Community Acquired Pneumonia Dr Vincent Ioos Medical Intensive
Care Unit Pakistan Institute of Medical Sciences
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Definition Infection of the lung parenchyma that has been
acquired in the community Before hospital admission or within 48
hours hospital acquired pneumonia, health care associated pneumonia
acute bronchitis and exacerbation of COPD obstructive pneumonia,
TB
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Diagnosis Lack of sensitivity of clinical signs and symptoms
But good Positive Predictive value of the presence of crakles Good
Negative Predictive Value of RR>30/mn, HR>100/mn, T>37,9C
Fever frequently absent in older patients CXR Leucopenia : poor
prognosis Microbiological diagnosis : better treatment when
pathogen oriented but contreversies on the value of tests
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Should we get a CXR ? Patient with severe infection : presence
of pneumonia allows proper empiric antibiotic therapy If patient is
not severely ill : helps in deferentiating CAP from acute
bronchitis or exacerbation of COPD, and assess if antibiotics are
necessary or not
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Which pathogens ?
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Epidemiology Varies from one country to another 2 questions :
Pathogens most likely to be responsible for CAP Pattern of
resistance, especially for Streptoccus Pn. Epidemiological studies
difficult : previous use of antibiotics, cost of C/S and
serological studies, invasive procedures. Sentinel surveillance
systems for specific pathogens : data from microbiology
departments, from disease oriented register.
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Etiology Outpatients
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Etiology ward patients
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Etiology ICU patients
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In Pakistan Lack of datas Neighbooring countries World
surveillance networks Peadiatric studies
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Shimia, Himachal Pradesh, India 70 patients with CAP, blood,
sputum and pleural fluid c/s, Mycoplasma Pn. Ab 75,6 % proven
etiology Streptococcus Pn 35,8% Klebsiella Pn 22% Staphylococcus
Aureus 17% Mycoplasma Pn 15% E. Coli 11% Beta hemolytic
Streptococci 7,5% GNB 5,9% Bansal S, Indian J Chest Dis Allied Sci.
2004, Jan-March ; 46(1) : 17-22
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New Delhi All India Institute of Medical Sciences, April 1997
December 1998 60 patients : blood C/S + Elisa Ab against L.
Pneumophila (serogroups 1-7) 13% conventional bacterial etiology
15% serological evidence of recent infection with L. Pneumophila
Chaudhry R, Trop Doct. 2000 Oct ; 30(4):197-200.
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Shangai 389 patients with CAP between 2001-2003 Bacterial
culture, PCR, specific immunological assays Specific pathogen found
in 39,8% : Haemophilus Inflenzae 51%, among them 88,3% amoxicilline
S Mycoplasma Pn. 27% Chlamydia Pn. 11% Klebsiella spp. 10%
Streptococcus Pn. 8% among them 75% Peni S, 25%Peni I
Staphylococcus Aureus 4% Legionella Pn. 1,3% Moraxella Catharallis
0,6% Huang HH, Eur J Clin Microbiol Infect Dis. 2006 Jun ;
25(6):369-74
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Iran, Afghanistan PubMed : country name + pneumonia, Iran : 33
articles, no epidemiological data on CAP Afghanistan : 12 articles,
one on epidemiology datas on CAP in Russian Soldiers
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Hoban DJ, Clin Infect Dis. 2001 May 15;32 Suppl 2:S81-93. 66
Laboratories in 1997, 81 in 1998 (17 in Asia-Pacific) Pneumococal
isolates from bloodstream and respiratory tract infections 8252
respiratory tract isolates
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Network of microbiology departments in 26 countries 1998-2000
Streptococcus Pneumonia (8882 isolates), Haemophilus Influenzae
(8523), Moraxella Catharralis (874)
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Streptococcus Pn. : 95% Amoxicilline S Quinolone resistance
1,1% Haemophilus : Beta Lactamase production 16,9%
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ARI in children, Pakistan 87 strains of Streptococcus
pneumoniae from blood culture 97% resistant to at least one drug
31% R to Cotrimoxazole, 39% R to Chloramphenicol All isolates were
susceptible to erythromycin, cefaclor, cephalothin, ceftriaxone,
cefuroxime, rifampicin, vancomycin, and clindamycin Mastro TD,
Lancet 1991 Jan 19 ; 337(8734):156-9.
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Critical microbes Legionella Pneumophila Influenza A +B Avian
Influenza SARS CA-MRSA Epidemiological challenges or treatment
different from standart regimen
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Which diagnostic methods ?
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Blood cultures (pros) Pretreatment blood cultures positive for
a pathogen in 7 to 16 percent of hospitalized patients.
Streptococcus pneumoniae : 2/3 of the positive blood cultures When
positive, the microbial diagnosis is established. Only diagnostic
test done, in most cases : major source of microbiologic data
(resistance patterns of S. pneumoniae )
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Blood cultures (cons) The blood culture positivity rate is
relatively low. High rate of false positive blood cultures (up to
10 percent). Eg Staphylococcus. Positive cultures rarely lead to
modification or narrowing of antibiotic therapy
Slide 26 25 PMNs / LPF but < 10 SECs/LPF on Gram Stain
Interpretation : Quantitation of growth (heavy, moderate or light,
quantitative threshold 10 7 CFU), clinical correlation, correlation
with the Gram's stain">
Sputum : standard quality criterias Deep cough specimen
obtained prior to antibiotics, To be sampled only if
macroscopically purulent sputum, Cultures performed rapidly after
collection, preferably within two hours Good" sputum sample : >
25 PMNs / LPF but < 10 SECs/LPF on Gram Stain Interpretation :
Quantitation of growth (heavy, moderate or light, quantitative
threshold 10 7 CFU), clinical correlation, correlation with the
Gram's stain
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Invasive sampling Protected brush specimen Bronchalveolar
Lavage In case of failure of the initial treatment If epidemiology
or clinical presentation suggest a specific pathogens that is not
covered by usual treatment strategy If patient is intubated
(ICU)
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Pleural Tap Rarely positive Evidences empyema
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Urinary antigens (pros) Urine specimens avalable when patients
cannot supply expectorated sputum. Results of urine antigen testing
immediately available. Retains validity even after the initiation
of antibiotic therapy. High sensitivity compared to blood cultures
and sputum studies.
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Urinary antigens (cons) The sensitivity and specificity may be
less in patients without bacteremia. No microbial pathogen
available for antibiotic sensitivity testing.
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Urinary Antigen LP Legionella Pneumophila Only for serotype 1
(the most frequent 80%) Sensitivity 86%, specificity 93% Positive 1
to 3 days after the onset of disease
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Urinary antigen (SP) Sensitivity 77-89% if CAP with blood
culture +, Sensitivity 44-64% if blood culture False positive test
rare Rapid diagnosis, still positive after 7 days of antibiotics,
persists several weeks.
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Diagnostic yield of microbiological tests Prospective study :
262 hospitalized patients with CAP. Sputum for Gram staining,
culture, and detection of pneumococcal antigen; blood for culture
and serologic tests; urine for legionella and pneumococcal
antigens; and specimens obtained by bronchoscopy. A pathogen was
identified in 158 (60 percent) patients Adequate sputum samples
obtained in only 44 patients : Gram's stain + positive sputum
culture in 36/44 patients (82%). Van der Eerden MM, Eur J Clin
Microbiol Infect Dis 2005 Apr;24(4):241-9.
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Diagnostic yield of microbiological tests S. pneumoniae most
commonly identified (97 of 158). Urinary pneumococcal antigen test
positive in 52/97 (54%) patients with pneumococcal pneumonia. Blood
cultures were positive in 40 of 254 (16%) patients. Bronchoscopy :
additive diagnostic value in 18/37 patients (49%) who did not
expectorate sputum and in 14 of 27 patients (52 percent) who failed
treatment within 72 hours after admission. Van der Eerden MM, Eur J
Clin Microbiol Infect Dis 2005 Apr;24(4):241-9.
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PCR Multiplex Real-time PCR Respiratory viruses and atypical
bacteria (eg, M. pneumoniae, L. pneumophila, Legionella spp, C.
pneumoniae, influenza A and B virus, respiratory syncytial virus,
parainfluenza viruses, human rhinovirus, metapneumovirus,
adenovirus, and human coronaviruses) 105 adults : etiology
determined 50% with conventional techniques 80% with PCR But
increased cost. ? Less antibiotic use. Templeton KE, Clin Infect
Dis 2005 Aug 1;41(3):345-51.
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Minimal approach 2 blood cultures and Tracheal Aspirate culture
if patient is intubated before antibiotics are given Urinary
Legionella Pn. Antigen
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Where should the patient be managed ? At home In the ward In
the ICU saving lifes and saving money Identify low risk patient to
save money (and hospital beds !) Identify high risk patient to save
life
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Saving lifes : the high risk patient
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Saving money, avoid unnecessary hospitalisation Large cohorts
for validation (38,039 adults retrospectively, 2,287 adults for
prospective validation)
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Fine scoring system ClassPoints II 70 III71 - 90 IV91 - 130
V> 130 Fine et al. N Engl J Med 1997; 336: 243-50
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Fine et coll. NEJM 1997
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Decision IV, V : admit the patient I : no admission II, III :
no admission if score results from the age + 1 other criteria.
Admit systematically if : Hypoxemia SaO2