Microbiology of Respiratory Infection II

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Microbiology of Respiratory Infection II

• Dr Michael Lockhart

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Respiratory Infections

• Infections of throat and pharynx
• Infections of middle ear and sinuses
• Infections of trachea and bronchi
• Infections of the lungs

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Infections of throat and pharynx

• Sore throat
• Diphtheria
• Candida/thrush
• Vincents angina

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Infections of throat and pharynx

• Diagnosis
• Well taken throat swab

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SORE THROAT
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Sore throat

• VAST MAJORITY (OVER TWO THIRDS) - VIRAL
• DO NOT NEED ANTIBIOTICS

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Bacterial sore throat

• The most common BACTERIAL cause is Streptococcus
  pyogenes (also known as Group A streptococci)
• Clinical Acute follicular tonsillitis
• TreatmentPenicillin

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Streptococcus pyogenes
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Streptococcal sore throat

• Acute complications
• Peritonsillar abscess (quinsy)
• Sinusitis/ otitis media
• Scarlet fever

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QUINSY (PERITONSILLAR ABSCESS)
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Streptococcal sore throat

• Late complications
• Rheumatic fever
• 3 weeks post sore throat
• fever, arthritis and pancarditis
• Glomerulonephritis
• 1-3 weeks post sore throat
• haematuria, albuminuria and oedema

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Diphtheria

• Corynebacterium diphtheriae
• Clinical Severe sore throat with a grey white
  membrane across the pharynx. The organism
  produces a potent exotoxin which is cardiotoxic
  and neurotoxic.

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DIPHTHERIA
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DIPHTHERIA
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Diphtheria

• Epidemiology Rare, but increased in certain
  parts of the world eg Russia
• Treatment Antitoxin and Supportive and
  Penicillin/erythromycin

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Candida/Thrush

• Candida albicans
• Clinical White patches on red, raw mucous
  membranes in throat/ mouth
• Cause endogenous
• Treatment Nystatin

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ORAL THRUSH
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Vincents angina

• Mixture of organisms (Borrelia vincenti and
  Fusobacterium sp.)
• ClinicalFoul smelling mouth and throat ulcers
• Treatment penicillin

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VINCENTS ANGINA
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Respiratory Infections

• Infections of throat and pharynx
• Infections of middle ear and sinuses
• Infections of trachea and bronchi
• Infections of the lungs

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EAR
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OTITIS MEDIA
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Infections of middle ear and sinuses

• Often viral with bacterial secondary infection
• Most common bacteria Haemophilus influenzae,
  Streptococcus pneumoniae and Streptococcus
  pyogenes.
• Treat Amoxycillin

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Respiratory Infections

• Infections of throat and pharynx
• Infections of middle ear and sinuses
• Infections of trachea and bronchi
• Infections of the lungs

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Infections of trachea and bronchi

• Acute epiglottitis
• Acute exacerbations of COPD
• Cystic fibrosis
• Pertussis (whooping cough)

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Acute epiglottitis

• Haemophilus influenzae
• Clinical severe croup in children aged 2-7
  years, may progress to respiratory obstruction
  and death.

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EPIGLOTTITIS
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EPIGLOTTITIS
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Acute epiglottitis

• Microbiology of Haemophilus influenzae
• Habitat - upper respiratory tract
• Microscopy- small gram negative bacillus
• Culture - Chocolate agar -small translucent
  colonies
• Identify - X and V test H influenzae requires
  both factors X and V to grow.

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Haemophilus influenzae
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Acute epiglottitis

• Diagnosis blood culture (?throat swab)
• Treatment ITU and ceftriaxone

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COPD

• Acute exacerbations of COPD.
• Exacerbations of this chronic condition are often
  associated with bacterial infection.

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Acute exacerbations of COPD

• Often follow viral infection, or fall in
  atmospheric temperature with increase in humidity
  (often in winter)
• Clinical Patients present with increased
  breathlessness. The volume and purulence of
  sputum is increased.

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Acute exacerbations of COPD

• The most common organisms associated are
• Haemophilus influenzae
• Streptococcus pneumoniae
• Moraxella catarrhalis
• NB All three organisms are present in normal
  upper respiratory tract flora.

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Acute exacerbations of COPD

• Treatment
• Give antibiotics if ?sputum purulence. If no
  ?sputum purulence then antibiotics not needed
  unless consolidation on CXR or signs of
  pneumonia.
• 1ST LINE Amoxicillin 500mg tds 2ND LINE
  Doxycycline 200mg on day 1 then 100mg daily (5
  days)
• With time becomes increasingly difficult to
  treat, due to acquisition of more resistant
  organisms.

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Cystic fibrosis

• Inherited defect
• leads to abnormally viscid mucus which blocks
  tubular structures in many different organs
  including the lungs.

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Cystic fibrosis

• Chronic respiratory infection is a major problem.
• Causal bacteria
• Staphylococcus aureus and Haemophilus influenzae
• Pseudomonas aeruginosa
• Burkholderia cepacia

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Pertussis (whooping cough)

• Bordetella pertussis
• Clinical Acute tracheobronchitis
• cold like symptoms for two weeks
• paroxysmal coughing (2 weeks)
• repeated violent exhalations with severe
  inspiratory whoop, vomiting common
• residual cough for month or more

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Pertussis (whooping cough)

• Diagnosis
• pernasal swab (charcoal blood agar/ Bordet-Gengou
  medium)
• serology
• clinical ( by the stage of paroxysmal coughing
  organism numbers much reduced)
• Treatment most effective in the first 10 days of
  illness, also reduces spread to susceptible
  contacts
• Vaccination

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Pernasal swab
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Respiratory Infections

• Infections of throat and pharynx
• Infections of middle ear and sinuses
• Infections of trachea and bronchi
• Infections of the lungs

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Infections of the lungs

• Community acquired pneumonia
• Nosocomial pneumonia
• Legionnaires disease
• Pneumocysitis carinii pneumonia (PCP)
• Fungal chest infection
• Tuberculosis

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Community acquired pneumonia

• Clinical cough, sputum production, dyspnoea,
  fever.
• Chest x-ray with infiltrates.
• Acquired in the community

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Community acquired pneumonia

• Causative organisms
• Streptococcus pneumoniae 70
• Atypicals/viruses 20
• Staphylococcus aureus 4
• Other bacteria 1
• Haemophilus influenzae 5

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Community acquired pneumonia

• Streptococcus pneumoniae
• Microbiology
• Microscopy - gram positive cocci
• Culture - Alpha haemolytic colonies, typically
  draughtsmen ie with sunken centre.
• Identify - Optochin sensitive
• Treatment - generally penicillin sensitive

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Streptococcus pneumoniae
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Lobar pneumonia
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Community acquired pneumonia

• Atypicals - old term for pneumonias not
  attributable to any of the common bacterial
  causes of pneumonia.
• Refer to Dr McIntyres talk

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Community acquired pneumonia

• Treatment , follow the Tayside Critical Care
  Pathway for the Management of Community-Acquired
  Pneumonia

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CURB65 SCORE 3 OR MORE (SEVERE)

• ANTIBIOTICS SEVERE
• ALL SHOULD INITIALLY RECEIVE
• IV CO-AMOXICLAV 1.2g x3/day PLUS IV
  CLARITHROMYCIN 500mg x2/day or PO DOXYCYCLINE
  100mg x2/day
• (PENICILLIN ALLERGY
• IV Levofloxacin 500mg2/day)
• Step down to oral doxycycline 100mg x 2/day in
  all patients
• ALL SHOULD HAVE Paired serology, throat
  swab/gargle for virology PCR, urinary legionella
  antigen tests
• Treat for at least 10 days (IV/oral)

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Nosocomial pneumonia

• hospital acquired pneumonia
• Predisposing factors
• Intubation
• Intensive care unit
• Antibiotics
• Surgery
• Immunosuppression

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Nosocomial pneumonia

• Organisms -60 gram negative organisms
• includes Pseudomonas aeruginosa, and Coliforms
  (such as E.coli, Klebsiella sp)
• If aspiration pneumonia anaerobes may be involved
  
• Treatment
• Severe IV Amoxicillin Metronidazole
  Gentamicin
• Step down to Coamoxiclav PO 7-10 days total
• Non severe Amoxicillin Metronidazole for 7
  days

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Legionnaires disease

• Legionella pneumophila
• Clinical
• flu like illness which may progress to a severe
  pneumonia, with mental confusion, acute renal
  failure and GI symptoms.
• Epidemiology
• often associated with travel, usually associated
  with water.

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Legionnaires disease

• Diagnosis Legionella urinary antigen/
  Serology
• Treatment
• Erythromycin/clarythromycin
• Fluoroquinolones

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Pneumocysitis carinii pneumonia (PCP)

• A cause of pneumonia in patients with AIDS
• Diagnosis Bronchioalvelar lavage (BAL) or
  induced sputum and identification of cysts.
• Treatment Cotrimoxazole, pentamidine.

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Fungal chest infection

• Aspergillus fumigatus
• Clinical Causes severe pneumonia/systemic
  infection in the severely immunocompromised.
• Or aspergilloma
• Diagnosis Culture
• Treatment iv Amphotereicin B

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ASPERGILLOMA
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TUBERCULOSIS

• Mycobacterium tuberculosis
• Acid Alcohol Fast Bacilli
• Bread crumb like growth on special medium, after
  prolonged (up to 3 months) incubation

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Acid and Alcohol Fast Bacilli (AAFB)
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Growing Tuberculosis
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Tuberculosis

• For more detailed information see Dr Winters
  Lecture

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Infections in lungs

• General diagnostic points

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Infections of the lungs - Diagnosis

• Isolation of causal pathogen
• Sputum NB Quality of sputum sample important
• Blood culture (organism in blood of one third of
  patients with pneumonia)

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Infections of the lungs - Diagnosis

• Detection of bacterial antigen
• eg Legionella urinary antigen
• Direct immunofluorescence for PCP
• Serology
• eg Legionella serology

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Immunisation

• UK guidance is summarised in a document called
  The Green Book available online at
• http//www.dh.gov.uk/PolicyAndGuidance/HealthAndSo
  cialCareTopics/GreenBook/fs/en

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Pneumococcal immunisation

• Pneumococcal polysaccharide vaccine covers 23
  different capsule types
• Efficacy 50-70 reduction of bacteremia risk
• Pneumococcal conjugate vaccine covers 7 different
  capsular types common childhood strains
• Efficacy 97 protection

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Pneumococcal immunisation

• Indications
• All those aged 65 years and over
• Childhood immunisation schedule
• Risk groups
• No spleen
• Various chronic diseases including COPD
• Immunosuppressed
• Patients with CSF shunts

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Hib

• Invasive Haemophilus infection caused most
  commonly by Type b capsular strains (Hib).
• Conjugate vaccine offered to all children less
  than 1, and all asplenic individuals
• Highly effective

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Pertussis immunisation

• Acellular vaccine 5 purified pertussis
  components
• Given as part of the childhood immunisation
  schedule

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Immunisation for Tuberculosis

• Live attenuated strain of Mycobacterium bovis
• UK efficacy of 70 in protecting against TB
• Risk based approach to identify those who receive
  the vaccine

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Community acquired pneumonia

• Causative organisms
• Streptococcus pneumoniae 70
• Atypicals/viruses 20
• Staphylococcus aureus 4
• Other bacteria 1
• Haemophilus influenzae 5