Partial Synergistic Effect Research Articles

Comparing the activity and interactions of the antifungal protein PeAfpA with conventional fungicides and food preservatives against mycotoxigenic fungi

SummaryPrevention of fungal contamination and the occurrence of mycotoxins in food and feeds requires the development of new antifungal approaches. The antifungal proteins (AFPs) produced by some fungi provide great potential for the control of contaminating fungi. In the present study, the antifungal activity of the protein PeAfpA from Penicillium expansum was compared with fungicides used in post‐harvest control (imazalil and thiabendazole) and food preservatives (calcium propionate, sodium, sodium benzoate, potassium sorbate, and natamycin), against 23 fungal species belonging to the genera Penicillium, Fusarium, Byssochlamys, Aspergillus and Alternaria. In general, PeAfpA had the lowest minimum inhibitory concentration (MIC) followed by natamycin, the fungicides, and the chemical preservatives. PeAfpA was able to completely inhibit the growth of all tested fungi at concentrations ranging from 0.5 to 8 μg mL−1. In addition, we assessed the effects of PeAfpA in combination with imazalil, thiabendazole, natamycin, or potassium sorbate against four representative fungal species. Our results provide evidence for partial synergistic and additive effects between the protein PeAfpA and the other compounds tested. This study concludes that PeAfpA, alone or in combination with fungicides or food preservatives, has a great potential to prevent fungal contamination and reduce the required dosage of fungicides or chemical preservatives used in food conservation.

Assessment of the Efficacy of the Antihistamine Drug Rupatadine Used Alone or in Combination against Mycobacteria.

The emergence of drug-resistant mycobacteria has rendered many clinical drugs and regimens ineffective, imposing significant economic and healthcare burden on individuals and society. Repurposing drugs intended for treating other diseases is a time-saving, cost-effective, and efficient approach for identifying excellent antimycobacterial candidates or lead compounds. This study is the first to demonstrate that rupatadine (RTD), a drug used to treat allergic rhinitis, possesses excellent activity against mycobacteria without detectable resistance, particularly Mycobacterium tuberculosis and Mycobacterium marinum, with a minimal inhibitory concentration as low as 3.13 µg/mL. Furthermore, RTD exhibited moderate activity against nonreplicating M. tuberculosis with minimal inhibitory concentrations lower than drugs targeting the cell wall, suggesting that RTD has great potential to be modified and used for the treatment of nonreplicating M. tuberculosis. Additionally, RTD exhibits partial synergistic effects when combined with clofazimine, pretomanid, and TB47 against M. tuberculosis, providing the theoretical foundation for the development of treatment regimens. Transcriptomic profiling leads us to speculate that eight essential genes may be the targets of RTD or may be closely associated with mycobacterial resistance to RTD. In summary, RTD may be a promising hit for further antimycobacterial drug or regimen optimization, especially in the case of nonreplicating mycobacteria.

New generation fluoroquinolone sitafloxacin could potentially overcome the majority levofloxacin and moxifloxacin resistance in multidrug-resistant Mycobacterium tuberculosis.

Introduction. Pre-existing fluoroquinolones (FQs) resistance is a major threat in treating multidrug-resistant (MDR) tuberculosis. Sitafloxacin (Sfx) is a new broad-spectrum FQ.Hypothesis. Sfx is more active against drug-resistant Mycobacterium tuberculosis (Mtb) isolates.Aim. To determine whether there is cross-resistance between Sfx and ofloxacin (Ofx), levofloxacin (Lfx) and moxifloxacin (Mfx) in MDR Mtb.Methods. A total of 106 clinical Mtb isolates, including 23 pan-susceptible and 83 MDR strains, were analysed for Sfx, Lfx and Mfx resistance using MIC assay. The isolates were also subjected to whole-genome sequencing to analyse drug-resistant genes.Results. Sfx exhibited the most robust inhibition activity against Mtb clinical isolates, with a MIC50 of 0.0313 µg ml-1 and MIC90 of 0.125 µg ml-1, which was lower than that of Mfx (MIC50 = 0.0625 µg ml-1, MIC90 = 1 µg ml-1) and Lfx (MIC50 = 0.125 µg ml-1, MIC90 = 2 µg ml-1). We determined the tentative epidemiological cut-off values as 0.5 µg ml-1 for Sfx. Also, 8.43% (7/83), 43.37% (36/83), 42.17% (35/83) and 51.81% (43/83) MDR strains were resistant to Sfx, Mfx, Lfx and Ofx, respectively. Cross-resistance between Ofx, Lfx and Mfx was 80.43% (37/46). Only 15.22% (7/46) of the pre-existing FQs resistance isolates were resistant to Sfx. Among the 30 isolates with mutations in gyrA or gyrB, 5 (16.67%) were Sfx resistant. The combination of Sfx and rifampicin could exert partial synergistic effects, and no antagonism between Sfx and six clinically important anti-Mtb antibiotics was evident.Conclusion. Sfx exhibited superior activity against MDR isolates comparing to Lfx and Mfx, and could potentially overcome the majority pre-existing FQs resistance in Mtb strains.

Characterization of the Human Plasma Biofilm Model (hpBIOM) to Identify Potential Therapeutic Targets for Wound Management of Chronic Infections.

The treatment of chronic wounds still represents a major challenge in wound management. Recent estimates suggest that 60-80% of chronic wounds are colonized by pathogenic microorganisms, which are strongly considered to have a major inhibiting influence on the healing process. By means of an innovative biofilm model based on human plasma, the time-dependent behavior of various bacterial strains under wound-milieu-like conditions were investigated, and the growth habits of different cocci species were compared. Undescribed fusion events between colonies of MRSA as well as of Staphylococcus epidermidis were detected, which were associated with the remodeling and reorganization of the glycocalyx of the wound tissue. After reaching a maximum colony size, the spreading of individual bacteria was observed. Interestingly, the combination of different cocci species with Pseudomonas aeruginosa in the human plasma biofilm revealed partial synergistic effects in these multispecies organizations. RT-qPCR analyses gave a first impression of the relevant proteins involved in the formation and maturation of biofilms, especially the role of fibrinogen-binding proteins. Knowledge of the maturation and growth behavior of persistent biofilms investigated in a translational human biofilm model reflects a starting point for the development of novel tools for the treatment of chronic wounds.

Photo-oxidative aromatization and photo-rearrangement of 2, 4-diaryl-5-oxohexahydroquinolines

Various 2,4-bisaryl substituted 5-oxohexahydroquinolines were synthesized and the electronic effects of 2- and 4-substitutions on the photochemical behaviors of these compounds were investigated. UV light irradiation of these compounds resulted in the occurrence of two types of photoreactions; oxidative normal photo-oxidation and photo-rearranged reactions. In both reactions, the aromatization of the heterocyclic 1,4-dihydropyridine ring to the pyridine ring was observed. The photochemical results indicated the involvement of the radical intermediate, responsible for the aryl ring migration and the occurrence of the photo-rearrangement reaction. The partial synergistic effect of the capto-dative radical stabilization of the involved radical intermediate was supported by the results of the experimental works and the DFT-computational studies. X-ray crystal structure analysis of two of 5-oxohexahydroquinoline compounds indicated that i). The C4-aryl ring occupies the pseudo-axial position of the twisted-boat conformation of the heterocyclic dihydropyridine ring and, ii). Owing to the steric ortho-repulsion, the C2-aryl ring has a non-planar orientation concerning the attached CC double bond of the heterocyclic ring. These observations were in good agreement with the data of the DFT-computational studies and the X-ray crystal structure analysis.

Hydroquinine Inhibits the Growth of Multidrug-Resistant Pseudomonas aeruginosa via the Suppression of the Arginine Deiminase Pathway Genes.

Hydroquinine has antimicrobial potential with demonstrated activity against several bacteria, including multidrug-resistant (MDR) P. aeruginosa reference strains. Despite this, there is limited evidence confirming the antibacterial activity of hydroquinine against clinical isolates and the underlying mechanism of action. Here, we aimed to investigate the antibacterial effect of hydroquinine in clinical P. aeruginosa strains using phenotypic antimicrobial susceptibility testing and synergistic testing. In addition, we examined the potential inhibitory mechanisms against MDR P. aeruginosa isolates using informatic-driven molecular docking analysis in combination with RT-qPCR. We uncovered that hydroquinine inhibits and kills clinical P. aeruginosa at 2.50 mg/mL (MIC) and 5.00 mg/mL (MBC), respectively. Hydroquinine also showed partial synergistic effects with ceftazidime against clinical MDR P. aeruginosa strains. Using SwissDock, we identified potential interactions between arginine deiminase (ADI)-pathway-related proteins and hydroquinine. Furthermore, using RT-qPCR, we found that hydroquinine directly affects the mRNA expression of arc operon. We demonstrated that the ADI-related genes, including the arginine/ornithine antiporter (arcD) and the three enzymes (arginine deiminase (arcA), ornithine transcarbamylase (arcB), and carbamate kinase (arcC)), were significantly downregulated at a half MIC of hydroquinine. This study is the first report that the ADI-related proteins are potential molecular targets for the inhibitory effect of hydroquinine against clinically isolated MDR P. aeruginosa strains.

Evaluation of In vitro Efficacy of Meropenem/Colistin and Meropenem/Fosfomycin Combinations on Multidrug Resistant Gram-Negative Bacilli

The rate of extensively drug-resistant and pan-resistant gram-negative rods isolated as infectious agents is increasing around the world and in Türkiye. One of the important options in the treatment of these infections is the combined use of antibiotics. Therefore, the aim of this study was to investigate the in vitro effect of meropenem/colistin and meropenem/fosfomycin combinations on carbapenem-resistant gram-negative bacilli isolated as infectious agents. Escherichia coli (n= 6), Klebsiella pneumoniae (n= 10), Pseudomonas aeruginosa (n= 5), and Acinetobacter baumannii (n= 6) isolates were recovered from blood and tracheal aspirate samples of patients hospitalized in our hospital's intensive care unit were included in the study. In the first stage of the combination study, minimal inhibitory concentrations (MIC) were investigated by broth microdilution for meropenem and colistin, and agar dilution methods for fosfomycin. In the second stage of the study, synergy, partial synergy, indifference, and antagonistic effects were investigated with the checkerboard method for the meropenem/colistin combination and the agar dilution method for the meropenem/fosfomycin combination. The checkerboard results were interpreted as follows: fractional inhibitory concentration index (FICI) values ≤ 0.5 synergy, < 0.5-≤ 1 partial synergy, > 1-≤ 4 indifference and FIC values of > 4 antagonism. MIC values obtained in the study were interpreted according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) criteria. Of the 27 isolates studied with the broth microdilution method, 63% were found to be colistin-resistant and 37% susceptible. The MIC values of fosfomycin against Enterobacterales group bacteria were found to be in the range of 2-2048 mg/L. Two of the six E.coli isolates and nine of the 10 K.pneumoniae isolates were found to be resistant to fosfomycin (IV). The MIC values of ≥ 128 mg/L were found in all 11 non-fermentative gram-negative rods with intrinsic resistance to fosfomycin. In the combination of meropenem/ colistin, synergy and partial synergy were observed in 11 (40.7%) of 27 isolates, an indifference effect was observed in 13 (48.2%), and antagonistic effects were observed in three (11.1%) of the isolates. The synergy and partial synergy effects of this combination were 37.5% for Enterobacterales group bacteria, 50% for E.coli, and 30% for K.pneumoniae. Regarding the 11 non-fermentative gram-negative rods included in the study, 83.3% synergy and partial synergy was found in A.baumannii for the meropenem/colistin combination, while no synergy and partial synergistic effect was found in P.aeruginosa. Meropenem/fosfomycin synergy and partial synergy effects were 83.3% (5/6) for E.coli, 100% (8/8) for K.pneumoniae, 100% (6/6) for A.baumannii, and 25% (1/4) for P.aeruginosa. In all of the isolates studied, meropenem/fosfomycin combination was found to be more effective than the meropenem/colistin combination. It would be meaningful to support these data obtained in vitro with clinical efficacy results to be obtained as a result of the application of antibiotics in vivo, taking into account the pharmacokinetic and pharmacodynamic properties of the antibiotics used in this study.

Combined effects of salinity and polystyrene microplastics exposure on the Pacific oysters Crassostrea gigas: Oxidative stress and energy metabolism

Microplastics (MPs) pollution and salinity variation are two environmental stressors, but their combined effects on marine mollusks are rarely known. Oysters (Crassostrea gigas) were exposed to 1 × 104 particles L−1 spherical polystyrene MPs (PS-MPs) of different sizes (small polystyrene MPs (SPS-MPs): 6 μm, large polystyrene MPs (LPS-MPs): 50–60 μm) under three salinity levels (21, 26, and 31 psu) for 14 days. Results demonstrated that low salinity reduced PS-MPs uptake in oysters. Antagonistic interactions between PS-MPs and low salinity mainly occurred, and partial synergistic effects were mainly induced by SPS-MPs. SPS-MPs induced higher lipid peroxidation (LPO) levels than LPS-MPs. In digestive glands, low salinity decreased LPO levels and glycometabolism-related gene expression, which was related to salinity levels. Low salinity instead of MPs mainly affected metabolomics profiles of gills through energy metabolism and osmotic adjustment pathway. In conclusion, oysters can adapt to combined stressors through energy and antioxidative regulation.

Chemical Composition, Antibacterial and Combinatorial Effects of the Essential Oils from Cymbopogon spp. and Mentha arvensis with Conventional Antibiotics

This work aimed to evaluate the chemical composition and antibacterial activity of essential oils of Cymbopogon citratus (CCEO), Cymbopogon khasianus (CKEO), and Mentha arvensis (MAEO) against two Gram-negative (Escherichia coli, Klebsiella pneumoniae) and three Gram-positive (Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis) microbial strains and their combination with antibiotics (chloramphenicol, ampicillin, erythromycin) to observe the synergistic behavior between them. The essential oils (EOs) were investigated by the GC-MS (gas chromatography mass spectrometry) method. The synergistic effect between EOs and antimicrobial agents was analyzed by broth dilution assay. (-)-carvone (52.48%), geraniol (57.66%), and citral (37.83%) were the major components identified in EOs of MAEO, CKEO, and CCEO, respectively. According to the antibacterial activity, EOs demonstrated strong antibacterial activity with MIC values ranging from 0.7 to 18 mg/mL. The interaction between the combination of EOs and antibiotics was determined in terms of FICI (Fractional Inhibitory Concentration Index). Some combinations displayed a partial synergistic effect, and some showed a synergistic and others displayed no effect against bacterial strains. The best synergistic action was shown by the combination of CCEO and Chloramphenicol against E. coli with a FICI value of 0.4. Three to four fold reductions in the MIC value of both essential oil and antibiotics were observed. Therefore, this synergistic interaction of the most active EOs with synthetic antibiotics could lead to new combination therapies for combating infections caused by multidrug-resistant microbes at sufficiently low concentrations in the pharmaceutical and food industry.

Nosiheptide Harbors Potent In Vitro and Intracellular Inhbitory Activities against Mycobacterium tuberculosis.

Multidrug-resistant tuberculosis (MDR-TB) is often associated with poor clinical outcomes. In this study, we evaluated the potential of nosiheptide (NOS) as a new drug candidate for treating Mycobacterium tuberculosis infections, including MDR-TB. The antimicrobial susceptibility testing was performed to determine the MICs of NOS against 18 reference strains of slowly growing mycobacteria (SGM) and 128 clinical isolates of M. tuberculosis. The postantibiotic effects (PAE) and interaction with other antituberculosis drugs of NOS were also evaluated using M. tuberculosis H37Rv. Fifteen out of the 18 tested reference strains of SGM had MICs far below 1 μg/mL. From the 128 M. tuberculosis clinical isolates, the MIC50 and MIC90 were 0.25 μg/mL and 1 μg/mL, respectively; the tentative epidemiological cutoff (ECOFF) was defined at 1 μg/mL. Furthermore, a Lys89Thr mutation was found in one M. tuberculosis isolate with a MIC of NOS >8 μg/mL. After 24 h of incubation, NOS at 1 μg/mL inhibited 25.79 ± 1.22% of intracellular bacterial growth, which was comparable with the inhibitory rate of 25.71 ± 3.67% achieved by rifampin at 2 μg/mL. Compared to rifampicin and isoniazid (INH), NOS had a much longer PAE, i.e., a value of about 16 days. In addition, a partial synergy between NOS and INH was observed. NOS has potent inhibitory activities against M. tuberculosis in vitro as well as in macrophages. Furthermore, the long PAE and partial synergistic effect with INH, in addition to the added safety of long-term use as a feed additive in husbandry, provide support for NOS being a promising drug candidate for tuberculosis treatment. IMPORTANCE This study is aimed at chemotherapy for MDR-TB, mainly to explore the anti-TB activity of the existing chemotherapeutic reagent. We found that NOS has potent inhibitory activities against M. tuberculosis in vitro regardless of the drug-resistant profile. Furthermore, NOS also showed the long PAE and partial synergistic effect with INH and is nontoxic, providing support for its promise as a drug candidate for drug-resistant tuberculosis treatment.

Combination effect of epsilon-poly-L-lysine and antibiotics against common bacterial pathogens.

Epsilon-poly-L-lysine (EPL) is an antimicrobial peptide with low mammalian toxicity; thus, it is commonly used as food preservative. Here, the capacity of EPL to improve the efficacy of the antibiotics ampicillin (AMP), gentamycin (GEN), tetracycline (TCN), and methicillin (MET) against four bacterial pathogens, namely Pseudomonas aeruginosa PAO1, Klebsiella pneumoniae CG43, MET-sensitive Staphylococcus aureus ATCC 25923 (MSSA), and MET-resistant S. aureus ATCC 33591 (MRSA), was investigated. Some antibiotic-EPL combinations, i.e., AMP-EPL, GEN-EPL, and TCN-EPL, were particularly active against the pathogens through synergy, partial synergy, or additive effects. Additionally, MET-EPL displayed a partial synergistic effect against MRSA. GEN-EPL had the most powerful antimicrobial effect against MSSA: it eradicated the bacterium within an hour. Conversely, AMP-EPL and MET-EPL were the least potent combinations against MRSA, and TCN-EPL was least potent against K. pneumoniae; for these combinations, bactericidal activities occurred >10 h after initial treatments. All antibiotic-EPL treatments showed inhibitory activities against P. aeruginosa biofilm formation and enhanced preformed biofilm disruption in vitro. Similarly, the inhibition of biofilm formation on a porcine skin model was observed. Moreover, no significant cytotoxicity was detected for any antibiotic-EPL treatment in tests using Balb/3t3 fibroblasts. Given the rise in antibiotic-resistant bacteria, combining antibiotics with EPL may enhance antibiotic effectiveness, as shown in this study, while helping to avoid antimicrobial resistance.

Restoration of antibacterial activity of inactive antibiotics via combined treatment with a cyanographene/Ag nanohybrid

The number of antibiotic-resistant bacterial strains is increasing due to the excessive and inappropriate use of antibiotics, which are therefore becoming ineffective. Here, we report an effective way of enhancing and restoring the antibacterial activity of inactive antibiotics by applying them together with a cyanographene/Ag nanohybrid, a nanomaterial that is applied for the first time for restoring the antibacterial activity of antibiotics. The cyanographene/Ag nanohybrid was synthesized by chemical reduction of a precursor material in which silver cations are coordinated on a cyanographene sheet. The antibacterial efficiency of the combined treatment was evaluated by determining fractional inhibitory concentrations (FIC) for antibiotics with different modes of action (gentamicin, ceftazidime, ciprofloxacin, and colistin) against the strains Escherichia coli, Pseudomonas aeruginosa, and Enterobacter kobei with different resistance mechanisms. Synergistic and partial synergistic effects against multiresistant strains were demonstrated for all of these antibiotics except ciprofloxacin, which exhibited an additive effect. The lowest average FICs equal to 0.29 and 0.39 were obtained for colistin against E. kobei and for gentamicin against E. coli, respectively. More importantly, we have experimentally confirmed for the first time, that interaction between the antibiotic's mode of action and the mechanism of bacterial resistance strongly influenced the combined treatment’s efficacy.

Polymyxin B Combined with Minocycline: A Potentially Effective Combination against blaOXA-23-harboring CRAB in In Vitro PK/PD Model.

Polymyxin-based combination therapy is commonly used to treat carbapenem-resistant Acinetobacter baumannii (CRAB) infections. In the present study, the bactericidal effect of polymyxin B and minocycline combination was tested in three CRAB strains containing blaOXA-23 by the checkerboard assay and in vitro dynamic pharmacokinetics/pharmacodynamics (PK/PD) model. The combination showed synergistic or partial synergistic effect (fractional inhibitory concentration index ≤0.56) on the tested strains in checkboard assays. The antibacterial activity was enhanced in the combination group compared with either monotherapy in in vitro PK/PD model. The combination regimen (simultaneous infusion of 0.75 mg/kg polymyxin B and 100 mg minocycline via 2 h infusion) reduced bacterial colony counts by 0.9–3.5 log10 colony forming units per milliliter (CFU/mL) compared with either drug alone at 24 h. In conclusion, 0.75 mg/kg polymyxin B combined with 100 mg minocycline via 2 h infusion could be a promising treatment option for CRAB bloodstream infections.

Screening, characterisation and bioactivities of green fabricated TiO2 NP via cyanobacterial extract.

The present study was aimed at exploring 37 strains of cyanobacteria for the biofabrication of TiO2 NP and evaluation of their antioxidant, antifungal, antibacterial and hemolytic activity. Screening of cyanobacterial strains was done via SEM, followed by optimisation and characterisation of the best strain. Synechocystis NCCU-370 appeared as the best strain for the synthesis of TiO2 NP in terms of size (73.39nm) and time (24h) after screening. Following optimisation, nanoparticles were synthesised in 12h having an average grain size of 16nm. The aqueous extract preparation required heating of 5mg/ml of powdered biomass to 60°C for 10min. Optimum conditions for the synthesis of TiO2 NP were found to be pH 7, 30°C and 12-h cell extract exposure to 0.1mM of salt. Antioxidant activity was evaluated via DPPH, ABTS and FRAP assay. Antifungal potential was explored against Candida albicans (MIC = 125µg/ml), Candida glabrata (MIC = 500µg/ml) and Candida tropicalis (MIC = 250µg/ml), whereas antibacterial potential was gauged for Bacillus cereus (MIC = 31.25µg/ml), Escherichia coli (MIC = 31.25µg/ml) and Klebsiella pneumoniae (MIC = 500µg/ml) strains. Biogenic TiO2 NP demonstrated partial synergistic effect and excellent biocompatibility.

New weapons to fight a new enemy: A systematic review of drug combinations against the drug-resistant fungus Candida auris.

Candida auris is an emerging and drug-resistant pathogen. Drug combination is a promising approach against such pathogens. This study was conducted to provide an overview of all the studied drug combinations against C.auris. Relevant articles reporting results of any drug/non-drug combinations against C.auris were found by a systematic search in PubMed, Scopus and Web of Science (ISI), and in Google Scholar up to 1 October 2020. From 187 articles retrieved in the primary search, 23 met the inclusion criteria. In total, 124 different combinations including antifungal with antifungal (45), antifungal with other antimicrobials (11), antifungal with non-antimicrobials (32), antifungal with natural compounds (25) and between natural compounds (11) have been reported. Complete or partial synergistic effects have been reported for 3 out of 45 (6.67%) combinations of two antifungal agents, 8 out of 11 (72.73%) combinations involving antifungal agents and antimicrobials, 15 out of 32 (46.88%) of combinations between antifungal agents with non-antimicrobials, 16 out of 25 (64%) of combinations involving antifungal agents and natural compounds, and 3 out of 11 (22.27%) of combinations involving multiple natural compounds. Antagonistic interactions have been reported for 1 out of 32 (3.13%) and 8 out of 25 (32%) of combinations between antifungal drugs with non-antimicrobials and with natural compounds, respectively. Different drugs/compounds could potentiate the activity of antifungal drugs using this approach. However, despite the availability of this promising initial data, many more studies will be required to elucidate whether favourable interactions observed in vitro might translate into tangible clinical benefits.

Differential expression of blaCTX-M-33 with vancomycin/trimethoprim combination in Escherichia coli-producing extended-spectrum β-lactamase isolated from intensive care unit-acquired urinary tract infection

Aim: The aim of this study was to develop combination approach for the treatment of Escherichia coli-producing extended-spectrum β-lactamases (ESBLs) isolated from intensive care unit (ICU)-acquired urinary tract infections (UTIs). Materials and Methods: The observational study was conducted between January 5, 2018- June 5, 2019 to isolate and detect E. coli from UTI patients admitted to ICUs in Shahid Rajaee hospital, Gachsaran, Iran. Morphological, biochemical and molecular methods were conducted to identify E. coli isolates. Phenotypic confirmation of E. coli producing ESBL was performed using ESBL disc diffusion test according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The combination index assay set-up was based on CLSI guidelines to investigate antibacterial susceptibilities to vancomycin alone and in combination with trimethoprim and interpreted with the fractional inhibitory concentration (FIC) index. Eventually, the expression levels of blaCTX-M-33 gene were determined by real-time quantitative reverse transcription–polymerase chain reaction. Results: A total of 90 ICU-acquired UTIs occurred among 255 patients. The combination index assay results showed that vancomycin/trimethoprim combination would be reduced its minimal inhibitory concentration90 value. The vancomycin/trimethoprim combination revealed partial synergistic and indifferent effects (FIC = 0.52–1.50) in the isolates of E. coli-producing ESBL. The results of gene expression analysis indicated that vancomycin/trimethoprim combination caused downregulation of blaCTX-M-33 gene at negligible levels by 55.56–58.82-fold and stopped drug resistant. Conclusion: Vancomycin/trimethoprim combination may diminish resistance in the E. coli-producing ESBL isolated from ICU-acquired UTI patients.

Expression analysis of drug-resistant gene (blaOXA-51) in carbapenemases producing Acinetobacter baumannii treated with imipenem/sulbactam combination

Drug-resistant Acinetobacter baumannii is a frightening reality. The aim of this study is to examine the expression profiles of blaOXA-51 gene in carbapenemases producing A. baumannii treated with imipenem/sulbactam combination. Carbapenemases producing A. baumannii was identified among clinical isolates of A. baumannii obtained from patients at Shahid Rajaee hospital, Gachsaran, Iran, from January to June 2018. Synergism testing of imipenem/sulbactam on carbapenemases producing A. baumannii was carried out by broth microdilution method. Eventually, the expression of blaOXA-51 gene was carried out to investigate the inhibitory properties of imipenem/sulbactam combination against carbapenemases producing A. baumannii using quantitative real time RT-PCR. Among A. baumannii isolates, 24% were carbapenemases producing A. baumannii. Imipenem/sulbactam combination revealed synergistic and partial synergistic effect for all tested isolates (FIC= 0.313-0.75). Finally, imipenem/sulbactam combination displayed significant down-regulation of blaOXA-51 gene in carbapenemases producing A. baumannii. Imipenem synergizes with sulbactam against carbapenemases producing A. baumannii by targeting of the blaOXA-51 gene.

Drug repurposing: Antimicrobial and antibiofilm effects of penfluridol against Enterococcus faecalis

The bacterium Enterococcus faecalis has increasingly attracted global attention as an important opportunistic pathogen due to its ability to form biofilms that are known to increase drug resistance. However, there are still no effective antibiofilm drugs in clinical settings. Here, by drug repurposing, we investigated the antibacterial activity of penfluridol (PF), an oral long‐acting antipsychotic approved by the FDA, against E. faecalis type strain and its clinical isolates. It was found that PF inhibited the growth of E. faecalis planktonic cells with the MIC and MBC of 7.81 µg/ml and 15.63 ~ 62.50 µg/ml, respectively. Moreover, PF could significantly prevent the biofilm formation of E. faecalis at the concentration of 1 × MIC. Furthermore, PF significantly eradicated 24 h pre‐formed biofilms of E. faecalis in a dose‐dependent manner, with a concentration range of 1 × MIC to 8 × MIC. Here, through the checkerboard method with other tested conventional antibiotics, we also determined that gentamycin, penicillin G, and amikacin showed partial synergistic antibacterial effects with PF. Also, PF showed almost no hemolysis on human erythrocytes. In a mouse peritonitis model, a single dose of 20 mg/kg of PF treatment could significantly reduce the bacterial colonization in the liver (~5‐fold reduction) and spleen (~3‐fold reduction). In conclusion, these findings indicated that after structural optimization, PF has the potential as a new antibacterial agent against E. faecalis.

Evaluation of Antimicrobial Activity of Buforin I and Nisin and the Synergistic Effect of Their Combination as a Novel Antimicrobial Preservative

One of the most effective methods for increasing the antimicrobial activity of a substance is to combine it with one or more other antimicrobial agents. The aim of the present study was to evaluate the antimicrobial effect of buforin I and nisin alone and investigate the synergistic action of these compounds against the most important food spoilage microorganisms in clouding B. subtilis, S. epidermidis, L. innocua, E. coli, S. Enteritidis, A. oryzae, R. glutinis and G. candidum. The results of MIC and MBC/MFC examinations showed that buforin I had higher antimicrobial activity than nisin on all the microbial strains used in this study (p≤0.5). E.coli was the most resistant to both antimicrobial agents, while Listeria innocua and Staphylococcus epidermidis were the most sensitive to nisin and buforin I, respectively. The results of synergistic interaction between buforin I and nisin indicated that the combination of buforin I and nisin on B. subtilis, S. epidermidis and A. oryzae showed synergistic effect, while it had no effect on S. Enteritidis and Geotrichum candidum. The combination of buforin I and nisin showed partial synergistic effect on Listeria innocua, Escherichia coli, Rhodotorula glutinis. Assessment of viability of the microorganisms under the antimicrobial agents alone and in combination with each other at MICs and FICs indicated that use of these antimicrobial agents in combination enhances antimicrobial activity at lower concentrations of both agents. The present study investigated the antimicrobial properties of buforin I against food spoilage microorganisms for the first time and suggests that its use alone or in combination with nisin may provide a clear horizon for the application of antimicrobial peptides as natural preservatives. Thus, the combination of antimicrobial peptides and traditional antimicrobial food preservative could be a promising option for the prevention of contamination, spoilage, and infestation of food and beverage products.

Synergistic Effects from Combination of Cryptotanshinone and Fosfomycin Against Fosfomycin-Susceptible and Fosfomycin-Resistant Staphylococcus aureus.

PurposeFosfomycin is now widely used to treat methicillin-resistant S. aureus due to its unique antibacterial activity. However, fosfomycin-resistant S. aureus has rapidly emerged, it is urgent to find new treatments to eliminate fosfomycin-resistant S. aureus infection. The purpose of this study was to analyze the activity of cryptanshinone, a traditional Chinese medicine monomer, in combination with fosfomycin against fosfomycin-sensitive S. aureus (FSSA) and fosfomycin-resistant S. aureus (FRSA).MethodsThe MICs of fosfomycin and/or cryptanshinone were determined by agar dilution assay and checkerboard microdilution assay. Furthermore, synergistic effects from fosfomycin and/or cryptanshinone were analyzed by the time-kill assay in vitro.ResultsThe combination of fosfomycin and cryptotanshinone had a synergistic effect on most (71.43%) of the FRSA and had a partial (28.57%) synergistic effect on a small part. In addition, time sterilization curve verified synergistic activity between cryptanshinone and fosfomycin against FSSA and FRSA, especially when fosfomycin was added for a second time.ConclusionThese data suggest that cryptanshinone combined with fosfomycin could be a novel treatment for FRSA and provide a new direction for the treatment of bacterial infections in the future.