New trends in peptide-based anti-biofilm strategies: a review of recent achievements and bioinformatic approaches

Figures & data

Table 1. AMP sources and classes.

Source/type	Family	Structural features	Synthesis and localization	Spectrum of activity	Other characteristics
Mammals	Cathelicidins	• Gene encoded (Tomasinsig and Zanetti 2005) • 12–100 a.a. (Wang et al. 2011a) • Cathelin domain (highly conserved N-terminal region) (Bals and Wilson 2003; Tomasinsig and Zanetti 2005) • Peptides with little similarity besides their precursor protein (hCAP18) (Smet and Contreras 2005; Lai and Gallo 2009)	• Expressed in leukocytes (neutrophils, monocytes, NK cells, T and B cells), epithelial cells of the testis, skin, gastrointestinal and respiratory tracts (Bals and Wilson 2003; Smet and Contreras 2005)	• Bacteria • Fungi (Cirioni et al. 2006)	• Also produced by invertebrates, fish, birds, frogs and snakes (Cirioni et al. 2006; Lai and Gallo 2009)
Defensins	• 3.5-6 kDa (Smet and Contreras 2005) • 6 conserved cysteine residues, forming 3 disulfide bridges (Smet and Contreras 2005) • 50α-defensins and 90β-defensins (Lai and Gallo 2009) • 4α neutrophil defensins (HNP-1 to 4), 2α enteric defensins (HD-5 and H-6) and 4β epithelial defensins (hβD-1 to 4) ( http://peptidesaustralia.com/peptides-and-proteins-with-antimicrobial-activity/)	• Expressed in monocytes, macrophages, keratinocytes and epithelial cells of the respiratory, digestive, urinary and reproductive systems (Lai and Gallo 2009) • Stored in the neutrophils' granules and in Paneth cells (Lai and Gallo 2009)	• Bacteria • Fungi • Protozoans • Viruses (Cederlund et al. 2011)	• Antitumoral • Stimulate cell proliferation • Interferes with signal transduction pathways • Chemo-attract immune cells • Stimulate cytokine and adhesion molecules' expression
Histatins	• 3-4 kDa • Histidine-rich (7 histidine residues) • Linear structure (Oppenheim et al. 1988; Smet and Contreras 2005) • Histatin 5: random coil structure in aqueous solvents and α-helix structure in non-aqueous solvents (Raj et al. 1998)	• Present in human saliva (Oppenheim et al. 1988; Smet and Contreras 2005) • Produced and secreted by the submandibular, sublingual and parotid glands (Smet and Contreras 2005)	• Bacteria • Fungi (Oppenheim et al. 1988; Smet and Contreras 2005)	• Inhibit inflammatory cytokine induction from human fibroblasts • Inhibit host and bacterial enzymes implicated in periodontal disease • Metallopeptide-like properties
Amphibians	Dermaseptins	• α-helical • Amphipathic • Undergo coil-to-helix transition upon binding to lipid bilayers • Signature pattern of a conserved Trp residue at position 3 and an AA(A/G) KAAL(G/N)A consensus motif in the midregion (Nicolas and El Amri 2009)	• Produced by Phyllomedusa, Pachymedusa, Agalichnis and Hylomantis frogs (Nicolas and El Amri 2009; Zhang et al. 2010) • Synthesized and stored in the granular glands of the skin (Nicolas and El Amri 2009)	• Bacteria • Yeast • Protozoa • Mollicutes • Enveloped viruses (Nicolas and El Amri 2009)	• Antimalarial (Nicolas and El Amri 2009)
Phylloseptins	• 19–21 a.a. (1.7–2.1 kDa) • Highly conserved N-terminal region and C-terminal amidation • Amphiphilic (Leite et al. 2005; Zhang et al. 2010)	• Present in skin secretions of Phyllomedusa and Hylomantis frogs (Nicolas and El Amri 2009)	• Bacteria • Protozoans (Leite et al. 2005; Zhang et al. 2010)	–
Magainins	• 23 a.a. (Zairi et al. 2009) • α-helical (Zairi et al. 2009) • Also known as PGS (peptide glycine serine) (Giovannini et al. 1987; Zairi et al. 2009)	• Present in the skin of the African clawed frog Xenopus laevis (Zairi et al. 2009; Duclohier 2010)	• Bacteria • Fungi • Viruses (Zairi et al. 2009; Duclohier 2010)	• Facilitate wound closure and reduce inflammation (Sai et al. 1995; Duclohier 2010) • Spermicidal (Reddy et al. 1996) • Antitumoral (Duclohier 2010) • Act as dimmers via the toroidal model (Duclohier 2010)
Crustaceans	Tachyplesins	• 17 a.a. • Unique arginine α-amide at the COOH terminal end (Nakamura et al. 1988) • Disulfide-stabilized β-sheet or β-hairpin conformation • 2 cross-strand disulfide bonds • 6 cationic residues (Doherty et al. 2006)	• Produced by horseshoe crabs' hemocytes (Nakamura et al. 1988; Minardi et al. 2007)	• Bacteria • Fungi • Viruses (Nakamura et al. 1988; Hancock and Lehrer 1998)	–
Stylicins	• Anionic • Theoretical pI of 5 • 82 a.a. (8.9 kDa) • Proline-rich N-terminal region • C-terminal portion with 13 cysteine residues (Rolland et al. 2010; Rosa and Barracco 2010)	• Produced by the penaeid shrimp Litopenaeus stylirostris (Rolland et al. 2010)	Fungi (Rolland et al. 2010)	• Bind LPS (Rolland et al. 2010)
Crustins	• 50 a.a. • 8 cysteine residues • Signal sequence at the N-terminus • Whey acidic protein (WAP) domain at the C-terminus • Tightly packed structure • 3 types: between the signal sequence and the WAP domain, type I crustins contain a cysteine-rich region, type II a glycine-rich and a cysteine-rich region and type III a proline-arginine-rich domain (Krusong et al. 2012)	• Produced by various crustaceans, including several shrimp species (Krusong et al. 2012)	• Bacteria (Krusong et al. 2012)	–
Plants	Thionins	• ∼5 kDa • Cysteine-rich • Basic • 2 types: α/β-thionins and γ-thionins (or plant defensins) (Stec 2006)	• Produced by monocots (grains) and eudicots, including dicotyledonous plants (different species of mistletoe and Pyrularia pubera), and rosids (crambin) (Stec 2006)	• Bacteria • Fungi (Stec 2006)	–
Cyclotides	• 30 a.a. • Amphipathic • Zero charge at neutral pH • Globular proteins • Head-to-tail cyclic backbone structure combined with a cystine knot • (Garcia and Camarero 2010; Smith et al. 2011)	• Produced by large plants (Garcia and Camarero 2010; Smith et al. 2011)	• Bacteria • Viruses • Insects (Garcia and Camarero 2010; Smith et al. 2011)	• Ultra-stable to thermal, chemical, and enzymatic degradation (Garcia and Camarero 2010; Smith et al. 2011)
Lipid Transfer Proteins (LTPs)	• 2 families: LTP1 (90–95 a.a., 9 kDa) and LTP2 (70 a.a., 7 kDa), with different patterns of disulfide bridges (Kido et al. 2010)	• Produced by higher plants (Kader 1996)	• Fungi • Bacteria (Kader 1996; Wang et al. 2004)	• Transfer phospholipids between a donor and an acceptor membrane (Kader 1996; Kido et al. 2010)
Bacteria	Bacteriocins	• Ribossomally synthesized • Class I bacteriocins: small (18–39 a.a.); called lantibiotics because of their lanthionine or β-methyllanthionine residues, formed during post-translational modification • Class II bacteriocins: very diverse group not subject to extensive posttranslational modification • Class III bacteriolysins: large, heat-labile proteins; catalyze the hydrolysis of bacterial cell walls (Sang and Blecha 2008)	• Produced by different groups of bacteria and archaea (Gálvez et al. 2007; Sang and Blecha 2008)	• Bacteria of the same species (narrow spectrum) • Bacteria of other genera (broad spectrum) (Sang and Blecha 2008)	–
Gramicidins	• Non-ribosomally synthesized • Prototypical channel formers • Gramicidins A, B, and C: linear penta-decapeptides; β-helix (6.3 a.a. per turn); alternating L- and D-a.a. composition except for position 2 (Gly) • Gramicidin S: backbone-cyclized cationic decapeptide; antiparallel β-sheet (Mogi and Kita 2009; Yala et al. 2011)	• Produced by the bacterium Aneurinibacillus migulanus (formerly known as Bacillus brevis) (Mogi and Kita 2009)	• Bacteria (Mogi and Kita 2009; Yala et al. 2011)	• Used to study organization, dynamics, and function of membrane-spanning channels (Yala et al. 2011) • Linear gramicidins enter lipid membranes forming a dimer channel that conducts a cation flow (Mogi and Kita 2009; Yala et al. 2011)
Polymyxins	• Non-ribosomally synthesized • Pentabasic decapeptides • Contain a cyclo-heptapeptide ring with a C9 or C10 hydrophobic fatty acid chain through a α-amide linkage (Mogi and Kita 2009)	• Produced by Gram-positive bacterium Bacillus polymyxa (Mogi and Kita 2009)	• Gram-negative bacteria (Martti 2010)	• Polymyxins B and E (colistin) used in the last resort treatment of Gram-negative bacterial infections • Bind LPS (Martti 2010)
Fungi	Peptaibols	• 10–20 a.a. • Non-ribosomally synthesized • High proportion of genetically non-coded amino acids ( α-aminoisobutyric acids (Aibs) or α-methylalanines and isovaline (Iva)) • C-terminal alcohol (Sang and Blecha 2008; Duclohier 2010)	• Produced by the hyphomycetous fungi of the Trichoderma genus (Duclohier 2010)	• Bacteria • Fungi (Sang and Blecha 2008)	–
Synthetic and Modified	Specifically (or selectively) targeted antimicrobial peptides (STAMPs)	• Targeting peptide domain fused to an antimicrobial, or ‘killing’, peptide domain, both functionally independent (Eckert et al. 2006a; He et al. 2010)	• Chemically synthesized with high-yield in vitro (Eckert et al. 2006a)	• Bacteria (Eckert et al. 2006a; He et al. 2010)	• Increased killing potency, selectivity, and kinetics (Eckert et al. 2006a)
Synthetic antimicrobial peptidomimetics (SAMPs)	• Extremely short (Flemming et al. 2009)	• Developed through modifications of the cationic antimicrobial peptides (CAPs) (Flemming et al. 2009)	• Same as CAP used (Flemming et al. 2009)	• Improved pharmacokinetic properties (Flemming et al. 2009)
Hydrophobic end-tagged AMPs	• Hydrophobic amino acid stretches at the C-terminal end (Malmsten et al. 2011)	• Developed through hydrophobic C-terminal tagging of AMPs (Malmsten et al. 2011)	• Bacteria (Malmsten et al. 2011)	• Improved bactericidal potency (Malmsten et al. 2011)
Automatically designed peptide antibiotics (adepantins)	• Based on anuran AMPs (Juretić et al. 2009)	• De novo peptides, outputs of a Designer algorithm (Juretić et al. 2009)	• Gram-negative bacteria (Juretić et al. 2009)	• Designer algorithm uses an objective construction procedure, based on collected experimental data from anuran AMPs (Juretić et al. 2009)
AMPs mimetics	Multimeric or Dendrimeric peptides	• Branched polymers with peptides attached centrally to a template or core matrix • Higher local concentration of bioactive units (Giuliani and Rinaldi 2011)	• De novo molecules with multiple peptide sequences added to an inner core usually of radially branched lysine residues (Bruschi et al. 2010; Giuliani and Rinaldi 2011)	• Bacteria (Bruschi et al. 2010; Giuliani and Rinaldi 2011) • Viruses (Giuliani and Rinaldi 2011)	• Resistant to peptidases and proteases • Increased activity (Giuliani and Rinaldi 2011)
Peptoids or Amptoids	• Oligo N-substituted glycines • Isomers of AMPs with side chains attached to the backbone nitrogen rather than the α-carbon (Giuliani and Rinaldi 2011)	• De novo peptides constructed via a library of peptoid monomers tuned for hydrophobicity and side-chain charge (Chongsiriwatana et al. 2008; Giuliani and Rinaldi 2011)	• Bacteria • Fungi (Giuliani and Rinaldi 2011; Kapoor et al. 2011)	• Resistant to proteases • Reduced immunogenicity • Improved bioavailability • Highly tunable side-chain chemistry (Chongsiriwatana et al. 2008; Giuliani and Rinaldi 2011)
Oligoacyllysines (OAKs)	• Composed of tandem repeats of acyllysines (Giuliani and Rinaldi 2011) • Hydrophobic and cationic (Giuliani and Rinaldi 2011)	• De novo peptides that mimic the primary structure and function of AMPs (Giuliani and Rinaldi 2011)	• Bacteria (Sarig et al. 2010; Giuliani and Rinaldi 2011)	• Does not form defined secondary structures due to optimal rotational freedom of the carbon atoms in an acyl chain • Increased vivo efficacy • Less toxic (Giuliani and Rinaldi 2011)
Ceragenins	• Derivatives of bile acids with covalently attached amines • Cationic (Giuliani and Rinaldi 2011)	• De novo molecules whose design was inspired by the aminosterol squalamine (Giuliani and Rinaldi 2011)	• Bacteria (Savage et al. 2002; Giuliani and Rinaldi 2011)	• LPS and (lipoteichoic acid) LTA binding activity (Giuliani and Rinaldi 2011)
DL-Amino acid diastereomers	• Do not retain α-helical structure of AMPs (Vooturi and Firestine 2010)	• De novo molecules obtained by incorporation of D-a.a. in the peptides (Vooturi and Firestine 2010)	• Bacteria (Vooturi and Firestine 2010)	• Increased activity • Resistant to proteases • Not cytotoxic on mammalian cells (Vooturi and Firestine 2010)

Figure 1. General statistics on the number of publications on AMPs (blue bars) and AMP applications to biofilms (red bars) in PubMed. The word cloud highlights research areas where these studies are most relevant.

Table 2. Recent applications of AMPs in the control of biofilms.

		Minimal active concentration
		Pre-treatment		Therapy
AMPs	Microorganisms	B	P	B	P	Reference
1010cys	Pseudomonas aeruginosa	14.2 peptides nm^−2 (on copolymer brush DMA/APMA) on Ti surfaces)		–		Gao et al. (2011a)
Aurein 2.5	Bacillus subtilis Escherichia coli	125 μM (MIC)	30 μM (MIC)	–		Dennison et al. (2009)
BMAP-28	Staphylococcus aureus	2 μg ml^−1 (MIC) 4 μg ml^−1 (MBC)		4 μg ml^−1 (MIC) 16 μg ml^−1 (MBC) 10 μg ml^−1 (CVC infection in rat)	–	Cirioni et al. (2006)
C16G2	Streptococcus mutans	–	3 μM	25 μM	–	Eckert et al. (2006b)
Chrysophsin-1	Streptococcus mutans	–	4 μg ml^−1 (MIC) 8 μg ml^−1 (MBC)	16 μg ml^−1	–	Wang et al. (2012)
F2,5,12W	Staphylococcus epidermidis	2.5 μM	10 μM	40 μM	–	Molhoek et al. (2011)
G10KHc	Pseudomonas aeruginosa	–	0.5 – 29 μM (MIC)	100 μg ml^−1	–	Eckert et al. (2006a)
Gramicidin A	Listeria ivanovii Enterococcus faecalis Staphylococcus aureus Escherichia coli Candida albicans	20 μg ml^−1 for 2h (cystamine self-assembled monolayers on gold surfaces)	–	–		Yala et al. (2011)
HBD3	Staphylococcus aureus Candida albicans	–	0.2 & 0.4 μg m1^−1 25 & 50 μg ml^−1 (MIC & MBC)	0.2 μg ml^−1 25 μg ml^−1  (on maxillofacial silicone elastomer disks)	–	(Shi et al. 2009)
KSL	Streptococcus mutans	62.5 μg ml^−1 (MIC)		0.25 mg ml^−1	–	(Liu et al. 2011)
Lacticin 3147	Streptococcus mutans	6.3 μmol l^−1	1.9–3.8 μmol l^−1 (MIC) 38 μmol l^−1 (MBC)	50 μmol l^−1	–	(Dobson et al. 2011)
LL-31	Burkholderia pseudomallei	–		20 ìM		(Kanthawong et al. 2012)
LL-37	Burkholderia pseudomallei	–		20 ìM		(Kanthawong et al. 2012)
Staphylococcus aureus	10 μg ml^−1	1.27 μg ml^−1 (EC50)	–		(Dean et al. 2011)
Candida albicans	20 μg ml^−1	–	–	20 μg ml^−1	(Tsai et al. 2011)
Pseudomonas aeruginosa	16 μg ml^−1 (MIC)	64 μg ml^−1 (MIC)	4 μg ml^−1	–	(Overhage et al. 2008)
Ltx10	Staphylococcus epidermidis Staphylococcus haemolyticus	–	2 μg ml^−1 4 μg ml^−1 (MIC)	50 μg ml^−1	–	(Flemming et al. 2009)
Ltx5	Staphylococcus epidermidis Staphylococcus haemolyticus	–	4 μg ml^−1 8 μg ml^−1 (MIC)	50 μg ml^−1	–	(Flemming et al. 2009)
Ltx9	Staphylococcus epidermidis Staphylococcus haemolyticus	–	2 μg ml^−1 4 μg ml^−1 (MIC)	50 μg ml^−1	–	(Flemming et al. 2009)
Magainin I	Listeria ivanovii	0.1 mg ml^−1 (on SS-SC-Chi-Tere surfaces)	–	–		(Héquet et al. 2011)
Listeria ivanovii Bacillus cereus	–		5% of a polymer brush		(Glinel et al. 2009)
Nisin	Staphylococcus aureus	1.25 ìg ml^−1	10 ìg ml^−1	–	–	(Qi et al. 2011)
Listeria ivanovii	0.1 mg ml^−1 (on SS-SC-Chi-Tere surfaces)	–	–		(Héquet et al. 2011)
Omiganan pentahydrochloride	MSSA MRSA MSSE MRSE	–	2–4 μg ml^−1 2–8 μg ml^−1 4 μg ml^−1 4 μg ml^−1 (MIC)	1% omigan aqueous gel (on skin colonisation models)	–	(Rubinchik et al. 2009)
Peptoid 1 Peptoid 1-C134mer	Pseudomonas aeruginosa	12.5 ìM	12.5 ìM (MIC)	12.5 ìM	–	(Kapoor et al. 2011)
Phylloseptin-1	Staphylococcus aureus	5 μM (MBEC)	5 μM (MIC)	–		(Zhang et al. 2010)
Pleurocidin	Streptococcus mutans Streptococcus sanguinis Streptococcus sobrinus Streptococcus gordonii Lactobacillus fermenti	–	8–16 μg ml^−1 (MIC) 16 μg ml^−1 (MBC)	64 μg ml^−1	–	(Tao et al. 2011)
PTP-7	Staphylococcus aureus	4 ìM	2–4 ìM (MIC) 4–8 ìM (MBC)	20–40 ìM	–	(Kharidia and Liang 2011)
Tachyplesin III	Pseudomonas aeruginosa	4 & 32 μg ml^−1 (MIC & MBC) 10 μg ml^−1 (for 30 min. in vivo on ureteral stents)	2 & 4 μg ml^−1 (MIC & MBC)	–		(Minardi et al. 2007)
Tet20	Pseudomonas aeruginosa	10.2 peptides nm^−2 (on copolymer brush DMA/APMA) on Ti surface)	–		(Gao et al. 2011a)
Tet213	Staphylococcus aureus Pseudomonas aeruginosa	∼9 mg cm^−2		–		(Kazemzadeh-Narbat et al. 2010)
Pseudomonas aeruginosa	0.20 chains nm^−2 (on copolymer brush DMA/APMA) on Ti surface)		–		(Gao et al. 2011b)
14.5 peptides nm^−2 (on copolymer brush DMA/APMA) on Ti surface)		–		(Gao et al. 2011a)
Tet26	10.5 peptides/nm^2 (on copolymer brush DMA/APMA) on Ti surface)		–		(Gao et al. 2011a)
Tn-AFP1	Candida tropicalis	32 μg ml^−1 (MIC)		–		(Mandal et al. 2011)
α-MSH	MRSA	–		12 μM	3 μM	(Madhuri et al. 2009)
(RW)4D	Escherichia coli	40 μM		–		(Hou et al. 2009)
Note: MSSA = methicillin-sensitive Staphylococcus aureus; MRSA = methicillin-resistant S. aureus; MSSE = methicillin-sensitive Staphylococcus epidermidis; MRSE = methicillin-resistant S. epidermidis; CVC = central venous catheter; B = biofilm; P = planktonic; MIC = minimal inhibitory concentration; MBC = minimal bactericidal concentration; MBEC = minimal biofilm eradication concentration; EC50 = half maximal effective concentration; IC50 = 50% growth inhibitory concentration. Pre-treatment accounts for the growth of cells in the presence of the AMP and also for the surface treatment, when indicated. Therapy accounts for the application of AMPs to the pre-grown biofilms or cells.

Figure 2. Bioinformatics resources for AMP studies. MS = mass spectrometry; LC = liquid chromatography; ANNs = artificial neural networks; HMMs = hidden Markov models; QMs = quantitative matrices; SVMs = support vector machines; RFs = random forests; DA = discriminant analysis; QSAR = quantitative structure–activity relationship.

Table 3. Contents and tools (similarity search, sequence alignment, prediction and others) of current AMP-related databases.

		Tools
Database (URL and reference)	Contents	Similarity search	Sequence alignment	Prediction	Other
AMSDb http://www.bbcm.units.it/∼tossi/amsdb.html	Gene encoded AMPs and proteins from animals and plants.	–	–	No	–
APD2 http://aps.unmc.edu/AP/main.php; Wang et al. (2009)	Categorizes peptides into families, sources, post-translational modifications, and binding targets.	–	–	Yes	Improvement of design peptides.
BACTIBASE http://bactibase.pfba-lab-tun.org/main.php; Hammami et al. (2007, 2010)	Bacteriocin natural AMPs.	BLAST, FASTA, Smith-Waterman	ClustalW, MUSCLE and T-Coffee	Yes (structure)	Physicochemical profile analysis; HMMER.
BAGEL2 http://bagel2.molgenrug.nl; de Jong et al. (2010)	Identifies putative bacteriocins.	BLAST(p or x)	–	Yes (ORFs prediction)	–
CAMP http://www.bicnirrh.res.in/antimicrobial; Thomas et al. (2010)	AMP sequences (experimentally validated and predicted), sources, activity (MIC values), reference literature, target and non-target organisms.	BLAST	–	Yes (sequences with antimicrobial activity based on SVMs, RFs, DA)	Physicochemical profile analysis.
DAMPD http://apps.sanbi.ac.za/dampd/; Seshadri Sundararajan et al. (2011)	Manually curated AMPs (update and replacement of the ANTIMIC database)	BLAST	ClustalW	Yes (signal peptide cleavage sites; sequence for antimicrobial activity based on SVMs)	HMMER; hydrophobicity calculator; graphical views; sub-database selection – UniProt, Swiss-Prot and TrEMBL
Defensins knowledgebase http://defensins.bii.a-star.edu.sg/; Seebah et al. (2007)	Sequence, structure and activity of defensins Related information on patents, grants, research laboratories and scientists, clinical studies and commercial entities.	BLAST	ClustalW	No	Analogs search.
MiniCOPE http://www.copewithcytokines.org/cope.cgi?key= Innate%20immunity%20defense%20peptides%20MiniCOPE%20Dictionary	Dictionary available from COPE (Cytokines & Cells Online Pathfinder Encyclopedia) for innate immunity defense peptides with antibiotic activities.	–	–	No	–
PenBase http://www.penbase.immunaqua.com; Gueguen et al. (2006)	Specialized database for the penaeidin family of AMPs, providing information about their properties, diversity and nomenclature.	BLAST	ClustalW	No	Database primers for subgroup determination.
Peptaibol database http://peptaibol.cryst.bbk.ac.uk/home.shtml; Whitmore and Wallace (2004)	Peptaibol related information from works published in scientific journals.	–	–	–	–
PhytAMP http://phytamp.pfba-lab-tun.org/main.php; Hammami et al. (2009)	Plant AMPs, including taxonomic, microbiological and physicochemical data.	BLAST, FASTA, Smith-Waterman	ClustalW, MUSCLE and T-Coffee	No	HMMER
RAPD http:/faculty.ist.unomaha.edu/chen/rapd/index.php; Li and Chen (2008)	Recombinantly-produced AMPs. Information about expression host, fusion strategy, release method and yield.	–	–	No	DNA translator; peptide calculator; DNA sequence convertor.
YADAMP http://www.yadamp.unisa.it/; Piotto et al. (2012)	Information on AMPs active against bacteria based on an extensive literature search.	–	–	–	–

Table 4. Synergism studies involving AMPs.

Tested compounds		Microorganisms	Culture state	Reference
Compound 1 (AMPs)	Compound 2 (AMP or other)
6752	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Bactenecin	Protegrin 1 Indolicidin	Escherichia coli	Planktonic	Yan and Hancock (2001)
	Protegrin 1	Pseudomonas aeruginosa	Planktonic	Yan and Hancock (2001)
Bacteriocin PsVP-10	Chlorhexidine	Streptococcus mutans Streptococcus sobrinus	Planktonic	Lobos et al. (2009)
BMAP-28	Quinupristin/dalfopristin (Q/D) Linezolid Vancomycin	Staphylococcus aureus	Both	Cirioni et al. (2006)
Bovine lactoferrin	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Cecropin	Rifampicin	Pseudomonas aeruginosa	Planktonic	Cirioni et al. (2008b)
Colistin	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
	Tobramycin	Pseudomonas aeruginosa	Biofilm/in vivo	Herrmann et al. (2010)
	Rifampicin	Pseudomonas aeruginosa	Planktonic/mouse pneumonia model	Aoki et al. (2009)
	Imipenem	Pseudomonas aeruginosa	Planktonic	Cirioni et al. (2007)
D-9-mer peptides	Tetracycline Piperacillin Chloramphenicol Cefotaxime Rifampicin	Pseudomonas aeruginosa Staphylococcus aureus	Planktonic	Iwasaki et al. (2007)
Daptomycin	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Dermaseptin S3(1-16)	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
G10KHc	Tobramycin	Pseudomonas aeruginosa	Planktonic	Eckert et al. (2006b)
Gaegurin 6 (GGN6)	Xylitol	Streptococcus gordonii	Planktonic	Kim et al. (2003)
GK14K4	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Gomesin	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
hLF (1-11)	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Indolicidin	Protegrin 1	Pseudomonas aeruginosa	Planktonic	Yan and Hancock (2001)
	Protegrin 1	Escherichia coli	Planktonic	Yan and Hancock (2001)
KR-20	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Lactoferrin	Ciprofloxacin Clarithromycin Minocycline	Porphyromonas gingivalis	Biofilm	Wakabayashi et al. (2009)
LL-37	Protegrin 1	Pseudomonas aeruginosa	Planktonic	Yan and Hancock (2001)
	Protegrin 1	Escherichia coli	Planktonic	Yan and Hancock (2001)
	Protegrin 1 Bactenecin	Enterococcus faecalis	Planktonic	Yan and Hancock (2001)
Magainin 2	Rifampicin	Pseudomonas aeruginosa	Planktonic	Cirioni et al. (2008b)
	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
	PGLa	Escherichia coli	Planktonic	Westerhoff et al. (1995); Tremouilhac et al.(2006); Strandberg et al. (2009)
Melanotropin-α	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
meta-phenylene ethynylene (mPE)	Chlorhexidine	Streptococcus mutans	Planktonic	Beckloff et al. (2007)
MUC7-12mer	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Nigrocin-OG13	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Nisin	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
	Sodium fluoride	Staphylococcus aureus	Both	Tong et al. (2011)
Odorranain-G1	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Parasin-I	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Pexiganan	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
Polymyxin B	Lysostaphin	Staphylococcus aureus	Planktonic	Desbois and Coote (2011)
PTP6	Chlorhexidine	Streptococcus sobrinus	Planktonic	Kim et al. (2003)
Ranalexin	Lysostaphin	Staphylococcus aureus	Planktonic/in vivo	Graham and Coote (2007); Desbois et al. (2010); Desbois and Coote (2011)
Tachyplesin III	Imipenem	Pseudomonas aeruginosa	Planktonic	Cirioni et al. (2007)
	G-CSF TZP	Mixed (primarily Escherichia coli, Klebsiella spp., Enterobacter spp., Gram-positive enterococci and staphylococci, and anaerobic Bacteroides spp.)	In vivo (murine neutropenic intraabdominal infection)	Cirioni et al. (2008a)
	TZP	Pseudomonas aeruginosa	Biofilm/in vivo (rat model ureteral stent infection)	Minardi et al. (2007)
Note: Both = biofilm and planktonic.