Common pathogens in pneumonia Bacteria

1
Common pathogens in pneumoniaBacteria

• Streptococcus pneumoniae
• Haemophilus influenzae
• Bordetella pertussis
• Chlamydia pneumoniae
• Legionella pneumophila
• Mycoplasma pneumoniae

2
Common pathogens in pneumoniaVirus

• Influensa A
• Respiratory syncytial virus
• Parainfluensa virus
• Metapneumovirus
• Adenovirus

3
Streptococcus pneumoniaeEpidemiology

• Present in nasopharynx of asymtomatic individuals
• High incidence of colonization in infants under 2
  years of age
• Low incidence in young people
• High incidence in people in their 70s

4
Streptococcus pneumoniaePathogenesis

• Nasopharyngeal colonization
• Viral respiratory infection, Influenza A,
  predisposes to pneumonia
• Splenectomy renders individuals vulnerable to
  catastrophic pneumococcal penumonia and
  bacteraemia
• Infection only in individuals without specific
  antibody to their colonizing serotype

5
Streptococcus pneumoniaeClinical features

• Pneumonia develops over several days
• Cough, sputum , dyspnoea, chest pain and myalgia
• In healthy young adults Hyperacute presentation
  with a dramatic rigor
• Older people, an insidious presentation, with
  only confusion and hypothermia
• Examination Consolidation, x-ray reveals
  infiltration

6
Streptococcus pneumoniaeLaboratory findings

• Most have a leukocytosis
• Leucopenia is an indicator of poor prognosis
• Examine morning sputum for quality, lt 10
  epithelial cells, gt20 white cells per microscopic
  field (not saliva)
• Sputum Gram stain and culture
• Blood culture for bacteraemia

7
Streptococcus pneumoniaeComplications

• Empyema, bacteria in the pleural space
• Persistence of fever and leucocytosis after 4-5
  days of appropriate antibiotic therapy
• Large amounts of pleural fluid on x-ray
• Empyema should be drained

8
Streptococcus pneumoniaeAntimicrobial therapy

• World wide Str. Pn. has become more resistant to
  penicillin, in Norway still sensitive
• Highly resistant isolates are common in some
  areas e.g. Spain, these strains are often
  resistant to other antibiotics
• If reduced sensitivity Str. Pn. often responds to
  penicillin or cephalosporins in high dose

9
Streptococcus pneumoniaePrevention

• A polyvalent pneumococcal vaccine (not
  omnivalent)
• Vaccination produces antibody response in 85
• Vaccination is effective in splenectomized but
  not in children lt2 years of age
• Vaccination is recommended after splenectomy, in
  chronic disease and in people gt65 years of age

10
Haemophilus influenzae

• Pneumonia in chronic bronchitis, smokers and
  alcoholics
• Mucosal infection such as middle ear and
  bronchitis
• Capsulate HI in pneumonia, microbial diagnosis is
  difficult, blood culture should always be done

11
Bordetella pertussis

• Transmitted by droplets, highly infectious
• Epidemics in cycles of 3-5 years
• Vaccination provides immunity for about 12 years
• BP has several virulence factors with damage to
  airway epithelium and activity against local
  neurons, which explains cough
• BP survives in phagocytes
• Diagnosis PCR

12
Chlamydia pneumoniaeTWAR

• Common cause of mild pneumonia in young adults
• Serious respiratory disease in young children and
  old debilitated individuals
• Clinical feature Bronchitis with persistent
  cough
• Serodiagnosis It may take months for
  seroconversion
• Treatment Tetracyclin or erythromycin

13
Legionella pneumophila

• Pathogenesis Inhalation of contaminated
  aerosols, LP is phagocytosed by macrophages but
  they fail to kill LP
• Epidemiology LP survives in water and is
  associated with water facilities of large
  buildings
• Clinical Pneumonia, Legionnaires disease with
  severe pneumonia and extrapulmonary manifestations

14
Mycoplasma pneumoniae

• Cold agglutinins is a useful bedside test, pos in
  50 of the patients
• Diagnosis is serological, a 4-fold increase in CF
  titre is diagnostic, ELISA for IgM can be used
• Therapy, erythromycin and tetracycline. Newer
  macrolides such as azithromycin are better
  tolerated than erythomycin

15
Mycoplasma pneumoniae

• Epidemiology Spreads with ease in institutions,
  highest incidence during the first two decades of
  life
• Pathogenesis Spreads by droplets, repeated
  infections results in pneumonitis
• Clinical Gradual onset, an initially dry cough
  dominates the disease, CNS symptoms are common in
  hospital treated patients

16
Respiratory viruses

• RSV, Metapneumovirusand and Coronavirus, severe
  lower respiratory illness in young children
• Parainfluenza types 1 and 2 agents of
  laryngotracheitis (croup)
• Rhinovirus and Coronavirus produce common cold
  like symptoms
• Adenovirus, pneumonia in children and military
  recruits
• SARS, severe pneumonia with high mortality

17
Influenza A

• Unique in their ability to cause recurrent
  epidemics and global pandemics
• Unpredictable antigenic change
• Clinical Influenza-like, mild respiratory
  disease fatal viral pneumonia
• Symptoms in elderly may be atypical
• Complications Secondary bacterial infection 5-10
  days after onset of IA

18
Influenza A

• Serious complications in old, very young and
  those with underlying disease
• 3 true pandemics, Spanish flu 1918, Asian flu
  1957 and Hong Kong flu in 1968
• Control Vaccine and chemoprofylaxis or therapy
  with rimantidine or neuraminidase inhibitors