Nevertheless, the most frequent mechanism is the production of β-lactamases, that hydrolize

the β-lactam ring [6, 7]. Whereas some β-lactamases degrade specific β-lactams, a great concern exists with respect to extended-spectrum β-lactamases (ESBL) [8]. Besides β-lactams, other antibiotics affect peptidoglycan, acting on different stages of biosynthesis. One of the most relevant is vancomycin, a glycopeptide that binds to terminal D-alanyl-D-alanine from the pentapeptide of the cell wall in gram-positive bacteria, blocking the incorporation of peptides to the cell wall, thus inhibiting peptydoglicane elongation [9]. Vancomycin is the last-line antibiotic for severe gram-positive infections, so the growing increase in resistance is a serious health SC79 research buy problem [10]. One mechanism of resistance to vancomycin appears to be alteration to the terminal aminoacid residues of the NAM/NAG-peptide subunits, normally D-alanyl-D-alanine, which vancomycin binds to, decreasing drug affinity [11]. The increase in the number of resistant

and multiresistant strains of bacteria is a major concern for health officials worldwide, with severe impact on economy and in public health [12]. Resistance is responsible of thousands of deaths each year. Many of them could be prevented by a rapid detection of the resistant bacteria and prompt administration of the appropriate antibiotic. This is particularly decisive in life-threatening infections or for Selumetinib patients in the intensive care unit [13]. In this case, empirical treatment fails in 20-40% cases, and the change of antibiotic based on late classic LY294002 mouse antibiogram results may be not successful. Critical clinical situations should benefit from a rapid procedure to evaluate the sensitivity or resistance to antibiotics. Moreover, a correct initial treatment, clonidine besides avoiding treatment failure, can prevent the spreading of resistant microorganisms through misuse of antibiotics. We have recently validated a rapid and simple technique to determine in situ, and at the single-cell level, the susceptibility or resistance

to quinolones, which induce DNA double-strand breaks [14–16]. The bacteria are immersed in an inert microgel on a microscope slide and incubated in a specific lysis solution that removes the cell wall, membranes and proteins. In quinolone sensitive strains, the DNA is fragmented, showing haloes of peripheral diffusion of DNA fragments emerging from the residual central core, that are visualized under fluorescence microscopy after staining with a sensitive fluorochrome. In case of resistant strains, the nucleoids liberated appear intact, with limited spreading of DNA fibre loops. Our purpose was to adapt this simple technology for a rapid evaluation of the susceptibility or resistance to antibiotics that affect the cell wall.