🖇 I. OVERVIEW OF FREE-LIVING AMOEBAE

🚨 Primary Safety Concern (Exam Point)

Preventing disease from reaching the brain
Brain infection → CNS damage

📌 Lecture Focus

Highly dangerous group of parasites: Free-Living Amoebae
One type can cause death within 6 days (Exam Point)

🖇 II. CLASSIFICATION OF AMOEBAE

📌 Definition of "Amoeba"

Term denotes pathogenicity (ability to cause disease)

🟠 Four Types of Amoebae:

1. Pathogenic Amoeba

Example: Entamoeba histolytica
Lives in intestine
Can damage blood vessels in intestinal wall
Trophozoite form travels via bloodstream
Can cause Amoebic Brain Abscess

2. Commensal Amoeba

Reside in various sites (especially large intestine)
Do NOT cause harm to humans

3. Opportunistic Amoeba

Typically cause mild disease in strong immunity
Cause severe illness or death in immunocompromised patients (Exam Point)

4. Potentially Pathogenic Free-Living Amoeba

Live, eat, and reproduce in surrounding environment (Exam Point)
Cause infection IF they gain entry into human body

🟣 Genera of Pathogenic Free-Living Amoebae (Exam Point)

Naegleria
Acanthamoeba

🖇 III. NAEGLERIA FOWLERI

🟠 A. TAXONOMY & DANGER

📌 Classification

Genus Naegleria: contains ~47 species
Only 1 species is pathogenic: Naegleria fowleri (Exam Point)
Most dangerous parasite (Exam Point)
Synonym: Naegleria ara
Named after scientist Fowleri

🟠 B. HABITAT & FEEDING

📌 Natural Habitat

Found in fresh water (Exam Point):
- Rivers
- Ponds
- Streams
- Swimming pools
- Hot springs (preferred location)
NOT found in:
- Saltwater
- Brackish water

📌 Seasonal Pattern

Infections more common in summer

📌 Feeding Behavior (Exam Point)

Outside human body: feeds on bacteria
Inside human body: feeds on surrounding tissue (e.g., brain tissue)

🟠 C. MORPHOLOGY & LIFE CYCLE

🚨 N. fowleri exists in 3 forms: (Exam Point)

1. Amoeboid Form (Trophozoite Form)

Pathogenic form
Infective stage
Thermophilic (loves heat) (Exam Point)
Optimal survival conditions: water temperature 35°C to 45°C (Exam Point)

2. Flagellate Form

Rapid, motile stage
Develops when temperature or food supply decreases
Possesses 2 flagella
Function: moves rapidly to find suitable temperature/food
Reverts to Amoeboid form when conditions improve

3. Cyst Form

Develops under highly unfavorable conditions:
- Temperature drops significantly
- Food completely absent

🟠 D. PATHOGENESIS & DISEASE

🟣 Route of Entry (Exam Point)

Primarily through the NOSE

🟣 Mechanism of Infection:

Step-by-Step Process:

Entry via inhalation or "snorting" of contaminated water
- During bathing or swimming
- Water splashing
Amoeba penetrates nasal mucosa
- Causes ulceration
Travels along Olfactory nerve
- Passes through Cribriform plate
- Reaches brain
Immune system launches massive attack
Intense attack → significant inflammation (Exam Point)

🟣 Disease Name & Characteristics

🚨 PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM) (Exam Point)

📌 "Primary" means:

Goes directly to brain (not via bloodstream)

📌 Pattern:

Infection is diffuse (affects entire brain) (Exam Point)

📌 Mechanism of Damage:

Amoeba feeds on brain cells (Amoebic Encephalitis)
Massive immune attack causes:
- Edema
- Hemorrhage
- Necrosis
- Brain damage

🟣 Clinical Manifestations

🚨 Disease Course:

Acute, Rapid, and Fulminant
(Powerful, severe, and sharp)

📌 Timeline & Symptoms:

Day 1 (Initial Symptoms):

Mild fever
Simple headache

Day 2 onwards (Rapid Progression):

High fever
Severe headache
Increased Intracranial Pressure (ICP) (Exam Point)
Vomiting (indicates high ICP)
Meningeal irritation signs:
- Nuchal rigidity
- Kernig's sign
- Brudzinski's sign
Anosmia (loss of smell) - characteristic
Ageusia (loss of taste) - characteristic
May progress to:
- Confusion
- Bulbar palsy
- Coma
- Death

🟣 Clinical Note: Mortality & Death

🚨 Key Statistics: (Exam Point)

Death within 6 days from start of infection
Mortality rate: 97% of cases

🚨 Cause of Death: (Exam Point)

Catastrophic increase in brain pressure
Leads to Brain Herniation

📌 Affected Population: (Exam Point)

Primarily affects children and young adults

🖇 IV. ACANTHAMOEBA

🟠 A. TAXONOMY, MORPHOLOGY & HABITAT

📌 Classification

Genus Acanthamoeba: ~25 species
9-12 species are pathogenic to humans

📌 Name Origin

Named for shape: resembles plant with broad leaves and thin spines

📌 Distinctive Feature (Exam Point)

Possesses spine-like pseudopods

📌 Temperature Preference

Trophozoite form thrives at ~30°C

📌 Habitat - Widespread

Found in any type of water:
- Fresh water
- Salt water
- Brackish water
Any moist environment where bacteria present
Even found in contact lens solutions

🟠 B. MORPHOLOGY & LIFE CYCLE

📌 Acanthamoeba exists in 2 forms:

1. Trophozoite Form

Infective stage
Present under favorable conditions

2. Cyst Form

Forms under unfavorable conditions
Triggers: temperature rises OR drops

🟠 C. PATHOGENESIS & DISEASE

🚨 Key Principle: (Exam Point)

Acanthamoeba does NOT cause systemic disease in immunocompetent individuals
Systemic disease occurs primarily in immunocompromised (Exam Point)

🟣 Routes of Entry & Outcomes:

1. Inhalation (Nose):

In immunocompetent person:
- Descends to lungs
- Causes mild, flu-like symptoms
- Often resolves spontaneously

2. Skin Entry:

Through cuts or abrasions

3. Ocular Entry (Cornea):

Via contaminated contact lens solutions

🟣 Systemic Disease: GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE)

🚨 Target Population: (Exam Point)

Immunocompromised patients

📌 Mechanism:

Amoeba enters body
Travels via bloodstream to brain
Found around blood vessels in brain
Immune reaction → formation of granulomas (single or multiple)

🟣 Understanding Granulomas

🚨 Definition of Granuloma: (Exam Point)

Cluster of cells formed by immune system
Purpose: to wall off (encircle) a pathogen immune system cannot eliminate

📌 Formation Timeline: (Exam Point)

Slow process
Takes weeks, months, or years

🟣 Disease Name & Pathology

🚨 GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE) (Exam Point)

📌 Characteristics:

Localized lesions (granulomas) within brain (Exam Point)
Destroys surrounding brain tissue
Causes increased Intracranial Pressure (ICP)

🟣 Clinical Manifestations (GAE)

📌 Neurological Effects:

Focal neurological deficits (localized)
Correspond to specific site of lesion
Non-specific manifestations from increased ICP

🚨 Disease Course: (Exam Point)

Chronic (unlike PAM which is acute)

📌 Mortality Timeline:

Death may occur after:
- 5-6 months
- Up to 1 year
Depends on patient's immune status
Severe immunocompromise → disseminated disease may occur

🟣 Clinical Note: Amoebic Keratitis

📌 Special Case:

Acanthamoeba causes Amoebic Keratitis (eye infection)
Can occur even in immunocompetent individuals
Associated with:
- Contact lens use
- Contaminated water

🟠 D. COMPARISON: PAM vs GAE (Exam Point)

PRIMARY AMOEBIC MENINGOENCEPHALITIS (PAM) - Naegleria

📌 Pathway:

Direct to brain via Nose/Olfactory nerve

📌 Immune Status:

Affects all, especially children & youth

📌 Pathology:

Diffuse Meningoencephalitis

📌 Course:

Acute/Fulminant

📌 Mortality:

High, rapid (days)

GRANULOMATOUS AMOEBIC ENCEPHALITIS (GAE) - Acanthamoeba

📌 Pathway:

Via Bloodstream

📌 Immune Status:

Primarily immunocompromised

📌 Pathology:

Localized Granulomas/Abscesses

📌 Course:

Chronic

📌 Mortality:

Slower (months to year)

🖇 V. DIAGNOSIS (Clinical Note)

🟠 A. STEPS IN DIAGNOSIS

1. History:

Document recent swimming or fresh water exposure
Especially during summer
Especially in hot springs

2. Imaging:

CT/MRI
Especially in GAE to identify granulomas

3. Lumbar Puncture (LP):

CSF withdrawn
Performed between L3 and L4 (Exam Point)

🟠 B. CEREBROSPINAL FLUID (CSF) ANALYSIS

📌 Typical CSF Findings (Both PAM & GAE):

🚨 Physical Characteristics:

Pressure: Withdrawn under tension (increased)
Appearance: Turbid or grayish-white (pus/inflammation)

🚨 Laboratory Findings:

WBCs: Increased
Protein: Increased
Glucose: Normal or slightly reduced (Exam Point)
- Important: Amoeba feeds on brain cells (not primarily glucose)
- Unlike bacteria which consume glucose

🚨 Microscopy:

Parasite (amoeba) present
No bacteria or fungi (rules out typical bacterial meningitis)

🟠 C. LABORATORY TOOLS

1. Direct CSF Examination:

Look for presence of amoeba

2. Culture: (Exam Point)

Amoebae cultured on Non-Nutrient Media (NN Media) seeded with bacteria
Bacteria included because free-living amoebae need bacteria for feeding outside host

3. PCR:

Rapid diagnostic tool
Highly important
Can be life-saving

🖇 VI. TREATMENT & CONTROL

🟠 A. NAEGLERIA FOWLERI (PAM)

🟣 Management:

Patient MUST be hospitalized

🟣 Medication:

🚨 Amphotericin B (Exam Point)

Very strong and dangerous drug

🟣 Administration:

Intravenously (IV), OR
Intrathecally (directly into spinal fluid)
Purpose: ensure high concentrations in CSF

🟣 Control/Prevention:

Avoid swimming in contaminated water
Maintain swimming pools properly
Increase chlorine concentration

🟠 B. ACANTHAMOEBA (GAE)

🟣 Medication:

🚨 Sulfadiazine (Exam Point)

🟣 Surgical Intervention:

Granulomas may need surgical removal
If feasible and localized

🟣 Co-treatment:

Acanthamoeba often coexists with bacteria in granulomas
Antibiotics administered alongside amoebicidal treatment

🟠 C. ACANTHAMOEBA (KERATITIS)

📌 Treatment:

Specific local treatments utilized
Different from systemic GAE treatment

📌 END OF LECTURE NOTES

Key Focus Areas for Exams:

Classification of amoebae (4 types)
N. fowleri: thermophilic, 3 forms, PAM characteristics
Route of entry via nose/olfactory nerve
PAM vs GAE comparison (pathway, immune status, pathology, course, mortality)
CSF findings (glucose normal/slightly reduced)
Treatment: Amphotericin B (PAM), Sulfadiazine (GAE)
Culture on NN media with bacteria

Parasitology