Genetic changes associated with tigecycline resistance in Staphylococcus aureus in vitro-selected mutants belonging to different lineages

Tigecycline (TGC) resistance remains rare in Staphylococcus aureus worldwide. In this study, 12 TGC-resistant S. aureus mutants (TRSAm) were obtained displaying an increase in efflux activity. The isolates belonged to seven different genetic lineages, with a predominance of clonal complex 5 (CC5). Diverse genetic changes in mepA and mepR genes were found producing alterations in the amino acid sequences of the corresponding proteins (MepA and MepR, respectively). The most frequent amino acid change in MepA was Glu287Gly. All of the TRSAm exhibited different single nucleotide polymorphisms (SNPs) or insertions/deletions (InDels) in mepR causing premature stop codons or amino acid changes in MepR. Expression of mepA was significantly increased in TRSAm with different mutations in mepA and mepR. Of the 12 TRSAm, 6 also harboured mutations in rpsJ that resulted in amino acid changes in the S10 ribosomal protein, with Lys57 being the most frequently mutated site. Our findings demonstrate that these acquired mechanisms of TGC resistance are not restricted to a single type of genotypic background and that different lineages might have the same plasticity to develop TGC resistance. The impact of TGC selective pressure assessed by whole-genome sequencing in four selected strain pairs revealed mutations in other singular genes and IS256 mobilisation.     

Detection of point mutations associated with antibiotic resistance in Pseudomonas aeruginosa

Excessive use of broad-spectrum antibiotics in hospitals has led to the emergence of highly resistant strains of Pseudomonas aeruginosa. To reduce the selection pressure for resistance, it is important to determine the antibiotic susceptibility pattern of bacteria so that hospital patients can be treated with more narrow-spectrum and target-specific antibiotics. This study describes the development of a technique for detecting point muations in the fluoroquinolone resistance-determining region of the gyrA and parC genes as well as the efflux regulatory genes mexR, mexZ and mexOZ that are associated with fluoroquinolone and aminoglycoside resistance. The assay is based on a short DNA sequencing method using multiplex-fast polymerase chain reaction (PCR) and Pyrosequencing™ for amplification and sequencing of the selected genes. Fifty-nine clinical isolates of P. aeruginosa were examined for mutations in the abovementioned genes. Mutations related to antibiotic resistance were detected in codons 83 and 87 of gyrA and codon 126 of the mexR regulatory gene. Results of this study suggest Pyrosequencing™ as a substitute for traditional methods as it provides a rapid and reliable technique for determining the antibiotic resistance pattern of a given bacterial strain in <1 h.     

Characterisation of integrons containing the plasmid-mediated quinolone resistance gene qnrA1 in Klebsiella pneumoniae

The aim of this study was to determine the structural relationships of qnrA1 and other resistance genes in four integrons contained in four clinical isolates of Klebsiella pneumoniae. In the four integrons, the sequences surrounding qnrA1 were similar to those described for pMG252 (accession no. AY070235). The four integrons carried a class 1 integrase gene belonging to the complex class 1 integron. Three of the strains contained an identical integron coding for resistance to β-lactams, aminoglycosides, chloramphenicol and trimethoprim. The fourth strain contained a different integron coding for resistance to β-lactams, aminoglycosides and chloramphenicol. Downstream of the last integron, copies of IS6100 and IS26 were present. We describe two new and different integrons containing qnrA1. These integrons code for resistance to different groups of antimicrobial agents from K. pneumoniae clinical strains isolated in the USA.     

Investigation of the prevalence of tetQ, tetX and tetX1 genes in Bacteroides strains with elevated tigecycline minimum inhibitory concentrations

In this study, the antibiotic susceptibilities to tigecycline and tetracycline of 35 selected Bacteroides fragilis group strains were determined by Etest, and the presence of tetQ, tetX, tetX1 and ermF genes was investigated by polymerase chain reaction (PCR). tetQ was detected in all 12 B. fragilis group isolates (100%) exhibiting elevated tigecycline minimum inhibitory concentrations (MICs) (≥8 μg/mL) as well as the 8 strains (100%) with a tigecycline MIC of 4 μg/mL, whilst tetX and tetX1 were present in 15% and 75% of these strains, respectively. All of these strains were fully resistant to tetracycline (MIC ≥ 16 μg/mL). On the other hand, amongst the group of strains with tigecycline MICs < 4 μg/mL (15 isolates), tetQ, tetX and tetX1 were found less frequently (73.3%, 13.3% and 46.7%, respectively). All but two strains harbouring the tetQ gene in this group were non-susceptible to tetracycline, with a MIC > 4 μg/mL. These data suggest that in most cases tigecycline overcomes the tetracycline resistance mechanisms frequently observed in Bacteroides strains. However, the presence of tetX and tetX1 genes in some of the strains exhibiting elevated MICs for tigecycline draws attention to the possible development and spread of resistance to this antibiotic agent amongst Bacteroides strains. The common occurrence of ermF, tetX, tetX1 and tetQ genes together predicted the presence of the CTnDOT-like Bacteroides conjugative transposon in this collection of Bacteroides strains.     

Resistance mechanism ofAcinetobacter spp. strains resistant to DW-116, a new quinolone

DW-116 is a new fluoroquinolone antimicrobial agent with a broad spectrum. In order to elucidate the resistance mechanism to DW-116 inAcinetobacter spp. bacteria, total chromosomal DNA was isolated from 10 strains ofAcinetobacter spp. resistant to DW-116. Quinolone resistance determinant region (QRDR) of DNA gyrase gene was amplified by PCR. The 345 bp nucleotide fragment yielded was inserted into pKF 3 which was used as the vector. Comparisons of the DNA sequences of 8 strains with that of the wild type strain revealed a Ser-83 to Leu mutation in mutants and all ten strains contained one silent mutation(T→G) in QRDR. FromAcinetobacter MB4-8 strain, DNA gyrase was isolated and purified, through novobiocin-sepharose, heparin-sepharose affinity column chromatography. The enzyme was composed of two subunits and the molecular mass of subunits A and B were 75.6 and 51.9 kDa, respectively. The supercoiling activity of the reconstituted DNA gyrase composed of subunit A fromAcinetobacter MB4-8 and subunit B fromE. coli was not inhibited by 128 μg/ml of ciprofloxacin. It might be said that one of the resistance mechanisms to DW-116 inAcinetobacter MB4-8 was subunit A alteration of DNA gyrase.     

2015-2020年新郑市人民医院妇科肿瘤术后患者医院感染的病原菌分布和耐药情况分析

目的 探讨新郑市人民医院妇科肿瘤术后发生医院感染的病原菌情况.方法 选取2015年9月—2020年9月在新郑市人民医院接受妇科肿瘤手术的120例患者的治疗资料进行分析.结果 妇科肿瘤术120例患者总计检出病原菌208株,革兰阴性菌134株(64.42％),革兰阳性菌60株(28.85％),真菌14株(6.73％).大肠...     

2017—2020年克拉玛依市中心医院抗菌药物使用强度与分离菌耐药性变化情况

目的 分析克拉玛依市中心医院2017—2020年住院患者常见分离菌分布及耐药率的变迁情况,为指导抗菌药物临床合理应用提供依据。方法 收集2017—2020年克拉玛依市中心医院住院患者抗菌药物使用情况及分离菌,分析主要分离菌对常见抗菌药物的耐药率变化趋势。结果 2017—2019克拉玛依市中心医院抗菌药物使用率和使用强度呈下降趋势,4年共有分离菌12 135株,其中革兰阳性菌2 567株,占21.15%;革兰阴性菌6 310株,占52.00%;真菌3 258株,占26.85%。居前5位的分离菌分别是白色假丝酵母菌（19.59%）、大肠埃希菌（16.84%）、肺炎克雷伯菌（13.33%）、鲍曼不动杆菌（8.71%）和铜绿假单胞菌（7.94%）。主要分离菌对常用抗菌药物耐药率总体呈下降趋势,肠杆菌科细菌对临床常用抗菌药物耐药性下降最明显。结论 克拉玛依市中心医院分离菌逐年增加,耐药率有下降趋势,抗菌药物临床应用基本合理,但需完善真菌检测能力。     

In vitro activity of ABT-773, telithromycin and eight other antimicrobials against erythromycin-resistant Streptococcus pneumoniae respiratory isolates of children

The activity of the ketolide ABT-773 against 180 erythromycin-resistant Streptococcus pneumoniae obtained from children was compared with telithromycin, azithromycin, clarithromyin, roxithromycin, clindamycin, penicillin, levofloxacin and gatifloxacin. Ketolide MICs were all ≤1 mg/l, with ABT-773 being the most potent of all drugs tested. MIC₉₀s for macrolides and azithromycin in mefE+ isolates were 16–32 compared with >128 mg/l for ermB+ isolates. ABT-773 and telithromycin MIC₉₀s for mefE+ isolates were 0.125 and 0.5, compared with 0.032 and 0.016 mg/l for ermB+ isolates and 0.5 and 1 mg/l, respectively, for isolates containing both genes. Clindamycin was active against mefE+ but not ermB+ isolates. 155 isolates were resistant to penicillin. All fluoroquinolone MICs were <1 mg/l. Further studies of ketolides for treatment of paediatric S. pneumoniae infections are warranted.     

2020—2022年清镇市第一人民医院妊娠期妇女尿路感染病原菌构成特点及耐药性分析

目的 探讨清镇市第一人民医院妊娠期妇女尿路感染病原菌的构成特点及耐药性,为临床治疗提供参考。方法 收集2020年1月—2022年12月清镇市第一人民医院疑为尿路感染妊娠期妇女清洁中段尿标本,使用法国梅里埃VITEK-2Compact或VITEK MS质谱仪进行病原菌鉴定和抗生素最低抑菌浓度（MIC）检测,根据美国临床试验室标准化研究所（CLSI）的标准判断药敏结果,采用WHONET 5.6和SPSS 20.0软件进行数据统计。结果 共检出384株病原菌,其中革兰阴性菌占84.9%(326株);革兰阳性菌占13.3%(51株),念珠菌占1.8%(7株),病原菌以大肠埃希菌（297株,占77.3%）和无乳链球菌（30株,占7.8%）最为常见。大肠埃希菌对氨苄西林、氨苄西林/舒巴坦、复方磺胺甲噁唑、头孢唑啉、环丙沙星和左氧氟沙星的耐药率高于70.0%,对呋喃妥因、哌拉西林/他唑巴坦、阿米卡星和头孢替坦的耐药率低于10.0%,多重耐药菌株占42.1%;无乳链球菌对四环素和克林霉素的耐药率高于65.0%,对青霉素、氨苄西林、喹努普汀/达福普汀、替加环素、利奈唑胺和万古霉素的耐药率为0。结论 妊娠...     

2018—2020年郑州市第七人民医院血流感染分离菌的分布及耐药性分析

目的 了解血流感染分离菌的分布及耐药特征,为临床防治血流感染提供指导和依据。方法 收集2018年1月—2020年12月郑州市第七人民医院血培养分离的非重复菌株,采用WHONET5.6软件统计菌株的分布及耐药特征。结果 共分离546株菌株,革兰阴性菌302株（55.31%）,革兰阳性菌220株（40.29%）,真菌24株（4.40%）。前6位分离菌依次为凝固酶阴性葡萄球菌（CNS,23.44%）、大肠埃希菌（18.68%）、肺炎克雷伯菌（14.84%）、金黄色葡萄球菌（6.04%）、鲍曼不动杆菌（4.21%）和铜绿假单胞菌（3.85%）。大肠埃希菌对碳青霉烯类最敏感,肺炎克雷菌碳对美罗培南和亚胺培南的耐药率分别为30.86%和35.80%,鲍曼不动杆菌耐药较严重,耐甲氧西林凝固酶阴性葡萄球菌（MRCNS）和耐甲氧西林金黄色葡萄球菌（MRSA）的检出率分别为72.66%、42.42%,未发现利奈唑胺和万古霉素耐药的葡萄球菌。结论 革兰阴性菌是医院血流感染的主要致病菌,细菌耐药情况复杂,临床要根据药敏结果合理选择抗菌药物。     

2012—2020年泰达国际心血管病医院心血管疾病患者血流感染病原菌分布和耐药性分析

目的 分析泰达国际心血管病医院心血管疾病患者发生血流感染的病原菌分布及耐药特征,为临床合理应用抗菌药物提供依据.方法 对2012年1月—2020年12月泰达国际心血管病医院血流感染病原菌的分布及耐药性进行回顾性分析.结果 共检出病原菌234株,其中革兰阴性菌133株,构成比为56.8％,主要为大肠埃希菌、肺炎克雷伯菌和...     

2018—2019年西安交通大学第二附属医院鲍曼不动杆菌的分布及耐药性分析

目的 分析西安交通大学第二附属医院鲍曼不动杆菌的临床分布及耐药性,为临床医师选择合理的抗感染治疗方案提供参考依据。方法 以2018年1月-2019年12月西安交通大学第二附属医院住院的患者为研究对象,按照美国临床实验室标准化委员会（CLSI）推荐的方法进行鲍曼不动杆菌的初步筛选,用梅里埃VITEK 2 Compact全自动细菌鉴定及药敏分析系统进行细菌鉴定和药敏实验,用Excel进行数据统计分析。结果 2018-2019年本院住院患者中共分离出935株鲍曼不动杆菌,主要分布于急诊科,共181株;主要来源于痰液标本,共676株。感染人群主要为14岁以上的中青年及老年患者。药敏结果显示鲍曼不动杆菌对替卡西林/克拉维酸、多西环素、哌拉西林/他唑巴坦具有较高的耐药性,耐药率依次为87.43%、75.96%、64.98%;鲍曼不动杆菌对黏菌素、阿米卡星和替加环素具有良好的敏感性,敏感率依次为99.61%、85.02%、73.56%。结论 本院临床上鲍曼不动杆菌感染的高发人群为14岁以上的中青年及老年患者,鲍曼不动杆菌对多种抗生素都有很强的耐药性,应加强病原菌培养及耐药性监测,指导临床医师合理使用抗生素。     

In vitro activity of eugenol, an active component from Ocimum sanctum, against multiresistant and susceptible strains of Neisseria gonorrhoeae

In view of the widespread emergence of resistant isolates, an attempt was made to isolate and characterise the component(s) of Ocimum sanctum with activity against Neisseria gonorrhoeae. Bioassay-guided purification of the hexane extract of leaves of O. sanctum was carried out, which yielded H12c as the active compound. H12c was characterised and was determined to be eugenol, with a minimum inhibitory concentration of 85-256 mg/L. The antigonorrhoeal efficacy of H12c was better against multiresistant strains. The 50% lethal dose (LD50) of H12c was found to be 2g/kg body weight in rats. In view of its efficacy and lower toxicity, eugenol may be a potentially suitable molecule to be developed clinically in response to emerging resistant isolates of N. gonorrhoeae.     

Mutations in dihydropteroate synthase gene of Pneumocystis carinii in HIV patients with Pneumocystis carinii pneumonia

The purpose of this study was to determine whether dihydropteroate synthase gene (DHPS) mutations were associated with the failure of sulpha/sulphone drugs used as prophylaxis agents in HIV infected patients. Results suggested that DHPS mutations were significantly associated with failure of anti-Pneumocystis carinii sulphone prophylaxis (P=0.031). An increasing number of mutant P. carinii strains have been isolated from patients no longer having prophylaxis. There was no statistically significant difference in severity or outcome of the pneumonia caused by wild-type or mutant DHPS. Moreover, two of the three patients with mutant P. carinii pneumonia (PCP) were successfully treated with sulpha drugs. We think that P. carinii drug-resistance could be an emerging problem for immunocompromised patients including those with HIV infection.     

2018-2022年深圳市妇幼保健院分离真菌的分布及耐药情况分析

目的 调查分析南方医科大学附属深圳妇幼保健院分离真菌的分布特点和药物敏感性情况,为妇幼真菌感染疾病的临床诊治、耐药性监测和流行病学研究提供参考。方法 回顾分析南方医科大学附属深圳妇幼保健院2018年1月-2022年12月标本采集、真菌鉴定和抗真菌药敏试验的结果数据。结果 共分离真菌3 350株,前2位分别为白色念珠菌1 542株、光滑念珠菌223株。阳性标本以阴道分泌物/宫颈分泌物为主。妇科和产科分离到的真菌最多。白色念珠菌对伊曲康唑、伏立康唑的5年耐药率分别为9.58%、4.12%,对两性霉素B和5-氟胞嘧啶的5年敏感率分别为99.79%、98.01%,对氟康唑的历年敏感率有逐渐升高的态势。光滑念珠菌、近平滑念珠菌和热带念珠菌对两性霉素B及5-氟胞嘧啶的敏感率均为100.00%。克柔念珠菌对两性霉素B和伏立康唑100.00%敏感。结论 南方医科大学附属深圳妇幼保健院分离真菌以念珠菌属为主,其中白色念珠菌最多。阴道分泌物/宫颈分泌物是主要真菌阳性分离标本。白色念珠菌对两性霉素B的耐药率最低、敏感率最高,对伊曲康唑的耐药率最高、敏感率最低。光滑念珠菌、近平滑念珠菌、热带念珠菌和克柔念珠菌对两性霉素B和5-氟胞嘧啶均无耐药性。光滑念珠菌对伊曲康唑耐药率最高、敏感率最低。     

2014—2018年解放军第三一六医院妊娠期女性人型支原体和解脲支原体感染状况及耐药性分析

目的 分析2014-2018年解放军第三一六医院妊娠期女性人型支原体和解脲支原体感染状况及耐药性。方法 采用回顾性分析的方法,对2014年1月-2018年12月解放军三一六医院的1 171例妊娠期女性泌尿生殖道支原体感染状况及耐药情况进行分析。结果 1 171例妊娠期女性中,644例感染了解脲支原体和/或人型支原体,其中1人感染了人型支原体,590例感染了解脲支原体,53例共同感染了两种支原体。解脲支原体在17~20岁年龄段感染率最高,解脲支原体和人型支原体双阳性在41~50年龄段感染率最高。解脲支原体和/或人型支原体对喹诺酮类抗生素、阿奇霉素和红霉素的敏感性较低,对交沙霉素、克拉霉素、美满霉素、强力霉素和四环素的敏感性较高。结论 妊娠期女性泌尿生殖道支原体的感染率高,耐药严重,一定要根据培养鉴定和药敏试验选用敏感抗生素进行治疗。     

2015—2019年连云港市第二人民医院感染真菌患者菌株分布及耐药性分析

目的 分析2015—2019年连云港市第二人民医院真菌培养阳性标本的病原菌分布情况和耐药状况。方法 收集2015年1月—2019年12月在连云港市第二人民医院所有的真菌培养和药敏试验阳性的标本共663例,应用DL-96Ⅱ细菌测定系统的体外诊断试剂DL-96FOUNGUS对样本进行真菌鉴定,以5种常见抗真菌药物为例,采用MIC法开展对样本中已鉴定真菌的药物敏感性试验,并应用WHONET 5.6软件进行对于该试验结果的统计学分析。结果 2015—2019年连云港市第二人民医院共分离出真菌663株。按照菌种类型分类,可得到如下比例：白色假丝酵母菌占49.9%（331/663）、热带假丝酵母菌占15.2%（101/663）、都柏林假丝酵母菌占8.3%（55/663）、光滑假丝酵母菌14.9%（99/663）、其他假丝酵母菌占11.6%（77/663）。白色假丝酵母菌对伏立康唑、氟康唑、伊曲康唑3种抗菌药物仍具有耐药性;热带假丝酵母菌对氟胞嘧啶、两性霉素高度敏感,对伏立康唑、氟康唑、伊曲康唑表现为耐药;光滑假丝酵母菌对氟胞嘧啶和两性霉素B的敏感性最高。结论 白色假丝酵母菌、热带假丝酵母菌、光滑假丝酵母菌是真菌感染的主要常见致病菌,以热带假丝酵母菌为主的多种假丝酵母菌对于氟康唑、伊曲康唑等临床常用抗菌药物耐药性日渐增长。     

2017—2021年肇庆市第一人民医院恶性肿瘤化疗后患者血流感染病原菌分布及耐药性分析

目的 分析肇庆市第一人民医院2017年1月-2021年12月肿瘤科和血液肿瘤科血培养的病原菌分布和药敏情况,以了解临床血流感染状况,为临床合理使用抗菌药物提供依据。方法 收集2017年1月1日-2021年12月31日肇庆市第一人民医院肿瘤科和血液肿瘤科临床送检血培养阳性标本分离出的210株病原菌资料并对患者临床资料进行分析。结果 210株血培养阳性菌株中,血液肿瘤92株,实体肿瘤118株。革兰阴性杆菌136株(占64.76%),革兰阳性球菌66株(占31.43%),真菌8株(占3.81%)。前5位的致病细菌分别为大肠埃希菌(24.29%)、凝固酶阴性葡萄球菌(15.24%)、肺炎克雷伯菌(12.86%)、铜绿假单胞菌(12.38%)、金黄色葡萄球菌(9.05%)。革兰阴性杆菌中大肠埃希菌和肺炎克雷伯菌产超广谱β内酰胺酶(ESBL)菌株的检出率分别为37.2%、19%。其中铜绿假单胞菌对亚胺培南的耐药率为15%,对美罗培南的耐药率为15.8%。结论 肇庆市第一人民医院恶性肿瘤患者化疗后合并血流感染病原菌种类分布较广,以革兰阴性杆菌为主,耐药情况较严峻。临床上对怀疑有革兰阳性球菌血液感染患者可经验性选择万古霉素、利奈唑胺或替加环素抗感染治疗。     

2013—2015年西安市胸科医院结核分枝杆菌的耐药性分析

目的了解西安市胸科医院结核分枝杆菌的耐药情况,为临床医生调整治疗方案和流行病学调查提供依据。方法选取2013年1月—2015年11月西安市胸科医院结核分枝杆菌感染的住院患者392例,对分离出的病原菌的耐药性进行分析。结果菌株来源于132例初治患者和260例复治患者,其中男性患者多于女性患者,年龄段主要集中在36~55岁。初治耐药率为22.5%,获得性耐药率为41.2%;链霉素的耐药率最高,为23.7%,乙胺丁醇的耐药率最低,为13.3%;单一耐药菌株有60株,耐药率为15.4%;多耐药菌株有37株,耐药率为9.4%;耐多药的菌株有52株,耐药率为13.2%;有27株全耐药,耐药率为6.9%。结论西安市胸科医院结核分枝杆菌的耐药状况仍处较高水平,应做好结核分枝杆菌的培养和药敏试验,并根据药敏实验结果合理制定或调整治疗方案。     

Genetical relationship between resistance to insecticides and procarcinogens in two Drosophila populations

Two Drosophila populations, one resistant and the other susceptible to several insecticides, were examined for response to several alkaryltriazenes (2,4,6-Cl₃-PDMT; 3-PyDMT; 3-PyDET) and to DMN, DEN and AM. Hikone R (HR) males developed relative resistance to both mutation induction and cell killing by the triazenes, whereas Berlin K (BK) males showed increased tolerance to DMN, DEN, and AM. When F₁ hybrid males from the two strains were treated with 2,4,6-Cl₃-PDMT, the yield of recessive lethal mutations in the heterozygotes was nearly half of that found in homozygotes from the susceptible strain Berlin K. These findings indicate that in Drosophila metabolism of procarcinogens is controlled by multiple-gene systems located on several chromosomes. An extremely divergent response of the two genotypes was found following treatment with 3-PyDET; this triazene acts as a potent mutagen in BK males but is hardly mutagenic when tested in strain HR.Abbreviations AM azoxymethane - DEN N-nitrosodiethylamine - DMN N-nitrosodimethylamine - 3-PyDET (3,3-diethyl-1-(3-pyridyl)-triazene) - 3-PyDMT (3,3-dimethyl-1-(3-pyridyl)-triazene) - 2,4,6-Cl₃-PDMT (1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene) - 3-PyODMT 3,3-dimethyl-1-N-oxide-(3-pyridyl)-triazene Part of this work was presented at a Conference on In Vitro Metabolic Activation in Mutagenesis Testing (cf. Vogel, 1976).