Table 2.
Liposomal formulations developed for MDR pathogens.
| Pathogen | Emerging Resistance Patterns | Formulations Developed | Effect | Ref. | |
|---|---|---|---|---|---|
| Active Compound | Lipid Composition | ||||
| Acinetobacter baumannii | Carbapenem Polymyxin |
Polymyxin B | Chitosan–DPPC:DSPE:Chol Chitosan–DPPC:DSPE:Chol with USMB (DPPC:DSPE:Chol) |
The combination of the two systems revealed an antibacterial synergetic effect that could almost eliminate the biofilm-producing bacterium. | [106] |
| Fusidic acid | DOPE:DPPC:CHEMS DPPC:Chol |
An increased antibacterial effect of fusogenic liposomes (DOPE:DPPC:CHEMS) against clinical isolates in comparison to non-fusogenic formulation (DPPC:Chol) was observed (MICs of 37.5–300.0 µg/mL versus >833.0 µg/mL). Free fusidic acid did not present antibacterial effect against Gram-negative bacteria. | [107] | ||
| Vancomycin | DOPE:DPPC:CHEMS DPPC:Chol |
Fusogenic liposomes (DOPE:DPPC:CHEMS) displayed MICs of 6–12.5 µg/mL against clinical isolates, while free vancomycin and non-fusogenic formulation (DPPC:Chol) showed no antibacterial activity. | [17] | ||
| Polymyxin B | DPPC:Chol POPC:Chol |
Higher incorporation parameters for DPPC:Chol were achieved. MIC was 16-fold lower for liposomal formulation than for free antibiotic. | [100] | ||
| Pseudomonas aeruginosa | Carbapenem | Amikacin Gentamicin Tobramycin |
DPPC:Chol | With liposomal formulations, MICs have been maintained or reduced against all tested clinical isolates, for all antibiotics incorporated in relation to respective free antibiotics (MICs reductions were antibiotic- and strain-dependent: amikacin, 2–64-fold; gentamicin, 2–64-fold; tobramycin, 1–128-fold). | [92] |
| Polymyxin B | DPPC:Chol POPC:Chol |
Higher incorporation parameters for DPPC:Chol were achieved. MICs against clinical isolates were 4–32-fold lower for liposomal formulation in relation to free antibiotic. Liposomal formulation promoted the antibiotic penetration into a resistant strain in higher extent than free form. | [100] | ||
| Gentamicin | DMPC:Chol | MICs against clinical isolates and a laboratory strain were 2–16- and 4-fold lower, respectively, for liposomal gentamicin in comparison with free form. Time–kill values of liposomal formulation were equivalent to the free antibiotic, for the laboratory strain and one clinical isolate, while for the other clinical isolate the bactericidal effect was achieved at 4× MIC for liposomal formulation and free gentamicin, after 6 and 24 h, respectively. | [108] | ||
| Norfloxacin | PCT1–EPC:Chol:α tocopherol PCT2–EPC:Chol:α tocopherol |
An increased antibacterial effect against a multi-resistant strain for both formulations in comparison with free antibiotic was achieved (MIC of 3.2 µg/mL versus >30.0 µg/mL). No toxic effects were observed for any of the formulations, evaluated through an in vivo embryo chicken model. | [109] | ||
| Ofloxacin | DMPC:Chol:DP DMPC:Chol:DPPS DMPC:Chol:DPPE DMPC:Chol:DPPA |
After a susceptibility screening against reference strains of all developed formulations, DMPC:Chol:DP and DMPC:Chol:DPPS were chosen for further studies. An increased antibacterial effect against clinical isolates resistant to quinolones, mainly with DMPC:Chol:DP formulations was observed, resulting in MICs of 2–4-fold lower than free antibiotic. Higher intracellular antibiotic concentrations were obtained for both strains tested, when antibiotic was loaded in DMPC:Chol:DP. | [110] | ||
| Enterobacteriacea | Carbapenem ESBL+ Fluoroquinolones |
Cefepime | EPC:Chol EPC:Chol:12NBr DOPE:12NBr |
The formulation EPC:Chol:12NBr demonstrated higher incorporation parameters and, thus, was used for antibacterial study. Cefepime-loaded liposomes presented similar antibacterial activity to its free form, against an E. coli strain. | [111] |
| Azithromycin | EPC:EPG: EPC:HSPC-3 EPC:EPG:HSPC-3 EPC:Pg EPC:EPG:Pg EPC:SLPC:-80:Pg EPC:EPG:SLPC-80:Pg |
Liposomes incorporation parameters and stability assays promoted the selection of EPC:HSPC-3, EPC:Pg and EPC:SLPC:-80:Pg formulations for further experiments. MIC50 for all strains tested, were similar for liposomal formulations and for free antibiotic, while against bacteria in biofilm form the activity was lipid composition-dependent. Antibiotic-loaded EPC:EPG:HSPC-3 demonstrated the lower MBIC50 against the E. coli k-12 strain (8-fold lower in relation to free antibiotic). | [112] | ||
| Ofloxacin | DMPC:Chol:DP DMPC:Chol:DPPS DMPC:Chol:DPPE DMPC:Chol:DPPA |
After a susceptibility screening against reference strains of all developed formulations, DMPC:Chol:DP and DMPC:Chol:DPPS were chosen for further studies. MICs against E. coli clinical isolates were 4-fold lower for both formulations in relation to free antibiotic. Higher intracellular antibiotic concentrations were achieved when antibiotic was loaded in DMPC:Chol:DP. | [110] | ||
| Norfloxacin | PCT1–EPC:Chol:α tocopherol PCT2–EPC:Chol:α tocopherol |
An increased antibacterial effect against an E. coli strain, mainly with PCT1–EPC:Chol:α tocopherol formulation was observed, resulting in a MIC 9-fold lower than free antibiotic. In case of Salmonella strains, PCT2–EPC:Chol:α tocopherol presented the highest antibacterial effect with MICs of 2–17- and 16–42-fold lower than the other formulation and free antibiotic, respectively. No toxic effects were observed for any of the formulations, evaluated though an in vivo embryo chicken model. | [109] | ||
| Polymyxin B | DPPC:Chol POPC:Chol |
Higher incorporation parameters for DPPC:Chol were achieved, thus further studies were conducted with this formulation. MICs against E. coli and K. pneumoniae were 8–16- and 16-fold, respectively, for the liposomal formulation in comparison with free polymyxin B. | [100] | ||
| Ciprofloxacin | DPPC:Chol DSPC:Chol SM:Chol |
The SM:Chol formulation presented higher circulation lifetime than the remaining formulations. In this way, the efficacy of antibiotic-loaded SM:Chol was evaluated in a Salmonella typhimurium infection model, resulting in viable bacteria 103–104-fold lower in the livers and spleens of infected mice than the free antibiotic. | [113] | ||
| Staphylococcus aureus | Methicillin Vancomycin |
Ofloxacin | DMPC:Chol:DP DMPC:Chol:DPPS DMPC:Chol:DPPE DMPC:Chol:DPPA |
After a susceptibility screening against reference strains of all developed formulations, DMPC:Chol:DP and DMPC:Chol:DPPS were chosen for further studies. An increased antibacterial effect against S. aureus clinical isolates, mainly for DMPC:Chol:DPPS, was observed, with values 3- and 4-fold lower than free antibiotic. | [110] |
| Piperacillin | PC:Chol | Antibiotic incorporated in liposomes inhibited 3-fold higher a S. aureus clinical isolate growth, than its free form. Experiments using exogenous staphylococcal β-lactamase demonstrated that the liposomal formulation promoted the highest degree of protection against hydrolysis by staphylococcal β-lactamase. | [101] | ||
| Vancomycin | DSPC:DcP:Chol DSPC:DMPG:Chol |
MICs and MBCs against MRSA strains were 2–4- and 4-fold lower, respectively, for both formulations in relation to free antibiotic. The DSPC:DcP:Chol formulation showed the highest efficacy. In a systemic MRSA murine model, the liposomal formulation displayed a higher therapeutic effect, improving kidney clearance by 1-log in comparison with free antibiotic. | [69] | ||
| Vancomycin | DSPC:Chol DSPC:Chol:DSPE-PEG |
At the highest antibiotic concentration tested, DSPC:Chol formulation (non-pegylated liposomes) reduced the intracellular MRSA growth inside macrophages in approximately 2- and 3-fold higher in relation to pegylated formulation (DSPC:Chol:DSPE-PEG) and free antibiotic, respectively. | [103] | ||
| Azithromycin | Lipoid S75 Lipoid S75:SDCh Lipoid S75:Pg DPPC:DODAB |
MIC and MBIC were maintained or reduced for all formulations in relation to free antibiotic. The DPPC:DODAB formulation presented the highest antibacterial activity against both planktonic and biofilm forms of all clinical isolates tested. The MICs and MBICs were 8–32- and 16–32-fold lower than free azithromycin. Liposomal formulations demonstrated biocompatibility with keratinocytes and fibroblasts. | [114] | ||
| Methicillin | DOPE:DPPC:CHEMS: DSPE-PEG-MAL DOPE:DPPC:CHEMS:DSPE-PEG-Tat |
Antibacterial activity reductions were observed for both formulations, especially for DOPE:DPPC:CHEMS:DSPE-PEG-Tat formulation. MICs against a MRSA strain were 3.3, 5.0 and >5.0 µg/mL for DOPE:DPPC:CHEMS:DSPE-PEG-Tat, DOPE:DPPC:CHEMS:DSPE-PEG-MAL and free methicillin, respectively. | [115] | ||
|
Helicobacter
pylori |
Clarithromycin | Ampicillin Metronidazole |
DPPC:Chol:NBD-PC DPPC:Fuc-E4-Chol:Chol:NBD-PC Epikuron 170:Chol:NBD-PC Epikuron 170:Fuc-E4-Chol:Chol:NBD-PC |
Liposome–bacteria interaction results obtained by epifluorescence microscopy demonstrated to be strain- and lipid composition-dependent. Formulations without Epikuron 170 displayed superior interaction levels in both strains tested. However, DPPC:Fuc-E4-Chol:Chol:NBD-PC showed the highest interaction levels in the strain that express the babA2 gene (H. pylori 17875), due to the specifically link between the BabA2 protein and the fucose at the surface of liposomes. | [116] |
| Amoxicillin | LC:Chol:DDAB PCT-LC:Chol:DDAB |
Although both formulations presented similar antibacterial effect, the experimental assays developed in this study evidenced a specific interaction of PCT-coating liposomes with mucins and surface structures of bacteria. | [117] | ||
| Campylobacter | Fluoroquinolones | Norfloxacin | PCT1–EPC:Chol:α tocoferol PCT2–EPC:Chol:α tocoferol |
An increased antibacterial activity against a Campylobacter jejuni strain, mainly with PCT–EPC:Chol:α tocoferol formulation was observed. MIC was 10-fold lower than free antibiotic. No toxic effects were observed for any of the formulations, evaluated in an in vivo embryo chicken model. | [109] |
| Streptococcus pneumoniae | Penicillin | Vancomycin | DOPE:DPPC:CHEMS: DSPE-PEG-MAL DOPE:DPPC:CHEMS:DSPE-PEG-Tat |
MICs were approximately 2-fold lower for both formulations than respective free antibiotic. For the lowest concentrations tested (0.6 µg/mL) the formulation. DOPE:DPPC:CHEMS:DSPE-PEG-Tat displayed more favorable results, with a reduction of viable bacteria of approximately 1- and 2-fold in relation to the other formulation and to free vancomycin, respectively. | [115] |
DPPC, dipalmitoyl phosphatidyl choline; DSPE, distearoyl phosphatidyl choline; Chol, cholesterol; DOPE, dioleoyl phosphatidyl ethanolamine; CHEMS, cholesteryl hemisuccinate; POPC, palmitoyloleoyl phosphatidyl choline; DMPC, dimyristoyl phosphatidyl choline; EPC, egg phosphatidyl choline; PCT, pectin from apple; PCT1, pectin from apple, found in the aqueous phase that surrounds the liposomes; PCT2, pectin from apple, distributed in the water phase inside and outside the liposomes; DPPS, dipalmitoyl phosphatidyl serine; DP, dihexadecyl hydrogen phosphate; DPPE, dipalmitoyl phosphatidyl ethanolamine; DPPA, dipalmitoyl phosphatidic acid; 12NBr, N,N,N-triethyl-N-(12-naphthoxydodecyl)ammonium surfactant; EPG, egg phosphatidyl glycerol; HSPC-3, hydrogenated soybean phosphatidyl choline; SLPC-80, monoacyl soybean phosphatidyl choline; PEG, propylene glycol; PC, soybean phosphatidyl choline; DSPC, distearoyl phosphatidyl choline; SM, Egg sphingomyelin; DcP, dicethyl phosphate; DMPG, dimyristoyl phosphatidyl glycerol; DSPE-PEG, distearoyl phosphatidyl ethanolamine covalently linked to poly(ethylene glycol) 2000; Lipoid S75, soybean lecithin containing 75% phosphatidyl choline; SDCh, sodium deoxycholate; DODAB, dioctadecyldimethyl ammonium bromide; DSPE-PEG-MAL, distearoyl phosphatidyl ethanolamine covalently linked to poly(ethylene glycol) 2000 linked to maleimide; Tat, cell penetrating peptide (Cys-Tyr-Gly-Arg-Lys-Lys-Arg-Arg-Gln-Arg- Arg-Arg-NH2); NBD-PC, fluorescent nitrobenzoxa diazolyl label linked to phosphatidylcholine; Fuc-E4-Chol, Cholesteryl tetraethylene glycol fucose; Epikuron 170, phosphatidyl choline > 72%, phosphatidyl ethanol amine > 10%, phosphatidyl inositol < 3%, lyso phosphatidyl choline < 4% and free fatty acids 10%; LC, lecithin; DDAB, di-dodecyldimethylammonium bromide; MBIC, minimum biofilm inhibitory concentration; MIC, minimum inhibitory concentration; MIC50, minimum inhibitory concentration that inhibited bacterial growth by 50%; USMB, ultrasound microbubbles.