Pathophysiology of in-vitro induced filaments, spheroplasts and rod-shaped bacteria in neutropenic mice

Abstract

This study compared the in-vitro properties and in-vivo effects of Escherichia coli filaments, spheroplasts and normal cells in a murine thigh infection model. E. coli was exposed to ceftazidime, meropenem or saline to obtain filaments, spheroplasts or normal bacilli, which were then injected into neutropenic mice. After 24 h, morphology, CFUs, local and circulating endotoxin levels, cytokine levels and mortality were recorded, and correlations between bacterial and host parameters of infection were investigated. Filaments and spheroplasts contained more endotoxin/CFU than controls. Histological studies showed that morphologically altered bacteria changed into rod-shaped cells in the absence of antibiotics. Bacterial spread to the liver was significantly higher in mice challenged with rod-shaped cells, compared with antibiotic-exposed bacteria (p 0.007). Muscle endotoxin levels correlated significantly with circulating interleukin (IL)-6 and tumour necrosis factor (TNF)-alpha, and both pro-inflammatory cytokines were correlated significantly (p 0.011). Despite a tendency toward higher local and systemic concentrations of endotoxin in the filament group, inflammatory responses and survival did not differ between groups. It was concluded that morphologically altered bacteria contain more endotoxin and can regain a rod shape after withdrawal of antibiotics, while non-antibiotic-exposed bacteria show greater spread to the liver. There was a clear intra-individual relationship between local endotoxin, systemic endotoxin, TNF-alpha and IL-6 production, but these parameters did not differ among groups.

Extract of Alpinia officinarum Suppresses Enteropathogenic Escherichia coli (EPEC) Lipopolysaccharide (LPS) Induced Inflammation in J774 A.1 Macrophages

“…Furthermore, the spheroplasts regained rod shape when the antibiotic was withdrawn. 16) This supports our hypothesis that endotoxins or LPS as such can induce high levels of TNFα and other proinflammatory cytokines. This could also possibly explain the reason for persistent diarrhea that is typical of an EPEC infection.…”

Concentration-dependency of β-lactam-induced filament formation in Gram-negative bacteria

“…At low concentrations, this may reflect filament formation rather than bacterial killing. This observation is explained by the fact that even large filaments count as 1 CFU [2,3,30–32]. Most isolates produced large filaments (more than ten cell lengths) at a certain dose range, but only short filaments were encountered in Klebsiella spp., and some isolates did not produce filamentous forms at all.…”

“…Binding of β‐lactam agents to PBP‐3 results in the formation of filaments, caused by the inability of bacteria to septate after doubling of their cell mass. Filaments are long strands of non‐dividing bacteria that contain enhanced quantities of endotoxin [2,3]. The mechanism by which the endotoxin content is enhanced is still unclear [4,5].…”

Lipopolysaccharide inhibits myogenic differentiation of C2C12 myoblasts through the Toll-like receptor 4-nuclear factor-κB signaling pathway and myoblast-derived tumor necrosis factor-α

“…Whether and how LPS affects myogenesis regulatory factors is unknown. Since TLR4 is expressed in skeletal muscle [39–41] and circulating LPS can reach peripheral tissues [42], we hypothesized that LPS might perturb both positive and negative regulatory factors via TLR4–NF-κB signaling in differentiating myoblasts, thereby suppressing muscle regeneration.…”