Atypical behaviour and survival ofStreptococcus pyogenesL forms during intraperitoneal infection in rats

Abstract

Groups of rats were injected intraperitoneally with cell wall-deficient (L) forms of Streptococcus pyogenes, with their parental (S) forms, as well as with a combined inoculum of both forms (S+L). Peritoneal exudate samples were harvested on days 1, 3, 7, 15 and 30 after challenge and were investigated by microbiological, electron microscopic, cytometric and biochemical methods. Parental S forms were isolated from peritoneal exudate samples up to day 15 post infection, while L form cultures were isolated until the end of the examined interval. Electron microscopic examination revealed continuous adhesion of L forms on the macrophage surface as well as intracellular persistence inside them. It was demonstrated that the intraperitoneal inflammatory response to L form infection was higher than to the other infections and the monocyte-macrophage populations were predominant. The established atypical behaviour and long survival of S. pyogenes L forms in the rat's peritoneum could explain some of the mechanisms of the pathogens' persistence as well as the reasons for chronic streptococcal infections.

Cell-wall deficient L. monocytogenes L-forms feature abrogated pathogenicity

“…Unfortunately, next to nothing is known about the expression of virulence genes in L-form bacteria, or the recognition of the wall-less cells by the immune system. This is intriguing, in particular in regard to numerous studies on experimental infections claiming a possible role for L-forms in diseases such as endocarditis, rheumatic fever, Crohn's disease, sarcoidosis, septicemia, urinary tract infections, or chronic gastritis (Owens, 1987; Markova et al, 1997; Michailova et al, 2000, 2007). However, direct evidence for a role of L-forms in disease is still missing, as re-isolation from an infected host has not yet been reported (Onwuamaegbu et al, 2005).…”

Filterable forms and L-forms ofMycobacterium bovisBCG

“…As far as cell wall deficiency facilitates the bacterial survival under unfavorable conditions, L-forms of different bacterial species have been shown to survive and persist for an extended period in vivo. [24][25][26][27] Of all bacteria, L-forms predominate and are crucial to the survival of mycobacteria in vivo. 6,9,20 Occurrence of M. bovis BCG L-forms inside macrophages has been observed with behavior and features of live BCG vaccine.…”

“…It may be suggested that prolonged non-specific irritation of the immune system by L-forms could become a reason for side effects of allergic or autoimmune origin. [24][25][26][27] Having in mind all unusual properties of L-forms, the presence of viable filterable L-form elements in commercial BCG vaccine can be evaluated as risk factor for vaccine safety in view of possible unpredictable adverse events. This specific insight on properties of vaccine strains needs to be taken into account when developing of new viable mycobacterial vaccines.…”