The gold standard for quantifying bacteria both in routine diagnostics and in research is plating followed by count of colony-forming units (CFU). But, manual CFU counting on plates is time-consuming and subjective. We evaluated fractal dimension as a new methodology for evaluating CFU. Twenty fragments of expanded polytetrafluoroethylene (ePTFE) synthetic vascular prosthesis and 20 silicone prostheses were embedded in bacterial suspensions and incubated. The prostheses were then sown in solid culture medium and incubated for 48 h. Petri dishes were photographed and analyzed by fractal dimension. There was correlation between the number of CFU in manual counting and the fractal dimension analysis ( p = 0.0001). We demonstrated that fractal dimension is a useful method for microbiological analyses in researches. It makes CFU analysis easier and faster and can be used regardless of the culture medium. Petri dishes with different bacterial colonies were photographed with a digital camera under natural light. The images were binarized and analyzed with ImageJ Ⓡ 's “fractal dimension” tool. Fractal dimension analysis showed to be a good tool for evaluating the amount of colony-forming unit.

Surface treatment of medical devices may be a way of avoiding the need for replacement of these devices and the comorbidities associated with infection. The aim of this study was to evaluate whether pre- and postcontamination washing of 2 prostheses with different textures can decrease bacterial contamination. The following microorganisms were evaluated: Staphylococcus aureus , Staphylococcus epidermidis , Proteus mirabilis and Enterococcus faecalis . Silicone and expanded polytetrafluoroethylene vascular prostheses were used and divided into 3 groups: prostheses contaminated; prostheses contaminated and treated before contamination; and prostheses contaminated and treated after contamination. Treatments were performed with antibiotic solution, chlorhexidine and lidocaine. After one week of incubation, the prostheses were sown in culture medium, which was incubated for 48 hours. The area of colony formation was evaluated by fractal dimension, an image analysis tool. The antibiotic solution inhibited the growth of S epidermidis and chlorhexidine decrease in 53% the colonization density for S aureus in for both prostheses in the pre-washing. In postcontamination washing, the antibiotic solution inhibited the growth of all bacteria evaluated; there was a 60% decrease in the colonization density of S aureus and absence of colonization for E faecalis with chlorhexidine; and lidocaine inhibited the growth of S aureus in both prostheses. Antibiotic solution showed the highest efficiency in inhibiting bacterial growth, especially for S epidermidis , in both washings. Lidocaine was able to reduce colonization by S aureus in post-contamination washing, showing that it can be used as an alternative adjuvant treatment in these cases.

Staphylococcus aureus biofilms have been recognized as a leading cause of multiple infections, including implant-associated infections and chronic wounds. We evaluated the colonization capacity of two distinct textured prostheses by different bacterial strains. Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Proteus mirabilis and Enterococcus faecalis were evaluated. Initially, the hydrophobicity and biofilm formation capacity were determined. Subsequently, 20 fragments of vascular prosthesis and 20 silicone prostheses were embedded in suspensions with the microorganisms and incubated. The prostheses were then sown in culture medium and incubated for 48 hours. Petri dishes were photographed and analyzed by fractal dimension. The Kruskal-Wallis test and the Dunn test were applied for the analysis of biofilm formation. To compare the mean intensity for the type of bacteria and the type of prosthesis, a general linear model was applied. Staphylococcus aureus was the bacterium with the highest colonization density in both prostheses (p = 0.0001). E. coli showed strong adherence in the biofilm formation capacity test (p = 0.0001), however, it did not colonize either prosthesis. We demonstrated that Staphylococcus aureus has a greater affinity for vascular and silicone prostheses than other bacteria.

Local anesthetics are commonly used in medicine and dentistryand have a low cost, but their action as a microbicidalagent is still controversial. This study aimed to evaluate the antimicrobial effects of lidocaine against bacteria thatmost commonly infect surgical wounds. We evaluated Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Proteus mirabilisand Enterococcus faecalis. The solutions tested were saline, chlorhexidine, lidocaine (solution and pure) and an antibioticsolution. The agar diffusion test was performedusingPetri dishes. The agar plates were made in duplicate and incubated in an oven at 37°C for 48h. Subsequently, the inhibition halos were measured.The plates tested with lidocaine (pure or solution) presented no inhibition halo. The antibiotic solution presented the largest inhibition halos for all the bacteria(p<0.05). Chlorhexidine formed an inhibition halo similar to that of the antibiotic solution for Escherichia coli(p>0.05). Lidocaine did not present an antimicrobial effect for any of thetested bacteria. However, the antibiotic solution and the chlorhexidine inhibited the growth of all bacteria.