Biofilms have been classically visualized by Scanning Electron Microscopy (SEM). The complex operating procedure of SEM restricts its use in routine practice. There is a need of newer visualizing techniques for examining surfaces of biofilms, in particular under ambient conditions. We have presented the unique advantages of atomic force microscopy (AFM) in studying surfaces of biofilms through analyses of the height images obtained on biofilms of two gram positive and one gram negative bacteria, namely Staphylococcus aureus, Nocardia brasiliensis and Pseudomonas aeruginosa, respectively. Biofilm quality of the three different bacteria, ageing effects on Nocardia spp. biofilm surface and effects of the antibiotic ciprofloxacin at different doses on Staphylococcus and Pseudomonas biofilm surfaces have been investigated under ambient conditions and distinctive features have been observed.
Adherence of the microorganism to submerged solid surfaces leads to biofilm formation. Biofilm formation modifies the surfaces in favor of bacteria facilitating the survival of the bacteria under different stressed conditions. On the other hand, the formation of biofilm has a direct adverse economic impact in various industries and more importantly in medical practices. This adherence is the reason for the failure of many indwelling medical devices. Surface biofilm adhesion is the key to biofilm growth and stability. Hence this adhesion needs to be substantially lowered to inhibit biofilm stability. Both chemical and physical properties of the surface influence biofilm formation and modulating these properties can control this formation. In this study, we have investigated the effect of Hydrofluoric acid (HF), at a specific concentration as an etchant, on the surface morphology of substrates and the growth of biofilms of Pseudomonas aeruginosa . and Staphylococcus aureus . We find that the bacterial counts on the etched surfaces undergo a periodic increase and decrease. This, on one hand, shows the close correlation between the biofilm growth and the particular roughness scale, and on the other hand, explains the existing contradictory results regarding the effects of etching on substrate roughness and biofilm growth. We propose a simple model of a sequence of hole formation, hole expansion and etching away of the hole walls to form a new, comparatively smooth surface, coupled with the preferential accumulation of bacteria at the hole edges, to explain these periodicities.
Bacterial biofilms pose the greatest challenge to implant surgeries leading to device-related infections and implant failure. Our present study aims at monitoring the variation in the biofilm architecture of a clinically isolated strain and ATCC 27853 strain of Pseudomonas aeruginosa on two polymeric biomaterials, used in implants. The perspective of our study is to recognize the potential of these two biomaterials to create biofilm infections and develop the understanding regarding their limitations of use and handle patients with this deeper insight. The final goal, however, is an accurate interpretation of substrate-microbe interactions in the two biomaterials, which will provide us the knowledge of possible surface modifications to develop of an efficacious anti-biofilm therapy for deterring implant infections. The reference strain ATCC 27853 and a clinical isolate of P. aeruginosa collected from urinary catheters of patients suffering from urinary tract infections, have been used as microbes while clinical grades of polypropylene and high density polyethylene, have been used as ‘substrates’ for biofilm growth. The variation in the nature of the ‘substrate’ and ‘conditioning layer’ of BSA have been found to affect the biofilm architecture as well as the physiology of the biofilm-forming bacteria, accompanied by an alteration in the nature and volume of EPS (extracellular polysaccharide) matrices.Graphical Abstract Electronic supplementary materialThe online version of this article (doi:10.1007/s40204-017-0061-2) contains supplementary material, which is available to authorized users.
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