Presence Of Bacterial Biofilms Research Articles

Intracellular antimicrobial activity appearing as a relevant factor in antibiotic efficacy against an experimental foreign-body infection caused by Staphylococcus aureus

The presence of bacterial biofilm, tolerance to antibiotics and dysfunctional activity of phagocytic cells are all related to difficulties in eradicating foreign-body infections. We aimed to quantify the presence of intracellular Staphylococcus aureus and to study the extent to which the intracellular activity of antibiotics might determine their efficacy against an experimental rat tissue-cage model of foreign-body infection. Using this model, animals were treated for 7 days with 100 mg/kg/day levofloxacin or 200 mg/kg/12 h cloxacillin, or were left untreated. Antibiotic efficacy was evaluated by means of bacterial counts from tissue-cage fluid (TCF); these counts were derived separately in total, intracellular and extracellular bacteria. The presence of intracellular bacteria was checked by electron microscopy. Population analysis was performed with surviving bacteria recovered at the end of levofloxacin therapy. Among a total number of bacteria (mean log cfu/mL +/- SD) from TCF of 6.86 +/- 0.6, we identified 6.38 +/- 0.8 intracellular bacteria and 5.57 +/- 0.5 extracellular bacteria. Levofloxacin was more efficient than cloxacillin (P < 0.05) against both intracellular and extracellular bacteria. The killing activity of levofloxacin against the intracellular population was higher than against the extracellular bacteria (P = 0.1). The frequency of levofloxacin-resistant mutants among surviving bacteria at the end of levofloxacin therapy was similar to that for the wild-type strain. Intracellular bacteria accounted for the largest proportion of the total inoculum in this model of foreign-body infection. The intracellular activity of an antibiotic seems to be an additional relevant factor in the antibiotic response to these infections.

Erosion from Staphylococcus aureus Biofilms Grown under Physiologically Relevant Fluid Shear Forces Yields Bacterial Cells with Reduced Avidity to Collagen

An estimated 65% of infective diseases are associated with the presence of bacterial biofilms. Biofilm-issued planktonic cells promote blood-borne, secondary sites of infection by the inoculation of the infected sites with bacteria from the intravascular space. To investigate the potential role of early detachment events in initiating secondary infections, we studied the phenotypic attributes of Staphylococcus aureus planktonic cells eroding from biofilms with respect to expression of the collagen adhesin, CNA. The collagen-binding abilities of S. aureus have been correlated to the development of osteomyelitis and septic arthritis. In this study, we focused on the impact of CNA expression on S. aureus adhesion to immobilized collagen in vitro under physiologically relevant shear forces. In contrast to the growth phase-dependent adhesion properties characteristic of S. aureus cells grown in suspension, eroding planktonic cells expressed invariant and lower effective adhesion rates regardless of the age of the biofilm from which they originated. These results correlated directly with the surface expression level of CNA. However, subsequent analysis revealed no qualitative differences between biofilms initiated with suspension cells and secondary biofilms initiated with biofilm-shed planktonic cells. Taken together, our findings suggest that, despite their low levels of CNA expression, S. aureus planktonic cells shed from biofilms retain the capacity for metastatic spread and the initiation of secondary infection. These findings demonstrate the need for a better understanding of the phenotypic properties of eroding planktonic cells, which could lead to new therapeutic strategies to target secondary infections.

Evidence of Bacterial Biofilms on Frontal Recess Stents in Patients with Chronic Rhinosinusitis

Bacterial biofilms have been documented on middle ear mucosa, tonsils, and cholesteatoma. We hypothesize that bacterial biofilms are present in mucosa of patients with chronic sinusitis. We believe that frontal sinus stents may serve as a reservoir for biofilms. We studied silicone frontal sinus stents removed from six patients 1 to 4 weeks after FESS with scanning electron microscopy (SEM). We identified evidence of bacterial biofilms on the frontal recess stents in six of six patients under SEM. Five of these patients had sinus cultures positive for Staphylococcus aureus. Bacterial biofilms were identified by evidence of glycocalyx, water channels, and three-dimensional structure. These images were similar to other images of known biofilms. This is evidence of the possible presence of bacterial biofilms on frontal sinus stents in patients with chronic sinusitis. Further study into the role of bacterial biofilms in perpetuating chronic sinusitis is warranted.

The role of bacterial biofilms in ocular infections.

There is increasing evidence that bacterial biofilms play a role in a variety of ocular infections. Bacterial growth is characterized as a biofilm when bacteria attach to a surface and/or to each other. This is distinguished from a planktonic or free-living mode of bacterial growth where these interactions are not present. Biofilm formation is a genetically controlled process in the life cycle of bacteria resulting in numerous changes in the cellular physiology of the organism, often including increased antibiotic resistance compared to growth under planktonic conditions. The presence of bacterial biofilms has been demonstrated on many medical devices including intravenous catheters, as well as materials relevant to the eye such as contact lenses, scleral buckles, suture material, and intraocular lenses. Many ocular infections often occur when such prosthetic devices come in contact with or are implanted in the eye. For instance, 56% of corneal ulcers in the United States are associated with contact lens wear. Bacterial biofilms may participate in ocular infections by allowing bacteria to persist on abiotic surfaces that come in contact with, or are implanted in the eye, and by direct biofilm formation on the biotic surfaces of the eye. An understanding of the role of bacterial biofilm formation in ocular infections may aid in the development of future antimicrobial strategies in ophthalmology. We review the current literature and concepts relating to biofilm formation and infections of the eye.

Adhesion formation, peritoneal effects, and the presence of bacterial biofilms

Adhesion formation, peritoneal effects, and the presence of bacterial biofilms

An atomic force microscopy study of the biodeterioration of stainless steel in the presence of bacterial biofilms

Atomic Force Microscopy (AFM), a technique requiring little or no preparation of biological samples prior to viewing and allowing observation of bacteria and bacterial expolymers in their hydrated forms, has been used to elucidate the phenomena of stainless steel corrosion due to the development of bacterial biofilms. Biofilms formed by pure and mixed cultures of Pseudomonas aeruginosa, the sulphate-reducing bacterium Desulfovibrio gigas and a consortium isolated from a corroding, cast iron pipe carrying potable water were grown for 7 and 14 days in batch cultures at 25°C on surfaces of stainless steel (316) coupons, polished to obtain a 1 μm finish. Surfaces with biofilms present and removed were examined by AFM and by scanning electron microscopy (SEM). The study revealed that the greatest deterioration of steel, in a form of pitting corrosion, occurred in the presence of an isolated pipe consortium. The degree of corrosion observed in mixed cultures of P. aeruginosa and D. gigas was higher than that recorded in pure cultures of these bacteria. The advantage of using AFM as a qualitative method of biocorrosion assessment and its potential for quantitative analysis of microbially influenced corrosion are emphasised.