Hydrophobicity and adhesion of bacterial growth under varying temperature-time environment and material surface have been studied. Bacterial isolates were identified by standard methods of classification. Hydrophobicity index was assessed by microbial adhesion to hydrocarbon (MATH) utilizing absorbance at 520 nm; and adhesion by measuring crystal violet absorbance at 570 nm for various times (1,8,24 H), temperatures (5,25,40ºC) and material surfaces (PS,PP,PTFE). The results of P. aeruginosa and S. aureus showed a strong - moderate level of hydrophobicity at 40ºC in comparison to S. marcescens at a low level. In the adhesion assays to plastic materials, P. aeruginosa and S. aureus showed more adherence than S. marcescens and following the order as Teflon<polypropylene<polystyrene for all time-temperature range studied. Our results explain that the adhesion mechanism is governed by the triad interaction bacteria environment material surface, each of which contributes its attribute that when optimum conditions are favorite lead up to infection.
Gram +/- Bacteria, Temperature; Hydrophobicity, Adhesion, Biomaterial,
Serratia marcescens is a Gram-negative and mesophilic microorganism found in water, soil, plant, and animals; it is transmitted by direct contact and via saline solutions. Their resistive infections are normally treated with specialized formula antibiotics . Now it is infamous for its pathogenicity to hospital patients but there are many reports on the contamination of medical devices and nosocomial infections with this bacterium . Pseudomonas aeruginosa is a Gram negative and mesophilic strain that frequently causing nosocomial infections of patients with reduced immunity and association with infections and are usually very tough to eradicate . Staphylococcus aureus is a Gram positive and mesophilic microorganism commonly associated with contamination caused by foreign body material implants as in catheter-related infection .
Adhesion to surfaces by bacteria and other microorganisms tend to follow a survival pattern in the colonization of surfaces . Initially the growth which is a thermodynamic process is mediated by diad interactions covering physical/chemical factors which also depend on the presence of nutrient that bring about growth for the bacterial colonization . Virulence factors in the bacterial adhesion depend on the physical nature of the biomaterial surface that meet the body as in the case of various implants [7,8].
Temperature is an abiotic factor that dramatically influence the efficacy of adhesion and to some extent on the hydrophobicity of bacteria / surface interface . Tanaka Y, et al. (2004) reported that S. marcescens and other bacterial species have unusual bacterial characteristic that is, temperature- dependent to bacteriostatic activity and observed that higher environment temperatures S. marcescens suppress its own growth and the growth of other bacteria . Material surfaces that meet microorganisms lead to the formation of biofilm by the initiation of bacterial adhesion to surfaces, a phenomenon governed by the triad interaction of physicochemical properties of the bacteria, environment and biomaterial characteristics. The main factors involved in polymeric surfaces are hydrophobicity and charge; thus negatively charged surfaces when in contact with negatively charged bacteria lead to electrostatic repulsion . Most used polymers as biomaterials are polystyrene PS, polyethylene PE, polypropylene PP, polyurethane PU, polyethylene terephthalate PET, polytetrafluoroethylene PTFE (Teflon) and polymethylmethacrylate PMMA (Perspex). As seen from the highlights the importance of these interactions as a functional bacterial growth parameters that this work is intended to investigate the influence of environmental factors (variation in growth time and growth temperature) and material surface factors on hydrophobicity and adhesion of P. aeruginosa, S. marcescens and S. aureus cultured on different polymeric surfaces (PS, PP and PTFE).