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Protective effect of Lactobacillus casei on Pseudomonas aeruginosa infection in mice
Abstract:
The protective effect of heat-killed Lactobacillus casei YIT9018 (LC 9018) against Pseudomonas aeruginosa infection in mice was compared with that of Corynebacterium parvum. Survival of mice after intraperitoneal (i.p.) infection with P. aeruginosa was augmented in mice that had been pretreated i.p. with LC 9018 5 days previously. Similar treatment of mice with C. parvum, however, was not effective at all. Moreover, mice became more susceptible to infection with P. aeruginosa after such treatment. Growth of P. aeruginosa in the peritoneal cavity and spleen was markedly inhibited in LC 9018-pretreated mice, whereas such inhibition of bacterial growth was not observed in C. parvum-treated mice. The protective effect of LC 9018 was observed in mice subjected to 800 rads of whole body irradiation but was abrogated when mice were treated with carrageenan. These results suggest that augmentation of the resistance of mice to P. aeruginosa was caused by the induction of activated macrophages. The number of macrophages detectable in the peritoneal cavity was almost the same in LC 9018- and C. parvum-treated mice. Growth of Listeria monocytogenes was inhibited by pretreatment with LC 9018. Inhibition of L. monocytogenes was also observed after the same pretreatment with C. parvum. It was suggested that macrophages activated with LC 9018 were involved in the protective immunity to P. aeruginosa.
Insights
Heat-killed Lactobacillus casei YIT9018 (LC 9018) enhances mouse survival against Pseudomonas aeruginosa infection by activating macrophages. Corynebacterium parvum showed no protective effect and increased susceptibility.
Area of Science:
- Immunology
- Microbiology
- Bacterial Infections
Background:
- Pseudomonas aeruginosa is an opportunistic pathogen causing severe infections.
- Lactobacillus casei YIT9018 (LC 9018) and Corynebacterium parvum are known immunomodulators.
- Understanding protective mechanisms against P. aeruginosa is crucial for developing effective treatments.
Purpose of the Study:
- To compare the protective effects of heat-killed LC 9018 and C. parvum against P. aeruginosa infection in mice.
- To investigate the role of activated macrophages in the observed protective immunity.
Main Methods:
- Mice were pretreated with LC 9018 or C. parvum before intraperitoneal challenge with P. aeruginosa.
- Bacterial growth in the peritoneal cavity and spleen was measured.
- The effect of irradiation and carrageenan treatment on LC 9018's protective effect was assessed.
- Macrophage activity and Listeria monocytogenes growth were also evaluated.
Main Results:
- LC 9018 pretreatment significantly increased mouse survival against P. aeruginosa infection.
- LC 9018 inhibited P. aeruginosa and Listeria monocytogenes growth in vivo.
- C. parvum did not provide protection and increased susceptibility to P. aeruginosa.
- The protective effect of LC 9018 was dependent on macrophage activation, as shown by carrageenan treatment abrogating the effect.
Conclusions:
- Heat-killed Lactobacillus casei YIT9018 (LC 9018) confers significant protection against Pseudomonas aeruginosa infection in mice.
- The protective immunity induced by LC 9018 is mediated by activated macrophages.
- Corynebacterium parvum is ineffective and potentially detrimental in this context.