Despite extensive research, the pathogenesis of neonatal necrotizing enterocolitis (NEC) remains elusive. The aim of our work was to investigate the role of bacterial strains involved in NEC in gnotobiotic quails as experimental model. Six groups of germ-free quails that were fed a lactose diet were associated with Klebsiella pneumoniae, Clostridium perfringens, C. difficile, C. paraputrificum, or C. butyricum (two strains). Implantation level, incidence of cecal lesions, production of short-chain fatty acids, and histologic lesions of the cecal wall were investigated. Whatever the strain, the implantation level was high (10(9) UFC/g). Neither K. pneumoniae nor C. difficile induced any cecal lesions. In contrast, the four other clostridial strains led to cecal NEC-like lesions with a variable occurrence: four of 12 quails for C. perfringens, eight of 12 quails for C. paraputrificum, and the same highest value, nine of 12 quails and eight of 10 quails for both C. butyricum strains. Gross aspects of the lesions may be linked to the short-chain fatty acid profiles and/or concentrations: thickening of the cecal wall (C. butyricum and C. perfringens) with high proportion of butyric acid, hemorrhages (C. paraputrificum) with high proportion of iso-butyric acid, and presence of other iso-acids. In addition, C. butyricum was characterized by pneumatosis, linked to a high gas production. Microscopic aspects confirmed the presence of edemas and intramucosa hemorrhages. Clostridia species, whose role is controversial, seem to be strongly implicated in NEC through excessive production of butyric acid as a result of colonic lactose fermentation. These results call for anaerobe detection in feces of infants who have NEC.