Infectious Flashcards

Question

**What does a serology profile of VCA IgM⁺, VCA IgG⁻, EBNA-1 IgG⁻ suggest** ⁉️

Answer 1

⚠️ **Possible acute infection or non-specific result** 💡 Further testing is required

Answer 2

🚨 **Acute EBV infection**

Answer 3

✅ **Past EBV infection** (immunity established)

Answer 4

⚠️ **Indeterminate** – could be acute or past infection 💡 Further testing required

Answer 5

⚠️ **Late primary infection or reactivation**

Answer 6

⚠️ **Past infection or non-specific finding** 💡 Further testing required

Answer 7

🧠 **Chickenpox** : Varicella zoster virus 🧠 **HFMD** : Coxsackievirus (Enterovirus group) 🧠 **HSV** : 🔹 HSV-1 → Lips, skin 🔹 HSV-2 → Genitalia

Answer 8

⏳ **Incubation** : 🔸 Chickenpox: 14–21 days 🔸 HFMD: 3–6 days 🔸 HSV: Variable 🛑 **Transmission** : 🔸 Chickenpox: Droplets, contact, transplacental 🔸 HFMD: Fecal-oral, droplets 🔸 HSV: ➡️ HSV-1: Saliva, contact ➡️ HSV-2: Sexual, birth canal

Answer 9

✅ Fever, headache ✅ Papulovesicular rash (in crops) over 3–5 days 🔹 **Pleomorphic** : different stages at once 🔹 Starts on head/trunk ➡️ spreads to limbs 🔹 Pruritic (itchy) ✅ Heals without scarring unless secondarily infected

Answer 10

🔹 Low-grade fever (usually summer) 🔹 **Vesicular lesions** on hands, feet, and mouth 🔹 Often mild or asymptomatic 🧠 Enteroviral, short course

Answer 11

🚩 **Gingivostomatitis** (common in 10m–3yrs): 🔸 Painful vesicles on lips, tongue, palate, mouth 🔸 High fever 🔸 Poor feeding → dehydration risk ⚠️ **Eczema herpeticum** : severe, widespread HSV in atopic skin 🧠 May persist up to 2 weeks

Answer 12

👏 **C. HSV-1 gingivostomatitis** HSV-1 gingivostomatitis presents with painful mouth ulcers, fever, and dehydration in toddlers.

Answer 13

🧪 **Chickenpox** : Clinical + vesicular fluid PCR 🧪 **HFMD** : Clinical diagnosis 🧪 **HSV** : 🔹 Clinical for gingivostomatitis 🔹 Tzanck smear (multinucleated giant cells) 🔹 PCR if encephalitis suspected

Answer 14

🚨 **Skin** : Secondary bacterial infection (Staph, GAS) 🚨 **CNS** : Encephalitis (early, good prognosis), meningitis, cerebellitis 🚨 **Respiratory** : Pneumonia 🚨 **Others** : Progressive disease in immunocompromised

Answer 15

✅ Generally mild ⚠️ **Main risk** : Dehydration due to painful ulcers 🧠 Other enterovirus syndromes: 🔻 Herpangina 🔻 Meningoencephalitis 🔻 Myocarditis 🔻 Pleurodynia 🔻 Neonatal sepsis

Answer 16

🚨 **Skin** : Eczema herpeticum, herpetic whitlow 🚨 **Eye** : Keratoconjunctivitis 🚨 **Neonates** : Disseminated HSV, sepsis 🚨 **CNS** : HSV encephalitis → high mortality, neuro sequelae ⚠️ Recurrent HSV may cause **erythema multiforme** (target lesions)

Answer 17

💊 **Chickenpox** : ✅ Supportive (no aspirin!) ✅ Antipyretics, antipruritics ✅ VZV vaccine (live attenuated) ✅ VZV Ig for immunocompromised 💊 **HFMD** : ✅ Supportive only (hydration, antipyretics) ❌ No vaccine 💊 **HSV** : ✅ Supportive (hydration, pain control) ✅ **Acyclovir** for severe, disseminated, or encephalitis ❌ No vaccine

Answer 18

👏 **B. Herpetic whitlow** ## footnote Herpetic whitlow is a painful vesicular lesion on fingers caused by HSV, especially with finger-sucking habits.

Answer 19

🧠 **Cause** : Reactivation of latent **Varicella-Zoster Virus (VZV)** 🔹 Primary VZV = Chickenpox (varicella) 🔹 Reactivated VZV = Shingles (herpes zoster)

Answer 20

🚩 **Dermatomal** vesicular rash ➡️ Localized to sensory nerve distribution (commonly thoracic) 🔸 Preceded by pain or burning 🔸 **Vesicles follow pain** ✅ Unlike adults, **neuralgia is rare** in children

Answer 21

⚠️ Children who had **chickenpox in the first year of life** ⚠️ **Immunocompromised** children (e.g., HIV) → 🔻 Risk of **multidermatomal or recurrent** zoster 🔻 Risk of **disseminated severe disease**

Answer 22

➡️ **Respiratory secretions** ➡️ **Vesicular fluid**

Answer 23

👏 **C. Herpes zoster (shingles)** ## footnote Shingles in children may follow early-life chickenpox and presents as a painful vesicular rash in a dermatomal pattern.

Answer 24

🧠 **Hepatitis A** : 🔸 RNA virus (Picornavirus) 🔸 Incubation: 15–30 days 🔸 Transmission: Fecal-oral (person-to-person) 🧠 **HIV/AIDS** : 🔸 Retrovirus (HIV-1 or HIV-2) 🔸 Incubation: Weeks–years 🔸 Transmission: • **Vertical (most common in infants)** • Horizontal (blood, sexual, IV drug)

Answer 25

🚩 Often asymptomatic or nonspecific ➡️ **Pre-icteric stage** : Fever, malaise, vomiting, nausea ➡️ **Icteric stage** : Jaundice, hepatomegaly, RUQ pain ➡️ **Convalescence** : Gradual resolution over weeks ✅ Prognosis: Excellent in children ⚠️ Rare complication: Fulminant hepatic failure

Answer 26

⚠️ May be **asymptomatic** or have: 🔸 Fever, FTT (failure to thrive), diarrhea 🔸 Severe oral thrush, lymphadenopathy 🔸 Recurrent bacterial/viral infections 🔸 Hepatosplenomegaly, parotid swelling 🔸 HIV encephalopathy, developmental delay

Answer 27

🔹 **N** : Asymptomatic 🔹 **A** : Mild (lymphadenopathy, parotid enlargement) 🔹 **B** : Moderate (recurrent infections, candidiasis, LIP, chronic diarrhea) 🔹 **C** : Severe (PCP pneumonia, encephalopathy, malignancy, growth failure)

Answer 28

🔬 Diagnosis: 1. CBC 2. LFTs: • ALT/AST ⬆️ • ALP normal • Total/direct bilirubin ⬆️ • PT important for prognosis 3. Serology: **HAV IgM = acute, IgG = past** 💊 Treatment: Supportive ✅ Prognosis: Excellent

Answer 29

🔬 Diagnosis: 1. **DNA PCR** (<18 months) 2. Serology (may be false +ve from maternal Ab) 3. Monitored by CD4 count, viral load 🔎 EBV serology and flow cytometry help rule out other causes ✅ **DNA PCR x2 negative in first 3 months = uninfected**

Answer 30

💊 **Treatment** : 1. **ART** : Zidovudine, Lamivudine, Protease inhibitors 2. **PCP prophylaxis** : Cotrimoxazole 3. Treat infections aggressively ✅ Nutritional & developmental support ✅ Multidisciplinary follow-up (growth, vaccines)

Answer 31

✅ **Prevention measures** : 1. Maternal ART during pregnancy 2. Elective C-section 3. Avoid breastfeeding 4. Zidovudine to infant (6 weeks) 🚫 Avoid prolonged ROM, instrumentation ✅ Transmission risk ↓ to <1%

Answer 32

👏 **D. HIV DNA PCR** ## footnote In infants under 18 months, maternal antibodies can yield false-positive serology; DNA PCR is the most accurate.

Answer 33

🧠 **Scarlet Fever** : 🔸 Group A β-hemolytic Streptococcus (GAS) 🔸 Pyrogenic exotoxin 🔸 Transmission: **Droplets** 🧠 **Pertussis** : 🔸 Bordetella pertussis (Gram-negative coccobacillus) 🔸 Highly contagious 🔸 Transmission: **Droplets**

Answer 34

⏳ **Scarlet Fever** : 2–7 days ⏳ **Pertussis** : 7–10 days (range 5–21 days)

Answer 35

1️⃣ **Fever** , sore throat, headache 2️⃣ **Strawberry tongue** : • Day 1: White • Day 3: Red 3️⃣ **Sandpaper rash** : • Starts neck ➡️ trunk, extremities • Pastia’s lines in flexures 4️⃣ **Face** : Red cheeks with **circumoral pallor** 5️⃣ Rash fades in 4–5 days with **desquamation**

Answer 36

🚩 **Catarrhal stage (1–2 wks)** : • Coryza, low-grade fever 🚩 **Paroxysmal stage (2–6 wks)** : • Spasmodic coughing ➡️ inspiratory “whoop” • **Post-tussive vomiting** , apnea, cyanosis 🚩 Convalescent stage (1–2 wks): • Gradual decline in severity 🧠 Cough may last up to **3 months** = “100-day cough”

Answer 37

🧪 **Scarlet Fever** : • Clinical ± throat swab • **Anti-streptolysin O (ASO)** titer 🧪 **Pertussis** : • **PCR or ELISA** from nasopharyngeal swab • CBC: **Absolute lymphocytosis** • CXR if respiratory symptoms

Answer 38

🚨 Otitis media 🚨 Rheumatic fever 🚨 Post-streptococcal glomerulonephritis (PSGN) 🚨 Reactive arthritis 🧠 Cervical lymphadenopathy

Answer 39

🚨 Apnea, pneumonia 🚨 Encephalopathy, convulsions, ICH 🚨 Retinal/subconjunctival hemorrhage 🚨 Hernia, rectal prolapse, malnutrition 🚨 OM, bronchiectasis, pneumothorax

Answer 40

💊 **Treatment** : • Penicillin V x 10 days • Antipyretics 🚫 **No vaccine** ✅ Isolation recommended

Answer 41

💊 **Treatment** : • **Macrolides** = drug of choice • Admit if young/severe/apnea • O₂ therapy if desaturation ✅ **Prevention** : • **DPT vaccine** • Macrolides to close contacts • Vaccinate unimmunized infants

Answer 42

👏 **B. Scarlet fever** ## footnote Scarlet fever has classic features of strawberry tongue, sandpaper rash, and circumoral pallor.

Answer 43

🧠 **RMSF** : 🔸 Rickettsia rickettsii (Gram-negative, intracellular) 🔸 Vector: Tick bite (Reservoir: Dogs) 🔸 Incubation: 2–14 days 🧠 **Typhoid (Enteric) Fever** : 🔸 Salmonella typhi / paratyphi 🔸 Transmission: Feco-oral (contaminated food/water) 🔸 Incubation: 3–30 days

Answer 44

🚨 Sudden high-grade fever 🚨 Severe headache, chills, myalgia 🚨 Rash (maculopapular ➡️ petechial): • Involves **palms, soles, wrists, ankles** 🚨 GI: Diarrhea, abdominal pain 🚨 Others: Pneumonitis, myocarditis, renal failure 🧠 Tick bite history + rash + fever = classic triad

Answer 45

🔸 **Fever** : Step-ladder pattern, relative bradycardia 🔸 **Abdominal pain**, diarrhea/constipation (2nd week) 🔸 **Rose spots** on trunk 🔸 **Hepatosplenomegaly** 🔸 Non-specific: headache, myalgia, anorexia 🧠 Resolves gradually in 2–4 weeks if uncomplicated

Answer 46

🧪 Clinically + 🔹 CBC: Anemia, thrombocytopenia 🔹 Electrolytes: **Hyponatremia** 🔹 LFT: Elevated AST/ALT 🔹 Serology / PCR for confirmation

Answer 47

🧪 CBC: Variable WBC & platelets 🧪 Blood culture (1st week – 80–90% positive) 🧪 Stool & urine cultures (later weeks) 🧪 Bone marrow culture: Most sensitive 🧪 **Widal test** (limited value)

Answer 48

🚨 **RMSF** : • Shock, DIC • Renal failure, myocarditis • Meningoencephalitis, ARDS • Multiorgan failure 🚨 **Typhoid** : • GI hemorrhage/perforation • Osteomyelitis, GN, hepatitis • Neurologic: Delirium, GBS, ataxia

Answer 49

💊 **RMSF** : • <8 yrs: Doxycycline • >8 yrs: Tetracycline • Macrolides (e.g. Azithromycin) ✅ Home care unless severe 💊 **Typhoid** : • Ceftriaxone, Cefotaxime • Azithromycin, Cefixime • Ampicillin (if sensitive) ⚠️ Hospitalize if systemic signs

Answer 50

🚫 **RMSF** : No vaccine ✅ **Typhoid** : • Live attenuated & killed vaccines available • Used in endemic areas and travelers

Answer 51

👏 **B. Rocky Mountain Spotted Fever** ##footnote 🗝️ RMSF presents with tick exposure, high fever, and petechial rash involving palms/soles 🕵️‍♂️

Answer 52

🧠 **Cause** : Borrelia burgdorferi (spirochete) ➡️ **Transmission** : Tick bite (hosts: sheep, foxes, small mammals) 🗓 **Incubation** : 4–30 days 🌿 **Season** : More common in summer, rural areas

Answer 53

🚩 **Erythema migrans** : • Expanding painless macule at bite site 🚩 **Systemic** : • Fever, headache, myalgia, arthralgia 🚩 **Lymphadenopathy** : Painful ## footnote 🧠 Early signs mimic flu but include a characteristic skin rash

Answer 54

🧠 **Neurologic** : • Facial nerve palsy • Meningoencephalitis • Peripheral neuropathy 🫀 **Cardiac** : • Myocarditis • Heart block (HB) 🦴 **Joint** : • Arthralgia • Large joint arthritis (often recurrent) • Erosive arthritis in ~10%

Answer 55

🔬 Primarily **clinical** 🔹 Serology (IgM/IgG) becomes positive **after 4 weeks** ## footnote ✅ Early diagnosis is clinical to avoid delay

Answer 56

💊 >8 yrs: **Doxycycline** 💊 <8 yrs: **Amoxicillin** 🚨 **Severe neurologic or cardiac disease** : ➡️ **IV 3rd gen cephalosporins** (e.g., ceftriaxone)

Answer 57

💡 **F.A.C.E** = 🔸 **F** acial nerve palsy 🔸 **A** rthritis 🔸 **C** arditis 🔸 **E** rythema migrans ## footnote 👉🏼 “Remember the FACE when biting into a LIME”

Answer 58

👏 **C. Lyme disease** ## footnote Erythema migrans + joint and facial nerve involvement after tick exposure = Lyme disease.

Answer 59

🧠 **TSS (Toxic Shock Syndrome)** : ➡️ Staphylococcus aureus (TSST-1 toxin) ➡️ Group A Streptococcus 🧠 **SSSS (Staphylococcal Scalded Skin Syndrome)** : ➡️ Staph. aureus exfoliative toxins **A & B**

Answer 60

🚨 **Major Criteria** (all required): 1. Fever > 39°C 2. Hypotension 3. Diffuse sunburn-like rash → desquamation (palms & soles) 🚨 **Minor Criteria** (3+): 🔹 Inflamed mucous membranes 🔹 GIT: Vomiting or diarrhea 🔹 Renal: ↑BUN or creatinine 🔹 Liver: ↑LFTs 🔹 Muscle: Myalgia or ↑CPK 🔹 CNS: Confusion, lethargy 🔹 Thrombocytopenia ✅ Must exclude other causes (negative cultures)

Answer 61

🚩 Sudden onset high fever (102–105°F) 🚩 Hypotension → syncope/shock (within 48h) 🚩 Non-purulent conjunctivitis, sore throat 🚩 **Sunburn-like rash** + desquamation 🚩 Watery diarrhea, vomiting ⚠️ Associated with tampon use

Answer 62

🚨 ARDS 🚨 Renal failure 🚨 Myocardial infarction 🚨 Hair and nail loss (1–2 months later) ## footnote ⚠️ Recurrence if not adequately treated

Answer 63

💊 **Supportive** : IV fluids, inotropes 💊 **Antibiotics** : 3rd gen cephalosporin ➕ clindamycin 💊 **Severe cases** : IVIG 💉 **Surgical** : Drain abscesses or infected sites

Answer 64

🧠 **Cause** : Staph. exfoliative toxins A & B ➡️ Neonates: **Ritter disease** – generalized skin peeling ➡️ Infants: Flaky desquamation (face/neck) ➡️ Older children: Localized bullous impetigo, tender scarlet-like rash 🧪 **Nikolsky sign** : +ve (epidermis separates on gentle pressure)

Answer 65

⚠️ Complications: 🔻 Dehydration 🔻 Secondary infection 💊 Treatment: • IV **anti-staph antibiotics** (e.g., flucloxacillin) • Pain control • Monitor hydration + fluids ✅ Healing without scarring

Answer 66

👏 **B. Toxic Shock Syndrome** ## footnote TSS features rapid shock, rash with desquamation, mucous membrane involvement, and systemic signs.

Answer 67

🧠 **Impetigo** : ➡️ Superficial, highly contagious skin infection ➡️ Caused by Staphylococcus aureus or Streptococcus pyogenes 🧠 **Periorbital Cellulitis** : ➡️ Inflammation **anterior to orbital septum** ➡️ Presents with fever, eyelid erythema, tenderness, edema ✅ Unilateral

Answer 68

🚩 Starts as erythematous macules ➡️ Progress to **vesicular/pustular or bullous lesions** ➡️ Vesicle rupture ➡️ **honey-colored crust** ⚠️ Spreads by **autoinoculation** 📍 Sites: Face, neck, hands

Answer 69

💊 Mild: **Topical mupirocin** 🚫 Children should not attend school/daycare **until lesions dry** ⚠️ **Complications** : Abscess, meningitis, cavernous sinus thrombosis

Answer 70

💊 Treated urgently with **IV antibiotics** (e.g. ceftriaxone) 📸 **CT or MRI** if orbital cellulitis suspected 👁 Ophthalmology consult if posterior spread suspected

Answer 71

🧠 **Periorbital cellulitis: ➡️ Involves tissues **anterior to orbital septum** ➡️ No visual changes or eye movement restriction 🚨 Orbital cellulitis (posterior): ➡️ Risk of vision loss, abscess, or CNS complications ➡️ Requires imaging and urgent intervention

Answer 72

👏 **C. Impetigo** ## footnote Classic honey-colored crusts after vesicle rupture = hallmark of impetigo.

Answer 73

🦠 **Viral** : 1. **HHV-6/7** ➡️ Roseola infantum (<2 years) 2. **Enteroviruses** 3. **Parvovirus B19** ➡️ Slapped cheek (school age) 4. **Measles & Rubella** ➡️ Uncommon if immunized

Answer 74

1. **Scarlet Fever (GAS)** 2. **Toxic Shock Syndrome (TSS)** 3. **Rheumatic Fever** ➡️ Erythema marginatum 4. **Typhoid Fever** ➡️ Rose spots 5. **Lyme Disease** ➡️ Erythema migrans

Answer 75

🔹 **Viral** : • **Varicella zoster** (Chickenpox, Shingles) • **HSV** • **Coxsackie virus** (HFMD) 🔹 **Bacterial** : • **Impetigo** (crusted) • **Boils** • **Staph bullous impetigo** • **SSSS** (Scalded skin syndrome) 🔹 **Other** : • **SJS/TEN** • **Erythema multiforme**

Answer 76

🔸 **Bacterial** : • **Meningococcemia** • **Other bacterial sepsis** • **Infective endocarditis** 🔸 **Viral** : • **Enteroviruses, adenoviruses** 🔸 **Other** : • **ITP** • **HSP** (Henoch-Schönlein purpura) • **Vasculitis** • **Malaria**

Answer 77

💡 **Mnemonic: “Very Sick Person Must Take Double Tablets”** 1️⃣ Varicella – Day 1 2️⃣ Scarlet fever – Day 2 3️⃣ Smallpox – Day 3 4️⃣ Measles – Day 4 5️⃣ Typhus – Day 5 6️⃣ Dengue – Day 6 7️⃣ Typhoid – Day 7

Answer 78

🔹 **Macule** : Flat pink lesion – **blanching** 🔹 **Papule** : Raised solid lesion – **blanching** 🔹 **Vesicle** : Clear fluid-filled <0.5 cm 🔹 **Bulla** : Clear fluid-filled >0.5 cm 🔹 **Pustule** : Pus-filled raised lesion

Answer 79

👏 **C. Parvovirus B19**

Answer 80

👏 **B. Meningococcemia**

Answer 81

🧠 **Primary herpetic gingivostomatitis** ## footnote ➡️ Caused by **Herpes Simplex Virus type 1 (HSV-1)** ➡️ Common in infants aged 6 months to 5 years ➡️ Features: fever, irritability, painful vesicles/ulcers on lips, tongue, hard palate

Answer 82

✅ **Viral clues** 🕵️‍♂️: 🔹 Conjunctivitis 🔹 Coryza 🔹 Cough 🔹 Diarrhea 🔹 Viral exanthem

Answer 83

💊 **Supportive care** ✅ Oral **analgesics** ✅ **Adequate hydration** ➡️ Most cases resolve spontaneously within 1–2 weeks ## footnote ⚠️ Start **oral acyclovir** only if early and severe

Answer 84

👏 **E. Analgesics and hydration** ## footnote Primary HSV gingivostomatitis in infants is typically self-limited and treated supportively.

Answer 85

🧠 **Cause** : Enterobius vermicularis (Pinworm) – a 1 cm threadlike nematode ➡️ **Transmission** : Feco-oral ## footnote ⚠️ **Autoinfection** common in children with finger-sucking habits

Answer 86

🔹 Often **asymptomatic** 🔸 **Anal itching** , worse at **night** 🔸 Sleep disturbances, **restlessness** , and **enuresis** ##footnote 🧠 Pruritus ani is hallmark

Answer 87

🔬 **Cellophane tape test** : • Tape applied to perianal area at night • Microscopy reveals **eggs or adult worms** ✅ Done in the **early morning**

Answer 88

💊 **Albendazole** 400 mg PO → repeat after 2 weeks 💊 **Mebendazole** 100 mg PO → repeat after 2 weeks ➡️ Treat **entire household** simultaneously

Answer 89

🧼 **Hand hygiene** is the most effective prevention 🚿 Treat household contacts even if asymptomatic 🧠 Reinfection is common without proper hygiene

Answer 90

👏 **C. Cellophane tape test** ## footnote **The perianal adhesive tape test is the gold standard for diagnosing pinworm infection** .

Answer 91

🧠 **Cause** : Entamoeba histolytica ➡️ Transmission: **Feco-oral route** ## footnote ⚠️ Common in areas with poor sanitation

Answer 92

🔸 **Asymptomatic carriers** (majority) 🔸 **Amebic dysentery** (5–10%): • Age: 1–5 years • Gradual onset abdominal cramps • Frequent stools with **tenesmus** • **Heme-positive** stool 🧠 Fever present in only 1/3 of cases

Answer 93

🔬 **Stool microscopy** : • Detects **cysts** (3 samples ⬆️ sensitivity) 🔬 **Stool antigen test** or **PCR** : • More specific for E. histolytica

Answer 94

💊 **Symptomatic** : • **Metronidazole** (DOC) • Tinidazole (alternative) 💊 **Asymptomatic** : • **Paromomycin** or **Iodoquinol** ## footnote 🧠 Luminal agents needed to prevent transmission

Answer 95

👏 **B. Amebic dysentery** ## footnote Gradual-onset bloody diarrhea without fever is typical of amebic dysentery caused by E. histolytica.

Answer 96

🧠 **Transmission** : Bite of **female sandfly** 🦠 **Cause** : Leishmania species (protozoan parasite)

Answer 97

🔸 Occurs on **exposed skin** ➡️ Papule ➡️ Nodule ➡️ **Painless ulcer** ✅ **Heals with scar** ## footnote 🧠 Often self-limited but disfiguring

Answer 98

🚨 **High fever** 🚨 **Massive splenomegaly** 🚨 **Severe cachexia** ## footnote 🧠 Often seen in children <5 years 🧠 Reticuloendothelial hyperplasia: Liver, spleen, bone marrow, lymph nodes

Answer 99

⚠️ Massive hepatosplenomegaly ⚠️ Profound **anemia** ⚠️ **Bleeding episodes** (esp. epistaxis) ⚠️ **Secondary infections** 🚨 Mortality >90% without treatment

Answer 100

💊 **Sodium stibogluconate** (Pentostam) 💊 **Amphotericin B** for resistant/severe cases ## footnote ⚠️ Early treatment prevents fatal outcomes

Answer 101

👏 **C. Visceral Leishmaniasis (Kala-azar)** ## footnote **Classic triad + severe cachexia and hepatosplenomegaly point to visceral leishmaniasis** .

Answer 102

🧠 **Key features** : 🔸 High fever, chills 🔸 Headache, myalgia 🔸 **Anemia** 🔸 **Thrombocytopenia** 🔸 **Metabolic acidosis** 🔸 Mild hepatosplenomegaly ## footnote ⚠️ Travel to **endemic area (e.g. Africa)** is a major clue 🕵️‍♂️

Answer 103

✅ **Thick blood smear + rapid diagnostic test (RDT)** ➡️ Thick smear: Detects **parasites** ➡️ RDT: Detects **antigens** from Plasmodium species 🧠 **Giemsa stain = gold standard for smear**

Answer 104

🚩 No chemoprophylaxis taken 🚩 Slept outdoors in an endemic area 🚩 Returned from **Africa** (high transmission region) ✅ These increase risk of **severe falciparum malaria**

Answer 105

👏 **D. Thick blood smear + rapid test** ## footnote **Malaria is confirmed by thick smear (parasite detection) and rapid antigen testing. All other tests are irrelevant for first-line diagnosis** .

Answer 106

🧠 **Definition** : ➡️ Fever >38.3°C (101°F) **at least once daily** ➡️ Duration: • >1 week in infants & young children • >2–3 weeks in adolescents ➡️ **No diagnosis** after thorough initial evaluation

Answer 107

🦠 **Bacterial** : • TB, infective endocarditis, UTI, typhoid, brucellosis • Cat-scratch disease, osteomyelitis, septic arthritis, liver abscess 🦠 **Viral** : • HIV, EBV, CMV, adenovirus 🦠 **Parasitic** : • Malaria, toxoplasmosis

Answer 108

🚨 **Malignancies** : 🔸 Leukemia 🔸 Lymphoma 🔸 Neuroblastoma 🔸 Sarcoma

Answer 109

🧬 CTD / Autoimmune: 🔹 Juvenile idiopathic arthritis 🔹 Kawasaki disease 🔹 Systemic lupus erythematosus (SLE) 🔹 Rheumatic fever

Answer 110

🔹 **Drug fever** (vancomycin) 🔹 **Factitious fever** (Munchausen by proxy) 🔹 **Immunodeficiency* 🔹 **IBD** (Inflammatory bowel disease) 🔹 **Periodic fever syndromes** (e.g., FMF) 🔹 **Diabetes insipidus** 🔹 **Familial dysautonomia**

Answer 111

✅ **Thorough history & physical exam** is most important 🔬 Investigations may include: • CBC, CRP, ESR, PCT • Urine C&S, TB skin test • Viral serologies • Imaging: X-ray, bone marrow aspiration ## footnote ⚠️ **Avoid premature antibiotics** — may obscure diagnosis

Answer 112

👏 **C. Conduct thorough history and physical exam** ## footnote **Good clinical history and examination is the cornerstone of PUO evaluation before advanced testing** .

Answer 113

🧠 To identify **low-risk** infants for **serious bacterial infections (SBI)** ➡️ Helps guide outpatient vs inpatient management

Answer 114

✅ **All must be present** : 1. **Well-appearing** 2. **Full term** birth (≥37 weeks) 3. **Previously healthy** 4. No signs of skin, soft tissue, skeletal, or ear infection 5. WBC count: **5,000–15,000/mm³** 6. Bands: **<1,500/mm³** 7. UA: WBCs **<10/hpf** 8. If diarrhea: Fecal leukocytes **<5/hpf**

Answer 115

✅ **<1%** risk of SBI ⚠️ If not all criteria are met ➡️ **risk increases to 7–9%**

Answer 116

👏 **D. Born at 36 weeks gestation** ## footnote **Preterm birth (<37 weeks) is an exclusion criterion for low-risk classification under Rochester Criteria** .

Answer 117

🫁 **Most common site** : Lung apex ✅ **Good immunity** → Ghon focus → fibrosis + calcification ⚠️ **Low immunity** → spread to lymph nodes and other organs

Answer 118

📍 **Ghon focus** : Caseating granuloma beneath pleura 📍 **Ghon complex** : • Ghon focus • Ipsilateral hilar lymphadenopathy • Lymphangitis

Answer 119

🔹 **90% asymptomatic** 🔸 Chronic cough (main symptom) 🔸 Recurrent infections unresponsive to antibiotics 🧠 Systemic: • Weight loss • Night sweats • Low-grade fever • Loss of appetite

Answer 120

1️⃣ Inhaled TB phagocytosed by macrophages 2️⃣ TB blocks phagolysosome fusion 3️⃣ Local infection → granuloma forms in 3 weeks 4️⃣ Central caseous necrosis → **Ghon focus** ✅ TB is held in check if immunity intact

Answer 121

🧠 TB meningitis 🫁 Pleural TB 🦴 Spinal TB (Pott’s) 🧬 Genitourinary TB 🌿 TB lymphadenitis 🍽 TB peritonitis 💡 Disseminated TB = **Miliary TB**

Answer 122

🧪 CBC: Lymphocytosis, ↑ESR 🧪 Tuberculin test (PPD): • <5 mm = Negative • ≥10 mm = Positive (infection or vaccine) • ≥15 mm = True infection 🧪 Sputum: Ziehl-Neelsen stain, **Lowenstein-Jensen culture** (4 wks), **BACTEC** (10 days) 🧪 PCR / Quantiferon TB gold / LN biopsy

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🩺 **Duration** : 6 months (can extend to 9 months) ➡️ **Intensive phase (0–2 months)** : • INH + Rifampin + Pyrazinamide + Ethambutol ➡️ **Continuation phase (2–6 months)** : • INH + Rifampin

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💊 **INH** : Peripheral neuropathy ➡️ give Vit B6 💊 **Rifampin** : Orange-red body fluids 💊 **Pyrazinamide** : Hyperuricemia (Gout) 💊 **Ethambutol** : Optic neuritis 💊 **Streptomycin** : Ototoxicity, nephrotoxicity

Answer 125

🧠 **Surgical excision** of infected lymph nodes ✅ Both **diagnostic** and **therapeutic**

Answer 126

🧫 **Slow-growing NTM** 🌊 Found in **tap water** 🫁 **Pulmonary disease** : • TB-like symptoms (cough, fever, hemoptysis, cavitation) 🧪 Mimics TB radiologically and clinically

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💊 **Rifampicin + Ethambutol** ## footnote 🧠 Similar to part of TB treatment, but without INH or PZA

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🧫 Actinomyces israelii ➡️ Anaerobic, **Gram-positive filamentous rod** ➡️ **Not acid-fast** ✅ Normal flora of mucosal surfaces (mouth, GI, GU)

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⚠️ Poor oral hygiene ⚠️ Dental trauma or procedures ⚠️ Periodontal disease 🧠 Endogenous infection after mucosal barrier is breached

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🔸 Large, firm **jaw mass** 🔸 Fibrosis and **abscess** formation 🔸 **Draining sinus tracts** with pus along jaw/neck 🧠 Most common presentation (50%)

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🫁 **Thoracic** 🍽 **Abdominal** 🧬 **Pelvic** (e.g., IUD-associated infections)

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🔬 **Gram-positive** , filamentous, **non–acid-fast** rods 🧠 Appear purple on Gram stain 🟣 Can form “sulfur granules” in pus

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💊 **Penicillin** ✅ ➡️ Long-term treatment often needed (weeks to months) ## footnote 🧠 Alternatives (if allergic): Doxycycline, Clindamycin

Answer 134

👏 **E. Penicillin** ## footnote **Actinomyces is treated with long-term penicillin; it’s gram-positive, filamentous, and not acid-fast** .

Answer 135

🦠 **Streptococcus pyogenes (Group A Strep)** 🦠 **Staphylococcus aureus** ## footnote ✅ These are the most frequent pathogens in **acute bacterial lymphadenitis**

Answer 136

💊 **Cephalexin** ➡️ Covers both **Streptococcus** and **Staphylococcus** ## footnote 🧠 Adjust if MRSA suspected or no response

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🧠 **Lymphangitis** = infection of **lymphatic vessels or nodes** ➡️ Usually a complication of **bacterial cellulitis** 🦠 Most common cause: **Streptococcus pyogenes (Group A Strep)**

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💊 **Cephalexin** ➕ **Warm compresses** ## footnote ✅ Treats streptococcal origin and promotes drainage

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🚨 **Thrombosis** of adjacent veins 🚨 **Sepsis** ## footnote 🧠 Requires prompt treatment to prevent systemic spread

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🦠 **Bartonella henselae** 🐱 Transmission: **Cat bite or scratch** (present in ~90% of cases) ## footnote 🧠 Most common cause of **chronic lymphadenitis** in children

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🔸 **Red papule** at scratch site 🔹 Regional **lymphadenopathy** (tender, erythematous, may suppurate in 10–40%) 📍 Most commonly involved nodes: • **Axillary** (most common) • Cervical, submandibular, preauricular

Answer 142

🔬 **Serology** (antibody detection) 🧪 **PCR** for Bartonella DNA ## footnote ✅ Often clinical diagnosis in typical presentations

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✅ **Supportive management** in most cases 🧠 **Antibiotics** (e.g., azithromycin) may be used in **moderate/severe** or **suppurative cases**

Answer 144

👏 **C. Cat Scratch Disease** ## footnote **Bartonella henselae from a cat scratch causes CSD, which presents with regional lymphadenopathy and a red lesion at the scratch site** .

Answer 145

🧠 **Rabies virus** = Single-stranded RNA virus ➡️ Family: **Rhabdovirus** 🐶 Transmitted via **infected animal saliva** (bite/scratch)

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🧠 **Infects neurons** ➡️ Travels **retrograde** from peripheral nerves to the brain ⚠️ Causes fatal **encephalitis**

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🚨 Most common form 🔹 **Hydrophobia** (pharyngeal spasms) 🔹 **Aggressive behavior** 🔹 **Autonomic overactivation** ## footnote ⚠️ Common in dog bites (especially in developing countries)

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🔸 Less common form 🔹 **Paresthesia** 🔹 **Ascending paralysis** ## footnote 🧠 May resemble Guillain-Barré Syndrome

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✅ **Wound cleaning** ✅ **Passive immunization** (Rabies Immunoglobulin) ✅ **Rabies vaccine (active immunization)** 🚨 If symptoms appear before treatment → **almost always fatal**

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✅ **Confine and observe the dog for 10 days** 🧠 If the dog shows symptoms → start PEP 🧠 If the dog stays healthy → no treatment needed

Answer 151

🦠 **Staphylococcus aureus** = most common cause 🚩 **Acute monoarthritis** with: • Fever, chills, malaise • Red, swollen, warm joint • Pain and restricted movement ## footnote 🧠 Hip/knee commonly affected

Answer 152

🔍 Joint **ultrasound** : detect effusion 💉 **Arthrocentesis** (aspiration): diagnostic and therapeutic 🧪 Labs: • ↑ WBC • ↑ ESR, CRP • Blood cultures

Answer 153

✅ **Urgent joint drainage** (aspiration or surgical) ✅ **IV antibiotics** (e.g., ceftriaxone or anti-staph agents) 💊 Pain control and supportive care ## footnote ⚠️ Delay increases risk of permanent joint damage

Answer 154

👏 **C. Joint drainage + IV antibiotics** ## footnote This is classic septic arthritis; drainage and IV antibiotics are urgent to prevent joint damage.

Answer 155

🦠 Brucella spp. (intracellular Gram-negative coccobacilli) • B. melitensis, B. suis, B. abortus, B. canis 🐄 **Transmission** : • Ingestion of **unpasteurized dairy** (raw milk, cheese) • Direct contact with infected animals

Answer 156

🔸 **Undulant fever** (comes and goes) 🔸 Malaise, weight loss, **night sweats** , myalgia 🔸 **Arthralgia** , sacroiliitis 🔸 Hepatosplenomegaly ⚠️ Can become **chronic or relapse**

Answer 157

🚨 **Endocarditis** 🚨 **Epididymo-orchitis** 🚨 **Hepatitis** 🚨 **Neurobrucellosis** (e.g., meningitis) 🚨 **Spontaneous abortion** in infected pregnant women

Answer 158

💊 **Doxycycline + Gentamicin** 💊 OR **Doxycycline + Rifampin** ## footnote 🧠 Treatment must be prolonged to prevent relapse

Answer 159

👏 **D. Hepatosplenomegaly** ## footnote Triad of **fever, splenomegaly, and arthralgial arthritis** , points towards Brucellosis.

Answer 160

🧠 **Erythema gangrenosum** = necrotic skin lesions caused by **severe systemic infection** ⚠️ Typically in **critically ill or immunocompromised** patients 🧬 Common in **neutropenic** or malnourished children

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🦠 **Pseudomonas aeruginosa** ✅ ➡️ Other rare causes: Staph, Klebsiella, fungi, viruses 🧠 Gram-negative bacillus with a predilection for bloodstream invasion

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🔴 **Painless red patches** → blister → **black necrotic ulcer** 🟣 **Central necrosis with red halo** 📍 Often in **perineal, axillary, or extremity areas**

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🔬 **Diagnosis** : • Clinical skin exam • **Blood cultures** • Skin **biopsy** for confirmation 💊 **Treatment** : • **Antipseudomonal antibiotics** (e.g., ceftazidime, meropenem) • Surgical debridement if needed ➡️ Adjust therapy based on culture results

Answer 164

👏 **A. Pseudomonas aeruginosa** ## footnote **Erythema gangrenosum in septic neonates is most classically due to Pseudomonas aeruginosa** .

Answer 165

✅ **Hepatitis B (1st dose)** ## footnote 🧠 Protects against perinatal transmission

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✅ **Hepatitis B (2nd dose)** 💉 Continuation of birth series

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💉 **1st doses of** : • DTP-Hib-HepB-IPV combo • Pneumococcal vaccine • Rotavirus vaccine

Answer 168

💉 **3rd doses of** : • DTP-Hib-HepB-IPV • Pneumococcal vaccine • ➕ **bOPV** (oral polio) • ➕ **Start of yearly influenza vaccine**

Answer 169

💉 **1st doses of** : • **MMR** (measles, mumps, rubella) • **Varicella (chickenpox)** • **Hepatitis A**

Answer 170

💉 **2nd doses of** : • DTP-Hib-HepB-IPV • Pneumococcal vaccine • Rotavirus vaccine

Answer 171

💉 **Boosters** : • DTP-Hib-IPV • bOPV • ✅ **Hepatitis A (2nd dose)**

Answer 172

💉 **Seasonal Influenza vaccine** ## footnote 🧠 Given before flu season every year

Answer 173

💉 **Boosters** : • DTP-IPV • ✅ **MMR (2nd dose)**

Answer 174

💉 **HPV vaccine** 🧠 Administered as **2 doses**

Answer 175

💉 **DTP booster (without polio)** ## footnote ✅ To maintain long-term protection

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🧠 **Live attenuated vaccine = weakened form** of the actual virus/bacterium ✅ Must **replicate** in the body to be effective ✅ Mimics **natural infection** ✅ Often **1 dose is sufficient** for long-term immunity

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💉 **Cannot replicate** 🛡️ Immune response is **humoral** (antibodies) ⏳ Multiple doses needed **(3–5 doses)** 🧠 Antibody levels **wane over time**

Answer 178

❌ **NOT live** = • Hepatitis A • Hepatitis B • Injectable polio (Salk) • Injectable influenza • Rabies 🧠 **Mnemonic** : **“Always Be RIP”** = **A (hep A), B (hep B), R (Rabies), I (Injectable influenza), P (Polio – injectable)**

Answer 179

✅ **Live bacterial vaccines** : • **BCG (TB)** • **Oral Typhoid** • **Plague vaccine** (less commonly used) 🧠 Most other bacterial vaccines are killed

Answer 180

⛔ **Anaphylaxis** to vaccine or any component (e.g., egg, gelatin, antibiotics) ⛔ **Moderate-severe illness** with or without fever ⚠️ **Immunocompromised** : Avoid LAV ✅ Exception: **Measles & BCG allowed in HIV patients** if **CD4 >15%**

Answer 181

👏 **C. Rabies** ## footnote Rabies is a killed viral vaccine. MMR, OPV, and Varicella are all live attenuated.

Answer 182

💉 **Administer BOTH** : ✅ **Hepatitis B vaccine (active)** ✅ **HBIG (Hepatitis B immunoglobulin)** (passive) 🧠 Must be given **within 12 hours** of birth ➡️ Prevents perinatal transmission

Answer 183

⚠️ Delay **vaccine** until discharge or 1 month ✅ Still give **HBIG** at birth ➡️ Vaccine efficacy is lower in low-birth-weight neonates

Answer 184

🧠 **Current Hepatitis B infection** ➡️ Baby requires **HBIG + Hep B vaccine at birth**

Answer 185

🧬 **HBsAg** = Infection (acute or chronic) 🧬 **Anti-HBs** = Immunity (from vaccine or resolved infection) 🧬 **Anti-HBc IgM** = Acute infection 🧬 **Anti-HBc IgG** = Past infection or chronic infection 🧬 **HBeAg** = High infectivity 🧬 **Anti-HBe** = Low infectivity

Answer 186

👏 **B. HBIG + Hepatitis B vaccine now** ## footnote HBIG + vaccine within 12 hours is essential to block vertical transmission.

Answer 187

👏 **C. Resolved past infection** ## footnote **Anti-HBc IgG (+) indicates natural exposure, not just vaccination. Absence of HBsAg confirms resolved status** .

Answer 188

🦠 **Streptococcus pneumoniae** (most common overall) 🦠 **Neisseria meningitidis** (esp. with complement deficiency C5–C8) 🦠 **Haemophilus influenzae type B** (Hib, now less common with vaccination)

Answer 189

🚨 Sudden fever, lethargy, irritability 🧠 **Signs of meningeal irritation**: • **Nuchal rigidity** • **Kernig’s sign** • **Brudzinski’s sign** 🔺 **Seizures** , altered consciousness, photophobia ⚠️ **Petechiae → purpura** in meningococcal meningitis

Answer 190

🔺 Headache, emesis, bulging fontanel 🔺 Papilledema 🔺 CN palsies (e.g., abducens) 🔺 Bradycardia + hypertension

Answer 191

🧪 **Lumbar puncture** (LP) 🔬 Confirm with CSF analysis + Gram stain + culture 🩸 Blood cultures should also be drawn

Answer 192

⚠️ **Indications for CT before LP** : • Papilledema • Focal neurologic signs • Coma • History of hydrocephalus or neurosurgery

Answer 193

📊 CSF analysis: • ⬆️ Opening pressure • **WBC** : 300–10,000 (PMNs) • ⬇️ Glucose <40 mg/dL or <50% serum • ⬆️ Protein: 100–500 mg/dL • Positive Gram stain/culture

Answer 194

💊 **Vancomycin + 3rd gen cephalosporin (e.g., ceftriaxone)** ➕ Add **ampicillin** if Listeria is suspected ➕ Use **cefepime/meropenem** if immunocompromised

Answer 195

🔹 **S. pneumoniae** : 3rd gen cephalosporin ± vancomycin 🔹 **N. meningitidis** : Penicillin or ceftriaxone 🔹 **H. influenzae type B** : • Ampicillin (β-lactamase -) • 3rd gen cephalosporin (β-lactamase +)

Answer 196

💉 **Dexamethasone** should be given **1–2 hrs before antibiotics* ✅ Reduces **hearing loss in Hib meningitis** (children >6 weeks)

Answer 197

🧪 **N. meningitidis** : **Rifampin** for all close contacts 🧪 **H. influenzae B** : Rifampin if household has under-immunized <48mo or immunocompromised member 🚫 **S. pneumoniae** : No prophylaxis needed

Answer 198

⚠️ **Neurologic sequelae** in 50% of cases 🔇 **Hearing loss** : most common (esp. with S. pneumoniae) 🔺 Seizures, developmental delay, hydrocephalus 💀 Mortality highest in **pneumococcal meningitis**

Answer 199

👏 **C. Bacterial meningitis (meningococcal)**

Answer 200

لا لا خلَّصنا، وآخرُ دعواهم أن الحمدلله ربِّ العالمين 💡📍

Infectious Flashcards

(230 cards)