Atividade antagonista de Bacteroides fragilis

Abstract

The genus Bacteroides includes Gram negative rods, obligate anaerobes, considered to be as members of the indigenous microbiota of humans and other animals. They are often recovered from infectious processes, mainly of intra-abdominal origin. Among Bacteroides species, Bacteroides fragilis should be highlighted considering that it is commonly recovered from clinical specimens, expresses several virulence abilities and frequently exhibits antimicrobial resistance. The ability to synthesize bacteriocins is widely spread among bacteria. We aimed to evaluate the expression of antibacterial activity by B. fragilis, including the investigation of the antagonistic activity spectrum and the extraction of a proteinaceous antagonistic substance. Antagonistic expression was evaluated by the double layer method. A total of 19 bacterial isolates, members of the intestinal microbiota or enteropathogens were included as indicator strains. Among the 57 tests conducted nine gave positive results. Isoantagonistic and heteroantagonistic activity were detected. One of the three test strains, B. fragilis D51, was selected for further steps of the investigation. Interfering factors were excluded suggesting the expression of a bacteriocin. The producer strain was submitted to protein extraction and among the intracellular fractions obtained only C30 expressed antagonistic activity (800 AU/mL). C30 lost its activity following treatment with proteinase K confirming its proteinaceous nature. Taken into consideration the relevance of the theme as well as the scarcity of data regarding this subject we believe that this investigation should be continued in order to allow a better understanding about B. fragilis virulence and bacteriocins relevance.