Friday, 14 July 2017 13:55

Biofilms differ in susceptibility to antibiotics

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Published in mBiosphere

A new Antimicrobial Agents and Chemotherapy report shows that species composition of a biofilm influences its susceptibility to antibiotics. The work has important implications for treatment of cystic fibrosis patients, whose lungs are often colonized with mixed biofilms, the compositions of which shift as patients age. 

AACJournal: Community composition determines activity of antibiotics against multispecies biofilms

The study, from first author Sarah Tavernier and lead scientist Tom Coenye, focused on three bacterial species: Pseudomonas aeruginosa, Streptococcus aureus, and Streptococcus anginosus. All three species are often isolated from CF lungs, but S. aureus is commonly the dominant species during childhood, while P. aeruginosa dominates during adulthood. The scientific team tested the ability of the three species to form biofilms and the susceptibility of these biofilms to antibiotic treatment.

When exposed to a number of different antibiotics, more S. aureus cells died in multispecies biofilms than in biofilms of S. aureus cells alone, while P. aeruginosa was equally drug susceptible in a mono- or multispecies biofilm. When treated with drugs targeting the cell wall, such as vancomycin, fewer S. anginosus cells were killed in a multispecies biofilm than in a monospecies biofilm.  

The researchers tested how these species interact by looking at the spent supernatant from monospecies biofilms, which contains bacterial waste products and signaling molecules that may influence bacterial behavior. S. anginosus was protected from antibiotic killing when grown in the supernatant from S. aureus biofilms, but not in supernatant from P. aeruginosa biofilms, suggesting that a secreted S. aureus factor protects S. anginosus during mixed-biofilm growth. This protection was also observed with spent medium from S. aureus planktonic culture.

This research suggests that targeting either P. aeruginosa or S. aureus may not efficiently target S. anginosus in CF patients, and this may help explain why S. anginosus can be linked to acute pulmonary exacerbations in some CF patients. This increased understanding may lead to more effective treatments against all biofilm community members and improvements for CF patient outcome. 

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Last modified on Friday, 14 July 2017 14:05
Julie Wolf

ASM Communications Social Media Specialist Julie Wolf spent her research career focused on medical mycology and infectious disease. Broadly interested in microbiology and scientific communication, she has taught at Long Island University and the community biolab Genspace and has written for the Scientista Foundation and Scholastic’s Science World magazine. Follow her on Twitter for more ASM and Microbiology highlights at @JulieMarieWolf.