Modification of physico-chemical surface properties and growth of Staphylococcus aureus under hyperglycemia and ketoacidosis conditions

Diabetes is a widely spread disease affecting the quality of life of millions of people around the world and is associated to a higher risk of developing infections in different parts of the body. The reasons why diabetes enhances infection episodes are not entirely clear; in this study our aim was to explore the changes that one of the most frequently pathogenic bacteria undergoes when exposed to hyperglycemia and ketoacidosis conditions. Physical surface properties such as hydrophobicity and surface electrical charge are related to bacterial growth behavior and the ability of Staphylococcus aureus to form biofilms. The addition of glucose made bacteria more negatively charged and with moderate-intermediate hydrophobicity. Ketone bodies increased hydrophobicity to approximately 75% and pathological concentrations hindered some of the bacterial surface charge by decreasing the negative zeta potential of cells. When both components were present, the bacterial physical surface changes were more similar to those observed in ketone bodies, suggesting a preferential adsorption of ketone bodies over glucose because of the more favorable solubility of glucose in water. Glucose diabetic concentrations gave the highest number of bacteria in the stationary phase of growth and provoked an increase in the biofilm slime index of around 400% in relation to the control state. Also, this situation is related with an increase of bacterial coverage. The combination of a high concentration of glucose and ketone bodies, which corresponds to a poorly controlled diabetic situation, appears associated with an early infection phase; increased hydrophobic attractive force and reduced electrostatic repulsion between cells results in better packing of cells within the biofilm and more efficient retention to the host surface. Knowledge of bacterial response in high amount of glucose and ketoacidosis environments can serve as a basis for designing strategies to prevent bacterial adhesion, biofilm formation and, consequently, the development of infections.

Therapeutic applications of lysostaphin against Staphylococcus aureus

Staphylococcus aureus, an opportunistic pathogen, causes diverse community and nosocomial-acquired human infections, including folliculitis, impetigo, sepsis, septic arthritis, endocarditis, osteomyelitis, implant-associated biofilm infections and contagious mastitis in cattle. In recent days, both methicillin-sensitive and methicillin-resistant S. aureus infections have increased. Highly effective anti-staphylococcal agents are urgently required. Lysostaphin is a 27 kDa zinc metallo antimicrobial lytic enzyme that is produced by Staphylococcus simulans biovar staphylolyticus and was first discovered in the 1960s. Lysostaphin is highly active against S. aureus strains irrespective of their drug-resistant patterns with a minimum inhibitory concentration of ranges between 0·001 and 0·064 μg ml^-1 . Lysostaphin has activity against both dividing and non-dividing S. aureus cells; and can seep through the extracellular matrix to kill the biofilm embedded S. aureus. In spite of having excellent anti-staphylococcal activity, its clinical application is hindered because of its immunogenicity and reduced bio-availability. Extensive research with lysostaphin lead to the development of several engineered lysostaphin derivatives with reduced immunogenicity and increased serum half-life. Therapeutic efficacy of both native and engineered lysostaphin derivatives was studied by several research groups. This review provides an overview of the therapeutic applications of native and engineered lysostaphin derivatives developed to eradicate S. aureus infections.