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Biofilm induced tolerance towards antimicrobial peptides.

ABSTRACT: Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular targets, the peptide antibiotic colistin and the fluoroquinolone ciprofloxacin. The dynamics of microbial killing were monitored by viable count determination, and confocal laser microscopy. Strains forming structurally organized biofilms show an increased bacterial survival when challenged with colistin, compared to strains forming unstructured biofilms. The increased survival is due to genetically regulated tolerant subpopulation formation and not caused by a general biofilm property. No significant difference in survival was detected when the strains were challenged with ciprofloxacin. Our data show that biofilm formation confers increased colistin tolerance to cells within the biofilm structure, but the protection is conditional being dependent on the structural organization of the biofilm, and the induction of specific tolerance mechanisms.

SUBMITTER: Folkesson A

PROVIDER: S-EPMC2270907 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Biofilm induced tolerance towards antimicrobial peptides.

Folkesson Anders A Haagensen Janus A J JA Zampaloni Claudia C Sternberg Claus C Molin Søren S

PloS one 20080402 4

Increased tolerance to antimicrobial agents is thought to be an important feature of microbes growing in biofilms. We address the question of how biofilm organization affects antibiotic susceptibility. We established Escherichia coli biofilms with differential structural organization due to the presence of IncF plasmids expressing altered forms of the transfer pili in two different biofilm model systems. The mature biofilms were subsequently treated with two antibiotics with different molecular ...[more]

PMID: 18382672

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Project description:BACKGROUND:ClpP is important for bacterial growth and plays an indispensable role in cellular protein quality control systems by refolding or degrading damaged proteins, but the physiological significance of ClpP in Enterococcus faecalis remains obscure. A clpP deletion mutant (?clpP) was constructed using the E. faecalis OG1RF strain to clarify the effect of ClpP on E. faecalis. The global abundance of proteins was determined by a mass spectrometer with tandem mass tag labeling. RESULTS:The ?clpP mutant strain showed impaired growth at 20?°C or 45?°C at 5% NaCl or 2?mM H2O2. The number of surviving ?clpP mutants decreased after exposure to the high concentration (50× minimal inhibitory concentration) of linezolid or minocycline for 96?h. The ?clpP mutant strain also demonstrated decreased biofilm formation but increased virulence in a Galleria mellonella model. The mass spectrometry proteomics data indicated that the abundances of 135 proteins changed (111 increased, 24 decreased) in the ?clpP mutant strain. Among those, the abundances of stress response or virulence relating proteins: FsrA response regulator, gelatinase GelE, regulatory protein Spx (spxA), heat-inducible transcription repressor HrcA, transcriptional regulator CtsR, ATPase/chaperone ClpC, acetyl esterase/lipase, and chaperonin GroEL increased in the ?clpP mutant strain; however, the abundances of ribosomal protein L4/L1 family protein (rplD), ribosomal protein L7/L12 (rplL2), 50S ribosomal protein L13 (rplM), L18 (rplR), L20 (rplT), 30S ribosomal protein S14 (rpsN2) and S18 (rpsR) all decreased. The abundances of biofilm formation-related adapter protein MecA increased, while the abundances of dihydroorotase (pyrC), orotate phosphoribosyltransferase (pyrE), and orotidine-5'-phosphate decarboxylase (pyrF) all decreased in the ?clpP mutant strain. CONCLUSION:The present study demonstrates that ClpP participates in stress tolerance, biofilm formation, antimicrobial tolerance, and virulence of E. faecalis.

Project description:Purpose:The aim of this study is to improve the anti-biofilm activity of antibiotics. We hypothesized that the antimicrobial peptide (AMP) complex of the host's immune system can be used for this purpose and examined the assumption on model biofilms. Methods:FLIP7, the AMP complex of the blowfly Calliphora vicina containing a combination of defensins, cecropins, diptericins and proline-rich peptides was isolated from the hemolymph of bacteria-challenged maggots. The complex interaction with antibiotics of various classes was studied in biofilm and planktonic cultures of Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Acinetobacter baumannii by the checkerboard method using trimethyl tetrazolium chloride cell viability and crystal violet biofilm eradication assays supplemented with microscopic analysis. Results:We found that FLIP7 demonstrated: high synergy (fractional inhibitory concentration index <0.25) with meropenem, amikacin, kanamycin, ampicillin, vancomycin and cefotaxime; synergy with clindamycin, erythromycin and chloramphenicol; additive interaction with oxacillin, tetracycline, ciprofloxacin and gentamicin; and no interaction with polymyxin B. The interaction in planktonic cell models was significantly weaker than in biofilms of the same strains. The analysis of the dose-effect curves pointed to persister cells as a likely target of FLIP7 synergistic effect. The biofilm eradication assay showed that the effect also caused total destruction of S. aureus and E. coli biofilm materials. The effect allowed reducing the effective anti-biofilm concentration of the antibiotic to a level well below the one clinically achievable (2-3 orders of magnitude in the case of meropenem, ampicillin, cefotaxime and oxacillin). Conclusion:FLIP7 is a highly efficient host antimicrobial system helping antibiotics to overcome biofilm barriers through persisters' sensitization and biofilm material destruction. It is promising for the treatment of biofilm infections as an adjuvant of various small-molecule antibiotics.

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Biofilm induced tolerance towards antimicrobial peptides.

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Biofilm induced tolerance towards antimicrobial peptides.

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