DLC coatings for UHMWPE: relationship between bacterial adherence and surface properties.

Development of intrinsically antibacterial surfaces is of key importance in the context of prostheses used in orthopedic surgery. This work presents a thorough study of several plasma-based coatings that may be used with this functionality: diamond-like carbon (DLC), fluorine-doped DLC (F-DLC), and a high-fluorine-content-carbon-fluor polymer (CF(X)). The coatings were obtained by a radio-frequency plasma-assisted deposition on ultra high molecular weight polyethylene (UHMWPE) samples and physicochemical properties of the coated surfaces were correlated with their antibacterial performance against collection and clinical Staphylococcus aureus and Staphylococcus epidermidis strains. The fluorine content and the relative amount of C-C and C-F bonds were controlled by X-ray photoelectron spectroscopy, and hydrophobicity and surface tension by contact angle measurements. Surface roughness was studied by Atomic Force Microscopy. Additional nanoidentation studies were performed for DLC and F-DLC coatings. Unpaired t test and regression linear models evaluated the adherence of S. aureus and S. epidermidis on raw and coated UHMWPE samples. Comparing with UHMWPE, DLC/UHMWPE was the least adherent surface with independence of the bacterial species, finding significant reductions (p ≤ 0.001) for nine staphylococci strains. Bacterial adherence was also significantly reduced in F-DLC/ UHMWPE and CFx/UHMWPE for six strains.

Differences in the in vitro susceptibility of planktonic and biofilm-associated Escherichia coli strains to antimicrobial agents.

The in vitro susceptibility of seven Escherichia coli biofilm-producing strains in their planktonic and biofilm-associated forms to amoxicillin, amoxicillin/clavulanic acid, cefotaxime, gentamicin, and ciprofloxacin was studied. Minimum inhibitory concentrations (MICs) were determined by the standard microdilution method and by the Alamar blue assay (providing the AB-MIC) at two levels of metabolic suppression and using standard and large inocula. Minimal biofilm inhibitory concentrations (AB-MBICs) on preformed biofilms on polystyrene plates were higher than the MICs and AB-MICs. Differences in magnitude depended on the antibiotic, strain, inoculum size, and the level of suppression of metabolism. Ciprofloxacin and gentamicin showed the greatest differences in the AB-MBIC as compared to AB-MIC. the possibility of antibiotic-resistant mutant selection within the biofilms was ruled out since bacteria recovered from the biofilm maintained the same MICs as before exposure to the antimicrobial agents. E. coli biofilms were much less sensitive than their planktonic counterparts.

Effects of human serum albumin, ibuprofen and N-acetyl-L-cysteine against biofilm formation by pathogenic Escherichia coli strains.

The aim of this study was to evaluate the effects of human serum albumin (HSA), ibuprofen sodium (IBU) and N-acetyl-L-cysteine (NAC) against biofilm formation by seven biofilm-producing strains of Escherichia coli. Biofilm formation was studied using polystyrene microtitre plates in static conditions. The impact of the three compounds on bacterial growth and biofilm formation was tested by applying each compound in solution and as pre-treatment (coating) of polystyrene wells. When studied in solution, the minimum biofilm inhibitory concentrations of HSA, IBU and NAC were 8 mg/L (all strains), 2-125 mg/L (five strains) and 30-125 mg/L (five strains), respectively. Pre-treatment of polystyrene plates with HSA at 8 and 32,000 mg/L significantly reduced biofilm formation by all strains, whereas coating with 125 mg/L IBU and 1000 mg/L NAC did not. When HSA at 8 and 32,000 mg/L was combined with either 125 mg/L IBU or 1000 mg/L NAC in pre-treatment assays, more potent inhibition of biofilm was observed for some strains. Our results suggest that biofilm formation by E. coli may be prevented by coating medical devices with HSA alone or in combination with IBU or NAC. In addition, IBU and NAC could be useful in the treatment of urinary tract infections caused by E. coli due to their inhibitory effect on both bacterial growth and biofilm formation.

In vitro and in vivo activity of miltefosine against penicillin-sensitive and -resistant Streptococcus pneumoniae strains.

The in vitro and in vivo activity of miltefosine against penicillin-sensitive and penicillin-resistant pneumococcal strains was studied. The minimum inhibitory concentrations (MICs) of miltefosine were determined in cation-adjusted Mueller Hinton plus 2% lysed horse blood (CAMHB) and in Todd-Hewitt (TH) broth. The respective MICs were higher using CAMHB (128 and 64 mg/L) than using TH broth (4 and 8 mg/L). The in vivo activity was studied in a murine peritonitis-sepsis model. Miltefosine was orally administered at doses of 15 and 30 mg/kg/day after, at the time of, and before bacterial challenge for 3-5 days. All control and 16 out of the 17 (94.1%) miltefosine-treated animals that were inoculated with the penicillin-sensitive strain died. No survival was observed among control and miltefosine-treated animals inoculated with the penicillin-resistant pneumococcal strain. The in vivo unresponsiveness of miltefosine in this sepsis model could be attributed to some inhibitory effect of blood, inadequate pharmacokinetics and/or the extracellular localization of the pneumococcus.

Measurement of biofilm formation by clinical isolates of Escherichia coli is method-dependent.

AIMS: In this study, we have evaluated the impact of methodological approaches in the determination of biofilm formation by four clinical isolates of Escherichia coli in static assays. METHODS AND RESULTS: The assays were performed in microtitre plates with two minimal and two enriched broths, with one- or two-steps protocol, and using three different mathematical formulas to quantify adherent bacteria. Different biofilm formation patterns were found depending on the E. coli strain, culture medium and reading optical density on one- and two-steps protocol. Strong or moderate biofilm formation occurred mostly in minimal media. The mathematical formulas used to quantify biofilm formation also gave different results and bacterial growth rate should be taken into account to quantify biofilm. CONCLUSIONS: Escherichia coli forms biofilms on static assays in a method-dependent fashion, depending on strain, and it is strongly modulated by culture conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: As verified in the studied E. coli strains, biofilm formation by any organism should be cautiously interpreted, considering all variables in the experimental settings.

Nistagmo vertical secundario a la administración de morfina epidural / Vertical nystagmus secondary to the epidural administration of morphine

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