Antimicrobial susceptibility patterns and distribution of blaOXA genes among Acinetobacter spp. Isolated from patients at Tehran hospitals

Multiple drug-resistant strains of Acinetobacter have created therapeutic problems worldwide. This study was conducted to determine the antimicrobial susceptibility patterns and prevalence of bla(OXA-type) carbapenemases among isolates of Acinetobacter spp. obtained from Iranian patients. Here, 128 Acinetobacter isolates were identified at the species level, and their susceptibilities to different antibiotics were determined using disk agar diffusion testing. Isolates were then subjected to multiplex-PCR targeting bla(OXA) genes. More than 50% of the isolates showed multidrug resistance to different antibiotics. The rates of susceptibility to imipenem, meropenem, piperacillin-tazobactam, and amikacin were 50.7, 50, 42.1, and 38.2%, respectively. The MICs of carbapenems for the resistant isolates ranged from 64 to > or = 256 microg/ml. All strains of Acinetobacter baumannii possessed a bla(OXA-51-like) gene. The co-existence of bla(OXA-51-like)/bla(OXA-23-like) and bla(OXA-51-like)/bla(OXA-24-like) was detected in 25% (n=32) and 17.9% (n=23) of the isolates, respectively. Over 70% of carbapenem-resistant strains contained at least two genes encoding OXA-type carbapenemase. Resistance to carbapenems in the population of Acinetobacter strains in Iran is high, with the majority of isolates showing multidrug resistance. A wide diversity of OXA genes exists among the strains of A. baumannii in Iran. Detection of bla(OXA-51-like) can be used as a simple and reliable method to differentiate A. baumannii strains from other species.     

High prevalence of metallo-beta-lactamase-producing acinetobacter baumannii in a teaching hospital in Tabriz, Iran

Metallo-beta-lactamase (MBL)-producing Acinetobacter baumannii has become a growing therapeutic concern worldwide. The aims of this study were to evaluate the antimicrobial susceptibility of A. baumannii isolates and to determine the prevalence of MBL genes among carbapenem non-susceptible isolates. During a period of 16 months (March 2008-June 2009), 100 isolates of A. baumannii were collected from different clinical specimens of inpatients admitted to the largest teaching hospital in the northwest of Iran. All isolates were tested for antimicrobial susceptibility by Kirby-Bauer disk diffusion method. Carbapenem non-susceptible isolates were further screened for production of MBL by Etest and were then subjected to PCR for detection of MBL genes of types bla(IMP) and bla(VIM). Among 63 carbapenem (imipenem and meropenem) non-susceptible isolates of A. baumannii, 31 (49%) were found to be MBL producers. Of 31 MBL-producing isolates, 19 (61%) carried the bla(IMP) gene and 9 (29%) carried the bla(VIM) gene. All MBL-producing isolates were multidrug resistant. This is the first report of IMP and VIM types among MBL-producing A. baumannii in Iran.     

Molecular epidemiology of an outbreak of imipenem-resistant Acinetobacter baumannii carrying the ISAba1-bla(OXA-51-like) genes in a Korean hospital

Between January 2004 and December 2004, an outbreak of imipenem-resistant Acinetobacter baumannii (IRAB) in 2 intensive care units (ICU) of Chosun University Hospital, Korea affected 77 patients. A case-control study revealed that the time spent in the hospital and mechanical ventilation practices were risk factors. IRAB was isolated from the hands of 4% (5/124) of healthcare workers; 27.3% (21/77) of the samples obtained from the ICU environment. A pulsed-field gel electrophoresis analysis showed that 82.1% (23/28) of clinical IRAB isolates and 85.7% (6/7) of environmental IRAB isolates were type A. The ISAba1F/OXA-51-likeR PCR showed that 93.7% (30/32) of IRAB strains had the ISAba1 gene upstream of the bla(OXA-51-like) gene. Two ISAba1F/OXA-51-likeR PCR-negative IRAB strains were bla(IMP-1) positive. All of the IRAB strains tested by PCR were negative for bla(VIM), bla(SIM), bla(GIM-1), bla(SPM-1), bla(GES), bla(OXA-23-like), bla(OXA-24-like), and bla(OXA-58-like) carbapenemase genes. After implementing an infection control strategy, a steady reduction in the attack rate of IRAB infection was observed.     

血培养中碳青霉烯类耐药鲍曼不动杆菌感染特征及耐药基因分析

目的 分析我院2018—2020年临床血培养检出的碳青霉烯类耐药鲍曼不动杆菌(carbapenem-resistant Acinetobacter Baumannii, CRAB)的感染特征及耐药基因分布情况,为防止院内感染、临床抗菌药物的合理使用及临床早期经验性提供依据。方法 收集2018年1月至2020年12月临床分离的血培养鲍曼不动杆菌48株,应用Logistic回归分析血流感染CRAB的可能危险因素。采用VITEK2 Compact全自动微生物分析系统进行细菌鉴定及药敏试验,热裂解法提取DNA,并应用PCR的方法检测常见鲍曼不动杆菌的碳青霉烯类耐药基因(OXA-23、OXA-51、NDM-1)及插入序列ISAba-1、整合酶Int I基因。结果 在所有XDR-AB中重症医学科的检出率最高,占68.4%。Logistic回归分析结果显示,肺炎、恶性肿瘤、静脉穿刺置管、输血、气管插管、尿管插管、胃管插管及支气管镜检查与血流感染CRAB有关(P<0.05),且肺炎(OR=81.894)是血流感染CRAB的独立危险因素(χ²=4.689,P<0.05)。多重耐药菌(13株)和广泛耐药菌(19株)均携带有OXA-23与OXA-51基因。敏感菌株中OXA-51基因检出率为43.8%,没有检测出OXA-23基因。48株菌株均没有检测出NDM-1基因。耐药基因OXA-23、OXA-51、ISAba-1的检出率在耐药菌和敏感菌之间差异有统计学意义(χOXA-232=48.000,χOXA-512=13.066,χISAba-12=15.709,均P<0.05)。结论 肺炎为我院血流感染CRAB的独立危险因素,非恶性肿瘤的患者感染CRAB的风险是有恶性肿瘤患者的21倍。本院碳青霉烯类耐药鲍曼不动杆菌主要为OXA-23型与OXA-51型菌株,且携带有OXA-23耐药基因的鲍曼不动杆菌对碳青霉烯类药物耐药率为100%,未携带该耐药基因的鲍曼不动杆菌对该类药物均呈敏感,提示OXA-23基因可能是造成CRAB耐药的原因,临床应加强院感管理,合理使用抗菌药物,防止该类鲍曼不动杆菌的暴发传播。     

耐亚胺培南鲍曼不动杆菌OXA-23基因检测及分析

目的了解临床分离的耐亚胺培南鲍曼不动杆菌OXA-23摹因的存在状况。方法收集我院临床分离的非重复耐亚胺培南鲍曼不动杆菌16株,采用纸片扩散法确定其耐药率,以PCR对亚胺培南耐药菌株进行OXA-23基因的检测并测序,序列与基因库比对。结果16株耐亚胺培南鲍曼不动杆菌中,OXA-23基因阳性11株,阳性率为68．8％。随机抽取2株OXA-23基因阳性株进行测序后,经网EGenBank比对,与OXA-23标准株100％同源。结论分离菌株主要来源于痰标本,耐亚胺培南鲍曼不动杆菌OXA-23雄因的携带率较高,分离菌株的耐药性可能与OXA-23型碳青霉烯酶基因有关。     

梅州地区临床分离耐碳氢霉烯类鲍曼不动杆菌的耐药机制及分子流行病学研究

目的 了解梅州地区临床分离的耐碳青霉烯类鲍曼不动杆菌的耐药性,探讨其耐药机制及分子流行病学特征。方法 收集梅州地区5所医院2012年1～12月临床分离的非重复耐碳青霉烯类鲍曼不动杆菌210株,采用K-B法检测药敏性,改良Hodge试验筛选耐碳青霉烯表型,PCR扩增IMP、VIM、OXA-23、OXA-24、OXA-51和OXA-58型碳氢霉烯酶基因,并测序。应用ERIC-PCR分型及同源性分析。结果 药敏结果显示,17种药物除多粘菌素B耐药率为0.48%外,其他药敏耐药率都高于60%;改良Hodge试验阳性菌株163株(77.62%)。扩增结果显示Bla-OXA-51的检出率为最高为94.29%(198/210),Bla-OXA-23的检出率次之为78.57%(165/210),Bla-VIM的检出率为4.29%(9/210),Bla-IMP、Bla-OXA-24、Bla-OXA-58均未被检出。210株菌株分为7个ERIC基因型,其中A型97株,B型44株,H型25株,为主要的流行克隆株。结论 梅州地区临床分离的耐碳青霉烯类鲍曼不动杆菌耐药十分严重;产OXA-51、OXA-23和VIM型碳氢霉烯酶是本地区鲍曼不动杆菌对碳青霉烯类药物耐药的重要机制,且耐碳青霉烯类鲍曼不动杆菌存在克隆的流行。     

多重耐药鲍曼不动杆菌主动外排泵基因abeM的测定及耐药性分析

目的了解临床分离株鲍曼不动杆菌对16种抗菌药物的耐药性,为抗耐药菌药物选择提供依据,并扩增外排泵蛋白编码基因abeM,以探讨鲍曼不动杆菌多重耐药与主动外排作用的关系。方法采用纸片扩散法(Kirby-Bauer)对收集的65株不重复鲍曼不动杆菌进行药物敏感性试验。应用聚合酶链反应测定多重耐药鲍曼不动杆菌主动外排系统abeM基因,并进行序列分析。结果收集的鲍曼不动杆菌对头孢哌酮/舒巴坦敏感,耐药率15.38%,对亚胺培南耐药率为52.31%,对其余抗菌药物的耐药率在60.00%~73.85%之间;经PCR扩增,65株鲍曼不动杆菌中adeB基因阳性60株(92.31%),序列分析显示与Genbank登录的鲍曼不动杆菌ATCC 19606药物外排蛋白编码基因abeM(AB204810)的同源性为98.00%。结论 abeM主动外排作用可能是多重耐药鲍曼不动杆菌多重耐药的重要机制之一。     

Class 1 integrons and resistance gene cassettes among multidrug resistant Salmonella serovars isolated from slaughter animals and foods of animal origin in Ethiopia

The present study was undertaken to identify and characterize integrons and integrated resistance gene cassettes among multidrug resistant (MDR) Salmonella isolates from slaughter animals and food products of animal origin in Ethiopia. A total of 98 epidemiologically unrelated Salmonella isolates comprising 13 serovars were characterized using serotyping, phage typing, antimicrobial resistance testing and the pulsed-field gel electrophoresis (PFGE) method. Integron-PCR was used to detect the presence of class 1 and class 2 integrons in the MDR strains. The associated individual resistance gene cassettes were identified using specific PCRs and DNA sequencing. The location of the integrons was determined by Southern blot hybridization analysis. Among the Salmonella serovars, a high level of antimicrobial resistance was found to streptomycin (82.6%), tetracycline (75.5%), sulfamethoxazole (60.2%), spectinomycin (53.1%), ampicillin (42.8%), nalidixic acid (34.7%), nitrofurantoin (30.6%), trimethoprim (27.5%), gentamicin (20.4%) and ciprofloxacin (19.4%). Class 1 integrons were detected in 53.1% of the MDR isolates comprising serovars Anatum, Braenderup, Kentucky, Saintpaul and Typhimurium. Of the class 1 integron positive isolates 61.5% harboured the integron-associated gene cassettes: aadA2, aadA2+bla(PSE-1), dfrA1-aadA1 and dfrA12-orf-aadA2 (amplicon sizes 1000 bp, 1000+1200 bp, 1600 bp and 1900 bp, respectively). The chromosomally located aadA2 and aadA2+bla(PSE-1) resistance gene cassettes occurred exclusively in S. Typhimurium DT104 isolates, the other cassettes were found on large plasmids in several serovars. An aacCA5-aadA7 gene cassette array (amplicon size 1600 bp) was exclusively found in all MDR S. Kentucky strains of R type Str/SpeSmxGenNalAmpTetCipCef and this integron was shown to be chromosomally located. Results of the present study indicate that class 1 integrons carrying gene cassettes, which confer resistance to different classes of antimicrobials such as aminoglycosides, beta-lactams and trimethoprim are widespread among the MDR Salmonella serovars isolated from slaughter animals and food products of animal origin in Ethiopia indicating the important role of these genetic elements in the dissemination of multidrug resistance.     

新疆某医院多重耐药菌及耐药性分析

目的回顾性分析2015年新疆医院临床分离多重耐药菌(multidrug-resistant organism,MDRO)的分布、类型及耐药性,为临床控制MDRO医院感染提供有效依据,为临床合理选用抗生素提供参考依据。方法 2015年1月至2015年11月期间对我院住院患者标本培养的多重耐药菌株,对其耐药菌类型与耐药性进行分析,并对高危因素进行分析与探讨。结果共检出、共分离出4560株细菌,其中多重耐药菌1210株。鲍曼不动杆菌344株,占28.40%,大肠埃希菌288株,占23.80%,铜绿假单胞菌201株,占16.60%,肺炎克雷伯菌150株,占12.40%,金黄色葡萄球菌100株,占8.30%,耐药性:鲍曼不动杆菌对碳青霉烯类抗生素耐药性为62.30%,多耐药肠杆菌科细菌对碳青霉烯类抗生素保持高度的敏感性(100%敏感),革兰氏阳性细菌主要为金黄色葡萄球菌,耐甲氧西林的金黄色葡萄球菌(MRSA)占65%,只对万古霉素敏感,未发现耐万古霉素、耐利奈唑胺菌株。结论该院分离的多重耐药菌种类多,耐药性严重,临床医师应重视病原学检查,并严格按照药物敏感试验结果选取合理抗生素,以减少细菌耐药性的发生,降低医疗费用,降低临床病死率。     

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.     

Prevalence and molecular analysis of multidrug-resistant Acinetobacter baumannii in the extra-hospital environment in Mthatha,South Africa

IntroductionThe presence of Acinetobacter baumannii outside hospitals remains unclear. This study aimed to determine the prevalence of multidrug-resistance (MDR) A. baumannii in the extra-hospital environment in Mthatha, South Africa and to investigate the frequency of carbapenemase-encoding genes.Material and MethodsFrom August 2016 to July 2017 a total of 598 abattoir samples and 689 aquatic samples were collected and analyzed presumptively by cultural methods for the presence of A. baumannii using CHROMagar™ Acinetobacter medium. Species identification was performed by autoSCAN-4 (Dade Behring Inc., IL) and confirmed by the detection of their intrinsic bla_OXA-51 gene. Confirmed MDR A. baumannii isolates were screened for the presence of carbapenemase-encoding genes, ISAba1 insertion sequence and integrase intI1.ResultsIn total, 248 (19.3%) Acinetobacter species were isolated. Acinetobacter. baumannii was detected in 183 (73.8%) of which 85 (46.4%) and 98 (53.6%) were recovered from abattoir and aquatic respectively. MDR A. baumannii was detected in 56.5% (48/85) abattoir isolates and 53.1% (52/98) aquatic isolates. Isolates showed high resistance to antimicrobials most frequently used to treat Acinetobacter infections such as piperacillin/tazobactam; abattoir (98% of isolates resistant), aquatic (94% of isolates resistant), ceftazidime (84%, 83%), ciprofloxacin (71%, 70%), amikacin (41%, 42%), imipenem (75%, 73%), and meropenem (74%, 71%). All the isolates were susceptible to tigecycline and colistin. All the isolates carried bla_OXA-51-like. The bla_OXA-23 was detected in 32 (66.7%) abattoir isolates and 11 (21.2%) aquatic isolates. The bla_OXA-58-like was positive in 7 (14.6%) and 4 (7.7%) abattoir and aquatic isolates, respectively. Both groups of isolates lacked bla_OXA-24-like, bla_IMP-type, bla_VIM-type, bla_NDM-1, bla_SIM, bla_AmpC, ISAba1 and inI1. Isolates showed high level of Multiple Antibiotic Resistance Index (MARI) ranging from 0.20-0.52.ConclusionExtra-hospital sources such as abattoir and aquatic environments may be a vehicle of spread of MDR A. baumannii strains in the community and hospital settings.     

产气肠杆菌连续分离株的耐药性及β-内酰胺类抗生素耐药机制的研究

目的 探讨临床连续分离的产气肠杆菌耐药性及耐碳青霉烯类药物菌株对β-内酰胺类药物耐药的主要机制。方法 用Vitek2-Compact仪对临床连续分离的240株产气肠杆菌进行鉴定和常规药敏试验,并筛选出耐碳青霉烯类药物的菌株;用琼脂稀释法测定其对碳青霉烯类药物的MIC值;用改良的三维试验方法分别检测耐药菌株的ESBLs与AmpC酶;改良Hodge试验法检测碳青霉烯酶;用PCR扩增法检测3种β-内酰胺酶的耐药基因;结果 240株产气肠杆菌对23种常用抗生素的耐药率在3.8%～100%之间,最高为头孢西丁(100%)、最低为亚胺培南(3.8%);筛选出10株耐碳青霉烯类产气肠杆菌;三维试验10株菌ESBLs 及AmpC酶均为阳性,Hodge试验阳性7株。PCR结果示,携带blaKPC基因7株;携带blaCTX-M基因7株,携带blaSHV基因2株;携带blaDHA基因6株,携带blaACT/MIR型ampC基因4株; 16SrRNA基因定量确定ampC基因的表达增加的3株。结论 产气肠杆菌对临床常用抗菌药物具有较高的耐药性,其主要耐药机制为产碳青霉烯酶、ESBLs与AmpC酶。     

部分非鲍曼不动杆菌耐药性及相关基因分析

目的了解目前非鲍曼不动杆菌临床分离株的耐药现状及耐药基因携带情况。方法随机抽取100株不动杆菌临床分离株,采用分子生物学方法筛选非鲍曼不动杆菌,用E-test方法检测非鲍曼不动杆菌对12种抗生素的耐药性,用PCR方法检测16种相关耐药基因的分布。结果共筛选出17株非鲍曼不动杆菌,7株为多重耐药(41.2%),其中对头孢噻肟的耐药率为100%,对氯霉素、哌拉西林、氨苄西林和氨曲南的耐药率分别为76.5%、76.5%、64.7%和52.9%,对多粘菌素B普遍敏感;检出6种耐药基因分别为ampC、blaTEM、blaPER-1、blaOXA-23-like、blaOXA-58和Int1。结论携带超广谱β-内酰胺酶(ESBLs)基因和blaOXA-23-like基因为非鲍曼不动杆菌对β-内酰胺类和碳青霉烯类抗生素耐药的主要原因。非鲍曼不动杆菌的耐药形势严峻,应加强监测。     

阴沟肠杆菌耐药及ampC基因表达状况研究

目的 了解144株阴沟肠杆菌的耐药现状及ampC基因的表达。方法 通过纸片扩散法检测阴沟肠杆菌的药敏情况。聚合酶链反应（PCR）法检测ampC基因，克隆测序分析其特异性，并根据耐药表型对ampC基因表达状况进行分析。结果 144株阴沟肠杆菌对亚胺培南的敏感率高达98.6%，对头孢吡肟和头孢哌酮/舒巴坦的敏感率分别为65.9%和63.9%，但对阿莫西林/克拉维酸，头孢呋辛和头孢噻肟等抗菌药物的敏感率较低。120株ampC基因阳性（占83.3%)，其中36株高水平表达（占30.0%),45株诱导表达（占37.5%),未表达或低水平表达的有39株（占32.5%)，有56株合并产超广谱β-内酰胺酶（ESBLs)（占46.7%)，单纯诱导产AmpC酶的菌株除对阿莫西林/克拉维酸和头孢呋辛敏感率低外，对其他抗菌药物的敏感率均在90%以上；而单纯高产AmpC酶的菌株仅对亚胺培南和头孢吡肟的敏感率在85%以上，如合并产ESBLs，则对头孢吡肟的敏感率下降。结论 阴沟肠杆菌耐药状况严重。明确ampC基因的表达状况有助于临床抗菌药物的选用。     

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。     

Antibiotic susceptibility of staphylococci isolated in blood cultures in relation to antibiotic consumption in hospital wards.

A total of 510 isolates of Micrococcaceae, 500 of staphylococci and 10 micrococci, detected in 485 (3.3%) of 14,860 consecutive blood cultures obtained from patients at a Swedish university hospital and 2 local hospitals were identified to species level and investigated for antibiotic susceptibility. The 5 most frequently isolated species were Staphylococcus epidermidis (54.8%), S. aureus (28.0%), S. hominis (3.4%), S. warneri (3.2%) and S. haemolyticus (2.8%). All isolates of S. aureus were oxacillin sensitive. Great diversity in antibiotic resistance among coagulase negative staphylococci between hospitals and different ward units in the university hospital was observed. The frequency of antimicrobial resistance among S. epidermidis correlated with the antibiotic consumption at different ward units, in particular for ciprofloxacin (p < 0.001) and co-trimoxazole (p < 0.004). The study emphasizes the importance of monitoring antibiotic consumption and resistance patterns of nosocomial staphylococci in order to avoid emergence and spread of multi-resistant bacteria within the hospital environment.     

Citywide clonal outbreak of multiresistant Acinetobacter baumannii and Pseudomonas aeruginosa in Brooklyn,NY: the preantibiotic era has returned

BACKGROUND: Carbapenems are important agents for treating nosocomial gram-negative infections. Carbapenem-resistant bacteria have become increasingly problematic in certain regions. This study determined the citywide prevalence and molecular epidemiological features of carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa in Brooklyn, NY. METHODS: All unique patient isolates of A baumannii and P aeruginosa were collected from 15 Brooklyn hospitals from July 1, 1999, through September 30, 1999. Antibiotic susceptibilities, the genetic relatedness of resistant isolates, and the relationship between antibiotic use and resistance rates were determined. RESULTS: A total of 419 isolates of A baumannii and 823 isolates of P aeruginosa were collected. For A baumannii, 53% were resistant to meropenem and/or imipenem, and 12% were resistant to all standard antibiotics. Ribotyping revealed that a single clone accounted for 62% of the samples and was isolated from patients at all 15 hospitals. The rate of carbapenem resistance was associated with cephalosporin use at each hospital (P =.004). For P aeruginosa, 24% were resistant to imipenem, 5% to amikacin, and 15% to 29% to other antipseudomonal agents. Ribotyping revealed that 3 clones accounted for nearly half of the isolates and were shared by most hospitals. CONCLUSIONS: Approximately 400 patients were infected or colonized with carbapenem-resistant A baumannii and P aeruginosa during a 3-month period in 1999. A few strains have spread widely throughout hospitals in this region. The prevalence of resistant A baumannii seems to be correlated with cephalosporin use. Multiresistant hospital-acquired bacteria should be viewed as a serious public health issue rather than an individual hospital's problem. An intensive coordinated effort will be needed to effectively address this problem.     

Escalation of antimicrobial resistance among Streptococcus pneumoniae: implications for therapy

Over the past 2 decades, antimicrobial resistance among Streptococcus pneumoniae, the most common cause of community-acquired pneumonia (CAP), has escalated dramatically worldwide. In the late 1970s, strains of pneumococci displaying resistance to penicillin were described in South Africa and Spain. By the early 1990s, penicillin-resistant clones of S. pneumoniae spread rapidly across Europe and globally. Additionally, resistance to macrolides and other antibiotic classes escalated in tandem with penicillin resistance. Six international clones (serotypes 6A, 6B, 9V, 14, 19F, 23F) were responsible for most of these resistant isolates. Currently, 20 to 30% of S. pneumoniae worldwide are multidrug resistant (MDR) (i.e., resistant to > or = 3 different classes of antibiotics). Despite the dramatic escalation in the rate of antimicrobial resistance among pneumococci worldwide, the clinical impact of antimicrobial resistance is difficult to define. Treatment failures due to antibiotic-resistant pneumococci have been reported with meningitis, otitis media, and lower respiratory tract infections, but the relation between drug resistance and treatment failures has not been convincingly established. Clinical failures often reflect factors independent of antimicrobial susceptibility of the infecting organisms. Host factors (e.g., extremes of age; underlying immunosuppressive or debilitating disease; comorbidities), or factors that affect intrinsic virulence of the organisms (e.g., capsular subtype) strongly influence prognosis. Mortality rates are higher in the presence of multilobar involvement, renal insufficiency, need for intensive care unit (ICU) care, hypoxemia, severe derangement in physiological parameters, and comorbidities. Given these confounding factors, determining the impact of antimicrobial resistance on clinical outcomes is difficult, if not impossible. Prospective, randomized trials designed to assess the clinical significance of antimicrobial resistance among pneumococci are lacking, and for logistical reasons, will never be done. Does in vitro resistance translate into clinical failures? Should changing resistance patterns modify our choice of therapy for CAP or for suspected pneumococcal pneumonia? This review discusses several facets, including mechanisms of antimicrobial resistance among specific antibiotic classes, epidemiology and spread of antimicrobial resistance determinants regionally and worldwide, risk factors for acquisition and dissemination of resistance, the impact of key international clones displaying MDR, the clinical impact of antimicrobial resistance, and strategies to limit or curtail antimicrobial resistance among this key respiratory tract pathogen.     

呼吸重症监护病房多重耐药鲍曼不动杆菌耐药基因研究

目的 观察我院呼吸重症监护病房(RICU)临床分离多重耐药鲍曼不动杆菌β-内酰胺酶基因和消毒剂耐药基因qacE△1-sul1存在状况.方法 收集RICU分离多重耐药鲍曼不动杆菌16株,采用PCR方法检测8种β-内酰胺酶基因(TEM、SHV、PER、DHA、IMP、VIM、OXA-23、OXA-24)和消毒剂耐药基因(qacE△1-sul1)共9种基因.采用多基因聚类分析方法进行多重耐药菌株亲缘性分析.结果 16株多重耐药鲍曼不动杆菌中blaOXA-23阳性5株(31.25%),blaTEM阳性2株(12.50%),blaDHA 2株(12.50%),blaOXA-24 1株(6.25%),blaPER 1株(6.25%).blaSHV、blaIMP、blaVIM均未检出,消毒剂耐药基因检测qacE△1-sull阳性16株(100.00%).多基因聚类分析发现存在克隆传播现象.结论 我院RICU多重耐药鲍曼不动杆菌携带多种β-内酰胺酶基因,消毒剂耐药基因携带率高,聚类分析显示存在克隆传播现象,应引起临床重视.