Abstract
Streptococcus pneumoniae is a leading cause of pneumonia mortality globally. Pneumococcal disease is often associated with prolonged colonisation of hosts and this process is facilitated by biofilm formation that is largely resistant to conventional antibiotics. We investigated the effects of antimicrobial peptides (AMPs) lysozyme, lactoferrin, LL37 and a combination of all three on planktonic growth, biofilm formation and biofilm-derived bacterial viability by S. pneumoniae, serotype 23F. Planktonic growth and biofilm-derived bacterial viability were determined using standard colony-forming techniques, while biofilm formation was measured using a crystal violet based spectrophotometric method. Relative to controls, lysozyme significantly reduced biofilm formation (0.08 OD vs. 0.10 OD at 570 nm, p = 0.01), while LL37 and the AMP combination increased biofilm formation (0.14 OD vs. 0.10 OD at 570 nm, p = 0.01). The combination of AMPs significantly decreased planktonic growth (1.10 × 108 colony-forming units per millilitres [CFU/mL] vs. 2.13 × 108 CFU/mL, p = 0.02). Biofilm-derived bacterial viability was greatly reduced by exposure to a combination of AMPs (1.05 × 105 CFU/mL vs. 1.12 × 106 CFU/mL, p = 3.60 × 10−8). Streptococcus pneumoniae displays marked resistance to the individual AMPs. A combination of lysozyme, lactoferrin and LL37 effectively inhibited planktonic growth and biofilm-derived bacterial viability; however, persister cell growth was still evident after exposure.
Highlights
Streptococcus pneumoniae is an immense public health problem
Exposure to LL37 was associated with increased planktonic growth relative to controls (2.90 × 108 colony-forming units (CFU)/mL vs. 2.13 × 108 CFU/mL, Mann–Whitney U-test (MW) p = 0.02)
Lysozyme significantly reduced the amount of biofilm formed (0.08 OD vs. 0.10 OD at 570 nm, MW p = 0.01) and LL37 greatly increased biofilm formation (0.19 OD vs. 0.10 OD at 570 nm, MW p = 9.60 × 10−6)
Summary
Streptococcus pneumoniae is an immense public health problem. In preceding decades, expanded vaccination and antimicrobial therapy have led to an impressive reduction in pneumococcalassociated morbidity and mortality. S. pneumoniae is the leading cause of mortality for lower respiratory tract infections globally.[1] Streptococcus pneumoniae colonises hosts by forming biofilms in the respiratory tract, and the biofilm-derived bacteria are resistant to antibiotic therapy.[2] A biofilm refers to a mushroom-shaped colony of bacteria adherent to a surface and encased in an extracellular matrix composed of a variety of polymers including, but not limited to, adhesion molecules, pili, protein binding carbohydrates and extracellular deoxyribonucleic acid (DNA) derived from dead bacteria.[3] A biofilm’s development and dispersal are regulated by quorum-sensing mechanisms that control bacterial colonies’ growth, gene expression and metabolism in response to environmental and internal stimuli.[4] Biofilms are an important contributor to bacterial survival following exposure to antibiotics and can promote the emergence of antibiotic resistance through persister cells that survive the initial exposure.[5]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
