Principles of Medical Microbiology and OmpathStudy

Trimethoprim-sulfamethoxazole (TMP-SMX) : First-line prophylaxis for both PCP and toxoplasmic encephalitis, especially when CD4 count <200 cells/μL or <100 cells/μL with positive Toxoplasma IgG. Alternative agents : Dapsone, atovaquone, or aerosolized pentamidine may be used in TMP-SMX-intolerant patients. CD4 Monitoring : Regular CD4+ T-cell count assessment to guide initiation and discontinuation of prophylaxis. ART initiation : Early antiretroviral therapy helps restore immunity and prevent opportunistic infections. Adherence counseling : Ensures compliance with prophylactic regimens and ART. Leucovorin (folinic acid) supplementation : To prevent bone marrow suppression from pyrimethamine. Regular hematologic monitoring : Monitor CBC for neutropenia, anemia, and thrombocytopenia. Renal function monitoring : Sulfadiazine can cause crystalluria or renal toxicity. Hydration : Ensure adequate fluid intake to prevent renal complications. Allergy surveillance : Watch for hypersensitivity reactions or rash, especially from sulfonamides. Cutaneous lesions : Ulcerated or nodular skin lesions at the site of sandfly bite, often painless. Regional lymphadenopathy : Enlargement of nearby lymph nodes. Disfiguring scars : Chronic or healing lesions may result in visible scarring. Secondary bacterial infection : May complicate ulcerated lesions. Systemic symptoms (in some cases) : Low-grade fever and malaise, depending on the species and immune status. Bactericidal effect occurs when an antibiotic kills bacteria directly. This is typically seen:At higher drug concentrations. In rapidly dividing bacterial populations. In infections where immune clearance is inadequate (e.g., endocarditis, meningitis, neutropenia). Bacteriostatic effect inhibits bacterial growth and replication without killing, relying on the host immune system to eliminate the organism. Effect depends on the drug, dose, organism, and host immunity. For example, chloramphenicol may be bacteriostatic for some organisms and bactericidal for others. Avoid in immunocompromised patients : These patients may require bactericidal agents due to reduced immune clearance. Avoid combination with bactericidal drugs : Some combinations (e.g., bactericidal + bacteriostatic) can lead to antagonism and reduced efficacy. Pathogenesis :Prions are misfolded proteins (PrP^Sc) that induce conformational changes in normal cellular prion proteins (PrP^C) to the abnormal form. PrP^Sc accumulates in neural tissue, forming amyloid plaques. This accumulation leads to neuronal death, spongiform degeneration, and progressive neurodegeneration. There is no immune response or inflammation due to the host-derived nature of prions. Human prion diseases : Creutzfeldt-Jakob disease (CJD) – the most common prion disease, often sporadic. Variant CJD – associated with consumption of BSE (mad cow disease)-infected beef. A. Life Cycle (Illustration-friendly — include with diagram if submitting) . Click to see Life Cycle Mosquito stage (Definitive host) Female Anopheles mosquito inoculates sporozoites during a blood meal. Human liver stage (Pre-erythrocytic) Sporozoites enter hepatocytes → multiply asexually → form schizonts → release merozoites into bloodstream. Human blood stage (Erythrocytic cycle) Merozoites invade RBCs → mature into trophozoites → form schizonts → rupture RBCs, releasing more merozoites. Some trophozoites form gametocytes (sexual forms). Back to mosquito (sexual cycle) Mosquito ingests gametocytes → gamete fusion → zygote → ookinete → oocyst → sporozoites → cycle continues. Illustration tip : Use a circular flow chart with human and mosquito phases clearly labeled. --- B. Pathogenesis RBC Destruction → Hemolytic anemia, jaundice. Cytoadherence → P. falciparum causes infected RBCs to adhere to endothelium (via PfEMP1) → microvascular obstruction , cerebral malaria , placental malaria . Immune response → Fever, chills, cytokine release. Sequestration → In spleen/liver; can lead to organomegaly and immune evasion. --- C. Treatment Uncomplicated malaria : Artemisinin-based combination therapies (ACTs) : e.g., artemether-lumefantrine, artesunate-amodiaquine. Severe malaria : IV artesunate (preferred), followed by oral ACT. Supportive care :Manage hypoglycemia, anemia, renal failure, cerebral edema. Note: Chloroquine is ineffective due to resistance. --- D. Control and Prevention Vector control : Insecticide-treated nets (ITNs), indoor residual spraying (IRS). Chemoprophylaxis : E.g., atovaquone-proguanil, doxycycline (travelers). Surveillance : Rapid diagnostic tests (RDTs), microscopy. Vaccination : RTS,S/AS01 (Mosquirix) approved for children in endemic regions. Public education : Elimination of breeding sites, early diagnosis. A. Molecular Diagnostics PCR and RT-PCR : High sensitivity/specificity for Plasmodium , Toxoplasma , Leishmania , Trypanosoma . Loop-mediated isothermal amplification (LAMP) : Field-friendly alternative to PCR. B. Immunodiagnostics ELISA : Detection of