Antimicrobial susceptibility of clinical isolates of Brucella

A number of antimicrobial agents have been used in the treatment of human brucellosis with varying effectiveness. The purpose of this study was to test the in vitro susceptibility of isolates of four Brucella species to a variety of antimicrobial agents, and to study in vitro synergy of combinations of agents. Minimal inhibitory concentrations (MICs) were determined using conventional broth microdilution methods and commercially available systems. Conventional checkerboard synergy microdilutions were prepared for gentamicin or streptomycin plus tetracycline, and rifampicin plus tetracycline. Synergy or antagonism was determined by the fractional inhibitory concentration index. Penicillin G and ampicillin showed in vitro activity against Brucella (MIC90 4 micrograms/ml), whereas the antipseudomonal penicillins were less active (carbenicillin MIC90 12 micrograms/ml, piperacillin MIC90 32 micrograms/ml). Among the third generation cephalosporins tested, cefotaxime (MIC90 2 micrograms/ml) demonstrated greatest activity. As a class, aminoglycosides were equivalent (MIC90 1-4 micrograms/ml). All strains were sensitive to tetracycline (MIC90 0.25 microgram/ml), trimethoprim-sulfamethoxazole (MIC90 1/19 micrograms/ml), and rifampin (MIC90 1 microgram/ml). Erythromycin (MIC90 greater than 8 micrograms/ml) and vancomycin (MIC90 greater than 16 micrograms/ml) demonstrated no activity. In vitro synergy (fractional inhibitory concentration index less than 0.5) was demonstrated with tetracycline plus rafampin in six of eight isolates tested.     

Antimicrobial susceptibility of clinical isolates of Acinetobacter baumannii

The in-vitro activity of 18 antimicrobial agents alone or in combination against 248 clinical isolates of Acinetobacter baumannii from Taiwan were tested by agar dilution. The MIC₉₀s of ampicillin, amoxicillin, piperacillin, cefuroxime, cefotaxime, ceftriaxone, gentamicin, and amikacin were at least 128 μg/ml. Ceftazidime, cefepime, sulbactam, clavulanic acid, and tazobactam presented moderate activity with MIC₉₀s of 32, 16, 16, 32, and 32 μg/ml, respectively. The increased activity of ampicillin/sulbactam, amoxicillin/clavulanic acid, and piperacillin/tazobactam was due to the intrinsic effect of sulbactam, clavulanic acid, and tazobactam, respectively. Imipenem, meropenem, and ciprofloxacin were the most active antimicrobial agents with MIC₉₀s of 1, 1, and 0.5 μg/ml, respectively. Nineteen isolates (7.7%) were resistant to all aminoglycosides and β-lactam antibiotics, except carbapenems and ciprofloxacin. We are concerned about the multidrug resistance of A. baumannii in this study.     

大肠埃希菌临床分离株耐药性分析

目的：监测近5年来大肠埃希菌临床分离株的耐药性变迁，指导临床合理使用抗生素。方法：常规方法进行菌株分离，采用VITEK-32全自动微生物分析仪进行菌株鉴定及药敏试验，超广谱β内酰胺酶采用双纸片确认试验和仪器检测相结合的方法，对近5年来我院大肠埃希菌的耐药谱进行回顾性调查分析。结果：近5年从各种临床标本中共分离到大肠埃希菌488株，大肠埃希菌对青霉素类及第一代头孢菌素耐药率最高。2002年，对氨苄西林、替卡西林和头孢噻吩耐药率均高达98％，对亚胺培南耐药率最低，5年耐药率均为零。对培氟沙星和替卡西林耐药率上升最快，分别上升了28和26个百分点，对呋喃妥因耐药率有所下降，对庆大霉素和妥布霉素耐药率趋于稳定。产ESBLs菌株有明显上升趋势，从1998年的17％上升到2002年的36％。结论：大肠埃希菌在临床标本中的检出率、耐药性及多重耐药性均有逐年上升的趋势。     

Antimicrobial susceptibility of clinical isolates of Serratia marcescens.

The in vitro susceptibilities of 242 isolates of Serratia marcescens to 17 antibacterial drugs have been determined. Oxolinic acid, nalidixic acid, cefoxitin, and amikacin were the most active drugs. Ampicillin, kanamycin, and cephalothin were among the least active. A 4-year study showed that resistance of S. marcescens to dibekacin, tobramycin, sisomycin, and gentamicin has increased at least one order of magnitude in that period, whereas resistance to amikacin showed but a twofold increase.     

Antimicrobial susceptibility of clinical isolates of gram-negative bacilli.

No one can doubt the increased incidence of gram-negative bacillary infections and the importance of an awareness of this increase. Today's hospital, where one finds aggressive surgery, patients with multiple indwelling polyethylene lines and Foley catheters, and widespread use of prophylactic antibiotics, serves as a haven for resistant gram-negative bacilli. Twenty-five strains of Escherichia coli, Klebsiella sp, Enterobacter sp, Pseudomonas sp, indole-negative Proteus sp, indole-positive Proteus sp, and Serratia sp from hospitalized patients were tested for susceptibility to eight commonly used antibiotics using an inocula replicating method. Gentamicin proved to be the most effective antibiotic against the majority; most strains were inhibited by 3.12mug/ml or less. Other antibiotics, although not so active against all species, were effective against selected species.     

磷霉素氨丁三醇对尿标本中分离菌的体外抗菌活性

目的 :分析磷霉素氨丁三醇对泌尿道感染分离菌的体外抗菌活性 ,并与其他 9种抗菌药物进行比较。方法 :用K B法对 110株引起泌尿道感染的细菌做体外药物敏感试验。结果 :磷霉素氨丁三醇对 110株细菌体外总敏感率为 84 .5 % ,其中93株革兰阴性杆菌和 17株革兰阳性球菌的敏感率分别为 82 .8%和 93.8% ,对占多数的大肠埃希菌的敏感率为 94 .1%。大肠埃希菌对磷霉素氨丁三醇与头孢噻肟的敏感性的差异无显著性 (P >0 .0 5 ) ,而其余 8种抗菌药物与磷霉素氨丁三醇相比差异均有显著性 (P <0 .0 5 )。     

留置导尿致泌尿系感染的常见菌群及其药敏分析

目的：了解留置导尿致泌尿系感染的常见菌群及其对抗生素的耐药性，以采取易行实用的预防对策，减少医院感染的发生率。方法：对从2000年5月—2003年5月因留置导尿致泌尿系感染而分离出的193株病原菌进行回顾性调查分析。结果：分离出193株病原菌中，革兰阴性杆菌118株(61．1％)，革兰阳性球菌49株(25．3％)，真菌26株(13．5％)。主要病原菌依次为大肠埃希菌(35．8％)、白念珠菌(10．9％)、粪肠球菌(9．3％)、肺炎克雷伯菌(8．3％)、铜绿假单胞菌(5．7％)和表皮葡萄球菌(5．7％)。药敏试验结果提示除真菌外的大多数病原菌出现多重耐药性。革兰阴性杆菌对亚胺培南、头孢派酮一舒巴坦、头孢西丁和阿米卡星较为敏感。革兰阳性球菌对替考拉宁和万古霉素高度敏感。16株大肠埃希菌产超广谱β内酰胺酶(ESBLs)，产酶率23．2％。结论：留置导尿致泌尿系感染的病原菌以大肠埃希菌为最常见，其次为白念珠菌、粪肠球菌和肺炎克雷伯菌。合理使用各种侵袭性诊疗技术及抗生素对有效控制泌尿系感染和避免耐药菌株的产生尤为重要。     

Antimicrobial susceptibility of clinical isolates of Haemophilus influenzae to ampicillin-sulbactam

A total of 1092 clinical isolates of Haemophilus influenzae (306 type b; 786 non-type-b), from five medical centers were obtained during 1987 and 1988. Disk diffusion antimicrobial susceptibilities were obtained for all isolates, and broth microdilution susceptibilities were obtained for 502 isolates. Beta-lactamase was produced by 34.3% of type-b and 22.1% of non-type-b isolates, with some geographic variations. Using disk diffusion antimicrobial susceptibility testing, all isolates were susceptible to ampicillin-sulbactam, ceftriaxone, cefuroxime, and rifampin; two isolates were resistant to chloramphenicol. Whether tested using a fixed ratio of ampicillin to sulbactam of 2:1 or a fixed concentration of sulbactam, the ampicillin-sulbactam combination demonstrated good activity against clinical isolates of H. influenzae. Only 8 of the 1092 isolates did not produce beta-lactamase but demonstrated MICs of greater than or equal to 2 micrograms/ml for ampicillin.     

Antimicrobial susceptibility of Branhamella catarrhalis isolates from bronchopulmonary infections

Fifty-four clinical isolates of Branhamella catarrhalis from patients with bronchopulmonary infections were studied. The MICs for 50 and 90% of the isolates and the geometric mean MICs were determined for 11 antimicrobial agents. All the strains were resistant to trimethoprim but were susceptible to clavulanate-potentiated amoxicillin (Augmentin; Beecham Research Laboratories, London), chloramphenicol, co-trimoxazole, erythromycin, cefotaxime, and cefuroxime. Beta-lactamase-negative strains were uniformly susceptible to penicillin and ampicillin.     

Antimicrobial susceptibility of Bordetella bronchiseptica isolates from porcine respiratory tract infections

MICs for 349 Bordetella bronchiseptica isolates from respiratory tract infections of swine were determined by broth microdilution. The lowest MIC at which 90% of isolates tested are inhibited (MIC90) was that of tetracycline and enrofloxacin (0.5 microg/ml), whereas the highest MIC90s were those of tilmicosin and cephalothin (32 microg/ml) as well as streptomycin (256 microg/ml).     

临床来源碳青霉烯耐药大肠埃希菌药物敏感性及分子流行病学特征分析

目的 探讨临床分离的碳青霉烯耐药大肠埃希菌药物敏感性特征及分子流行病学特征,为院内感染控制及临床治疗提供基础数据。方法 收集某医院临床分离的21株对碳青霉烯类药物耐药的大肠埃希菌,采用琼脂稀释法测定菌株对11种临床常用药物的最低抑菌浓度（MIC）;Carba NP试验检测菌株产碳青霉烯酶情况;采用PCR扩增及序列比对检测耐药基因（包括blaNDM、blaKPC、blaIMP、blaVIM、blaOXA）携带状况;采用脉冲场凝胶电泳（PFGE）和多位点序列分型（MLST）对菌株进行分子分型。结果 21株碳青霉烯耐药大肠埃希菌中,对哌拉西林、头孢吡肟、头孢曲松、头孢他啶等-内酰胺类药物和左氧氟沙星耐药率为100.00%;对甲氧苄啶-磺胺甲恶唑的耐药率也高达76.19%;对米诺环素、阿米卡星和磷霉素的耐药率相对较低,分别为23.81%、23.81%和19.05%。Carba NP试验阳性菌株17株,均携带blaNDM-1基因,其余4种基因检测均为阴性。MLST显示21株菌株共有9种ST型别,其中携带blaNDM-1基因的大肠埃希菌主要为ST167型和ST540型。PFGE显示来自泌尿外科的3株菌株电泳图谱完全相同,另外来自不同病房的2株菌株电泳图谱也完全相同,提示医院内存在同一克隆菌株传播的可能。结论 该医院碳青霉烯耐药大肠埃希菌基因型分布呈现多态性;对碳青霉烯类药物耐药的机制主要是携带blaNDM-1基因;携带该基因的大肠埃希菌对临床常用抗菌药物往往呈现多重耐药,给临床治疗带来了困难。加强对碳青霉烯耐药菌株基因型和耐药基因的检测,将对减缓或阻断耐药菌的传播具有重要意义。     

Antimicrobial susceptibility of Brucella melitensis isolates in Peru

Brucellosis is an important public health problem in Peru. We evaluated 48 human Brucella melitensis biotype 1 strains from Peru between 2000 and 2006. MICs of isolates to doxycycline, azithromycin, gentamicin, rifampin, ciprofloxacin, and trimethoprim-sulfamethoxazole were determined by the Etest method. All isolates were sensitive to tested drugs during the periods of testing. Relapses did not appear to be related to drug resistance.     

Antimicrobial susceptibilities of clinical Desulfovibrio isolates

The antimicrobial susceptibilities of 16 clinical isolates of Desulfovibrio spp. were determined. All or most isolates were susceptible to imipenem (MIC(90) [MIC at which 90% of the isolates tested were inhibited], 0.5 microg/ml), metronidazole (MIC(90), 0.25 microg/ml), clindamycin (MIC(90), 4 microg/ml), and chloramphenicol (MIC(90), 16 microg/ml) but were resistant or intermediate to penicillin G (MIC(90), 64 microg/ml), piperacillin (MIC(90), 256 microg/ml), piperacillin-tazobactam (MIC(90), 256 microg/ml), cefoxitin (MIC(90), >256 microg/ml), and cefotetan (MIC(90), 64 microg/ml). Among isolates with decreased susceptibility to beta-lactams (n = 15), only six were beta-lactamase positive and susceptible to amoxicillin-clavulanate and ticarcillin-clavulanate.     

Antimicrobial susceptibility to azithromycin among Salmonella enterica isolates from the United States

Due to emerging resistance to traditional antimicrobial agents, such as ampicillin, trimethoprim-sulfamethoxazole, and chloramphenicol, azithromycin is increasingly used for the treatment of invasive Salmonella infections. In the present study, 696 isolates of non-Typhi Salmonella collected from humans, food animals, and retail meats in the United States were investigated for antimicrobial susceptibility to azithromycin. Seventy-two Salmonella enterica serotype Typhi isolates from humans were also tested. For each isolate, MICs of azithromycin and 15 other antimicrobial agents were determined by broth microdilution. Among the non-Typhi Salmonella isolates, azithromycin MICs among human isolates ranged from 1 to 32 μg/ml, whereas the MICs among the animal and retail meat isolates ranged from 2 to 16 μg/ml and 4 to 16 μg/ml, respectively. Among Salmonella serotype Typhi isolates, the azithromycin MICs ranged from 4 to 16 μg/ml. The highest MIC observed in the present study was 32 μg/ml, and it was detected in three human isolates belonging to serotypes Kentucky, Montevideo, and Paratyphi A. Based on our findings, we propose an epidemiological cutoff value (ECOFF) for wild-type Salmonella of ≤16 μg/ml of azithromycin. The susceptibility data provided could be used in combination with clinical outcome data to determine tentative clinical breakpoints for azithromycin and Salmonella enterica.     

Antimicrobial susceptibility of Bordetella avium and Bordetella bronchiseptica isolates.

Two veterinary pathogens, Bordetella bronchiseptica and Bordetella avium, were tested for their antimicrobial susceptibilities. Of the 20 antimicrobial agents tested, both species were consistently resistant to penicillin and cefuroxime but susceptible to mezlocillin, piperacillin, gentamicin, amikacin, and cefoperazone.     

Antimicrobial susceptibility and molecular determinants of quinolone resistance in Neisseria gonorrhoeae isolates from Shanghai

OBJECTIVES: To determine the antimicrobial susceptibility of Neisseria gonorrhoeae from Shanghai and to type the quinolone resistance-determining regions (QRDRs) of ciprofloxacin-resistant isolates. METHODS: N. gonorrhoeae isolates (n = 159) were consecutively collected from male patients in Shanghai and examined for their antimicrobial susceptibilities to penicillin, tetracycline, ciprofloxacin, spectinomycin and ceftriaxone. The mutation profiles of the QRDRs of gyrA and parC were determined for 103 isolates including one susceptible isolate and one isolate with intermediate levels of susceptibility to ciprofloxacin. RESULTS: High percentages of the 159 isolates were resistant to ciprofloxacin (98.7%), penicillin (93.1%) and tetracycline (56.5%). Penicillinase-producing N. gonorrhoeae (PPNG, 37.8%) or penicillinase-producing/tetracycline-resistant N. gonorrhoeae (PP/TRNG, 13.8%) accounted for 51.6% of the isolates. Chromosomal resistance to penicillin was observed in 41.5% of the isolates. Tetracycline resistance was noted in 56.5% of the isolates with 20.1% carrying plasmid-mediated resistance and 36.4% being chromosomally resistant. All isolates were susceptible to ceftriaxone and spectinomycin, although a trend to decreased susceptibility was noted. QRDR mutations were observed in the 101 ciprofloxacin-resistant isolates and the one ciprofloxacin-intermediate isolate, in contrast to the ciprofloxacin-susceptible isolate tested. Mutations in the QRDRs comprised four predominant (65.0% of the 103 isolates) patterns of a total of 19 patterns. Mutations in parC were significantly associated with higher MICs of ciprofloxacin. CONCLUSIONS: Spectinomycin and ceftriaxone are currently recommended for the treatment of gonorrhoea in Shanghai. Although the present study indicates that these antimicrobials should remain effective, the identification of isolates with decreased susceptibility underscores the importance of ongoing antimicrobial susceptibility surveillance to monitor and respond to the emergence of resistant isolates.     

Antimicrobial susceptibility and synergy studies of Stenotrophomonas maltophilia isolates from patients with cystic fibrosis

Stenotrophomonas maltophilia is a newly emerging pathogen being detected with increasing frequency in patients with cystic fibrosis (CF). The impact of this multidrug-resistant organism on lung function is uncertain. The optimal treatment for S. maltophilia in CF patients is unknown. We studied the in vitro activity of ten antimicrobial agents, and conducted synergy studies by using checkerboard dilutions of eight pairs of antimicrobial agents against strains isolated from 673 CF patients from 1996 to 2001. This represents approximately 7 to 23% of the CF patients in the United States who harbor S. maltophilia annually. Doxycycline was the most active agent and inhibited 80% of 673 initial patient isolates, while trimethoprim-sulfamethoxazole inhibited only 16%. High concentrations of colistin proved more active than high concentrations of tobramycin and gentamicin. Serial isolates (n = 151) from individual patients over time (median, 290 days) showed minimal changes in resistance. Synergistic or additive activity was demonstrated by trimethoprim-sulfamethoxazole paired with ticarcillin-clavulanate (65% of strains), ciprofloxacin paired with ticarcillin-clavulanate (64% of strains), ciprofloxacin paired with piperacillin-tazobactam (59% of strains), trimethoprim-sulfamethoxazole paired with piperacillin-tazobactam (55% of strains), and doxycycline paired with ticarcillin-clavulanate (49% of strains). In all, 522 (78%) isolates were multidrug resistant (i.e., resistant to all agents in two or more antimicrobial classes) but 473 (91%) of these were inhibited by at least one antimicrobial combination (median, four; range, one to eight). To determine appropriate treatment for patients with CF, it is important to monitor the prevalence, antimicrobial susceptibility, and clinical impact of S. maltophilia in this patient population.     

4551株临床分离细菌耐药性分析

目的分析我院2005年临床分离细菌对抗菌药物的耐药性。方法采用K-B纸片扩散法对4551株临床分离菌进行药敏试验,结果按NCCLS/CLSI2005年版标准判断及采用WHONET5.3软件进行统计分析。结果4551株细菌中革兰阴性菌3012株(66.2%),革兰阳性菌1539株(33.8%),非发酵菌占阴性菌的55.2%。MRSA和MRCNS检出率分别为68.6%和86.5%,未检测到万古霉素耐药株,也未发现万古霉素、替考拉宁耐药的粪肠球菌和屎肠球菌。大肠埃希菌、肺炎克雷伯菌ESBLs的发生率分别为55.8%、43.5%,亚胺培南和美罗培南对肠杆菌科细菌仍保持较高的敏感性(>96%)。鲍曼不动杆菌仅对头孢哌酮/舒巴坦的耐药率相对较低为35.7%,对亚胺培南和美罗培南的耐药率高达66.1%。铜绿假单胞菌对阿米卡星耐药率最低为14.7%,其次为头孢他啶、头孢吡肟、头孢哌酮/舒巴坦、氨曲南(23%～29%),对美罗培南的耐药率为25.2%,低于亚胺培南的33.4%。米诺环素对嗜麦芽窄食单胞菌、脑膜炎败血性黄杆菌、洋葱伯克霍尔德菌有较好的抗菌活性(耐药率<10%)。结论我院分离的细菌特别是鲍曼不动杆菌耐药性较为严重,应引起重视。