Department of Bacteriology, Host-Pathogen Interaction and Diagnostics Development, Wageningen Bioveterinary Research, Lelystad, the Netherlands.
Department of Diagnostics and Crisis Organisation, Wageningen Bioveterinary Research, Lelystad, the Netherlands.
Vet Microbiol. 2021 Aug;259:109166. doi: 10.1016/j.vetmic.2021.109166. Epub 2021 Jun 25.
Chlamydia gallinacea is a recently discovered and widespread obligate intracellular bacterium in chickens. In chickens, infections appear to be asymptomatic, but can result in reduced weight gain in broilers. Molecular typing revealed C. gallinacea is genetically diverse which might lead to differences in pathogenic potential between strains. However, studies about the pathogenesis of different C. gallinacea strains are still limited. In this study, the pathogenesis of C. gallinacea strain NL_G47 was investigated in three consecutive animal experiments. The first experiment served as a pilot in which a maximum culturable dose was administered orally to 13 chickens. Excretion of chlamydial DNA in cloacal swabs was measured during 11 days post infection, but no clinical signs were observed. The second and third experiment were a repetition of the first experiment, but now chickens were sacrificed at consecutive time points to investigate tissue dissemination of C. gallinacea. Again excretion of chlamydial DNA in cloacal swabs was detected and no clinical signs were observed in line with the results of the first experiment. PCR and immunohistochemistry of tissue samples revealed C. gallinacea infected the epithelium of the jejunum, ileum and caecum. Furthermore, C. gallinacea could be detected in macrophages in the lamina propria and in follicular dendritic cells (FDCs) of the B cell follicles in the caecal tonsil. Results of serology showed a systemic antibody response from day seven or eight and onward in all three experiments. The experiments with strain NL_G47 confirmed observations from field studies that C. gallinacea infection does not result in acute clinical disease and mainly resides in the epithelium of the gut. Whether the presence of C. gallinacea results in chronic persistent infections with long term and less obvious health effects in line with observations on other infections caused by Chlamydiae, needs further investigation.
鸡鹦鹉热衣原体是一种最近发现的、广泛存在于鸡体内的专性细胞内细菌。在鸡中，感染似乎无症状，但可导致肉鸡体重减轻。分子分型表明，鹦鹉热衣原体具有遗传多样性，这可能导致不同菌株的致病潜力存在差异。然而，关于不同鹦鹉热衣原体菌株的发病机制的研究仍然有限。在这项研究中，连续进行了三项动物实验来研究鹦鹉热衣原体 NL_G47 株的发病机制。第一项实验作为一项试验，给 13 只鸡口服了最大可培养剂量的细菌。在感染后 11 天内，通过直肠拭子测量了衣原体 DNA 的排出量，但未观察到临床症状。第二项和第三项实验是第一项实验的重复，但现在鸡在连续的时间点被处死，以研究鹦鹉热衣原体在组织中的传播。同样，在直肠拭子中检测到了衣原体 DNA 的排出，并且与第一项实验的结果一致，未观察到临床症状。组织样本的 PCR 和免疫组织化学分析显示，鹦鹉热衣原体感染了空肠、回肠和盲肠的上皮细胞。此外，在固有层的巨噬细胞和盲肠扁桃体的 B 细胞滤泡中的滤泡树突状细胞（FDC）中也可以检测到鹦鹉热衣原体。血清学结果表明，在所有三项实验中，从第 7 天或第 8 天开始，均出现了全身性抗体反应。NL_G47 株的实验证实了田间研究的观察结果，即鹦鹉热衣原体感染不会导致急性临床疾病，主要存在于肠道的上皮细胞中。鹦鹉热衣原体的存在是否会导致与其他衣原体引起的感染相一致的慢性持续性感染，并伴有长期且不太明显的健康影响，需要进一步研究。
