IS256与医院感染表皮葡萄球菌耐氨基糖苷类抗菌药物的关系

目的了解医院感染表皮葡萄球菌对不同类型氨基糖苷类抗菌药物的敏感特征,分析插入序列(IS)256与表皮葡萄球菌耐氨基糖苷类抗菌药物的关系。方法收集2007年2月至2007年7月外科病区中引起医院感染的表皮葡萄球菌48株,利用纸片扩散法测定细菌对4种氨基糖苷类抗菌药物(庆大霉素、奈替米星、链霉素和阿米卡星)药敏特征;构建IS256特异性引物,利用聚合酶链反应(PCR)检测48株细菌中IS256分布状况。结果48株临床分离的表皮葡萄球菌对4种氨基糖苷类抗菌药物的药敏特征分别为:对庆大霉素的耐药率为69%,敏感率为31%;对奈替米星的耐药率为8%,敏感率为79%,中介率为13%;对链霉素的耐药率为42%,敏感率为35%,中介率为23%;对阿米卡星的耐药率为15%,敏感率为75%,中介率为10%。全部临床分离株中,有25株细菌检出IS256。在庆大霉素耐药菌株中,IS256检出率高达70%,与敏感菌相比差异具有统计学意义(P<0.01);而对其他3种抗菌药物耐药的菌株中,IS256的检出与耐药无明显相关性(P>0.05)。结论表皮葡萄球菌临床分离株对氨基糖苷类抗菌药物存在不同程度耐药。IS256与表皮葡萄球菌对庆大霉素耐药密切相关。     

表皮葡萄球菌icaADBC操纵子检出与细菌耐氨基糖苷类抗菌药物的关系

目的分析临床分离表皮葡萄球菌对不同类型氨基糖苷类抗菌药物的耐药特征;分析icaADBC操纵子在临床分离的表皮葡萄球菌中的检出及与细菌耐药的关系。方法收集2013年1~10月上海市东方医院临床分离的表皮葡萄球菌77株,采用纸片扩散法检测细菌4种氨基糖苷类抗菌药物(庆大霉素、链霉素、奈替米星和阿米卡星)药敏试验特征;构建icaADBC特异性引物,采用聚合酶链反应扩增技术检测77株细菌中icaADBC的分布状况。结果结果77株表皮葡萄球菌对氨基糖苷类抗菌药物耐药率较高,分别为庆大霉素:62.3%,链霉素:61.0%,阿米卡星:22.1%,奈替米星:23.4%。icaADBC操纵子的检出率为20.8%,ica阳性菌株与阴性菌株对氨基糖苷类抗菌药物耐药性比较差异有统计学意义(P0.05)。结论临床分离的icaADBC操纵子阳性表皮葡萄球菌对氨基糖苷类抗菌药物耐药率较高。     

广州地区产AmpC酶肺炎克雷伯菌耐药性及氨基糖苷类修饰酶基因分析

目的调查广州地区临床分离产AmpC酶肺炎克雷伯菌对抗菌药物耐药性及氨基糖苷类修饰酶基因分布。方法采用纸片扩散法（即K-B法）测定51株产AmpC肺炎克雷伯菌对15种抗菌药物的耐药情况，聚合酶链反应（PCR）分析ampC和氨基糖苛修饰酶基因型。结果51株产AmpC肺炎克雷伯菌呈现多重耐药，对阿米卡星、庆大霉素、妥布霉素和奈替米星的耐药率分别为39.2％、66.7％、58.8％和43.1％，除亚胺培南外其余抗生素耐药率在47.0％-100％；41株（80.3％）检出氨基糖苷修饰酶基因。结论临床分离的产AmpC酶肺炎克雷伯菌多重耐药严重，氨基糖苷修饰酶基因携带率很高。     

多重耐药鲍曼不动杆菌对氨基糖苷类药物耐药性及其耐药基因(ant)的研究

目的了解多重耐药鲍曼不动杆菌对氨基糖苷类药物修饰酶的耐药性及其耐药基因。方法用琼脂稀释法检测庆大霉素、阿米卡星、链霉素、卡那霉素、妥布霉素、奈替米星、新霉素7种药物对20株多重耐药性鲍曼不动杆菌的最低抑菌浓度（MIC）；用PCR法检测两种氨基糖苷类药物核苷转移酶基因，并使用DNA测序加以证实。结果庆大霉素、阿米卡星、链霉素、卡那霉素对20株鲍曼不动杆菌的MIC50和MIC90均大于1024mg／L，耐药率分别为95％、95％、100％和90％；而妥布霉素、奈替米星和新霉素的耐药率分别为85％、90％、40％。从20株菌中检出ant（2”）-I、ant（3”）-I两种修饰酶基因，阳性率分别为55％、80％，10株细菌两种基因同时阳性，占50％。结论鲍曼不动杆菌对氨基糖苷类药物耐药与ant（2”）-I、ant（3”）-I基因有非常密切的关系。     

广州地区产AmpC酶肺炎克雷伯菌耐药性及氨基糖苷类修饰酶基因分析

目的调查广州地区临床分离产AmpC酶肺炎克雷伯菌对抗菌药物耐药性及氨基糖苷类修饰酶基因分布。方法采用纸片扩散法（即K-B法）测定51株产AmpC肺炎克雷伯菌对15种抗菌药物的耐药情况，聚合酶链反应（PCR）分析ampC和氨基糖苛修饰酶基因型。结果51株产AmpC肺炎克雷伯菌呈现多重耐药，对阿米卡星、庆大霉素、妥布霉素和奈替米星的耐药率分别为39.2％、66.7％、58.8％和43.1％，除亚胺培南外其余抗生素耐药率在47.0％-100％；41株（80.3％）检出氨基糖苷修饰酶基因。结论临床分离的产AmpC酶肺炎克雷伯菌多重耐药严重，氨基糖苷修饰酶基因携带率很高。     

阴沟肠杆菌16SrRNA甲基化酶基因分布

目的：了解湖南邵阳地区耐氨基糖苷类抗菌药物的阴沟肠杆菌中16S rRNA甲基化酶基因分布特点及其与氨基糖苷类抗菌药物耐药性的关系。方法收集2012年8月至2014年5月邵阳地区新宁县人民医院、武岗市人民医院、邵阳县人民医院和邵阳医学高等专科学校附属医院临床样本中分离的241株阴沟肠杆菌,采用API20E进行菌种鉴定,同时用纸片扩散法进行体外药物敏感性试验。采用聚合酶链反应（ PCR）进行armA、npmA、rmtA、rmtB、rmtC和rmtD基因检测,分析耐药基因与耐药表型的关系。结果241株阴沟肠杆菌中200株对阿米卡星、庆大霉素、妥布霉素和奈替米星4种氨基糖苷类抗菌药物耐药,其耐药率分别为41．9％、68．5％、70．1％和63．5％。基因检测结果提示,241株阴沟肠杆菌检出2种16S rRNA甲基化酶基因,分别为armA（96株,39．8％）和rmtB（17株,7．1％）,未检出npmA、rmtA、rmtC和rmtD基因。结论16S rRNA甲基化酶与氨基糖苷类抗菌药物的耐药性有相关性。不同地区分离的对氨基糖苷类药物耐药的阴沟肠杆菌菌株携带16S rRNA甲基化酶的基因型有一定差异,湖南邵阳地区阴沟肠杆菌以携带armA基因为主。     

铜绿假单胞菌氨基糖苷类修饰酶基因与耐药表型的研究

目的探讨临床分离的22株铜绿假单胞菌（Pa）氨基糖苷类修饰酶（AMES）基因与耐药表型的关系。方法对22株铜绿假单胞菌采用稀释法检测庆大霉素、阿米卡星、奈替米星、妥布霉素4种抗菌药物的最低抑菌浓度（MIC），并用聚合酶链反应（PCR）法检测6种氨基糖苷类修饰酶基因。结果本组22株Pa菌庆大霉素耐药15株（68．2％）、阿米卡星耐药3株（13．6％）、奈替米星14株（63．6％）、妥布霉素15株（68．2％），检出aac（3）-Ⅰ阳性14株（63．6％）、aac（6’）-Ⅰ阳性5株（22．7％）、aac（6’）-Ⅱ阳性3株（13．6％）、ant（3”）-Ⅰ阳性1株（4．5％）和ant（2”）-Ⅰ阳性7株（31．8％），aac（3）．Ⅰ为阴性。共有18株检出氨基糖苷类修饰酶基因（81．8％）。结论分离自临床的铜绿假单胞菌氨基糖苷类修饰酶基因检出率高，且与耐药表型一致。     

铜绿假单胞菌氨基糖苷类药物修饰酶基因研究

目的 调查铜绿假单胞菌对常用抗生素的耐药特性及氨基糖苷类药物修饰酶基因表达。方法 用Phoenix^TM-100系统鉴定细菌和药敏试验。用琼脂扩散法检测20株多重耐药铜绿假单胞菌对阿米卡星、庆大霉素、妥布霉素和奈替米星4种药物的敏感性。采用聚合酶链反应（PCR）扩增4种氨基糖苷类药物修饰酶基因，并使用DNA测序加以证实。结果 190株铜绿假单胞菌对氯霉素、四环素、复方磺胺耐药率最高，均为98．9％；对亚胺培南、美洛培南的耐药率分别为15．3％和6．8％。从20株菌中检出aac（6′）-Ⅰ、aac（6′）-Ⅱ和ant（2″）-Ⅰ3种修饰酶基因，阳性率分别为10％、60％和65％，未发现ant（3″）-Ⅰ基因。20株菌对阿米卡星、庆大霉素、妥布霉素和奈替米星的耐药率分别为35．0％、90．0％、70．0％、60．0％。结论 本地区铜绿假单胞菌对氨基糖苷类药物的耐药与修饰酶基因的传播表达有关。     

507株临床分离菌对抗菌药物耐药性分析

目的：了解我院细菌耐药性现状。方法：采用美国国家临床实验室标准委员会（NCCLS）推荐的纸片扩散法（K-B法）测定2000年4月-2001年3月临床微生物室临床分离507株细菌对29种临床常用抗菌药物进行药物敏感试验。结果：88株葡萄球菌中金黄色葡萄球菌和凝固酶阴性葡萄球菌中甲氧西林耐药株分别为75.4％和80％，耐甲氧西林菌株对其他抗菌药物的耐药的耐药率均明显高于甲氧西林敏感菌株，未发现葡萄球菌和肠球菌对万古霉素耐药。糖发酵革兰阴性杆菌中对氨苄西林高度耐药，对第三代头孢菌素，以及亚胺培南、美罗培南、帕尼培南高度敏感，耐药率均低于20％，细菌对亚胺培南的耐药率均在5％以下，铜绿假单胞菌对阿米卡星、庆大霉素、头孢他啶、头孢哌酮、亚胺培南、症状罗培南和头孢哌酮-舒巴坦呈高度敏感，耐药率均在10％以下，不动杆菌对氨苄西林-舒巴培高度敏感，耐药率仅10％。结论：了解致病菌的耐药性，有利于临床诊断和合理使用抗菌药物，对细菌耐药性监测十分重要。     

36株多重耐药鲍曼不动杆菌对氨基糖苷类药物耐药基因的流行病学研究

目的了解多重耐药鲍曼不动杆菌中氨基糖苷类耐药基因的存在情况。方法收集2012年8—11月江苏大学附属医院和镇江市第一人民医院住院患者的临床标本中分离到的多重耐药鲍曼不动杆菌菌株36株。应用KB纸片扩散法检测多重耐药鲍曼不动杆菌对抗菌药物的敏感性、应用PCR检测细菌对氨基糖苷类药物的耐药基因。结果36株多重耐药鲍曼不动杆菌对头孢哌酮一舒巴坦有较高的敏感率（33．3％）,对其他抗菌药物的敏感率均较低（20．0％）。36株多重耐药鲍曼不动杆菌中氨基糖苷类耐药基因aac（3）-I、aac（6’）Ib、aph（3’）-I和16SrRNA甲基化酶基因armA的阳性率分别为72．2％（26株）、72．2％（26株）、80．6％（29株）和80．6％（29株）。结论本组多重耐药鲍曼不动杆菌多耐药情况比较严重,其对氨基糖苷类药物耐药与氨基糖苷类耐药基因的存在密切相关。     

The prevalence of high-level aminoglycoside resistance among enterococci isolated from blood cultures during 1980-1988

Two hundred and eighty-one strains of enterococci isolated from blood cultures of 281 consecutive patients during 1980-1988 and 108 strains of enterococci isolated from miscellaneous clinical materials during 1988 were studied for high-level resistance (MIC greater than 2000 mg/l) to amikacin, kanamycin, streptomycin, gentamicin, tobramycin and netilmicin. Before 1985 there was no enterococcal strain with high-level resistance to amikacin, gentamicin, tobramycin or netilmicin, but 14% were resistant to kanamycin and 21% to streptomycin. For strains isolated from blood cultures during 1985-1988, the prevalence of high-level resistance was as follows: amikacin, less than 1%; kanamycin, 35%; streptomycin, 26%; gentamicin, 9%; tobramycin, 9%, netilmicin, 4%. Prevalence of high-level aminoglycoside resistance of enterococci isolated from miscellaneous sources during 1988 was higher (amikacin, 5%; kanamycin, 37%; streptomycin, 31%; gentamicin, 24%, tobramycin, 27%; netilmicin, 10%). Among strains isolated from blood cultures between 1980-1984, 24% (30 of 126 strains) and among 1985-1988 strains, 40% (62 of 155 strains) were resistant to at least one of the aminoglycosides tested. Similarly, among the miscellaneous strains, 40% (43 of 108 strains) had high-level resistance to at least one of the aminoglycosides tested.     

Susceptibility of Hong Kong isolates of methicillin-resistant Staphylococcus aureus to antimicrobial agents

Two hundred and sixty-six non-replicate Hong Kong isolates of methicillin-resistant Staphylococcus aureus were tested for their susceptibility to various anti-staphylococcal agents. Multiple resistance was common. More than 95% of patient isolates were resistant to both gentamicin and tetracycline, 68% to erythromycin, 37% to chloramphenicol, 10% to trimethoprim, 5% to rifampicin and 2% to fusidic acid. No isolate was resistant to all these agents, but nineteen different patterns of resistance were identified. Selected gentamicin-resistant isolates were tested against other aminoglycosides, and were sensitive to amikacin and netilmicin. The pattern of aminoglycoside resistance indicated that all isolates produced the aminoglycoside-modifying enzymes APH-(2") and AAC-(6')-I. All isolates were sensitive to vancomycin and teicoplanin. A single strain was resistant to three of the five quinolones tested, but resistance to all the quinolones could be induced easily in vitro by exposure to increasing subinhibitory concentrations of norfloxacin in broth.     

In Vitro Comparison of Netilmicin, a Semisynthetic Derivative of Sisomicin, and Four Other Aminoglycoside Antibiotics

One hundred isolates of Pseudomonas and Enterobacteriaceae, of which 85 were chosen because of their resistance to gentamicin or amikacin, were tested for susceptibility to netilmicin (SCH 20569), a new semisynthetic derivative of sisomicin, and to four other aminoglycosides. Tests were performed in Mueller-Hinton agar and, with 43 of these isolates, also in Mueller-Hinton broth. Most isolates of Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Serratia that were gentamicin resistant proved to be susceptible to netilmicin and amikacin. Tests of representative isolates of this group showed that they owed their resistance to the production of aminoglycoside-adenylylating enzymes. Four isolates of Serratia, detected by their resistance to amikacin, were also highly resistant to netilmicin but were susceptible to gentamicin. These isolates produced aminoglycoside-acetylating enzymes. Gentamicin-resistant Proteus and Providencia were, in general, highly resistant to netilmicin but were susceptible to amikacin. These isolates also produced aminoglycoside-acetylating enzymes. Most gentamicin-resistant strains of Pseudomonas were resistant to netilmicin, either by enzymatic aminoglycoside modification or by other undefined mechanisms. Thus, like amikacin, netilmicin extends the aminoglycoside susceptibility pattern of Enterobacteriaceae to include gentamicin-resistant isolates that produce aminoglycoside-adenylylating enzymes. It is ineffective against strains, some of them susceptible to amikacin, gentamicin, or tobramycin, that produce aminoglycoside-acetylating enzymes.     

Different aminoglycoside-resistant phenotypes in a rabbit Staphylococcus aureus endocarditis infection model

The impact of different types of enzymatic resistance on the in vivo antibacterial activity of aminoglycosides (amikacin, gentamicin, and netilmicin) was studied in the rabbit endocarditis model with four strains of Staphylococcus aureus. Animals were treated in a manner simulating the administration of a single daily human dose. Amikacin had no effect on the three kanamycin-resistant strains despite apparent susceptibility in the disk diffusion test. Gentamicin appears to be the preferable aminoglycoside for treatment of staphylococcal infections.     

Netilmicin: in-vitro activity compared with that of other aminoglycosides against Serratia marcescens

The activity of netilmicin, a semisynthetic aminoglycoside, was compared with that of gentamicin, tobramycin, and amikacin against 100 clinical isolates of Serratia marcescens. Minimum inhibitory concentrations (MIC) were determined by an agar dilution procedure. Defining amikacin resistance as an MIC of greater than 16 mg/l, and netilmicin, gentamicin and tobramycin resistance as an MIC greater than 4 mg/l, 1% were resistant to amikacin, 3% to netilmicin, 8% to tobramycin, and 43% to gentamicin. The majority of isolates that were resistant to both gentamicin and tobramycin were sensitive to netilmicin. These results indicate that the activity of netilmicin against Ser. marcescens is closely comparable to that of amikacin.     

Aminoglycoside resistance among Pseudomonas aeruginosa isolates with an unusual disk diffusion antibiogram.

In recent years, a number of clinical microbiology laboratories have isolated Pseudomonas aeruginosa with the unusual aminoglycoside disk diffusion result of resistance to both amikacin and gentamicin but susceptibility to tobramycin (ArGrTs). A total of 39 isolates of P. aeruginosa reported to have this resistance pattern were retested by the standard National Committee for Clinical Laboratory Standards disk diffusion procedure; 30 strains (77%) were confirmed to be ArGrTs. These 30 isolates were further examined for susceptibility to those aminoglycosides by agar dilution and broth micro- and macrodilution methods. Only 27, 27, and 23% of the isolates appeared to be ArGrTs by agar, broth microdilution, and broth macrodilution testing, respectively. Most of the remaining isolates were resistant to all three aminoglycosides when tested by broth dilution and resistant only to gentamicin when tested by agar dilution. The percentages of strains resistant to any particular aminoglycoside by agar dilution, broth microdilution, and broth macrodilution, respectively, were 43, 80, and 70 for amikacin, 97, 93, and 100 for gentamicin, 100, 100, and 100 for netilmicin, 30, 87, and 93 for sisomicin, and 13, 57, and 50 for tobramycin. These results indicate that strains showing the unusual aminoglycoside antibiogram are less susceptible to aminoglycosides in general and should probably be considered borderline resistant to all aminoglycosides. The efficacy of aminoglycosides in the treatment of infections produced by these strains is unknown.     

Comparative cochlear toxicities of streptomycin,gentamicin, amikacin and netilmicin in guinea-pigs

All the aminoglycoside antibiotics now in clinical use are ototoxic. This study was designed to compare the toxic effects of four aminoglycoside antibiotics, streptomycin, gentamicin, amikacin and netilmicin, administered to guinea-pigs systemically (at respective doses of 125 mg/kg, 50 mg/kg, 150 mg/kg or 37.5 mg/kg, twice daily for 1 week) or topically via the transtympanic route (0.25 ml/kg in 4% saline, twice daily for 1 week). Chosen doses were 10-20 times higher than the recommended human dosage. Cochlear damage was observed in all animals that were given systemic and local aminoglycosides. The severity of the cochlear damage was in the order gentamicin, amikacin, streptomycin, netilmicin, with gentamicin being the most toxic. No statistically significant difference between the severity of cochlear damage resulting from the systemic and topical applications was detected.     

Phenotypic and genotypic aminoglycoside resistance in blood culture isolates of coagulase-negative staphylococci from a single neonatal intensive care unit, 1989-2000

OBJECTIVES: To investigate the prevalence of aminoglycoside resistance and genes encoding aminoglycoside-modifying enzymes (AME) in blood culture isolates of coagulase-negative staphylococci (CoNS) from neonates. MATERIALS AND METHODS: A total of 180 isolates from 148 patients collected in a single neonatal unit over a 12 year period were examined for susceptibility to gentamicin, tobramycin, netilmicin, amikacin and arbekacin by Etest and/or disc diffusion. AME genes were detected by PCR. RESULTS: The overall non-susceptibility rates to gentamicin, tobramycin, netilmicin, amikacin and arbekacin were 66%, 68%, 52%, 38% and 1%, respectively. Gentamicin non-susceptibility rates were 4% and 91% in methicillin-susceptible and -resistant isolates, respectively. aac(6')-Ie-aph(2')-Ia, aph(3')-IIIa and/or ant(4')-Ia were encountered in 125 (69%), 1 (0.5%) and 30 (16.6%) isolates, respectively. Forty-six (26%) isolates negative for AME genes were susceptible to all aminoglycosides. In contrast, 115 (92%), 91 (73%) and 66 (53%) of aac(6')-Ie-aph(2')-Ia positive isolates were non-susceptible to gentamicin, netilmicin and amikacin, respectively. Only one isolate showed arbekacin resistance. However, aac(6')-Ie-aph(2')-Ia positive isolates and isolates with gentamicin MIC > or =128 mg/L displayed a significant reduction in arbekacin inhibition zones. CONCLUSIONS: A high prevalence of aminoglycoside resistance was detected and associated with methicillin resistance. Discrepancies between phenotypic and genetic detection of aminoglycoside resistance were discerned. Gentamicin was the preferred substrate for phenotypic detection of aac(6')-Ie-aph(2')-Ia. Arbekacin showed favourable antibacterial activity even in aac(6')-Ie-aph(2')-Ia-positive isolates. We suggest including arbekacin in future clinical trials of empirical treatment of late onset neonatal sepsis.