Respiratory Infections

Viral Infection

a. Pharyngitis & Rhinitis (caused by rhinovirus, coxsackie, coronaviruses, adenoviruses, RSV & othomyxoviruses) > rhinitis, nasal obstruction, nasal discharge & general malaise

b. Influenza; airborne transmission, type A, B or C

c. Laryngotracheobronchitis (Croup); parainfluenza viruses > acute infection

d. Bronchiolitis; parainfluenza virus > acute infection > possibly fatal in babies

Upper Respiratory Tract Infections

Bacterial Infections

a. Streptococcal pharyngitis; Strep. Pyogenes > inflammed mucous membrane > fever, headache & lymph node enlargement > Quinsy (complicated infection leading to peritonsillar abscess (may also result in acute GN or rheumatic fever)

b. Epiglottitis (=Haemophilus Influenzae); Influenza B Virus > systemic infection, cellulitis, epiglotic enlargment & obstruction > possible meningitis (HIB vaccine protects against bacterium)

c. Diphtheria; C. diphtheriae > release of exotoxin > formation of "false membrane" & local oedema > airway occlusion

d. Pertussis (Whooping cough); B. pertussis > upper/lower tract infection > catarrhal stage (resembles minor infection) > paroxysmal stage (paroxysms of coughing) > convalescent stage (similar symptoms to chronic bronchitis) (DTP vaccine available)

Sinus & Middle Ear Infections

a. Sinusitis; due to impaired drainage > viral infection/allergic reaction/anatomical defects/indwelling nasal tubes > bacterial sinusitis (commonly pyogenic bacteria)

b. Otitis Media; impaired drainage of eustachian tube due to virus infection/allergies/throat infections

c. Otitis Externae; due to Strep. Pyogenes or Staph. Aureus > diffuse infections > Pseudomonas aeruginosa "swimmer's ear", Aspergillus

Bronchitis

Acute Pneumonia

Community Acquired Pneumonia

Atypical Pneumonia

Legionnaire's Disease

Pulmonary Tuberculosis

Aetiological factors

Commonly viral but bacterial microbes such as Bordetella petussis (Whooping cough) & Mycoplasma pneumonia (Atypical pneumonia) = chronic bronchitis

Chronic Bronchitis

Productive cough & airflow obstruction (COPD) > increase exacerbation (frequency & amount of exudate) = chronic bronchitis attack (acute exacerbation)

Chronic bronchitis & CF

Reduced ability to remove secretions from respiratory tract > increased susceptibility to bacterial infection

Common pathogens include Pseudomonas aeruginosa (characterised by 1. Moisture 2. Resistance (to drugs) 3. Slime production

Aspiration Pneumonia

Inhalation of vomit/saliva (in unconscious individual) > mixture of microorganisms within GIT (inc. anaerobes from oral cavity)

Outline

Presents with copious sputum production in very young/elderly, major complication of a primary viral infection & secondary bacterial pneumonia

Main microbes involved are S. Pneumoniae (contains anti-phagocytic capsule & produced pneumolysin > potent inflammation > polymorph attraction > lobar consolidation > reduced oxygen perfusion)

- May cause lung destruction > septicaemia

Usually results in TYPICAL pattern changes seen w/ X-ray (Lobar pneumonia & bronchopneumonia)

Treatment usually consists of cepaholsporin (broad-spectrum antibiotic)

Outline

Diffuse pattern of invasion/growth (bilateral infiltration rather than consolidation)

Lymphocyte mediated; Cytotoxic T-cells > inflammatory response

Involved microbes include Mycoplasma pneumoniae (cause of 'Ambulent Pneumonia', abnormal cell wall = penicillin ineffective), Viral pneumonia (VZV & measles virus), Coxiella burnetii (cause of 'Q fever') & chlamydia/chlamydia-like (I.e psittacosis from birds)

Outline

Presents as either atypical pneumonia or bronchopneumonia (inhaling infected aerosoles from cooling towers)

Legionella species can be found within amoeba & macrophages

Outline

Main aetiology is from the Mycobacterium tuberculosis species

Tubercle formation following persistent macrophagic attempts to phagocytose microbes > lymphocytes wall off microbe > calcified lesion

Normally asymptomatic but may present with symptoms of blood stained sputum, night sweats, weight loss & anorexia, upper mass formation

Treated with DOTS (direct observational treatment strategy), BCG vaccine protects those of highest risk (I.e health care workers)

More common in lungs and then kidneys, no antibodies activated & diagnosed with MANTOUX test