Transcript Infectious Diseases

Infectious Diseases
Dr. Meg-angela Christi Amores
Infectious Diseases
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Tuberculosis
Leprosy
AIDS
Syphilis
Viral Infections
Pneumonia
Herpes
TUBERCULOSIS
• one of the oldest diseases to affect humans
• caused by bacteria of the Mycobacterium
tuberculosis complex
• Usually affects the lungs
• untreated, the disease may be fatal within 5
years in 50–65% of cases
• airborne spread of droplet nuclei
M. Tuberculosis
• rod-shaped, non-sporeforming, thin aerobic
bacterium measuring 0.5
um by 3 um
• Acid-fast (once stained,
cannot be decolorized by
acid alcohol)
From infection to disease
• the risk of developing disease after being
infected depends largely on endogenous
factors, such as the individual's immunity
• primary tuberculosis –
– Clinical illness directly following infection
– common among children up to 4 years of age and
among immunocompromised persons
• secondary (or postprimary) tuberculosis
– Dormant bacilli persisting for years before
reactivating
– Mostly in adults
– Pulmonary findings
Pathogenesis and Immunity
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Infection and Macrophage Invasion
Virulence of Tubercle Bacilli
Innate Resistance to Infection
The Host Response
– phagosomes and lysosomes occurs
– bacilli begin to multiply, ultimately
killing the macrophage
Pathogenesis and Immunity
• Granuloma Formation
– macrophages
• The Macrophage-Activating Response
– Caseous necrosis
• The Delayed-Type Hypersensitivity Reaction
• Role of Macrophages and T lymphocytes
• Mycobacterial Lipids and Proteins
Immunity
• Skin Test Reactivity
– PPD Skin test:
– Due to delayed-type sensitivity
– Coincident with immunity
– Positive Tuberculin Skin Test (TST): wheal
• > 5mm on un-vaccinated persons
• >10 mm on vaccinated persons
• After 72 hours
Clinical Manifestations
• PULMONARY
• EXTRA-PULMONARY
Pulmonary TB
• Primary
– Mostly seen in children
– most inspired air is distributed to the
middle and lower lung zones, these areas
of the lungs are most commonly involved in
primary tuberculosis
– lesion heals spontaneously and may later
be evident as a small calcified nodule
(Ghon lesion)
– immunocompromised persons develop
miliary TB
Pulmonary TB
• Secondary (Postprimary)
– adult-type, reactivation
– localized to the apical and posterior
segments of the upper lobes, where
the substantially higher mean
oxygen tension favors mycobacterial
growth
– small infiltrates to extensive cavitary
disease
Clinical Manifestations
• fever and night sweats, weight loss, anorexia,
general malaise, and weakness
• cough eventually develops—often initially
nonproductive and subsequently
accompanied by the production of purulent
sputum, sometimes with blood streaking
• Often with no physical findings
Extrapulmonary TB
• Lymph-Node Tuberculosis
– frequent among HIV-infected patients
– historically referred to as scrofula
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Pleural TB
TB of upper airways
Genitourinary TB
TB Meningitis and Tuberculoma
Gastrointestinal TB
Extrapulmonary TB
• Skeletal TB
– reactivation of hematogenous foci
or to spread from adjacent
paravertebral lymph nodes
– spine in 40% of cases, the hips in
13%, and the knees in 10%
– Spinal tuberculosis (Pott's disease
or tuberculous spondylitis)
– With advanced disease, collapse of
vertebral bodies results in kyphosis
(gibbus)
Extrapulmonary TB
• Miliary TB
– Disseminated TB
– yellowish granulomas 1–2 mm in diameter that
resemble millet seeds
– chest radiography reveals a miliary reticulonodular
pattern
Diagnosis
• High index of suspision
• XRAY consistent with TB
• AFB microscopy:
– Sputum exam
– Tissue biopsy
• Culture
– Gold standard
Treatment
• DOTS ( Direct Observed Treatment Strategy)
– Treatment partner