Identification and genetic characterization of metallo-beta-lactamase-producing strains of Pseudomonas aeruginosa in Tehran, Iran

Metallo-beta-lactamases (MBLs) are being reported with increasing frequency worldwide. The aim of this study was to investigate the prevalence of blalMP-1, blaVIM-1,2 and blaSPM-1 genes encoding metallo-beta-lactamases (MBLs) among a collection of Pseudomonas aeruginosa strains isolated from patients at different hospitals in Tehran and to trace the disseminated clones at these hospitals by pulsed field gel electrophoresis (PFGE). Susceptibility of 610 P aeruginosa to 14 different antibiotics was determined using disc diffusion method. Isolates showing resistance to imipenem and ceftazidime were subjected to micro broth dilution assay to determine their MIC values. The blaIMP-1, blaVIM-1, blaVIM-2, and blaSPM-1, genes were amplified by PCR. Isolates containing blaVIM-1 were analyzed by PFGE. Sixty-eight isolates were resistant to imipenem (MIC > or = 4 microg/ml) of which 16 isolates carried blaVIM-1 gene using PCR assay. No other MBL genes were detected in this study. Three different unrelated patterns were found for isolates containing blaVIM-1 gene by PFGE of which pattern A was predominant. All isolates were susceptible to colistin and polymixin B. blaVIM-1 was the main gene encoding MBL among the isolates of P aeruginosa in our study. Clonal spread of isolates containing blaVIM-1 had occurred at Tehran hospitals. However, heterogeneous clones also were involved in the outbreaks.     

碳青霉烯类耐药肺炎克雷伯菌基因型检测及同源性分析

目的了解福建医科大学附属第一医院耐碳青霉烯类肺炎克雷伯菌（KPC）的耐药基因分型及同源性分布情况。方法收集临床分离的29株KPC,改良Hodge试验检测碳青霉烯酶表型。PCR检测碳青霉烯酶blaKPC、blaIMP-1、blaVIM-1、blaOXA-48及blaNDM-基因;阳性结果进行DNA测序,并进行BLAST比对确定其基因型。采用肠杆菌科基因间重复序列（ERIC—PCR）对KPC进行同源性分析。结果29株KPC中Hodge试验阳性27株,阳性率为93．1％（27／29）。PCR扩增和DNA测序显示28株为blaKPC-2,株为blaIMP-1,未检出blaVIM-2、blaOXA-48和blaNDM-1基因。同源性分析发现KPC主要存在两种型别：28株A1和1株A2。结论blaKPC-2型碳青霉烯酶是该院KPC的主要型别,A1型已在该院流行,应加强院感监测和预防。ERIC—PCR是一种简便、快捷的基因分型技术,适合同源性的初步分型筛查。     

Multidrug-resistant Providencia isolates carrying blaPER-1, blaVIM-2, and armA

During May to July 2004, three strains of Providencia spp. with multidrug-resistance (MDR) were isolated from urinary specimen of three patients hospitalized with a same hospital room. By PCR analysis, all three strains have been found to carry both VIM-2 type metallo-beta-lactamase gene and PER-1 type extendedspectrum beta-lactamase gene. One out of three strains carried additional resistance gene, armA, 16S rRNA methylase gene responsible for high level resistance to aminoglycosides. To our knowledge, this is the first report on the identification of Providencia spp. simultaneously carrying blaVIM-2, blaPER-1, and armA genes.     

对一株铜绿假单胞菌22种耐药基因的研究

目的研究铜绿假单胞菌多重耐药情况和相关机制。方法采用聚合酶链反应（PCR）法对一株多重耐药铜绿假单胞菌进行β-内酰胺酶基因、氨基糖苷类修饰酶（AMEs）基因、喹诺酮类耐药基因、耐消毒剂基因（qacE△1-sul1）和整合酶基因检测,并对VIM基因进行了测序。结果PCR扩增结果显示该菌株aac（6′）-Ⅰb、blaCARB、gyrA、oprD2、ant（2″）-Ⅰ、qacE△1-sul1、blaIMP-I、blaTEM、blaVEB、aac（3）-Ⅱ、ant（3″）-Ⅰ、intⅠ1、blaVIM基因均为阳性,而aac（3）-Ⅰ、aac（6′）-Ⅱ、blaGES、blaGIM、blaOXA-10群、blaPER、blaSPM、blaSHV、blaDHA基因均为阴性,VIM基因扩增产物测序后经BLAST同源性分析表明为VIM-2型。结论铜绿假单胞菌存在多重耐药基因。管壁涂有季胺类、双胍类消毒剂和磺胺的II代导管的抑菌效果需重新评价。     

Molecular characterization of Pseudomonas aeruginosa isolates resistant to all antimicrobial agents, but susceptible to colistin, in Daegu, Korea

Multi-drug resistant Pseudomonas aeruginosa has been implicated in a variety of serious therapeutic problems in clinical environments. Among the 968 P. aeruginosa isolates obtained from two hospitals in Daegu, Korea, we acquired 17 isolates that were resistant to all available tested antimicrobial agents, with the exception of colistin (colistin-only sensitive). We characterized the antimicrobial susceptibilities, metallo-beta-lactamases, and epidemiological relatedness among the colistin-only sensitive P. aeruginosa isolates. All colistin-only sensitive isolates were positive in the modified Hodge test and imipenem-EDTA synergy test, thereby indicating the production of metallo-beta-lactamases. 11 isolates from the secondary hospital and six isolates from the tertiary teaching hospital harbored blaVIM-2 and blaIMP-1, respectively. The pulsed-field gel electrophoretic analysis of the SpeI-digested DNA from P. aeruginosa isolates indicated that two different clones of colistin-only sensitive P. aeruginosa originated from each hospital, and had spread within the hospital environment. Overall, colistin-only sensitive P. aeruginosa was detected in Korea for the first time, but no pan-drug resistant bacteria were identified. Nationwide surveillance is required in order to monitor the emergence of colistin-only sensitive or pan-drug resistant bacteria.     

同时携带blaKPC和blaOXA-10基因的亚胺培南耐药阴沟肠杆菌的研究

目的研究宁波地区临床分离的亚胺培南耐药的阴沟肠杆菌所携带的β-内酰胺酶耐药基因,以确定本地区亚胺培南耐药的阴沟肠杆菌的主要基因型别及其流行情况,指导临床合理用药。方法收集2010年1月1日至2011年4月30日临床分离的阴沟肠杆菌,筛选出亚胺培南耐药菌株用PCR法进行blaOXA-10、blaOXA-2、blaOXA-1、blaKPC、blaIMP、blaVIM、blaNDM-1、blaIMI-1、blaSME、blaSHV-38等多种基因的同时检测。结果共收集到阴沟肠杆菌311株,筛选出对亚胺培南耐药的6株(编号为37号、60号、89号、90号、92号、120号),占1.92%;PCR检测结果显示60号、89号、92号、120号菌株同时产blaKPC型碳青霉烯酶和OXA-10型广谱β-内酰胺酶。结论首次在亚胺培南耐药的阴沟肠杆菌中发现了blaKPC与blaOXA-10同时存在的菌株;亚胺培南耐药的阴沟肠杆菌其耐药机制复杂,且多种耐药机制共存,亟待我们积极深入的探索研究。     

Prevalence and genotypic relatedness of carbapenem resistance among multidrug-resistant P. aeruginosa in tertiary hospitals across Thailand

ABSTRACT: BACKGROUND: Increased infection caused by multidrug resistant (MDR) Pseudomonas aeruginosa has raised awareness of the resistance situation worldwide. Carbapenem resistance among MDR (CR-MDR) P. aeruginosa has become a serious life-threatening problem due to the limited therapeutic options. Therefore, the objectives of this study were to determine the prevalence, the antibiotic susceptibility patterns and the relatedness of CR-MDR P. aeruginosa in tertiary hospitals across Thailand. METHODS: MDR P. aeruginosa from eight tertiary hospitals across Thailand were collected from 2007--2009. Susceptibility of P. aeruginosa clinical isolates was determined according to the Clinical and Laboratory Standards Institute guideline. Selected CR-MDR P. aeruginosa isolates were genetically analyzed by pulsed-field gel electrophoresis. RESULTS: About 261 clinical isolates were identified as MDR P. aeruginosa and approximately 71.65% were found to be CR-MDR P. aeruginosa. The result showed that the meropenem resistance rate was the highest reaching over 50% in every hospitals. Additionally, the type of hospitals was a major factor affecting the resistance rate, as demonstrated by significantly higher CR-MDR rates among university and regional hospitals. The fingerprinting map identified 107 clones with at least 95% similarity. Only 4 clones were detected in more than one hospital. CONCLUSIONS: Although the antibiotic resistance rate was high, the spreading of CR-MDR was found locally. Specific strains of CR-MDR did not commonly spread from one hospital to another. Importantly, clonal dissemination ratio indicated limited intra-hospital transmission in Thailand.     

PER-1 is still widespread in Turkish hospitals among Pseudomonas aeruginosa and Acinetobacter spp

PER-1 type beta-lactamases were screened among ceftazidime-resistant clinical isolates of Acinetobacter spp. and Pseudomonas aeruginosa. A total of 176 non-repetitive isolates (84 Acinetobacter spp. and 92 P. aeruginosa) were collected during a three month surveillance period. Isolates were obtained from seven intensive care units of seven university hospitals. All strains were screened for bla(PER-1) alleles by PCR. Of the strains, 31% and 55.4% of Acinetobacter spp. and P. aeruginosa were positive for bla(PER-1) type genes, respectively.     

Outbreaks of imipenem-resistant Acinetobacter baumannii producing carbapenemases in Korea

Among 53 Acinetobacter baumannii isolates collected in 2004, nine imipenem-resistant isolates were obtained from clinical specimens taken from patients hospitalized in Busan, Korea. Nine carbapenemase-producing isolates were further investigated in order to determine the mechanisms underlying resistance. These isolates were then analyzed via antibiotic susceptibility testing, microbiological tests of carbapenemase activity, pI determination, transconjugation test, enterobacterial repetitive consensus (ERIC)-PCR, and DNA sequencing. One outbreak involved seven cases of infection by A. baumannii producing OXA-23 beta-lactamase, and was found to have been caused by a single ERIC-PCR clone. During the study period, the other outbreak involved two cases of infection by A. baumannii producing IMP-1 beta-lactamase. The two clones, one from each of the outbreaks, were characterized via a modified cloverleaf synergy test and an EDTA-disk synergy test. The isoelectric focusing of the crude bacterial extracts detected nitrocefin-positive bands with pI values of 6.65 (OXA-23) and 9.0 (IMP-1). The PCR amplification and characterization of the amplicons via direct sequencing showed that the clonal isolates harbored blaIMP-1 or blaOXA-23 determinants. The two clones were characterized by a multidrug resistance phenotype that remained unaltered throughout the outbreak. This resistance encompassed penicillins, extended-spectrum cephalosporins, carbapenems, monobactams, and aminoglycosides. These results appear to show that the imipenem resistance observed among nine Korean A. baumannii isolates could be attributed to the spread of an IMP-1- or OXA-23-producing clone. Our microbiological test of carbapenemase activity is a simple method for the screening of clinical isolates producing class D carbapenemase and/or class B metallo-beta-lactamase, in order both to determine their clinical impact and to prevent further spread.     

铜绿假单胞菌氨基糖苷16SrRNA甲基化酶基因分析

目的调查215株湖州地区临床分离铜绿假单胞菌对氨基糖苷类抗生素的耐药性和16S rRNA甲基化酶基因分布情况。方法收集2011年1月至2012年12月湖州地区临床分离铜绿假单胞菌215株,琼脂稀释法测定5种氨基糖苷类抗菌药物（庆大霉素、阿米卡星、妥布霉素、伊帕米星、奈替米星）的MIC值;PCR检测armA、rmtA、rmtB、rmtC、rmtD和npmA六种氨基糖苷类16S rRN甲基化酶基因,序列分析明确基因型。测定产16S rRNA甲基化酶菌株对常见抗菌的敏感性,并检测碳青霉烯耐药株产碳青霉烯酶情况。结果铜绿假单胞菌对异帕米星敏感率最高为81.4%,对5种氨基糖苷类抗生素全部耐药的22株菌株中,17株检出armA基因;未发现其他16S rRNA甲基化酶基因阳性菌株。17株armA阳性菌株对碳青霉烯类抗生素耐药5株（耐药率为29.4%）,对头孢他啶、头孢吡肟、哌拉西林/他唑巴坦、环丙沙星耐药率均超过40%。5株碳青霉烯耐药菌株中检测到2株产VIM-2型金属碳青霉烯酶。结论铜绿假单胞菌对氨基糖苷类抗生素耐药率高,检测到16S rRNA甲基化酶基因armA。产16S rRNA甲基化酶铜绿假单胞菌耐药性强,部分菌株同时产金属碳青霉烯酶,给临床抗感染治疗及院内感染控制带来挑战。     

Occurrence of qnr-positive clinical isolates in Klebsiella pneumoniae producing ESBL or AmpC-type beta-lactamase from five pediatric hospitals in China.

The plasmid-mediated quinolone resistance qnr genes in clinical isolates in adults have been described in different countries; however, the frequency of their occurrence has not been detected in pediatric patients. A total of 410 clinical isolates of Klebsiella pneumoniae, identified as producers of an extended-spectrum beta-lactamase (ESBL), or AmpC beta-lactamase, were collected from five children's hospitals in China during 2005-2006. The isolates were screened for the presence of the qnrA, qnrB, and qnrS genes, and then the harboring qnr gene isolates were detected for a bla gene coding for the TEM, SHV, CTX-M, and plasmid-mediated ampC gene by a PCR experiment. Ninety-two isolates (22.7%) were positive for the qnr gene, including 10 of qnrA (2.4%), 25 of qnrB (6.1%), and 62 of qnrS (15.1%). Eighty-one of the 92 (88.0%) qnr-positive isolates carried at least one bla gene for TEM, SHV, CTX-M, or DHA-1. The ciprofloxacin resistance increased 16-256-fold and oflaxacin resistance increased 2-32-fold in transconjugants, respectively. These results indicated that the plasmid-mediated qnr quinolone resistance gene was qnrS, followed by qnrB and qnrA. Most of the isolates also carried a bla gene coding ESBL or ampC gene coding DHA-1 among Klebsiella pneumoniae isolated from Chinese pediatric patients.     

Phenotypic and Molecular Characterization of Extended-Spectrum Beta-Lactamase-Producing Escherichia coli in Bangladesh

Background

Resistance to cephalosporins in Enterobacteriaceae is mainly due to the production of extended-spectrum beta-lactamase (ESBL). Little is known about ESBL-producing bacteria in Bangladesh. Therefore, the study presents results of phenotypic and molecular characterization of ESBL-producing Escherichia coli from hospitals in Bangladesh.

Methods

A total of 339 E. coli isolated from patients with urinary tract and wound infections attending three different medical hospitals in urban and rural areas of Bangladesh between 2003–2007 were screened for ESBL-production by the double disk diffusion test. Isolates with ESBL-phenotype were further characterized by antibiotic susceptibility testing, PCR and sequencing of different β-lactamase and virulence genes, serotyping, and XbaI-macrorestriction followed by pulsed-field gel electrophoresis (PFGE).

Results

We identified 40 E. coli with ESBL phenotype. These isolates were resistant to ceftriaxone, ceftazidime, cefotaxime, aztreonam, cefepime, and nalidixic acid but remained susceptible to imipenem. All but one isolate were additionally resistant to ciprofloxacin, and 3 isolates were resistant to cefoxitin. ESBL genes of blaCTX-M-1-group were detected in all isolates; blaTEM-type and blaOXA-1-type genes were detected in 33 (82.5%) and 19 (47.5%) isolates, respectively. Virulence genes that are present in diarrhoeagenic E. coli were not found. Class-1 integron was present in 20 (50%) isolates. All the ESBL-producing E. coli isolates harbored plasmids ranging between 1.1 and 120 MDa. PFGE-typing revealed 26 different pulsotypes, but identical pulsotype showed 6 isolates of serotype O25:H4.

Conclusion

The prevalence of multidrug-resistant ESBL-producing E. coli isolates appears to be high and the majority of the isolates were positive for bla _CTX-M. Although there was genetic heterogeneity among isolates, presence of a cluster of isolates belonging to serotype O25:H4 indicates dissemination of the pandemic uropathogenic E. coli clone in Bangladesh.     

Susceptibility, phenotypes of resistance, and extended-spectrum β-lactamases in Acinetobacter baumannii strains

Acinetobacter baumannii plays an increasing role in the pathogenesis of infections in humans. The bacilli are frequently isolated from patients treated in intensive care units. A growing resistance to antibiotics is leading to the emergence of strains that are multidrug-resistant and resistant to all available agents. The objective of this study was to assess susceptibility to antibiotics and to determine the presence and current level of the extended-spectrum β-lactamases (ESBLs) and attempt to isolate the Acinetobacter baumannii strain carrying the blaPER gene. A total of 51 strains of A. baumannii identified by phenotypic features were examined. That the strains belonged to the species was confirmed by the presence of the blaOXA-51-like; gene. A broth microdilution method was used for antibacterial susceptibility testing. The occurrence of ESBLs was determined using phenotypic double-disk synergy tests. The PCR technique was used to confirm the presence of the blaPER-1; gene encoding ESBL. The most active antibiotics were meropenem, cefepime and ampicillin/sulbactam, with susceptibility shown by 76.5%, 60.8% and 56.9% of the strains, respectively. The strains exhibited the highest resistance (> 75%) to piperacillin, tetracycline, ciprofloxacin and cefotaxime. Phenotypic tests revealed ESBL mechanism of resistance in approximately 20% of Acinetobacter baumannii isolates. However, the PCR technique did not confirm the presence of the blaPER-1; gene in any of the Acinetobacter baumannii strains examined in our hospital. Acinetobacter baumannii strains demonstrate considerable resistance to many groups of antibiotics. Our findings indicate the involvement of enzymes belonging to families other than PER β-lactamase in resistance to β-lactams in A. baumannii.     

2007-2010四年间鲍曼不动杆菌耐药性变迁及对亚胺培南耐药的机制研究

目的研究2007-2010四年间中山大学附属第一医院临床分离的鲍曼不动杆菌的耐药性迁移情况和耐亚胺培南的鲍曼不动杆菌(IRAB)的耐药机制,为临床抗感染治疗提供依据。方法采用VITEK 2型全自动微生物检测系统对细菌进行鉴定及药敏分析;用PCR方法检测碳青霉烯酶基因blaOXA-51、blaOXA-23、blaOXA-24和blaOXA-58。结果 2007-2010四年间分离鲍曼不动杆菌811株,耐药率逐年上升,其对头孢哌酮/舒巴坦、美罗培南、头孢吡肟、亚胺培南和哌拉西林/他唑巴坦的耐药率上升明显,如对亚胺培南的耐药率自2007-2010年分别为13.1%、26.0%、44.3%和59.5%。811株鲍曼不动杆菌中IRAB有311株,IRAB对抗生素的耐药率明显升高,但四年间的耐药率变化并不明显。对IRAB敏感的抗生素以阿米卡星为首,其次为头孢哌酮/舒巴坦,但头孢哌酮/舒巴坦的敏感率逐年下降。从311株IRAB中随机抽取140株,检出blaOXA-51基因阳性125株(89.3%),blaOXA-23基因阳性29株(20.7%),blaOXA-24基因阳性3株(2.14%),blaOXA-58基因阳性22株(15.7%)。结论鲍曼不动杆菌的耐药性逐年升高,以阿米卡星与头孢哌酮/舒巴坦联合应用为有效的治疗方法,产碳青霉烯酶是IRAB的主要耐药机制。     

A set of novel multiplex Taqman real-time PCRs for the detection of diarrhoeagenic Escherichia coli and its use in determining the prevalence of EPEC and EAEC in a university hospital

Background

Escherichia coli isolates of equine faecal origin were investigated for antibiotic resistance, resistance genes and their ability to perform horizontal transfer.

Methods

In total, 264 faecal samples were collected from 138 horses in hospital and community livery premises in northwest England, yielding 296 resistant E. coli isolates. Isolates were tested for susceptibility to antimicrobial drugs by disc diffusion and agar dilution methods in order to determine minimum inhibitory concentrations (MIC). PCR amplification was used to detect genes conferring resistance to: ampicillin (TEM and SHV beta-lactamase), chloramphenicol (catI, catII, catIII and cml), tetracycline (tetA, tetB, tetC, tetD, tet E and tetG), and trimethoprim (dfrA1, dfrA9, dfrA12, dfrA13, dfr7, and dfr17).

Results

The proportion of antibiotic resistant isolates, and multidrug resistant isolates (MDR) was significantly higher in hospital samples compared to livery samples (MDR: 48% of hospital isolates; 12% of livery isolates, p < 0.001). Resistance to ciprofloxacin and florfenicol were identified mostly within the MDR phenotypes. Resistance genes included dfr, TEM beta-lactamase, tet and cat, conferring resistance to trimethoprim, ampicillin, tetracycline and chloramphenicol, respectively. Within each antimicrobial resistance group, these genes occurred at frequencies of 93% (260/279), 91%, 86.8% and 73.5%, respectively; with 115/296 (38.8%) found to be MDR isolates. Conjugation experiments were performed on selected isolates and MDR phenotypes were readily transferred.

Conclusions

Our findings demonstrate that E. coli of equine faecal origin are commonly resistant to antibiotics used in human and veterinary medicine. Furthermore, our results suggest that most antibiotic resistance observed in equine E. coli is encoded by well-known and well-characterized resistant genes common to E. coli from man and domestic animals. These data support the ongoing concern about antimicrobial resistance, MDR, antimicrobial use in veterinary medicine and the zoonotic risk that horses could potentially pose to public health.     

The presence of blaIMP genes on plasmids DNA isolated from multidrug-resistant Pseudomonas aeruginosa strains at University Hospital in Bialystok (Poland)--first report

Resistance to carbapenems is emerging, and it is a great problem to therapeutics. Seven multidrug-resistant (MDR) of Pseudomonas aeruginosa strains were isolated from urine and bronchial specimens. All isolates showed resistance to imipenem and meropenem (MIC; > or =16 mg/L). The resistance to carbapenems in two of seven strains was associated with the production of a metallo-beta-lactamases. Plasmids DNA probes were used to investigate the presence of genes coding for IMP-type enzymes. PCR experiments revealed that bla(IMP) genes were present in two isolates of Pseudomonas aeruginosa (MIC >32 microg/mL for both carbapenems).     

Occurrence of blaOXA-23 gene in imipenem-susceptible Acinetobacter baumannii

The aim of the current study was to describe the occurrence of the blaOXA-23 gene and the ISAba1 element in imipenem-susceptible Acinetobacter baumannii strains. By performing the polymerase chain reaction mapping using combinations of ISAba1 forward primers and the blaOXA-23-like gene reverse primers, we demonstrated that the ISAba1 element did not occur upstream of the blaOXA-23 gene in five of 31 isolates, which explained the lack of resistance to imipenem despite the presence of the blaOXA-23 gene. All of the blaOXA-23-positive isolates were susceptible to imipenem and meropenem with minimal inhibitory concentration ≤ 4 μg/mL. Pulsed-field gel electrophoresis analysis revealed four genotypes among the five blaOXA-23-positive isolates. The current report of the blaOXA-23 gene in imipenem-susceptible isolates provided evidence that this gene may be silently spread in a hospital environment and highlighted the threat of undetected reservoirs of carbapenemase genes.     

Molecular characterization of imipenem-resistant Pseudomonas aeruginosa in Hiroshima, Japan

Pseudomonas aeruginosa showing resistance to imipenem were found in 100 of 1,058 strains (9.5%) from six hospitals (a-f) in Hiroshima City, Japan. Of the 100 strains, 14 (14%) were double disk synergy test positive using sodium mercaptoacetic acid disks, and 18 (18%) were bla(IMP-1) or bla(VIM-2) allele positive by polymerase chain reaction (PCR). Among 100 imipenem-resistant strains, 32 were categorized into multi-drug resistant strains, in which 13 were positive for the metallo-beta-lactamase gene. Fifty-one strains (51%) among the 100 imipenem-resistant strains had elevated RND efflux pump activity against levofloxacin. But only 6 of 51 strains were classified as multi-drug resistant strains. The pulsed field gel electrophoresis analysis of the Spe I-digested DNA from the 100 isolates suggested not only clonal spread but spread of heterogeneous clones started to contribute to the prevalence of metallo-beta-lactamase producing P. aeruginosa strains in Japanese hospitals.     

Molecular characterization of multidrug-resistant Escherichia coli isolates from Irish cattle farms

This study describes the genotypic characteristics of a collection of 100 multidrug-resistant (MDR) Escherichia coli strains recovered from cattle and the farm environment in Ireland in 2007. The most prevalent antimicrobial resistance identified was to streptomycin (100%), followed by tetracycline (99%), sulfonamides (98%), ampicillin (82%), and neomycin (62%). Resistance was mediated predominantly by strA-strB (92%), tetA (67%), sul2 (90%), bla(TEM) (79%), and aphA1 (63%) gene markers, respectively. Twenty-seven isolates harbored a class 1 integrase (intI1), while qacEΔ1 and sul1 markers were identified in 25 and 26 isolates, respectively. The variable regions of these integrons contained aminoglycoside, trimethoprim, and β-lactam resistance determinants (aadA12, aadB-aadA1, bla(OXA-30)-aadA1, dfrA1-aadA1, dfrA7). Class 2 integrons were identified less frequently (4%) and contained the gene cassette array dfrA1-sat1-aadA1. Resistance to ampicillin, neomycin, streptomycin, sulfonamide, and tetracycline was associated with transferable high-molecular-weight plasmids, as demonstrated by conjugation assays. A panel of virulence markers was screened for by PCR, and genes identified included vt1, K5 in 2 isolates, papC in 10 isolates, and PAI IV(536) in 37 isolates. MDR commensal E. coli isolates from Irish cattle displayed considerable diversity with respect to the genes identified. Our findings highlight the importance of the commensal microflora of food-producing animals as a reservoir of transferable MDR.     

铜绿假单胞茵肺炎治疗和预后的临床研究

目的探讨感染铜绿假单胞菌肺炎患者的治疗和预后。方法选取2011年1月至2013年2月浙江大学医学院附属第一医院住院的铜绿假单胞菌肺炎患者,共211例作为研究对象。根据药敏试验结果,把铜绿假单胞菌株分为非多重耐药、多重耐药菌株,分别探讨非多重耐药、多重耐药铜绿假单胞菌所致肺炎的治疗和预后。结果非多重耐药、多重耐药铜绿假单胞菌肺炎治疗有效率分别为91.0% （144/155 ）,35. 7% （20/56 ）,差异有统计学意义（P 〈 0. 05）,死亡率分别为2. 6% （4/155）、32. 1%（ 18/56）,差异有统计学意义（P 〈0.05）。抗菌药单药或联合治疗方案对非多重耐药铜绿假单胞菌肺炎的临床有效率差异无统计学意义（P〉0.05）,联合治疗方案能缩短非多重耐药铜绿假单胞菌肺炎的平均住院天数（P〈0. 05）;抗菌药单药或联合治疗方案对多重耐药铜绿假单胞菌肺炎的临床有效率、平均住院天数差异无统计学意义（P 〉0.05）。结论非多重耐药铜绿假单胞菌肺炎治疗疗效好,死亡率低,联合治疗方案可缩短非多重耐药铜绿假单胞菌肺炎的平均住院天数。多重耐药铜绿假单胞菌肺炎治疗疗效差,死亡率高。