Health care-associated infections such as Pseudomonas aeruginosa bacteremia pose a major clinical risk for hospitalized patients. However, these systemic infections are presumed to be a "dead-end" for P. aeruginosa and to have no impact on transmission. Here, we use a mouse infection model to show that P. aeruginosa can spread from the bloodstream to the gallbladder, where it replicates to extremely high numbers. Bacteria in the gallbladder can then seed the intestines and feces, leading to transmission to uninfected cage-mate mice. Our work shows that the gallbladder is crucial for spread of P. aeruginosa from the bloodstream to the feces during bacteremia, a process that promotes transmission in this experimental system. Further research is needed to test to what extent these findings are relevant to infections in patients.
Background
Streptococcus pneumoniae infections in Taiwan mostly occur in children aged 2–4 years. Because of a significant increase in the incidence of serotype 19A-related infections, the 13-valent pneumococcal conjugate vaccine (PCV13) was initially introduced in the national immunization program for children 2–5 years of age, prior to the national programs for infants. We have assessed the impact of such vaccination programs in reducing the incidence of invasive pneumococcal disease (IPD) in Taiwanese children.
Methods
We analyzed the national data on IPDs from the Taiwan Centers for Disease Control between 2008 and 2017. We calculated the incidence rates of IPD and incidence rate ratios (IRRs) between years for different serotypes to estimate the effectiveness of the vaccination programs.
Results
The national catch-up primary vaccination schedule successfully reduced the incidence rate of IPD from 17.8/100 000 in 2012 to 5.5/100 000 in 2017 among children aged 0–5 years. The IRR (2017 over 2012) was 0.31, corresponding to a 69% reduction. A modest herd effect was also observed, with a 37% reduction in the incidence of IPD in elderly people (≥70 years) from 2012 to 2017. The incidence of IPD caused by serotype 19A in children aged 0–5 years was reduced by 32.6–44.3% yearly from 2012 to 2017. In 2015, serogroup 15 outnumbered 19A, to become the leading serotypes in children 0–5 years old.
Conclusions
Special catch-up vaccination programs starting from children 2–5 years of age with PCV13 have been highly effective in reducing the incidence of IPD, especially as caused by serotype 19A, in Taiwanese children.
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