Respiratory Tract Infections Bacterial

Respiratory Tract Infections Bacterial Dr. Ross Davidson Rm 309, MacKenzie Building QE II HSC ph: 473-5520 Respiratory Tract Infections • Pneumonia - community-acquired - hospital • AECB (AE-COPD) • Sinusitis • Otitis media RTIs • 1st lecture – Common bacterial causes • 2nd lecture – Mycobacteria & atypical pathogens RTI - specimens • • • • • • Sputum BAL / bronch washing Naso-pharyngeal aspirates Endotracheal aspirates Sinus aspirates Tympanocentesis Respiratory Tract Infections Common Pathogens • • • • • • Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis Mycoplasma pneumoniae Chlamydaphyla pneumoniae Legionella pneumophila Atypical Pathogens • S.aureus • B.pertussis • Gram-negatives / anaerobes Community Acquired Pneumonia etiology S.pneumoniae H.influenzae Other Anaerobes L.pneumophilia M.pneumoniae C.pneumoniae Respiratory Tract Infections • S.pneumoniae • Most common bacterial cause of RTIs small gram positive diplococci alpha haemolytic, bile soluble, optochin S growth often enhanced in CO2 atmosphere most are encapsulated (> 80 distinct types) • Colonizes the nasopharynx in 5-10% of adults and 20-40% of children • Incidence increases in winter months 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 Pneumococcal Capsule Respiratory Tract Infections • Pneumococcal vaccine 23 different serotypes account for 90% of invasive strains protection wanes with time and age Indications for vaccine advanced age splenectomy HIV / AIDs lymphoma • myeloma alcoholism diabetes • PREVNAR - conjugate vaccine - indicated for use in infants < 2 years of age S.pneumoniae • Treatment - penicillins, cephalosporins, macrolides, fluoroquinolones • Choice of antibiotic - site of infection - co-morbidities - degree of illness - ambulatory / inpatient Respiratory Tract Infections • Antibiotic resistance in S.pneumoniae - penicillin resistance is major concern - due to remodeling of the PBP - multi-drug resistance Penicillin Resistance in S.pneumoniae Minimum Inhibitory Concentration oral / viridans Streptococci S.pneumoniae 0.03 g/ml 0.06 g/ml 0.12 g/ml 0.5 g/ml Penicillin-Resistant Pneumococci: Canadian Bacterial Surveillance Network, 1988-2003 16 14 12 % Intermediate Resistance % High-level Resistance 10 8 6 4 2 0 1988 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Canadian Bacterial Surveillance Network, Apr 15. 2004 Resistance in S.pneumoniae % Resistance 25 20 15 10 5 0 Relationship Between Patient Types, Pulmonary Function, and Likely Pathogens Viral, allergens, pollutants, cigarette smoke M.pneumoniae, C.pneumoniae H.influenzae, S.pneumoniae Enterobacteriaceae Pseudomonas spp Gram-negatives Resistant organisms Acute Bronchitis Simple FEV1 % Predicted Chronic Bronchitis Complicated Complicated PLUS Risks 16 4/22/2008 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 >> very little Hib seen today • majority of mucosal disease due to non-encapsulated strains Respiratory Tract Infections • • • • • 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 Respiratory Tract Infections • Moraxella catarrhalis small gram negative cocco-bacilli associated with otitis media, sinusitis, AECB carriage rate probably approaches 50% • 90% strains resistant to ampicillin with exception of trimethoprim, predictably susceptible to most oral antibiotics 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 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 Respiratory Tract Infections • Laboratory diagnosis • Naso-pharyngeal specimens best yield • - culture - PCR - DFA • Treatment - macrolides 1st choice RTIs • Nosocomial pneumonia - ventilated patients at increased risk - gram negative bacteria / S.aureus • Nursing home pneumonia - similar etiology to CAP - greater incidence of anaerobes