大肠埃希菌体外对氟喹诺酮类药物交叉耐药的研究

目的探讨大肠埃希菌在体外对氟喹诺酮类药物的交叉耐药性。方法采用多步诱导法,对32株临床分离的氟喹诺酮类敏感大肠埃希菌分别进行环丙沙星、左氧氟沙星、加替沙星的诱导性耐药试验;用琼脂稀释法测定药物敏感性。结果22株大肠埃希菌诱导出稳定的高耐氟喹诺酮菌株;与原株比较,耐药株的MIC分别增加了32-3 000倍,三种氟喹诺酮药物诱导的耐药株对三种药物存在交叉耐药性;进行测序的1株诱导高度耐药菌株的gyrA发生Ser83→Leu、Asp87→Asn,parC发生ser80→Ile的氨基酸替换,而测序的一株敏感菌株未发现氨基酸改变。结论在低浓度抗菌药物的长期压力下,可诱导大肠埃希菌产生对氟喹诺酮类药物的获得性耐药,氟喹诺酮药物之间存在交叉耐药性。     

铜绿假单胞菌的耐药性及其耐氟喹诺酮机制的研究

目的：了解铜绿假单胞菌的耐药性及其耐氟喹诺酮的机制。方法：用纸片扩散法测定626株铜绿假单胞菌对11种抗生素的耐药性。琼脂稀释法测定40株耐环丙沙星的铜绿假单胞菌对环丙沙星和左氧氟沙星的最低抑菌浓度（MIC），聚合酶链反应－限制性长度多态性分析检测耐环沙星的铜绿假单胞菌的gyrA基因和parC基因突变，结果：626株铜绿假单胞菌中耐环丙沙星的180株（28．8％），耐左氧氟沙星的219株（35．0％），40株耐环丙沙星的铜绿假单胞菌有30株（75％）发生gyrA基因83位点突变，26株（65％）发生parC基因87位点突变，两种突变同时发生的25株（62．5％），结论：铜绿假单胞菌的耐药性日趋严重，临床分离的铜绿假单胞菌耐氟喹诺酮的机制大多为药物作用靶位gyrA和parC的基因突变。     

Fluoroquinolone resistance in Neisseria gonorrhoeae.

Fluoroquinolones and broad-spectrum cephalosporins are the most effective antimicrobial agents for the treatment of gonorrhea. However, clinically significant resistance to fluoroquinolones has emerged in Neisseria gonorrhoeae. Fluoroquinolone-resistant strains account for approximately 10% of all gonococcal strains in Hong Kong and the Republic of the Philippines. As many as 50% of strains from some Far Eastern countries exhibit decreased susceptibility (intermediate resistance) to fluoroquinolones. Strains with intermediate resistance and clinically significant resistance are being isolated sporadically in North America, where resistant strains have been associated with an outbreak and with failure of infections to respond to treatment with doses of ciprofloxacin and ofloxacin recommended by the Centers for Disease Control and Prevention; strains exhibiting decreased susceptibility to these agents are endemic in at least one metropolitan area. Monitoring for fluoroquinolone resistance is now critical for ensuring adequate treatment of infections with resistant strains and for maximizing the time during which fluoroquinolones may be used to treat gonorrhea.     

四环素诱导表皮葡萄球菌对氟喹诺酮类耐药性研究

目的　为研究氟喹诺酮类抗菌药物非特异性耐药机制建立细菌筛选方法,并研究其耐药特点及遗传稳定性。方法　使用高浓度四环素作诱导剂,分步诱导敏感表皮葡萄球菌产生高耐突变株,并从中选择对环丙沙星和司帕沙星耐药菌株。结果　经过4 步四环素诱导突变后,获得的突变株对四环素的M IC增加了500 倍,这些菌株中约有1/3 对环丙沙星和司帕沙星中度耐药,MIC比亲代株增加了60 倍。子代菌与亲代菌相比主要生化反应无改变,连续传代培养证明突变株对氟喹诺酮类药物的抗药性可稳定遗传。结论　采用四环素诱导突变的方法可使细菌获得对氟喹诺酮类的耐药性,提示用其它抗菌药物治疗感染失败的患者换用氟喹诺酮类药物时应慎重     

大肠埃希菌对氟喹诺酮类的耐药性及其机制研究

目的 探讨大肠埃希菌(ECO)对氟喹诺酮类药物的耐药率及耐药机制.方法 K-B法测定100株ECO对5种氟喹诺酮抗菌药物的耐药性,试管稀释法测定耐环丙沙星和左氧氟沙星的最低抑菌浓度(MIC);错配PCR技术检测耐环丙沙星ECO gyrA基因和parC基因的突变.结果 100株ECO中耐环丙沙星有65株;环丙沙星MIC50、MIC90分别是32、128 μg/ml,左氧氟沙星MIC50、MIC90是16、64 μg/ml;基因位点结果显示,耐环丙沙星的65株中,有60株发生gyrA、parC一个或多个基因位点的突变,有5株未发生突变.结论 gyrA、parC基因突变是该地区ECO,对氟喹诺酮类药物耐药的重要机制,且基因突变位点越多其耐药程度越高.     

广西壮族自治区1994-2013年伤寒流行病学特征及菌株耐药分析

目的 分析1994-2013年广西地区伤寒流行特征、菌株耐药特征及其变迁。方法 采用描述流行病学方法分析1994-2013年广西地区伤寒疫情报告资料,对分离自伤寒病例475株沙门菌,利用纸片扩散法及肉汤微量稀释法检测抗菌药物最小抑菌圈和抑菌浓度（MIC）,依据CLSI 2012版敏感判定标准,判定菌株的耐药情况。结果 20年间广西地区共报告伤寒病例57 928例,年均发病率为6.29/10万,病死率为0.03%。<20岁人群发病较高,发病无性别差异,病例以农民和学生为主,主要分布在广西北部地区,全年均有发病,发病高峰在5-10月。2001-2013年发生13起大的暴发疫情,传播方式以水型为主。475株菌对第三代头孢类抗生素头孢噻肟和氟喹诺酮类诺氟沙星的敏感率为100%,对四环素、氯霉素、氨苄西林、庆大霉素的敏感率约为98%,对环丙沙星的敏感率为89.89%;对链霉素、复方新诺明的敏感性较低,为67.73%和65.89%。发现1株环丙沙星耐药、47株环丙沙星敏感性降低的菌株。暴发株与散发株耐药情况无差别。有28株菌耐≥3种抗生素,首次发现1株同时对氨苄西林、氯霉素、链霉素、复方新诺明、四环素、萘啶酸（ACSSxT-NAL）耐药的多重耐药菌株。多耐药株多见于伤寒小范围暴发疫情。结论 广西地区伤寒发病水平仍较高,且菌株出现对临床常用的氟喹诺酮类药物敏感性降低及多重耐药现象,应加强疫情及耐药监测。     

Contribution of AcrAB efflux pump to ciprofloxacin resistance in Klebsiella pneumoniae isolated from burn patients

Resistance to fluoroquinolones has been recently increased among bacterial strains isolated from outpatients. Multidrug-resistant K. pneumoniae is one of the major organisms isolated from burn patients and the AcrAB efflux pump is the principal pump contributing to the intrinsic resistance in K. pneumoniae against multiple antimicrobial agents including ciprofloxacin and other fluoroquinolones. Fifty-two K. pneumoniae isolated from burn patients in Shahid Motahari hospital and confirmed by conventional biochemical tests. Antimicrobial susceptibility testing was done according to CLSI 2011 guidelines, to determine the antimicrobial resistance pattern of isolates. AcrA gene was detected among ciprofloxacin-resistant isolates by PCR assay. MICs to ciprofloxacin were measured with and without carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Forty out of the 52 K. pneumoniae isolated from burn patients in Shahid Motahari hospital were resistant to ciprofloxacin according to breakpoint of CLSI guideline. PCR assay for acrA gene demonstrated that all ciprofloxacin-resistant isolates harbored acrA gene coding the membrane fusion protein AcrA and is a part of AcrAB efflux system. Among these isolates, 19 strains (47.5%) showed 2 to 32 fold reduction in MICs after using CCCP as an efflux pump inhibitor. The other 21 strains (52.5%) showed no disparity in MICs before and after using CCCP. In conclusion, the AcrAB efflux system is one of the principal mechanisms contribute in ciprofloxacin resistance among K. pneumoniae isolates but there are some other mechanisms interfere with ciprofloxacin resistance such as mutation in target proteins of DNA gyrase of topoisomerase IV enzymes.     

Resistance to Fluoroquinolone by a Combination of Efflux and Target Site Mutations in Enteroaggregative Escherichia coli Isolated in Korea

ObjectivesEnteroaggregative Escherichia coli (EAEC) was recently reported as a major diarrheagenic pathogen in infant and adult travelers, both in developing and developed countries. EAEC strains are known to be highly resistant to antibiotics including quinolones. Therefore in this study we have determined the various mechanisms of quinolone resistance in EAEC strains isolated in Korea.MethodsFor 26 EAEC strains highly resistant to fluoroquinolone, minimal inhibitory concentrations for fluoroquinolones were determined, mutations in the quinolone target genes were identified by PCR and sequencing, the presence of transferable quinolone resistance mechanism were identified by PCR, and the contribution of the efflux pump was determined by synergy tests using a proton pump inhibitor. The expression levels of efflux pump-related genes were identified by relative quantification using real-time PCR.ResultsApart from two, all tested isolates had common mutations on GyrA (Ser83Leu and Ser87Gly) and ParC (Ser80Gln). Isolates EACR24 and EACR39 had mutations that have not been reported previously: Ala81Pro in ParC and Arg157Gly in GyrA, respectively. Increased susceptibility of all the tested isolates to ciprofloxacin and norfloxacin in the presence of the pump inhibitor implies that efflux pumps contributed to the resistance against fluoroquinolones. Expression of the efflux pump-related genes, tolC, mdfA, and ydhE, were induced in isolates EACR 07, EACR 29, and EACR 33 in the presence of ciprofloxacin.ConclusionThese results indicate that quinolone resistance of EAEC strains mainly results from the combination of mutations in the target enzyme and an increased expression of efflux pump-related genes. The mutations Ala81Pro in ParC and Arg157Gly in GyrA have not been reported previously; the exact influence of these mutations should be investigated further.     

Factors Related to Increasing Prevalence of Resistance to Ciprofloxacin and Other Antimicrobial Drugs in Neisseria gonorrhoeae, United States

Using data from the Gonococcal Isolate Surveillance Project, we studied changes in ciprofloxacin resistance in Neisseria gonorrhoeae isolates in the United States during 2002-2007. Compared with prevalence in heterosexual men, prevalence of ciprofloxacin-resistant N. gonorrhoeae infections showed a more pronounced increase in men who have sex with men (MSM), particularly through an increase in prevalence of strains also resistant to tetracycline and penicillin. Moreover, that multidrug resistance profile among MSM was negatively associated with recent travel. Across the surveillance project sites, first appearance of ciprofloxacin resistance in heterosexual men was positively correlated with such resistance for MSM. The increase in prevalence of ciprofloxacin resistance may have been facilitated by use of fluoroquinolones for treating gonorrhea and other conditions. The prominence of multidrug resistance suggests that using other classes of antimicrobial drugs for purposes other than treating gonorrhea helped increase the prevalence of ciprofloxacin-resistant strains that are also resistant to those drugs.     

Antimicrobial resistant pattern of Escherichia coli strains isolated from pediatric patients in Jordan

The present study was conducted to investigate antimicrobial resistant pattern of Escherichia coli (E. coli) strains isolated from clinical specimens of Jordanian pediatric patients during the period from January to December 2008. A total of 444 E. coli strains were isolated from clinical specimens and tested for their susceptibility to different antimicrobial drugs. Overall, high resistance rate was observed for ampicillin (84%), followed by amoxicillin-clavulanic acid (74.3%), cotrimoxazole (71%), nalidixic acid (47.3%), cephalothin (41%). Lower resistance rates were observed for amikacin (0%) followed by Cefotaxime (11%), Ceftriaxone (11.7%), ciprofloxacin (14.5%), Norfloxacin (16.5%), gentamicin (17.3%) cephalexin (20.9%), Ceftazidime (22.5%), cefixime (29.6%), and cefaclor (32.8%). Ampicillin, amoxicillin-clavulanic acid and cotrimoxazole were found to be ineffective at in vitro inhibition of the E. coli of pediatric origin. Amikacin was highly effective for E. coli with susceptibility rate of 100%. The majority of E. coli strains were susceptible to third generation cephalosporins and fluoroquinolones.     

Antimicrobial susceptibility patterns of Salmonella enterica serotype typhi in eastern Nepal

The aim of the present study was to evaluate antimicrobial susceptibility patterns with special reference to multidrug resistance, susceptibility to ciprofloxacin, and bacteriophage typing of Salmonella enterica serotype Typhi isolated from blood sent for culture in a tertiary-care teaching hospital in eastern Nepal during January 2000-December 2004. In total, 132 strains of S. enterica Typhi, isolated from 2,568 blood culture samples collected from cases of suspected enteric fever, were tested for susceptibility to commonly-used antimicrobials by the disc-diffusion method. There were 35 multidrug-resistant strains. None of the isolates were resistant to ciprofloxacin. Of 52 isolates tested for minimum inhibitory concentration (MIC) of ciprofloxacin, 36 (69.23%) showed reduced susceptibility (MIC >0.25 mg/L). Of 112 strains tested for nalidixic acid susceptibility, 86 (76%) were resistant. Strains with reduced susceptibility to ciprofloxacin and resistance to nalidixic acid could be correlated. The commonest phage type was El. Nalidixic acid susceptibility could be a useful screening test for the detection of decreased susceptibility of S. Typhi to ciprofloxacin, a drug which is commonly used even for minor ailments in this area.     

8种氟喹诺酮类药物的体外敏感性

目的比较大肠埃希菌、铜绿假单胞菌和金黄色葡萄球菌对8种氟喹诺酮类药物的体外抗菌活性. 方法按NCCLS推荐的标准纸片扩散法(K-B法)对69株大肠埃希菌、84株铜绿假单胞菌和82株金黄色葡萄球菌进行8种三代氟喹诺酮药物的体外敏感性实验. 结果对于大肠埃希菌和铜绿假单胞菌,环丙沙星的体外抗菌活性最强;对于金黄色葡萄球菌,虽环丙沙星的敏感率低于氧氟沙星、左氧氟沙星及司帕沙星等,但并未提示差异有显著性(P>0.05). 结论 8种帕喹诺酮类药物显示明显的交叉耐药性,环丙沙星的体外敏感性结果对于临床应用三代氟喹诺酮类药物具有一定的指导意义.     

2009-2013年某医院鲍氏不动杆菌的 分布及耐药性变迁

摘要:目的　研究2009-2013年某医院临床分离鲍氏不动杆菌的分布及耐药性的变迁。方法　回顾分析2009-2013年我院住院患者标本中分离的鲍氏不动杆菌的分布情况及其药敏试验结果,采用仪器法和纸片扩散法检测鲍氏不动杆菌对常用10种抗菌药物的耐药性,分析5年来鲍氏不动杆菌的分布特点及耐药性变迁。结果　5年间共分离到鲍氏不动杆菌1200株,2009-2011年其数量和所占总分离菌株的构成比呈逐年递增。标本类型中痰、分泌物和血占分离标本的前3位,痰标本最常见,占82.83%。鲍氏不动杆菌对亚胺培南、哌拉西林/他唑巴坦、头孢哌酮/舒巴坦的耐药率呈逐年上升趋势。对环丙沙星耐药率最高,平均达77.27%。结论　5年来鲍氏不动杆菌对部分抗菌药物的耐药性呈升高趋势,应加强鲍氏不动杆菌的耐药性监测,依据体外药敏结果合理使用抗菌药物。     

大肠埃希菌耐药性分析及生物被膜形成能力研究

目的 探讨医院产ESBLs大肠埃希菌(ECO)临床分离株的流行现状、耐药性及其生物被膜形成能力,为医院感染控制和临床诊疗感染性疾病提供依据.方法 采用法国生物梅里埃公司的VITEK-2 Compact全自动微生物分析仪对菌株进行鉴定和药物敏感性分析,采用结晶紫半定量方法检测菌株的生物被膜形成能力.结果 医院ECO检出前3位病区分别为普外病区、肾脏病区和呼吸病区;检出前3位标本分别为痰、尿和血液;466株ECO临床分离菌株中,产ESBLs菌株297株占63.73％,非产ESBLs菌株169株占36.27％;对＞3类抗菌药物耐药ECO 357株占76.61％,其中,产ESBLs菌株287株占61.59％,耐药率最高的为氨苄西林,其次为头孢唑林和头孢曲松;环丙沙星和左氧氟沙星的耐药率均＞60.0％;已出现耐亚胺培南ECO;对于临床常用的青霉素类、头孢菌素类、氟喹诺酮类、氨基糖苷类和单酰胺类抗菌药物,与非产ESBLs菌株相比,产ESBLs菌株的MIC值与耐药率显著升高;而对头霉素类、呋喃类、含酶抑制剂的哌拉西林/他唑巴坦和碳青霉烯类药物的敏感性产ESBLs组与非产ESBLs组比较差异无统计学意义;＞90.00％的ECO具有生物被膜形成能力,生物被膜形成量以中量为主,不同标本来源的菌株之间生物被膜形成能力差异无统计学意义.结论 医院ECO产ESBLs比例高,生物被膜形成能力强,呈现多药耐药的特征,医院应加强产ESBLs菌株的分子流行病学调查和感染控制,避免医院感染的暴发流行.     

Bacterial resistance to ciprofloxacin in Greece: results from the National Electronic Surveillance System. Greek Network for the Surveillance of Antimicrobial Resistance.

According to 1997 susceptibility data from the National Electronic System for the Surveillance of Antimicrobial Resistance, Greece has high rates of ciprofloxacin resistance. For most species, the frequency of ciprofloxacin-resistant isolates (from highest to lowest, by patient setting) was as follows: intensive care unit > surgical > medical > outpatient. Most ciprofloxacin-resistant strains were multidrug resistant.     

Pseudomonas aeruginosa: a multicentric study of antibiotic resistance (1999-2000)

A retrospective multicentric study was carried out over a period of 2 years (1999-2000). 2659 strains of Pseudomonas aeruginosa were collected from 4 university hospitals (Charles Nicolle Hospital, Pediatric Hospital and National Centre of Bone Marrow Transplantation in Tunis, Habib Bourguiba Hospital in Sfax). Epidemiological profile and antibiotic susceptibility were analysed. All bacteria were identified by conventional methods and antibiotic susceptibility tests were performed according to CA-SFM guidelines. The strains were recovered essentially from surgical wards (33%) and intensive care units (22%). Pseudomonas aeruginosa was isolated mainly from pus (36%), urine (32%) and respiratory samples (18%). 25% of strains were resistant to ticarcilline, 18% to cefsulodine, 9% to ceftazidime, 14% to imipenem and amikacin and 25% to ciprofloxacin. Moreover, the resistance rates varied from hospital to hospital and from unit to another. The resistant strains were isolated particularly from urology and intensive care units: respectively 62% and 39% for ticarcilline; 26% and 13% for ceftazidime. The acquired resistance to b-lactams seems largely due to penicillinase production. The frequency of resistance to ceftazidime was the lowest and seems associated to chromosomal cephalosporinase over production.     

解脲脲原体对氟喹诺酮类药物耐药性研究

目的探讨解脲脲原体对氟喹诺酮类药物的耐药状况与gyrA基因突变之间的关系。方法对鉴定确认的解脲脲原体临床分离株,采用微量肉汤稀释法检测其环丙沙星、氧氟沙星和左旋氧氟沙星的最小抑菌浓度（MIC）,随机抽取28株菌株,PCR扩增gyrA基因并测序,采用Blast比对法分析临床菌株与标准菌株的序列差异。结果解脲脲原体的环丙沙星、氧氟沙星和左旋氧氟沙星MIC50分别为8,4和2 mg/L;MIC90分别为64,16和8 mg/L;在28株解脲脲原体菌株中,经测序分析发现gyrA基因3种突变形式：（1）101位丙氨酸改变为缬氨酸;（2）112位天冬氨酸改变为谷氨酸;（3）267位碱基T缺失。具有基因突变的菌株其MIC明显高于没有突变的菌株。结论江苏省部分地区解脲脲原体对第1、2代氟喹诺酮类药物耐药严重,此类药物不再适用于治疗解脲脲原体感染;解脲脲原体对氟喹诺酮类药物的耐药主要是由于gyrA基因突变导致相应氨基酸改变所介导。     

Clinical epidemiology of ciprofloxacin resistance and its relationship to broad-spectrum cephalosporin resistance in bloodstream infections caused by Enterobacter species.

OBJECTIVES: To evaluate the clinical features of ciprofloxacin-resistant Enterobacter bacteremia and to examine the risk factors for ciprofloxacin resistance in Enterobacter species isolates causing bacteremia. DESIGN: A case-control study. SETTING: A 1,500-bed, tertiary-care university hospital and referral center. PATIENTS: All patients older than 16 years with Enterobacter species isolated from blood were enrolled. The medical records of 183 patients with clinically significant Enterobacter bacteremia from January 1998 to December 2002 were identified. We compared patients with bacteremia caused by ciprofloxacin-susceptible isolates with patients with bacteremia caused by ciprofloxacin-resistant isolates. RESULTS: Twenty-three (12.6%) of the patients had bacteremia caused by isolates resistant to ciprofloxacin. There were no significant differences in age, gender, underlying diseases, primary site of infection, or Acute Physiology and Chronic Health Evaluation II score between the ciprofloxacin-resistant and the ciprofloxacin-susceptible groups. Broad-spectrum cephalosporin resistance, defined as resistance to cefotaxime or ceftazidime in vitro, was detected in 21 (91.3%) of 23 ciprofloxacin-resistant isolates compared with 65 (40.6%) of 160 ciprofloxacin-susceptible isolates (P < .001). Multivariate analysis revealed that independent risk factors for ciprofloxacin resistance were the prior receipt of fluoroquinolones (P < .001) and broad-spectrum cephalosporin resistance (P < .001). CONCLUSIONS: In Enterobacter species isolates causing bacteremia, ciprofloxacin resistance was closely associated with the prior receipt of fluoroquinolones and broad-spectrum cephalosporin resistance. The close relationship between ciprofloxacin resistance and broad-spectrum cephalosporin resistance is particularly troublesome because it severely restricts the therapeutic options for Enterobacter species infection.     

陕西部分地区零售肉中沙门菌耐药的检测分析

目的 对陕西省西安市和杨凌示范区超级市场及农贸市场零售肉中沙门菌的药敏性进行检测分析.方法 采用美国临床实验室标准化委员会(National Committee of Clinical Laboratorystandard,NCCLS)推荐的琼脂稀释法,以大肠埃希菌ATCC25922和粪肠球菌ATCC29212为质控菌株,对193株沙门菌进行了7大类共14种抗生素的药敏性检测.结果 沙门菌分离株对磺胺甲嗯唑的抗性最高(44.6%),其次为卡那霉素(40.9%)、四环素(37.8%)、阿莫西林(26.9%)、氨苄西林(25.4%)、庆大霉素(23.3%)和氯霉素(21.8%)等;对氟喹诺酮类抗生素的耐药率依次分别为环丙沙星22.3%、恩诺沙星21.8%、左氧氟沙星20.7%、加替沙星20.2%.55株(28.5%)沙门菌为多重耐药株,其中28株(14.5%)可耐至少13种抗生素,24株(12.4%)的耐药介于4到12种之间.结论 陕西西安地区零售肉沙门菌多重耐药现象比较严重.