Detection of Teichoic Acid and Lipoteichoic acid in Staphylococcus Aureus pneumonia.

Kharkiv National Medical University

Department of microbiology and virology

Lupai E., Gramatyuk S.

Cases of rapidly progressive and fatal staphylococcal pneumonia still occur. This is a rapidly progressive disease. Patients with primary staphylococcal pneumonia present with a short prodrome of fever followed by rapid onset of respiratory distress, which may include tachypnea, retractions, and cyanosis. Patients may also have prominent GI tract symptoms. Staphylococcal pneumonia may also develop after influenza infection, which seems to occur preferentially among young adults (in whom mortality reaches 50%). In adults, 60%-87% of pneumococcal bacteremia is associated with pneumonia. The primary form occurs without an extrapulmonary focus, presumably through direct inoculation to the lungs, and the secondary form results from hematogenous seeding of the lungs during endocarditis or bacteremia. Skin-colonizing gram-positive bacteria produce wall teichoic acids (WTAs) or related glycopolymers for unclear reasons. Staphylococcus aureus is an important pathogen in nosocomial pneumonia. Lipoteichoic acid (LTA) are part of the staphylococcal cell wall.

Materials and Methods

Isolation of teichoic acid. Teichoic acid was isolated from the cell walls of Staphylococcus aureus Wood 46. The strain was obtained from the Bacterial Culture Museum of the Cathedra of Microbiology and Medical Clinic held №4 in Kharkov, Ukraine. The preparation was isolated by the method of Archibald.

Results

We show here that concentration of teichoic acids plays a pivotal role in the initial step of biofilm formation. The cell surface of S. aureus as in most bacteria, has a moderately negative net charge at neutral pH, which is probably due to the fact that the teichoic acids contain fewer positively charged d-alanine residues than negatively charged phosphate groups. The direct interaction of bacteria and surfaces is dependent on van der Waals forces, which are generally attractive, and interionic forces, which can be either attractive or repulsive. Even if bacteria and surfaces are charged alike, van der Waals forces can overcome repulsion and lead to adhesion. The much stronger probably leads to a pronounced increase in the repulsive forces, thereby disabling any adherence of the bacteria to polystyrene or glass.

On the other hand, altered concentration teichoic acid may affect the adhesive properties of bacterial cells in an indirect way. For instance, decreased concentration teichoic acids has been shown to alter the folding of exoproteins in Bacillus subtilis. Although the pattern of cell wall-associated proteins was only slightly different in the S. aureus, altered protein conformations might lead to altered physicochemical properties of the cell surface and thereby compromise the interaction with artificial surfaces.

Our data suggest that increasing the repulsive forces between the plastic surface and the bacteria by modifying the properties of implanted materials may lead to reduced capacity to form a biofilm. Moreover, since the concentration teichoic acid content vary among S. aureus strains, increased amounts of teichoic acid may contribute to the capacity of staphylococci to colonize indwelling devices.