Susceptibility of Invasive compared with Respiratory Streptococcus pneumoniae

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Susceptibility of Invasive compared with
Respiratory Streptococcus pneumoniae
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Question How do patterns of resistance compare
in S. pneumoniae from blood and S. pneumoniae
from community-acquired lower respiratory
infections?
R. Reynolds, D. Felmingham, D. Livermore BSAC
Working Party on Resistance Surveillance
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BSAC Respiratory Resistance Surveillance Programme

• 20 laboratories over UK and Ireland
• winter seasons (October-April, 1999 - 2002)
• community-acquired infection (patients in
  hospital gt 48 hours excluded)
• duplicate isolates within 2 weeks excluded
• cystic fibrosis excluded
• central testing, BSAC agar dilution MIC

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BSAC Bacteraemia Resistance Surveillance Programme

• 25 laboratories over UK and Ireland
• calendar years (2001, 2002)
• duplicate isolates within 1 week excluded
• 12 organism groups (6 Gram-positive, 6
  Gram-negative)
• central testing, BSAC agar dilution MIC

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Acknowledgements

• COLLECTING LABORATORIES
• CENTRAL LABS - GR Micro Ltd., London Health
  Protection Agency, London
• SPONSORS
• Abbott Aventis Bayer GSK
• MSD Pharmacia Wyeth

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There are differences in demographics between the
two programmes. Source of infection and country
may affect resistance rates, so it is not
sufficient to do a simple comparison of
resistance rates between bacteraemia and
respiratory isolates.
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Despite the very similar median ages, there is a
distinct difference in the age distribution of
patients in the two programmes. This also may
affect resistance rates.
Age distribution of patients contributing S.
pneumoniae
p lt 0.001
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Respiratory S. pneumoniaeMultivariate Analysis
These three factors have been shown to be
significant predictors of resistance in a
multivariate analysis of respiratory S.
pneumoniae.
Revised Question Is there a similar relationship
of resistance with patient age in bacteraemia?

• Antimicrobial
• Country
• Resistance more prevalent in Ireland
• Age
• Resistance less prevalent in middle age groups

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There are reasonable numbers of isolates in all
groups, but note only 24 from bacteraemia
patients age 5-24. Therefore, do not focus too
much on that age group when looking at the
following graphs as resistance rates are likely
to vary more here than in older groups which have
larger numbers.
Numbers of Isolates
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Although the confidence intervals overlap, the
multivariate analysis of respiratory isolates
gives strong evidence that penicillin
non-susceptibility depends on age and that the
form of the relationship is U-shaped, as
illustrated here.
non-susceptibility to penicillin in respiratory
S. pneumoniae

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The bacteraemia S. pneumoniae show a similar
U-shaped dependence of resistance on age.
non-susceptibility to penicillin in bacteraemia
S. pneumoniae

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Similarly for erythromycin.
non-susceptibility to erythromycin in S.
pneumoniae


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And for tetracycline.
non-susceptibility to tetracycline in S.
pneumoniae


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Conclusions

• Susceptibility of S. pneumoniae is related to
  age the pattern is similar in respiratory and
  bacteraemia isolates.
• More detailed analysis is needed to separate the
  effects of different factors on susceptibility.
• Results are on www.bsacsurv.org