Liao Chun-Hsing, Chen Wei-Chien, Li Li-Hua, Lin Yi-Tsung, Pan Sz-Yun, Yang Tsuey-Ching
Division of Infectious Disease, Far Eastern Memorial Hospital, New Taipei City, Taiwan.
Department of Medicine, Yang-Ming University, Taipei, Taiwan.
J Antimicrob Chemother. 2020 Dec 1;75(12):3544-3551. doi: 10.1093/jac/dkaa358.
Iron is an essential nutrient for almost all aerobic organisms, including Stenotrophomonas maltophilia. Fur is the only known transcriptional regulator presumptively involved in iron homeostasis in S. maltophilia. AmpR, a LysR-type transcriptional regulator, is known to regulate β-lactamase expression and β-lactam resistance in S. maltophilia.
To identify the novel regulator involved in controlling the viability of S. maltophilia in an iron-depleted condition and to elucidate the underlying regulatory mechanisms.
The potential regulator involved in iron homeostasis was identified by studying the cell viabilities of different regulator mutants in 2,2'-dipyridyl (DIP)-containing medium. Iron-chelating activity was investigated using the chrome azurol S (CAS) activity assay. An iron source utilization bioassay was carried out to examine utilization of different iron sources. Gene expression was determined by quantitative real-time PCR, and the Etest method was used to evaluate antibiotic susceptibility.
Of the 14 tested mutants, the ampR mutant, KJΔAmpR, showed a growth compromise in DIP-containing medium. AmpR regulated stenobactin synthesis in an iron-depleted condition, but showed little involvement in the uptake and utilization of ferri-stenobactin and ferric citrate. AmpR was up-regulated by iron limitation and β-lactam challenge. S. maltophilia clinical isolates grown under conditions of iron depletion were generally more resistant to β-lactams compared with conditions of iron repletion.
AmpR is a dual transcriptional regulator in S. maltophilia, which regulates the β-lactam-induced β-lactamase expression and iron depletion-mediated stenobactin synthesis. AmpR is, therefore, a promising target for the development of inhibitors.
铁是包括嗜麦芽窄食单胞菌在内的几乎所有需氧生物所必需的营养素。Fur是推测参与嗜麦芽窄食单胞菌铁稳态的唯一已知转录调节因子。AmpR是一种LysR型转录调节因子，已知可调节嗜麦芽窄食单胞菌中的β-内酰胺酶表达和β-内酰胺抗性。
鉴定参与控制嗜麦芽窄食单胞菌在缺铁条件下生存能力的新型调节因子，并阐明其潜在的调节机制。
通过研究不同调节因子突变体在含2,2'-联吡啶（DIP）培养基中的细胞活力，鉴定参与铁稳态的潜在调节因子。使用铬天青S（CAS）活性测定法研究铁螯合活性。进行铁源利用生物测定以检测不同铁源的利用情况。通过定量实时PCR测定基因表达，并使用Etest方法评估抗生素敏感性。
在14个测试突变体中，ampR突变体KJΔAmpR在含DIP的培养基中生长受损。AmpR在缺铁条件下调节嗜铁素合成，但在铁嗜铁素和柠檬酸铁的摄取和利用中作用很小。AmpR受铁限制和β-内酰胺攻击上调。与铁充足条件相比，在缺铁条件下生长的嗜麦芽窄食单胞菌临床分离株通常对β-内酰胺更具抗性。
AmpR是嗜麦芽窄食单胞菌中的双重转录调节因子，可调节β-内酰胺诱导的β-内酰胺酶表达和铁耗竭介导的嗜铁素合成。因此，AmpR是开发抑制剂的有希望的靶点。
