated in such patients. Synovial and serosal surfaces may be more suited for the growth of the bacteria within the body. Furthermore, leukocytoclastic vasculitis has been observed in the skin lesions. Diagnosis
The microaerophilic conditions needed for the bacteria to grow, makes its detection incredibly difficult. Trypticase soy agar or broth enriched with 20% blood, serum, or ascitic fluid is necessary for the optimal growth of the bacteria under laboratory conditions. The organism may take up to seven days to grow and the colonies generally have a circular, grayish and shiny appearance on agar. Once the microbe has grown, primary identification can be carried out via biochemical and carbohydrate fermentation analysis. Biochemical tests such as oxidase, catalase, indole, and nitrate can be used to detect the bacteria. However, S. moniliformis can be biochemically differentiated from similar bacteria by their negative production of indole, catalase, and oxidase, while reduction of nitrate to nitrite. PCR assay specific for Streptobacillus moniliformis can also be used to detect the bacteria in a patient sample with high accuracy.
The PCR assay utilizes primers based on the 16S rRNA gene base sequences of human and rodent strains of S. moniliformis (forward primer, 5′ GCT TAA CAC ATG CAA ATC TAT 3′ and reverse primer, 5′ AGT AAG GGC CGT ATC TCA 3′). These primers exhibit 100% complementarity to S. moniliformis ATCC 14674T and S. moniliformis ANL 370-1. The PCR assay generates a 296-bp product which upon treatment with BfaI restriction enzyme, leads to the generation of three distinct fragments (128, 92, and 76 bp), which are specific to S. moniliformis. Hence, this assay can be used to detect S. moniliformis with great accuracy. Prevention
Although rare, the disease is certainly seeing a spike in the number of incidences because of various reasons. The most important among them is the fact that rodents are increasingly finding their way into our homes either as a pet or as a pest. In fact, the number of children who are affected by rat bite fever has been specifically on the rise. Therefore, wild rats should not be brought home and if there is an infestation, appropriate measures for extermination must be undertaken to prevent the disease from spreading. Treatment
The bacteria are susceptible to a number of antibiotics. They are: cephalosporins, carbapenems, aztreonam, clindamycin, erythromycin, nitrofurantoin, bacitracin, doxycycline, tetracycline, teicoplanin, and vancomycin. However, the data suggests that treatment with erythromycin can be less efficient. Intravenous penicillin G (400000–600000 IU/day) should be administered for 7 days and then a dosage of oral penicillin must be prescribed.