Non-starved mucoid Pseudomonas aeruginosa isolates cause a high death rate in strains of mice.

Pseudomonas aeruginosa is an opportunistic pathogen that affects many patients in a hospital setting as well as immunocompromised patients. Pseudomonas aeruginosa is resistant to many antibiotics because of the formation of biofilms and pigmentations serving as virulence factors. Pseudomonas aeruginosa isolates are either mucoid or alginate-producing and non-alginate-producing (non-mucoid) isolates. The main objective of this experiment was to analyze the pathogenicity of mucoid and non-mucoid isolates in P. aeruginosa in a mouse model. We hypothesized that mucoid isolates are more pathogenic compared to non-pathogenic ones. Pseudomonas aeruginosa isolates PAO1 (non-mucoid) and 2192 (mucoid) were used intranasally to infect and monitor mortality rates. Isolates starved in water for at least three months were tested for infectivity. The mucoid isolate 2192 showed a 67% death rate compared to 33% of PAO1, suggesting the mucoid is more pathogenic to BALB/c mice than the non-mucoid PAO1. The death rate of mice infected with strain DBA susceptible to P. aeruginosa infection was higher than that of the BALB/c strain. The results also suggest that non-starved bacteria are more pathogenic to mice than starved bacteria. We extend our study by infecting mouse strains under hindlimb-unloading (HU) conditions with P. aeruginosa mucoid and non-mucoid isolates. Our results show that HU conditions enhance infection, suggesting the effect of stress and physiological changes could lead to susceptibility to infection. Our data indicate that the mucoid isolate is more likely to kill all mouse strains.