In vitro activity of linezolid and eperezolid, two novel oxazolidinone antimicrobial agents, against anaerobic bacteria

Linezolid (formerly U-100766) and eperezolid (formerly U-100592) are novel oxazolidinone antimicrobial agents that are active against multi-drug-resistant staphylococci, streptococci, enterococci, corynebacteria, and mycobacteria. Preliminary studies also demonstrated that the compounds inhibited some test strains of anaerobic bacteria. Therefore, we extended the in vitro evaluation of these agents to include a total of 54 different anaerobic species. Minimal inhibitory concentration (MIC) values were determined using a standard agar dilution method for 143 anaerobic bacterial isolates. Eperezolid and linezolid demonstrated potent activity against the anaerobic Gram-positive organisms with most MIC values in the range of 0.25-4 microg/mL. Viridans streptococci demonstrated MICs of 1-2 microg/mL; Peptostreptococcus species and Propionibacterium species were inhibited by 相似文献   

Methicillin resistance study in clinical isolates of coagulase-negative staphylococci and determination of their susceptibility to alternative antimicrobial agents

AIMS: To achieve reliable detection of methicillin resistance in clinical isolates of coagulase-negative staphylococci. METHODS AND RESULTS: Strains (105) were evaluated by normatized antimicrobial susceptibility methods, and for the presence of the methicillin resistance-determining mecA gene, using the polymerase chain reaction. Correlation between phenotypic and genotypic methods was obtained in 87.6% of the samples. Six strains, classified as methicillin-susceptible by phenotypic assays, revealed the presence of the mecA gene, indicating that methicillin resistance expression was probably repressed. Another seven isolates failed to show mecA amplification after displaying methicillin resistance in phenotypic evaluations. The susceptibility of the methicillin-resistant isolates to other antimicrobial agents was variable. CONCLUSION: Genotypic determination of the mecA gene proved to be the most reliable method for detection of methicillin resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: Correct assessment of methicillin resistance, such as that attained through genotyping, is essential for defining therapeutic strategies, particularly when treating severely compromised patients.     

In vitro susceptibilities of Aeromonas genomic species to 69 antimicrobial agents

A total of 217 strains representing all 14 currently described genomic species in the genus Aeromonas were tested for susceptibility to 69 antimicrobial agents by a microdilution method. All species were susceptible to tetracyclines, quinolones, chloramphenicol, and most of the aminoglycosides and the cephalosporins, but were resistant to lincosamides, vancomycin, teicoplanin and some penicillins. In general, no significant differences were found that correlated with the taxonomic designation or the origin of the isolates tested. The microdilution method proved to be easy to perform allowing susceptibility testing of extensive strain collections for a large number of antimicrobial agents.     

耐碳青霉烯类肠杆菌科细菌体外抗菌活性分析

目的了解临床分离的59株碳青霉烯酶类抗生素耐药的肠杆菌科细菌(CRE)体外药敏情况。方法采用法国生物梅里埃公司VITEK-2Compact全自动细菌分析鉴定系统进行细菌鉴定及药敏,MALDI-TOF MS确认。琼脂稀释法测定临床常用抗生素的最低抑菌浓度。结果分离的菌株以肺炎克雷伯菌为主。59株CRE除对亚胺培南和美罗培南耐药率100.0%外,对哌拉西林/他巴唑坦和阿莫西林/克拉维酸同样完全耐药。头孢他啶、头孢噻肟、氨曲南耐药率分别为91.5%、98.5%和94.8%。阿米卡星有较好的抗菌活性,耐药率为44.8%。替加环素耐药率最低,为22.0%。结论 CRE耐药率较高,头孢类、青霉素类及其复合制剂单独用药不适合作为本地区CRE菌株抗菌药物,需联合用药。替加环素目前可作为CRE理想用药,阿米卡星也可作为次选。     

In vitro activity of vancomycin, quinupristin/dalfopristin, and linezolid against intact and disrupted biofilms of staphylococci

 

Shed cells or disrupted parts of the biofilm may enter the circulation causing serious and very hard to treat biofilm-associated infections. The activity of antimicrobial agents against the shed cells/disrupted biofilms is largely unknown.

Methods

We studied the in vitro susceptibility of intact and disrupted biofilms of thirty clinical isolates of methicillin-resistant and methicillin–susceptible Staphylococcus aureus (MRSA and MSSA) and Staphylococcus epidermidis to vancomycin, quinupristin/dalfopristin, and linezolid and compared it to that of the suspended (planktonic) cells.

Results

Bacteria in the disrupted biofilms were as resistant as those in the intact biofilms at the minimum inhibitory concentrations of the antibiotics. At higher concentrations, bacteria in the disrupted biofilms were significantly (P < 0.001) less resistant than those in the intact biofilms but more resistant than the planktonic cells. Quinupristin/dalfopristin showed the best activity against cells of the disrupted biofilms at concentrations above MICs and vancomycin, at 500 and 1,000 μg/ml, was significantly more active against the biofilms of MRSA and S. epidermidis

Conclusion

The difficulty of treating biofilm-associated infections may be attributed not only to the difficulty of eradicating the biofilm focus but also to the lack of susceptibility of cells disrupted from the biofilm to antimicrobial agents.     

In vitro action of a combination of selected antimicrobial agents and chondroitin sulfate

Chondroitin sulfate (CS), a highly anionic polymer and the most predominant sulfated glycosaminoglycan in connective tissues, was investigated regarding to its interaction with cationic disinfectants, which are used as antiinfectives in humans. Combinations of cetylpyridiniumchloride (CPC), chlorhexidine (CHex), and polyhexamethylene biguanide (PHMB) with CS, respectively, were prepared and the resulting microbicidal activity of the mixtures was tested in the quantitative suspension test without organic matter. Polyvidone-iodine and Ringer's solution were used as controls. Even precipitated, the resulting test combinations behave differently against Staphylococcus aureus, Enterococcus faecium, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. CPC/CS demonstrated only microbicidal activity against Gram-positive bacteria, and CHex/CS was more active against Gram-negative bacteria and C. albicans. PHMB/CS, especially in combination with CS-A, only revealed an antimicrobial effect against P. aeruginosa after 60 min action. The interaction of cationic disinfectants with CS showed depending on the investigated microorganism a more or less controlled sustained release manner of the microbicidal agent from the precipitated complex, with the only exception of PHMB in combination with CS-C, which is completely neutralized. Polyvidone-iodine and Ringer's solution were not affected by CS.     

Prevalence and antimicrobial susceptibility of staphylococci isolated from saliva of clinically normal cats

Samples were collected from 150 adult cats, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, enrofloxin and tetracycline. Methicillin resistance was also determined. One hundred and four isolates were obtained (69.3% of samples). Coagulase-negative species were most common, and the most frequently isolated (33 samples) species was Staph. felis. Other coagulase-negative species, such as Staph. haemolyticus, Staph. simulans, Staph. epidermidis and Staph. saprophyticus were also isolated. Coagulase-positive staphylococci were obtained from 30 cats, and the only species recovered in this group was Staph. intermedius. Resistance to antibiotics was frequently observed, with 68.2% of the isolates showing resistance to at least one drug. Resistance to Penicillin G was observed in 68 of the 104 isolates (65.4%), 23 samples were resistant to oxacillin (22.1%), 33 to tetracycline (31.7%) and 24 to enrofloxin (23.1%). Gentamicin was the most active antimicrobial agent. The role of these microorganisms in the saliva of cats is discussed.     

支原体对抗生素的体外敏感性研究

目的研究非淋菌性尿道(宫颈)炎(NGU)患者支原体对12种抗生素敏感性,指导临床治疗。方法男性标本取尿道拭子．女性标本取宫颈拭子,采用支原体培养鉴定及药敏试剂盒进行体外药敏测定。结果126株解脲支原体(Uu)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、克拉霉素、四环素、阿奇霉素、罗红霉素、司帕沙星、甲砜霉素、红霉素、可乐必妥和壮观霉素。12株人型支原体(Mh)对12种抗生素敏感性从高至低依次为交沙霉素、强力霉素、美满霉素、司帕沙星、四环素、壮观霉素、可乐必妥、甲砜霉素、红霉素、阿奇霉素、克拉霉素和罗红霉素。结论支原体耐药情况相当普遍。Uu、Mh对相同抗生素具有不同的敏感性。治疗时可依据药敏结果选择用药。     

In vitro susceptibility to 9 antifungal agents of 14 strains of Zygomycetes isolated from clinical specimens

Fourteen clinical isolates of Zygomycetes were tested for their in vitro susceptibility to nine antifungal agents. Susceptibility assessment was performed using a microtiter broth dilution method. Synthetic broth with YNB and glucose was used for 5-fluorocytosine and BHI broth for all the other antimycotics. Amphotericin B exhibited the strongest activity against all isolates tested. MIC values of other two polyenes — nystatin and pimaricin — ranged within the susceptibility limits, with a little pronounced higher activity of pimaricin. The isolates of the genusAbsidia andSyncephalastrum were well sensitive to all antimycotics with the exception of 5-fluorocytosine and naftifine. A very weak or zero growth inhibitory effect against all members of the generaMucor andRhizopus was found in azoles, 5-fluorocytosine and naftifine.     

Flow cytometric determination of Enterococcus spp. susceptibility to four antimicrobial agents

Two Enterococcus strains (E. faecalis and E. faecium) isolated from 2 patients in an intensive care unit (blood and drain, respectively) were analyzed for susceptibility to 4 antibiotics (penicillin, vancomycin, gentamicin, streptomycin) by agar dilution standard method (MICs), time-kill and flow cytometry. We compared the data from classical methods of antibiotic susceptibility detection, that are compulsory 24 hrs long and flow cytometry results at 5 and 24 hrs cultivation. The results from both classical and flow cytometric analyses were highly cogent and revealed the fact that flow cytometry is very useful in early diagnosis of bacterial resistance to antibiotics.     

Increase in the in vitro susceptibility of Staphylococcus aureus to antimicrobial agents in the presence of Candida albicans.

In experiments with mixed cultures of Staphylococcus aureus and Candida albicans both in the absence and in the presence of 5-fluorocytosine (5-FC), we have observed that (1) there is an inhibition of S. aureus growth in mixed cultures with C. albicans in media supplemented with 1 microgram/mL of 5-fc and that 5-FC has no effect on staphylococci in pure cultures; (2) this inhibition occurred with clinically isolated and laboratory strains and could be reversed by specific metabolites; (3) Staphylococcus aureus was inhibited by filtrates of C. albicans cultures treated with 5-FC and this seemed to be favored by some C. albicans filterable product which can affect the cell wall and the permeability of the staphylococcal cells since they become sensitive to 5-FC; (4) nine other commonly used antimicrobials showed an increased inhibitory activity against S. aureus in mixed cultures with C. albicans; and (5) there is a decrease in the number of precipitating antigens of S. aureus and of the activity of alpha toxin when this species was grown with both C. albicans and 5-FC. Our results indicate that the susceptibility of some species to antimicrobials could be significantly modified in the presence of other species. One cannot exclude that a similar phenomenon could happen in hosts under treatment with antibiotics against infection.     

Identification and susceptibility to antimicrobial agents of strictly anaerobic bacteria isolated from hospitalized patients

The aim of this study was to identify anaerobic strains isolated in 2001 from clinical specimens obtained from patients of Warsaw hospital and to evaluate a susceptibility of these strains to antimicrobial agents. In 2001 two hundred and twenty five clinical strains of obligate anaerobes were cultured, which were identified in the automatic ATB system (bioMérieux, France) using biochemical tests API 20 A. Drug-susceptibility of strains was determined also in ATB system with the use of ATB ANA strips. C. difficile strains were isolated on selective CCCA medium. Toxins A/B of C. difficile directly in stool specimens were detected by means of ELISA test (TechLab, USA). Fifty four strains of Gram-negative anaerobes (B. fragilis strains dominated) and 171 strains of Gram-positive anaerobes (the greatest number of strains belonged to genus Peptostreptococcus) were cultured from clinical specimens. In the cases of antibiotic-associated diarrhea 28 C. difficile strains were isolated and C. difficile toxins A/B were detected in 39 stool samples. The most active in vitro antimicrobials against Gram-negative anaerobes were metronidazole, imipenem, ticarcillin combined with clavulanic acid and piperacillin with tazobactam. Gram-positive, clinical strains of anaerobes were the most susceptible in vitro to beta-lactam antibiotics combined with beta-lactamase inhibitors (amoxicillin/clavulanate, piperacillin/tazobactam, ticarcillin/clavulanate) and imipenem.     

Correlation of in vitro and in vivo resistance development to antimicrobial agents

Preclinical in vitro and in vivo determinations of the likelihood of an antibiotic to develop resistance can and has proven predictive of their likelihood of resistance development in patients. Problematic antibiotic/bacterial species combinations are often associated with high frequencies of single-step resistance development in that species. Thus, treatment of organisms with rapid in vitro emergence of drug resistance should be monitored carefully. In vitro studies, however, are limited in predicting resistance mediated through acquisition of a resistance plasmid.The frequency of resistance development to a drug is dependent on factors such as the drug used for selections, the concentration (i.e., dosing) of the drug, the bacterium, and the site of infection. Organisms intrinsically less susceptible to an antibiotic develop resistance rapidly due to their low therapeutic ratios. Since cross-resistance often occurs within an antibiotic class, it may be desirable to initiate therapy with a drug with low resistance-selecting potential. Optimal dosing regimens are especially critical when treating bacterial species likely to develop drug resistance. Though combination drug therapies have proven affective in experimental animal infections and in man, they do not prevent resistant variants from emerging. Understanding of drug-resistance development will contribute to our management of infectious diseases.     

Prevalence and antimicrobial susceptibility of staphylococci isolated from the skin surface of clinically normal cats

Samples were collected from 148 adult cats, processed for isolation of Staphylococcus species and tested for susceptibility to penicillin G, gentamicin, oxacillin, amoxycillin, ampicillin, cephalexin and rifampin. Methicillin resistance was also determined. Ninety-eight isolates were obtained (66% of samples). Coagulase-negative species were most common, and the most frequently isolated species (37 samples) was Staph. felis . Other coagulasenegative species, such as Staph. simulans , Staph. epidermidis and Staph. Saprophyticus were also isolated. Coagulase-positive species were obtained from 40 cats; the most frequent was Staph. intermedius (26 samples), followed by Staph. aureus (14 samples). Resistance to antibiotics was frequently observed, with 58·2% of the isolates showing resistance to at least one drug. Resistance to Penicillin G was observed in 49 of the 98 isolates (50%), 22 samples were resistant to oxacillin (22·4%) and 12 to rifampin (12·2%). Resistance to amoxycillin and ampicillin was very similar to that observed to Penicillin G. Gentamicin was the most active antimicrobial agent. Three MRSA (methicillin-resistant Staphylococcus aureus ) were isolated, which represents 21·4% of the isolates of that species. Nineteen MRS (methicillin resistant staphylococci) were also observed, distributed among Staph. intermedius (eight), Staph. simulans (six) and Staph. felis (five) isolates. The role of these micro-organisms on the skin of cats is discussed.     

In vitro susceptibility of human Blastocystis subtypes to simeprevir

Introduction and aimBlastocystis is a common enteric parasite, having a worldwide distribution. Many antimicrobial agents are effective against it, yet side effects and drug resistance have been reported. Thus, ongoing trials are being conducted for exploring anti-Blastocystis alternatives. Proteases are attractive anti-protozoal drug targets, having documented roles in Blastocystis. Serine proteases are present in both hepatitis C virus and Blastocystis. Since drug repositioning is quite trendy, the in vitro efficacy of simeprevir (SMV), an anti-hepatitis serine protease inhibitor, against Blastocystis was investigated in the current study.MethodsStool samples were collected from patients, Alexandria, Egypt. Concentrated stools were screened using direct smears, trichrome, and modified Ziehl-Neelsen stains to exclude parasitic co-infections. Positive stool isolates were cultivated, molecularly subtyped for assessing the efficacy of three SMV doses (100,150, and 200 μg/ml) along 72 hours (h), on the most common subtype, through monitoring parasite growth, viability, re-culture, and also via ultrastructure verification. The most efficient dose and duration were later tested on other subtypes.ResultsResults revealed that Blastocystis was detected in 54.17% of examined samples. Molecularly, ST3 predominated (62%), followed by ST1 (8.6%) and ST2 (3.4%). Ascending concentrations of SMV progressively inhibited growth, viability, and re-culture of treated Blastocystis, with a non-statistically significant difference when compared to the therapeutic control metronidazole (MTZ). The most efficient dose and duration against ST3 was 150 µg/ml for 72 h. This dose inhibited the growth of ST3, ST1, and ST2 with percentages of 95.19%, 94.83%, and 94.74%, successively and viability with percentages of 98.30%, 98.09%, and 97.96%, successively. This dose abolished Blastocystis upon re-culturing. Ultra-structurally, SMV induced rupture of Blastocystis cell membrane leading to necrotic death, versus the reported apoptotic death caused by MTZ. In conclusion, 150 µg/ml SMV for 72 h proved its efficacy against ST1, ST2, and ST3 Blastocystis, thus sparing the need for pre-treatment molecular subtyping in developing countries.     

In vitro multitarget activity of sulfadiazine substituted triazenes as antimicrobial,cytotoxic, and larvicidal agents

Multidrug resistance (MDR) causes difficulties in the treatment of infections and cancer. Research and development studies have become increasingly important for the strategy of preventing MDR. There is a need for new multitarget drug research and advancement to reduce the development of drug resistance in drug-drug interactions and reduce cost and toxic effects. This study aimed to determine the effects of multi-target triazene compounds on antibacterial, antifungal, antiviral, cytotoxic, and larvicidal activities were investigated in vitro. A series of 12 novel of 1,3-diaryltriazene-substituted sulfadiazine (SDZ) derivatives were synthesized, and the obtained pure products characterized in detail by spectroscopic and analytic methods (FT-IR, ¹H-NMR, ¹³C-NMR, and melting points). The antibacterial and antifungal activities of these derivatives (AH1-12) were determined by broth microdilution method. All derivatives have been evaluated in cell-based assays for cytotoxic and antiviral activities against Modified Vaccinia Virus Ankara. The larvicidal efficacy of these chemical compounds was also investigated by using Lucilia sericata (L. sericata) larvae. Twelve 1,3-diaryltriazene-substituted SDZ derivatives (AH1-12) were designed and developed as potent multitargeted compounds. Among them, the AH1 derivative showed the most antibacterial and antifungal activity. Besides, synthesized derivatives AH2, AH3, AH5, and AH7 showed higher antiviral activity than SDZ. All synthesized derivatives showed higher cytotoxic activity than SDZ. Also, they showed larvicidal activity at 72 h of the experiment. As a result, these compounds might be great leads for the development of next-generation multitargeted agents.