Azeredo, Joana

Cerca, Nuno

Martins, Silvia

Oliveira, Rosário

Pier, Gerald B.

Universidade do Minho: RepositoriUM

Can studies of inhibition of adhesion by sub-mic concentrations of antibiotics predict the outcome in biofilm formation inhibition?  Nuno Cerca1 , Silvia Martins1, Gerald  Pier2, Rosario Oliveira1,  Joana Azeredo1* 1Centro de Engenharia Biológica, Minho University, Braga, Portugal 2Channing Laboratory, Brigham Women's Hospital, Harvard Medical School, Boston, USA  *Corresponding author: jazeredo@deb.uminho.pt  Abstract  The use of sub-inhibitory (sub-mic) concentrations of antibiotics has been suggested as a way of preventing biofilm formation by clinically relevant microorganisms. Many studies have demonstrated that low concentrations of antibiotics can inhibit initial microbial adherence to medical-device surfaces. However, since initial adherence and subsequent biofilm formation can be two distinct phenomena, conclusions withdrawn regarding initial adhesion adhesion cannot be extrapolated to biofilm formation.. In this study, we evaluated the adherence of several clinical isolates of Coagulase negative staphylococci (CoNS) to acrylic and the effect of sub-mic concentrations of vancomycin, cefazolin, dicloxacillin and combinations of these antibiotics.  Most of the antibiotic-strain combinations resulted in an effective reduction of bacterial adhesion, in some cases reaching 77% inhibition of adherence. Some synergistic effects were observed when using combinations of antibiotics. To determine the effect of the above antibiotics in biofilm formation, the strains with a high biofilm formation capacity were grown in sub-mic concentrations of those antibiotics. While some antibiotic-strain combinations significantly inhibited biofilm formation, most of the combinations that inhibited adherence did not have a profound effect on overall biofilm formation. No synergistic effects on reducing biofilm formation were found when using sub-mic combinations of antibiotics  When comparing the results of the effect of sub-mice amounts of antibiotics on inhibition of adherence with their effect on inhibition of biofilm formation, significant differences (p<0.05) were found, mainly when using combinations of antibiotics. In general, the effect on inhibition of adherence was greater than the effect of inhibition of biofilm formation.  Our results demonstrate that assays evaluating the inhibition of initial adherence to medical surfaces cannot predict the effect of inhibition of biofilm formation. 

Can studies of inhibition of adhesion by sub-mic concentrations of antibiotics predict the outcome in biofilm formation inhibition?

Can studies of inhibition of adhesion by sub-mic concentrations of antibiotics 
predict the outcome in biofilm formation inhibition?  
Nuno Cerca1 , Silvia Martins1, Gerald  Pier2, Rosario Oliveira1,  Joana Azeredo1* 
1Centro de Engenharia Biológica, Minho University, Braga, Portugal 
2Channing Laboratory, Brigham Women's Hospital, Harvard Medical School, Boston, USA 
 
*Corresponding author: jazeredo@deb.uminho.pt 
 
Abstract 
 
The use of sub-inhibitory (sub-mic) concentrations of antibiotics has been 
suggested as a way of preventing biofilm formation by clinically relevant microorganisms. 
Many studies have demonstrated that low concentrations of antibiotics can inhibit initial 
microbial adherence to medical-device surfaces. However, since initial adherence and 
subsequent biofilm formation can be two distinct phenomena, conclusions withdrawn 
regarding initial adhesion adhesion cannot be extrapolated to biofilm formation.. 
In this study, we evaluated the adherence of several clinical isolates of Coagulase 
negative staphylococci (CoNS) to acrylic and the effect of sub-mic concentrations of 
vancomycin, cefazolin, dicloxacillin and combinations of these antibiotics.  Most of the 
antibiotic-strain combinations resulted in an effective reduction of bacterial adhesion, in 
some cases reaching 77% inhibition of adherence. Some synergistic effects were 
observed when using combinations of antibiotics. To determine the effect of the above 
antibiotics in biofilm formation, the strains with a high biofilm formation capacity were 
grown in sub-mic concentrations of those antibiotics. While some antibiotic-strain 
combinations significantly inhibited biofilm formation, most of the combinations that 
inhibited adherence did not have a profound effect on overall biofilm formation. No 
synergistic effects on reducing biofilm formation were found when using sub-mic 
combinations of antibiotics  When comparing the results of the effect of sub-mice amounts 
of antibiotics on inhibition of adherence with their effect on inhibition of biofilm formation, 
significant differences (p<0.05) were found, mainly when using combinations of antibiotics. 
In general, the effect on inhibition of adherence was greater than the effect of inhibition of 
biofilm formation.  
Our results demonstrate that assays evaluating the inhibition of initial adherence to 
medical surfaces cannot predict the effect of inhibition of biofilm formation. 


English

http://repositorium.sdum.uminho.pt/bitstream/1822/32145/1/document_3367_1.pdf

Can studies of inhibition of adhesion by sub-mic concentrations of antibiotics predict the outcome in biofilm formation inhibition?

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