Chloramphenicol and tetracycline decrease motility and increase invasion and attachment gene expression in specific isolates of multidrug-resistant Salmonella enterica serovar Typhimurium
Chloramphenicol and tetracycline decrease motility and increase invasion and attachment gene expression in specific isolates of multidrug-resistant Salmonella enterica serovar Typhimurium
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DOI：
10.3389/fmicb.2014.00801
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发表时间：
2015-01-30
影响因子：
5.2
通讯作者：
Bearson, Shawn M. D.
中科院分区：
文献类型：
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作者：
Brunelle, Brian W.;Bearson, Bradley L.;Bearson, Shawn M. D.
抗生素用于人类和动物的疾病治疗或预防作用，以及用于提高牲畜的饲料转化效率。抗生素还可在微生物种群中引起不良影响，包括选择抗生素抗性、增强病原体入侵和刺激水平基因转移。卡巴多斯是一种兽用抗生素，在美国用于猪生产的初始阶段，用于提高饲料效率和控制猪痢疾和细菌性猪肠炎。卡巴氨已在体外显示出在产滋贺毒素的大肠杆菌（STEC）中诱导噬菌体编码的滋贺毒素，以及在猪短螺旋体中诱导转移抗生素抗性基因的噬菌体样元件，但卡巴氨对其他细菌中的原噬菌体的影响尚不清楚。本研究检测了暴露于碳水化合物对鼠伤寒沙门氏菌原噬菌体诱导和遗传转移的影响，鼠伤寒沙门氏菌是一种人类食源性病原体，经常在猪体内定植而不引起疾病。S.鼠伤寒LT 2暴露于卡巴肼诱导的原噬菌体产生，导致细菌细胞裂解和释放电子显微镜可见的病毒体。通过监测Fels-1前噬菌体中sodCIII：：neo盒从LT 2到受体沙门氏菌菌株的转导，证实了卡巴多诱导噬菌体介导的基因转移。此外，碳酰亚胺经常在多药耐药噬菌体类型DT 104和DT 120分离株中诱导全身性转导，导致包括抗生素耐药基因的染色体和质粒DNA的转移。我们的研究表明，沙门氏菌暴露于卡巴氨诱导的前噬菌体，可以转移毒力和抗生素抗性基因的敏感细菌宿主。在动物生产过程中，卡巴氧诱导的噬菌体介导的基因转移可以作为细菌进化的一个促成因素，而噬菌体是环境中细菌适应性基因的储存库。鼠伤寒沙门氏菌是从人类和牲畜中分离的最常见的血清型之一，超过35%的这些分离株对三种或更多种抗生素具有耐药性。多重耐药（MDR）沙门氏菌是一个公共卫生问题，因为与抗生素敏感菌株相比，它与患者发病率增加有关，尽管目前尚不清楚抗生素耐药菌株如何导致更严重的感染。沙门氏菌的细胞侵入是受时间调控的，通常发生在对数晚期和稳定生长期间。然而，我们先前的工作确定，暴露于亚抑制浓度的四环素30分钟可以在某些MDR S的早期对数生长期间诱导完全侵袭表型。鼠伤寒分离株。目前的研究检查了其他抗生素的亚抑菌浓度是否也可以在同一组分离株中诱导侵袭性。氨苄青霉素和链霉素没有影响入侵，但一定浓度的氯霉素被发现诱导入侵的一个子集的分离株。氯霉素诱导的两个菌株也可被四环素诱导。RNA-seq分析表明，氯霉素和四环素都下调运动基因的表达，而上调与附着，侵袭和细胞内生存相关的基因。11个菌毛操纵子被上调，这是值得注意的，因为只有3个菌毛操纵子被认为是在培养物中可诱导的;这些上调的操纵子中有6个已被报道在小鼠中沙门氏菌的持久性中发挥作用。总的来说，这些数据表明，由于抗生素暴露，调节侵袭的遗传途径的正常进展可以在30分钟内加速发生。这种由于抗生素而改变的侵入过程可能在MDR沙门氏菌患者中观察到的感染强度和持续时间增加中发挥作用。
Antibiotics are used for disease therapeutic or preventative effects in humans and animals, as well as for enhanced feed conversion efficiency in livestock. Antibiotics can also cause undesirable effects in microbial populations, including selection for antibiotic resistance, enhanced pathogen invasion, and stimulation of horizontal gene transfer. Carbadox is a veterinary antibiotic used in the US during the starter phase of swine production for improved feed efficiency and control of swine dysentery and bacterial swine enteritis. Carbadox has been shown in vitro to induce phage-encoded Shiga toxin in Shiga toxin-producing Escherichia coli (STEC) and a phage-like element transferring antibiotic resistance genes in Brachyspira hyodysenteriae, but the effect of carbadox on prophages in other bacteria is unknown. This study examined carbadox exposure on prophage induction and genetic transfer in Salmonella enterica serovar Typhimurium, a human foodborne pathogen that frequently colonizes swine without causing disease. S. Typhimurium LT2 exposed to carbadox induced prophage production, resulting in bacterial cell lysis and release of virions that were visible by electron microscopy. Carbadox induction of phage-mediated gene transfer was confirmed by monitoring the transduction of a sodCIII::neo cassette in the Fels-1 prophage from LT2 to a recipient Salmonella strain. Furthermore, carbadox frequently induced generalized transducing phages in multidrug-resistant phage type DT104 and DT120 isolates, resulting in the transfer of chromosomal and plasmid DNA that included antibiotic resistance genes. Our research indicates that exposure of Salmonella to carbadox induces prophages that can transfer virulence and antibiotic resistance genes to susceptible bacterial hosts. Carbadox-induced, phage-mediated gene transfer could serve as a contributing factor in bacterial evolution during animal production, with prophages being a reservoir for bacterial fitness genes in the environment.Salmonella enterica serovar Typhimurium is one of the most common serovars isolated from humans and livestock, and over 35% of these isolates are resistant to three or more antibiotics. Multidrug-resistant (MDR) Salmonella is a public health concern as it is associated with increased morbidity in patients compared to antibiotic sensitive strains, though it is unknown how the antibiotic resistant isolates lead to a more severe infection. Cellular invasion is temporally regulated in Salmonella and normally occurs during late-log and stationary growth. However, our previous work determined that a 30 min exposure to a sub-inhibitory concentration of tetracycline can induce the full invasion phenotype during early-log growth in certain MDR S. Typhimurium isolates. The current study examined whether sub-inhibitory concentrations of other antibiotics could also induce the invasiveness in the same set of isolates. Ampicillin and streptomycin had no effect on invasion, but certain concentrations of chloramphenicol were found to induce invasion in a subset of isolates. Two of the isolates induced by chloramphenicol were also inducible by tetracycline. RNA-seq analyses demonstrated that chloramphenicol and tetracycline both down-regulated motility gene expression, while up-regulating genes associated with attachment, invasion, and intracellular survival. Eleven fimbrial operons were up-regulated, which is notable as only three fimbrial operons were thought to be inducible in culture; six of these up-regulated operons have been reported to play a role in Salmonella persistence in mice. Overall, these data show that the normal progression of the genetic pathways that regulate invasion can be expedited to occur within 30 min due to antibiotic exposure. This altered invasion process due to antibiotics may play a role in the increased intensity and duration of infection observed in patients with MDR Salmonella.