Update on ATS Education Committee
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Transcript Update on ATS Education Committee
Bacterial infections secondary to
rhinovirus infection in COPD
exacerbations
Dr Patrick Mallia MD PhD
NIHR Clinical Lecturer
Imperial College London
Background
COPD is predicted to be the 4th leading cause of death worldwide
by 2030
Morbidity, mortality and health-care costs of COPD largely
determined by acute exacerbations
Most exacerbations are associated with respiratory infections and
both bacteria and viruses are commonly detected in exacerbations
Few studies have examined the role of dual viral/bacterial
infections in COPD exacerbations
Viral/bacterial infections in COPD
Country
Viruses
Bacteria
Co-infection
Reference
Australia
43%
23%
6.5%
Cameron et al.
Int. Care Med. 2006
Australia
29%
25%
8%
Pant et al.
Respirology 2009
Switzerland
51%
64%
11.5%
Kherad et al
Chest 2010
Australia
21%
30%
12%
Hutchinson et al.
Resp Med. 2007
Canada
31%
49%
13%
De Serres et al.
J Clin Virol 2009
UK
24%
76%
17%
Hurst JR et al.
AJRCCM 2006
Italy
48%
55%
25%
Papi et al.
AJRCCM 2006
13.2%
Viral/bacterial infections in COPD
Secondary bacterial infections may follow viral infections –
established for flu but not for other respiratory viruses such as
rhinoviruses
Symptomatic colds frequently precede exacerbations
Rhinovirus infection in vitro increases bacterial adherence to
epithelial cells. H.influenzae increases rhinovirus binding and
replication in vitro
Therefore studies using a single sampling time point cannot
determine the true prevalence of co-infection or the sequence of
infection
Experimental rhinovirus infection
as a model of COPD exacerbations
We have developed a model of COPD exacerbation using
experimental rhinovirus (RV) infection in carefully selected
volunteers
RV infection induced the features of a COPD exacerbation – lower
respiratory symptoms, airflow obstruction and airways
inflammation
Experimental Rhinovirus Infection as a Human Model of Chronic Obstructive Pulmonary Disease
Exacerbation. Am J Respir Crit Care Med, Mar 2011; 183: 734 - 742
This model provides a tool to examine interactions between RV and
bacterial infections
Study Protocol
Induced
sputum
Study days
-14
5
9
12
15
21
RV INOCULATION
DAY 0
DAILY SYMPTOM DIARY CARDS
3 groups:
1) COPD (GOLD stage II, FEV1 50 – 80% predicted) – N=30
2) Smokers (SMK) with normal lung function – N=28
3) Non-smokers (NS) – N=18
Rhinovirus infection successful in 20 COPD, 21 SMK and 11 NS
42
Results
Bacteria
(PPM)
COPD
SMK
NS
60%
9.5%
10%
P<0.001
Incidence of bacterial infection following experimental RV infection
Rhinovirus
infected
Not infected
COPD
SMK
NS
60%
9.5%
10%
20%
P=0.038
16.7%
P=NS
12.5%
P=NS
Bacterial infection in subjects not infected with rhinovirus
Time course of bacterial infection
*P<0.05 vs. baseline, #P<0.05 vs. SMK, †P<0.05 vs. NS
Comparison of time course of
bacterial and viral infections
7
***
Virus load
Bacterial load
***
4
6
Sputum virus load
(Log10 copies/mL)
3
5
4
2
3
*
2
1
Sputum bacteria load
(Log10 cfu/mL)
***
1
0
Baseline
0
5
9
12
15
21
42
Study time points
(days from inoculation)
Significant correlation between virus and
bacterial loads R=0.47, P=0.039
Antimicrobial peptides
Antimicrobial peptides (AMPs) play a key role in innate lung
defence against infections
Two AMPs with both antmicrobial and anti-protease activity –
secretory leukocyte protease inhibitor (SLPI) and elafin
Inverse relationship between bacterial infection and SLPI in
COPD but the direction of relationship undetermined
SLPI and elafin – relationship
to bacterial infection in COPD
*P<0.05 vs. baseline, †P<0.05 vs. bacteria +ve COPD subjects
SLPI levels on day 12 and elafin levels on day 9 correlated
inversely with bacterial load (r=-0.51, P=0.023 and r=-0.71,
P=0004 respectively)
Neutrophil elastase degrades SLPI and elafin
High neutrophil numbers and neutrophil elastase levels
occur in bacteria +ve COPD subjects only
Conclusions
Bacterial infection is common following RV infection in COPD
There is a gap of 6-10 days between the peak of virus infection and
secondary bacterial peak
Reduced levels of SLPI and elafin in sputum are associated with
secondary bacterial infection in COPD and may be related to high
sputum levels of neutrophil elastase
Antiviral drugs may not only be effective against virus-induced
exacerbations but also reduce secondary bacterial infections
Acknowledgements
J Footitt, R Sotero, M-B Trujillo-Toralbo, T Kebadze, J
Aniscenko, G Oleszkiewicz, S Elkin, OM Kon, I Adcock, P
Barnes, Professor SL Johnston
Microbiology Laboratory Imperial College Healthcare NHS
Trust – Dr A Jepson, S Philip
Academy of Medical Sciences/Wellcome
NIHR