儿童呼吸道感染常见革兰阳性致病菌耐药性分析

目的 通过奉贤区中心医院市六分院儿童呼吸道感染常见革兰阳性致病菌（肺炎链球菌、A族乙型溶血性链球菌、金黄色葡萄球菌）研究,了解患儿呼吸道感染常见革兰阳性致病菌耐药性情况[1].方法 2006年1月至2009年12月期间,儿科呼吸道感染患儿咽分泌物培养,其中35株金黄色葡萄球菌、30株肺炎链球菌、15株A族乙型溶血性链球菌,采用K-B纸片法进行抗生素敏感性检测.结果 35株金黄色葡萄球菌对氨苄西林耐药率为86%,对头孢拉啶耐药率为79%,对青霉素耐药率为71%,对苯唑西林耐药率为8%,而且多重耐药问题很严重;30株肺炎链球菌对红霉素耐药率为62%,对青霉素不敏感3株,为10%,多重耐药率高达90%;15株A族乙型溶血性链球菌,对红霉素耐药率为80%,对青霉素及氨苄西林敏感.结论 儿童呼吸道感染常见致病菌的耐药性情况不乐观.肺炎链球菌及A族乙型溶血性链球菌对红霉素耐药性很高;发现金黄色葡萄球菌多耐药问题很严重.儿童呼吸道感染时,应尽量避免使用非β-内酰胺类抗生素.     

13种抗菌药物对肺炎链球菌的体外抗菌活性分析

目的 探讨常用抗菌药物对临床分离的肺炎链球菌的体外抗菌活性.方法 用全自动微生物分析系统VITEK-2Compact对临床分离的154株肺炎链球菌进行鉴定和药敏试验.结果 药敏试验测得154株肺炎链球菌有85株（54.5%）对青霉素不敏感,其中72株（46.8%）对青霉素高度耐药,13株（8.4%）对青霉素中度耐药;测得氯霉素、美诺培南、头孢噻肟、头孢曲松、阿莫西林、复方新诺明、四环素、红霉素的耐药率分别为3.4%、16.2%、19.5%、20.8%、25.3%、68.8%、84.4%、90.9%;所有菌株对左旋氧氟沙星、莫西沙星、利奈唑胺、万古霉素敏感;135株对3种或3种以上抗生素耐药,多重耐药率为87.7%.结论 肺炎链球菌对左旋氧氟沙星、莫西沙星、利奈唑胺、万古霉素100%敏感,抗菌活性高;对氯霉素、美诺培南、头孢噻肟、头孢曲松、阿莫西林耐药率也较低,对青霉素、复方新诺明、四环素、红霉素的耐药率高,尤其是青霉素不敏感株和多重耐药菌株多见,应引起临床重视.     

湘潭市中心医院社区获得性肺炎住院患儿肺炎链球菌的耐药性研究

目的了解湘潭市中心医院因社区获得性肺炎住院的患儿肺炎链球菌(SP)的耐药情况。方法对本院2010-2011年住院患儿分离的115株SP进行分析,采用K-B纸片琼脂扩散法及浓度梯度法(E测试)检测SP对青霉素、头孢曲松、红霉素、克林霉素、左氧氟沙星、万古霉素、利奈唑胺、复方磺胺甲噁唑的耐药性。结果 115株SP中青霉素敏感肺炎链球菌(PSSP)占86.1%,青霉素中介肺炎链球菌(PISP)占7.8%,青霉素耐药肺炎链球菌(PRSP)占6.1%。SP对红霉素、克林霉素及复方磺胺甲噁唑的耐药率分别为95.6%、94.8%和73.9%,左氧氟沙星的耐药率为1.7%,头孢曲松的耐药率为6.9%,未发现对万古霉素及利奈唑胺耐药的SP菌株。结论本院分离的SP对儿科常用抗生素青霉素及头孢曲松钠仍高度敏感,但对大环内酯类抗生素红霉素、林可酰胺类抗生素克林霉素耐药情况严重。     

2005～2006年烟台地区儿童肺炎链球菌、流感嗜血杆菌抗生素敏感性调查

目的:了解烟台地区儿童肺炎链球菌(Sp)、流感嗜血杆菌(Hi)对常用抗生素的敏感性.方法:对2005～2006年在烟台毓璜顶医院住院的肺炎患儿采取痰标本,采用ATB Expression自动细菌鉴定仪行痰培养;分离出Sp及Hi菌株,并行抗生素敏感性试验.结果:939例肺炎患儿分离Sp 112株,Hi 77株.Sp对常用抗生素耐药率为:青霉素92株(82.2%)、阿莫西林32株(28.6%)、红霉素111株(99.1%)、复方新诺明109株(97.3%)、万古霉素0株(0%).Hi对常用抗生素耐药率为:氨苄西林36株(46.8%),复方阿莫西林8株(10.4%),头孢克洛14株(18.2%),头孢呋辛6株(7.8%),第三代头孢菌素5株(6.5%),复方新诺明69株(89.6%).结论:烟台地区儿童Sp、Hi耐药形势严峻.Sp对青霉素、红霉素、复方新诺明等多重耐药.Hi对氨苄西林、复方新诺明耐药率高,对第三代头孢菌素、头孢呋辛、阿莫西林克拉维酸敏感性较高.     

2004—2009年益阳市中心医院临床分离肺炎链球菌的血清型/群分布及耐药性监测

目的了解近5年益阳市中心医院临床分离肺炎链球菌的血清型/群分布及耐药趋势,为临床合理使用抗生素提供参考。方法以2004—2009年期间临床分离的822株肺炎链球菌为研究对象,采用荚膜肿胀试验进行血清分型/群,E-test检测菌种对青霉素、头孢呋辛、头孢地尼、头孢克罗、红霉素、四环素、左氧氟沙星、万古霉素等8种抗生素的敏感性。结果 2004年青霉素不敏感肺炎链球菌(PNSP)的分离率为49.4%,并呈逐年上升趋势,至2006年PNSP分离率高达67.8%,2009年下降至51.5%。822株肺炎链球菌最常见的型/群是19群,其次是23、6、14、3群和其他。PNSP在6种血清型/群中所占的比例在2004—2009年期间无显著性变化(P>0.05)。肺炎链球菌对其他β内酰胺类抗生素的非敏感趋势类似青霉素,对红霉素、四环素的非敏感率始终在60%以上,其中青霉素耐药肺炎链球菌(PRSP)对红霉素和四环素几乎100%耐药,对左氧氟沙星、万古霉素的非敏感率均<3%。结论临床分离肺炎链球菌以19、23、6、14、3群常见;对β内酰胺类抗生素的非敏感率自2007年呈下降趋势,且对左氧氟沙星、万古霉素始终具有较高的敏感性。     

2004～2009年临床分离肺炎链球菌的血清型/群分布及耐药性监测

目的：了解当前本院临床分离肺炎链球菌的血清型/群分布及耐药趋势,为临床合理使用抗生素提供参考。方法：以2004～2009年临床分离的822株肺炎链球菌为研究对象,采用荚膜肿胀试验进行血清分型/群,E-test检测菌种对青霉素、头孢呋辛、头孢地尼、头孢克罗、红霉素、四环素、左氧氟沙星、万古霉素等8种抗生素的敏感性。结果：2004年青霉素不敏感肺炎链球菌（PNSP）的分离率为49.4%,并呈逐年上升趋势,至2006年PNSP分离率高达67.8%,2009年下降至51.0%。822株肺炎链球菌最常见的型/群是19群,其次是23、6、14、3、其他。PNSP在6种血清型/群中所占的比例在2004～2009年期间无显著性变化（P〉0.05）。肺炎链球菌对其他β内酰胺类抗生素的非敏感趋势类似青霉素,对红霉素、四环素的非敏感率始终在60%以上,其中青霉素耐药肺炎链球菌（PRSP）对红霉素和四环素几乎100%耐药,对左氧氟沙星、万古霉素的非敏感率均〈3%。结论：临床分离肺炎链球菌以19群、23群、6群、14群、3群常见;对β内酰胺类抗生素的非敏感率自2007年呈下降趋势,且对左氧氟沙星、万古霉素始终具有较高的敏感性。     

272例肺炎链球菌的耐药性分析

目的：探讨儿童感染肺炎链球菌的耐药性及流行情况。方法：对本院272株肺炎链球菌,采用纸片扩散法（K-B法）对8种抗生素进行耐药性检测。结果：肺炎链球菌在对红霉素、苯唑西林、复方磺胺甲唑、氧氟沙星、四环素、万古霉素、氯霉素和利福平耐药率分别为80.5%、84.6%、89.0%、6.2%、67.3%、0%、12.0%、38.2%。结论：提示临床了解肺炎链球菌耐药菌株的检出率及多重耐药的特点,对减少耐药菌株的产生,更好地合理使用抗生素有着重要的意义。     

1330株临床分离革兰阳性菌耐药性分析

目的 了解临床分离的革兰阳性菌对不同抗菌药物的耐药情况,为临床医师及时提供抗生素的耐药动向与耐药变迁为临床抗感染治疗提供选药依据.方法 用苯唑西林检测葡萄球菌临床分离株的敏感性,用纸片扩散法检测革兰阳性菌对四环素、红霉素、庆大霉素、氨苄青霉素、环丙沙星、头孢吡肟、复方磺胺甲噁唑、万古霉素、替考拉宁、利福平、克林霉素等抗菌药物的耐药结果.用E-test法检测对苯唑西林耐药的肺炎链球菌青霉素的MIC值.结果 1330株革兰阳性菌中耐甲氧西林的葡萄球菌对抗菌药物的耐药率显著高于对甲氧两林敏感的葡萄球菌.肠球菌属以粪肠球菌和屎肠球菌检出率最高,粪肠球菌对呋喃妥因、氨苄西林耐药率较低,屎肠球菌耐药性较强,仅对氯霉素、四环素耐药率较低.肺炎链球菌对四环素、克林霉素、红霉素有较高的耐药率,青霉素不敏感肺炎链球菌(PNSSP)的E-test检测结果以中介菌株为主,PNSSP的MIC值最高达到6μg/mL.结论 葡萄球菌、肺炎链球菌对万古霉素全部敏感,有仅发现1株耐万古霉素的屎肠球菌,万古霉素是临床治疗重症革兰阳性菌感染的首选药物.加强耐药性监测对指导临床合理使用抗菌药物具有重要意义.     

202株肺炎链球菌感染的临床分布及耐药性分析

目的调查大庆某医院临床分离的202株肺炎链球菌的临床分布特征及耐药状况,为临床合理用药提供依据。方法对2014年1月—2018年12月期间大庆某医院分离的202株肺炎链球菌进行回顾性分析。结果202株肺炎链球菌主要分离自呼吸道标本(痰61.4%、咽拭子20.3%)及血液标本(14.9%);感染者以儿童及中老年人为主(87.6%),患者主要来源于ICU(16.8%)、呼吸内科(15.3%)、耳鼻喉科(12.4%)及儿科(11.9%)。肺炎链球菌对红霉素(99.3%)、四环素(91.3%)、复方磺胺甲噁唑(74.0%)耐药性较严重,青霉素的耐药率为37.1%,对三代头孢菌素(头孢曲松、头孢噻肟)、氯霉素、氟喹诺酮类及厄他培南较敏感,万古霉素和利奈唑胺全部敏感。结论肺炎链球菌以呼吸系统感染为主,感染人群以儿童及中老年人多见。肺炎链球菌对四环素、红霉素及复方磺胺甲噁唑耐药严重,临床应根据药敏结果合理使用抗菌药物治疗。     

272例肺炎链球菌的耐药性分析

目的:探讨儿童感染肺炎链球菌的耐药性及流行情况。方法:对本院272株肺炎链球菌,采用纸片扩散法(K－B法)对8种抗生素进行耐药性检测。结果:肺炎链球菌在对红霉素、苯唑西林、复方磺胺甲(口恶)唑、氧氟沙星、四环素、万古霉素、氯霉素和利福平耐药率分别为80.5%、84.6%、89.0%、6.2%、67.3%、0%、12.0%、38.2%。结论:提示临床了解肺炎链球菌耐药菌株的检出率及多重耐药的特点,对减少耐药菌株的产生,更好地合理使用抗生素有着重要的意义。     

Prevalence of antimicrobial resistance in Haemophilus influenzae, Streptococcus pneumoniae, Moraxella catarrhalis and Streptococcus pyogenes: results of a multicentre study in Turkey

The in vitro activities of several antimicrobial agents against clinical isolates of Streptococcus pneumoniae (283), Haemophilus influenzae (272), Moraxella catarrhalis (179) and Streptococcus pyogenes (256) were determined in a multicentre study with the participation of five hospitals from four cities in Turkey. Penicillin resistance in S. pneumoniae was evaluated using the E-test and the remaining agents by disk diffusion. For S. pneumoniae overall 25.8% of the isolates were intermediately and 3.9% were highly resistant to penicillin and resistance to chloramphenicol, azithromycin and trimethoprim/sulphamethoxazole (TMP/SMX) was 3.8, 2.1 and 55.4%, respectively. Seven percent of H. influenzae produced beta-lactamase and all were susceptible to cefotaxime and azithromycin; the highest rate of resistance, 23.5%, was for TMP/SMX. Eighty-one percent of M. catarrhalis isolates produced beta-lactamase, 18.4% were resistant to TMP/SMX and all were susceptible to sulbactam/ampicillin combination. Resistance to chloramphenicol and azithromycin of S. pyogenes was 2.2 and 1.9%, respectively.     

Viridans group streptococci in blood culture isolates in a Swedish university hospital: antibiotic susceptibility and identification of erythromycin resistance genes

One hundred and twenty-nine isolates of viridans group streptococci in blood cultures from patients with septicaemia or endocarditis isolated between 1998 and 2003 were tested for antibiotic susceptibility to penicillin, ciprofloxacin, clindamycin, dalbavancin, daptomycin, erythromycin, linezolid, tigecycline, trimethoprim/sulphamethoxazole and vancomycin. Reduced susceptibility to penicillin (minimum inhibitory concentration (MIC) > or =0.25 microg/mL) was found in 18% of the isolates, and 4% of the strains were resistant to penicillin (MIC> or =4.0 microg/mL). Nineteen percent of the isolates had reduced susceptibility to erythromycin (MIC> or =0.5 microg/mL), among which ermB and mefA were found in 40% and 80%, respectively. Strains sequenced as Streptococcus mitis by rnpB had a high degree of non-susceptibility to erythromycin (32%) and penicillin (21%). The level of penicillin resistance in this Swedish study was lower compared with studies from other countries where the antibiotic pressure might be higher than in Sweden. Susceptibility to newer antibiotics was high; all strains were susceptible to dalbavancin, daptomycin, linezolid and vancomycin.     

淋球菌对大观霉素等5种抗生素的耐药性监测

目的　监测广州地区 2 0 0 2～ 2 0 0 3年度分离的淋球菌对青霉素、四环素、大观霉素、头孢曲松和环丙沙星的耐药性 ,分析耐药菌株的流行特点。方法　采用琼脂稀释法测定菌株对 5种抗生素的最小抑菌浓度(MIC) ,判断敏感性按 WHO西太区淋球菌耐药性监测统一标准。用纸片酸度法检测产 β-内酰胺酶淋球菌(PPNG)菌株。结果　 10 7株淋球菌中检出 96株对青霉素耐药 (89.7% ) ,产 β-内酰胺酶淋球菌 (PPNG) 2 0株(占 18.7% ) ;四环素耐药率为 6 5 .4 % ,其中质粒介导高度耐四环素淋球菌 (TRNG)为 31株 ,占 2 9.0 % ;环丙沙星耐药率为 88.8% ;未发现对大观霉素和头孢曲松耐药菌株。青霉素 四环素和环丙沙星的 MIC50 及MIC90 均已超过耐药标准 ,尤其是青霉素为甚 ,其 MIC50 及 MIC90 均超过耐药标准的 8倍和 6 4倍。结论　淋球菌对大观霉素和头孢曲松的敏感性较高 ,可作为治疗的首选药物 ,对青霉素、四环素和环丙沙星耐药率较高 ,提示对淋病的治疗作用差     

成都地区肺炎链球菌对抗菌药物的耐药性调查

目的 了解成都地区临床分离的肺炎链球菌的耐药性，为肺炎链球菌感染临床合理应用抗菌药物提供理论依据。方法 二倍琼脂稀释法测定11种抗菌药物对肺炎链球菌的最低抑菌浓度(MIC)。结果 91．94％菌株对青霉素敏感，8．06％中度耐药；88．71％菌株对SMZ／TMP敏感，11．29％中度耐药；肺炎链球菌对头孢呋辛、头孢噻肟、头孢毗肟、氧氟沙星、司帕沙星、美洛培南、万古霉素敏感率为100％；对红霉素、克林霉素耐药率相当高，分别达到62．90％和74．19％。结论 成都地区肺炎链球菌对青霉素耐药率较低，而对大环内酯类和克林霉素类耐药率较高。     

Prevalence of antimicrobial resistance among uropathogens causing acute uncomplicated cystitis in female outpatients in South Korea: a multicentre study in 2006

The Korean Association of Urogenital Tract Infection and Inflammation (KAUTII) conducted a survey of the antimicrobial susceptibility patterns of uropathogens responsible for female acute uncomplicated cystitis in South Korea in 2006. KAUTII has already reported similar data in 2002, which are compared with the results of the present study. This study was carried out with the participation of 22 hospitals in South Korea. A total of 301 isolates were obtained from female outpatients with acute uncomplicated cystitis. The antimicrobial susceptibilities to commonly prescribed drugs were determined. The most prevalent causative organism was Escherichia coli (71.1%), followed by enterococci (13.0%), coagulase-negative staphylococci (5.3%) and other species of Enterobacteriaceae (10.6%). Among all Enterobacteriaceae isolates, 31.4% were susceptible to ampicillin, 52.3% to ampicillin/sulbactam, 97.6% to piperacillin/tazobactam, 78.9% to ciprofloxacin, 80.3% to gatifloxacin, 86.8% to cefazolin, 99.6% to amikacin, 80.5% to gentamicin, 81.1% to tobramycin and 73.9% to trimethoprim/sulfamethoxazole (TMP/SMX). The resistance rates of E. coli to ciprofloxacin and gatifloxacin were 23.4% and 21.8%, respectively, and 12 (11.8%) of 102 suspected strains were confirmed as producing extended-spectrum beta-lactamase (ESBL). All the ESBL-producing strains were also resistant to fluoroquinolones. Enterobacteriaceae were highly susceptible to piperacillin/tazobactam and amikacin (>97%). There was a small increase in susceptibility to TMP/SMX (73.9%) compared with the same study in 2002 (62.1%). Similar to 2002, the high prevalence of resistance to ampicillin, ampicillin/sulbactam and TMP/SMX still exists. The increasing number of ESBL-producing or fluoroquinolones-resistant strains remains a serious clinical problem in South Korea.     

Penicillin resistant Streptococcus pneumoniae isolates in Harare, Zimbabwe

OBJECTIVE: To determine the susceptibility of Streptococcus pneumoniae isolates to penicillin and other antimicrobial drugs. DESIGN: This was a laboratory based study. SETTING: Department of Medical Laboratory Sciences, University of Zimbabwe and the Bacteriology Unit, Public Health Laboratories, Harare. SUBJECTS: 71 S. pneumoniae isolates from Parirenyatwa and Harare hospitals. MAIN OUTCOME MEASURES: Penicillin resistance, MIC of penicillin to S. pneumoniae, multi-drug resistance. RESULTS: 71 S. pneumoniae isolates were tested for their susceptibilities to penicillin G, erythromycin, tetracycline, ampicillin, ciprofloxacin and clindamycin. Five (7%) of the isolates were resistant to penicillin G and were also all resistant to erythromycin. Isolates resistant to other antibiotics were; tetracycline (4), ampicillin (3) and ciprofloxacin (2). The five isolates that were resistant to penicillin G showed resistance to two or more antibiotics. Four S. pneumoniae isolates were designated highly resistant to penicillin (MIC > or = 2 micrograms/ml) and one isolate was designated intermediate in resistance to penicillin (MIC between 0.1 and 1.0 microgram/ml). CONCLUSIONS: A low percentage of S. pneumoniae isolates were resistant to penicillin and were also resistant to erythromycin. The penicillin resistant strains showed multi-drug resistance.     

In vitro activities of the oxazolidinone compounds linezolid (PNU-100766) and eperzolid (PNU-100592) against middle ear isolates of Streptococcus pneumoniae.

Two hundred and sixteen isolates of Streptococcus pneumoniae recovered between 1994 and 1996 from the middle ears of children with acute otitis media were tested for their susceptibility to penicillin, erythromycin, clindamycin and the oxazolidinones, linezolid (PNU-100766) and eperezolid (PNU-100592). There were 116 isolates from the Children's Hospital of Pittsburgh and 100 isolates from a national collection. Eighty percent of the local strains were susceptible to penicillin (MIC < 0.1 mg/l); 20% of the local strains and all of the national strains had reduced susceptibility to penicillin. All strains of S. pneumoniae tested had an MIC < 2.0 mg/l for both oxazolidinones. A regional difference was noted in the frequency of resistance to erythromycin with local isolates being more susceptible than isolates from the national collection. This difference was most pronounced among the high-level penicillin-resistant strains of S. pneumoniae.     

Susceptibility of 1100 Streptococcus pneumoniae strains isolated in 1997 from seven Latin American and Caribbean countries. Laser Study Group

The antimicrobial susceptibility to beta-lactam and non-beta-lactam agents of 1100 isolates of Streptococcus pneumoniae recovered in 1997 from 16 centres in Argentina, Brazil, Chile, Mexico, Panama, Venezuela and West Indies was studied using E-test and disk diffusion methods. A total of 23.6% of isolates had raised penicillin MICs (16.7% intermediate and 6.9% resistant). The susceptibility of the other agents tested, from most active to least active, were, amoxycillin/clavulanate (99.5% susceptible); chloramphenicol (93.2%); cefotaxime (91.7%); erythromycin (87.1%); tetracycline (74.6%); trimethoprim/sulphamethoxazole (TMP-SMZ) (55.4%); and cefaclor (52.8%). The highest proportion of strains resistant to penicillin, chloramphenicol, erythromycin, tetracycline and TMP-SMZ was found in strains from Mexico while resistance to these agents was lowest in strains from the West Indies. Prevalence of penicillin resistance (including intermediate and resistant isolates) in each of the countries, from highest to lowest was, Mexico (40.8%); Chile (31.3%); Panama (23.0%); Venezuela (21.9%); Argentina (19.1%); Brazil (12.9%); and West Indies (7.1%). Based on current levels of antimicrobial resistance of S. pneumoniae in Latin American and Caribbean countries, continued surveillance efforts are necessary in order to guide clinical empiric treatment and provide for judicious use of antimicrobial agents.     

Antibiotic susceptibility of Streptococcus pneumoniae in New Zealand

AIMS: To determine the current antibiotic susceptibility patterns of Streptococcus pneumoniae from four centres in New Zealand. METHODS: Over a six-month period in 1997, 386 consecutive clinical isolates of S pneumoniae were collected by four laboratories (Auckland, Wellington, Hamilton and Christchurch) from general practice or inpatients. Susceptibility testing for seven antibiotics was performed by each centre using the Etest. RESULTS: Eighty-three-percent of isolates were penicillin susceptible, 12% showed intermediate resistance to penicillin and 5% were penicillin resistant. Overall, 93 and 91% of isolates were susceptible to amoxicillin/clavulanic acid and ceftriaxone, respectively. Erythromycin and tetracycline had similar rates of susceptibility (88 and 87%, respectively). Resistance to cotrimoxazole was common, with only 57% of isolates susceptible to this combination. No National Committee for Clinical Laboratory Standard (NCCLS) breakpoints were available for cefaclor to allow interpretation of the minimum inhibitory concentration data for this agent. Wellington had lower resistance rates than Auckland, Christchurch and Hamilton. Isolates from children had consistently higher resistance rates (two- to five-fold greater for beta-lactams and 1.2 to 1.3-fold for other agents) compared with isolates from adult patients. CONCLUSIONS: Resistance to multiple antibiotics among S pneumoniae is now evident in New Zealand, although rates varied between study centres. The overall rate of penicillin resistance is 5%, which is similar to that observed in many European and US cities but lower than the rates reported in badly affected areas (> 30%). These data suggest that amoxicillin (+/- clavulanic acid), erythromycin or tetracycline are appropriate agents for empirical use in less serious community acquired infections when S pneumoniae is suspected. Ceftriaxone, with or without vancomycin, should be considered in the empirical treatment of invasive, disease until sensitivities are known.     

Antibiotic resistance in outpatient urinary isolates: final results from the North American Urinary Tract Infection Collaborative Alliance (NAUTICA)

The goal of the North American Urinary Tract Infection Collaborative Alliance (NAUTICA) study was to determine antibiotic susceptibility to commonly used agents for urinary tract infections against outpatient urinary isolates obtained in various geographic regions in the USA and Canada. Forty-one medical centres (30 from the USA and 11 from Canada) participated, with each centre submitting up to 50 consecutive outpatient midstream urine isolates. Isolates were identified to species level by the standard protocol of each laboratory. Susceptibility testing was determined using the National Committee for Clinical Laboratory Standards (NCCLS) microdilution method. Resistance breakpoints used were those published by the NCCLS, including: ampicillin (resistant > or = 32 microg/mL), sulphamethoxazole/trimethoprim (SMX/TMP) (resistant > or = 4 microg/mL), nitrofurantoin (resistant > or = 128 microg/mL), ciprofloxacin (resistant > or = 4 microg/mL) and levofloxacin (resistant > or = 8 microg/mL). Of the 1990 isolates collected, 75.1% (1494) were collected from the USA and 24.9% (496) were collected from Canada. The mean age of the patients was 48.3 years (range 1 month to 99 years), and 79.5% and 20.5% of isolates were obtained from women and men, respectively. The most common organisms were Escherichia coli (57.5%), Klebsiella pneumoniae (12.4%), Enterococcus spp. (6.6%), Proteus mirabilis (5.4%), Pseudomonas aeruginosa (2.9%), Citrobacter spp. (2.7%), Staphylococcus aureus (2.2%), Enterobacter cloacae (1.9%), coagulase-negative staphylococci (1.3%), Staphylococcus saprophyticus (1.2%), Klebsiella spp. (1.2%), Enterobacter aerogenes (1.1%) and Streptococcus agalactiae (1.0%). Among all 1990 isolates, 45.9% were resistant to ampicillin, 20.4% to SMX/TMP, 14.3% to nitrofurantoin, 9.7% to ciprofloxacin and 8.1% to levofloxacin. Fluoroquinolone resistance was highest in patients > or = 65 years of age. For the 1142 E. coli isolates, resistance rates were: ampicillin 37.7%, SMX/TMP 21.3%, ciprofloxacin 5.5%, levofloxacin 5.1% and nitrofurantoin 1.1%. For all 1990 isolates and for the 1142 E. coli only, resistance rates were significantly higher in US compared with Canadian medical centres. This study reports higher rates of antibiotic resistance in US versus Canadian outpatient urinary isolates and demonstrates the continuing evolution of resistance to antimicrobial agents.