Pathological Evaluation of Staphylococcal Fatty Acid Modifying Enzyme (FAME) and Lipase on Abscess Production by Non- Abscess ProducerStaphylococci in Sheep

Abstract

This work was carried out to explain the role of FAME and lipase in survival and multiplication of the organism in the host tissues and the induction of abscess by non abscess-producer Staphylococci treated with FAME and/or lipase and also to study the effect of triglycerides on abscess formation. Staphylococcus aureus (S. aureus)subsp. anaerobiusand S. epidermidiswere isolated from sheep abscess for extraction of FAME and lipase respectively by culturing themon trypticase soy broth medium. Thirty-nine sheep, divided into nine groups of three animals each, were inoculated subcutaneously (S/C) with different protocols and doses. Inocula included: S. epidermidisplus FAME; or plus FAME and lipase;S. warneriplus FAME or plus FAME and lipase; or plus lipase alone; S. aureus subsp. anaerobiusplus triglyceride; or plustriglyceride and lipase; or plus triglyceride and FAME. The control groups (six groups of two animals each) were inoculated with the enzymes FAME and lipase, triglycerides and the test bacteria (S. aureus subsp. anaerobius, S. epidermidis and S. warneri). Necropsy of the experimental sheep revealed the presence of abscesses at the sites injected with S. epidermidisand S. warneriwhen treated with FAME or with both FAMEand lipase and also at sites where S. aureus subsp. anaerobiuswas inoculated. No abscesses were formed at sites injected with S. epidermidisor S. warnerialone or S. warneri plus lipase. Triglycerides were found to inhibit the formation of abscess when injected with abscess-producer Staphylococci (S. aureus subsp. anaerobius), but when FAME or lipase was also added, abscess was formed again. 14 Sections prepared from sites injected with bacteria and the enzymes FAME and lipase showed the presence of abscesses characterized by neutrophils infiltration surrounded by fibrous tissue reaction. At places chronic inflammatory cells (mainly macrophages), fibroplasia and pyogranulomas were seen. The tissue changes were more pronounced at sites where S. epidermidiswas injected with FAME and lipase, followed by inoculation sites of S. epidermidisplus FAME, and S. aureus subsp. anaerobiusalone or when triglycerides were added to it with FAME or lipase. Sites injected with S. aureus subsp. anaerobiusplus triglycerides showed slight inflammatory reaction. To the best of our knowledge this in vivo experimental study seems to be the first of its type.