Efficacy of Zoliflodacin, a Spiropyrimidinetrione Antibiotic, Against Gram-Negative Pathogens.

Zoliflodacin is a spiropyrimidinetrione antibiotic that acts by binding to the GyrB part of the DNA gyrase enzyme in bacteria. Its effectiveness for the treatment of Neisseria gonorrhoeae infections has been investigated extensively. Since antibiotic resistance has been reached an alarming rate worldwide, researches on new antimicrobials are considered a priority, especially in the treatment of multidrug-resistant Gram-negative bacteria, such as Klebsiella pneumonia. The aim of this study is to test and compare the effectiveness of zoliflodacin with some traditional antibiotics which are frequently preferred in the treatment of Gram-negative pathogens, primarily K. pneumonia. Additionally, its ability to prevent biofilm formation has also been determined. The minimum inhibitory concentration (MIC) values of zoliflodacin along with levofloxacin, meropenem, gentamicin, ampicillin/sulbactam and ceftazidime/avibactam were evaluated by broth microdilution method against 15 Gram-negative clinical isolates and three standard strains. Also, the synergism potential of zoliflodacin with other antibiotics was evaluated by the checkerboard method against standard strains of K. pneumonia, Pseudomonas aeruginosa, and Acinetobacter baumannii. In addition, the inhibitory effects of zoliflodacin on biofilm formation of standard strains were determined. Zoliflodacin MICs were found to be in the range of 2-64 µg/mL, and its combination with meropenem and ampicillin/sulbactam was found to be synergistic, especially against A. baumannii. Zoliflodacin significantly inhibited A. baumannii biofilm at sub-MIC values. These results indicated that zoliflodacin can be considered as an alternative against infections of Gram-negative pathogens, alone or in combination.

Antibiotic adjuvant activities of quorum sensing signal molecules DSF and BDSF against mature biofilms of Staphylococci.

Among promising antibiofilm compounds, quorum-sensing (QS) molecules that regulate biological processes such as biofilm formation and intra- or interspecies communication appear to be good candidates. The invitro antibiotic-adjuvant effects of QS molecules diffusible signal factor (DSF) and B. cenocepacia producing-DSF (BDSF) were investigated against mature Staphylococcal biofilms. Broth microdilution methods were used for the determinations of MIC, MBC, MBIC, and MBEC, and bactericidal activities were determined by TKC method. The lowest MICs were obtained with ciprofloxacin and gentamicin, and MBECs with ciprofloxacin. DSF and BDSF at 0.5 µM decreased the MICs as 2-8, and 2-32 fold, respectively. In TKC studies, -cidal activities were achieved by BDSF + gentamycin, or ciprofloxacin, and DSF + daptomycin, vancomycin, meropenem or gentamycin combinations. Synergistic effects were generally obtained with BDSF + gentamicin combinations, followed by DSF + daptomycin against most S. aureus; while BDSF + gentamicin or ciprofloxacin, and DSF + vancomycin or meropenem were synergist against some S. epidermidis biofilms. Also, the antagonist effects were observed with BDSF + meropenem or ciprofloxacin against each MSSE and MSSA. It is estimated that these QS molecules, although it was strain dependent, generally enhanced the antibiotic activity, and would be a new and effective treatment strategy for biofilm control, either alone or as an antibiotic adjuvant.

Antimicrobial Activity of Ceragenins against Vancomycin-Susceptible and -Resistant Enterococcus spp.

Ceragenins (CSAs) are a new class of antimicrobial agents designed to mimic the activities of endogenous antimicrobial peptides. In this study, the antibacterial activities of various ceragenins (CSA-13, CSA-44, CSA-90, CSA-131, CSA-138, CSA-142, and CSA-192), linezolid, and daptomycin were assessed against 50 non-repeated Enterococcus spp. (17 of them vancomycin-resistant Enterococcus-VRE) isolated from various clinical specimens. Among the ceragenins evaluated, the MIC50 and MIC90 values of CSA-44 and CSA-192 were the lowest (2 and 4 µg/mL, respectively), and further studies were continued with these two ceragenins. Potential interactions between CSA-44 or CSA-192 and linezolid were tested and synergistic interactions were seen with the CSA-192-linezolid combination against three Enterococcus spp., one of them VRE. The effects of CSA-44 and CSA-192 on the MIC values of vancomycin were also investigated, and the largest MIC change was seen in the vancomycin-CSA-192 combination. The in vivo effects of CSA-44 and CSA-192 were evaluated in a Caenorhabditis elegans model system. Compared to no treatment, increased survival was observed with C. elegans when treated with ceragenins. In conclusion, CSA-44 and CSA-192 appear to be good candidates (alone or in combination) for the treatment of enterococcal infections, including those from VRE.

Efficacy of Ceragenins Alone and in Combinations with Antibiotics Against Multidrug-Resistant Gram Negative Pathogens from Bloodstream Infections.

Ceragenins (CSAs) that mimic the activities of antimicrobial peptides may be new options for the treatment of infections caused by multidrug-resistant pathogens. This study investigated the antibacterial activities of eight different ceragenins against MDR pathogens and the synergistic effects of some ceragenins in combinations with antibiotics (meropenem-MEM, ceftazidime + avibactam-CZA, tigecycline-TIG). A disc diffusion method was used for antibiotic susceptibility tests, a broth microdilution, and checkerboard methods were used to detect minimum inhibitory concentrations (MICs) and the effects of combinations, respectively. While MIC90 values CSA-13, CSA-44, CSA-131 against Klebsiella pneumoniae isolates had similar effect with MEM (8 µg/ml); CSA-13, CSA-44, CSA-131, CSA-138, and CSA-144 had better activity than MEM against Acinetobacter baumannii and Pseudomonas aeruginosa isolates. In particular, CSA-44 and CSA-131 were effective against A. baumannii and P. aeruginosa isolates which resistant to both COL and MEM. CSA-44+MEM and CSA-131+CZA combinations showed synergistic activity against most (70%) of MDR- E. coli isolates. Although TIG is known to have weak activity in nonfermentative bacteria, CSA-44+TIG combination showed synergistic activity against two (17%) of the A. baumanni isolates. In addition, CSA-44+TIG and CSA-131+TIG combinations showed additive effects against all P. aeruginosa isolates. Antagonism was not detected in any of the combinations. CSA-44 and CSA-131 alone/or in combinations with MEM or CZA can be considered as new alternative treatments in serious infections caused by MDR pathogens.

In vitro activities of antibiotic combinations against mature biofilms of ventilator-associated pneumonia isolates.

Background: The authors aimed to determine the efficacy of frequently used antibiotics, alone or in combination, against biofilms of ventilator-associated pneumonia isolates. Materials & methods: The authors determined the MICs, minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of meropenem, ciprofloxacin and colistin as well as their combinations against planktonic forms and biofilms of Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii clinical isolates. Results: Generally, the minimum biofilm inhibitory concentrations and minimum biofilm eradication concentrations of the antibiotics were 1000-fold higher than their MICs, and synergy was provided by different concentrations of meropenem-colistin and meropenem-ciprofloxacin combinations with checkerboard and time-kill curve methods. Conclusion: The combination of meropenem and ciprofloxacin seems to be a good candidate for the treatment of biofilm-associated infections; none of the concentrations obtained as a result of the synergy test were clinically significant.

Preparation and evaluation of a propolis ointment for skin nourishing and healing.

Propolis is a resinous substance containing aromatic acids, esters, volatile compounds, hydrocarbons, steroids, enzymes, flavonoids, vitamins and minerals. In this direction it has nutrient, antibacterial and antioxidant properties due to its complex structure and content. In this study it was aimed to prepare a propolis ointment with a base of occlusive and emollient properties for nourishing and healing of skin damaged by environmental effects. Six formulations were prepared by using vaseline, lanolin, glycerine and different types of crude propolis. According to physical examinations only the ointment formulations prepared with ethanolic propolis extracts at two different concentrations were found as successful. Successful formulation including 1:5 propolis: Ethanol extract was evaluated by physical controls, mechanic tests, antimicrobial tests and stability evaluation. Results showed that prepared propolis ointment has a creamy yellow colour with an acceptable odour, homogeny and a good spreadability texture and has a good stability at 40oC and 25oC and for 2 and 3 months respectively. And it presented mild antibacterial effects on E. coli and S. aureus strains, which was acceptable for a frequent use for cosmetic purposes. As a conclusion prepared propolis ointment can be a good candidate for a cosmetic ointment for skin nutrition and healing purposes.

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 âˆ¼ 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.

Voriconazole incorporated nanofiber formulations for topical application: preparation, characterization and antifungal activity studies against Candida species.

In this study, voriconazole (VCZ) incorporated polyvinyl alcohol/sodium alginate electrospun nanofibers were produced and, then crosslinked with glutaraldehyde for topical antifungal treatment. The nanofibers were characterized in terms of fiber size, surface morphology, and compatibility between drug-polymer and polymer-polymer using scanning electron microscopy, atomic force microscopy, attenuated total reflection-Fourier transform infrared spectroscopy, and high pressure liquid chromatography. After optimization studies, in vitro drug release, skin penetration, and deposition studies were performed using Franz diffusion cells. Antifungal activities of the nanofiber formulations against Candida albicans, Candida tropicalis, and Candida parapysilosis strains were evaluated using susceptibility test and subsequently time-kill study was performed against C. albicans. The cytotoxicity study was performed using 4-succinate dehydrogenase viability assay on mouse fibroblast cell line. The release rate of VCZ from crosslinked nanofibers was slower than that of non-crosslinked nanofibers and Higuchi kinetic model best fitted to the in vitro release data of both of formulations. VCZ deposited in deeper skin layers from nanofiber formulations was higher than that of the control formulation (VCZ solution in propylene glycol (1% (w/v)). According to the susceptibility and time-kill studies, all of the nanofiber formulations showed antifungal activity against C. albicans with confirming no cytotoxicity on mouse fibroblast cells.

In vitro activities of antifungals alone and in combination with tigecycline against Candida albicans biofilms.

BACKGROUND: Candida may form biofilms, which are thought to underlie the most recalcitrant infections. METHODS: In this study, activities of antifungal agents alone and in combination with tigecycline against planktonic cells and mature and developing biofilms of Candida albicans isolates were evaluated. RESULTS: Amphotericin B and echinocandins were found to be the most effective agents against mature biofilms, whereas the least effective agent was fluconazole. Furthermore, the most effective anti-fungal monotherapies against biofilm formation were amphotericin B and anidulafungin, and the least effective monotherapy was itraconazole. The combination of tigecycline and amphotericin B yielded synergistic effects, whereas combinations containing itraconazole yielded antagonist effects against planktonic cells. The combination of tigecycline and caspofungin exhibited maximum efficacy against mature biofilms, whereas combinations containing itraconazole exhibited minimal effects. Combinations of tigecycline with amphotericin B or anidulafungin were highly effective against C. albicans biofilm formation. DISCUSSION: In summary, tigecycline was highly active against C. albicans particularly when combined with amphotericin B and echinocandins.

Antimicrobial activities of widely consumed herbal teas, alone or in combination with antibiotics: an in vitro study.

BACKGROUND: Because of increasing antibiotic resistance, herbal teas are the most popular natural alternatives for the treatment of infectious diseases, and are currently gaining more importance. We examined the antimicrobial activities of 31 herbal teas both alone and in combination with antibiotics or antifungals against some standard and clinical isolates of Pseudomonas aeruginosa, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae, Enterococcus faecalis, methicillin susceptible/resistant Staphylococcus aureus and Candida albicans. METHODS: The antimicrobial activities of the teas were determined by using the disk diffusion and microbroth dilution methods, and the combination studies were examined by using the microbroth checkerboard and the time killing curve methods. RESULTS: Rosehip, rosehip bag, pomegranate blossom, thyme, wormwood, mint, echinacea bag, cinnamon, black, and green teas were active against most of the studied microorganisms. In the combination studies, we characterized all the expected effects (synergistic, additive, and antagonistic) between the teas and the antimicrobials. While synergy was observed more frequently between ampicillin, ampicillin-sulbactam, or nystatine, and the various tea combinations, most of the effects between the ciprofloxacin, erythromycin, cefuroxime, or amikacin and various tea combinations, particularly rosehip, rosehip bag, and pomegranate blossom teas, were antagonistic. The results of the time kill curve analyses showed that none of the herbal teas were bactericidal in their usage concentrations; however, in combination with antibiotics they showed some bactericidal effect. DISCUSSION: Some herbal teas, particularly rosehip and pomegranate blossom should be avoided because of their antagonistic interactions with some antibiotics during the course of antibiotic treatment or they should be consumed alone for their antimicrobial activities.

Antibacterial and anti-biofilm activities of melittin and colistin, alone and in combination with antibiotics against Gram-negative bacteria.

In vitro antibacterial and anti-biofilm activities of antimicrobial cationic peptides (AMPs) - melittin and colistin - both alone and in combination with antibiotics were evaluated against clinical isolates of Gram-negative bacteria. Minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) index were determined by the microbroth dilution and chequerboard techniques, respectively. The time-kill curve (TKC) method was used for determining the bactericidal activities of AMPs alone and in combination. Measurements of anti-biofilm activities were performed spectrophotometrically for both inhibition of attachment and 24-hour biofilm formation at MIC or subMIC. According to MIC90 values, the most active agents against Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae were colistin, imipenem and ciprofloxacin, respectively. In combination studies, synergistic effects were mostly seen with colistin-imipenem against E. coli and K. pneumoniae (50 and 54%, respectively), colistin-ciprofloxacin against P. aeruginosa (77%). In TKC studies, synergism was observed with almost all expected combinations, even more frequently than chequerboard method. All of the antimicrobial agents were able to inhibit attachment and 24-hour biofilm formation between 0-57% at 1/10 × MIC and 7-73% at 1 × or 1/10 × MIC, respectively. AMPs seem to be a good candidate for antimicrobial chemotherapy with their antibacterial and anti-biofilm activities as a single agent or in combination with antibiotics.

Inhibition and destruction of Pseudomonas aeruginosa biofilms by antibiotics and antimicrobial peptides.

Pseudomonas aeruginosa is one of the major nosocomial pathogen that can causes a wide variety of acute and chronic infections P. aeruginosa is a dreaded bacteria not just because of the high intrinsic and acquired antibiotic resistance rates but also the biofilm formation and production of multiple virulence factors. We investigated the in vitro activities of antibiotics (ceftazidime, tobramycin, ciprofloxacin, doripenem, piperacillin and colistin) and antimicrobial cationic peptides (AMPs; LL-37, CAMA: cecropin(1-7)-melittin A(2-9) amide, melittin, defensin and magainin-II) alone or in combination against biofilms of laboratory strain ATCC 27853 and 4 clinical strains of P. aeruginosa. The minimum inhibitory concentrations (MIC), minimum bactericidal concentration (MBC) and minimum biofilm eradication concentrations (MBEC) were determined by microbroth dilution technique. The MBEC values of antibiotics and AMPs were 80->5120 and 640->640mg/L, respectively. When combined with the LL-37 or CAMA at 1/10× MBEC, the MBEC values of antibiotics that active against biofilms, were decreased up to 8-fold. All of the antibiotics, and AMPs were able to inhibit the attachment of bacteria at the 1/10× MIC and biofilm formation at 1× or 1/10× MIC concentrations. Time killing curve studies showed 3-log10 killing against biofilms in 24h with almost all studied antibiotics and AMPs. Synergism were seen in most of the studied combinations especially CAMA/LL-37+ciprofloxacin against at least one or two strains' biofilms. Since biofilms are not affected the antibiotics at therapeutic concentrations, using a combination of antimicrobial agents including AMPs, or inhibition of biofilm formation by blocking the attachment of bacteria to surfaces might be alternative methods to fight with biofilm associated infections.

In vitro pharmacokinetics of antimicrobial cationic peptides alone and in combination with antibiotics against methicillin resistant Staphylococcus aureus biofilms.

Antibiotic therapy for methicillin-resistant Staphylococcus aureus (MRSA) infections is becoming more difficult in hospitals and communities because of strong biofilm-forming properties and multidrug resistance. Biofilm-associated MRSA is not affected by therapeutically achievable concentrations of antibiotics. Therefore, we investigated the in vitro pharmacokinetic activities of antimicrobial cationic peptides (AMPs; indolicidin, cecropin [1-7]-melittin A [2-9] amide [CAMA], and nisin), either alone or in combination with antibiotics (daptomycin, linezolid, teicoplanin, ciprofloxacin, and azithromycin), against standard and 2 clinically obtained MRSA biofilms. The minimum inhibitory concentrations (MIC) and minimum biofilm-eradication concentrations (MBEC) were determined by microbroth dilution technique. The time-kill curve (TKC) method was used to determine the bactericidal activities of the AMPs alone and in combination with the antibiotics against standard and clinically obtained MRSA biofilms. The MIC values of the AMPs and antibiotics ranged between 2 to 16 and 0.25 to 512 mg/L, and their MBEC values were 640 and 512 to 5120 mg/L, respectively. The TKC studies demonstrated that synergistic interactions occurred most frequently when using nisin+daptomycin/ciprofloxacin, indolicidin+teicoplanin, and CAMA+ciprofloxacin combinations. No antagonism was observed with any combination. AMPs appear to be good candidates for the treatment of MRSA biofilms, as they act as both enhancers of anti-biofilm activities and help to prevent or delay the emergence of resistance when used either alone or in combination with antibiotics.

In vitro activities of antibiotics and antimicrobial cationic peptides alone and in combination against methicillin-resistant Staphylococcus aureus biofilms.

Methicillin-resistant Staphylococcus aureus (MRSA) strains are most often found as hospital- and community-acquired infections. The danger of MRSA infections results from not only the emergence of multidrug resistance but also the occurrence of bacteria that form strong biofilms. We investigated the in vitro activities of antibiotics (daptomycin, linezolid, teichoplanine, azithromycin, and ciprofloxacin) and antimicrobial cationic peptides {AMPs; indolicidin, CAMA [cecropin (1-7)-melittin A (2-9) amide], and nisin} alone or in combination against MRSA ATCC 43300 biofilms. The MICs and minimum biofilm eradication concentrations (MBECs) were determined by the broth microdilution technique. Antibiotic and AMP combinations were assessed using the checkerboard technique. For MRSA planktonic cells, MICs of antibiotics and AMPs ranged between 0.125 and 512 and 8 and 16 mg/liter, respectively, and the MBEC values were between 512 and 5,120 and 640 mg/liter, respectively. With a fractional inhibitory concentration of ≤0.5 as the borderline, synergistic interactions against MRSA biofilms were frequent with almost all antibiotic-antibiotic and antibiotic-AMP combinations. Against planktonic cells, they generally had an additive effect. No antagonism was observed. All of the antibiotics, AMPs, and their combinations were able to inhibit the attachment of bacteria at 1/10 MIC and biofilm formation at 1× MIC. Biofilm-associated MRSA was not affected by therapeutically achievable concentrations of antimicrobial agents. Use of a combination of antimicrobial agents can provide a synergistic effect, which rapidly enhances antibiofilm activity and may help prevent or delay the emergence of resistance. AMPs seem to be good candidates for further investigations in the treatment of MRSA biofilms, alone or in combination with antibiotics.

In vitro activities of antimicrobial cationic peptides; melittin and nisin, alone or in combination with antibiotics against Gram-positive bacteria.

The In vitro activities of two antimicrobial cationic peptides, melittin and nisin alone and in combination with frequently used antibiotics (daptomycin, vancomycin, linezolid, ampicillin, and erythromycin), were assessed against clinical isolates of methicillin-susceptible Staphylococcus aureus, methicillin-resistant S. aureus and Enterococcus faecalis. Using the broth microdilution method, minimum inhibitory concentration (MIC) ranges of melittin and nisin against all strains were 2-8 µg/ml and 2-32 µg/ml respectively. In combination studies performed with the microdilution checkerboard method using a fractional inhibitory concentration index of ≤ 0.5 as borderline, synergistic interactions occurred more frequently with nisin-ampicillin combination against MSSA and nisin-daptomycin combination against E. faecalis strains. The results of the time-killing curve analysis demonstrated that the concentration dependent rapid bactericidal activity of nisin, and that synergism or early synergism was detected in most strains when nisin or melittin was used in combination with antibiotics even at concentrations of 0.5 × MIC.

Synthesis and biological activity of new 1,3-dioxolanes as potential antibacterial and antifungal compounds.

A series of new enantiomerically pure and racemic 1,3-dioxolanes 1-8 was synthesized in good yields and short reaction times by the reaction of salicylaldehyde with commercially available diols using a catalytic amount of Mont K10. Elemental analysis and spectroscopic characterization established the structure of all the newly synthesized compounds. These compounds were tested for their possible antibacterial and antifungal activity. Biological screening showed that all the tested compounds, except 1, show excellent antifungal activity against C. albicans, while most of the compounds have also shown significant antibacterial activity against S. aureus, S. epidermidis, E. faecalis and P. aeruginosa.

In vitro activities of nisin alone or in combination with vancomycin and ciprofloxacin against methicillin-resistant and methicillin-susceptible Staphylococcus aureus strains.

BACKGROUND: We investigated the in vitro activities of nisin alone or in combination with vancomycin and ciprofloxacin against methicillin-resistant (MRSA) and -susceptible Staphylococcus aureus (MSSA) strains. METHODS: The minimum inhibitory concentrations were determined by microbroth dilution technique. Antibiotic combinations were assessed using the checkerboard technique. The time-kill curve method was used for determining the bactericidal activity of nisin alone and in combination. RESULTS: For both MSSA and MRSA strains, the minimum inhibitory concentrations of nisin ranged between 4 and 16 mg/l. With a fractional inhibitory concentration of ≥0.5 as borderline, synergistic interactions were seen in three of five isolates with nisin-ciprofloxacin compared to two of five isolates with nisin-vancomycin combinations against both MSSA and MRSA. No antagonism was observed. The results of time-kill curve analysis demonstrated concentration-dependent rapid bactericidal activity of nisin and synergism almost in all strains when nisin was used in combination with ciprofloxacin, and early synergistic interactions in some of the strains when it was used in combination with vancomycin. CONCLUSION: Nisin seems to be a good candidate for further investigations in the treatment of Gram-positive bacteria, alone or in combination with antibiotics.