Anti-staphylococcal activity of ent-kaurane-type diterpenoids from Croton tonkinensis

Ent-kaurane-type diterpenpoids 1–11, isolated from the dried leaves of the endemic Vietnamese medicinal plant Croton tonkinensis Gagnep. (Euphorbiaceae), were evaluated for inhibitory activity against Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) strains. The most active diterpenoids, 2, 3, and 8, exhibited minimum inhibitory concentrations (MICs) of 32, 500, and 125 g/ml, respectively, against MRSA strains.     

Multiple pathways towards reduced membrane potential and concomitant reduction in aminoglycoside susceptibility in Staphylococcus aureus

Staphylococcus aureus is responsible for life-threatening and difficult-to-treat infections worldwide and antimicrobial resistance is an increasing concern. Whilst acquired resistance has been widely studied, little is known of the contributions from chromosomal determinants that upon inactivation may reduce the susceptibility of S. aureus to antibiotics. The aim of this study was to identify genetic determinants that upon inactivation reduce aminoglycoside susceptibility in S. aureus. The Nebraska Transposon Mutant Library of 1920 single-gene inactivations in S. aureus strain JE2 was screened for reduced susceptibility to gentamicin. Nine mutants were confirmed by Etest to display between 2- and 16-fold reduced susceptibility to this antibiotic. All of the identified genes were associated with the electron transport chain and energy metabolism. Four mutant strains (menD, hemB, aroC and SAUSA300_0355) conferred the largest decrease in gentamicin susceptibility and three exhibited a small colony variant phenotype, whereas the remaining mutants (qoxA, qoxB, qoxC, ndh and hemX) displayed colony morphology similar to the wild-type. All of the mutants, except hemX, displayed reduced membrane potential suggesting that reduced uptake of gentamicin is the predominant mechanism leading to reduced susceptibility. The results of this study demonstrate that S. aureus possesses multiple genes that upon inactivation by mutagenesis reduce the membrane potential and thereby reduce the lethal activity of gentamicin.     

丁香酚对压疮致病菌金黄色葡萄球菌及其耐药菌的抑菌作用及机制

目的 明确丁香酚对压疮致病菌金黄色葡萄球菌Staphylococcus aureus的体外抑菌作用及机制。方法 采用微量肉汤稀释法和和生长曲线确定丁香酚对金黄色葡萄球菌的抑菌活性;通过碱性磷酸酶（AKP）活性、细菌核酸蛋白泄漏的检测,细菌超微结构的扫描和透射电镜观察以及菌体对碘化丙啶（PI）和N-菲酰-次巯基-L-丙氨酸（NPN）的摄取来探讨丁香酚处理后金黄色葡萄球菌细胞膜的通透性和完整性;以结晶紫染色法和实时荧光定量PCR法研究丁香酚对菌体生物被膜（BF）生成、成熟以及菌体黏附、侵袭相关毒力因子表达水平的影响。结果 丁香酚对金黄色葡萄球菌标准菌和耐甲氧西林金葡菌（MRSA）的最低抑菌浓度（MIC）分别为0.25、0.125 mg/mL。丁香酚处理后可以提高细菌培养液中核酸、蛋白浓度及AKP的活性;菌体出现皱缩和破裂,菌体内膜和外膜中分别出现PI和NPN荧光,菌体结构破坏和荧光强度与丁香酚浓度呈正相关。丁香酚能够抑制金黄色葡萄球菌菌株BF的生成,且对成熟BF具有明显清除作用,显著降低BF生成相关基因agr A、sar A、cid A和icaA及黏附因子clf A、clf B、fnb A...     

黄芩苷消除鲍曼不动杆菌耐药质粒的实验研究

目的探讨黄芩苷能否消除鲍曼不动杆菌质粒,并影响抗菌药物对细菌的最低抑菌浓度(MIC)。方法测定黄芩苷处理的鲍曼不动杆菌生长曲线。16株庆大霉素和环丙沙星双重耐药的鲍曼不动杆菌,经黄芩苷作用20 h,分别在处理前和处理后应用碱裂解法检测质粒,琼脂稀释法测定抗菌药物MIC。结果黄芩苷能抑制鲍曼不动杆菌生长。16株鲍曼不动杆菌耐药株均携带质粒,经1 mg.mL 1黄芩苷作用后,质粒消除率为37.5%(6/16)。6株经黄芩苷消除质粒的细菌,庆大霉素中度水平或低水平耐药株的MIC值均下降至敏感水平;环丙沙星低水平耐药株的MIC值下降至敏感水平,部分环丙沙星中度水平耐药株的MIC值下降但高于耐药水平。结论黄芩苷能够消除鲍曼不动杆菌低水平耐药株携带的质粒,恢复菌株对庆大霉素和环丙沙星的敏感性,可用于鲍曼不动杆菌低水平耐药株感染辅助治疗。     

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.     

Antibiotic resistance in Staphylococcus aureus and its relevance in therapy

Staphylococcus aureus is a major cause of infections. Only ～ 20% of the strains remain sensitive to penicillin. β-lactamase stable penicillins such as flucloxacillin form the mainstay of treatment of staphylococcal infection. Meticillin-resistant S. aureus (MRSA) are resistant to all β-lactam antibiotics. Glycopeptide antibiotics are effective against most MRSA strains but, in the last few years, isolates of MRSA that have reduced susceptibility to glycopeptides (glycopeptide-intermediate S. aureus) have been isolated. Some strains exhibit frank resistance to glycopeptides (vancomycin-resistant S. aureus). Infections due to these strains are difficult to treat. This review summarises the therapeutic options for MRSA, glycopeptide-intermediate S. aureus and vancomycin-resistant S. aureus. Novel therapeutic strategies such as immunotherapy and vaccines are also discussed.     

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...     

Antimicrobial therapy of Staphylococcus aureus bloodstream infection

Staphylococcus aureus bloodstream infection (BSI) contributes significantly to the morbidity and mortality of in-patients. The optimal therapy for methicillin-susceptible S. aureus BSI consists of penicillins. The efficacy of these drugs is well documented from several published data and supported from a long clinical experience. Methicillin-resistant S. aureus (MRSA) strains are responsible for the majority of nosocomial BSI and are recovered with increasing frequency at hospital admission. Although glycopeptides still represent the drugs of choice, there are several concerns on the treatment of MRSA BSI: reports of clinical failure with vancomycin treatment, regardless of the in vitro susceptibility; increasing reports of MRSA strains with reduced vancomycin susceptibility; difficulty in therapeutic dosage monitoring of teicoplanin; lack of evidence on the efficacy of combination therapy. Recently, new drugs have been introduced in the therapeutic arsenal for MRSA infections, but their clinical use is not yet clearly established for BSI. The review summarises evidence on present therapeutic options for the treatment of S. aureus BSI.     

Melittin Tryptophan Substitution with a Fluorescent Amino Acid Reveals the Structural Basis of Selective Antitumor Effect and Subcellular Localization in Tumor Cells

Melittin is a membrane-active peptide with strong anticancer activity against various cancers. Despite decades of research, the role of the singular Trp in the anticancer activity and selectivity of melittin remains poorly understood. Here, we propose a theranostic solution based on the substitution of Trp19 with a noncanonical fluorescent amino acid (Dap^AMCA). The introduction of Dap^AMCA residue in melittin stabilized the helical structure of the peptide, as evaluated by circular dichroism spectra and molecular dynamics simulations. In vitro hemolytic and anticancer activity assays revealed that introducing Dap^AMCA residue in melittin changed its mode of action with the cell membrane, resulting in reduced hemolytic toxicity and an improved the selectivity index (SI), with up to a five-fold increase compared to melittin. In vitro fluorescence imaging of Dap^AMCA-labeled melittin (MEL^FL) in cancer cells demonstrated high membrane-penetrating activity, with strong nuclear and nucleolar localization ability. These findings provide implications for novel anticancer therapies based on Trp-substituted designs and nuclear/nucleolar targeted therapy.     

In vitro activity of meropenem/piperacillin/tazobactam triple combination therapy against clinical isolates of Staphylococcus aureus,Staphylococcus epidermidis,Staphylococcus pseudintermedius and vancomycin-resistant Enterococcus spp

ObjectivesTo evaluate the activity of the reported synergistic and collaterally sensitive antibiotic combination, meropenem/piperacillin/tazobactam (ME/PI/TZ), against a panel of methicillin-resistant Staphylococcus aureus (MRSA) and other methicillin-resistant Staphylococcus species; and to investigate the relationship between ME/PI/TZ susceptibility and the genomic background of clinical isolates of MRSA.MethodsME/PI/TZ combination and single drug minimum inhibitory concentrations (MICs) were determined for 207 strains (including 121 MRSA, 4 methicillin-sensitive S. aureus [MSSA], 37 vancomycin-intermediate S. aureus [VISA], 6 ceftaroline non-susceptible MRSA, 29 coagulase-negative staphylococci [CoNS], 5 S. pseudointermedius and 5 vancomycin-resistant Enterococci [VRE]) by broth microdilution. Whole genomes of 168 S. aureus strains were sequenced, assembled, and comparatively analysed.ResultsUSA300-SCCmec type IV isolates, clonal complex 8 (CC8)-MRSA isolates, including some VISA and ceftaroline (CPT)-intermediate strains, and all tested methicillin-resistant S. epidermidis isolates were highly susceptible to ME/PI/TZ. Isolates with elevated MICs (MICs of >16/16/16 mg/L) clustered with the USA100-SCCmec type II strain. Susceptibility of MRSA to ME/PI/TZ was correlated with susceptibility to ME. No obvious cross-resistance to CPT was observed among high-ME/PI/TZ MIC isolates.ConclusionsThe ME/PI/TZ combination is effective against a variety of clinical MRSA isolates, particularly of the USA300 lineage, which is expanding worldwide. ME/PI/TZ is also effective against drug-resistant CoNS and S. pseudintermedius clinical isolates.     

2016—2021年清镇市第一人民医院神经外科患者下呼吸道标本病原菌分布特征及耐药性分析

目的 探讨清镇市第一人民医院神经外科患者下呼吸道标本病原菌构成特点及耐药情况,为临床合理使用抗菌药物治疗提供参考依据。方法 收集2016年1月—2021年12月清镇市第一人民医院神经外科患者送检的合格下呼吸道标本,采用梅里埃VITEK 2-compact分析仪进行细菌鉴定和药物敏感性试验。结果 共检出663株细菌,其中革兰阴性杆菌有556株,占比83.9%;革兰阳性球菌有107株,占比16.1%;常见病原菌为肺炎克雷伯菌（214株,32.3%）、鲍曼不动杆菌（93株,14.0%）、金黄色葡萄球菌（91株,13.7%）、铜绿假单胞菌（80株,12.1%）和大肠埃希菌（61株,9.2%）。耐药性监测结果显示,肺炎克雷伯菌和大肠埃希菌产超广谱β-内酰胺酶（ESBLs）菌株分别占33.1%、60.6%,对碳青霉烯类药物的耐药率为8.9%、1.6%;鲍曼不动杆菌对氨曲南、头孢他啶、氨苄西林/舒巴坦、环丙沙星和头孢吡肟的耐药率超过60.0%,对亚胺培南的耐药率为53.8%;铜绿假单胞菌对庆大霉素、阿米卡星和妥布霉素的耐药率低于15.0%,对亚胺培南的耐药率为45.0%。金黄色葡萄球菌中甲氧西林耐药金黄色葡萄球菌（MRSA）检出率为62.6%,MRSA的耐药率明显高于甲氧西林敏感金黄色葡萄球菌（MSSA）,未检出对替加环素、万古霉素和利奈唑胺耐药的菌株。结论 清镇市第一人民医院神经外科患者下呼吸道感染病原菌以革兰阴性杆菌为主,肺炎克雷伯菌、鲍曼不动杆菌、金黄色葡萄球菌、铜绿假单胞菌和大肠埃希菌是常见的病原菌。病原菌对临床常用抗菌药物耐药严重,多重耐药细菌检出率高,临床用药治疗前应及时采样进行细菌培养和药物敏感性试验,根据药敏试验结果制定合理的治疗方案。     

Catechol-bearing imidazolium and benzimidazolium chlorides as promising antimicrobial agents

Catechol-containing imidazolium (four) and benzimidazolium chlorides (eight) were synthesized to evaluate their antimicrobial properties. All the compounds were fully characterized using ¹H and ¹³C nuclear magnetic resonance, liquid chromatography–mass spectrometry, infrared spectroscopic methods, and elemental analyses. Antimicrobial activities of the compounds were tested against the bacteria Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Enterococcus faecalis, and the fungal strains Candida albicans and Candida glabrata, and promising results were achieved. The two most important benzyl-substituted benzimidazolium chlorides, 3l and 3k , showed comparable activity to vancomycin against MRSA.     

Selection and characterisation of Staphylococcus aureus mutants with reduced susceptibility to the investigational oxazolidinone MRX-I

MRX-I is a new oxazolidinone antimicrobial under development. In this study, the potential for development of resistance to MRX-I in Staphylococcus aureus was investigated and key mutations were characterised. Determination of spontaneous resistance frequency and the mutant selection window (MSW) were performed with meticillin-susceptible S. aureus (MSSA) ATCC 29213, meticillin-resistant S. aureus (MRSA) ATCC 33591 and two clinical MRSA isolates SA 0016 and SA 0017. Selected resistant mutants were sequenced for 23S rRNA as well as genes encoding the ribosomal proteins L3, L4 and L22. Resistance frequencies for the aforementioned strains were <8.25 × 10⁻¹², <6.33 × 10⁻¹², <2.96 × 10⁻¹³ and <4.52 × 10⁻¹³, respectively, and the MSW of MRX-I was 2–4, 1–4, 1–2 and 1–4 mg/L, respectively. After 30 serial passages, MRX-I minimum inhibitory concentrations (MICs) increased up to 8- to 16-fold both against MSSA and MRSA, whilst linezolid MICs increased 128-fold against MSSA and 16- to 32-fold against MRSA. MRX-I resistance mutations were clustered mainly in 23S rRNA and L3 protein regions. The U2504A transversion in 23S rRNA dominated in MRX-I-resistant mutants. No mutations in L4 and L22 proteins were observed. MRX-I exhibits a low potential to develop resistance in S. aureus, with a reduced resistance propensity compared with linezolid.     

2017—2021年南京医科大学附属儿童医院SICU患儿感染常见病原菌分布及耐药性分析

目的 分析南京医科大学附属儿童医院儿外科重症监护病房（SICU）病原菌分布及耐药率,为临床合理选用抗菌药物提供依据。方法 对2017年1月—2021年12月南京市儿童医院SICU患儿送检各类标本所分离的病原菌及其耐药状况进行回顾性分析。结果 11 939例标本共分离出病原菌1 823株,分离率为15.27%。主要分离的革兰阳性菌有金黄色葡萄球菌、凝固酶阴性葡萄球菌;革兰阴性菌有肺炎克雷伯菌、鲍曼不动杆菌、大肠埃希菌、铜绿假单胞菌。金黄色葡萄球菌与凝固酶阴性葡萄球菌的甲氧西林耐药率分别为42.46%、71.68%,未发现耐万古霉素菌株。革兰阴性菌中,有71株肺炎克雷伯菌碳青霉烯耐药菌株,耐药率22.40%。结论 SICU科室应根据患儿自身实际情况合理用药、严格遵循无菌操作规范,监测病原菌分布及耐药状况对抗菌药物的合理选用有重要意义。     

Antimicrobial and antioxidant activities of crude extracts of two Nigerian chewing sticks

In vitro determinations of the antimicrobial and antioxidant activities of ethanol and aqueous extracts of Disthemonanthus benthamianus Baill. (Caesalpiniaceae) and Zanthoxylum zanthoxyloides Lam. (Rutaceae), which are used as chewing sticks in Nigeria, were investigated. The extracts were screened against eight strains of Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, one methicillin-resistant strain of Staphylococcus epidermidis, twelve strains of Pseudomonas aeruginosa, five strains of Candida albicans and four strains of Bacillus cereus. The in vitro antimicrobial assay was performed by using a Mast Multipoint Inoculator based on the principles of an agar dilution technique. The aqueous extracts had no inhibitory effects on any of the tested microorganisms. The ethanol D. benthamianus extract inhibited P. aeruginosa, E. faecalis, and B. cereus with MIC ≤ 2.64?mg mL^?1 and S. aureus and S. epidermidis with MIC ≤ 0.44?mg mL^?1. Z. zanthoxyloides ethanol extract was less effective but noteworthy was the MIC ≤ 2.52?mg mL^?1 against C. albicans and 0.28?mg mL^?1 against some S. aureus strains. D. benthamianus ethanol extract had the best antioxidant activity and Z. zanthoxyloides ethanol extract second best. IC₅₀ for DPPH free radical scavenging of these extracts were 87.76 and 128.28?μg mL^?1/mL, respectively; ascorbic acid equivalents were 2.4 and 9.5?mg mg^?1 and total antioxidant capacities using the FRAP assay were 4068.06?mM Fe⁺⁺ mg^?1 and 624.86?mM Fe⁺⁺ mg^?1, respectively. The ethanol extracts of D. benthamianus and Z. zanthoxyloides showed significant antimicrobial and antioxidant activities which could be beneficial in oral hygiene.     

Molecular analysis and susceptibility patterns of meticillin-resistant Staphylococcus aureus (MRSA) strains circulating in the community in the Ligurian area, a northern region of Italy: emergence of USA300 and EMRSA-15 clones

For many years meticillin-resistant Staphylococcus aureus (MRSA) has been considered a typical nosocomial pathogen. Recently, MRSA has emerged as a frequent cause of infections in the community. A multicentre surveillance study was carried out in the Ligurian area of Italy to evaluate the incidence, molecular nature and susceptibility patterns of MRSA strains circulating among outpatients. The genetic background of MRSA strains was analysed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Determination of antimicrobial susceptibility patterns, staphylococcal cassette chromosome mec (SCCmec) type, accessory gene regulator (agr) group and Panton–Valentine leukocidin (PVL) production was also performed. In total, 12 (6.4%) of 188 S. aureus isolates collected during 2006–2007 were found to be MRSA by phenotypic and genotypic methods. Analysis of isolates by PFGE showed that the majority of strains (11/12) belonged to two well-known international clones (EMRSA-15 and USA300) and their variations. High variability regarding SCCmec IV subtypes, susceptibility patterns and PVL toxin production were found among members of the USA300 clonal group, even when displaying the same PFGE profiles. The remaining MRSA strain belonged to sequence type (ST) 8, agr group I and carried SCCmec type I. Both community-associated MRSA and healthcare-associated MRSA epidemic international clones circulate among outpatients in our region. It is alarming that members of the most represented clonal group in our collection (USA300) can acquire multiresistance as well as PVL genes. Infection control measures in our area should be improved to avoid the selection of microorganisms displaying both traits simultaneously as well as the spread of these epidemic international clones.     

Enriching modern pharmacotherapy through synergy assessment for the combination of natural products and synthetic drugs

5-O-methylglovanon (5-O-MG) is a bioactive compound first isolated and characterized from Glycosmis plants. In this issue, Zhou et al. evaluated the anti-staphylococcal effects of 5-O-MG against ampicillin-resistant isolates of Staphylococcus aureus and S. epidermidis. The authors showed that the combination of 5-O-MG and ampicillin significantly increased the susceptibility of Staphylococcus strains to the drugs by decreasing MICs with a comparable anti-staphylococcal effect to that of β-lactamase inhibitors, suggesting that herbal compounds such as 5-O-MG may be potential candidates for the inhibitor of β-lactamases. This study is another example of synergy assessment of natural products in drug development to likely enrich modern pharmacotherapy.     

Antimicrobial Properties of Brevinin‐2‐Related Peptide and its Analogs: Efficacy Against Multidrug‐Resistant Acinetobacter baumannii

Brevinin‐2 related peptide (B2RP; GIWDTIKSMG¹⁰KVFAGKILQN²⁰L.NH₂), first isolated from skin secretions of the mink frog Lithobates septentrionalis, shows broad‐spectrum antimicrobial activity but its therapeutic potential is limited by moderate hemolytic activity. The peptide adopts an α‐helical conformation in a membrane‐mimetic solvent but amphipathicity is low. Increasing amphipathicity together with hydrophobicity by the substitutions Lys¹⁶→Leu and Lys¹⁶→Ala increased hemolytic activity approximately fivefold without increasing antimicrobial potency. The substitution Leu¹⁸→Lys increased both cationicity and amphipathicity but produced decreases in both antimicrobial potency and hemolytic activity. In contrast, increasing cationicity of B2RP without changing amphipathicity by the substitution Asp⁴→Lys resulted in a fourfold increase in potency against Escherichia coli [minimal inhibitory concentration (MIC) = 6 μm ) and twofold increases in potency against Staphylococcus aureus (MIC = 12.5 μm ) and Candida albicans (MIC = 6 μm ) without changing significantly hemolytic activity against human erythrocytes (LC₅₀ = 95 μm ). The emergence of antibiotic‐resistant strains of the Gram‐negative bacterium Acinetobacter baumannii constitutes a serious risk to public health. B2RP (MIC = 3–6 μm ) and [Lys⁴]B2RP (MIC = 1.5–3 μm ) potently inhibited the growth of nosocomial isolates of multidrug‐resistant Acinetobacter baumannii. Although the analogs [Lys⁴, Lys¹⁸]B2RP and [Lys⁴, Ala¹⁶, Lys¹⁸]B2RP showed reduced potency against Staphylococcus aureus, they retained activity against Acinetobacter baumannii (MIC = 3–6 μm ) and had very low hemolytic activity (LC₅₀ > 200 μm ).     

Synthesis of novel 2-(3′-aryl-sydnon-4′-ylidene)-5′-substituted-[1,3,4]-thiadiazolylamines and [1,3,4]-thiadiazol-2′-yl-3-oxo-[1,2,4]-triazoles as antimicrobial agents

The title compounds (3g–n) and (6g–n) were synthesized using 3-arylsydnones as synthons, and the structures were confirmed by IR, ¹H NMR, FAB mass and CHN analysis. These compounds were evaluated for their antibacterial and the antifungal activities in terms of minimum inhibitory concentrations (MICs) against the bacterial strains E. coli, B. cereus, and the fungal strains A. niger, C. albicans. Some of the compounds have shown significant activities.