De Koning-Ward T F, Robins-Browne R M
Department of Microbiology and Infectious Diseases, Royal Children's Hospital, Parkville, Victoria, Australia.
Infect Immun. 1995 Oct;63(10):3790-5. doi: 10.1128/iai.63.10.3790-3795.1995.
The stomach serves as a barrier to enteric infection because of the antibacterial effect of the hydrochloric acid in gastric juice. In this study, we tested the ability of the enteric pathogen Yersinia enterocolitica to tolerate a pH range of 2.0 to 6.0 and found that under the conditions of a normal human fasting stomach (pH < 3 and a gastric emptying time of 2 h), Y. enterocolitica is highly acid resistant, showing approximately 85% survival. The resistance of Y. enterocolitica to acid in vitro depended on the bacterial growth phase and the concentration of urea in the medium, being maximal during stationary phase in the presence of at least 0.3 mM urea. Urease-negative mutants of Y. enterocolitica were constructed by disrupting the urease gene complex of a virulent strain of serogroup O9. Compared with the wild type, these mutants showed an approximately 1,000-fold decrease in the ability to tolerate acid in vitro (< 0.08% survival) and a 10-fold reduction in viability after passage through the stomachs of mice. Complementation of the disrupted urease genes in trans restored the ability of urease-negative mutants to tolerate low pH in vitro and gastric acidity to approximately wild-type levels. These findings indicate that urease is responsible for acid resistance in Y. enterocolitica and suggest that urease contributes to the virulence of Y. enterocolitica by enhancing the likelihood of bacterial survival during passage through the stomach.
由于胃液中盐酸的抗菌作用，胃成为肠道感染的一道屏障。在本研究中，我们测试了肠道病原体小肠结肠炎耶尔森菌在pH值2.0至6.0范围内的耐受能力，发现正常人体空腹胃的条件下（pH < 3且胃排空时间为2小时），小肠结肠炎耶尔森菌具有高度耐酸性，存活率约为85%。小肠结肠炎耶尔森菌在体外对酸的抗性取决于细菌生长阶段和培养基中尿素的浓度，在稳定期且存在至少0.3 mM尿素时抗性最大。通过破坏O9血清群强毒株的脲酶基因复合体构建了小肠结肠炎耶尔森菌脲酶阴性突变体。与野生型相比，这些突变体在体外耐受酸的能力下降了约1000倍（存活率< 0.08%），经小鼠胃后活力降低了10倍。通过反式互补破坏的脲酶基因可恢复脲酶阴性突变体在体外耐受低pH值的能力以及在胃酸性环境中的存活率至接近野生型水平。这些发现表明脲酶是小肠结肠炎耶尔森菌耐酸性的原因，并提示脲酶通过提高细菌在通过胃部过程中的存活可能性而有助于小肠结肠炎耶尔森菌的致病性。
