title: Effect of combination therapy of rifampicin and azithromycin on TNF levels during a rat model of chronic osteomyelitis.
abstract: The purpose of the present study was to evaluate the combination of azithromycin and rifampicin on experimental chronic osteomyelitis due to Staphylococcus aureus. Alterations in bone bacterial titre, activity of tumour necrosis factor (TNF), a cytokine implicated in inflammation-induced bone pathology, and histopathological changes during infection and following antibiotic treatment were evaluated. Rats were infected with S. aureus by direct tibial inoculation and then randomized 56 days after infection to receive saline treatment or a combination of azithromycin and rifampicin (50 mg/kg po and 25 mg/kg sc respectively) once daily for 21 days. The combination of azithromycin and rifampicin was successful as determined by dramatic reduction in bone bacterial counts (approximately log 4 cfu), but regrowth of the organisms occurred suggesting that the duration of treatment was insufficient. TNF alpha mRNA and TNF activity were constantly elevated by approximately 20- and >200-fold, respectively, and remained elevated irrespective of antimicrobial treatment. Bone histology revealed extensive increase in bone turnover in both the infected and antibiotic treated bones with no difference being observed between the groups. This suggests that, in infected bone, the elevated TNF levels observed may be directly related to the bone pathology and both remain largely unchanged despite potent antibiotic therapy.
authors.affiliation: Pharma Research, Ciba-Geigy AG, Basle, Switzerland.
authors.forename: A J
authors.initials: AJ
authors.lastname: Littlewood-Evans
authors.forename: M
authors.initials: M
authors.lastname: Hattenberger
authors.forename: O
authors.initials: O
authors.lastname: Zak
authors.forename: T
authors.initials: T
authors.lastname: O'Reilly
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use; D000904:Antibiotics, Antitubercular / Q000494:pharmacology / Q000627:therapeutic use; D017963:Azithromycin / Q000494:pharmacology* / Q000627:therapeutic use; D001842:Bone and Bones / Q000187:drug effects / Q000382:microbiology / Q000473:pathology; D002908:Chronic Disease; D004195:Disease Models, Animal; D004359:Drug Therapy, Combination / Q000494:pharmacology* / Q000627:therapeutic use; D010019:Osteomyelitis / Q000188:drug therapy* / Q000382:microbiology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D012293:Rifampin / Q000494:pharmacology* / Q000627:therapeutic use; D013211:Staphylococcus aureus / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D000904:Antibiotics, Antitubercular; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D017963:Azithromycin; D012293:Rifampin