In vivo demonstration of Pseudomonas aeruginosa biofilms as independent pharmacological microcompartments

• Published in: Journal of cystic fibrosis Vol. 19; no. 6; pp. 996 - 1003
• Main Authors: Christophersen, Lars, Schwartz, Franziska Angelika, Lerche, Christian Johann, Svanekjær, Trine, Kragh, Kasper Nørskov, Laulund, Anne Sofie, Thomsen, Kim, Henneberg, Kaj-Åge, Sams, Thomas, Høiby, Niels, Moser, Claus
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-11-2020
• Subjects: Alginate beads; Biofilm model; Chronic infection; Independent pharmacological compartment; Pharmacodynamics; Pharmacokinetics; PBS; Biofilm model; Pharmacodynamics; MIC; Chronic infection; RPM; PMN; Independent pharmacological compartment; CFU; PD; LB; Alginate beads; PK; Pharmacokinetics
• ISSN: 1569-1993; 1873-5010
• DOI: 10.1016/j.jcf.2020.01.009

•A biofilm matrix behaves as an independent pharmacokinetic microcompartment.•The present in vivo study confirms our previous in vitro studies of this phenomenon.•Biofilm bacterial regrowth can be observed after standard tobramycin dosing.•Modelling of pharmacokinetics predicts the low free tobramycin concentration.•Contributes to revealing the mechanisms for antibiotic tolerance of biofilms.
Pseudomonas aeruginosa is difficult to eradicate from the lungs of cystic fibrosis (CF) patients due to biofilm formation. Organs and blood are independent pharmacokinetic (PK) compartments. Previously, we showed in vitro biofilms behave as independent compartments impacting the pharmacodynamics. The present study investigated this phenomenon in vivo.
Seaweed alginate beads with P. aeruginosa resembling biofilms, either freshly produced (D0) or incubated for 5 days (D5) were installed s.c in BALB/c mice. Mice (n = 64) received tobramycin 40 mg/kg s.c. and were sacrificed at 0.5, 3, 6, 8, 16 or 24 h after treatment. Untreated controls (n = 14) were sacrificed, correspondingly. Tobramycin concentrations were determined in serum, muscle tissue, lung tissue and beads. Quantitative bacteriology was determined.
The tobramycin peak concentrations in serum was 58.3 (±9.2) mg/L, in lungs 7.1 mg/L (±2.3), muscle tissue 2.8 mg/L (±0.5) all after 0.5 h and in D0 beads 19.8 mg/L (±3.5) and in D5 beads 24.8 mg/L (±4.1) (both 3 h). A 1-log killing of P. aeruginosa in beads was obtained at 8h, after which the bacterial level remained stable at 16 h and even increased in D0 beads at 24 h. Using the established diffusion retardation model the free tobramycin concentration inside the beads showed a delayed buildup of 3 h but remained lower than the MIC throughout the 24 h.
The present in vivo study based on tobramycin exposure supports that biofilms behave as independent pharmacological microcompartments. The study indicates, reducing the biofilm matrix would increase free tobramycin concentrations and improve therapeutic effects.