Streptococcus faecalis: in vitro susceptibility to antimicrobial drugs, single and combined, with and without defibrinated human blood

Ampicillin, fusidic acid, gentamicin, imipenem, mezlocillin, ofloxacin, penicillin G, piperacillin, and vancomycin were examined for inhibitory and bactericidal activity in various broth media against 7 clinical isolates of Streptococcus faecalis. On a weight-for-weight basis, ampicillin, imipenem, mezlocillin, and ofloxacin proved to be more efficacious. All enterococcal isolates were resistant against gentamicin; fusidic acid and vancomycin lacked bactericidal activity. The combinations of either ampicillin, imipenem, mezlocillin, ofloxacin, piperacillin, or vancomycin with a subinhibitory concentration (4 micrograms/ml) of gentamicin, with or without added 65% (v/v) fresh defibrinated human blood, respectively, yielded additive effects against all enterococcal isolates. The addition of fresh human blood failed to enhance the antienterococcal activity of 4 micrograms/ml of gentamicin; in contrast, addition of 65% (v/v) fresh or heat-inactivated (56 degrees C, 30 min) normal rabbit, bovine, and human sera augmented the activity of gentamicin, an effect that was ablated through the addition of either 0.005 M DTT or 0.01 M MgCl2 + 0.01 M EGTA + 0.01 M CaCl2, supplements known to antagonize human serum beta-lysin, but not lysozyme activity.     

Susceptibility of Acinetobacter calcoaceticus to antimicrobial drugs, alone and combined, with and without defibrinated human blood

Twenty-five clinical isolates of Acinetobacter calcoaceticus were examined for susceptibility to 14 antimicrobial drugs. In terms of inhibitory and bactericidal activities, imipenem and polymyxin B were most active, followed by amikacin and ceftazidime. Four isolates were resistant against fluoroquinolones (ciprofloxacin, norfloxacin, ofloxacin). The isolates varied in susceptibility to aztreonam, cefotaxime, cotrimoxazole, gentamicin, mezlocillin, netilmicin and piperacillin. Fresh defibrinated human blood from 3 donors revealed similar killing kinetics against 8 selected isolates. In time-kill curve experiments, human blood enhanced the activity of amikacin more than that of ceftazidime, ciprofloxacin and imipenem against A. calcoaceticus. The combinations of amikacin + imipenem and amikacin + ceftazidime in the presence of human blood were effective against this microorganism. Human blood combined with ciprofloxacin + imipenem was more effective than blood with added ceftazidime + ciprofloxacin.     

Pseudomonas aeruginosa: in vivo (murine) activity of five antimicrobial drugs, with and without human IgG immunoglobulin preparations

Five antimicrobial drugs (ceftazidime, ciprofloxacin, imipenem, piperacillin and tobramycin) and two human, intravenously applicable, IgG immunoglobulin preparations (Psomaglobin, Polyglobin N) were examined alone and in various combinations for therapeutic efficacy in myelosuppressed as well as normal NMRI mice following systemic infection with 4 selected strains of Pseudomonas aeruginosa. Both IgG preparations alone invariably failed to passively protect neutropenic and normal mice, even though the preparations contained demonstrable antibodies against purified exotoxin A of P. aeruginosa and against numerous polypeptide and lipopolysaccharide constituents of the 4 test strains of P. aeruginosa. Among the antimicrobial drugs employed alone, ciprofloxacin and imipenem were the most effective. Tobramycin alone occupied an intermediate position, whereas monotherapy with ceftazidime and piperacillin invariably failed. All antimicrobial drug combinations were efficacious in myelo-suppressed as well as normal mice. Both IgG preparations failed to enhance the activities of ceftazidime and piperacillin in neutropenic mice; the activity of tobramycin was augmented against 1 of 2 P. aeruginosa strains, as well as that of ciprofloxacin. Both IgG preparations enhanced the activities of ceftazidime and tobramycin in normal NMRI mice, as well as that of piperacillin against 1 of 2 test strains. It was concluded that the two IgG preparations were more beneficial for normal rather than neutropenic mice, provided that the animals were treated with appropriate antimicrobial drugs as well.     

铜绿假单胞菌对10种抗菌药物敏感性分析

目的调查我院临床分离的铜绿假单胞菌对10种抗菌药物的敏感性,分析其多重耐药特点,指导临床用药.方法收集我院2002-2004年临床分离368株铜绿假单胞菌,使用Kirby-Bauer纸片琼脂扩散法测定其对10种抗菌药物的抑菌环直径,按NCCLS 2002年规定判读结果.结果ICU分离菌对亚胺培南和美罗培南耐药率为54.3%和52.2%,分别高于非ICU28.8个百分点和34.7个百分点（P＜0.01）,对头孢吡肟、头孢他啶和氨曲南的耐药率高于非ICU 10.2～12.6个百分点（P＜0.05）;呼吸道标本分离株对哌拉西林、哌拉西林-三唑巴坦、头孢吡肟、亚胺培南、美罗培南、环丙沙星、庆大霉素和阿米卡星的耐药率高出非呼吸道标本12.2～25.4个百分点（P＜0.01）,对头孢他啶的耐药率比非呼吸道标本高10.1个百分点（P＜0.05）.结论我院ICU和呼吸道标本分离铜绿假单胞菌对多种抗菌药物的耐药率高于非ICU和非呼吸道标本分离株.     

Combined defibrinated human blood and antimicrobial drug activities against Enterobacter cloacae

The combinations of 11 antimicrobial drugs and fresh human defibrinated blood were examined for potential additive effects against several isolates of Enterobacter cloacae recovered from patients with bacteremia or meningitis. Aminoglycosides (amikacin, gentamicin, netilmicin) proved most efficacious, followed by cephalosporins (lamoxactam, cefotaxime, ceftizoxime) and ureidopenicillins (mezlocillin, piperacillin). Nalidixic acid, nitrofurantoin, and cotrimoxazole yielded indifferent effects. The E. cloacae isolates displayed low virulence for outbred NMRI mice.     

Gentamicin- and methicillin-resistant Staphylococcus aureus: in vitro susceptibility to antimicrobial drugs

Thirteen nosocomially significant, gentamicin- and methicillin-resistant (GRMR) Staphylococcus aureus isolates, all of phage group III/M (lysotype 42E/47/53/54/75/77/83A/84/85/94/96), were uniformly resistant against augmentin, erythromycin, fosfomycin, gentamicin, methicillin, oxacillin, penicillin G, tetracycline, and tobramycin, but differed in susceptibility to cefamandole, ciprofloxacin, clindamycin, imipenem, josamycin, the synthetic chinolone Ro 23-6240, and ofloxacin. All isolates were susceptible to chloramphenicol, coumermycin, fusidic acid, novobiocin, rifampin, teicoplanin, trimethoprim-sulfamethoxazole (cotrimoxazole), and vancomycin. One isolate was of intermediate susceptibility to netilmicin. On a weight-for-weight basis, the 7 most active drugs were rifampin, coumermycin, cotrimoxazole, novobiocin, teicoplanin, fusidic acid, and vancomycin (in decreasing order) in terms of minimal inhibitory concentrations. With regard to minimal bactericidal concentrations, coumermycin, rifampin, vancomycin, teicoplanin, cotrimoxazole, ofloxacin, and ciprofloxacin (in decreasing order) were the 7 most potent antimicrobial drugs. Freshly defibrinated human blood [65% (v/v)] combined with chloramphenicol and rifampin, respectively, resulted in a weak additive effect (time kill curves). Indifferent effects were observed following combination of blood with ciprofloxacin, cotrimoxazole, coumermycin, fusidic acid, imipenem, netilmicin, novobiocin, ofloxacin, compound Ro 23-6240, teicoplanin, and vancomycin. Rifampin combined with novobiocin, teicoplanin, and vancomycin, respectively, in the presence of 65% (v/v) human blood, resulted in an additive effect. Combinations of rifampin with 9 other antimicrobial drugs in blood yielded essentially indifferent effects.     

Pseudomonas aeruginosa bacteremia: susceptibility of 100 blood culture isolates to seven antimicrobial agents and its clinical significance.

The susceptibility of 100 blood culture isolates of Pseudomonas aeruginosa observed during 4 1/2 years was tested for tobramycin, netilimicin, gentamicin, amikacin, pirbenicillin, ticarcillin and carbenicillin, singly and in combination. For aminoglycosides, the agar MICs were twofold to threefold greater than tube dilution MICs but for the penicillins they were similar. For aminoglycosides and ticarcillin, the MBCs were twofold greater than the tube dilution MICs. The MBCs were not achieved at concentrations as high as 512 micrograms/ml for 40% of the isolates for pirbenicillin and for 10% for carbenicillin. Tobramycin and pirbenicillin had the lowest MICs for the aminoglycosides and penicillins, respectively. Synergism was tested and observed between tobramycin + ticarcillin and amikacin + ticarcillin. No overall increase in resistance to gentamicin or carbenicillin was seen from 1974 to 1977. However, patients given repeated courses of gentamicin had more resistant strains. Following the administration of 1.5 mg/kg/dose of gentamicin, peak serum concentrations failed to achieve the MIC for the microorganism in 22% of the patients. The MIC was achieved in all patients receiving the same dose of tobramycin. The overall fatality rate was 67% with one third of the patients dying within 36 hr. There was no relationship of patient fatality rate and MIC for the microorganism. Although in the rapidly fatal group of all patients receiving inappropriate therapy died, the fatality rates of appropriately or inappropriately treated patients in the ultimately fatal and nonfatal groups were similar. Underlying host disease was the major determining factor in patient survival.     

Interactions of antimicrobial drugs and combined phagocytic/serum bactericidal activity of defibrinated human blood against Serratia marcescens. IV. N-formimidoyl thienamycin

Minimal bactericidal concentrations of thienamycin revealed moderate intraphagolysosomal bactericidal activity against pseudo-(PSR) and genuinely serum-resistant (NSS) assay strains of Serratia marcescens. Combinations of inhibitory and subinhibitory concentrations of thienamycin with 55 vol% of defibrinated human blood resulted in additive effects against all PSR and NSS test strains of S. marcescens and against the NSS Escherichia coli control strain ATCC 25922.     

2014年中国云南地区铜绿假单胞菌耐药监测

目的 监测2014年中国云南地区铜绿假单胞菌临床分布及耐药情况.方法 收集2014年1-12月国家卫生和计划生育委员会全国细菌耐药监测网云南省28家三级医院的监测资料,按统一的方案进行铜绿假单胞菌的培养、分离、鉴定和药敏试验,判断标准按CLSI M100-S24,用Whonet5.6软件进行数据统计分析.结果 2014年云南地区28家三级医院共分离出2 873株铜绿假单胞菌,其中90.36%分离自住院患者,菌株按标本来源主要分离自痰液(60.32%)、尿(8.42%)、分泌物(8.11%)、脓液(4.70%)、血液(2.92%)等.铜绿假单胞菌对常见抗菌药物敏感度前5位依次为阿米卡星(88.7%)、哌拉西林/他唑巴坦(85.0%)、妥布霉素(83.1%)、哌拉西林(80.3%)、头孢吡肟(80.1%).对氨曲南的耐药率为59.0%;对亚胺培南、头孢他啶、美罗培南、左氧氟沙星、环丙沙星的耐药率处于20.9%~29.7%;对哌拉西林、庆大霉素、头孢吡肟、妥布霉素、哌拉西林/他唑巴坦、阿米卡星的耐药率处于10.3%~19.9%.结论 2014年中国云南地区临床分离的铜绿假单胞菌对抗菌药物的耐药性相差较大,医疗机构应加强细菌耐药监测,指导临床合理使用抗菌药物.     

In vitro susceptibility of Pseudomonas aeruginosa to carbenicillin, glycine, and ethylenediaminetetraacetic acid combinations

Striking bacterial activity against Pseudomonas aeruginosa 9D-2 was achieved by glycine-carbenicillin, ethylenediaminetetraacetic acid-carbenicillin, and glycine-ethylenediaminetetraacetic acid combinations, whereas none of the agents used alone was capable of the same degree of bactericidal activity. Studies using a microtiter modification of the checkerboard technique were performed to evaluate the comparative activity of these antimicrobial combinations. Isobolograms showed synergistic effects with carbenicillin-glycine, carbenicillin-ethylene-diaminetetraacetic acid, and glycine-ethylenediaminetetraacetic acid combinations. Bacterial growth inhibitory curves with subinhibitory concentrations of these agents in combination confirmed these findings.     

Interactions of antimicrobial drugs and combined phagocytic/serum bactericidal activity of defibrinated human blood against Serratia marcescens. III. beta-Lactam antibiotics and fosfomycin

Neither cefoperazone, cefotaxime, mezlocillin nor piperacillin significantly killed intraphagocytic bacteria of representative assay strains of Serratia marcescens, as determined with 55 vol% of fresh defibrinated human blood treated with 2 mg/ml of phenylbutazone, which permitted phagocytic ingestion of bacteria, but selectively inhibited the microbicidal activity of peripheral blood leukocytes. Extraphagocytic bacteria were killed with group A (phage tail) bacteriocins of S. marcescens. However, minimal bactericidal concentrations of fosfomycin displayed intraphagolysosomal bactericidal activity which approximated that of rifampin. Inhibitory and subinhibitory concentrations of cefoperazone, cefotaxime, fosfomycin, mezlocillin, and piperacillin combined with 55 vol% of defibrinated human blood, respectively, yielded additive effects against all test strains of S. marcescens utilized and Escherichia coli control strain ATCC 25922.     

Hyperoxia and the antimicrobial susceptibility of Escherichia coli and Pseudomonas aeruginosa.

We have tested the ability of hyperoxia (98% O2-2% CO2 at 2.8 atmospheres absolute [ca. 284.6 kPa]) to enhance killing of Escherichia coli (serotype O18 or ATCC 25922) by nitrofurantoin, sulfamethoxazole, trimethoprim, gentamicin, and tobramycin. We have also looked for interactions between hyperoxia and the aminoglycosides against Pseudomonas aeruginosa ATCC 27853. Hyperoxia significantly enhanced bacteriostatic activity of nitrofurantoin and trimethoprim as measured by MIC testing. The possibility exists that these effects might be due to the method required to tests MICs under hyperoxic conditions rather than to the effect of hyperoxia itself. In addition, hyperoxia enhanced killing of bacteria by trimethoprim as measured by MBC testing. Hyperoxia decreased numbers of E. coli by 1.3 log10 and P. aeruginosa by 2.7 log10 in cation-supplemented Mueller-Hinton broth medium. The bacteriostatic effects of hyperoxia did not affect MICs of gentamicin or tobramycin. The lack of interaction between hyperoxia and gentamicin or tobramycin was confirmed by determining the number of viable bacteria remaining after 24 h of exposure to hyperoxia by using a pour plate method. We conclude that hyperoxia potentiates the antimicrobial activity of the reduction-oxidation-cycling antibiotic tested (nitrofurantoin) and of one of the antimetabolites tested (trimethoprim). Hyperoxia does not enhance the bactericidal effects of gentamicin and tobramycin, which require oxidative metabolism for transport into bacterial cells.     

广州地区耐亚胺培南铜绿假单胞菌的感染现状及耐药性检测

目的调查广州地区耐亚胺培南铜绿假单胞菌在医院内的感染现状及耐药谱特性,帮助临床合理选用抗生素。方法用VITEK-32型全自动细菌分析系统筛选广东省中医院、南方医院、广州中医药大学附属第一医院、中山大学附属第二医院2005-2007年期间耐亚胺培南铜绿假单胞菌,并用琼脂稀释法检测其对亚胺培南的最低抑菌浓度。结果440株铜绿假单胞菌中,耐亚胺培南81株（18．41％）。在所测试的抗生素中,耐亚胺培南菌株组与非耐亚胺培南菌株组之间的耐药率差异明显,尤以庆大霉素（分别为65．43％、10．86％）、头孢他啶（分别为53．09％、10．03％）和阿米卡星（分别为53．09％、12．26％）显著。结论耐亚胺培南铜绿假单胞菌对多种抗生素耐药,且耐药率有逐年增高的趋势,在治疗时应根据药敏试验结果合理谨慎选用抗生素,有效控制及减缓耐药株的产生。     

Quality of antimicrobial susceptibility testing in the UK: a Pseudomonas aeruginosa survey revisited.

As part of a programme to assess the usefulness of routine antimicrobial susceptibility data as a surveillance tool, we reviewed the results of a national survey of resistance in Pseudomonas aeruginosa, undertaken in 1993. Twenty-four UK laboratories contributed isolates for centralized MIC testing, indicating also their own susceptibility test data. As reported previously (Chen et al. (1995) Journal of Antimicrobial Chemotherapy 35, 521-34), the rate of false resistance (isolates reported susceptible, but found resistant on MIC testing/all isolates reported susceptible) was 0.6-8%, according to the antimicrobial and breakpoint. Review showed that this favourable position reflected the fact that >88% of isolates were susceptible to any given antimicrobial and--in most cases--were correctly reported as such. Reporting was more erratic for resistant isolates: for beta-lactams and amikacin, isolates resistant at the highest MIC breakpoints were equally likely to be reported as 'susceptible' or 'resistant'; such misreporting was less common with ciprofloxacin and gentamicin but still occurred in 9-20% of cases. Conversely, up to 73% of the isolates reported as resistant proved to be susceptible at high breakpoints, and up to 44% were susceptible at low breakpoints. Miscategorizations did not reflect failure to detect particular mechanisms but, rather, the fact that MIC and zone breakpoints for P. aeruginosa serve to cut 'tails' of resistant organisms from continuous distributions, not to distinguish discrete populations. In this situation, some disagreement between routine tests and MICs is inevitable, but the frequency at which highly resistant isolates were reported as sensitive is disturbing. For surveillance, we conclude that resistance rates based on routine tests are unreliable for P. aeruginosa. This situation may improve with greater standardization of routine testing, but the continuous susceptibility distributions without discrete resistant and susceptible populations militate against perfect agreement. Despite these deficiencies, routine data should allow trend analysis.     

铜绿假单胞菌高活性β内酰胺酶检测及其耐药性分析

目的:研究临床分离铜绿假单胞菌(PA)持续高产AmpC酶和超广谱β内酰胺酶(ESBLs)的发生率及对耐药性的影响。方法:用改良三维试验法检验持续高产AmpC酶和ESBLs,用K—B法检测细菌耐药性。结果:我院2001年3月-2002年10月临床分离241株PA中,产生高活性β内酰胺酶共83株,检出率为34.4％,其中高产AmpC酶28株(11.6％),产ESBLs69株(28.6％),ESBLs与高产AmpC酶均阳性21株(8.7％),非AmpC酶、非ESBLs 7株(2.9％)。83株产酶PA主要分离自痰液(56株,67.5％)和烧伤创面分泌物(23株,27.7％)。易感人群以重症肺炎(34例,41.0%)、烧伤(23例,27.7 %)和肿瘤患者(10例,12.0%)为主。产酶株呈多重耐药性,对亚胺培南耐药率为10.8％,对受试的其他11种抗菌药物耐药率在49.4％～86.7％;除亚胺培南外,产酶株耐药率均明显高于非产酶株(X2≥16.1,P<0.005)。结论:我院PA临床株产ESBLs为主(约28.6％),其次是持续高产AmpC酶(约11.6％)。产酶株主要分离自重症肺炎、烧伤和肿瘤患者,其耐药率高,治疗用药应参考药敏试验结果。     

Oxacillinase-mediated resistance to cefepime and susceptibility to ceftazidime in Pseudomonas aeruginosa

Pseudomonas aeruginosa clinical isolate SOF-1 was resistant to cefepime and susceptible to ceftazidime. This resistance phenotype was explained by the expression of OXA-31, which shared 98% amino acid identity with a class D beta-lactamase, OXA-1. The oxa-31 gene was located on a ca. 300-kb nonconjugative plasmid and on a class 1 integron. No additional efflux mechanism for cefepime was detected in P. aeruginosa SOF-1. Resistance to cefepime and susceptibility to ceftazidime in P. aeruginosa were conferred by OXA-1 as well.     

In vitro activities of tritrpticin alone and in combination with other antimicrobial agents against Pseudomonas aeruginosa

The in vitro activity of the cathelicidin tritrpticin was investigated against multidrug-resistant Pseudomonas aeruginosa. The isolates were susceptible to the peptide at concentrations of 0.50 to 8 mg/liter. Tritrpticin completely inhibits lipopolysaccharide procoagulant activity at a 10 microM concentration. Fractionary inhibitory concentration indexes (0.385, 0.312, and 0.458) demonstrated synergy between the peptide and beta-lactams.     

Pseudomonas aeruginosa and Acinetobacter calcoaceticus: in vitro susceptibility of 150 clinical isolates to five beta-lactam antibiotics and tobramycin

The in vitro activities of azlocillin, carbenicillin, ceftriaxone, piperacillin, N-formimidoyl thienamycin (N-f thienamycin) and tobramycin have been compared against clinical isolates of Pseudomonas aeruginosa (n = 100) and Acinetobacter calcoaceticus (n = 50). An agar dilution method was employed for measurement of minimal inhibitory concentration (MIC). Tobramycin was the most active drug against P. aeruginosa (MIC less than or equal to 2 mg/l). Of the beta-lactam antibiotics, N-f thienamycin and tobramycin were highly active against A. calcoaceticus (MIC less than or equal to 2 mg/l), although one isolate was resistant to tobramycin (MIC greater than 16 mg/l). The other drugs were only moderately active against A. calcoaceticus.     

Changes in susceptibility of Pseudomonas aeruginosa to gatifloxacin and carbapenem in an in vitro urinary bladder model

To study the changes of bacterial susceptibility during exposure to antimicrobials, the respective minimal inhibitory concentrations (MICs) of 50 colonies from each of various bacterial test strains were determined in an experimental system using an in vitro urinary bladder model. The MICs of gatifloxacin and meropenem for Pseudomonas aeruginosa strains were not homogeneous before exposure to the drugs. The MICs of the strains examined reflected only that of their dominant population. When starting from 10(7)CFU/ml, the bacterial count was determined serially during exposure to gatifloxacin or meropenem in therapeutic urinary concentrations. The MIC of the less susceptible population of each strain was changed serially to a higher one. The more susceptible strains were eradicated before the change of the MIC. The bacteria originally consisted of strains having heterogeneous susceptibility to drugs, in which major strains had susceptibility expressed by the MIC and minor ones had a higher or lower MIC. This heterogeneity may be responsible for the change of susceptibility in strains after exposure to the drugs.