The Sensitivity of Opportunistic Bacteria to Blood Serum Low-Molecular Fraction Containing Antimicrobial Peptides and Proteins.

We studied the sensitivity of clinically significant (opportunistic) bacteria to blood serum fraction with a molecular weight <100 kDa containing antimicrobial peptides and proteins. The degree of damage to cytoplasmic membranes of bacterial cells was assessed by a spectrophotometric method. A total of 129 bacterial isolates belonging to 46 species, 19 genera, 13 families, 8 orders, 4 classes, and 3 types were studied. The mean sensitivity varied from -5.2 to 36.6%. The sensitivity depends on the structure of bacterial cell wall: higher sensitivity was demonstrated by taxonomic ranks related to gram-negative bacteria (median 19.1%) and lower values were observed in gram-positive bacteria (median 9.3%) (p<0.01). Among all orders, Lactobacilliales showed the lowest sensitivity (3.6%). Ranking of the studied species by their sensitivity showed that 7 of the first 15 species with sensitivity >19% are among to the leading causative agents of sepsis.