Healthcare-associated infections (HAI) are a huge public health concern,particularly when the etiological agents are multidrug resistant. The ability of bacteria to
develop biofilm is a helpful skill, both to persist within hospital units and to increase
antibiotic resistance. Although the links between antibiotic resistance, biofilms assembly
and HAI are consensual, little is known about biofilms. Here, electron microscopy was
adopted as a tool to investigate biofilm structures associated with increased antibiotic resistance. The K. pneumoniae strains investigated are able to assemble biofilms, albeit with different kinetics. The biofilm structure and the relative area fractions of bacteria and
extracellular matrix depend on the particular strain, as well as the minimal inhibitory
concentration (MIC) for the antibiotics. Increased values were found for bacteria organized
in biofilms when compared to the respective planktonic forms, except for isolates Kp45
and Kp2948, the MIC values for which remained unchanged for fosfomycin. Altogether,
these results showed that the emergence of antimicrobial resistance among bacteria
responsible for HAI is a multifactorial phenomenon dependent on antibiotics and on
bacteria/biofilm features