Distribution of Class 1–3 Integrons in Carbapenem-Resistant Pseudomonas aeruginosa Isolated from Inpatients in Shiraz,South of Iran

BackgroundHealth-care-associated infection (HAI) is effect on patients for the time of staying in the hospital. Opportunistic pathogens including Pseudomonas aeruginosa are the most dangerous biological agents in nosocomial infections. This study aimed to assess the prevalence of 3 classes of integrons carrying to carbapenem resistance in P. aeruginosa strains collected from Nemazee hospital.MethodsThis cross-sectional study was conducted on clinical P. aeruginosa isolates were collected from Nemazee hospital. The identification of the isolates was performed by routine biochemical tests. Antimicrobial sensitivity testing was determined using the disk diffusion method against imipenem and meropenem. The int1, int2 and int3 genes were detected using the polymerase chain reaction (PCR).ResultsSeventy-five clinical isolates of P. aeruginosa were recovered from various clinical infections. A carbapenem-resistant phenotype was detected in 42.7% (imipenem) and 29.3% (meropenem) of isolates. As the PCR results, 48 (64%) and 15 (20%) isolates were identified as being positive for class 1 and class 2 integrons, respectively. Class 3 integrons were not found among the studied isolates.ConclusionsOur data demonstrate the importance of class 1 and 2 integrons in carbapenem resistant P. aeruginosa strains. Therefore, integrons play an important role in acquisition and dissemination of carbapenem resistance genes among these pathogens, so, management of infection control policies and the appropriate use of antibiotics is essential for control the spreading of antibiotics resistance genes.     

肺部感染铜绿假单胞菌耐药性与抗菌药物治疗效果研究

目的 分析广州地区肺部感染患者分离的铜绿假单胞菌（PA)耐药性及整合子携带情况，探讨其抗菌药物治疗效果及影响因素。方法 回顾性调查2008年9月-2010年12月广州市3所三级甲等医院呼吸内科确诊为PA肺部感染患者的病历资料。收集上述患者标本分离的PA菌株，检测其对常用抗菌药物的敏感性；采用聚合酶链反应（PCR）法扩增菌株整合子片段，分析整合子的类型；分析影响PA肺部感染患者预后的可能危险因素。结果共收集PA 114株,检出多重耐药菌47株（41.23%）；71株（62.28%）PA检出Ⅰ类整合子。患者预后：21例（18.42%）治愈，63例（55.26%）好转，30例（26.32%）死亡。除庆大霉素、阿米卡星、妥布霉素、哌拉西林及哌拉西林/他唑巴坦外，Ⅰ类整合子阳性菌株对常用抗菌药物的耐药率明显高于Ⅰ类整合子阴性菌株（均P＜0.05）。影响PA肺部感染患者预后的危险因素包括整合子阳性、多重耐药菌株、不适当的经验性治疗、联合使用3类或以上抗菌药物、混合感染、碳青霉烯类抗生素的使用，而联合使用2类抗菌药物是患者预后的保护因素。结论肺部感染患者分离的PA多重耐药率及Ⅰ类整合子携带率较高，整合子与耐药性关系密切，应加强监测。尽量避免使用碳青霉烯类抗生素进行经验性治疗；可联合使用2类抗菌药物进行抗感染治疗。     

Emergence of highly antibiotic-resistant Pseudomonas aeruginosa in relation to duration of empirical antipseudomonal antibiotic treatment

OBJECTIVE: This study examines antibiotic resistance in Pseudomonas aeruginosa in hospitalized patients in relation to prior empirical antibiotic therapy. DESIGN: Two retrospective case analyses comparing patients who manifested P aeruginosa with differing patterns of antibiotic resistance. SETTING AND PARTICIPANTS: Patients acquiring P aeruginosa in a community hospital. MEASURES: Patients were compared on duration of hospitalization and days and doses of antibiotics prior to recovery of P aeruginosa. Patients were grouped, based on susceptibility patterns of their P aeruginosa isolates classified as follows: (1) fully susceptible (susceptible to all classes of antipseudomonal antibiotics [SPA]), (2) multidrug-resistant (resistant to two classes of antipseudomonal antibiotics [MDRPA]), or (3) highly drug-resistant (resistant to > or = 6 classes of antipseudomonal antibiotics [HRPA]). To control for duration of hospitalization, antibiotic treatments of HRPA and SPA patients were compared during the first 21 days of care. RESULTS: Prior to recovery of HRPA, six HRPA patients received greater amounts of antibiotics, both antipseudomonal and non-antipseudomonal, than did six SPA patients prior to recovery of SPA. For 14 patients with hospital-acquired SPA who later manifested MDRPA, duration and dosage of antipseudomonal antibiotics, but not all antibiotics, were significantly higher for the SPA-to-MDRPA interval than for the preceding admission-to-SPA interval. The median duration of antipseudomonal antibiotic treatment prior to the recovery of P aeruginosa was 0 days for SPA, 11 days for MDRPA, and 24 days for HRPA. CONCLUSION: Duration of empirical antipseudomonal antibiotic treatment influences selection of resistant strains of P aeruginosa; the longer the duration, the broader the pattern of resistance.     

Endemic carbapenem-resistant Pseudomonas aeruginosa with acquired metallo-beta-lactamase determinants in European hospital

Acquired metallo-beta-lactamases (MBLs) can confer broad-spectrum beta-lactam resistance (including carbapenems) not reversible by conventional beta-lactamase inhibitors and are emerging resistance determinants of remarkable clinical importance. In 2001, multidrug-resistant Pseudomonas aeruginosa carrying bla(VIM) MBL genes were found to be widespread (approximately 20% of all P. aeruginosa isolates and 70% of the carbapenem-resistant isolates) at Trieste University Hospital. Clonal diversity and heterogeneity of resistance determinants (either bla(VIM-1)-like or bla(VIM-2)-like) were detected among MBL producers. This evidence is the first that acquired MBLs can rapidly emerge and establish a condition of endemicity in certain epidemiologic settings.     

老年患者铜绿假单胞菌医院感染的危险因素与耐药性分析

目的探讨254例老年患者铜绿假单胞菌（PAE）医院感染的危险因素及耐药性,为临床监测与控制PAE感染提供依据。方法统计老年患者PAE医院感染的临床资料,采用K-B法对PAE进行体外耐药监测。结果老年患者PAE医院感染的危险因素为原发基础疾病、免疫功能低下、住院日长、侵入性治疗、抗菌药物使用时间长等;PAE对复方新诺明和头孢噻肟耐药率分别为74.8%、60.2%,对亚胺培南耐药率为3.9%。结论建议采取综合治理措施,控制耐药菌的传播,提高对老年患者PAE感染的防治水平。     

耐碳青霉烯乙酸钙-鲍蔓不动杆菌肺炎的临床分析

目的探讨与重症监护病房(ICU)患者耐碳青霉烯乙酸钙_鲍蔓不动杆菌(CRA.b)肺炎相关的临床相关因素,为临床预防CRA.b的感染提供依据。方法前瞻性分析本院ICU收治的78例乙酸钙_鲍蔓不动杆菌肺炎患者的临床资料,分析耐碳青霉烯乙酸钙_鲍蔓不动杆菌危险因素。结果通过CRA.b阳性患者和对碳青霉烯敏感的乙酸钙_鲍蔓不动杆菌(CSA.b)患者危险因素的比较,发现CRA.b阳性患者细菌均为多重耐药株,仅对头孢哌酮/舒巴坦耐药率相对较低,为16.2%,敏感率为41.0%。CRA.b阳性患者多频繁或超长使用碳青霉烯类抗生素,住院环境中有CRA.b。结论本院碳青霉烯类耐药鲍曼不动杆菌流行主要为医院感染所致,且多重耐药。因此,合理使用碳青霉烯类抗生素,严格控制感染尤为重要。     

Antibiotic resistance in long-term acute care hospitals: the perfect storm.

OBJECTIVE: To examine bacterial antibiotic resistance and antibiotic use patterns in long-term acute care hospitals (LTACHs) and to evaluate effects of antibiotic use and other hospital-level variables on the prevalence of antibiotic resistance. DESIGN: Multihospital ecologic study. METHODS: Antibiograms, antibiotic purchasing data, and demographic variables from 2002 and 2003 were obtained from 45 LTACHs. Multivariable regression models were constructed, controlling for other hospital-level variables, to evaluate the effects of antibiotic use on resistance for selected pathogens. Results of active surveillance in 2003 at one LTACH were available. RESULTS: Among LTACHs, median prevalences of resistance for several antimicrobial-organism pairs were greater than the 90th percentile value for National Nosocomial Infections Surveillance system (NNIS) medical intensive care units (ICUs). The median prevalence of methicillin resistance among Staphylococcus aureus isolates was 84%. More than 60% of patients in one LTACH were infected or colonized with methicillin-resistant S. aureus and/or vancomycin-resistant Enterococcus at the time of admission. Antibiotic consumption in LTACHs was comparable to consumption in NNIS medical ICUs. In multivariable logistic regression modeling, the only significant association between antibiotic use and the prevalence of antibiotic resistance was for carbapenems and imipenem resistance among Pseudomonas aeruginosa isolates (odds ratio, 11.88 [95% confidence interval, 1.42-99.13]; P=.02). CONCLUSIONS: The prevalence of antibiotic resistance among bacteria recovered from patients in LTACHs is extremely high. Although antibiotic use in LTACHs likely contributes to resistance prevalence for some antimicrobial-organism pairs, for the majority of such pairs, other variables, such as prior colonization with and horizontal transmission of antimicrobial-resistant pathogens, may be more important determinants. Further research on antibiotic resistance in LTACHs is needed, particularly with respect to determining optimal infection control practices in this environment.     

Impact of antibiotic changes in empirical therapy on antimicrobial resistance in intensive care unit-acquired infections

We conducted a one-year prospective study on intensive care unit (ICU)-acquired infections and antimicrobial resistance patterns in an 18-bed medical-surgical ICU of a tertiary-care university hospital. We divided the study into two six-month periods in order to evaluate the impact of antibiotic changes in empirical therapy on antimicrobial resistance profiles of the principal isolated micro-organisms. In the first period no changes were made to the previously applied empirical antibiotic protocol; at the end of this period we found high rates of methicillin resistance (MR) among staphylococci, 93% for Staphylococcus aureus (69 isolates) and 79% for coagulase-negative staphylococci (CNS) (48 isolates), and of multiple drug resistance for Pseudomonas aeruginosa (57 isolates), in particular 67% resistance to piperacillin/tazobactam (PIP/TZ). We therefore decided to substitute PIP/TZ with imipenem in nosocomial pneumonia and with cefepime plus metronidazole in peritonitis. We also considered the previous use of amoxicillin/clavulanate (AM/CL) at admission in critically ill patients inadequate; we therefore advised that no antibiotics should be given unless fever developed and eventually to replace AM/CL with trimethoprim/sulfamethoxazole (TMP/SMX). At the end of this intervention period, we observed a significant decrease of S. aureus MR (93 vs. 73%, P = 0.003) and of P. aeruginosa resistance to PIP/TZ (67 vs. 29%, P < 0.001). A reduction in MR was also seen in CNS (79 vs. 64%, P = 0.09). Other resistance patterns also improved among staphylococci; in contrast P. aeruginosa resistance to imipenem increased in the second period (24 vs. 41%, P = 0.06). A non-premeditated change of antibiotics in empirical therapy, on the basis of detected resistance patterns, provided promising results in reducing some antimicrobial resistance rates. We believe, however, that antibiotic changes must be tailored to local microbiological situation monitoring, and that a repeated rotation is crucial to limit the emergence of new resistance profiles. Furthermore the adoption of this policy should be accompanied by other infection control practices aimed at reducing antimicrobial resistance and nosocomial infection rates.     

Imipenem resistance among pseudomonas aeruginosa isolates: risk factors for infection and impact of resistance on clinical and economic outcomes.

OBJECTIVES: To identify risk factors for infection with imipenem-resistant Pseudomonas aeruginosa and determine the impact of imipenem resistance on clinical and economic outcomes among patients infected with P. aeruginosa. DESIGNS: An ecologic study, a case-control study, and a retrospective cohort study. SETTING: A 625-bed tertiary care medical center. PATIENTS: All patients who had an inpatient clinical culture positive for P. aeruginosa between January 1, 1999, and December 31, 2000. RESULTS: From 1991 through 2000, the annual prevalence of imipenem resistance among P. aeruginosa isolates increased significantly (P<.001 by the chi (2) test for trend). Among 879 patients infected with P. aeruginosa during 1999-2000, a total of 142 had imipenem-resistant P. aeruginosa infection (the case group), whereas 737 had imipenem-susceptible P. aeruginosa infection (the control group). The only independent risk factor for imipenem-resistant P. aeruginosa infection was prior fluoroquinolone use (adjusted odds ratio, 2.52 [95% confidence interval {CI}, 1.61-3.92]; P<.001). Compared with patients infected with imipenem-susceptible P. aeruginosa, patients infected with imipenem-resistant P. aeruginosa had longer subsequent hospitalization durations (15.5 days vs 9 days; P=.02) and greater hospital costs (81,330 dollars vs 48,381dollars ; P<.001). The mortality rate among patients infected with imipenem-resistant P. aeruginosa was 31.1%, compared with 16.7% for patients infected with imipenem-susceptible P. aeruginosa (relative risk, 1.86 [95% CI, 1.38-2.51]; P<.001). In multivariable analyses, there remained an independent association between infection with imipenem-resistant P. aeruginosa and mortality. CONCLUSIONS: The prevalence of imipenem resistance among P. aeruginosa strains has increased markedly in recent years and has had a significant impact on both clinical and economic outcomes. Our results suggest that curtailing use of other antibiotics (particularly fluoroquinolones) may be important in attempts to curb further emergence of imipenem resistance.     

First report of Klebsiella pneumonia carbapenemase-producing Pseudomonas aeruginosa isolated from burn patients in Iran: phenotypic and genotypic methods

Wound infection associated with carbapenem-resistant Pseudomonas aeruginosa in burn patients is a growing problem. One of the main mechanisms of resistance to carbapenem antibiotics is the ability of P. aeruginosa to produce carbapenemase enzymes. Klebsiella pneumonia carbapemenase (KPC) is an important type of carbapenemase which can hydrolyze carbapenem antibiotics. The Modified Hodge Test (MHT) and boronic acid as a KPC inhibitor are two phenotypic methods used for detection of carbapenemase. The sensitivity and specificity of these two phenotypic tests for the identification of KPC can be measured by PCR.In this study, 241 P. aeruginosa strains were isolated from wounds of hospitalized burn patients. Carbapenem-resistant P. aeruginosa isolates were determined by the disk diffusion method. KPC-producing carbapenem-resistant strains were examined using the Modified Hodge Test, followed by boronic acid. Further, strains with positive responses to MHT and boronic acid tests were analyzed with the PCR molecular method. One hundred eighty-six of 241 isolates were resistant to carbapenems and 75 were positive in the MHT. Three exhibited an at least 5-mm diameter difference when meropenem was combined with boronic acid vs meropenem alone in the boronic acid test. Two strains had a specific band with primer No.1 after gel electrophoresis. This study showed that MHT, despite excellent sensitivity, has variable specificity independent of bacterial species. Further, the use of KPC inhibitors such as boronic acid did not yield favorable sensitivity and specificity among the specimens from Iranian patients. Thus, it seems that sequencing after PCR should be considered the gold standard for the detection of KPC-producing P. aeruginosa.     

耐碳青霉烯类大肠埃希菌分子流行病学机制研究

目的 研究重症监护病房(ICU)耐碳青霉烯类大肠埃希菌分子流行病学特征和耐药机制.方法 采用琼脂稀释法检测分离株的抗菌药物敏感性,采用PCR、DNA测序分析介导碳青霉烯类耐药的基因型,采用脉冲场琼脂糖凝胶电泳(PFGE)进行分子分型,研究耐碳青霉烯类大肠埃希菌的耐药机制和遗传关系.结果 临床分离的14株泛耐药菌株,均表现多药耐药性,碳青霉烯类耐药基因扩增显示,均带KPC-2型碳青霉烯酶基因,分子流行病学分析,14株菌分别属于10个流行克隆型.结论 医院出现耐碳青霉烯类大肠埃希菌,碳青霉烯酶KPC-2,是泛耐药大肠埃希菌介导,对碳青霉烯类耐药的主要原因.     

Molecular typing of imipenem-resistant Acinetobacter baumannii-calcoaceticus complex in a Singapore hospital where carbapenem resistance is endemic.

OBJECTIVE: To investigate the molecular epidemiology of carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex isolates in a tertiary care hospital where the prevalence of carbapenem resistance among these organisms is high. DESIGN: The study was a prospective, observational study performed during an 8-month period (May 1 through December 31, 2004). A. baumannii isolates recovered from all clinical samples during the study period were included in the study. Antibiotic susceptibility testing was performed using the disk diffusion method, and all carbapenem-resistant strains were typed by a polymerase chain reaction-based typing method.Setting. An 800-bed hospital in Singapore. RESULTS: More than half of recovered isolates were clonally unrelated, with the remaining isolates grouped into 4 genotypes. CONCLUSIONS: The results of the study suggest that the high prevalence of carbapenem resistance among Acinetobacter organisms in this institution is not caused by the spread of a predominant clone and that other factors may need to be investigated.     

老年人尿路感染常见病原菌耐药性分析

[目的]探讨老年尿路感染患者的常见病原菌的耐药性。[方法]回顾性分析440例住院尿路感染患者的中段尿标本实验室检验结果。[结果]①住院老年患者清洁中段尿的病原菌检出率为82.9%。②检出的365株菌株中,大肠埃希菌占40.5%,奇异变形杆菌占17.8%,肺炎克雷伯菌占12.3%,铜绿假单胞菌占8.5%,肠球菌属占6.0%。产超广谱β-内酰胺酶(ESBLs)大肠埃希菌和肺炎克雷伯菌的检出率为51.4%和42.2%。③G-杆菌对氨苄西林、哌拉西林、环丙沙星耐药率高,对头孢哌酮舒巴坦耐药率低,对碳青酶类无耐药;G+球菌对克林霉素、克拉霉素、氧氟沙星耐药率高,对万古霉素无耐药。产ESBLs大肠埃希菌、肺炎克雷伯菌对第二、三代头孢菌素、氨苄西林、环丙沙星耐药率高,对头孢哌酮舒巴坦、丁胺卡那敏感,对碳青酶类无耐药。④添加酶抑制剂的抗生素对大肠埃希菌、肺炎克雷伯菌的药物敏感性极显著高于未添加酶抑制剂者。[结论]老年人尿路感染病原菌耐药性高,头孢哌酮舒巴坦是治疗老年人尿路感染较为理想的药物。     

某医院患者呼吸道感染的菌种分布及其耐药情况

目的了解某医院呼吸科患者呼吸道感染的菌群分布特点及耐药情况,指导临床合理用药。方法采用VITEK-2鉴定细菌,按照NCCLS标准采用纸片扩散(Kirby-Bauer)法对临床分离菌株进行药敏试验。结果共分离革兰阴性菌527株,占全部分离菌的58.8%。以铜绿假单胞菌、鲍曼不动杆菌、肺炎克雷伯菌、嗜麦芽窄食单胞菌和大肠埃希菌多见。药敏试验结果表明,肠道杆菌主要对碳青霉烯类敏感,肺炎克雷伯菌、大肠埃希菌等对头孢菌素类、氨基糖苷类、喹诺酮类抗菌药物耐药率高,铜绿假单胞菌、肠杆菌等呈现多重耐药。结论呼吸道感染病原体中以革兰阴性菌为主,革兰阴性菌的耐药问题严重且出现多重耐药,定期进行病原菌耐药性监测,对指导临床合理应用抗菌药物具有重要意义。     

医院获得性肺炎患者分离耐碳青霉烯类铜绿假单胞菌OprD的表达

目的 研究耐碳青霉烯类抗菌药物铜绿假单胞菌(PAE) OprD的表达水平,探讨济南地区PAE耐碳青霉烯类抗菌药物的机制.方法 收集从医院获得性肺炎患者痰液中分离的PAE,提取13株耐碳青霉烯类抗菌药物菌株的RNA,应用荧光实时定量PCR分析PAE外膜蛋白oprD的基因表达水平;采用超声破碎法制备外膜蛋白,超速离心收集外膜蛋白,十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分离外膜蛋白,观察OprD的表达.结果 荧光实时定量RT-PCR检测PAEoprD基因表达的结果表明,实验室标准株Ct值oprD/rpsL为1.42;13株碳青霉烯类耐药株Ct值oprD/rpsL平均值为1.17,与实验室标准株相比,差异有统计学意义(t=3.0716,P＜0.01),2株碳青霉烯类敏感株Ct值的oprD/rpsL平均值为1.58,与实验室标准株相比,差异无统计学意义;外膜蛋白电泳图谱表明,碳青霉烯类耐药株在45 kDa处表达明显下降,此处外膜蛋白为OprD.结论 济南地区PAE耐碳青霉烯类抗菌药物与OprD表达水平下降有关.     

耐碳青霉烯药物肺炎克雷伯菌研究进展

随着临床碳青霉烯类抗菌药物的大量应用,耐碳青霉烯药物肠杆菌科广泛流行,其中耐碳青霉烯药物肺炎克雷伯菌临床检出率逐渐增加,给临床诊疗和感染控制带来很大挑战.现就耐碳青霉烯肺炎克雷伯菌的感染现状、耐药机制、检测及治疗进展作一综述.     

引起医院下呼吸道感染病原菌的分布及耐药性分析

目的了解住院患者下呼吸道感染病原菌的分布及耐药特点,为临床合理用药提供依据。方法对2003至2006年住院患者下呼吸道感染痰标本所分离的病原菌,进行菌种和耐药性回顾性统计分析。结果临床所分离的3113株病原菌中,前几位依次为铜绿假单胞菌、鲍氏不动杆菌、肺炎克雷伯菌、大肠埃希菌和金黄色葡萄球菌;铜绿假单胞菌和鲍氏不动杆菌常呈多药耐药且对亚胺培南耐药率上升明显;除亚胺培南外,肠杆菌科细菌对其他抗菌药物的耐药率总体上呈逐年上升趋势;产超广谱β-内酰胺酶（ESBLs）克雷伯菌属检出率为16.7%～32.5%,产ESBLs大肠埃希菌检出率〉64.4%,产ESBLs菌株的耐药率明显高于非产ESBLs菌株;金黄色葡萄球菌中耐甲氧西林金黄色葡萄球菌（MRSA）的分离率较高。结论下呼吸道感染病原菌以革兰阴性杆菌为主,主要的病原菌对临床常用抗菌药物耐药严重,临床应合理应用抗菌药物,以延缓细菌耐药性的产生。     

Risk factors for and impact of infection or colonization with aztreonam-resistant Pseudomonas aeruginosa.

OBJECTIVE: To identify risk factors for infection or colonization with aztreonam-resistant Pseudomonas aeruginosa and examine the impact of this organism on mortality. DESIGN: A case-control study was performed to identify risk factors for infection or colonization with aztreonam-resistant P. aeruginosa. A cohort study was subsequently performed to examine the impact of aztreonam resistance on outcomes. SETTING: A tertiary referral center in southeastern Pennsylvania.Participants. Inpatients with a clinical culture positive for P. aeruginosa between January 1, 1999, and December 31, 2000. RESULTS: Of 720 P. aeruginosa. isolates, 183 (25.4%) were aztreonam-resistant and 537 (74.6%) were aztreonam susceptible. In a multivariable model, prior fluoroquinolone use (adjusted odds ratio [aOR], 1.81 [95% confidence interval {CI}, 1.17-2.80]), prior use of an antianaerobic agent (aOR, 1.56 [95% CI, 1.06-2.29]), and renal insufficiency (aOR, 1.59 [95% CI, 1.10-2.29]) were associated with infection or colonization with aztreonam-resistant P. aeruginosa, while older age (aOR, 0.98 [95% CI, 0.97-0.99] per year of age) was negatively associated with infection or colonization with this organism. In-hospital mortality was higher among subjects infected or colonized with aztreonam-resistant P. aeruginosa, compared with those who were infected or colonized with aztreonam-susceptible P. aeruginosa (25.7% vs 16.8%; P=.009), but in multivariable analysis, no significant association was found between infection or colonization with aztreonam-resistant P. aeruginosa and mortality. CONCLUSIONS: Curbing the use of fluoroquinolones and antimicrobials with antianaerobic activity may be an effective strategy to limit the emergence of aztreonam-resistant P. aeruginosa.     

Relationship between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from 47 French hospitals.

OBJECTIVE: To investigate relationships between rates of antimicrobial consumption and the incidence of antimicrobial resistance in Staphylococcus aureus and Pseudomonas aeruginosa isolates from hospitals. METHODS: We conducted an observational study that used retrospective data from 2002 and linear regression to model relationships. Hospitals were asked to collect data on consecutive S. aureus and P. aeruginosa isolates, consumption rates for antibiotics (ie, anti-infectives for systemic use as defined by Anatomical Therapeutic Chemical class J01), and hospital characteristics, including infection control policies. Rates of methicillin resistance in S. aureus and rates of ceftazidime and ciprofloxacin resistance in P. aeruginosa were expressed as the percentage of isolates that were nonsusceptible (ie, either resistant or intermediately susceptible) and as the incidence of nonsuceptible isolates (ie, the number of nonsuceptible isolates recovered per 1,000 patient-days). The rate of antimicrobial consumption was expressed as the number of defined daily doses per 1,000 patient-days. SETTING: Data were obtained from 47 French hospitals, and a total of 12,188 S. aureus isolates and 6,370 P. aeruginosa isolates were tested. RESULTS: In the multivariate analysis, fewer antimicrobials showed a significant association between the consumption rate and the percentage of isolates that were resistant than an association between the consumption rate and the incidence of resistance. The overall rate of antibiotic consumption, not including the antibiotics used to treat methicillin-resistant S. aureus infection, explained 13% of the variance between hospitals in the incidence of methicillin resistance among S. aureus isolates. The incidence of methicillin resistance in S. aureus isolates increased with the use of ciprofloxacin and levofloxacin and with the percentage of the hospital's beds located in intensive care units (adjusted multivariate coefficient of determination [aR(2)], 0.30). For P. aeruginosa, the incidence of ceftazidime resistance was greater in hospitals with higher consumption rates for ceftazidime, levofloxacin, and gentamicin (aR(2), 0.37). The incidence of ciprofloxacin resistance increased with the use of fluoroquinolones and with the percentage of a hospital's beds located in intensive care ( aR(2), 0.28). CONCLUSIONS: A statistically significant relationship existed between the rate of fluoroquinolone use and the rate of antimicrobial resistance among S. aureus and P. aeruginosa isolates. The incidence of resistant isolates showed a stronger association with the rate of antimicrobial use than did the percentage of isolates with resistance.