Microbiology – Study of microorganisms.
Virus → Virology Bacteria → Bacteriology Fungi → Mycology Parasites → Parasitology Virology (Study of Viruses) General Rules DNA Viruses All are dsDNA , except Parvovirus → ssDNA All are linear , except:Papillomavirus → spiral/projection shape Hepadnavirus (HBV) → circular Envelope : Herpes virus acquires a nuclear membrane, and others from the cell membrane RNA Viruses All are ssRNA , except Reovirus → dsRNA 1. DNA Viruses Virus Family Genome Shape Envelope Herpes virus dsDNA Linear Enveloped (from nuclear membrane) Parvovirus ssDNA Linear Non-enveloped Papillomavirus dsDNA Circular / Spiral-like projection Non-enveloped Hepadnavirus (HBV) dsDNA (partially ds) Circular Enveloped Others (Adeno, Pox, etc.) dsDNA Linear Variable
2. Herpesviridae Family (HSV–HHV Subtypes) Subtype Name Transmission Clinical Features Latency Site HSV-1 Herpes simplex virus type 1 Respiratory route, Saliva – Gingivostomatitis – Conjunctivitis – Meningitis Trigeminal ganglia HSV-2 Herpes simplex virus type 2 Sexual intercourse Vaginal delivery (→ need C-section) – Painful genital ulcers Sacral ganglia HSV-3 Varicella-zoster virus (VZV) Respiratory route – Chickenpox (rash, cough, vesicles) – Reactivation → Shingles – CN V1 involvement → Herpes zoster ophthalmicus Dorsal root ganglia HSV-4 Epstein–Barr virus (EBV) Respiratory route, Saliva – Infectious mononucleosis (pharyngitis → splenomegaly → fever) – Burkitt’s lymphoma (t(8:14)) – Nasopharyngeal carcinoma B lymphocytes HSV-5 Cytomegalovirus (CMV) Saliva, Placenta, Sexual intercourse, Transplant – Retinitis in HIV patients – Opportunistic infection in transplant pts – Owl’s eye inclusions Latent in monocytes/macrophages HSV-6/7 (not in your notes, optional) Saliva Roseola infantum (exanthem subitum, fever + rash in infants) T-cells HSV-8 Kaposi’s sarcoma virus Sexual route (esp. in HIV pts) – Cancer of endothelial cells → Kaposi sarcoma (AIDS defining) B-cells & endothelial cells
3. Genital Ulcers Type Cause Features Notes / Diagnosis Painless ulcer Syphilis – Single, indurated ulcer (chancre ) – Painless – Clean base Test: Dark-field microscopy (gold standard )Painful ulcer (shallow) HSV-2 (Herpes genitalis )– Multiple small ulcers/vesicles – Painful, burning – Often recurrent Test: Tzanck smear (multinucleated giant cells), PCR Painful ulcer (deep) Chancroid – Soft, ragged edges – Painful ulcer – Tender suppurative inguinal lymphadenitis (“bubo”) Test: Gram stain (“school of fish” pattern), culture
Virus Genome Shape Diseases / Associations Parvovirus ssDNA Linear – Aplastic crisis in Thalassemia, Sickle cell disease, Hereditary spherocytosis Papillomavirus (HPV) dsDNA Spiral – HPV 6, 11 → Warts / Verrucae – HPV 16, 18 → Cervical cancer Adenovirus dsDNA Linear – Sore throat – Acute hemorrhagic cystitis (bladder bleed) – Pneumonia – Myocarditis – Conjunctivitis
4. Acute Hemorrhagic Cystitis (AHC): Viral cause → Adenovirus Drug-induced cause → Cyclophosphamide (toxic metabolite: acrolein )Antidote / Prevention → Mesna (binds acrolein, protects bladder)5. RNA Viruses Reoviridae Non-enveloped , dsRNA , linear Example: Rotavirus → diarrhea in children (can be fatal) Picornaviridae (PERCH) – non-enveloped, ssRNA, linearP → Polio virus (vaccine available)E → EchovirusR → Rhinovirus → common coldC → Coxsackie virus → myocarditisH → HAV → acute hepatitisHepevirus HEV → acute hepatitis, lethal in pregnancy Flaviviridae Hepatitis C virus → cirrhosis → liver CADengue virus → hemorrhagic fever(Also included under flavivirus in your notes) Togaviridae Rubella Adult → post-auricular lymphadenopathy, fever, rash Congenital → cataract, hearing loss, PDA Retrovirus HIV → CD4 destruction → AIDSParamyxoviridae Measles Mumps Respiratory syncytial virus (RSV) → bronchiolitis in < 2 yrParainfluenza → Croup Rhabdoviridae Rabies virus Bullet-shaped 100% mortality Autopsy → Negri bodies Deltavirus Hepatitis D virus → defective virus (needs HBV)Orthomyxoviridae (Influenza virus) Antigenic shift → major, abrupt mutation → pandemic Antigenic drift → minor, gradual mutation → epidemic Treatment → Oseltamivir (neuraminidase inhibitor)DNA Viruses (selected from your notes) Herpes viruses HSV-1 → DOC: Acyclovir EBV CMV → DOC: Ganciclovir HHV-8 → Kaposi sarcoma Other points HAV → Councilman bodies (acute hepatitis)HAV in pregnancy → commonHEV in pregnancy → lethal, commonHBsAg → antigenAnti-HBs → antibodyHBeAg → envelope antigenAnti-HBe → antibodyIgM → acute responseIgG → chronicOther Key Associations Dengue → bleedingChikungunya → joint painPseudomonas → green pusActinomyces israelii → sulfur granules in pus (after IUD)Serratia marcescens → red pigmentHere are other materials for NLE NRE step 1
6. Gram-negative vs Gram-positive Bacteria Feature Gram-negative (-ve) Gram-positive (+ve) Cell wall Thin peptidoglycanThick peptidoglycanLPS Present (+), contains Lipid A Absent (–) Toxin type Endotoxin (Lipid A of LPS)Exotoxin (protein)Antigen release Antigen is secreted out directly No toxoid vaccine (endotoxin is unstable for vaccine use)Vaccine No toxoid vaccine (endotoxin unstable for vaccine use)Toxoid vaccine possible Heat stability Stable at 100 °C Destroyed at 60 °C
7. Gram-Positive Bacteria Organism Key Feature / Disease Notes / Treatment Staphylococcus epidermidis Prosthetic valve infection Streptococcus viridans Dental infection Staphylococcus aureus Skin infections, IV drug users → most common valve = Tricuspid Streptococcus bovis (gallolyticus) Colon cancer association Bacillus cereus Food poisoning from reheated rice Toxin = Cereulide , onset 2–5 hr , Tx = supportive Clostridium tetani Releases tetanospasmin , blocks GABA release in the spinal cord → spastic paralysis. Clostridium botulinum Blocks Ach release → diplopia, dysarthria, dyspnea, dysphagia → flaccid paralysis Clostridium difficile Pseudomembranous colitis (esp. after Clindamycin ) Tx: 1. Metronidazole 2. Vancomycin (SE: Red man syndrome)
8. Gram-Negative Bacteria Organism Key Feature / Disease Notes / Treatment E. coli Diarrhea; DM patient → foot ulcer Pasteurella multocida (dog bite)DM + otitis media after bite Tx: Co-amoxiclav Bartonella henselae Cat scratch disease Bacillus anthracis (actually Gram+ + but you wrote here in the sheet contact)Respiratory anthrax (wool/sheet contact) → pulmonary diseaseTx: Ciprofloxacin Cutaneous anthrax → black eschar
9. Spirochetes Organism Key Feature / Disease Notes / Treatment Borrelia burgdorferi (Lyme disease)Facial nerve palsy (Bell’s), arthritis, heart block, erythema migrans (target rash) Tx: Doxycycline Leptospira interrogans Animal pee in river Weil disease = bleeding + jaundice + nonspecific symptoms Treponema pallidum Syphilis (you wrote “palledra” = corrected spelling pallidum )
Check your NRE Step 1 result after completing the exam .
