Antimicrobial Synergistic Effects of Linezolid and Vancomycin with a Small Synthesized 2-Mercaptobenzothiazole Derivative: A Challenge for MRSA Solving.

Methicillin-resistant Staphylococcus aureus (MRSA) emerged as one of the leading causes of persistent human infections and makes it difficult to treat bacteremia, especially with biofilm formation. In this work, we investigated the in vitro synergism between Linezolid (LNZ) and Vancomycin (VAN) with a 2-mercaptobenzothiazole derivative, resulting in a new small-molecule antibacterial compound that we named BTZ2e, on several clinical MRSA, MRSE (methicillin-resistant Staphylococcus epidermidis) and control (ATCC Collection) strains in their planktonic and biofilms cultures. The broth microdilution method evaluated the susceptibility of planktonic cells to each investigated antibiotic combined with BTZ2e. The biofilm's metabolic activity was studied with the XTT reduction assay. As a result, in this study, biofilm formation was significantly suppressed by the BTZ2e treatment. In terms of minimal biofilm inhibitory concentration (MBIC), BTZ2e revealed an MBIC50 value of 32 µg/mL against methicillin-susceptible S. aureus (MSSA) and 16 µg/mL against methicillin-resistant S. aureus ATCC 43300 biofilms. An inhibition range of 32 µg/mL and 256 µg/mL was registered for the clinical isolates. Interestingly, a synergistic effect (FICI ≤ 0.5) was encountered for the combination of BTZ2e with LNZ and VAN on several planktonic and sessile strains. In particular, the best result against planktonic cells emerged as a result of the synergistic association between LNZ and BTZ2e, while against sessile cells, the best synergistic association resulted from VAN and BTZ2e. The consistent results indicate BTZ2e as a promising adjuvant against multi-resistant strains such as MRSA and MRSE.

Biological evaluation of hyperforin and its hydrogenated analogue on bacterial growth and biofilm production.

Bacterial biofilms are organized communities of microorganisms, embedded in a self-produced matrix, growing on a biotic surface and resistant to many antimicrobial agents when associated with a medical device. These biofilms require the development of new strategies for the prevention and treatment of infectious disease, including the potential use of natural products. One interesting natural product example is Hypericum, a plant genus that contains species known to have antimicrobial properties. The major constituent of Hypericum perforatum is an unstable compound named hyperforin (1); for this reason it was not believed to play a significant role in the pharmacological effects. In this investigation a hydrogenated hyperforin analogue (2) was tested on several ATCC and clinical isolate strains, in their planktonic and biofilm form (Staphylococcus aureus, MRSA, and Enterococcus faecalis). Compound 2 was effective against planktonic and biofilm cultures, probably due to higher stability, showing the percentage of cells killed in the range from 45% to 52%. These results are noteworthy from the point of view of future development of these polyprenylated phloroglucinols as potential antibiotics.

Effect of Methyl-ß-Cyclodextrin on the antimicrobial activity of a new series of poorly water-soluble benzothiazoles.

The antibacterial activity of the S-unsubstituted- and S-benzyl-substituted-2-mercapto-benzothiazoles 1-4 has been evaluated after complexation with Methyl-ß-Cyclodextrin (Me-ß-CD) or incorporation in solid dispersions based on Pluronic® F-127 and compared with that of the pure compounds. This with the aim to gain further insights on the possible mechanism(s) involved in the CD-mediated enhancement of antimicrobial effectiveness, a promising methodology to overcome the microbial resistance issue. Together with Differential Scanning Calorimetry, FT-IR spectroscopy and X-ray Powder Diffraction investigations, a molecular modeling study focused on compounds 2 and 4 showed that the S-unsubstituted compound 2/Me-ß-CD complex should be more stable than S-benzyl-substituted 4/Me-ß-CD. Only for 1/Me-ß-CD or, particularly, 2/Me-ß-CD complexes, the antibacterial effectiveness was enhanced in the presence of selected bacterial strains. The results herein presented support the mechanisms focusing on the interactions of the bacterial membrane with CD complexes more than those focusing on the improvement of dissolution properties consequent to CD complexation.

In vitro synergy testing of anidulafungin with fluconazole, tioconazole, 5-flucytosine and amphotericin B against some Candida spp.

In this paper the authors investigated a synergistic antimycotic effect between four antifungal drugs Amphotericin B, Fluconazole, Tioconazole, and Flucytosine individually combined with Anidulafungin compound. This latter is considered a drug of choice in the treatment of fungal infections; it has good activity both in vitro and in vivo against yeasts and moulds, as Candida and Aspergillus. The goal of this study was to evaluate the in vitro interaction of Anidulafungin in the synergic combinations with previous reported drugs against 12 Candida strains according to CLSI M27-A3 protocol. A synergistic interaction was observed against the most antifungal strains; in particular an increasing of the antimycotic efficacy was obtained from the association between Anidulafungin and Amphotericin B or Fluconazole (Mixture 4:6). In contrast the association Tioconazole/Anidulafungin was less effective on fungal species growth. The antimycotics MIC reduction values were more evident against some strains as C. glabrata, C. krusei, C. tropicalis and C. parapsilosis.