In vitro evaluation of intracellular activity of antibiotics against non-typhoid Salmonella

Non-typhoid salmonellae are the most common causative organisms of bacteria l enteritis in children. Clinical studies have failed to show any influence of various antibiotics on the natural course of acute salmonella enteritis . Poor penetration of antibiotics into phagocytic cells that contain intrac ellular Salmonella spp., and possible intracellular antibiotic inactivation have been considered as possible reasons for this. In this study, we used an in vitro model to assess the intracellular activity of antibiotics again st non-typhoid salmonellae. The survival of intracellular Salmonella spp. i n P388D1 cells, a mouse macrophage cell line was measured in the presence o f various antibiotics. Except for gentamicin, which entered phagocytes poor ly, ofloxacin, azithromycin, chloramphenicol and three beta-lactam antibiot ics, ampicillin, cefixime and ceftriaxone, exhibited bacteriostatic activit y against susceptible intracellular Salmonella spp. at an extracellular con centration equal to the minimal inhibitory concentration (MIC). At a concen tration of 10 x MIC, neither chloramphenicol nor the three beta-lactam anti biotics produced a bactericidal response; however, both ofloxacin and azith romycin were bactericidal after 8-24 h of incubation. The results showed th at fluoroquinolones and new macrolides were more efficient than the other a ntibiotics in eradicating intracellular salmonella and might be useful agen ts for the treatment of non-typhoid salmonella enteritis in children. Clini cal trials should be considered. (C) 1999 Elsevier Science B.V. and Interna tional Society of Chemotherapy. All rights reserved.