M8: TB and Respiratory pathogens Flashcards
What is tuberculosis?
A granulomatous infectious disease caused by Mycobacterium tuberculosis
What are the symptoms of tuberculosis?
Persistant cough (blood in sputum) Fatigue Chest pain Loss of appatite Weight loss Fevers and night sweats Chills
what is a granuloma?
a chronic inflammatory reaction, predominantly
of activated macrophages – aggregation of macrophages
with lymphocytes and some plasma cells.
- cheese like
what are the oral manifestations of TB?
Ulcer on tongue (also less often on any oral mucosal site).
Nodules, periapical granulomas, indurated (hardened) patches.
Oral lesions can be overlooked in the absence of systemic symptoms
Give the characteristics of mycobacteria
Aerobic,
curved/straight rods, non-motile
Acid-fast - Cell wall contains ‘waxy’ lipids (mycolic acids)
Causes TB in humans
What colour do Acid fast calls stain on a green background?
red (rods/bacilli)
other bacteria that are non-acid fast stain green
Give the characteristics of the growth of TB
slow growing
colonies (visible to the eye after 8 weeks) are typically ‘rough, buff (ie pale yellowish) and tough’
temp. range of growth: 35-37 ºC
What is a biomarker
a substance/structure/process that can be measured in the body or its products and influence/predict the incidence of outcome or disease
what are the 4 closely related speciec that can cause mammalian TB
- M.tuberculosis (Human)
- M.bovis (bovine – also human and other mammals)
- M.africanum (human, mainly found in equatorial Africa)
- M.microti (vole – seldom encountered)
what are the 2 main forms of TB
primary & post-primary
explain the stages of primary infection
- Initial infection (lungs)
- M. tuberculosis replicates via macrophages
- Macrophage carries disease to hilar lymph node = additional foci; ghon focus; spread to other organs & tissues
- 10 days+ T-lymphocytes produce; lymphokines; macrophages
- GRANULOMA (cheese-like cessation)
- Limits primary infection, but mycobacteria persists within = POST PRIMARY DISEASE
explain the stages of post-primary TB
- Reactivation of dormant foci in lobes of lungs
- Large granulomas with caseation
- Tuberculoma expands onto bronchus = bacilli in sputum & further spread & lesion
what patients are mire suscptible to post-primary TB
HIV px; elderly; transplant px
post-primary TB is cause be the reactivation of _______
dormant foci in the lobes of the lungs
Tuberculoma expands into the bronchus in post-primary TB. T/F?
T
how is TB transmitted
Droplet inhalation from ‘open’ (sputum +ve) individuals
What is the vaccination for TB and what is its efficacy?
BCG (bacille calmette-guerin)
Intracutaneous injection
Variable efficacy – better in children, variable in adults
What drugs are given to the px in the intensive 2 month phase, and in the continuous 6-9 month phase to treat TB?
intensive phase: Rifampicin, Isoniazid Pyrazinamide (and/or Ethambutol)
continuation phase:
Rifampicin
Isoniazid
What are the stages of Pneumonia?
Inflammation of bronchial and alveolar spaces -> Anoxia -> Altered cardiopulmonary
functions -> Morbidity/Mortality
Name the bacteria found in:
- Acute and chronic bronchitis
- bronchiectasis
- whooping cough
1. Bronchitis Acute: -Mycoplasma pneumoniae Chronic: -H.influenzae -S.pneumoniae 2. Bronchiectasis (weakened and dilated bronchus) H.influenza Ps.aeruginosa (anaerobes) 3. Whooping Cough B.pertussis
what type of pathogens can cause primary pneumonia?
Streptococcus pneumoniae Yersinia Pestis (Pneumonic plague) Klebsiella pneumoniae Bacillus anthracis (anthrax) Legionella pneumophilia (Legionnairesdisease) (Mycoplasma, Chlamydia)
what type of pathogens can cause secondary pneumonia?
Strep. pneumoniae
Haemophilus influenzae
Branhamella catarrhalis
fungal infections
what are haemophilus species?
-gram -ve rod; pleomorphus = coccobacillus/filamentous shape
-facultative anaerobes
• CO2 enhances growth
• Catalase +ve
• Oxidase +ve
-requires X factor (haemin) and/or V factor NADP
how many antigenic types of haemphilus influenza are ther and which is the most important?
6,
B
• Capsular type b strains are most frequently
associated with invasive disease
Haemophilus influenzae
Carriage
• Upper resp. tract (nasopharynx/throat)
• Non capsulate stains in 25 – 80% healthy individuals
• Capsulate strains in 5 – 10% healthy individuals
• Type b strains in 1 – 5% healthy individuals
Pathogenesis
• Important in young children ( 2 months to 2 years especially)
• Possibly penetration of submucosa of nasopharynx by H.influenzae
• Occasionally causes pulmonary disease in adults
with preceding viral infection or chronic bronchitis
Otitis Media
• Frequently caused by non-typable strains although
pathogenesis is unclear
Virulence factors
• Capsule – antiphagocytic
• Pili (fimbrae) – attachment to epithelial cells
• IgA protease
• Other cell membrane components
Non-invasive disease
• Usually non-encapsulated strains
• Often predisposition (viral, anatomical)
• Local infection
Otitis media
Sinusitis
• Can give chronic obstructive airway
disease
what are the characteritics of corynebacterium diphtheriae?
• Causes diphtheria
• Gram +ve rods – diptheroids or
coryneforms (pleomorphic rods which may stain irregularly ‘Chinese Lettering!’)
Aerobic/facultative anaerobic
how is corynebacterium diphtheriae spread?
Person to person spread via nasopharyngeal
secretions;
children are particularly susceptible
how can corynebacterium diphtheriae cause respiratory obstruction?
C.diptheriae elicit an inflammatory exudate
and cause necrosis of faucial mucosa (Fauces: opening leading from mouth to pharynx)
Infection may spread to post-nasal cavity of
larynx and cause respiratory obstruction.
+
Clotting of exudate which becomes adherent –
pseudomembrane
what is the treatment for diphtheria
px. in isolation; antibiotics given: Pencillin, Tetracycline, Clindamycin
what tests allow you to differentiate between different toxigenic strains
from commensal corynebacteria
- Elek Test
* Schick Test
