In vitro activity of tedizolid against 43 species of Nocardia species

The purpose of the present study was to evaluate the in vitro activity of tedizolid against several clinically significant species of Nocardia by comparing with that of linezolid. A total of 286 isolates of Nocardia species, including 236 clinical isolates recovered from patients in Japan and 50 strains (43 species) purchased from NITE Biological Resource Center, were studied. Antimicrobial susceptibility testing was performed using the broth microdilution method. For the 286 Nocardia isolates, the minimal inhibitory concentration (MIC)50 and MIC90 values of tedizolid were 0.25 and 0.5 μg/ml, and those of linezolid were 2 and 2 μg/ml, respectively. The distribution of the linezolid/tedizolid ratios (MICs of linezolid/MICs of tedizolid) showed that tedizolid had four- to eight-fold higher activity than linezolid in 96.1% (275/286) of Nocardia isolates. Both the tedizolid and linezolid MIC90 values for Nocardia brasiliensis were two-fold higher than those for the other Nocardia species. Both tedizolid and linezolid had low MIC values, 0.25-1 μg/ml and 0.5-4 μg/ml, respectively, even against nine isolates (five species) that were resistant to trimethoprim/sulfamethoxazole. One Nocardia sputorum isolate showed reduced susceptibility to tedizolid (4 μg/ml). Bioinformatics analysis suggests different resistance mechanisms than the oxazolidinone resistance seen in enterococci and staphylococci.

The in vitro activity of danofloxacin plus ceftiofur combination: implications for antimicrobial efficacy and resistance prevention

Due to the high prevalence of multi-drug resistant bacteria, combination therapy is an efficient choice for treatment of infections caused by highly resistant strains. In this study, the efficacy of ceftiofur plus danofloxacin combination was investigated against resistant Escherichia coli. The interaction between the two drugs was determined by checkerboard tests and time-kill assays. The combination was defined as bactericidal or bacteriostatic based on the minimum bactericidal concentration test results. Mutant prevention concentration test was used to evaluate the resistance tendency suppression potential of the combination. The combination had a synergistic effect against 83.00% of the isolates as verified by the checkerboard and time-kill assays. The combination was defined as bactericidal against all E. coli strains, since minimum bactericidal concentration: minimum inhibitory concentration ratios were below four thresholds and also markedly reduced mutant prevention concentration values of ceftiofur up to 4000-fold compared to its single use. Ceftiofur plus danofloxacin combination inhibited growth of E. coli strains which were resistant to ceftiofur or newer generation of fluoroquinolones. Our results suggest that ceftiofur plus danofloxacin combination has a bactericidal characteristic and can be an important alternative for the treatment of infections caused by resistant E. coli.

Functionalized 1,2,3-triazolium salts as potential agents against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis, being fatal if untreated. In search of a more effective treatment for VL, one of the main strategies is the development and screening of new antileishmanial compounds. Here, we reported the synthesis of seven new acetyl functionalized 1,2,3-triazolium salts, together with four 1,2,3-triazole precursors, and investigated their effect against different strains of L. infantum from dogs and humans. The 1,2,3-triazolium salts exhibited better activity than the 1,2,3-triazole derivatives with IC₅₀ range from 0.12 to 8.66 μM and, among them, compound 5 showed significant activity against promastigotes (IC₅₀ from 4.55 to 5.28 μM) and intracellular amastigotes (IC₅₀ from 5.36 to 7.92 μM), with the best selective index (SI ~ 6-9) and reduced toxicity. Our findings, using biochemical and ultrastructural approaches, demonstrated that compound 5 targets the mitochondrion of L. infantum promastigotes, leading to the formation of reactive oxygen species (ROS), increase of the mitochondrial membrane potential, and mitochondrial alteration. Moreover, quantitative transmission electron microscopy (TEM) revealed that compound 5 induces the reduction of promastigote size and cytoplasmic vacuolization. Interestingly, the effect of compound 5 was not associated with apoptosis or necrosis of the parasites but, instead, seems to be mediated through a pathway involving autophagy, with a clear detection of autophagic vacuoles in the cytoplasm by using both a fluorescent marker and TEM. As for the in vivo studies, compound 5 showed activity in a mouse model of VL at 20 mg/kg, reducing the parasite load in both spleen and liver (59.80% and 26.88%, respectively). Finally, this compound did not induce hepatoxicity or nephrotoxicity and was able to normalize the altered biochemical parameters in the infected mice. Thus, our findings support the use of 1,2,3-triazolium salts as potential agents against visceral leishmaniasis.

[In vitro activity of delafloxacin against bacterial isolates from osteoarticular and skin infections in Buenos Aires, Argentina]

In vitro activities of delafloxacin, ciprofloxacin and levofloxacin were evaluated by epsilometric and disk diffusion methods against 181 bacterial isolates recovered from bone and skin infections. Isolates included were 84 Staphylococcus aureus (40 MRSA and 44 MSSA), 46 coagulase-negative staphylococci (CNS), 23 Klebsiella pneumoniae and 28 Pseudomonas aeruginosa. The MIC₅₀/MIC₉₀ (mg/l) for delafloxacin, ciprofloxacin and levofloxacin, respectively, were: MRSA, 0.004/0.064, 0.25/16 and 0.125/4; MSSA, 0.002/0.004, 0.125/0.25 and 0.125/0.25; CNS, 0.008/0.25, 0.125/>32 and 0.25/>32; K. pneumoniae, 4/>32,>32/>32 and 16/>32; P. aeruginosa, 1/>32, 0,5/>32 and 4/>32. Susceptibilities for delafloxacin, ciprofloxacin and levofloxacin, respectively, were: MRSA, 97.5%, 82.5% and 82.5%; MSSA, 97.7%, 95.5% and 95.5%; CNS, 93.5%, 63.0% and 60.9%; K. pneumoniae, 21.7%, 26.1% and 43.5%; P aeruginosa, 35.7%, 53.6% and 42.8%. The disk diffusion and epsilometric methods were concordant for evaluating in vitro susceptibility in staphylococci (categorical concordance of 98.8% for S. aureus and 91.3% for CNS).

Biofilm modelling on the contact lenses and comparison of the in vitro activities of multipurpose lens solutions and antibiotics

During the contact lens (CL) usage, microbial adhesion and biofilm formation are crucial threats for eye health due to the development of mature biofilms on CL surfaces associated with serious eye infections such as keratitis. For CL related eye infections, multi drug resistant Pseudomonas aeruginosa or Staphylococcus aureus (especially MRSA) and Candida albicans are the most common infectious bacteria and yeast, respectively. In this study, CL biofilm models were created by comparing them to reveal the differences on specific conditions. Then the anti-biofilm activities of some commercially available multipurpose CL solutions (MPSs) and antibiotic eye drops against mature biofilms of S. aureus, P. aeruginosa, and C. albicans standard and clinical strains were determined by the time killing curve (TKC) method at 6, 24 and 48 h. According to the biofilm formation models, the optimal biofilms occurred in a mixture of bovine serum albumin (20% v/v) and lysozyme (2 g/L) diluted in PBS at 37 °C for 24 h, without shaking. When we compared the CL types under the same conditions, the strongest biofilms according to their cell density, were formed on Pure Vision ≥ Softens 38 > Acuve 2 ∼ Softens Toric CLs. When we compared the used CLs with the new ones, a significant increase at the density of biofilms on the used CLs was observed. The most active MPS against P. aeruginosa and S. aureus biofilms at 24 h was Opti-Free followed by Bio-True and Renu according to the TKC analyses. In addition, the most active MPS against C. albicans was Renu followed by Opti-Free and Bio-True at 48 h. None of the MPSs showed 3 Log bactericidal/fungicidal activity, except for Opti-Free against S. aureus and P. aeruginosa biofilms during 6 h contact time. Moreover, all studied antibiotic eye drops were active against S. aureus and P. aeruginosa biofilms on CLs at 6 h and 24 h either directly or as 1/10 concentration, respectively. According to the results of the study, anti-biofilm activities of MPSs have changed depending on the chemical ingredients and contact times of MPSs, the type of infectious agent, and especially the CL type and usage time.

In vitro activity of omadacycline against pathogens isolated from Mainland China during 2017-2018

Antibiotic resistance of bacterial pathogens isolated in China is a major concern. Omadacycline is a novel tetracycline derivative that has been approved for use in skin infections and community-acquired pneumonia. This study was conducted to determine the in vitro activity of omadacycline against a large collection of patient isolate medical centers across Mainland China. A total of 1041 recent clinical isolates are obtained from patients hospitalized in 29 provinces and municipalities across China. The in vitro activity of omadacycline and comparator agents was assessed using the microbroth dilution methodology. Omadacycline was active against methicillin-susceptible and -resistant Staphylococcus aureus with MIC₉₀ values of 0.25 and 1 mg/L, respectively. All isolates of Enterococcus faecalis and Enterococcus faecium, including vancomycin-resistant isolates, were inhibited by ≤ 0.25 mg/L of omadacycline. It was active against Streptococcus pneumoniae irrespective of susceptibility to penicillin or macrolides (MIC₉₀ =0.12 mg/L). The minimum inhibitory concentration (MIC) distribution of omadacycline was nearly identical against (extended-spectrum beta-lactamases) ESBL-positive, ESBL-negative, and carbapenemase-producing Escherichia coli (MIC₉₀ = 4 mg/L). Omadacycline also showed good activity against Acinetobacter baumannii, inhibiting all isolates at ≤ 8 mg/L. Against Hemophilus influenzae and Moraxella catarrhalis, the MICs of omadacycline were low and not influenced by the presence of β-lactamase. Overall, the activity of omadacycline was very good against isolates commonly associated with skin infections and pneumonia, and the susceptibility of Chinese isolates was similar to that reported for these pathogens from large surveillance studies outside China. This suggests that omadacycline could be an option for treatment of these infections in Chinese patients.

New potential drug leads against MDR-MTB: A short review

Multidrug resistant Mycobacterium tuberculosis (MDR-MTB) infections have created a critical health problem globally. The appalling rise in drug resistance to all the current therapeutics has triggered the need for identifying new antimycobacterial agents effective against multidrug-resistant Mycobacterium tuberculosis. Structurally unique chemical entities with new mode of action will be required to combat this pressing issue. This review gives an overview of the structures and outlines on various aspects of in vitro pharmacological activities of new antimycobacterial agents, mechanism of action and brief structure activity relationships in the perspective of drug discovery and development. This review also summarizes on recent reports of new antimycobacterial agents.

Repurposing of known drugs for leishmaniasis treatment using bioinformatic predictions, in vitro validations and pharmacokinetic simulations

Leishmaniasis is a neglected tropical disease caused by Leishmania parasites and is associated to more than 1.3 million cases annually. Some of the pharmacological options for treating the disease are pentavalent antimonials, pentamidine, miltefosine, and amphotericin B. However, all are associated with a wide range of adverse effects and contraindications, as well as resistance from the parasite. In the present study, we looked for pharmacological alternatives to treat leishmaniasis, with a focus on drug repurposing. This was done by detecting potential homologs between proteins targeted by approved drugs and proteins of the parasite. The proteins were analyzed using an interaction network, and the drugs were subjected to in vitro evaluations and pharmacokinetics simulations to compare probable plasma concentrations with the effective concentrations detected experimentally. This strategy yielded a list of 33 drugs with potential anti-Leishmania activity, and more than 80 possible protein targets in the parasite. From the drugs tested, two reported high in vitro activity (perphenazine EC₅₀ = 1.2 µg/mL and rifabutin EC₅₀ = 8.5 µg/mL). These results allowed us to propose these drugs as candidates for further in vivo studies and evaluations of the effectiveness on their topical forms.

Activity of omadacycline tested against Streptococcus pneumoniae from a global surveillance program (2014)

The activity of omadacycline and comparators when tested against a subset of Streptococcus pneumoniae from US and European regions of a 2014 global surveillance program (304 isolates) are reported. These MIC results were compared to those obtained when testing S. pneumoniae from 2010 surveillance (1,834 isolates). The omadacycline MIC_50/90 for S. pneumoniae (2014) was 0.06/0.06μg/mL, similar to 2010 (MIC_50/90, 0.06/0.12μg/mL). The omadacycline MIC₉₀ (0.06-0.12μg/mL) was similar for the penicillin-susceptible, -intermediate, -resistant, multidrug-resistance (MDR; ≥3 classes), and ceftriaxone nonsusceptible subgroups. Omadacycline MIC₉₀ values were 0.06-0.12μg/mL for S. pneumoniae from the US and Europe. There was a high degree of resistance with doxycycline, erythromycin and trimethoprim-sulfamethoxazole in both US and EU. For penicillin-resistant S. pneumoniae, resistance to doxycycline and tetracycline in US/Europe was 64.2/61.0% and 63.8/60.5%, respectively, erythromycin 91.2/75.1, and ceftriaxone 7.3/4.0%. The potent activity of omadacycline against S. pneumoniae indicates that omadacycline merits further study in bacterial pneumonia, especially where MDR may be a concern.

Synthesis of readily available fluorophenylalanine derivatives and investigation of their biological activity

A series of thirty novel N-acetylated fluorophenylalanine-based aromatic amides and esters was synthesized using N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide or phosphorus trichloride in pyridine. They were characterized by spectral methods and screened against various microbes (Mycobacterium tuberculosis, non-tuberculous mycobacteria, other bacteria, fungi), for their inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and cytotoxicity. All amino acids derivatives revealed a moderate inhibition of both cholinesterases with IC₅₀ values for AChE and BChE of 57.88-130.75µM and 8.25-289.0µM, respectively. Some derivatives were comparable or superior to rivastigmine, an established drug. Phenyl 2-acetamido-3-(4-fluorophenyl)propanoate was identified as the selective and most potent inhibitor of BChE. The esterification and amidation of parent acids led to an improved BChE inhibition. The esters are better inhibitors of BChE than the amides. The introduction of NO₂ and CH₃ groups into aniline ring and CF₃ moiety in phenol is translated into lower IC₅₀ values. Seven compounds showed selectivity index higher than 10 for at least one cholinesterase. Especially the esters exhibited a mild activity against Gram-positive bacteria, mycobacteria and several fungal strains with minimum inhibitory concentrations starting from 125µM. The highest susceptibility was recorded for Trichophyton mentagrophytes fungus.

In vitro activity of tigecycline alone and antimicrobial combinations against clinical Neisseria gonorrhoeae isolates

In this study, we determined the in vitro activity of various combinations of antimicrobial agents against 54 Neisseria gonorrhoeae isolates. The combined activity of ceftriaxone (CRO) and azithromycin (AZM), CRO and doxycycline (DOX), CRO and spectinomycin (SPT), cefixime (CFX) and AZM, CFX and DOX, and CFX and SPT was determined using a checkerboard method. The fractional inhibitory concentration index (FICI) values for all combinations were either additive or indifferent, and no synergistic or antagonistic effects were found. The FICI comparison in each combination did not show any difference according to the N.gonorrhoeae-resistant phenotypes and genotypic characteristics, including penicillinase-producing N. gonorrhoeae, tetracycline-resistant N. gonorrhoeae, stratified MIC of all antibiotics, and N. gonorrhoeae multiantigen sequence typing. MIC₅₀ and MIC₉₀ of tigecycline by agar dilution were 0.5 mg/L and 0.5 mg/L, respectively, which were lower than that of tetracycline and DOX. Additive/indifference results could suggest that combinations that include CRO may be used safely without a significant likelihood of generating resistance.

Salicylanilide N-monosubstituted carbamates: Synthesis and in vitro antimicrobial activity

The research of innovative antimicrobial agents represents a cutting edge topic. Hence, we synthesized and characterised novel salicylanilide N-monosubstituted carbamates. Twenty compounds were evaluated in vitro against eight bacterial strains and eight fungal species. The lowest minimum inhibitory concentrations (MICs) were found to be ⩽0.49 μM. Genus Staphylococcus, including methicillin-resistant Staphylococcus aureus, and fungus Trichophyton mentagrophytes showed uniformly the highest rate of susceptibility, whilst Gram-negative bacteria and most of the fungi were less susceptible. A wide range of carbamates provided comparable or superior in vitro antimicrobial activity in comparison to established drugs. Interestingly, extended-spectrum β-lactamase producing strain of Klebsiella pneumoniae was inhibited with MICs starting from 31.25 μM. With respect to Staphylococci, 2-[(4-bromophenyl)carbamoyl]-4-chlorophenyl phenylcarbamate exhibited the lowest MIC values (⩽0.98 μM). 2-[(4-Bromophenyl)carbamoyl]-4-chlorophenyl benzylcarbamate showed the widest spectrum of antifungal action. The results indicate that some salicylanilide carbamates can be considered to be promising candidates for future investigation.

Anti-Trichomonas vaginalis properties of the oil of Amomum tsao-ko and its major component, geraniol

CONTEXT

Trichomonosis, caused by the flagellate protozoan Trichomonas vaginalis, is the most common non-viral sexually transmitted disease (STD) and 5-nitroimidazole drugs are used for the treatment. However, a growing number of T. vaginalis isolates are resistant to these drugs, which make it becomes an urgent issue.

OBJECTIVE

The current study was designed to evaluate the anti-T. vaginalis activity of the essential oil from A. tsao-ko used in traditional Chinese medicine and as a spice and its main component, geraniol.

MATERIALS AND METHODS

The anti-T. vaginalis activities of A. tsao-ko essential oil and geraniol were evaluated by the minimum lethal concentration (MLC) and 50% inhibitory concentration (IC50) in vitro. The morphological changes of T. vaginalis were observed by transmission electron microscopy (TEM). Additionally, sub-MLC concentration treatment with sub-MLC A. tsao-ko essential oil and geraniol was also performed.

RESULTS

This study shows that MLC/IC50 of A. tsao-ko essential oil was 44.97 µg/ml/22.49 µg/ml for T. vaginalis isolate Tv1, and 89.93 µg/ml/44.97 µg/ml for T. vaginalis isolate Tv2. Those of geraniol were 342.96 µg/ml/171.48 µg/ml, respectively. After A. tsao-ko essential oil or geraniol treatment, obvious similar morphological changes of T. vaginalis were observed by TEM: the nuclear membrane was damaged, nuclei were dissolved, and the chromatin was accumulated; in the cytoplasm, numerous vacuoles appeared, rough endoplasmic reticulum dilated, the number of ribosomes were reduced, organelles disintegrated, the cell membrane was partially damaged, with cytoplasmic leakage, and cell disintegration was observed. The action time did not increase the effect of A. tsao-ko essential oil or geraniol against T. vaginalis, as no significant difference was observed after sub-MLC concentration treatment for 1, 3, and 5 h with A. tsao-ko essential oil and geraniol.

DISCUSSION AND CONCLUSION

The study describes the first report on the activity and morphological changes of A. tsao-ko essential oil and geraniol against T. vaginalis. The results obtained herein presented new opportunities for antitrichomonal drugs.

In vitro activity of Alkanna frigida extracts in comparison with glucantime against Leishmania major

BACKGROUND AND OBJECTIVES

Current chemotherapies of cutaneous leihmaniasis have faced to some problems and limitations; Development of new leishmanicidal drugs from different sources like herbal plants, are crucially important. The objective of the present study was evaluation of in vitro activity of Alkanna frigida extracts in comparison with glucantime against Leishmania major.

MATERIALS AND METHODS

L. major promastigotes were exposed to different concentrations of the A. frigida extracts, processed by ethyl acetate, ethanol, hexane and chloroform. The inhibitory effect, as the IC50, were calculated after 24, 48 and 72 hours by linear regression analysis values of the concentrations employed.

RESULTS

The significant inhibition was observed after 24 and 48 hours with different concentrations of compounds (p < 0.05 in all tests). All extracts had potent activity against proliferation of the promastigotes, comparing to the untreated negative control. It could compete with the glucantime efficacy in some concentrations. Ethyl acetate and ethanol extractions showed potent IC50 value, 106 µg/ml and 86 µg/ml, respectively. Hexane and chloroform extractions had poor efficacy after 24 hours; however, the efficacy increased after 48 and 72 hours.

CONCLUSION

The results indicated that the A. frigida has appropriate inhibitory effects on the growth of L. major promastigotes in vitro and can be of herbal targets for further investigation in vivo.

Anti-cancer studies of noble metal nanoparticles synthesized using different plant extracts

Biofunctionalized gold and silver nanoparticles synthesized using different plant extracts of guava and clove in vitro anti-cancer efficacy against four different cancer cell lines human colorectal adenocarcinoma, human kidney, human chronic myelogenous, leukemia, bone marrow, and human cervix have been studied and reported. The present experimental study suggests that flavonoids functionalized gold nanoparticles synthesized using aqueous clove buds extract are more potential than guava leaf extract towards anti-cancer activities. The microscopic and 2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide (XTT) assay infer that the functionalized irregular shaped gold nanoparticles synthesized with aqueous clove bud extract showed a satisfactory anti-cancer effect on all the cell lines. The silver nanoparticles synthesized using same extracts are devoid of anti-cancer activity. The XTT assay revealed dose-dependent cytotoxicity to cancer cell lines. The study revealed that the free radicals generated by gold nanoparticles are responsible for anti-cancer effect. To confirm the free-radical scavenging efficacy of gold nanoparticle, nitric oxide assay is followed. We observed that the gold nanoparticles swabbed the free radicals in dose-dependent manner. With continued improvements, these nanoparticles may prove to be potential anti-cancer agents.

The anti-mycobacterial activity of Lantana camara a plant traditionally used to treat symptoms of tuberculosis in South-western Uganda

INTRODUCTION

Tuberculosis continues to be a devastating public health problem. Many communities in Uganda use medicinal plants to treat various infections, including respiratory tract infections. There are claims that some can treat tuberculosis. Verifying some of these claims could lead to discovery of lead compounds for development of a TB drug.

METHODS

Chloroform and methanol extracts of L. camara collected from South-western Uganda were screened against three strains of Mycobacterium tuberculosis using the agar-well diffusion method. H37Rv, the rifampicin-resistant TMC-331 and a non-resistant wild strain (28-25271). The MIC and MBC were determined using the Agar dilution method on Middle brook 7H11.

RESULTS

The methanol extract showed the highest activity against all the three strains used, with zones of inhibition of 18.0-22.5 mm and MIC values of 20 µg/ml for H37Rv and 15 µg/ml for both TMC-331 and wild stain. The values for rifampicin were 1.0 µg/ml for both H37Rv and wild strain but rifampicin hardly showed any activity on TMC-331. The MBC value for the methanol extract of L. camara was 30µg/ml for the H37Rv, and 20µg/ml for both the TMC-331 and wild strains of M. tuberculosis. The MBC for rifampicin was 2.0µg/ml for both H37Rv and the wild strain.

CONCLUSION

We conclude that L. camara contains principles active against M. tuberculosis, which merit further research.