IDS Malaria, Salmonella, Rabies, HIV, COVID 19 Flashcards
Malaria, Salmonella, Rabies, HIV, COVID 19
What is the pathognomonic histopathologic finding in rabies?
Negri bodies (basophilic cytoplasmic inclusions in brain neurons).
Where are Negri bodies most commonly found?
Purkinje cells of the cerebellum & pyramidal cells of the hippocampus.
Do all infected neurons show Negri bodies?
No, Negri bodies occur in only a minority of infected neurons.
What is the best antemortem test for rabies diagnosis?
RT-PCR from saliva, CSF, or nuchal skin biopsy.
What is the most common cause of death in rabies?
Respiratory failure due to brainstem dysfunction.
What is the primary mode of rabies transmission?
Bite or saliva exposure from an infected animal (e.g., dog, bat).
What is the incubation period of rabies?
Typically 1-3 months (range: 5 days to 1 year).
What are the two major clinical types of rabies?
- Encephalitic (Furious) Rabies, 2. Paralytic Rabies.
What are the key features of Encephalitic (Furious) Rabies?
Hydrophobia, aerophobia, hypersalivation, agitation, autonomic instability.
What are the key features of Paralytic Rabies?
Flaccid, ascending paralysis (resembles Guillain-Barré Syndrome).
What is the recommended post-exposure prophylaxis (PEP) for Category III rabies exposure?
Rabies vaccine + Rabies Immunoglobulin (RIG).
What should be done immediately after a rabies-exposure bite?
Thorough wound washing with soap & water for at least 15 minutes.
Which histopathologic finding is specific to rabies?
Negri bodies in a minority of infected neurons.
Why are Negri bodies not reliable for antemortem diagnosis?
Because they occur in only a minority of infected neurons and are seen postmortem.
What is the most characteristic sign of rabies prodrome?
Paresthesia at the bite site (pathognomonic early symptom).
What is the etiologic agent of HIV?
HIV is caused by the Human Immunodeficiency Virus, a retrovirus that targets CD4+ T cells.
What are the two types of HIV?
HIV-1 (most common worldwide, highly virulent) and HIV-2 (less virulent, primarily in West Africa).
How is HIV transmitted?
Sexual contact, blood exposure (IV drug use, transfusions), perinatal transmission (mother-to-child), occupational exposure.
What is the pathophysiology of HIV?
HIV binds to CD4 receptors and CCR5/CXCR4 co-receptors, integrates into host DNA via reverse transcriptase, leading to progressive CD4+ T-cell depletion.
What are the clinical stages of HIV according to WHO classification?
Stage 1: Acute HIV (flu-like symptoms, high viral load), Stage 2: Chronic HIV (asymptomatic or mild symptoms), Stage 3: AIDS (CD4 <200 or AIDS-defining illness).
What are common opportunistic infections at CD4 <500?
TB, Kaposi sarcoma (HHV-8), Candida oral thrush, Herpes zoster, bacterial pneumonia.
What are common opportunistic infections at CD4 <200?
PCP (Pneumocystis jirovecii pneumonia), PML (Progressive multifocal leukoencephalopathy), Cryptosporidiosis.
What are common opportunistic infections at CD4 <100?
Toxoplasmosis, Cryptococcal meningitis, Chronic diarrhea due to Cryptosporidium.
What are common opportunistic infections at CD4 <50?
CMV retinitis, Mycobacterium avium complex (MAC) infection.
What is the gold standard test for HIV diagnosis?
Western Blot (historical) and HIV RNA PCR; however, 4th Generation HIV Ag/Ab Test is now the standard confirmatory test.
What is the first-line screening test for HIV?
4th Generation HIV Ag/Ab Combo Test (Detects p24 antigen and HIV antibodies).
Which test detects HIV in the earliest stage?
HIV RNA PCR (NAT – Nucleic Acid Test), detects HIV within 1-2 weeks post-exposure.
What is the AIDS-defining CD4 count and key illnesses?
AIDS is defined as CD4 <200 or an AIDS-defining illness such as PCP, CNS lymphoma, Cryptococcus, CMV, or Kaposi Sarcoma.
What is the first-line ART regimen recommended by WHO?
First-line regimen: Tenofovir + Lamivudine (or Emtricitabine) + Dolutegravir (TLD regimen).
When should ART be initiated in an HIV patient?
ART should be initiated immediately in all HIV patients, regardless of CD4 count.
What is the goal of ART in terms of viral load?
Undetectable viral load (<50 copies/mL); U=U (Undetectable = Untransmittable).
What is the post-exposure prophylaxis (PEP) regimen for HIV?
PEP should be started within 72 hours of exposure and consists of Tenofovir + Lamivudine + Dolutegravir for 28 days.
What is the pre-exposure prophylaxis (PrEP) regimen for HIV?
PrEP is used for high-risk individuals (MSM, discordant partners) and consists of daily Tenofovir + Emtricitabine (Truvada).
What are the key side effects of Tenofovir?
Tenofovir can cause nephrotoxicity (Fanconi syndrome) and decreased bone mineral density.
What are the key side effects of Efavirenz?
Efavirenz is associated with neuropsychiatric effects (vivid dreams, depression, dizziness).
What are the key side effects of Protease inhibitors (PIs)?
Protease inhibitors (PIs) can cause hyperlipidemia, insulin resistance, and lipodystrophy.
What is immune reconstitution inflammatory syndrome (IRIS)?
IRIS is a paradoxical worsening of infections after starting ART, due to immune recovery.
How is HIV-related tuberculosis managed?
HIV increases TB risk; Start ART after 2 weeks of TB treatment if CD4 <50, otherwise after 8 weeks.
What is the preferred ART regimen for pregnant HIV patients?
Preferred regimen: Tenofovir + Lamivudine + Dolutegravir; avoid Efavirenz due to teratogenicity.
What is the recommended neonatal prophylaxis for an HIV-exposed infant?
Neonates should receive Zidovudine for 4-6 weeks, with additional prophylaxis for high-risk cases.
What vaccines should be avoided in HIV patients with CD4 <200?
Live vaccines should be avoided in CD4 <200 patients, including BCG, MMR, Varicella, and Yellow Fever vaccines.
What are the two types of HIV?
HIV-1 (most common worldwide, highly virulent) and HIV-2 (less virulent, primarily in West Africa).
How is HIV transmitted?
Sexual contact, blood exposure (IV drug use, transfusions), perinatal transmission (mother-to-child), occupational exposure.
What is the pathophysiology of HIV?
HIV binds to CD4 receptors and CCR5/CXCR4 co-receptors, integrates into host DNA via reverse transcriptase, leading to progressive CD4+ T-cell depletion.
What are the clinical stages of HIV according to WHO classification?
Stage 1: Acute HIV (flu-like symptoms, high viral load), Stage 2: Chronic HIV (asymptomatic or mild symptoms), Stage 3: AIDS (CD4 <200 or AIDS-defining illness).
What are common opportunistic infections at CD4 <500?
TB, Kaposi sarcoma (HHV-8), Candida oral thrush, Herpes zoster, bacterial pneumonia.
What are common opportunistic infections at CD4 <200?
PCP (Pneumocystis jirovecii pneumonia), PML (Progressive multifocal leukoencephalopathy), Cryptosporidiosis.
What are common opportunistic infections at CD4 <100?
Toxoplasmosis, Cryptococcal meningitis, Chronic diarrhea due to Cryptosporidium.
What are common opportunistic infections at CD4 <50?
CMV retinitis, Mycobacterium avium complex (MAC) infection.
What is the gold standard test for HIV diagnosis?
Western Blot (historical) and HIV RNA PCR; however, 4th Generation HIV Ag/Ab Test is now the standard confirmatory test.
What is the first-line screening test for HIV?
4th Generation HIV Ag/Ab Combo Test (Detects p24 antigen and HIV antibodies).
Which test detects HIV in the earliest stage?
HIV RNA PCR (NAT – Nucleic Acid Test), detects HIV within 1-2 weeks post-exposure.
What is the AIDS-defining CD4 count and key illnesses?
AIDS is defined as CD4 <200 or an AIDS-defining illness such as PCP, CNS lymphoma, Cryptococcus, CMV, or Kaposi Sarcoma.
What is the first-line ART regimen recommended by WHO?
First-line regimen: Tenofovir + Lamivudine (or Emtricitabine) + Dolutegravir (TLD regimen).
When should ART be initiated in an HIV patient?
ART should be initiated immediately in all HIV patients, regardless of CD4 count.
What is the goal of ART in terms of viral load?
Undetectable viral load (<50 copies/mL); U=U (Undetectable = Untransmittable).
What is the post-exposure prophylaxis (PEP) regimen for HIV?
PEP should be started within 72 hours of exposure and consists of Tenofovir + Lamivudine + Dolutegravir for 28 days.
What is the pre-exposure prophylaxis (PrEP) regimen for HIV?
PrEP is used for high-risk individuals (MSM, discordant partners) and consists of daily Tenofovir + Emtricitabine (Truvada).
What are the key side effects of Tenofovir?
Tenofovir can cause nephrotoxicity (Fanconi syndrome) and decreased bone mineral density.
What are the key side effects of Efavirenz?
Efavirenz is associated with neuropsychiatric effects (vivid dreams, depression, dizziness).
What are the key side effects of Protease inhibitors (PIs)?
Protease inhibitors (PIs) can cause hyperlipidemia, insulin resistance, and lipodystrophy.
What is immune reconstitution inflammatory syndrome (IRIS)?
IRIS is a paradoxical worsening of infections after starting ART, due to immune recovery.
How is HIV-related tuberculosis managed?
HIV increases TB risk; Start ART after 2 weeks of TB treatment if CD4 <50, otherwise after 8 weeks.
What is the etiologic agent of Salmonella infections?
Salmonella enterica, a Gram-negative facultative anaerobic bacillus.
What are the two major types of Salmonella infections?
Typhoidal Salmonella (S. Typhi, S. Paratyphi) causing enteric fever, and Nontyphoidal Salmonella (NTS) (S. enteritidis, S. typhimurium) causing gastroenteritis and bacteremia.
How is Salmonella transmitted?
Fecal-oral route via contaminated food, water, and person-to-person contact.
What is the pathophysiology of Salmonella infection?
Invades intestinal M cells, enters macrophages, spreads through the bloodstream, causing systemic illness.
What are the key clinical features of typhoid fever?
Stepwise fever progression, relative bradycardia, rose spots, hepatosplenomegaly, constipation > diarrhea.
What are the key clinical features of nontyphoidal Salmonella infection?
Nausea, vomiting, non-bloody diarrhea, usually self-limited but can cause bacteremia in immunocompromised patients.
What are the complications of typhoid fever?
Intestinal perforation, encephalopathy, myocarditis, chronic carrier state.
What are the complications of nontyphoidal Salmonella?
Sepsis, osteomyelitis (especially in sickle cell disease), endovascular infections.
What is the gold standard for diagnosing typhoid fever?
Blood culture (gold standard, ~60% sensitivity).
Which diagnostic test has the highest sensitivity for typhoid fever?
Bone marrow culture (>80% sensitivity, remains positive despite prior antibiotics).
What is the role of culture of intestinal secretions in Salmonella diagnosis?
Culture of intestinal secretions (via duodenal string test) may be positive even when blood and bone marrow cultures are negative.
What are the first-line treatments for typhoid fever?
Fluoroquinolones (Ciprofloxacin or Levofloxacin) for 7-14 days, Azithromycin (for fluoroquinolone-resistant strains), Ceftriaxone IV (severe cases).
When should antibiotics be used for nontyphoidal Salmonella infection?
Only for severe cases or in immunocompromised patients (Fluoroquinolones or Ceftriaxone).
How can Salmonella infections be prevented?
Hand hygiene, proper food handling, improved sanitation, typhoid vaccination for at-risk individuals.
What are special considerations for treating Salmonella in pregnancy?
Avoid fluoroquinolones; Ceftriaxone is preferred during pregnancy.
Name the four species of Plasmodium that cause human malaria.
- P. falciparum – most severe, cerebral malaria
- P. vivax – relapses, tertian fever
- P. ovale – relapses, tertian fever
-
P. malariae – quartan fever, chronic infection
(+ P. knowlesi – zoonotic, severe, daily fever)
How is malaria transmitted?
- Bite of an infected female Anopheles mosquito
- Blood transfusion
- Congenital transmission
- Needle sharing
What is the key pathogenic mechanism of P. falciparum malaria?
- Cytoadherence and sequestration of infected RBCs
- Leads to microvascular obstruction → severe malaria (cerebral malaria, multi-organ failure)
What are the hallmark symptoms of malaria?
- Fever, chills, sweats (paroxysmal)
- Headache, myalgia
- Anemia, jaundice
- Hepatosplenomegaly
Severe Malaria Signs (P. falciparum):
- Cerebral malaria (seizures, coma)
- Severe anemia
- ARDS, pulmonary edema
- Acute kidney injury
- Shock, metabolic acidosis
Match the Plasmodium species with their fever pattern.
- P. falciparum → Irregular fever (malignant tertian)
- P. vivax/ovale → Tertian fever (every 48 hours)
- P. malariae → Quartan fever (every 72 hours)
- P. knowlesi → Daily fevers (24-hour cycle)
What are the gold standard and rapid tests for malaria?
-
Gold Standard: Thick and thin blood smear (Giemsa stain)
- Thick: Detects parasites
- Thin: Identifies species
- Rapid Diagnostic Tests (RDTs): Detects Plasmodium antigens (HRP2, pLDH)
- PCR (Polymerase Chain Reaction): High sensitivity but not routinely used
- Serology: Not useful for acute infection
What is the treatment for uncomplicated malaria?
-
P. falciparum (chloroquine-resistant):
- Artemisinin-based combination therapy (ACT) (e.g., artemether-lumefantrine)
-
P. falciparum (chloroquine-sensitive):
- Chloroquine
-
P. vivax/ovale:
- Chloroquine + Primaquine (to eradicate hypnozoites)
-
P. malariae/P. knowlesi:
- Chloroquine
🔴 Check for G6PD deficiency before giving Primaquine!
What is the treatment for severe malaria?
- IV Artesunate (preferred)
- IV Quinine (if artesunate unavailable)
- Supportive care: Fluids, glucose, transfusion, seizure control
💡 Switch to oral ACT when stable.
What are the chemoprophylaxis options for malaria?
- Chloroquine-sensitive areas: Chloroquine
-
Chloroquine-resistant areas:
- Mefloquine (neuropsych SEs)
- Doxycycline (not for pregnancy, photosensitivity)
- Atovaquone-proguanil (short half-life)
How do you prevent relapses in P. vivax and P. ovale?
- Primaquine (eradicates liver hypnozoites)
- Test for G6PD deficiency first!
What is the most common cause of native valve infective endocarditis (IE)?
Staphylococcus aureus (acute) and Viridans streptococci (subacute).
What is the most common cause of prosthetic valve endocarditis (PVE) within the first 2 months post-surgery?
Staphylococcus epidermidis (coagulase-negative Staphylococcus).
What is the most common organism in IV drug users with infective endocarditis?
Staphylococcus aureus, often affecting the tricuspid valve.
Which valve is most commonly affected in infective endocarditis?
Mitral valve (except in IV drug users, where the tricuspid valve is most commonly affected).
What are the major Duke criteria for diagnosing infective endocarditis?
- Positive blood cultures for typical organisms, 2. Evidence of endocardial involvement (vegetation on echocardiography, new valvular regurgitation).
What are the minor Duke criteria for infective endocarditis?
- Predisposing condition (e.g., prosthetic valve, IV drug use), 2. Fever ≥38°C, 3. Vascular phenomena (e.g., Janeway lesions, emboli), 4. Immunologic phenomena (e.g., Roth spots, Osler nodes), 5. Positive blood culture not meeting major criteria.
What is required to establish a definite diagnosis of infective endocarditis using Duke criteria?
2 major criteria, or 1 major + 3 minor, or 5 minor criteria.
What are Janeway lesions?
Painless, erythematous macules on the palms and soles caused by septic emboli.
What are Osler nodes?
Painful, tender nodules on the fingers and toes due to immune complex deposition.
What are Roth spots?
Retinal hemorrhages with a pale center, seen in infective endocarditis.
What is the most sensitive imaging modality for detecting infective endocarditis?
Transesophageal echocardiography (TEE).
What is the initial empiric antibiotic treatment for native valve infective endocarditis?
Vancomycin + Ceftriaxone or Vancomycin + Gentamicin (to cover MRSA, Strep, and Enterococcus).
What is the initial treatment for prosthetic valve endocarditis?
Vancomycin + Gentamicin + Rifampin (covers MRSA and biofilm-forming organisms).
When is surgery indicated in infective endocarditis?
- Heart failure due to valve dysfunction, 2. Uncontrolled infection despite antibiotics, 3. Large vegetations (>10 mm) with embolic risk, 4. Prosthetic valve involvement.
What is the most common complication of infective endocarditis?
Heart failure due to valvular destruction.
What are the most common embolic complications of infective endocarditis?
Stroke, renal infarcts, splenic infarcts, and septic pulmonary emboli (especially in right-sided endocarditis).
Which patients require prophylactic antibiotics for infective endocarditis?
Patients with prosthetic heart valves, prior IE, congenital heart disease, or cardiac transplant recipients undergoing dental procedures.
What is the recommended prophylactic antibiotic regimen for high-risk patients before dental procedures?
Amoxicillin 2g PO 30-60 minutes before procedure (Clindamycin or Azithromycin if allergic).
What is the most common cause of culture-negative infective endocarditis?
HACEK organisms (Haemophilus, Aggregatibacter, Cardiobacterium, Eikenella, Kingella) and prior antibiotic use.
What is the pathophysiology of infective endocarditis?
Bacteria adhere to damaged endocardium, form vegetations with platelets and fibrin, leading to persistent bacteremia and embolization.
What is the causative agent of COVID-19?
SARS-CoV-2 (a novel coronavirus, from the Coronaviridae family).
What is the primary mode of transmission?
Respiratory droplets and aerosols.
What is the incubation period of COVID-19?
2-14 days (average: 5 days).
Which populations are at highest risk for severe COVID-19?
Elderly (≥60 y/o), immunocompromised, pregnant women, patients with comorbidities (DM, CKD, COPD, CVD).
What are the 4 clinical categories of COVID-19?
- Mild, 2. Moderate, 3. Severe, 4. Critical.
What defines mild COVID-19?
Symptoms (fever, cough, anosmia, sore throat) WITHOUT pneumonia or hypoxia.
What defines moderate COVID-19?
Pneumonia WITHOUT hypoxia (SpO₂ ≥94%).
What defines severe COVID-19?
Pneumonia WITH hypoxia (SpO₂ <94%, RR ≥30, or PaO₂/FiO₂ <300).
What defines critical COVID-19?
ARDS, respiratory failure, septic shock, or multi-organ dysfunction (MODS).
What is the gold standard test for COVID-19 diagnosis?
RT-PCR (Nasopharyngeal swab).
When is rapid antigen testing (RAT) useful?
Best used within the first 5-7 days of symptoms in symptomatic cases.
What is the characteristic finding on chest CT in severe COVID-19?
Bilateral ground-glass opacities (GGO) and crazy paving pattern.
What chest X-ray findings are seen in severe COVID-19?
Bilateral interstitial infiltrates, patchy opacities.
What is the first-line treatment for mild COVID-19?
Supportive care: hydration, antipyretics, NO antibiotics or antivirals.
Which antiviral is recommended for high-risk outpatients with mild COVID-19?
Paxlovid (Nirmatrelvir-Ritonavir) within 5 days of symptom onset.
What is the treatment for moderate COVID-19 requiring hospitalization?
Oxygen therapy (SpO₂ >94%) + Remdesivir in high-risk cases.
What is the first-line steroid for severe COVID-19?
Dexamethasone 6 mg/day for 10 days.
Which immunomodulator is recommended for severe COVID-19?
Tocilizumab (IL-6 inhibitor) for rapid progression cases.
When is mechanical ventilation indicated in COVID-19?
For refractory hypoxemia (ARDS) despite oxygen support.
What are the four main types of COVID-19 vaccines?
- mRNA vaccines, 2. Viral vector vaccines, 3. Inactivated virus vaccines, 4. Protein subunit vaccines.
What are the mRNA vaccines for COVID-19?
Pfizer-BioNTech (Comirnaty) and Moderna (Spikevax).
What are the viral vector vaccines for COVID-19?
AstraZeneca (Vaxzevria), Janssen (J&J), Sputnik V.
What are the inactivated virus vaccines for COVID-19?
Sinovac (CoronaVac), Sinopharm (BBIBP-CorV).
What is the protein subunit vaccine for COVID-19?
Novavax (Nuvaxovid).
Which COVID-19 vaccine has the highest efficacy?
mRNA vaccines (Pfizer & Moderna) ~95% against severe disease.
Which COVID-19 vaccine is single-dose?
Janssen (J&J).
Which COVID-19 vaccines require storage at ultra-low temperatures?
Pfizer (-80°C to -20°C) and Moderna (-20°C).
What are the key preventive measures for COVID-19?
Face masks, hand hygiene, ventilation, vaccination, avoiding crowded places.
Who should receive a COVID-19 booster dose?
Elderly (≥60 y/o), immunocompromised, healthcare workers, pregnant women.
Can COVID-19 vaccines be mixed for booster doses?
Yes, heterologous boosting is recommended.
