Molecular characterization of class 1 integrons and antimicrobial resistance in Aeromonas strains from foodborne outbreak-suspect samples and environmental sources in Taiwan

One hundred thirty-three Aeromonas spp. isolates were examined for multiple antibiotic resistance phenotypes and prevalence of class 1 integron sequences. Twenty-four (18.0%) of these isolates contained class 1 integron. Seven different class 1 integrons were found among 24strains, with a total of 10 different gene cassettes encoding for resistance to trimethoprim (dfr12 and dfr2d), aminoglycosides (aadA1 and aadA2), beta-lactam antibiotics (oxa2), chloramphenicol (catB3 and catB8), quaternary ammonium amines (qacE2), and 2 ORFs (orfD and orfF) with unknown function. Rate of antibiotic resistance was different between integron-positive and integron-negative strains. Trimethoprim and trimethoprim-sulphamethoxazole resistances were commonly associated with integron, and all of integron-positive isolates were multiple resistant to more than 3 agents. Resistance to as many as 10 antimicrobial agents were observed in integron-positive strains. Several cassette arrays of class 1 integrons identified in this study were not previously reported in Aeromonas strains. This study demonstrates the wide distribution of class 1 integron in Aeromonas spp. isolated from foodborne outbreak-suspect samples and environmental sources in Taiwan.     

Clonal dissemination of a single Shigella sonnei strain among Iranian children during Fall 2012 in Tehran,I.R. Iran

Shigella species are a common cause of bacterial diarrhea worldwide and the disease is characterized by seasonality. Shigella has been encountered by widespread resistance to commonly used antibiotics which is a serious concern. The aim of this study was to analyze the epidemiological relatedness of Shigella strains isolated from children during one year period by PFGE method and to investigate antimicrobial resistance determinants and cassettes among Shigella species. The occurrence of Shigella spp. in the present study was 1.32% during the study period and the majority of cases (56 (80%)) were occurred during autumn while Shigella sonnei was the most prevalent species identified. Multi-drug resistance phenotype was seen in 98.5% of total isolates with SXT^r/TE^r/TMP^r resistance pattern. Among the 70 Shigella spp. analyzed in this study, 16 isolates were positive for class I integron (int1⁺) with two types of gene cassette arrays (dfrA17/aadA5 and dfrA7).The class 2 integron was more frequently detected among the isolates (85.71%) with dfrA1/sat1/aadA1 (10%) and dfrA1/sat1 (75.71%) gene cassettes. The tetA and tetB determinants were observed in 75.7% and 21.42% of Shigella isolates and tet(A) was the foremost in S. sonnei and Shigella flexneri population. In this study 5 tetracycline resistant isolates had no tetracycline resistance gene (A–D) and no association was recognized between the value of MIC against tetracycline and the tet genes content of isolates. Fifty three of total Shigella isolates (75.7%) showed an identical PFGE patterns. Seven PFGE clusters observed in our study were composed of members with one to three band variations, which is indicative of closely related isolates. The major cluster (cluster C) constituted 75.7% of total isolates, all of which (except eight isolates) consonantly showed identical class 2 integron of 1500 bp which strongly suggests the dissemination of a single S. sonnei clone among the pediatric population in 2012 autumn in Tehran, Iran, in comparison with the equal data from the comparable time period from recent years.     

The new perspective of old antibiotic: In vitro antibacterial activity of TMP-SMZ against Klebsiella pneumoniae

Background/purposeTrimethoprim-sulfamethoxazole (TMP-SMZ) is broadly administered to treat multiple infections, and the paucity of effective treatment alternatives for infections caused by Klebsiella pneumoniae has led to a renewed interest in TMP-SMZ. The aim of this study is to evaluate the antibacterial efficacy of TMP-SMZ against K. pneumoniae.MethodsThe resistance genes of K. pneumoniae clinical isolates were investigated by PCR, followed by conjugation experiments and multilocus sequence typing.ResultsThe resistance rate of K. pneumoniae to TMP-SMZ decreased over the collection period from 26.7% (88/330) to 16.9% (56/332). The high carrying rates (173/175, 98.9%) of resistance determinants (sul genes or dfr genes) were the main mechanisms of TMP-SMZ resistance isolates, with sul1 (142/175, 81.1%) and dfrA1 (119/175, 68.0%). Only class 1 integron was detected, the prevalence of which in TMP-SMZ resistant K. pneumoniae was 63.4% (111/175).ConclusionThese results provided insights into the antimicrobial efficacy of TMP-SMZ against K. pneumoniae, also illustrating the wide distribution of SMZ and TMP resistance genes among resistant K. pneumoniae. Simultaneously, the present study highlights the significance of reasonable administration and effective continued monitoring.     

多药耐药肺炎克雷伯菌碳青霉烯酶及整合子检测与分析

目的了解新疆维吾尔自治区多药耐药肺炎克雷伯菌碳青霉烯酶和整合子分布,为有效控制医院感染提供重要依据。方法收集2010年5月-2011年12月医院各种标本5 208份,使用VITEK-2Compact系统进行菌株的鉴定和药敏试验,对14株肺炎克雷伯菌进行改良Hodge试验,亚胺培南-EDTA协同试验,使用PCR技术检测blaNDM、blaIMP、blaIMI、blaVIM、blaGES、blaKPC、Ⅰ^Ⅲ类整合酶及整合子可变区,并测序明确基因型。结果 14株肺炎克雷伯菌对阿米卡星和妥布霉素的耐药率均为71.42%,对亚胺培南和美罗培南及其他抗菌药物的耐药率均为100.00%;14株多药耐药肺炎克雷伯菌改良Hodge试验有13株表现为阳性,阳性率92.86%;亚胺培南-EDTA纸条法协同试验检测均表现为阴性;PCR检测多药耐药肺炎克雷伯菌均携带KPC-2基因和Ⅰ类整合子;7株整合子可变区扩增出dfrA12-aadA2基因。结论新疆维吾尔自治区发现的多药耐药肺炎克雷伯菌携带KPC-2基因和Ⅰ类整合子,耐药机制与KPC-2和Ⅰ类整合子有关。     

一株铜绿假单胞菌新型整合子检测与分析

目的了解临床分离铜绿假单胞菌PA 091701整合子携带耐药基因情况,探讨新的基因盒排列与多重耐药关系。方法药物敏感试验采用K-B纸片扩散方法,整合子及耐药基因盒的检测采用PCR方法。结果在所测试抗菌药物中,PA091701表现对多粘菌素敏感,对亚胺培南和哌拉西林/他唑巴坦中介,对其它种类抗菌药物耐药;基因盒检测结果显示,PA091701所携带aac（6）’IIa、adA13和oxA10a基因盒为首次出现新的基因盒排列方式,并已登录Gen BankJ：N118546。结论 PA091701携带的基因盒与其对氨基糖苷类、β-内酰胺类耐药有关,表明其多重耐药性除整合子外,还存在其它耐药机制。     

A potential role of aminoglycoside resistance in endemic occurrence of Pseudomonas aeruginosa strains in lower airways of mechanically ventilated patients

Altogether, 98 Pseudomonas aeruginosa isolates from a 5-bed intensive care unit were fingerprinted with pulsed-field gel electrophoresis and tested for aminoglycoside resistance genes aac(6′)-Ib, aac(3″)-IIa, ant(2″)-Ia, armA, rmtA, and rmtB and integrons and virulence genes/operons phzI, phzII, phzM, phzS, apr, lasB, plcH, plcN, pilA, algD, toxA, exoS, exoT, exoY, and exoU. Two major clusters were identified (49 and 19 isolates), harbouring aac(6′)-Ib, bla_PSE-1, and ant(3″)-Ia genes or ant(2″)-Ia gene, respectively, on a class I integron. Most virulence genes except for exoU and pilA were found. Only 1 isolate of the minor cluster (8 isolates) and 1 of the 22 sporadic isolates carried integrons (without gene cassettes); virulence profile was highly variable. Comparing the resistance and virulence patterns of endemic and sporadic isolates suggests that integron-borne aminoglycoside resistance is more closely associated with the frequency than virulence. Consequently, aminoglycoside usage may have played a role in maintenance of the endemic clones.     

多药耐药肺炎克雷伯菌尿液分离株检出gyrA基因新亚型

目的了解1株多药耐药肺炎克雷伯菌的遗传学背景。方法采用聚合酶链反应(PCR)的方法分析1株多药耐药肺炎克雷伯菌可能存在的65种耐药相关基因:包括β-内酰胺类、氨基糖苷类、喹诺酮类耐药相关基因及可移动的遗传元件(整合子、转座子、接合性质粒)遗传标记、抗菌制剂外排泵基因。结果该株多药耐药肺炎克雷伯菌耐β-内酰胺类药物基因检出blaTEM,耐氨基糖苷类药物基因检出aph(3′)-Ⅰ,耐喹诺酮类药物基因检出gyrA,Ⅰ类整合子遗传标记检出intⅠ1,转座子遗传标记检出tnp513,接合性质粒遗传标记检出trbC;抗菌制剂外排泵基因检出qacE△1-sul1,gyrA基因是新亚型(GenBank登录号:JN232083),83位密码子突变方式为TCG→TTC,导致氨基酸从丝氨酸(S)→苯丙氨酸(F);87位密码子突变方式为GAC→GCC,导致氨基酸从天冬氨酸(D)→丙氨酸(A)。结论携带多药耐药基因和抗菌制剂外排泵基因是这株肺炎克雷伯菌呈多药耐药的主要原因,携带多种可移动遗传元件使细菌的耐药性在同种细菌菌株之间,甚至不同种细菌菌株之间得以快速传播。     

水产品中耐药大肠埃希菌整合子与耐药基因盒研究

目的:利用水产品中分离到的耐药大肠埃希菌,研究整合子与耐药性的关系。方法:PCR扩增1类和2类整合酶及整合子,将其进行序列分析。结果:85株耐药大肠埃希菌中88%含有1类整合酶基因;其中68%能扩增此基因;1类整合子可变区PCR扩增产物谱型有17种;1类整合子最常见的基因盒有4种。还发现1株大肠埃希菌同时携带1和2两类不同的整合酶和整合子。结论:大肠埃希菌耐药性与整合子有相关性。     

痰标本分离革兰阴性杆菌整合子分布及分型研究

目的研究临床痰标本分离革兰阴性杆菌中整合子的分布与分型。方法用Ⅰ类、Ⅱ类和Ⅲ类3种整合酶基因通用引物扩增398株痰标本分离革兰阴性杆菌的相应基因;用琼脂对倍稀释法检测临床菌株的MIC。结果Ⅰ类整合酶基因总阳性率为48.7%,Ⅱ类整合酶基因总阳性率为2.3%,未检出Ⅲ类整合酶基因阳性菌株,Ⅰ类和Ⅱ类整合子同时阳性率为1.5%。肠杆菌科细菌Ⅰ类整合酶基因阳性率为69%,Ⅱ类整合子阳性率为2.7%;非发酵菌中Ⅰ类整合子阳性率为34%,Ⅱ类整合子阳性率为1.8%。在肠杆菌科细菌中,Ⅰ类整合酶基因阳性菌株对多种抗菌药物的耐药率均明显高于阴性菌株。结论在痰标本分离的革兰阴性杆菌中,肠杆菌科细菌Ⅰ类整合子的携带率高于非发酵菌,Ⅱ类整合子则无明显区别。     

多药耐药肺炎克雷伯菌噬菌体原/噬菌体、整合子、转座子、插入序列及质粒遗传标记分析

目的 调查多药耐药肺炎克雷伯菌(MDRKP)中噬菌体原/噬菌体、整合子、转座子、插入序列和质粒等可移动遗传元件遗传标记的存在情况.方法 收集2008年8月-2010年5月6所医院共47株MDRKP,采用聚合酶链反应(PCR)及序列分析的方法,分析12种噬菌体原/噬菌体、3种整合子、7种转座子插入序列和两种质粒共24种可移动遗传元件遗传标记.结果 该组MDRKP共检出1种噬菌体原/噬菌体、1种整合子、6种转座子和插入序列、两种质粒遗传标记.结论 携带Ⅰ类整合子(intⅠ 1)、插入序列(IS26、IS903、ISEcp1、ISKpn6)、耐药质粒(trbC)是该组MDRKP耐药的一个重要原因,MDRKP同时作噬菌体原/噬菌体、整合子、转座子、插入序列和质粒等遗传标记检测为国内首次.