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Respiratory Tract Infections Bacterial. Dr. Ross Davidson Rm 309, MacKenzie Building QE II HSC ph: 473-5520 [email protected] Respiratory Tract Infections. Pneumonia - community-acquired - hospital AECB (AE-COPD) Sinusitis Otitis media. RTIs.

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Respiratory Tract InfectionsBacterial

Dr. Ross Davidson

Rm 309, MacKenzie Building

QE II HSC

ph: 473-5520

[email protected]


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Respiratory Tract Infections

  • Pneumonia - community-acquired - hospital

  • AECB (AE-COPD)

  • Sinusitis

  • Otitis media


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RTIs

  • 1st lecture – Common bacterial causes

  • 2nd lecture – Mycobacteria & atypical pathogens


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RTI - specimens

  • Sputum

  • BAL / bronch washing

  • Naso-pharyngeal aspirates

  • Endotracheal aspirates

  • Sinus aspirates

  • Tympanocentesis


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Respiratory Tract InfectionsCommon Pathogens

  • Streptococcus pneumoniae

  • Haemophilus influenzae

  • Moraxella catarrhalis

  • Mycoplasma pneumoniae

  • Chlamydophyla pneumoniae

  • Legionella pneumophila

  • S.aureus

  • B.pertussis

  • Gram-negatives / anaerobes

Atypical Pathogens


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Community Acquired Pneumoniaetiology

S.pneumoniae

H.influenzae

Other

Anaerobes

L.pneumophilia

M.pneumoniae

C.pneumoniae


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Respiratory Tract Infections

  • S.pneumoniae

  • Most common bacterial cause of RTIssmall gram positive diplococcialpha haemolytic, bile soluble, optochin Sgrowth often enhanced in CO2 atmospheremost are encapsulated (> 80 distinct types)

  • Colonizes the nasopharynx in 5-10% of adults and 20-40% of children

  • Incidence increases in winter months


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Respiratory Tract Infections

  • Pathogenicity-adherence essential for colonization-capsule is important virulence factor - aids in escape from phagocytic cells

  • Predisposition to pneumococcal infection-defective Ab formation-insufficient numbers of PMNs-day-cares, military, prisons, shelters-chronic respiratory disease-infancy and aging-diabetes, alcoholism, liver disease



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Respiratory Tract Infections

  • Pneumococcal vaccine23 different serotypesaccount for 90% of invasive strainsprotection wanes with time and age

  • Indications for vaccineadvanced age myelomasplenectomy alcoholismHIV / AIDs diabeteslymphoma

  • PREVNAR- conjugate vaccine - indicated for use in infants < 2 years of age


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S.pneumoniae

  • Treatment- penicillins, cephalosporins, macrolides, fluoroquinolones

  • Choice of antibiotic - site of infection - co-morbidities - degree of illness - ambulatory / inpatient


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Respiratory Tract Infections

  • Antibiotic resistance in S.pneumoniae- penicillin resistance is major concern - due to remodeling of the PBP- multi-drug resistance


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oral / viridans

Streptococci

0.03 g/ml

S.pneumoniae

0.06 g/ml

0.12 g/ml

0.5 g/ml

Penicillin Resistance inS.pneumoniae

Minimum

Inhibitory Concentration


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Percentage of Penicillin Non-Susceptible S. pneumoniae in Canada: 1988-2005

16

% Intermediate Resistance

14

% High-level Resistance

12

10

8

6

4

2

0

1988

1993

1995

1997

1999

2001

2003

2005

Low, D: Canadian Bacterial Surveillance Network, Nov , 2005


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% Resistance

25

High Res

Intermediate Res

20

15

10

5

0

Pen-I

Cefprozil

TMP/SMX

Amoxicillin

Ceftriaxone

Cefuroxime

Gatifloxacin

Tetracycline

Moxifloxacin

Levofloxacin

Gemifloxacin

Erythromycin

Telithromycin

Resistance in S.pneumoniae


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Relationship Between Patient Types, Pulmonary Function, and Likely Pathogens

Viral, allergens, pollutants, cigarette smoke

M.pneumoniae, C.pneumoniae

H.influenzae, S.pneumoniae

FEV1 % Predicted

Enterobacteriaceae Pseudomonas spp Gram-negatives

Resistant organisms

Acute Bronchitis

Chronic Bronchitis

Simple

Complicated

Complicated

PLUS Risks


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Respiratory Tract Infections Likely Pathogens

  • H.influenzae

  • Most common cause of AE-COPD-small gram negative bacilli-requires X and V factors for growth-will grow on “chocolate” agar (5% CO2)-may be encapsulated

  • Historically, type b (Hib) responsible for majority of invasive disease

  • Introduction of Hib vaccine >> very little Hib seen today

  • majority of mucosal disease due to non-encapsulated strains


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Respiratory Tract Infections Likely Pathogens

  • Approx 20% produce -lactamase

  • < 2% have altered PBP

  • 2nd / 3rd generation cephalosporins effective

  • newer macrolides have some activity

  • fluoroquinolones very active, but contraindicated in children


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Respiratory Tract Infections Likely Pathogens

  • Moraxella catarrhalissmall gram negative cocco-bacilliassociated with otitis media, sinusitis, AECBcarriage rate probably approaches 50%

  • 90% strains resistant to ampicillinwith exception of trimethoprim, predictably susceptible to most oral antibiotics


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Respiratory Tract Infections Likely Pathogens

  • Bordetella pertussis

  • Causitive agent of pertussis

  • Small gram negative cocci-bacilli

  • Strictly aerobic, fastidious

  • Requires growth on media containing charcoal, blood, or starch

  • Bordet-Gengou(BG) or RL medium


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Respiratory Tract Infections Likely Pathogens

  • Incubation period generally 7-10 days (range 4-21)

  • Classical course of disease:1. Catarrhal stage 1-2 weeks - symptoms non specific - low grade fever, mild cough, etc 2. Paroxysmal stage 1-6 weeks - paroxysmal cough, whoop, posttussive vomiting 3. convalescent stage 2-4 weeks - symptoms gradually decrease


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Respiratory Tract Infections Likely Pathogens

  • Laboratory diagnosis

  • Naso-pharyngeal specimens best yield

  • - culture - PCR - DFA

  • Treatment - macrolides 1st choice


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RTIs Likely Pathogens

  • Nosocomial pneumonia - ventilated patients at increased risk - gram negative bacteria / S.aureus

  • Nursing home pneumonia - similar etiology to CAP - greater incidence of anaerobes


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