Susceptibility patterns of Staphylococcus aureus biofilms in diabetic foot infections

Abstract

BackgroundFoot infections are a major cause of morbidity in people with diabetes and the most common cause of diabetes-related hospitalization and lower extremity amputation. Staphylococcus aureus is by far the most frequent species isolated from these infections. In particular, methicillin-resistant S. aureus (MRSA) has emerged as a major clinical and epidemiological problem in hospitals. MRSA strains have the ability to be resistant to most β-lactam antibiotics, but also to a wide range of other antimicrobials, making infections difficult to manage and very costly to treat. To date, there are two fifth-generation cephalosporins generally efficacious against MRSA, ceftaroline and ceftobripole, sharing a similar spectrum.Biofilm formation is one of the most important virulence traits of S. aureus. Biofilm growth plays an important role during infection by providing defence against several antagonistic mechanisms. In this study, we analysed the antimicrobial susceptibility patterns of biofilm-producing S. aureus strains isolated from diabetic foot infections. The antibiotic minimum inhibitory concentration (MIC) was determined for ten antimicrobial compounds, along with the minimum biofilm inhibitory concentration (MBIC) and minimum biofilm eradication concentration (MBEC), followed by PCR identification of genetic determinants of biofilm production and antimicrobial resistance.ResultsResults demonstrate that very high concentrations of the most used antibiotics in treating diabetic foot infections (DFI) are required to inhibit S. aureus biofilms in vitro, which may explain why monotherapy with these agents frequently fails to eradicate biofilm infections. In fact, biofilms were resistant to antibiotics at concentrations 10–1000 times greater than the ones required to kill free-living or planktonic cells. The only antibiotics able to inhibit biofilm eradication on 50 % of isolates were ceftaroline and gentamicin.ConclusionsThe results suggest that the antibiotic susceptibility patterns cannot be applied to biofilm established infections. Selection of antimicrobial therapy is a critical step in DFI and should aim at overcoming biofilm disease in order to optimize the outcomes of this complex pathology.

Comprehensive Evaluation of the Biological Properties of Surface-Modified Titanium Alloy Implants

“…The new generation of implants should not only facilitate their tissue integration but also prevent microbial colonization and biofilm formation. Serious medical problems associated with the introduction of implants to the human body are infections, which can lead to increased patients failure and mortality [68][69][70][71]. To solve this problem, the implant surface is modified by the formation of bioactive nanostructures (e.g., TiO 2 nanotubes, nanofibers) and/or their enrichment with metal nanoparticles (mainly silver and copper) [20,27,28,[72][73][74].…”

New Antibacterial Paper Made of Silver Phosphate Cellulose Fibers: A Preliminary Study on the Elimination of Staphylococcus aureus Involved in Diabetic Foot Ulceration

“…In one small study, MBEC of Staphylococcus aureus isolated from DFU demonstrated resistance to antibiotics at concentrations 10 to 1000 times higher than those required at MIC, meaning that the antibiotic susceptibility profile cannot be applied to biofilm-established infections, particularly in the case of DFU. In this condition, broad-spectrum antibacterial agents are needed [12,68,69]. Finally, few variables were tested in the innovation of the new fibers, which means that further studies are needed to understand the silver ion release, cytotoxicity, and cell interactions in a wound model in vitro and animal model in vivo, as well as time to efficiency and duration, mechanical and physical properties of the SPCF (as a layer), and in combination with other ions such as zinc.…”

Association between biofilm and multi/extensive drug resistance in diabetic foot infection

“…Bacterial biofilm causes chronic infections because they show increased tolerance to antibiotics and disinfectants as well as resisting phagocytosis and other components of the body's tolerance system . Biofilm‐forming bacteria are refractory to host response and medical treatment. Biofilm‐forming bacterial colonies are 10 to 1000 times more resistant to antimicrobials in comparison with planktonic (free‐floating) bacteria …”

“…Biofilm‐forming bacteria are refractory to host response and medical treatment. Biofilm‐forming bacterial colonies are 10 to 1000 times more resistant to antimicrobials in comparison with planktonic (free‐floating) bacteria …”