In 2012, were estimated 6.7 million cases of healthcare-associated infections (HAI) either
in long-term care facilities or acute-care hospitals from which result 37,000 deaths
configuring a serious public health problem [1].
The etiological agents are diverse and often resistant to antimicrobial agents. One of the
mechanisms responsible for the emergence of drug resistance is biofilm assembly.
Biofilms are defined as thin layers of microorganisms adhering to the surface of a
structure, which may be organic or inorganic, together with the polymers that they secrete
[2]. They are dynamic structures which experience different stages of organization with
the ageing and are linked to an increase in bacterial resistance to host defense
mechanisms, antibiotics, sterilization procedures other than autoclaving, persistence in
water distribution systems and other surfaces. The understanding of bacteria organization
within the biofilm and the identification of differences between planktonic and sessile
forms of bacteria will be a step forward to fight HAIs.
Bacterial isolates were grown in adequate medium. Antibiotic susceptibility was
evaluated by broth microdilution method and interpreted according to NCCLS guidelines.
A similar assay was performed to evaluate biofilm susceptibility to antibiotics. Bacteria
ability to assemble biofilms was assayed by the microtiter-plate test [3] being tested in
both abiotic (materials present in healthcare units) and biotic (Hella cells) surfaces. The
biofilm structure was assessed by scanning electron microscopy (SEM) in either
backscattered electron diffraction or secondary electrons mode.
The kinetic of biofilm assembly depends on bacteria growth rate, incubation temperature
and medium. Furthermore, the SEM analysis of planktonic and sessile forms of the same
bacteria allowed the identification of structural differences which may be involved in
virulence (Fig. 1). Bacteria ability to assemble biofilms seems to be independent of the
abiotic structure (Fig.2). The same is not observed in biotic surfaces. This fact suggests
that biofilm assembly in vivo is dependent of bacteria tropism. The minimum inhibitory
concentration (MIC) determine for bacteria organized in biofilms is higher than for their
planktonic forms. The increase ranges from 2 to 200 folds and is proportional to the
ability of bacteria to assemble biofilms.
Further studies will be conducted in order to prevent biofilm assembly within healthcare
units which will result in a decrease of HAI and emergence of antibiotic resistant
bacteria
