Respiratory Tract Infections Bacterial

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Respiratory Tract InfectionsBacterial

• Dr. Ross Davidson
• Rm 309, MacKenzie Building
• QE II HSC
• ph 473-5520
• ross.davidson_at_cdha.nshealth.ca

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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 (gt 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-defectiv
  e 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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Pneumococcal Capsule
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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 lt 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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Penicillin Resistance inS.pneumoniae
Minimum Inhibitory Concentration
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Percentage of Penicillin Non-Susceptible S.
pneumoniae in Canada 1988-2005
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Intermediate Resistance
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High-level Resistance
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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 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

• 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 gtgt very little Hib
  seen today
• majority of mucosal disease due to
  non-encapsulated strains

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Respiratory Tract Infections

• Approx 20 produce ?-lactamase
• lt 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

• 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

• 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

• 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

• Laboratory diagnosis
• Naso-pharyngeal specimens best yield
• - culture - PCR - DFA
• Treatment - macrolides 1st choice

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RTIs

• Nosocomial pneumonia - ventilated patients at
  increased risk - gram negative bacteria /
  S.aureus
• Nursing home pneumonia - similar etiology to
  CAP - greater incidence of anaerobes