鲍曼不动杆菌的临床分布及耐药情况分析

目的：了解高邮市人民医院鲍曼不动杆菌的临床分布状况及耐药情况,为有效预防和控制医院感染、指导临床合理用药提供理论依据。方法对2010-2012年我院临床分离的鲍曼不动杆菌进行鉴定,采用纸片扩散法进行药敏试验,采用 WHONET 5．6软件对数据进行统计分析鲍曼不动杆菌的科室分布情况与耐药率及变化趋势。结果3年共分离出155株鲍曼不动杆菌,主要分离来自痰液（82．6％）,其次为分泌物及脓汁（12．3％）;科室分布以 ICU （34．2％）为主,其次是神经外科（18．1％）和呼吸内科（15．5％）;3年来鲍曼不动杆菌总体耐药率呈现上升趋势,尤其以亚胺培南最为明显,亚胺培南3年的耐药率分别是23．3％,44．2％和68．3％;临床常用抗菌药物中只有头孢哌酮/舒巴坦和哌拉西林/他唑巴坦的耐药率低于40％,其余均大于65％。结论鲍曼不动杆菌是医院感染中重要的条件致病菌,且耐药率较高,临床医务人员应根据药敏结果合理选择抗菌药物,控制耐药菌株的流行及医院感染。     

鲍曼不动杆菌的耐药性分析

鲍曼不动杆菌作为条件致病菌广泛存在于自然界,由于广谱抗生素的大量应用,其引起院内感染的重要性越来越受到人们的重视,尤其近年来其耐药性逐渐增强,使得临床选择抗生素越来越局限.为此,对临床分离的91株鲍曼不动杆菌的药敏结果进行总结、分析.     

耐亚胺培南鲍曼不动杆菌的耐药性分析

目的探讨我院耐亚胺培南鲍曼不动杆菌的耐药特性。方法对2009年1月至2011年12月我院临床标本采用常规方法进行蓠株分离,采用Vitek-32全自动细茼鉴定药敏系统及绒片扩散法（K—B法）测定鲍曼不动杆菌对16种抗菌药物的敏感性。结果．共检测到91株鲍曼不动杆菌,其中耐亚胺墙南的鲍曼不动杆菌为23株（占25．3％）,标本来源大部分为痰液（占94．9％）。耐亚胺培南鲍曼不动杆菌对常用16种抗蕾药物耐药率〉50％的有15种,耐药率〉90％有3种,分剐为氨苄西林（98．O％）、头孢唑林（99．O％）和呋喃妥因（99．0％）,对抗菌药物耐药率最低仅为头孢哌嗣／舒巳坦（10．2％）,另外检测到对所用抗菌素泛耐为4株（8．O％）;而对亚胺培南敏感的鲍曼不动杆菌对常用16种抗菌药物耐药率〉50％的仅为4种,耐药率〉90％同样为氨苄西林（100％）、头孢唑林（97．9％）和呋喃妥因（97．9％）,耐药率比较低的为美罗培南（10．4％）、妥布霉素（16．7％）和环丙沙星（16．7％）,耐药率最低也为头孢哌酮／舒巴坦（6．3％）。结论我院耐亚胺培南鲍曼不动杆茼多重耐药性严重,出现了泛耐菌株;临床可根据药敏试验选用抗茼药物,一般条件下耐亚胺培南鲍曼不动杆菌建议选用头孢哌嗣／舒巴坦。     

Novobiocin Inhibits the Antimicrobial Resistance Acquired through DNA Damage-Induced Mutagenesis in Acinetobacter baumannii

Acinetobacter baumannii, a worldwide emerging nosocomial pathogen, acquires antimicrobial resistances in response to DNA-damaging agents, which increase the expression of multiple error-prone DNA polymerase components. Here we show that the aminocoumarin novobiocin, which inhibits the DNA damage response in Gram-positive bacteria, also inhibits the expression of error-prone DNA polymerases in this Gram-negative multidrug-resistant pathogen and, consequently, its potential acquisition of antimicrobial resistance through DNA damage-induced mutagenesis.     

Role of Acinetobacter baumannii UmuD Homologs in Antibiotic Resistance Acquired through DNA Damage-Induced Mutagenesis

The role of Acinetobacter baumannii ATCC 17978 UmuDC homologs A1S_0636-A1S_0637, A1S_1174-A1S_1173, and A1S_1389 (UmuD_Ab) in antibiotic resistance acquired through UV-induced mutagenesis was evaluated. Neither the growth rate nor the UV-related survival of any of the three mutants was significantly different from that of the wild-type parental strain. However, all mutants, and especially the umuD_Ab mutant, were less able to acquire resistance to rifampin and streptomycin through the activities of their error-prone DNA polymerases. Furthermore, in the A. baumannii mutant defective in the umuD_Ab gene, the spectrum of mutations included a dramatic reduction in the frequency of transition mutations, the mutagenic signature of the DNA polymerase V encoded by umuDC.     

In Vitro Activities of Combinations of Rifampin with Other Antimicrobials against Multidrug-Resistant Acinetobacter baumannii

The antimicrobial treatment of multidrug-resistant (MDR) Acinetobacter baumannii infections has become a great challenge for medical staff all over the world. Increasing numbers of MDR A. baumannii infections have been identified and reported, but effective clinical treatments for them are decreasing. The objective of this study was to investigate the in vitro activities of combinations of rifampin (an established antimicrobial) and other antimicrobials, including biapenem, colistin, and tigecycline, against 73 clinical isolates of MDR A. baumannii. In total, 73 clinical isolates of MDR A. baumannii were collected from two A-level general hospitals in Beijing, and the MICs of rifampin, biapenem, colistin, and tigecycline were determined. The checkerboard method was used to determine the fractional inhibitory concentration indices (FICIs), that is, whether the combinations acted synergistically against these isolates. The MIC₅₀, MIC₉₀, and MIC_range of rifampin combined with biapenem, colistin, and tigecycline against the isolates were clearly lower than those for four antimicrobials (rifampin, biapenem, colistin, and tigecycline) that were used alone. Combinations of rifampin with biapenem, colistin, and tigecycline individually demonstrated the following interactions: synergistic interactions (FICI ≤ 0.5) for 31.51%, 34.25%, and 31.51% of the isolates, partially synergistic interactions (0.5 < FICI < 1) for 49.31%, 43.83%, and 47.94% of the isolates, and additive interactions (FICI = 1) for 19.18%, 21.92%, and 20.55% of the isolates, respectively. There were no indifferent (1 < FICI < 4) or antagonistic (FICI ≥ 4) interactions. Therefore, combinations of rifampin with biapenem, colistin, or tigecycline may be future therapeutic alternatives for the treatment of MDR A. baumannii infections.     

Role of OmpA in the Multidrug Resistance Phenotype of Acinetobacter baumannii

Acinetobacter baumannii has emerged as a nosocomial pathogen with an increased prevalence of multidrug-resistant strains. The role of the outer membrane protein A (OmpA) in antimicrobial resistance remains poorly understood. In this report, disruption of the ompA gene led to decreased MICs of chloramphenicol, aztreonam, and nalidixic acid. We have characterized, for the first time, the contribution of OmpA in the antimicrobial resistance phenotype of A. baumannii.     

Novel Engineered Peptides of a Phage Lysin as Effective Antimicrobials against Multidrug-Resistant Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative bacterial pathogen responsible for a range of nosocomial infections. The recent rise and spread of multidrug-resistant A. baumannii clones has fueled a search for alternative therapies, including bacteriophage endolysins with potent antibacterial activities. A common feature of these lysins is the presence of a highly positively charged C-terminal domain with a likely role in promoting outer membrane penetration. In the present study, we show that the C-terminal amino acids 108 to 138 of phage lysin PlyF307, named P307, alone were sufficient to kill A. baumannii (>3 logs). Furthermore, P307 could be engineered for improved activity, the most active derivative being P307_SQ-8C (>5-log kill). Both P307 and P307_SQ-8C showed high in vitro activity against A. baumannii in biofilms. Moreover, P307_SQ-8C exhibited MICs comparable to those of levofloxacin and ceftazidime and acted synergistically with polymyxin B. Although the peptides were shown to kill by disrupting the bacterial cytoplasmic membrane, they did not lyse human red blood cells or B cells; however, serum was found to be inhibitory to lytic activity. In a murine model of A. baumannii skin infection, P307_SQ-8C reduced the bacterial burden by ∼2 logs in 2 h. This study demonstrates the prospect of using peptide derivatives from bacteriophage lysins to treat topical infections and remove biofilms caused by Gram-negative pathogens.     

2007-2009年鲍曼不动杆菌的耐药性分析

目的探讨2007年1月至2009年6月浙江省乐清市人民医院检出的鲍曼不动杆菌(AB)对常用抗生素的耐药性变化趋势,以指导临床合理选用抗生素。方法对该院2007年1月至2009年6月分离的非重复的革兰阴性杆菌使用法国生物梅里埃公司ATB细菌鉴定仪鉴定菌种,并做药敏试验,以明确AB对常用抗菌药物的体外耐药情况。结果 220株AB中85株来自重症监护病房(ICU),85%分离自痰标本。哌拉西林的耐药率从19.5%上升至66.7%。头孢噻肟、头孢他啶和头孢吡肟的耐药率从10%左右上升到60%以上。头孢呋辛的耐药率2008年达到97.7%。亚胺培南的耐药率从5.2%上升至56.1%。氨基糖苷类和喹诺酮类的耐药率均增高。从ICU分离到的AB比非ICU的AB的耐药率普遍高30%以上。结论 AB对多种抗菌药物耐药性迅速上升。应改善医疗环境条件,增强医务人员无菌观念,合理使用抗菌药物,加强对该菌耐药性的监测,以延缓耐药菌株上升,预防和控制病区内AB流行。     

Multiple Genetic Mutations Associated with Polymyxin Resistance in Acinetobacter baumannii

We studied polymyxin B resistance in 10 pairs of clinical Acinetobacter baumannii isolates, two of which had developed polymyxin B resistance in vivo. All polymyxin B-resistant isolates had lower growth rates than and substitution mutations in the lpx or pmrB gene compared to their parent isolates. There were significant differences in terms of antibiotic susceptibility and genetic determinants of resistance in A. baumannii isolates that had developed polymyxin B resistance in vivo compared to isolates that had developed polymyxin B resistance in vitro.     

铜陵地区鲍曼不动杆菌的分布及耐药性特点

目的了解安徽省铜陵地区鲍曼不动杆菌的耐药性变迁和临床分布特点,为合理应用抗菌药物和预防控制医院感染提供依据。方法回顾性分析2003年1月—2010年12月铜陵地区5所医院临床分离1 432株鲍曼不动杆菌的药敏试验资料,药敏试验采用Kirby-Bauer法。结果鲍曼不动杆菌对亚胺培南、美罗培南、头孢哌酮-舒巴坦和米诺环素敏感率较高,对其他抗菌药物耐药率均较高,对常用抗菌药物耐药率总体呈上升趋势;鲍曼不动杆菌感染主要发生在ICU、呼吸科和脑外科,依次占22.5%、15.6%和13.4%;本研究检测标本来源主要为痰,占72.0%,其次为皮肤软组织创面,占13.3%。结论鲍曼不动杆菌多重耐药现象严重,对常用抗菌药物耐药率逐年上升,其所致感染应根据药敏试验结果合理用药。ICU、呼吸科等是预防控制的重点科室,应加强感染控制措施。     

Clinical and Epidemiological Significance of Carbapenem Resistance in Acinetobacter baumannii Infections

Carbapenems are considered the treatment of choice for Acinetobacter baumannii infections. Many facilities implement preventive measures toward only carbapenem-resistant A. baumannii (CRAB). However, the independent role of the carbapenem resistance determinant on patient outcomes remains controversial. In a 6-year analysis of adults with A. baumannii bloodstream infection (BSI), the outcomes of 149 CRAB isolates were compared to those of 91 patients with carbapenem-susceptible A. baumannii. In bivariable analyses, CRAB BSIs were significantly associated with worse outcomes and with a delay in the initiation of appropriate antimicrobial therapy (DAAT). However, in multivariable analyses, carbapenem resistance status was no longer associated with poor outcomes, while DAAT remained an independent predictor. The epidemiological significance of A. baumannii should not be determined by its resistance to carbapenems.     

鲍曼不动杆菌耐药分析

目的：为了解鲍曼不动杆菌在医院感染中的地位,动态监测其耐药性及其发展趋势,为临床合理应用抗生素提供依据。方法：API及VITEK2鉴定系统对菌株进行鉴定,用K-B纸片扩散法进行药敏试验,用WHONET5软件对药敏结果进行统计学分析。结果：2001/2003年所监测抗生素的耐药性有逐步升高的趋势,尤以2003年上升更为显著,特别是鲍曼不动杆菌对碳青霉烯类耐药率增加迅速,ICU病房对亚胺培南耐药率达35%。结论：鲍曼不动杆菌耐药性日趋严重,应引起高度重视。     

泛耐药鲍曼不动杆菌耐药机制及所涉感染诱因探讨

目的探讨泛耐药鲍曼不动杆菌(PDR-AB)耐药机制及所涉感染诱因。方法收集鲍曼不动杆菌感染者分离菌株104株,PCR检测PDR-AB组和非PDR-AB组菌株16S rRNA甲基化酶基因、碳青霉烯类耐药基因和生物膜相关基因,微量半定量法检测菌株生物膜形成能力,微量肉汤稀释法测定菌株的最低抑菌浓度(MIC),并回顾性分析感染者的临床诱因。结果 104株菌株分为PDR-AB 28株和非PDR-AB 76株;PDR-AB组blaOXA-23、blaVIM、aba I和csu E基因携带率均高于非PDR-AB组(P0.05),两组生物膜形成能力差异无统计学意义(P0.05);PDR-AB组患者平均住院日、侵入性治疗(大于48 h)发生率、菌株分离前3种及以上抗菌药物使用率及抗菌药物暴露时间均高于非PDR-AB感染组患者(P0.05)。结论 PDR-AB耐药与相关耐药基因携带有关,而PDR-AB感染与患者进行侵入性治疗、感染前抗菌药物暴露等临床诱因有关。     

Molecular Mechanisms of Sulbactam Antibacterial Activity and Resistance Determinants in Acinetobacter baumannii

Sulbactam is a class A β-lactamase inhibitor with intrinsic whole-cell activity against certain bacterial species, including Acinetobacter baumannii. The clinical use of sulbactam for A. baumannii infections is of interest due to increasing multidrug resistance in this pathogen. However, the molecular drivers of its antibacterial activity and resistance determinants have yet to be precisely defined. Here we show that the antibacterial activities of sulbactam vary widely across contemporary A. baumannii clinical isolates and are mediated through inhibition of the penicillin-binding proteins (PBPs) PBP1 and PBP3, with very low frequency of resistance; the rare pbp3 mutants with high levels of resistance to sulbactam are attenuated in fitness. These results support further investigation of the potential clinical utility of sulbactam.     

Resistance to Colistin in Acinetobacter baumannii Associated with Mutations in the PmrAB Two-Component System

The mechanism of colistin resistance (Col^r) in Acinetobacter baumannii was studied by selecting in vitro Col^r derivatives of the multidrug-resistant A. baumannii isolate AB0057 and the drug-susceptible strain ATCC 17978, using escalating concentrations of colistin in liquid culture. DNA sequencing identified mutations in genes encoding the two-component system proteins PmrA and/or PmrB in each strain and in a Col^r clinical isolate. A colistin-susceptible revertant of one Col^r mutant strain, obtained following serial passage in the absence of colistin selection, carried a partial deletion of pmrB. Growth of AB0057 and ATCC 17978 at pH 5.5 increased the colistin MIC and conferred protection from killing by colistin in a 1-hour survival assay. Growth in ferric chloride [Fe(III)] conferred a small protective effect. Expression of pmrA was increased in Col^r mutants, but not at a low pH, suggesting that additional regulatory factors remain to be discovered.Among gram-negative pathogens that are reported as “multidrug resistant” (MDR), Acinetobacter baumannii is rapidly becoming a focus of significant attention (1, 7, 25, 32, 38, 39, 46, 51). In intensive care units, up to 30% of A. baumannii clinical isolates are resistant to at least three classes of antibiotics, often including fluoroquinolones and carbapenems (25).The emergence of MDR gram-negative pathogens, including A. baumannii, has prompted increased reliance on the cationic peptide antibiotic colistin (12). Regrettably, increasing colistin use has led to the discovery of resistant strains (10, 11, 22, 26). For example, in a recent study, 12% of carbapenemase-producing Enterobacteriaceae were found to be colistin resistant (Col^r) (6). Although still uncommon, A. baumannii isolates resistant to all available antimicrobial agents have been reported (26, 45) and are of enormous concern, given their potential to spread in the critical care environment.Colistin and other polymyxins are cyclic cationic peptides produced by the soil bacterium Bacillus polymyxa that act by disrupting the negatively charged outer membranes of gram-negative bacteria (37, 50). The following three distinct mechanisms that give rise to colistin resistance are known: (i) specific modification of the lipid A component of the outer membrane lipopolysaccharide, resulting in a reduction of the net negative charge of the outer membrane; (ii) proteolytic cleavage of the drug; and (iii) activation of a broad-spectrum efflux pump (13, 14, 49). The mechanism of colistin resistance in Acinetobacter spp. is not yet known. Heteroresistance to colistin in A. baumannii has been described (17, 24), but it is uncertain whether the basis for this resistance is the presence of a genetically distinct population of cells or whether variation in the regulatory program among genetically identical cells may be sufficient for the expression of resistance.In Salmonella enterica, the two-component signaling systems PmrAB and PhoPQ are involved in sensing environmental pH, Fe³⁺, and Mg²⁺ levels, leading to altered expression of a set of genes involved in lipid A modification (14, 43, 53). A small adapter protein, PmrD, serves as an interface between the two-component systems by stabilizing the activated form of PmrA in S. enterica (19), but other mechanisms of coordinated regulation are described for other species (52). Mutations causing constitutive activation of PmrA and PmrB are associated with colistin resistance (31, 33). Interestingly, the phoPQ and pmrD genes do not appear to be present in Acinetobacter spp., based on computational analysis of the genome sequences (2).PmrA-regulated resistance to colistin in S. enterica and P. aeruginosa results from modification of lipid A with 4-deoxy-aminoarabinose (Ara4N) or phosphoethanolamine via activation of ugd, the pmrF (or pbgP) operon, and pmrC, which encode UDP-glucose dehydrogenase (the first step in Ara4N biosynthesis), Ara4N biosynthetic enzymes, and lipid A phosphoethanolamine transferase, respectively (8, 15, 21, 41, 48). The Ara4N biosynthesis and attachment genes are not present in A. baumannii or Neisseria meningitidis (36, 47). N. meningitidis is intrinsically resistant to polymyxins, demonstrating that Ara4N modification of lipid A is not required for resistance. Mutations in the pmrC ortholog lptA, encoding the lipid A phosphoethanolamine transferase, reduce colistin resistance in N. meningitidis, suggesting that this modification alone may be sufficient for conferring colistin resistance (49). Here we show that the PmrAB system is involved in regulating colistin resistance in A. baumannii by identification of mutations in resistant isolates that exhibit constitutive expression of pmrA.