BACKGROUND & AIMS: :Twenty-two non-repetitive carbapenem-resistant Acinetobacter baumannii isolates were obtained from Intensive Care Unit patients. All of the isolates carried bla(OXA-23), bla(OXA-66), a novel cephalosporinase-encoding gene (bla(ADC-25)) and a class 1 integron with an aacC1-orfP-orfQ-aadA1a cassette array and had identical enterobacterial repetitive intergenic consensus (ERIC) profiles. ISAba1 was found upstream of bla(OXA-23), but was not associated with bla(OXA-66) or bla(ADC-25).

背景与目标： : 从重症监护病房患者中获得了22株非重复的耐碳青霉烯类鲍曼不动杆菌分离株。所有分离株均携带bla(OXA-23)，bla(OXA-66)，新型头孢菌素酶编码基因 (bla(ADC-25)) 和具有aacC1-orfP-orfQ-aadA1a盒阵列的1类整合子，并具有相同的肠细菌重复基因间共识 (ERIC) 谱。ISAba1位于bla(OXA-23) 的上游，但与bla(OXA-66) 或bla(ADC-25) 无关。

BACKGROUND & AIMS: OBJECTIVE:The aim of this study was to identify the clinical presentations and the current antimicrobial susceptibility of Acinetobacter baumannii. RESULTS:We identified 754 strains especially from intensive care units (50.53%) between January 2003 and December 2005. Bronchial swabs and blood culture were prevalent. High-level resistance to betalactamines was noted: 91% to cefotaxime, 50.3% to ceftazidime, and 42.6% to imipenem. Aminoside resistance varied from 17.9% for netilmicine to 72.1% for gentamycin. The resistance rate to ciprofloxacine was 65.8%, and to trimethoprime-sulfamethoxazole 75.8%. In intensive care units, the antimicrobial resistance rate of A. baumannii was higher (p<0.05). CONCLUSION:The resistance of A. baumannii to current antibiotics is alarming especially in intensive care units. An effective strategy against nosocomial infection is still necessary.

背景与目标：

BACKGROUND & AIMS: :The stress protectant trehalose is synthesized in Acinetobacter baumannii from UPD-glucose and glucose-6-phosphase via the OtsA/OtsB pathway. Previous studies proved that deletion of otsB led to a decreased virulence, the inability to grow at 45°C and a slight reduction of growth at high salinities indicating that trehalose is the cause of these phenotypes. We have questioned this conclusion by producing ∆otsA and ∆otsBA mutants and studying their phenotypes. Only deletion of otsB, but not deletion of otsA or otsBA, led to growth impairments at high salt and high temperature. The intracellular concentrations of trehalose and trehalose-6-phosphate were measured by NMR or enzymatic assay. Interestingly, none of the mutants accumulated trehalose any more but the ∆otsB mutant with its defect in trehalose-6-phosphate phosphatase activity accumulated trehalose-6-phosphate. Moreover, expression of otsA in a ∆otsB background under conditions where trehalose synthesis is not induced led to growth inhibition and the accumulation of trehalose-6-phosphate. Our results demonstrate that trehalose-6-phosphate affects multiple physiological activities in A. baumannii ATCC 19606.

背景与目标： : 压力保护剂海藻糖由UPD-葡萄糖和glucose-6-phosphase通过OtsA/OtsB途径在鲍曼不动杆菌中合成。先前的研究证明，otsB的缺失导致毒力降低，在45 °C下无法生长以及在高盐度下的生长略有降低，这表明海藻糖是这些表型的原因。我们通过产生 ∆ otsa和 ∆ otsba突变体并研究其表型来质疑这一结论。仅删除otsB，而不删除otsA或otsBA，在高盐和高温下导致生长受损。通过NMR或酶法测定海藻糖和trehalose-6-phosphate的细胞内浓度。有趣的是，除了trehalose-6-phosphate磷酸酶活性缺陷的 ∆ otsb突变体外，没有一个突变体再积累海藻糖trehalose-6-phosphate。此外，在不诱导海藻糖合成的条件下，otsA在 ∆ otsb背景中的表达导致生长抑制和trehalose-6-phosphate积累。我们的结果表明，trehalose-6-phosphate影响鲍曼不动杆菌ATCC 19606的多种生理活动。

BACKGROUND & AIMS: BACKGROUND:The worldwide emergence and clonal spread of carbapenem-resistant Acinetobacter baumannii (CRAB) is of great concern. The aim of this nationwide study was to investigate the prevalence of CRAB isolates in Serbia and to characterize underlying resistance mechanisms and their genetic relatedness. METHODS:Non-redundant clinical samples obtained from hospitalized patients throughout Serbia were included in the prospective, observational, multicenter study conducted from January to June 2018. Samples were initially screened for the presence of Acinetobacter baumannii-calcoaceticus (Acb) complex using conventional bacteriological techniques. Acb complexes recovered from clinical samples obtained from inpatients with confirmed bacterial infections were further evaluated for the presence of A. baumannii. Identification to the species level was done by the detection of the blaOXA-51 gene and rpoB gene sequence analysis. Susceptibility testing was done by disk diffusion and broth microdilution method. CRAB isolates were tested for the presence of acquired carbapenemases (blaOXA-24-like, blaOXA-23-like,blaOXA-58-like, blaOXA-143-like, blaIMP, blaVIM, blaGIM, blaSPM, blaSIM, blaNDM) by PCR. Clonal relatedness was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). RESULTS:Acb complex was isolated in 280 out of 2401 clinical samples (11.6%). Overall, A. baumannii was identified in 237 out of 280 Acb complex (84.6%). CRAB prevalence was found to be 93.7% (237/222). The MIC50/MIC90 for imipenem and meropenem were 8/> 32 μg/mL and 16/> 32 μg/mL, respectively. Although susceptibility was high for colistin (95.7%; n = 227) and tigecycline (75.1%; n = 178), ten isolates (4.3%) were classified as pandrug-resistant. The following carbapenemases-encoding genes were found: 98 (44.2%) blaOXA-24-like, 76 (34.5%) blaOXA-23-like, and 7 (3.2%) blaNDM-1. PFGE analysis revealed six different clusters. MLST analysis identified three STs: ST2 (n = 13), ST492 (n = 14), and ST636 (n = 10). Obtained results evaluated that circulating CRAB clones in Serbia were as follows: blaOXA66/blaOXA23/ST2 (32.4%), blaOXA66/blaOXA23/blaOXA72/ST2 (2.7%), blaOXA66/blaOXA72/ST492 (37.8%), and blaOXA66/blaOXA72/ST636 (27.1%). CONCLUSION:This study revealed extremely high proportions of carbapenem resistance among A. baumannii clinical isolates due to the emergence of blaOXA-72, blaOXA-23, and blaNDM-1 genes among CRAB isolates in Serbia and their clonal propagation.

背景与目标：

BACKGROUND & AIMS: :A 5-kbp region upstream of the are-ben-cat genes was cloned from Acinetobacter sp. strain ADP1, extending the supraoperonic cluster of catabolic genes to 30 kbp. Four open reading frames, salA, salR, salE, and salD, were identified from the nucleotide sequence. Reverse transcription-PCR studies suggested that these open reading frames are organized into two convergent transcription units, salAR and salDE. The salE gene, encoding a protein of 239 residues, was ligated into expression vector pET5a. Its product, SalE, was shown to have esterase activity against short-chain alkyl esters of 4-nitrophenol but was also able to hydrolyze ethyl salicylate to ethanol and salicylic acid. A mutant of ADP1 with a Km(r) cassette introduced into salE had lost the ability to utilize only ethyl and methyl salicylates of the esters tested as sole carbon sources, and no esterase activity against ethyl salicylate could be detected in cell extracts. SalE was induced during growth on ethyl salicylate but not during growth on salicylate itself. salD encoded a protein of undetermined function with homologies to the Escherichia coli FadL membrane protein, which is involved in facilitating fatty acid transport, and a number of other proteins detected during aromatic catabolism, which may also function in hydrocarbon transport or uptake processes. A Km(r) cassette insertion in salD deleteriously affected cell growth and viability. The salA and salR gene products closely resemble two Pseudomonas proteins, NahG and NahR, respectively encoding salicylate hydroxylase and the LysR family regulator of both salicylate and naphthalene catabolism. salA was cloned into pUC18 together with salR and salE, and its gene product showed salicylate-inducible hydroxylase activity against a range of substituted salicylates, with the same relative specific activities as found in wild-type ADP1 grown on salicylate. Mutations involving insertion of Km(r) cassettes into salA and salR eliminated expression of salicylate hydroxylase activity and the ability to grow on either salicylate or ethyl salicylate. Studies of mutants with disruptions of genes of the beta-ketoadipate pathway with or without an additional salE mutation confirmed that ethyl salicylate and salicylate were channeled into the beta-ketoadipate pathway at the level of catechol and thence dissimilated by the cat gene products. SalR appeared to regulate expression of salA but not salE.

背景与目标： : 从不动杆菌属中克隆了一个位于ar-ben-cat基因上游的5-kbp区域。菌株ADP1，将分解代谢基因簇的上周期扩展到30 kbp。从核苷酸序列中鉴定出四个开放阅读框，salA，salR，salE和salD。逆转录PCR研究表明，这些开放阅读框被组织成两个会聚的转录单位，salAR和salDE。将编码239残基蛋白的salE基因连接到表达载体pET5a中。它的产品SalE显示出对4-硝基苯酚的短链烷基酯具有酯酶活性，但也能够将水杨酸乙酯水解为乙醇和水杨酸。引入salE的带有Km(r) 盒的ADP1突变体失去了仅利用测试的酯的乙基和水杨酸甲酯作为唯一碳源的能力，并且在细胞提取物中未检测到对水杨酸乙酯的酯酶活性。在水杨酸乙酯的生长过程中会诱导销售，但在水杨酸乙酯本身的生长过程中不会诱导销售。salD编码一种功能未定的蛋白质，与大肠杆菌FadL膜蛋白具有同源性，该蛋白参与促进脂肪酸转运，以及在芳香族分解代谢过程中检测到的许多其他蛋白质，这些蛋白质也可能在碳氢化合物转运或吸收过程中起作用。在salD中插入Km(r) 盒会严重影响细胞的生长和活力。salA和salR基因产物与两个假单胞菌蛋白NahG和NahR非常相似，分别编码水杨酸盐羟化酶和水杨酸盐和萘分解代谢的LysR家族调节剂。salA与salR和salE一起被克隆到pUC18中，其基因产物对一系列取代的水杨酸盐显示出水杨酸盐诱导的羟化酶活性，其相对比活与在水杨酸盐上生长的野生型ADP1中发现的相对比活相同。涉及将Km(r) 盒插入salA和salR的突变消除了水杨酸羟化酶活性的表达以及在水杨酸酯或水杨酸乙酯上生长的能力。对具有或没有附加销售突变的 β-酮己二酸途径基因破坏的突变体的研究证实，水杨酸乙酯和水杨酸乙酯在邻苯二酚的水平下被引导进入 β-酮己二酸途径，然后被cat基因产物异化。SalR似乎可以调节salA的表达，但不能调节销售。

BACKGROUND & AIMS: A serious epidemic of Acinetobacter baumannii resistant to imipenem occurred in the surgical intensive care unit of the hospital Charles-Nicolle in Tunis during February 1994, causing two deaths among three patients. The Acinetobacter strains were isolated from various samples of the intensive care unit. The techniques used for typing were biotyping, antibiogram, plasmid profiles and chromosomal DNA by random amplified polymorphic DNA (RAPD). The A baumannii strains isolated from patients exhibited an identical pattern with all the epidemiological markers utilized; the strains from the surrounding areas showed four and six different patterns respectively for phenotypic and genotypic characters. The strain isolated from a care table had the same phenotypic and genotypic pattern as that of the patients' strains.

背景与目标： 1994年2月期间，突尼斯Charles-Nicolle医院的外科重症监护室发生了对亚胺培南耐药的鲍曼不动杆菌的严重流行，导致三名患者中有两人死亡。从重症监护病房的各种样品中分离出不动杆菌菌株。用于分型的技术是通过随机扩增多态性DNA (RAPD) 进行的生物分型，抗生素图，质粒谱和染色体DNA。从患者中分离出的鲍曼不动杆菌菌株表现出与所有使用的流行病学标记相同的模式; 来自周围地区的菌株分别表现出四种和六种不同的表型和基因型特征。从护理表中分离出的菌株具有与患者菌株相同的表型和基因型模式。

BACKGROUND & AIMS: OBJECTIVES:Tigecycline has shown in vitro activity against Acinetobacter baumannii. Yet, published clinical experience with tigecycline use outside clinical trials is lacking. We describe, for the first time, bloodstream infection caused by tigecycline-non-susceptible A. baumannii occurring in patients receiving tigecycline for other indications. The possible mechanisms of resistance and pharmacokinetic limitations of the drug are addressed. METHODS:The clinical records of involved patients were systematically reviewed. Tigecycline susceptibility testing was initially performed using the Etest method and confirmed by agar dilution. Involved isolates underwent PFGE and exposure to phenyl-arginine-beta-naphthylamide (PAbetaN), an efflux pump inhibitor. RESULTS:Two patients developed A. baumannii bloodstream infection while receiving tigecycline. Tigecycline was administered for other indications for 9 and 16 days, respectively, before the onset of A. baumannii infection. Patient 1 died of overwhelming A. baumannii infection and Patient 2 recovered after a change in antibiotic therapy. The MICs of tigecycline were 4 and 16 mg/L, respectively. Both isolates had a multidrug-resistant phenotype and were genotypically unrelated. After exposure to PAbetaN, the MICs reduced to 1 and 4 mg/L, respectively. CONCLUSIONS:To our knowledge, this is the first clinical description of bloodstream infection caused by tigecycline-non-susceptible A. baumannii. Such resistance appears to be at least partly attributable to an efflux pump mechanism. Given the reported low serum tigecycline levels, we urge caution when using this drug for treatment of A. baumannii bloodstream infection.

背景与目标：

BACKGROUND & AIMS: :The genus Acinetobacter encompasses a heterogeneous group of bacteria that are ubiquitous in the natural environment due in part to their ability to adapt genetically to novel challenges. Acinetobacter sp. strain ADP1 (also known as strain BD413) is naturally transformable and takes up DNA from any source. Donor DNA can be integrated into the chromosome by recombination provided it possesses sufficient levels of nucleotide sequence identity to the recipient's DNA. In other bacteria, the requirement for sequence identity during recombination is partly due to the actions of the mismatch repair system, a key component of which, MutS, recognizes mismatched bases in heteroduplex DNA and, along with MutL, blocks strand exchange. We have cloned mutS from strain ADP1 and examined its roles in preventing recombination between divergent DNA and in the repair of spontaneous replication errors. Inactivation of mutS resulted in 3- to 17-fold increases in transformation efficiencies with donor sequences that were 8 to 20% divergent relative to the strain ADP1. Strains lacking MutS exhibited increased spontaneous mutation frequencies, and reversion assays demonstrated that MutS preferentially recognized transition mismatches while having little effect on the repair of transversion mismatches. Inactivation of mutS also abolished the marker-specific variations in transforming efficiency seen in mutS(+) recipients where transition and frameshift alleles transformed at eightfold lower frequencies than transversions or large deletions. Comparison of the MutS homologs from five individual Acinetobacter strains with those of other gram-negative bacteria revealed that a number of unique indels are conserved among the Acinetobacter amino acid sequences.

背景与目标： : 不动杆菌属包括一群在自然环境中普遍存在的异质细菌，部分原因是它们能够在基因上适应新的挑战。不动杆菌属。ADP1菌株 (也称为BD413菌株) 是天然可转化的，并从任何来源获取DNA。只要供体DNA与受体DNA具有足够水平的核苷酸序列同一性，就可以通过重组将其整合到染色体中。在其他细菌中，重组过程中对序列同一性的要求部分是由于错配修复系统的作用，该系统的关键组成部分MutS识别异双链DNA中的错配碱基，并与MutL一起阻止链交换。我们已经从ADP1菌株中克隆了mutS，并检查了其在防止发散DNA之间的重组以及修复自发复制错误中的作用。mutS的失活导致转化效率提高3至17倍，供体序列相对于菌株adp1发散8至20% 倍。缺乏MutS的菌株表现出增加的自发突变频率，并且逆转试验表明，MutS优先识别过渡失配，而对逆转失配的修复几乎没有影响。mutS的失活还消除了在mutS () 受体中看到的特定于标记的转换效率变化，其中转换和移码等位基因的转换频率比转换或大缺失低八倍。将五个单独的不动杆菌菌株的MutS同源物与其他革兰氏阴性细菌的MutS同源物进行比较，发现不动杆菌氨基酸序列中存在许多独特的indels。

BACKGROUND & AIMS: :The in vitro activity of 21 antimicrobial agents against 143 Acinetobacter strains (belonging to 12 different DNA hybridization groups) was studied. Of the antibiotics tested, ciprofloxacin, ofloxacin, doxycycline and imipenem had the lowest MICs. For most antibiotics there was a considerable overlap of the MICs between the DNA groups; however, some differences in antimicrobial susceptibility between DNA groups were found. Strains of DNA groups 2 (A. baumannii) and 13 (unnamed) were most resistant, and strains of DNA groups 8 (A. lwoffii) and 5 (A. junii) less resistant. Many DNA groups contain both saccharolytic and non-saccharolytic strains but in the present study no differences in antimicrobial susceptibility were found between strains of a particular DNA group with regard to this property.

背景与目标： : 研究了21种抗菌剂对143不动杆菌菌株 (属于12个不同的DNA杂交组) 的体外活性。在测试的抗生素中，环丙沙星，氧氟沙星，强力霉素和亚胺培南的mic最低。对于大多数抗生素，DNA组之间的mic有相当大的重叠; 但是，发现DNA组之间的抗菌药物敏感性存在一些差异。DNA组2 (鲍曼不动杆菌) 和13 (未命名) 的菌株抗性最高，而DNA组8 (A. lwoffii) 和5 (A. junii) 的菌株抗性较低。许多DNA组同时包含糖分解和非糖分解菌株，但在本研究中，就该特性而言，特定DNA组的菌株之间未发现抗菌药物敏感性差异。

BACKGROUND & AIMS: :Antimicrobial peptides (AMPs) represent a promising therapeutic alternative for the treatment of antibiotic-resistant bacterial infections. The present study investigates the antimicrobial activity of new, rationally-designed derivatives of a short α-helical peptide, RR. From the peptides designed, RR4 and its D-enantiomer, D-RR4, emerged as the most potent analogues with a more than 32-fold improvement in antimicrobial activity observed against multidrug-resistant strains of Pseudomonas aeruginosa and Acinetobacter baumannii. Remarkably, D-RR4 demonstrated potent activity against colistin-resistant strains of P. aeruginosa (isolated from cystic fibrosis patients) indicating a potential therapeutic advantage of this peptide over several AMPs. In contrast to many natural AMPs, D-RR4 retained its activity under challenging physiological conditions (high salts, serum, and acidic pH). Furthermore, D-RR4 was more capable of disrupting P. aeruginosa and A. baumannii biofilms when compared to conventional antibiotics. Of note, D-RR4 was able to bind to lipopolysaccharide to reduce the endotoxin-induced proinflammatory cytokine response in macrophages. Finally, D-RR4 protected Caenorhabditis elegans from lethal infections of P. aeruginosa and A. baumannii and enhanced the activity of colistin in vivo against colistin-resistant P. aeruginosa.

背景与目标： 抗菌肽 (AMPs) 是治疗抗生素耐药性细菌感染的一种有前途的治疗选择。本研究调查了短 α-螺旋肽RR的新的，合理设计的衍生物的抗菌活性。从设计的肽中，RR4及其D-对映异构体D-RR4成为最有效的类似物，对铜绿假单胞菌和鲍曼不动杆菌的多重耐药菌株的抗菌活性提高了32倍以上。值得注意的是，D-RR4显示出对铜绿假单胞菌 (从囊性纤维化患者中分离出) 的粘菌素抗性菌株的有效活性，表明该肽在几种AMPs上具有潜在的治疗优势。与许多天然amp相比，D-RR4在具有挑战性的生理条件 (高盐、血清和酸性pH) 下保持其活性。此外，与常规抗生素相比，D-RR4更有能力破坏铜绿假单胞菌和鲍曼不动杆菌生物膜。值得注意的是，D-RR4能够与脂多糖结合以减少巨噬细胞中内毒素诱导的促炎性细胞因子反应。最后，D-RR4保护秀丽隐杆线虫免受铜绿假单胞菌和鲍曼不动杆菌的致命感染，并增强粘菌素在体内抵抗粘菌素抗性铜绿假单胞菌的活性。

BACKGROUND & AIMS: BACKGROUND:Acinetobacter baumannii is characterized by strictly aerobic, gram-negative, nonmotile, nonlactose-fermenting, oxidase-negative, catalase-positive coccobacilli, and the combination of its environmental resilience and its rapid development of resistance to multiple classes of antimicrobials renders it a successful nosocomial pathogen. OBJECTIVES:The aim of this study was to identify specific risk factors and outcome of nosocomial pneumonia because of carbapenem-resistant Acinetobacter baumannii (CRAB). METHODS:The retrospective study, set in a 1,500-bed referral and tertiary care hospital, was conducted to analyze the clinical and microbiologic data of patients with nosocomial pneumonia because of Acinetobacter baumannii (A baumannii) from January 2006 to December 2011. Comparisons were made between patients with CRAB pneumonia and patients with carbapenem-susceptible A baumannii (CSAB) pneumonia. Only the first isolation of A baumannii was considered. RESULTS:A total of 145 patients with CSAB pneumonia and 97 patients with CRAB pneumonia was included. Among these patients, the independent risk factors for acquiring CRAB pneumonia were Acute Physiology and Chronic Health Evaluation II (APACHE II) score (>20) at admission, systemic illnesses (chronic respiratory disease and cerebrovascular accident), presence of excess noninvasive or invasive devices (mechanical ventilation), and ever used antibiotics within 28 days (carbapenem and cefepime). The patients with CRAB pneumonia had higher mortality rate than CSAB pneumonia. Multivariate analysis showed that, among patients with A baumannii pneumonia, APACHE II score (>20) at pneumonia onset, infections with other microorganisms, and inappropriate therapy were independently associated with 28-day mortality. CONCLUSION:Patients with CRAB pneumonia have a higher mortality rate than those with CSAB pneumonia. The nosocomial occurrence of CRAB pneumonia is strongly related to systemic illnesses, APACHE II score, mechanical ventilation, and ever used antibiotics within 28 days.

背景与目标：

BACKGROUND & AIMS: :Based on phylogenetic analyses, strain M2a isolated from honey, an unexpected source of acinetobacters, was classified as Acinetobacter lwoffii. The genome of this strain is strikingly crowded with mobile genetic elements. It harbours more than 250 IS elements of 15 IS-families, several unit and compound transposons and 15 different plasmids. These IS elements, including 30 newly identified ones, could be classified into at least 53 IS species. Regarding the plasmids, 13 of the 15 belong to the Rep-3 superfamily and only one plasmid, belonging to the "Low-GC" family, possesses a seemingly complete conjugative system. The other plasmids, with one exception, have a mobilization region of common pattern, consisting of the divergent mobA/mobL-family and mobS-, mobC- or traD-like genes separated by an oriT-like sequence. Although two plasmids of M2a are almost identical to those of A. lwoffi strains isolated from gold mine or Pleistocene sediments, most of them have no close relatives. The presence of numerous plasmid-borne and chromosomal metal resistance determinants suggests that M2a previously has also evolved in a metal-polluted environment. The numerous, possibly transferable, plasmids and the outstanding number of transposable elements may reflect the high potential of M2a for rapid evolution.

背景与目标： : 根据系统发育分析，从蜂蜜 (一种意想不到的不动杆菌来源) 中分离出的M2a菌株被归类为lwoffii不动杆菌。该菌株的基因组中明显挤满了可移动的遗传元件。它拥有15个IS家族的250多个IS元素，几个单元和化合物转座子以及15个不同的质粒。这些IS元素，包括30个新发现的元素，可以分为至少53个IS物种。关于质粒，15个质粒中有13个属于Rep-3超家族，只有一个属于 “低GC” 家族的质粒具有看似完整的结合系统。除了一个例外，其他质粒具有共同模式的动员区域，由不同的mobA/mobL家族和mobS，mobC或traD样基因组成，这些基因由oriT样序列分开。尽管M2a的两个质粒与从金矿或更新世沉积物中分离的A. lwoffi菌株的质粒几乎相同，但它们中的大多数没有近亲。许多质粒传播和染色体金属抗性决定簇的存在表明，M2a以前也在金属污染的环境中进化。大量可能可转移的质粒和出色数量的转座元件可能反映了M2a快速进化的巨大潜力。

BACKGROUND & AIMS: :Acinetobacter baumannii and Pseudomonas aeruginosa are gram-negative pathogens that target immunocompromised patients. They express a variety of determinants that confer resistance to a broad array of antimicrobial agents. Mechanisms of resistance include impaired entry through the bacterial outer membrane, production of antibiotic-modifying enzymes, active efflux, and target mutations that reduce antimicrobial affinity. It has been a challenge to identify new agents that have activity against the more resistant variants of these species. Doripenem is a carbapenem in phase 3 trials that has excellent activity against P. aeruginosa and A. baumannii. However, it lacks activity against strains that express resistance to the currently available carbapenems. Tigecycline is a newly licensed glycylcycline that lacks activity against P. aeruginosa but has encouraging activity against many A. baumannii isolates. Resistance to tigecycline can emerge during therapy, however, and is due to expression of multidrug efflux pumps.

背景与目标： : 鲍曼不动杆菌和铜绿假单胞菌是针对免疫功能低下患者的革兰氏阴性病原体。它们表达了多种决定因素，赋予了对多种抗菌剂的耐药性。耐药机制包括通过细菌外膜的进入受损，抗生素修饰酶的产生，主动外排以及降低抗菌亲和力的靶突变。确定对这些物种更具抗性的变体具有活性的新药物一直是一个挑战。Doripenem是3期试验中的碳青霉烯类化合物，对铜绿假单胞菌和鲍曼不动杆菌具有优异的活性。但是，它对表达对当前可用碳青霉烯类抗性的菌株缺乏活性。替加环素是一种新获得许可的甘氨环素，对铜绿假单胞菌缺乏活性，但对许多鲍曼不动杆菌分离株具有令人鼓舞的活性。但是，在治疗过程中会出现对替加环素的耐药性，这是由于多药外排泵的表达所致。

BACKGROUND & AIMS: :Active porins were isolated and purified from the outer membranes of the gram-negative anaerobic rod Porphyromonas asaccharolytica and the aerobic coccobacillus Acinetobacter baumannii. The porins from both bacteria appear to be monomers when isolated and purified. Both porins exhibited decreased mobility on SDS-PAGE after boiling for 10 min in the sample buffer. After heating, their molecular weight is estimated at 43 kDa while without heating they run as proteins with a molecular weight of approximately 37 kDa. Due to their characteristic heat-modifiability, these proteins were named HMP (heat-modifiable protein)-P. asaccharolytica and HMP-A. baumannii. Amino acid analysis revealed both porins to be hydrophilic proteins. These proteins have been shown to be active in transporting sugars when incorporated into liposomes. The permeability of both porins for L-arabinose was less than that produced by the porin of Escherichia coli B. Permeability to high molecular weight disaccharides was lower than for small monosaccharides. Western blot analysis did not reveal any antigenic cross reaction between HMP-A. baumannii and the HMP-P. asaccharolytica. The results obtained in this study confirm that although these heat-modifiable proteins are pore forming proteins and have similar activity they differ in their antigenicity.

背景与目标： : 从革兰氏阴性厌氧杆状卟啉单胞菌和需氧球芽孢杆菌鲍曼不动杆菌的外膜中分离并纯化活性孔蛋白。分离和纯化后，两种细菌的孔蛋白似乎都是单体。在样品缓冲液中煮沸10分钟后，两种孔蛋白在sdds-PAGE上的迁移率均降低。加热后，它们的分子量估计为43 kDa，而在不加热的情况下，它们作为分子量约为37 kDa的蛋白质运行。由于其特征性的热修饰性，这些蛋白质被命名为HMP (热可修饰蛋白)-P。asaccharolytica和HMP-A. baumannii。氨基酸分析表明，两种孔蛋白都是亲水性蛋白。这些蛋白质已被证明在掺入脂质体中时具有转运糖的活性。两种孔蛋白对L-阿拉伯糖的渗透性均小于大肠杆菌B的孔蛋白产生的渗透性。对高分子量二糖的渗透性低于对小单糖的渗透性。Western印迹分析未显示HMP-A之间的任何抗原交叉反应。鲍曼不动杆菌和HMP-P. asaccharolytica。在这项研究中获得的结果证实，尽管这些热修饰蛋白是成孔蛋白，并且具有相似的活性，但它们的抗原性不同。

BACKGROUND & AIMS: :Short nucleotide sequence repetitions in DNA can provide selective benefits and also can be a source of genetic instability arising from deletions guided by pairing between misaligned strands. These findings raise the question of how the frequency of deletion mutations is influenced by the length of sequence repetitions and by the distance between them. An experimental approach to this question was presented by the heat-sensitive phenotype conferred by pcaG1102, a 30-bp deletion in one of the structural genes for Acinetobacter baylyi protocatechuate 3,4-dioxygenase, which is required for growth with quinate. The original pcaG1102 deletion appears to have been guided by pairing between slipped DNA strands from nearby repeated sequences in wild-type pcaG. Placement of an in-phase termination codon between the repeated sequences in pcaG prevents growth with quinate and permits selection of sequence-guided deletions that excise the codon and permit quinate to be used as a growth substrate at room temperature. Natural transformation facilitated introduction of 68 different variants of the wild-type repeat structure within pcaG into the A. baylyi chromosome, and the frequency of deletion between the repetitions was determined with a novel method, precision plating. The deletion frequency increases with repeat length, decreases with the distance between repeats, and requires a minimum amount of similarity to occur at measurable rates. Deletions occurred in a recA-deficient background. Their frequency was unaffected by deficiencies in mutS and was increased by inactivation of recG.

背景与目标： : DNA中的短核苷酸序列重复可以提供选择性益处，也可能是由于错配链之间配对指导的缺失引起的遗传不稳定的来源。这些发现提出了一个问题，即序列重复的长度以及它们之间的距离如何影响缺失突变的频率。pcaG1102赋予的热敏表型提出了解决此问题的实验方法，pcaG1102是baylyi不动杆菌原儿茶酸3,4-双加氧酶结构基因之一中的30 bp缺失，这是用quinate生长所必需的。最初的pcaG1102缺失似乎是通过野生型pcaG中附近重复序列中缺失的DNA链之间的配对来指导的。在pcaG中的重复序列之间放置同相终止密码子可防止quinate的生长，并允许选择序列引导的缺失，以切除密码子并允许quinate在室温下用作生长底物。自然转化促进了将pcaG中野生型重复结构的68种不同变体引入到baylyi染色体中，并通过一种新颖的方法 (精密电镀) 确定了重复之间的缺失频率。删除频率随重复长度的增加而增加，随重复之间的距离而减小，并且要求以可测量的速率发生最小量的相似性。缺失发生在缺乏rec的背景下。它们的频率不受mutS缺陷的影响，并且由于recG的失活而增加。