Inhibition of biofilm maturation by linezolid in meticillin-resistant Staphylococcus epidermidis clinical isolates: comparison with other drugs

Abstract

Biofilm resistance mechanisms are multifactorial and vary from one organism to another. The purpose of this study was to investigate the efficacy of linezolid against indwelling device-related meticillin-resistant Staphylococcus epidermidis (MRSE) biofilm, and compare this with other antimicrobials. MICs, minimum biofilm inhibitory concentrations (MBICs) and minimum biofilm eradication concentrations (MBECs) were determined by the microtitre plate method. Fourteen and thirteen isolates from patients with indwelling device-related bacteraemia (IDB) and indwelling device colonization not associated with bacteraemia, respectively, were assessed. High MBIC was associated with a high intensity of biofilm formation (gentamicin r50.796; linezolid r50.477; rifampicin r50.634; tigecycline r50.410; and vancomycin r50.771), but this correlation was not observed with MBEC. Linezolid demonstrated better in vitro antimicrobial activity than other antimicrobials (MBIC -gentamicin P,0.001, rifampicin P50.019, vancomycin P50.008; MBEC -gentamicin P,0.001, rifampicin P50.002, vancomycin P,0.001). Biofilm growth inhibition was strongly associated with biofilm formation intensity; however, biofilm eradication was not cell number dependent. MRSE biofilm eradication would represent a huge advance for IDB, although high concentrations of gentamicin, linezolid, rifampicin, tigecycline and vancomycin were required for that. In general, linezolid reached better in vitro concentrations and was demonstrated to be highly active against MRSE biofilms by inhibiting their growth during biofilm formation.

Antimicrobial synergism against different lineages of methicillin-resistant Staphylococcus aureus carrying SCCmec IV

“…Reiter et al . () studied the activity of rifampicin, individually and in combination with vancomycin, against biofilm producer isolates of MRSA. They found greater inhibition of bacterial growth after combined drug use than after use of each drug individually.…”

“…In our study, another synergism that was observed to present a good activity against MRSA isolates was rifampicin (2 lg ml À1 ) plus vancomycin (4 lg ml À1 ). Reiter et al (2012) studied the activity of rifampicin, individually and in combination with vancomycin, against biofilm producer isolates of MRSA. They found greater inhibition of bacterial growth after combined drug use than after use of each drug individually.…”

Susceptibility of Oral Streptococci to Chlorhexidine and Cetylpyridinium Chloride

“…Such susceptibility differences between the culture states of the bacteria can have various causes, including the difference in diffusion of the antimicrobial agent Ceri et al, 1999, Wilson, 1996, Costerton et al, 1995 Recently, the minimum biofilm inhibitory concentration MBIC and minimum biofilm eradication concentration MBEC have been proposed as experimental benchmarks for evaluating antimicrobial activity against biofilms Reiter et al, 2013, Anwar et al, 1990,Sandoe et al, 2002 . The MBIC of the antimicrobial agent is the minimum concentration at which the growth of the biofilm bacteria is inhibited, and the MBEC is the minimum concentration at which 99.9% of the biofilm bacteria are eradicated Ceri et al, 1999, Reiter et al, 2013 Streptococci are bacteria that initially attach to tooth surfaces Kara et al, 2006, Kolenbrander et al, 2002 They are present in a large number in plaques, and have a wide range of properties that allow them to adhere to pellicle components as well as other bacterial species through a coaggregation mechanism Blanc et al, 2014 . Many previous studies have observed the antibacterial effects of chlorhexidine and cetylpyridinium chloride, alone and in mouthwash formulations, on oral bacteria Koljalg et al, 2002, Gehlen et al, 2000, Kitagawa et al, 2016, Andre et al, 2011 determine the MIC and MBC.…”

“…Antimicrobial susceptibility testing of the bacterial biofilms was performed using a previously reported method Ceri et al, 1999, Reiter et al, 2013, Cafiso et al, 2010 In brief, to form biofilm on the bottom of a 96-well plate SPL flat-bottom plates , 180 µL of BHI medium and 20 µL of bacterial suspension adjusted to 0.5 McFarland standard 1 10 8 CFU/mL were added to the plates and cultured in a 5% CO 2 incubator at 37 for 18 h. After incubation, each microplate was washed three times with BHI medium to remove any non-adherent bacterial cells. Each antimicrobial agent was diluted serially in BHI medium in a new microplate, and the diluted solution was transferred to the microplate with biofilm, which was then cultured at 37 for 18 h. After incubation, the turbidity of the supernatant was observed and the minimum concentration at which bacterial growth was inhibited was determined as the MBIC.…”

“…After the biofilm is formed, the action of the antimicrobial agent on the bacteria is not the same as that on the planktonic bacteria Reiter et al, 2013 . It is known that extracellular polysaccharides surround the bacterium after biofilm formation, making it difficult for an antimicrobial agent to permeate into the biofilm as compared with its direct contact with planktonic bacteria Ceri et al, cetylpyridinium chloride MBIC values 15.63 µg/mL were 200-fold higher than their MIC values 0.06 µg/ mL .…”