Aims: Carbapenem-resistant Acinetobacter baumannii represents a public health problem, and the search for new antibacterial drugs has become a priority. Here, we investigate the antibacterial activity of biogenic silver nanoparticles (Bio-AgNPs) synthesized by Fusarium oxysporum, used alone or in combination with polymyxin B against carbapenem-resistant A. baumannii.
Methods and Results:In this study, ATCC ® 19606 ™ strain and four carbapenemresistant A. baumannii strains were used. The antibacterial activity of Bio-AgNPs and its synergism with polymyxin B were determined using broth microdilution, checkboard methods and time-kill assays. The integrity of the bacterial cell membrane was monitored by protein leakage assay. In addition, the cytotoxicity in the VERO mammalian cell line was also evaluated, and the selectivity index was calculated. Bio-AgNPs have an antibacterial activity with MIC and MBC ranging from 0.460 to 1.870 µg/ml. The combination of polymyxin B and Bio-AgNPs presents synergy against four of the five strains tested and additivity against one strain in the checkerboard assay. Considering the time of cell death, Bio-AgNPs killed all carbapenem-resistant isolates and ATCC ® 19606 ™ within 1 h. When combined, Bio-AgNPs presented 16-fold reduction of the polymyxin B MIC and showed a decrease in terms of viable A. baumannii cells in 4 h of treatment, with synergic and additive effects. Protein leakage was observed with increasing concentrations for Bio-AgNPs treatments. Additionally, Bio-AgNP and polymyxin B showed dose-dependent cytotoxicity against mammalian VERO cells and combined the cytotoxicity which was significantly reduced and presented a greater pharmacological safety.
Conclusions:The results presented here indicate that Bio-AgNPs in combination with polymyxin B could represent a good alternative in the treatment of carbapenemresistant A. baumannii.
Significance and Impact of Study:This study demonstrates the synergic effect between Bio-AgNPs and polymyxin B on carbapenem-resistant A. baumannii strains.
Sub-Antarctic macroalgae can be a feasible source of innumerous bioactive compounds that can display important biological activities. In this sense, the aims of this work were to evaluate the chemical composition, antimicrobial activity and cytotoxic potential of n-hexane extracts from sub-Antarctic seaweed Mazzaella laminarioides (Bory) Fredericq at distinct development phases. Results showed that extracts were constituted of as much as 65 distinct compounds that could be distributed mainly among hydrocarbons, fatty acids, sterols and fatty alcohols. Generally, there were significant differences (P < 0.05) in the concentrations of compounds comparing distinct development phases. Antimicrobial evaluation indicated that n-hexane extracts of cystocarpic and tetrasporophytic phase of M. laminarioides inhibited the growth of most organisms tested, reaching minimum inhibitory concentrations of 0.0312 mg mL −1 against Enterococcus faecalis (Andrewes and Horder) and 0.25 mg mL −1 against Acinetobacter baumannii (Bouvet and Grimont). Cytotoxic evaluation of extracts showed no toxicity to normal cells at concentrations below 1 mg mL −1. Therefore, M. laminarioides from the sub-Antarctic region had antimicrobial potential that could be explored on further commercial applications.
Respiratory bacterial infections are a cause of morbidity and mortality worldwide; most of these infections respond well to antibiotic therapies, although several factors cause bacteria to become increasingly resistant, leading to a concerning public health problem. Hence, researchers have sought new antibiotics that can replace or enhance the effectiveness of existing drugs. Given this scenario, this review is based on original articles from the PubMed and Science Direct databases published from May 2015 to February 2022 that reported the potential of essential oils, extracts, and formulations containing Myrtaceae and nanoparticles against bacteria that affect the respiratory system.
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