3-氨基苯酚硼酸增强试验检测同时产AmpC酶和ESBLs菌株

摘要：目的：评价3-氨基苯酚硼酸（APB）增强试验同时检测大肠埃希菌和肺炎克雷伯菌产ESBLs和AmpC酶的效果。 方法：用加APB的头孢他啶、头孢噻肟、头孢他啶/克拉维酸、头孢噻肟/克拉维酸纸片检测31株产质粒型AmpC酶的大肠埃希菌和肺炎克雷伯菌合并产ESBLs情况,并与仪器法、经典方法(K-B法)检测ESBLs结果进行对比。同时采用此方法检测239株大肠埃希菌和肺炎克雷伯菌产ESBLs酶的情况。并采用加与不加APB的头孢他啶、头孢噻肟、头孢西丁检测其是否高产AmpC酶。 结果：31株产质粒型AmpC酶的大肠埃希菌和肺炎克雷伯菌中合并产ESBLs酶的菌株,经典方法漏检ESBLs 6株,漏检率23.08%(6/26)。而Vitek-60微生物仪漏检率达65.38%（17/26）。239株菌中检测出产AmpC酶10株（4.18%）。其中有5株同时产ESBLs 酶和AmpC酶;产ESBLs 酶106株（44.35%）。 结论：目前产ESBLs、高产AmpC酶的菌株检出率较高,APB增强法能快速、简便、较准确检测同时产ESBLs和AmpC酶菌株,适合临床实验室应用。     

改良的纸片表型筛选法用于AmpC酶的检测

目的 建立并评价一种检测大肠埃希菌和肺炎克雷伯菌产AmpC酶的新方法.方法 采用改良的纸片表型筛选法,以头孢西丁三维试验和多重PCR法作为对照,对临床分离的耐第三代头孢菌素的164株大肠埃希菌和40株肺炎克雷伯菌进行AmpC酶的检测.结果 164株大肠埃希菌中,改良的纸片表型筛选法检出8株产AmpC酶的阳性菌株（8/164,4.88%）,其中有2株同时产ESBLs酶;40株肺炎克雷伯菌中未检出产AmpC酶菌株,但检出2株（2/40,5.00%）诱导产AmpC酶菌株.头孢西丁三维试验在大肠埃希菌中检出AmpC酶阳性菌株8株（8/164,4.88%）,在肺炎克雷伯菌中未检出产AmpC酶株.多重PCR法检出大肠埃希菌AmpC酶耐药基因阳性9株（9/164,5.49%）,肺炎克雷伯菌阳性2株（2/40,5.00%）.结论 改良的纸片表型筛选法可用于检测大肠埃希菌和肺炎克雷伯菌产AmpC酶和诱导产酶株,并可同时检测产ESBLs酶菌株,该法操作简便、结果可靠、无需特殊仪器,可在普通临床实验室应用.     

大肠埃希菌和肺炎克雷伯菌质粒AmpC酶基因型及流行病学分析

目的研究大肠埃希菌和肺炎克雷伯菌中产质粒型AmpC酶株的比率、酶的基因型及其流行病学状况。方法收集本院、福建省立医院两家医院2004年9月至2005年3月的67株耐头孢西丁不重复大肠埃希菌和肺炎克雷伯菌，用酶提取物三维试验检测高产AmpC酶；抽提高产AmpC酶株质粒，用PCR及产物序列分析确定质粒AmpC酶和13内酰胺酶的基因型；质粒转化试验定位耐药基因；ERIC-PCR指纹图确定产酶株间的同源关系。结果福州两家医院耐头孢西丁菌中产质粒型AmpC酶的发生率，大肠埃希菌分别为16．7％和10．5％，肺炎克雷伯菌则分别为8．0％和0。2株肺炎克雷伯菌产DHA-1型、4株大肠埃希菌产CMY-2型、1株大肠埃希菌产CMY-22型质粒AmpC酶；5株产CMY型AmpC酶的大肠埃希菌还分别同时产CTX—M-14、CTX—M-27、TEM-144和TEM-1型13内酰胺酶。7株菌中，1株肺炎克雷伯菌和3株大肠埃希菌可将头孢西丁耐药性转移给受体菌。7株产酶菌ERIC—PCR指纹图显示，2株肺炎克雷伯菌来自相同克隆，其余菌株来自不同克隆。结论福州地区发现产DHA-1型AmpC酶肺炎克雷伯菌和产CMY-2型及CMY-22型AmpC酶大肠埃希菌。CMY-22型AmpC酶和TEM-144型13内酰胺酶是国内外首次报道，GenBank登录号为DQ256079和DQ2560S0。     

大肠埃希氏菌和肺炎克雷伯氏菌AmpC酶的检测

目的了解我院大肠埃希氏菌和肺炎克雷伯氏菌产AmpC酶情况。方法按NCCLS推荐的超广谱β-内酰胺酶(ESBLs)确证试验,对369株大肠埃希氏菌和肺炎克雷伯氏菌进行ESBLs酶的检测,并用改良三维试验、三维试验抑制试验及AmpC酶诱导试验对表型可疑产AmpC酶的菌株进行检测。结果73株表型可疑产AmpC酶的菌株中检出34株产AmpC酶,大肠埃希氏菌24株,肺炎克雷伯氏菌10株,其中有5株大肠埃希氏菌2、株肺炎克雷伯氏菌同时产ESBLs酶。2株肺炎克雷伯氏菌诱导产AmpC酶。结论产生AmpC酶是大肠埃希氏菌和肺炎克雷伯氏菌对头孢类抗生素耐药的又一重要机制,实验室应对其检测和监测给予足够重视,以指导临床合理选用抗生素、减缓对细菌耐药的选择性压力、避免医院感染的发生和流行。     

大肠埃希菌和肺炎克雷伯菌质粒β—内酰胺酶的筛选

目的：了解大肠埃菌和肺炎克雷伯菌的质粒介导的β-内酰胺酶的分布,表型及其检测方法,方法：经头孢泊肟初筛,用NCCLS确证试验检测超广谱β-内酰胺酶（ESBL）和用头孢西丁三相试验检测质粒AmpC.结果341株大肠埃希菌和肺炎克雷伯菌中经常规药敏试验筛选出164株（48．1％）头孢泊肟（CPD）的MIC＞1μg/ml,对其中的102株进行检测,结果产ESBL的有64株,头孢西丁三相试验阳性者有6株。结大肠埃钸菌和肺炎克雷伯菌的质粒β-内酰胺酶以ESBL为主（30．2％）,质粒AmpCs仅占2．8％。     

大肠埃希菌中质粒AmpC型β内酰胺酶基因型的检测

目的 :研究大肠埃希菌和肺炎克雷伯菌中AmpC型 β内酰胺酶的基因型。 方法 :收集对头孢西丁不敏感的 4 2株大肠埃希菌和肺炎克雷伯菌 ,用酶提取物三维试验检测AmpC酶 ;用等电聚焦电泳、接合试验、聚合酶链反应 (PCR)确定AmpC型酶的表型和基因型。结果 :16株菌高产AmpC酶 ,其中 11株同时产超广谱 β内酰胺酶 (ESBLs) ;这 16株菌对亚胺培南敏感 ,5株只产AmpC酶的菌对头孢吡肟敏感 ;等电聚焦电泳发现这 16株菌产生 2～ 5种酶 ,且都有一个能为氯唑西林抑制的、等电点>7.8的酶带 ;1株大肠埃希菌通过接合试验可将头孢西丁耐药性传递给受体菌 ;PCR扩增和测序证实其为质粒介导的ACT 1型AmpC酶。 结论 :2 0 0 0年我院分离的对头孢西丁不敏感的 4 2株革兰阴性杆菌中证实有 15株大肠埃希菌和 1株肺炎克雷伯菌产AmpC酶 ,并在国内首次发现 1株大肠埃希菌产ACT 1型质粒AmpC酶。     

产超广谱β内酰胺酶肺炎克雷伯菌和大肠埃希菌耐药性检测

【目的】了解临床分离肺炎克雷伯菌和大肠埃希菌超广谱β内酰胺酶（ESBLs）产生情况及耐药性。【方法】用VITEK32型全自动细菌鉴定分析系统对临床标本中分离的123株肺炎克雷伯菌和大肠埃希菌进行鉴定，ESBLs采用双纸片扩散法检测，采用KB纸片法选用13种抗菌药物进行药敏分析。【结果】产ESBLs肺炎克雷伯菌和大肠埃希菌检出率分别为46．2％和40．5％，以呼吸道感染为主占50％。产ESBLs菌对多种抗生素的耐药性较非产酶株显著升高，对β一内酰胺类喹诺酮类和青霉素类抗生素几乎全部耐药，但对亚胺培南的敏感性为100％，对头孢西丁的敏感率〉60％。【结论】治疗产ESBLs肺炎克雷伯菌和大肠埃希菌首选是碳青霉烯类和头霉素类；应重视ESBLs的检测，合理使用抗生素。     

大肠埃希菌ESBLs和AmpC酶的检测及耐药性分析

目的 分析大肠埃希菌产ESBLs和AmpC酶的检出情况及其对常用抗生素的耐药性.方法 收集临床无重复分离的161株大肠埃希菌,利用双纸片协同法检测ESBLs,Tris-EDTA纸片法测AmpC酶,K-B法测定细菌对抗生素的耐药性.结果 161株大肠埃希菌共检出产酶菌(包括单产ESBLs、单产AmpC酶、同时产ESBLs和AmpC酶)63株,占39.1%,其中以单产ESBLs为主.产酶菌耐药性明显高于非产酶菌,以产AmpC酶菌更为严重;所有菌株对亚胺培南均敏感.结论 临床分离的大肠埃希菌产酶菌株普遍,耐药率高,应引起临床重视.治疗产酶菌株引起的感染首选碳青霉稀类抗生素.     

持续高产AmpC酶的检测及其临床意义

目的调查持续高产AmpC酶在大肠埃希菌、肺炎克雷伯菌和鲍曼不动杆菌中的携带率和流行趋势.方法用头孢西丁药敏纸片法（K-B法）和头孢西丁三维试验作AmpC酶的筛选、确证试验,对AmpC酶阳性者进行质粒接合试验.结果 11种抗生素中亚胺培南的抗菌活性最强,耐药率仅为1.1%.头孢西丁纸片筛选法阳性率为84.4%,三维试验阳性率为32.2%.与三维试验相比,纸片筛选法总的假阳性率为54.4%,两种方法差异具有高度显著性（P〈0.001）.AmpC酶、超广谱β-内酰胺酶（ESBLs）、AmpC酶＋ESBLs阳性率分别为24.4%、54.4%和7.8%,其中以肺炎克雷伯菌AmpC酶阳性率最高,达33.3%.大肠埃希菌ESBLs阳性率最高,达70.0%.29株AmpC酶阳性菌中,5株耐药质粒转移成功.结论 AmpC酶可由染色体或质粒介导,但以染色体介导为主.头孢西丁三维试验可准确检出持续高产AmpC酶,对指导临床用药有积极意义.     

重症监护病房患者大肠埃希菌和肺炎克雷伯菌多重耐药性分析

目的 探讨重症监护病房（ICU）患者大肠埃希菌和肺炎克雷伯菌多重耐药性,为临床提供治疗依据.方法 回顾分析ICU病房患者标本中分离的280株大肠埃希菌和肺炎克雷伯菌耐药性.结果 大肠埃希菌和肺炎克雷伯菌多数来自痰标本,其中产超广谱β-内酰胺酶（ESBLs）136株（48.6%）,产AmpC β-内酰胺酶10株（3.6%）,同时产两种酶2株（1.1%）.抗生素耐药显示：携带产 ESBLs和AmpC酶菌株都有较高耐药性;产 ESBLs菌株对亚胺培南较为敏感（94.8%）,其次是哌拉西林/他唑巴坦（36.1%）;而AmpC酶菌株对亚胺培南的敏感率仅为48.4%.结论 ICU病房大肠埃希菌和肺炎克雷伯菌均有较高的耐药性,因此必须合理应用抗生素.     

Evaluation of phenotypic screening methods for detecting plasmid-mediated AmpC beta-lactamases-producing isolates of Escherichia coli and Klebsiella pneumoniae

Detection of plasmid-mediated (P-M) AmpC beta-lactamase-producing isolates is considered critical for epidemiologic studies and hospital infection control, but the documents of the Clinical and Laboratory Standards Institute do not contain any recommendation for the phenotypic detection. In this study, phenotypic detection methods, cefoxitin-Hodge test and induction test, were evaluated using cefoxitin-resistant Escherichia coli and Klebsiella pneumoniae isolates. The cefoxitin-Hodge test detected all bla(CMY-10), and 97.4% of bla(CMY-2) allele-positive isolates, but only 57.3% of bla(DHA-1) allele-positive isolates. Induction test with an aztreonam and an amoxicillin-clavulanic acid disk was more sensitive than with cefoxitin disk, which detected 86.6% of bla(DHA-1) allele-positive isolates. These phenotypic tests should be useful to screen P-M AmpC beta-lactamase-producing E. coli and K. pneumoniae isolates.     

同时产ESBLs和AmpC酶菌株的表型检测及其意义

目的：探讨同时产ESBLs和AmpC酶菌株的表型检测方法。方法：应用VITEK2微生物鉴定系统鉴定临床分离的细菌标本，用双纸片增效确证试验进行验证。对产ESBLs的细菌，用头孢西丁筛查试验、三维试验、Tris—EDTA法和粗提酶检测法检测AmpC酶。结果：365株肠杆菌科细菌中检出ESBLs菌株93株（25．5％），CLSI确证试验阳性菌株88株（94．6％）。头孢两丁筛查阳性的26株菌中检出同时产ESBLS和AmpC酶菌1株。结论：应用表型检测法可在临床标本中检出同时产ESBLS和AmpC酶菌株；以CSLI确证试验检测ESBLs，以酶粗提物直接测定法、Tris—EDTA法进行AmpC酶检测，对同时产两种酶的临床菌株进行筛查。其操作易行、结果可靠、便于临床推广应用。     

大肠埃希菌和肺炎克雷伯菌质粒β-内酰胺酶的筛选

目的　了解大肠埃希菌和肺炎克雷伯菌的质粒介导的β-内酰胺酶的分布、表型及其检测方法。　方法　经头孢泊肟初筛,分别用NCCLS确证试验检测超广谱β-内酰胺酶(ESBL)和用头孢西丁三相试验检测质粒AmpC。　结果　341株大肠埃希菌和肺炎克雷伯菌中经常规药敏试验筛选出164株(48.1%)头孢泊肟(CPD)的MIC＞1μg/ml,对其中的102株进行检测,结果产ESBL的有64株,头孢西丁三相试验阳性者有6株。　结论　大肠埃希菌和肺炎克雷伯菌的质粒β-内酰胺酶以ESBL为主(30.2%),质粒AmpCs仅占2.8%。     

Evaluation of the MicroScan ESBL plus confirmation panel for detection of extended-spectrum beta-lactamases in clinical isolates of oxyimino-cephalosporin-resistant Gram-negative bacteria

OBJECTIVE: We aimed to assess the performance of the MicroScan ESBL plus confirmation panel using a series of 87 oxyimino-cephalosporin-resistant Gram-negative bacilli of various species. METHODS: Organisms tested included 57 extended-spectrum beta-lactamase (ESBL) strains comprising Enterobacter aerogenes (3), Enterobacter cloacae (10), Escherichia coli (11), Klebsiella pneumoniae (26), Klebsiella oxytoca (3) and Proteus mirabilis (4). Also included were 30 strains resistant to oxyimino cephalosporins but lacking ESBLs, which were characterized with other resistance mechanisms, such as inherent clavulanate susceptibility in Acinetobacter spp. (4), hyperproduction of AmpC enzyme in Citrobacter freundii (2), E. aerogenes (3), E. cloacae (3), E. coli (4), Hafnia alvei (1) and Morganella morganii (1), production of plasmid-mediated AmpC beta-lactamase in K. pneumoniae (3) and E. coli (3) or hyperproduction of K1 enzyme in K. oxytoca (6). RESULTS: The MicroScan MIC-based clavulanate synergy correctly classified 50 of 57 ESBL strains as ESBL-positive and 23 of 30 non-ESBL strains as ESBL-negative (yielding a sensitivity of 88% and a specificity of 76.7%, respectively). False negatives among ESBL producers were highest with Enterobacter spp. due to masking interactions between ESBL and AmpC beta-lactamases. False-positive classifications occurred in two Acinetobacter spp., one E. coli producing plasmid-mediated AmpC beta-lactamase and two K. oxytoca hyperproducing their chromosomal K1 beta-lactamase. CONCLUSION: The MicroScan clavulanate synergy test proved to be a valuable tool for ESBL confirmation. However, this test has limitations in detecting ESBLs in Enterobacter spp. and in discriminating ESBL-related resistance from the K1 enzyme and from inherent clavulanate susceptibility in Acinetobacter spp.     

Detection and reporting beta-lactam resistance phenotypes in Escherichia coli and Klebsiella pneumoniae: a multicenter proficiency study in Spain

The ability of 57 Spanish microbiology laboratories in detecting and reporting beta-lactam resistance phenotypes in Escherichia coli and Klebsiella pneumoniae was evaluated. Laboratories received 6 well-characterized isolates expressing the most widespread extended-spectrum beta-lactamases (ESBLs) in Spain (4 CTX-M type, 1 TEM type, and 1 SHV type), 3 isolates producing AmpC-type enzymes (2 plasmid mediated and 1 E. coli hyperproducing its chromosomal AmpC), and 3 quality control strains. Ninety-one percent of laboratories recognized all ESBL producers correctly, and therefore, low error rates were observed when testing cephalosporins and aztreonam. The highest error rates were observed with combinations of penicillin plus beta-lactamase inhibitor, although more than 60% of cases were due to the interpretation made by the microbiologists. Correct recognition of all AmpC beta-lactamase-producing strains occurred in only 47.4% of laboratories. These isolates were wrongly reported as ESBL producers and penicillinase hyperproducers in 7.6 % and 5.8% of cases, respectively. Detection of the AmpC-type phenotype by Spanish laboratories needs to be improved.     

耐头孢西丁肺炎克雷伯菌ESBLs和AmpC酶的检测及耐药基因分析

目的 了解浙江省台州地区肺炎克雷伯菌ESBLs和AmpC -内酰胺酶产生情况及AmpC酶的耐药基因型别特征。 方法 采用VITEK-AMS60全自动细菌鉴定仪鉴定细菌,按CLSI推荐的确证试验检测ESBLs,采用头孢西丁纸片扩散法筛选疑产AmpC酶阳性菌株,通过酶粗提物三维试验确证产AmpC酶,并经PCR测序等实验分析该菌株的基因型。 结果 在对头孢西丁不敏感的86株肺炎克雷伯菌中,ESBLs和AmpC酶检出率分别为88.37%和77.91%;以同产ESBLs和AmpC酶为主要形式,占47.67%,单产ESBLs和单产AmpC酶分别占40.70%和30.23%;AmpC酶阳性菌株的耐药基因型:62株为DHA-1型、5株为ACT-1型。 结论 台州地区肺炎克雷伯菌产ESBLs和AmpC酶检出率较高,AmpC酶以DHA-1型为主。     

Phenotypic detection of extended-spectrum and AmpC beta-lactamases by a new spot-inoculation method and modified three-dimensional extract test: comparison with the conventional three-dimensional extract test

OBJECTIVES: To develop an easy, rapid and reproducible spot-inoculation method for phenotypic detection of extended-spectrum beta-lactamases (ESBLs) and AmpC beta-lactamases and to make the existing three-dimensional extract test more convenient for use in routine diagnostic laboratories. METHODS: ESBL and AmpC producing and non-producing isolates of Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa, as identified by the conventional three-dimensional extract test, were used to evaluate the modified procedures. Whole bacterial cells and freeze-thaw preparations, as beta-lactamase sources, were strategically applied to culture plates near ceftazidime and cefoxitin discs on a lawn inoculum of E. coli ATCC 25922. Technical variations of the test included placing the beta-lactamase-containing inoculum into slits, wells and trenches, or onto the surface as spots at varying distances from the discs, and adding clavulanate or cloxacillin to the three-dimensional inoculum to confirm the presence of ESBLs and AmpC beta-lactamases, respectively. RESULTS: All the methods adopted for ESBL and AmpC detection by using the whole bacterial cells gave positive results. However, the best results were given by the spot-inoculation method. In modifications using the enzymic extracts, the enhanced growth of surface organisms was better appreciated in the designed modifications compared with the conventional methods. CONCLUSIONS: The method described here is simple and cost-effective. Furthermore, up to 16 isolates may be tested on a single culture plate, thus it is a less labour-intensive and more economic technique than other reported phenotypic methods.     

Epidemiology of conjugative plasmid-mediated AmpC beta-lactamases in the United States

A sample of 752 resistant Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli strains from 70 sites in 25 U.S. states and the District of Columbia was examined for transmissibility of resistance to ceftazidime and the nature of the plasmid-mediated beta-lactamase involved. Fifty-nine percent of the K. pneumoniae, 24% of the K. oxytoca, and 44% of the E. coli isolates transferred resistance to ceftazidime. Plasmids encoding AmpC-type beta-lactamase were found in 8.5% of the K. pneumoniae samples, 6.9% of the K. oxytoca samples, and 4% of the E. coli samples, at 20 of the 70 sites and in 10 of the 25 states. ACT-1 beta-lactamase was found at eight sites, four of which were near New York City, where the ACT-1 enzyme was first discovered; ACT-1 beta-lactamase was also found in Massachusetts, Pennsylvania, and Virginia. FOX-5 beta-lactamase was also found at eight sites, mainly in southeastern states but also in New York. Two E. coli strains produced CMY-2, and one K. pneumoniae strain produced DHA-1 beta-lactamase. Pulsed-field gel electrophoresis and plasmid analysis suggested that AmpC-mediated resistance spread both by strain and plasmid dissemination. All AmpC beta-lactamase-containing isolates were resistant to cefoxitin, but so were 11% of strains containing transmissible SHV- and TEM-type extended-spectrum beta-lactamases. A beta-lactamase inhibitor test was helpful in distinguishing the two types of resistance but was not definitive since 24% of clinical isolates producing AmpC beta-lactamase had a positive response to clavulanic acid. Coexistence of AmpC and extended-spectrum beta-lactamases was the main reason for these discrepancies. Plasmid-mediated AmpC-type enzymes are thus responsible for an appreciable fraction of resistance in clinical isolates of Klebsiella spp. and E. coli, are disseminated around the United States, and are not so easily distinguished from other enzymes that mediate resistance to oxyimino-beta-lactams.     

重症监护病房(ICU)两种产超广谱B-内酰胺酶细菌耐药性动态分析

目的对医院ICU(重症监护病房)两种常见产超广谱B-内酰胺酶(ESBLs)细菌的检出率及耐药性进行动态观察,为指导临床合理使用抗生素提供依据。方法对我室2006至2009年从ICU标本分离的479株肺炎克雷伯菌和491株大肠埃希菌采用纸片协同试验和双纸片确证试验检测其ESBLs,并用纸片扩散法进行药敏试验。结果四年来大肠埃希菌产ESBLs阳性率从41.6%上升至58.4%;肺炎克雷伯菌产ESBLs阳性率从29.0%上升至35.3%。产ESBLs株对常用抗菌药物的耐药率明显高于非产ESBLs株,但对碳青霉烯类抗菌药物都敏感。结论 4年来,大肠埃希菌、肺炎克雷伯菌中ESBLs阳性率逐年升高,对产ESBLs菌株的治疗应首选含酶抑制剂的抗生素、非B内酰胺类敏感的抗生素或碳青霉烯类抗菌药物。     

Detection of extended-spectrum beta-lactamases in members of the family Enterobacteriaceae: comparison of the double-disk and three-dimensional tests.

The three-dimensional and clavulanate double-disk potentiation tests were compared as procedures for the detection of extended-spectrum beta-lactamase production in 32 strains of Escherichia coli and Klebsiella pneumoniae, 31 of which produced TEM-1, TEM-2, TEM-3, TEM-4, TEM-5, TEM-7, TEM-8, TEM-9, TEM-10, TEM-12, TEM-101, SHV-1, SHV-2, SHV-3, SHV-4, SHV-5, CAZ-2, MIR-1, or an unidentified extended-spectrum beta-lactamase with a pI of 5.95, with some strains producing multiple beta-lactamases. The three-dimensional test, which was performed in conjunction with a routine disk diffusion test, detected extended-spectrum beta-lactamase production in 26 of 28 (93%) of the strains that produced extended-spectrum beta-lactamases. The clavulanate double-disk potentiation test detected extended-spectrum beta-lactamases in only 22 of the 28 strains (79%) when it was performed as currently recommended. The three-dimensional test, when performed in conjunction with the disk diffusion test, offered the advantages of providing simultaneous information about both antibiotic susceptibility and extended-spectrum beta-lactamase production, coupled with a greater sensitivity and earlier detection of extended-spectrum beta-lactamases.