Haematogenous models of septic arthritis have some inherent disadvantages, such as the manifestation of arthritis relies on chance, the size of the inoculum is unknown and the number of animals to be studied cannot be reduced because the animals cannot serve as their own controls. This study aimed to develop a rat model of knee septic arthritis by injecting a known inoculum of Staphylococcus aureus into the joint. The left knees of 27 Sprague Dawley rats were injected with four different inoculum concentrations of a sensitive strain of S. aureus (30,000 colony-forming units (CFUs), n = 3; 18,550 CFUs, n = 6; 15,500 CFUs, n = 9; and 7700 CFUs, n = 9); the right knees served as controls. Clinical, microbiological and histological variables were assessed two and seven days later. The main criterion for diagnosing septic arthritis was a positive culture of synovial fluid. The rate of microbiologically confirmed septic arthritis was high for all inoculum concentrations (3/3, 6/6, 8/9 and 7/9, respectively), and the rate of bacteraemia was also high. Animal welfare was better for the two lowest inoculum concentrations. No animal reached the pre-established humane end points. Overall, the third inoculum was considered the most suitable. Thus, acute septic arthritis can be caused in rats by inoculating 15,000 CFUs of an ATCC strain of S. aureus directly into the knee joint. Overall, the model seems to be useful for studying the effectiveness of drugs for the treatment of acute septic arthritis.
BackgroundMembers of the genus Pseudonocardia have been widely reported and recovered from several ecosystems, such as soil samples and plant samples. Pseudonocardia bacteria colonize the microbial communities on the integument of fungus gardening ant species. We present the first documented case of Pseudonocardia carboxydivorans isolated in human cerebrospinal fluid (CSF). To the best of our knowledge, this is the first report of an human infection by P. carboxydivorans.
Case presentationA patient, who suffered a traumatic brain injury a month before, was admitted to this hospital due to gait alteration and cognitive disturbances. Culture of cerebrospinal fluid showed ramified, not acid-fast, Gram positive bacilli. The bacterium was identified by molecular methods as P. carboxydivorans.ConclusionThis is the first documented case of isolating P. carboxydivorans in human CSF in a case of probable meningitis. Further research is needed in order to determine its pathogenic role in human infections.
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