Epidemiology of plasmid-mediated quinolone resistance in salmonella enterica serovar typhimurium isolates from food-producing animals in Japan

A total of 225 isolates of Salmonella enterica serovar Typhimurium from food-producing animals collected between 2003 and 2007 were examined for the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants, namely qnrA, qnrB, qnrC, qnrD, qnrS, qepA and aac(6')Ib-cr, in Japan. Two isolates (0.8%) of S. Typhimurium DT104 from different dairy cows on a single farm in 2006 and 2007 were found to have qnrS1 on a plasmid of approximately 9.6-kbp. None of the S. Typhimurium isolates had qnrA, qnrB, qnrC, qnrD, qepA and acc(6')-Ib-cr. Currently in Japan, the prevalence of the PMQR genes among S. Typhimurium isolates from food animals may remain low or restricted. The PFGE profile of two S. Typhimurium DT104 isolates without qnrS1 on the farm in 2005 had an identical PFGE profile to those of two S. Typhimurium DT104 isolates with qnrS1. The PFGE analysis suggested that the already existing S. Typhimurium DT104 on the farm fortuitously acquired the qnrS1 plasmid.     

Molecular characteristics of extended-spectrum β-lactamases in clinical isolates of Enterobacteriaceae from the Philippines

β-Lactamases, including extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases, are major resistance mechanisms of Enterobacteriaceae. Emergence of plasmid-mediated quinolone resistance (PMQR) determinants in ESBL-producing isolates poses a global threat. The molecular characterisitcs of ESBL and PMQR determinants in the Philippines are not well characterized. In this study, we investigated ESBLs and AmpC β-lactamases in clinical isolates of Enterobacteriaceae from the Philippines, and analyzed the association between ESBL and PMQR genes. A total of 91 amoxicilin non-susceptible Enterobacteriaceae were collected at the Research Institute for Tropical Medicine of the Philippines from 2006 to 2008. AmpC- or ESBL-producing isolates were screened by detecting a zone diameter for cefoxitin ≤ 14 mm or cefpodoxime ≤ 20 mm, respectively. Possible ESBL-producing strains were assessed by the ESBL confirmation test of the Clinical and Laboratory Standards Institute. PCR and sequencing were performed to detect the ESBL and PMQR genes. The number of ESBL-producers and AmpC-producers confirmed phenotypically was 17 (18.7%) and 61 (67.0%), respectively. Of 17 phenotypic ESBL-producers, 14 isolates had ESBL genes, including 6 of Escherichia coli, 3 of Enterobacter cloacae, 2 of Enterobacter aerogenes, 2 of Klebsiella pneumoniae, and 1 of Klebsiella ozaenae. Among these isolates, there were 13, 4, and 12 with bla(CTX-M), bla(SHV), and bla(TEM), respectively. Of the bla(CTX-M)-positive isolates, bla(CTX-M-15) shows the highest prevalence, followed by bla(CTX-M-3) and bla(CTX-M-14). Of 14 ESBL-producers identified by PCR, 4, 6, and 7 isolates were positive for qnrB, qnrS, and aac(6')-Ib-cr, respectively. The frequency of aac(6')-Ib-cr positivity was significantly higher among CTX-M-15-producing isolates. Thus, we identified bla(CTX-M), aac(6')-Ib-cr, and qnr in ESBL-producing Enterobacteriaceae from the Philippines, and revealed a significant association between bla(CTX-M-15) and aac(6')-Ib-cr. Local epidemiological data are important for implementing appropriate antimicrobial therapy and effective infection control measures. Continuous monitoring of antimicrobial resistance genes in the Philippines will be required.     

临床分离志贺菌质粒介导喹诺酮类耐药基因的检测

目的 了解临床分离志贺菌质粒介导喹诺酮类耐药基因的种类、分布以及对抗菌药物的耐药性。方法 PCR法检测137株志贺菌的qnr、aac(6′)- Ib-cr和qepA基因,对阳性扩增产物进行测序分析并对阳性菌株做接合试验,采用琼脂倍比稀释法测定志贺菌、受体菌和接合子对喹诺酮类及其他抗菌药物的最低抑菌浓度(MIC)。PCR...     

qnrA prevalence in extended-spectrum beta-lactamase-positive Enterobacteriaceae isolates from Turkey

Quinolone resistance mostly originates from chromosomal mutations. In recent years, however, plasmid-mediated quinolone resistance has been reported in several parts of the world. Plasmid-borne qnrA, qnrB, or qnrS genes are responsible for this kind of resistance. Little is known about the diversity, type, and species range of the qnr genes in Turkey. We screened qnrA, qnrB, and qnrS genes in quinolone-resistant blood culture isolates collected from six different medical centers in Turkey which produced extended-spectrum beta-lactamases (ESBLs). A total of 78 ESBL-positive isolates were enrolled in this study. Of these, 37 (47.4%) were nalidixic-acid resistant or intermediate. qnrA was found on large plasmids isolated from five (6.4%) of the Nal(I/R) isolates. In three of these, the same plasmid also carried bla(CTX-M). Four of the qnrA-positive isolates were Klebsiella pneumoniae from Dokuz Eylul University Hospital, Izmir, and the fifth isolate was Escherichia coli from Istanbul University Hospital. Two of the isolates from Izmir were found by enterobacterial repetitive interegenic consensus sequence-PCR to be clonally related. This is the first report on the qnrA prevalence among ESBL-positive blood culture isolates collected from different regions in Turkey. According to our results, plasmid-mediated resistance is a potential problem for the spread of quinolone resistance, and this mechanism could be emerging strongly among the ESBL-positive Enterobacteriaceae in Turkey.     

Prevalence of aac(6')-Ib-cr plasmid-mediated and chromosome-encoded fluoroquinolone resistance in Enterobacteriaceae in Italy

The spread of aac(6')-Ib-cr plasmid-mediated quinolone resistance determinants was evaluated in 197 enterobacterial isolates recovered in an Italian teaching hospital. The aac(6')-Ib-cr gene was found exclusively in Escherichia coli strains. The gene was located on a plasmid which presented additional ESBL genes. Most of the clinical strains were clonally related and displayed three point mutations at the topoisomerase level which conferred high resistance to fluoroquinolones.     

Prevalence of plasmid-mediated quinolone resistance genes among ciprofloxacin-nonsusceptible Escherichia coli and Klebsiella pneumoniae isolated from blood cultures in Korea

OBJECTIVES:

To analyze the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in ciprofloxacin-nonsusceptible Escherichia coli and Klebsiella pneumoniae isolated from patients at a tertiary care hospital in Korea.

METHODS:

A total of 102 nonduplicate isolates of ciprofloxacin-intermediate or ciprofloxacin-resistant E coli (n=80) and K pneumoniae (n=22) from blood cultures were obtained. The qnr (qnrA, qnrB, qnrS), aac(6′)-Ib-cr, qepA and oqxAB genes were detected using polymerase chain reaction (PCR) and confirmed using direct sequencing. To determine whether the PMQR-positive plasmid was horizontally transferable, conjugation experiments were performed.

RESULTS:

Of the 102 isolates, 81 (79.4%) had one or more PMQR genes; these consisted of 59 (73.8%) E coli and 22 (100%) K pneumoniae isolates. The qnr genes were present in 15 isolates (14.7%): qnrB4 was detected in 10.8% and qnrS1 was detected in 3.9%. The aac(6′)-Ib-cr, qepA and oqxAB genes were detected in 77.5%, 3.9% and 10.8%, respectively. In conjugation experiments, PMQR genes were successfully transferred from seven (8.6%) isolates. The range of minimum inhibitory concentrations of ciprofloxacin for these seven transconjugants increased to 0.5 mg/L to 1 mg/L, which was 16- to 33-fold that of the recipient E coli J53 bacteria.

CONCLUSIONS:

PMQR genes were highly prevalent among ciprofloxacin-nonsusceptible E coli and K pneumoniae from blood cultures in the authors’ hospital. Therefore, it is necessary to monitor for the spread of PMQR genes of clinical isolates and to ensure careful antibiotic use in a hospital setting.     

Investigation of plasmid-mediated quinolone resistance among isolates obtained in a Turkish intensive care unit

The aim of this study was to search for three plasmid-encoded, quinolone-resistant determinants: qnrA, qnrB, and qnrS. Thus, 460 Gram-negative strains belonging to 11 different genera (clinical, 347; non-clinical, i.e., from a rectal swab, 113), of which 40% were ciprofloxacin-resistant, were recovered from patients in an intensive care unit at the Istanbul Medical Faculty, Turkey, in the years 2000 and 2006. PCR with primers specific for qnrA, qnrB, and qnrS genes and primers specific for a series of ESBL genes were used. One qnrB1 and two qnrS1 genes were identified in three ESBL-positive isolates, whereas no qnrA-positive strain was found. The qnrB1 determinant was identified in a ciprofloxacin-susceptible Enterobacter cloacae isolate that expressed CTX-M-15 beta-lactamase. Two qnrS1-determinants were found in two ciprofloxacin-susceptible E. cloacae isolates that were clonally related, but that had been isolated from different patients; both of these isolates expressed the same ESBL, CTX-M-3. This study detected the first plasmid-mediated quinolone-resistance determinants qnrB1 and qnrS1, among clinical strains obtained from patients in Turkey.     

骨科患者术后创面感染鲍曼不动杆菌对喹诺酮类抗菌药物的耐药性分析

目的了解医院骨科患者手术后创面感染的鲍曼不动杆菌的耐药情况,以指导医生合理用药,有效控制鲍曼不动杆菌耐药性的进一步发展,预防和减少医院感染的发生。方法从骨科患者手术后创面感染标本分离鲍曼不动杆菌28株,作gyrA基因测序,并进行BLASTn比对;通过测定最小抑菌浓度(minimum inhibitory concentration,MIC)进行药敏试验,测定鲍曼不动杆菌的耐药性;选取经纯培养的鲍曼不动杆菌菌落置入含蛋白酶K溶液的离心管内,分别进行水浴,再离心,留取上清液,以此为模板PCR扩增与喹诺酮类抗菌药物耐药性相关的gyrA、qepA、qnrS、qnrA、qnrB和aac(6)-Ib基因,使用Chromas分析软件进行测序。结果鲍曼不动杆菌对诺氟沙星、氧氟沙星、培氟沙星、依诺沙星、环丙沙星、司帕沙星、左氧氟沙星、加替沙星、莫西沙星的耐药率分别为:96.43%、96.43%、96.43%、89.29%、85.71%、85.71%、82.14%、78.57%和78.57%。PCR检测28株鲍曼不动杆菌gyrA基因100%阳性,即都发生了gyrA基因突变,而其他相关基因检测均阴性。基因测序看出,其83位发生突变,即由TCA转变为TTA。结论本组分离骨科患者手术创面感染的鲍曼不动杆菌对喹诺酮类抗菌药物的耐药情况严重,其中对诺氟沙星、氧氟沙星、培氟沙星等的耐药率均在90%以上。临床抗感染治疗应根据耐药结果进行用药,并控制喹诺酮类抗菌药物的使用。     

广西生鲜畜禽产品源致病性大肠杆菌血清型、耐药性及耐药基因调查

目的 了解广西生鲜畜禽产品中致病性大肠杆菌血清型分布、耐药性以及β-内酰胺酶bla_TEM、bla_CTX-M基因和氟喹诺酮类抗生素耐药基因qnrA、oqxA、oqxB、aac(6')-Ib-cr的流行情况。方法 采用玻片凝集法对2015—2016年间分离自广西生鲜畜禽产品中的249株致病性大肠杆菌进行“O”抗原血清型鉴定;K-B纸片法对已定型菌株进行24种常见抗生素的敏感性试验;PCR方法检测bla_TEM、bla_CTX-M、qnrA、oqxA、oqxB、aac(6')-Ib-cr。结果 249株致病性大肠杆菌中136株可定型、96株未定型、17株自凝,分别占鉴定菌株的54.6%、38.6%、6.8%;136株已定型菌株分属25个血清型,以O8 (19.85%) 、O86 (8.82%) 、O6 (6.62%)、O28(6.62%) 、O124 (6.62%)为主要优势血清型;136株已定型菌株对24种抗生素均产生不同程度的耐药,耐药率从16.18%到100%,且全部为多重耐药,主要集中在12~18重耐药,共占多重耐药的72.06%;136株已定型菌株对6种耐药基因的检出率为qnrA 91.18%(124/136)、oqxA 80.88%(110/136)、oqxB 50.00%(68/136)、aac(6')-Ib-cr 35.29%(48/136)、bla_TEM 100.00%(136/136)、bla_CTX-M 23.53%(32/136)。结论 广西生鲜畜禽产品源致病性大肠杆菌O抗原血清型呈多样性分布,耐药情况严重,临床日益严重的耐药现象与耐药基因的普遍存在有重要的关系。     

Mechanisms of reduced susceptibility to ciprofloxacin in Escherichia coli isolates from Canadian hospitals

OBJECTIVE:

To determine whether plasmid-mediated quinolone resistance (PMQR) determinants play a role in the increasing resistance to fluoroquinolones among Escherichia coli isolates in Canadian hospitals, and to determine the mechanisms of reduced susceptibility to ciprofloxacin in a recent collection of 190 clinical E coli isolates.

METHODS:

E coli isolates (n=1702) were collected as part of the 2007 Canadian Hospital Ward Antibiotic Resistance Surveillance (CANWARD) study. Antimicrobial susceptibility testing was performed by Clinical and Laboratory Standards Institute (CLSI) broth microdilution. Using a representative subset of isolates (n=190), the mechanisms of reduced susceptibility to ciprofloxacin were detected by polymerase chain reaction and sequencing of the quinolone resistance-determining regions (QRDR) of chromosomal gyrA and parC genes, and by polymerase chain reaction for the PMQR genes: qnr, aac(6′) Ib-cr and qepA.

RESULTS:

2.1% and 1.1% of E coli harboured aac(6′)Ib-cr and qnrB, respectively. Single amino acid substitutions in the QRDR of gyrA were observed among isolates with ciprofloxacin minimum inhibitory concentrations as low as 0.12 μg/mL. As the ciprofloxacin minimum inhibitory concentration increased to 1 μg/mL (which is still considered to be susceptible by the CLSI), the vast majority of isolates demonstrated both gyrA and parC mutations.

CONCLUSION:

PMQR determinants and QRDR mutants among clinical E coli isolates with reduced susceptibility to ciprofloxacin demonstrates the need for increased surveillance and the need to re-evaluate the current CLSI breakpoints to prevent further development of fluoroquinolone resistance.     

大肠埃希菌药敏分析及qnr基因分布情况研究

目的了解衡水地区大肠埃希菌的药敏情况以及qnr基因的存在情况。方法采用肉汤稀释法测15种抗菌药物最低抑菌浓度（MIC）并计算其MIC50和MIC90;采用聚合酶链反应（PCR）检测qnr基因。结果15种抗菌药物中仅亚胺培南、哌拉西林／他唑巴坦和头孢哌酮／舒巴坦对大肠埃希菌敏感,245例大肠埃希菌中检出5株存在qnrB基因,占2．O％,1株存在qnrS基因,占0．4％。结论我院检出的大肠埃希菌存在多重耐药。少数菌株中,存在qnrB和qnrS基因,临床应加强监测。     

福氏志贺菌中质粒介导喹诺酮类耐药qnr基因的检测

目的 了解福氏志贺菌中qnr基因的分布.方法 采用PCR法检测26株福氏志贺菌的qnr基因并对阳性扩增产物进行测序分析,采用琼脂稀释法测定qnr基因阳性菌株对多种抗菌药物的敏感性,采用随机引物PCR法(ERIC-PCR)进行qnr基因阳性菌株同源性检测.结果 26株福氏志贺菌中,qnrAl、qnrS1和qnrS2基因的阳性率分别为30.8%、11.5%和3.8%;qnr基因阳性菌株对氯霉素、奈啶酸耐药.对诺氟沙星、哌拉西林耐药或中介;部分菌株对头孢唑啉、阿米卡星、第二、三代头孢菌素耐药.ERIC-PCR电泳图谱型显示.2株qnrAl基因阳性菌株属于同一谱型.结论 福氏志贺菌中存在qnr基因阳性菌株,部分菌株间存在克隆传播现象,临床应加强检测和监测.     

Determinants of quinolone resistance in Escherichia coli causing community-acquired urinary tract infection in Bejaia,Algeria

Objective:To investigate the mechanisms of quinolone resistance and the association with other resistance markers among Esherichia coli(E.coli) strains isolated from outpatient with urinary tract infection in north of Algeria.Methods:A total of 30 nalidixic acid-resistant E.coli isolates from outpatient with urinary tract infections from January 2010 to April 2011 in north of Algeria(Bejaia) were studied.Antimicrobial susceptibility was determined by disc diffusion assay,minimal inhibitory concentrations(MIC) of quinolone were determined by microdilution.Mutations in the Quinolone Resistance-Determining Region(QRDR) of gyra and parC genes and screening for qnr(A,B and S) and bla genes were done by PCK and UNA sequencing.Results:Most of the E.coli isolates(56.66%) were shown to carry mutations in gyrA and parC,igyra:Ser83Leu + Asp87Asn and parC:Ser80Iler.While.16.66 had only an alteration in gyrA:Ser83Leu.One isolate produced qnrB-like and two qnrS-like.Four isolates were CTXM-15 producers associated with TEM-1 producing in one case.Co-expression of bla_(LTV,M)_(15) and qnrB was determined in one E.coli isolate.Conclusions:Our findings suggested the community emergence of gyrA and parC alterations and Qnr determinants that contributed to the development and spread of fluoroquinolone resistance in Algerian E.coli isolates.     

The worldwide emergence of plasmid-mediated quinolone resistance

Fluoroquinolone resistance is emerging in gram-negative pathogens worldwide. The traditional understanding that quinolone resistance is acquired only through mutation and transmitted only vertically does not entirely account for the relative ease with which resistance develops in exquisitely susceptible organisms, or for the very strong association between resistance to quinolones and to other agents. The recent discovery of plasmid-mediated horizontally transferable genes encoding quinolone resistance might shed light on these phenomena. The Qnr proteins, capable of protecting DNA gyrase from quinolones, have homologues in water-dwelling bacteria, and seem to have been in circulation for some time, having achieved global distribution in a variety of plasmid environments and bacterial genera. AAC(6')-Ib-cr, a variant aminoglycoside acetyltransferase capable of modifying ciprofloxacin and reducing its activity, seems to have emerged more recently, but might be even more prevalent than the Qnr proteins. Both mechanisms provide low-level quinolone resistance that facilitates the emergence of higher-level resistance in the presence of quinolones at therapeutic levels. Much remains to be understood about these genes, but their insidious promotion of substantial resistance, their horizontal spread, and their co-selection with other resistance elements indicate that a more cautious approach to quinolone use and a reconsideration of clinical breakpoints are needed.     

48株鲍曼不动杆菌氨基糖苷类抗生素耐药基因检测

目的了解鲍曼不动杆菌氨基糖苷类抗生素耐药基因分布情况。方法收集蚌埠医学院第一附属医院2015年1月至12月临床分离的48株泛耐药鲍曼不动杆菌,VITEK 2Compact进行鉴定和药敏实验。PCR法检测12个氨基糖苷类修饰酶基因和3个甲基化酶基因以及外排泵基因adeB。结果在实验的16个基因中,共检出4种氨基糖苷类抗生素耐药基因aac(6′)-Ib、armA、adeB和ant(3″)-Ia,其中aac(6′)-Ib检出率为39.6%(19/48),armA基因检出率为89.6%(43/48),adeB检出率89.6%(43/48),ant(3″)-Ia检出率为10.4%(5/48),其余基因均未检出;存在两种以上耐药基因的共39株,检出率为81.3%(38/48)。结论 aac(6′)-Ib、armA基因以及外排泵adeB是介导我院鲍曼不动杆菌氨基糖苷类抗生素耐药的主要基因。     

下呼吸道感染患者铜绿假单胞菌分离株氨基糖苷类耐药相关基因分析

目的探讨分离自下呼吸道感染患者的氨基糖苷类耐药铜绿假单胞菌的耐药机制。方法从下呼吸道感染患者痰液中分离出52株对氨基糖苷类耐药的铜绿假单胞菌,PCR法检测6种氨基糖苷类修饰酶(AMEs)基因,并检测其中泛耐药菌的6种16S rRNA甲基化酶基因(以下简称甲基化酶基因)。对阳性产物测序加以证实。结果 52株铜绿假单胞菌中检出4种AMEs基因[aac(3)-Ⅱ、aac(6’)-Ⅰb、aac(6’)-Ⅱ和ant(2″)-Ⅰ],AMEs基因总检出率为92.3%。泛耐药菌中检出1种甲基化酶基因(rmtB)。16株高水平泛耐药菌中rmtB基因的检出率为81.3%。结论分离自下呼吸道感染患者的氨基糖苷类耐药铜绿假单胞菌中AMEs基因携带率高,其对氨基糖苷类耐药与aac(3)-Ⅱ、aac(6’)-Ⅰb、aac(6’)-Ⅱ和ant(2″)-Ⅰ有关;对氨基糖苷类高水平泛耐药主要与甲基化酶基因rmtB有关。     

1株携带质粒介导喹诺酮耐药基因qnrS1和qepA1的多耐药沙门菌的基因特点分析

目的 分析一株多重耐药沙门菌SM846的遗传背景,研究其对喹诺酮耐药的机制。方法 测定SM846对14种药物的最小抑菌浓度(minimal inhibitoryconcentration,MIC)。用三代测序技术对菌株进行全基因组测序,根据耐药数据库注释SM846序列中的耐药基因。使用NCBI的BLAST工具搜索与耐药质粒相似的序列,并进行生物信息学分析。结果 SM846对14种测试抗生素中的12种表现出耐药,包括喹诺酮类抗生素萘啶酸和环丙沙星。SM846包含1条染色体和1条质粒。染色体序列不含可导致耐药的基因和突变,质粒携带13个耐药基因,包括喹诺酮类耐药基因qepA1和qnrS1。qepA1和qnrS1位于质粒内部的可移动原件I类整合子上。13条相似质粒的分析表明中国分离的此型别的质粒耐药性强于美国和加拿大分离的。结论 QnrS1和qepA1基因通过IS6和可移动元件整合到质粒的I类整合子上,说明SM846可能迫于抗生素压力通过获得耐药基因来快速适应环境。中国分离菌株的耐药性强,地区间的耐药情况差异,尤其是与不发达国家之间的差异提示我们应当继续监测各地区的耐药表现型,以制定本地的耐药控制策略。     

Presence of quinolone resistance to qnrB1 genes and blaOXA-48 carbapenemase in clinical isolates of Klebsiella pneumoniae in Spain

A study is presented on the presence of quinolone resistance qnrB1 genes in clinical isolates belonging to the largest series of infections caused by OXA-48-producing Klebsiella pneumoniae in a single-centre outbreak in Spain. Evidence is also provided, according to in vitro results, that there is a possibility of co-transfer of plasmid harbouring bla_OXA-48 with an other plasmid harbouring qnrB1 in presence of low antibiotic concentrations of fluoroquinolones, showing the risk of multi-resistance screening.     

医院获得性鲍曼不动杆菌肺炎六例微生物学及临床观察

目的探讨医院获得性鲍曼不动杆菌肺炎患者临床微生物学特点和治疗转归。方法回顾性调查2005年1～8月白求恩国际和平医院经分子生物学方法证实的6例医院获得性产PER-1型超广谱13内酰胺酶（ESBL）鲍曼不动杆菌肺炎患者的临床资料。用脉冲场凝胶电泳检测6株鲍曼不动杆菌的同源性，聚合酶链反应分析相关耐药基因。结果6株鲍曼不动杆菌中5株仅对亚胺培南敏感，4株对美罗培南敏感。脉冲场凝胶电泳将其分为A1型2株，A2～如型各1株，携有β内酰胺酶blaPER-1基因，同时blaTEM-1型基因、耐消毒剂磺胺药物基因（qacEΔ1-sull）和1类整合子酶基因（intll）阳性，其中3株氨基糖苷类修饰酶基因aac（3）-I、aac（6’）-I同时阳性，2株aac（3）-I、ant（3”）-I同时阳性，1株aac（3）-I单独阳性。6例患者均患有严重的基础疾病，使用过呼吸机；检出鲍曼不动杆菌前15d内应用过广谱抗菌药物；经使用碳青霉烯类和（或）头孢哌酮／舒巴坦抗感染治疗，3例临床好转，3例死亡。结论6株产PER-1型ESBL鲍曼不动杆菌具有高度同源性，耐药基因复杂，其所引起的医院获得性肺炎临床预后差。     

Molecular diversity of class 1 integrons in human isolates of Aeromonas spp. from southern Taiwan

This work studies antimicrobial resistance and class 1 integrons of Aeromonas spp. in human isolates from southern Taiwan. PCR amplification and DNA sequence analyses were performed to characterize the gene cassette regions of the class 1 integron in 204 isolates of Aeromonas hydrophila, 36 isolates of A. sobria, 23 isolates of A. veronii, and 4 isolates of A. caviae. By using Southern hybridization with an intI1 probe to determine the presence of class 1 integrons in the 9 isolates of Aeromonas spp. harboring plasmid DNA, only 2 isolates, one A. veronii AV69 harboring 176-kb plasmid DNA, and one A. hydrophila AH207 harboring 149-kb plasmid DNA were identified. A conjugation experiment was carried out with 2 isolates of A. veronii AV69 and A. hydrophila AH207. Only one transconjugant of Escherichia coli AH207, containing 149-kb plasmids obtained from A. hydrophila AH207, was identified. ERIC-PCR analysis was performed to analyze the genetic relatedness in all isolates of Aeromonas spp. that carry class 1 integrons. The results of cluster analysis in this experiment revealed that none of these isolates were clonal, which may indicate that they were not related to the outbreak. Among the 267 isolates tested, class 1 integrons were detected in 37 isolates (13.9%) of Aeromonas spp. from humans. No class 2 or class 3 integrons were detected in this study. Gene cassette structures were identified in 30 (81.0%) of 37 isolates of Aeromonas spp. containing class 1 integrons. The gene cassette of dfrA12-orfF-aadA2 was the most prevalent in the gene cassette array (16.0%), followed by arr3-aacA4 (13.3%) and dfr2d-catB3-aadA1 (10.0%). Four novel arrays of gene cassettes were also identified, namely, dfr2d-catB3-aadA1, aadA1-aac(6')-II, aadA4a, and aac(6')-II-blaOXA-21-catB3. This is the first report of Aeromonas spp. isolates from humans.