EuroPneumo Special Issue / pneumonia 2015 Oct 21;7:I–72


Evaluation of Streptococcus pneumoniae respiratory infection in mice

with different susceptibility for acute inflammatory responses

Rúbia Isler Mancuso 1 , Alessandra Soares-Schanoski 1 , Eliane Namie Miyaji 1 , Paulo Lee Ho 1, 2 ,

Orlando Garcia Ribeiro 3 , Maria Leonor Oliveira 1


Centro de Biotecnologia - Instituto Butantan, São Paulo, Brazil; 2 Divisão de Desenvolvimento Industrial e Produção - Instituto Butantan, São Paulo,

Brazil; 3 Laboratório de Imunogenetica - Instituto Butantan, São Paulo, Brazil

Acute inflammation is an important response against bacterial infections. Here, an invasive respiratory challenge model

with a Streptococcus pneumoniae serotype 3 strain was studied in two outbred mice lineages, genetically selected for

exacerbated (AIRmax) and low (AIRmin) acute inflammatory responses. A dose of 10 4 bacteria per animal induced the

death of 100% of AIRmin mice a few days after the challenge. In contrast, only 36.4% of AIRmax mice died after the

infection. Bacterial numbers in the airways of AIRmax mice at 48 h post-challenge were significantly lower than the

observed in AIRmin mice. Analysis of cytokines in bronchoalveolar lavage fluids, showed peaks of IFN-γ and IL-6 at 12 h

post-challenge for AIRmax mice, and significant increases in IL-4, IL-5 and IL-10, at the same time point, for AIRmin mice.

No differences were observed for IL-1β, KC or IL-17, when comparing the 2 mice strains. The profile of TNF-α response

after the challenge was similar in the 2 mice strains; however, the levels of this cytokine remained high for AIRmin mice

at later time points. Preliminary analysis showed no differences in the percentage of alveolar macrophages expressing

the CD206 mannose receptor (F4/80+ CD11c+, CD206+), for both mice strains, before or 6 hours post-challenge.

However, a significant increase in the expression of CD206 by these cells (measured by the mean fluorescence intensity)

was observed in AIRmin mice at 6 hours post-challenge. Further analysis on the role of these cells in the outcome of

pneumococcal infection in this model is underway.


Stable niche adaptation within clonal lineages of Streptococcus


Zarina Amin, Claudia Trappetti, Bart Eijkelkamp, Catherine Hughes, Richard Harvey, Christopher

McDevitt, Adrienne Paton, James Paton

University of Adelaide, Adelaide, Australia

Individual Streptococcus pneumoniae strains differ markedly in their virulence phenotypes, but genetic heterogeneity

has complicated attempts to identify any association between a given clonal lineage and propensity to cause a particular

disease type. Previously we reported that serotype 3 pneumococci of the same ST-type exhibit distinct in vitro and in

vivo phenotypes in accordance with clinical site of isolation. In this study, serotype 14 blood and ear isolates of the same

ST-type (ST15) were investigated for pathogenic phenotype. In a murine intranasal challenge model, the three blood

and two ear isolates colonised the nasopharynx to similar extents. However, they exhibited significant differences in

bacterial loads in other host niches. At 24 and 2 hours post-challenge, neither of the ear isolates was detectable in the

lungs of any of the mice, but the blood isolates were present in the lungs of the majority of mice at both time points.

None of the three ST15 blood isolates were detected in the brains of any mice at either time point. However, the ear

isolates were detected in the brains and ear compartment of most of the mice at both 24 hours and at 72 hours. Thus,

stable niche adaptation within a clonal lineage appears to be a general property of pneumococci. Interestingly, both

blood and ear isolates were present in the lungs at similar levels at 6h post-infection, suggesting early immune responses

may underpin the distinct virulence phenotypes. Transcriptional analysis of lung tissue from mice infected for 6 hours

with blood versus ear isolates using RT-PCR arrays of key immune response genes revealed 8 differentially expressed

genes. Two of these were exclusively expressed in response to infection with the ear isolate. These results suggest a link

between differential capacity to elicit early innate immune response and the distinct virulence phenotypes of clonally

related S. pneumoniae strains.

pneumonia 2015 Volume 7


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