Salmonella enterica serovar Typhi, the etiological agent of typhoid fever, causes a systemic life-threatening disease. To carry out a successful infection process, this bacterium needs to survive alkaline and acid pH conditions presented in the mouth, stomach, small intestine, and gallbladder. Therefore, in this work, a genetic screening to identify S. Typhi genes involved in acid and circumneutral pH resistance was performed. A collection of S. Typhi mutants deleted of fragments ranging from 6 to 80 kb were obtained by the Datsenko and Wanner method. Bacterial growth rate assays of each mutant were performed to identify S. Typhi genes involved in circumneutral and acid pH resistance. S. Typhi mutants deficient to growth at specific pH were evaluated in their capacity to invade and replicate in phagocytic cells. In this work, it is reported that S. Typhi ∆F4 (pH 4.5), S. Typhi ∆F44 (pH 4.5, 5.5, and 6.5), and S. Typhi ∆F73 (pH 4.5, 5.5, 6.5, and 7.5) were deficient to grow in the pH indicated. These three mutant strains were also affected in their ability to invade and replicate in human macrophages. S. Typhi contains defined genomic regions that influence the survival at specific pH values, as well as the invasion and replication inside human cells. Thus, this genetic information probably allows the bacteria to survive in different human compartments for an efficient infection cycle.

中文翻译：

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沙门氏菌血清型鼠伤寒基因组区域参与低pH抵抗力和人类巨噬细胞的侵袭和复制

伤寒的病原体肠炎沙门氏菌引起全身性威胁生命的疾病。为了成功完成感染过程，该细菌需要在口腔，胃，小肠和胆囊中存在的碱性和酸性pH条件下生存。因此，在这项工作中，进行了遗传筛选以鉴定参与酸性和环境pH耐受性的鼠伤寒沙门氏菌基因。通过Datsenko和Wanner方法获得了缺失了6至80kb片段的鼠伤寒沙门氏菌突变体的集合。进行每个突变体的细菌生长速率测定以鉴定参与环境中性和酸性pH抗性的鼠伤寒沙门氏菌基因。对在特定pH下缺乏生长的鼠伤寒沙门氏菌突变体在吞噬细胞中侵袭和复制的能力进行了评估。在这项工作中，据报道，S。Typhi ∆F4（pH 4.5），S。Typhi ∆F44（pH 4.5、5.5和6.5）和S. Typhi ∆F73（pH 4.5、5.5、6.5和7.5）在所示pH值下不足。这三种突变株在人巨噬细胞中侵袭和复制的能力也受到影响。伤寒沙门氏菌包含确定的基因组区域，这些区域会影响特定pH值下的存活以及人类细胞内部的侵袭和复制。因此，这种遗传信息可能使细菌能够在不同的人类隔室中生存，从而实现有效的感染周期。伤寒含有确定的基因组区域，这些区域会影响特定pH值下的存活以及人类细胞内的侵袭和复制。因此，这种遗传信息可能使细菌能够在不同的人类隔室中生存，从而实现有效的感染周期。伤寒含有确定的基因组区域，这些区域会影响特定pH值下的存活以及人类细胞内的侵袭和复制。因此，这种遗传信息可能使细菌能够在不同的人类隔室中生存，从而实现有效的感染周期。