A mutation in the sap operon attenuates survival of nontypeable Haemophilus influenzae in a chinchilla model of otitis media
A mutation in the sap operon attenuates survival of nontypeable Haemophilus influenzae in a chinchilla model of otitis media
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DOI：
10.1128/iai.73.1.599-608.2005
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发表时间：
2005-01-01
影响因子：
3.1
通讯作者：
Bakaletz, LO
中科院分区：
文献类型：
--
作者：
Mason, KM;Munson, RS;Bakaletz, LO
细菌已经进化出抵抗抗菌肽(AP)杀死的策略，抗菌肽是先天免疫的重要效应者。SAP(对抗菌肽敏感)操纵子对A-P介导的杀灭沙门氏菌具有抵抗力。我们最近发现，在非分型流感嗜血杆菌(NTHI)诱导的中耳炎的灰鼠模型中，SapA基因的表达在中耳上调。基于这些发现，我们构建了一个含有由SAPA启动子驱动的Lux报告质粒的NTHI菌株，并证明了感染后SAP操纵子在栗鼠上呼吸道部位的早期但短暂的表达。我们推测，汁液操纵子产物介导了NTHI对AP的抗性。为了验证这一假说，我们构建了临床低传代菌株NTHI株86-028NP的SapA基因的非极性突变。SapA突变体对重组龙猫β-防御素1的杀伤敏感性大约是亲本菌株的8倍。然后我们评估了该突变体在龙猫体内定植和引起中耳炎的能力。与亲本菌株相比，SapA突变体在龙猫的鼻咽和中耳中存活的能力明显减弱。此外，在感染的双菌株挑战模型中，突变株与亲本株竞争的能力受到了损害。我们的结果表明，汁液操纵子的产物对于抵抗AP的活性是重要的，并可能在一定程度上调节正常运输与NTHI引起的疾病之间的平衡。
Bacteria have evolved strategies to resist killing by antimicrobial peptides (APs), important effectors of innate immunity. The sap (sensitivity to antimicrobial peptides) operon confers resistance to A-P-mediated killing of Salmonella. We have recently shown that sapA gene expression is upregulated in the middle ear in a chinchilla model of nontypeable Haemophilus influenzae (NTHI)-induced otitis media. Based on these findings, we constructed an NTHI strain containing a Lux reporter plasmid driven by the sapA promoter and demonstrated early yet transient expression of the sap operon within sites of the chinchilla upper airway upon infection. We hypothesized that the sap operon products mediate NTHI resistance to APs. In order to test this hypothesis, we constructed a nonpolar mutation in the sapA gene of NTHI strain 86-028NP, a low-passage-number clinical isolate. The sapA mutant was approximately eightfold more sensitive than the parent strain to killing by recombinant chinchilla beta-defensin 1. We then assessed the ability of this mutant to both colonize and cause otitis media in chinchillas. The sapA mutant was significantly attenuated compared to the parent strain in its ability to survive in both the nasopharynx and the middle ear of the chinchilla. In addition, the mutant was impaired in its ability to compete with the parent strain in a dual-strain challenge model of infection. Our results indicate that the products of the sap operon are important for resisting the activity of APs and may regulate, in part, the balance between normal carriage and disease caused by NTHI.