Microbiology Study Guide: Infectious Diseases of Organ Systems (Chapters 16-21)

Overview of Infectious Diseases by Organ System

Introduction

This study guide summarizes key infectious diseases affecting major human organ systems, as covered in Chapters 16-21 of a typical college-level Microbiology course. It includes the causative agents (pathogens), their classification (virus, bacteria, protozoa, fungi, helminths), symptoms, transmission, diagnosis, and prevention strategies.

Respiratory System Infections (Chapter 16)

Major Diseases and Causative Agents

• Diphtheria: Corynebacterium diphtheriae (bacterium)

• Pertussis (Whooping Cough): Bordetella pertussis (bacterium)

• Tuberculosis: Mycobacterium tuberculosis (bacterium)

• Pneumonia: Multiple agents, including Streptococcus pneumoniae, Mycoplasma pneumoniae, viruses, and fungi

• Common Cold: Rhinoviruses, Coronaviruses (viruses)

• Influenza: Influenza viruses A, B, and C

• SARS: Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

• Hantavirus Pulmonary Syndrome: Hantaviruses

• Diseases by Staphylococcus aureus and Streptococcus pyogenes: Can cause pneumonia and other respiratory infections

• Mycoses: Fungal infections such as histoplasmosis (Histoplasma capsulatum)

Symptoms and Transmission

• Tuberculosis: Chronic cough, hemoptysis, weight loss, night sweats

• Pneumonia: Cough, fever, chest pain, difficulty breathing

• Influenza: Fever, chills, muscle aches, cough, fatigue

• Transmission: Primarily via respiratory droplets; some (e.g., hantavirus) via inhalation of contaminated dust

Skin and Eye Infections (Chapter 17)

Major Diseases and Causative Agents

• Impetigo: Staphylococcus aureus, Streptococcus pyogenes

• Gas Gangrene: Clostridium perfringens

• Cutaneous Anthrax: Bacillus anthracis

• Measles & Rubella: Measles virus, Rubella virus

• Smallpox/Chickenpox: Variola virus (smallpox), Varicella-zoster virus (chickenpox)

• HSV-1: Herpes simplex virus type 1 (oral herpes)

• Acne: Cutibacterium acnes

• Diseases by S. aureus, S. pyogenes, Pseudomonas species: Folliculitis, cellulitis, wound infections

• Cutaneous Mycoses: Dermatophytes (e.g., Trichophyton species)

Symptoms and Transmission

• Impetigo: Honey-colored crusted lesions, highly contagious

• Gas Gangrene: Rapid tissue death, foul odor, gas production

• Transmission: Direct contact, fomites, or via wounds

Nervous System Infections (Chapter 18)

Major Diseases and Causative Agents

• Tetanus: Clostridium tetani

• Botulism: Clostridium botulinum

• Rabies: Rabies virus

• Polio: Poliovirus

• Meningitis: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, viruses, fungi

• Cryptococcosis: Cryptococcus neoformans (fungus)

• African Sleeping Sickness: Trypanosoma brucei (protozoan)

• Toxoplasmosis: Toxoplasma gondii (protozoan)

• Prion Diseases: Abnormal prion proteins (e.g., Creutzfeldt-Jakob disease)

Symptoms and Transmission

• Meningitis: Headache, neck stiffness, fever, photophobia

• Botulism: Flaccid paralysis, difficulty swallowing, respiratory failure

• Transmission: Varies—e.g., tetanus via wounds, rabies via animal bites, polio via fecal-oral route

Digestive System Infections (Chapter 19)

Major Diseases and Causative Agents

• Mumps: Mumps virus

• Hepatitis: Hepatitis viruses (A, B, C, D, E)

• Stomach Ulcer: Helicobacter pylori

• Diarrhea and Dysentery: Escherichia coli, Shigella, Salmonella, viruses, protozoa

• Cholera: Vibrio cholerae

• Clostridium difficile Infection: Antibiotic-associated diarrhea

• Amoebiasis: Entamoeba histolytica

• Cryptosporidiosis: Cryptosporidium species

• Giardiasis: Giardia lamblia

• Schistosomiasis: Schistosoma species (helminth)

• Tapeworm and Pinworm: Taenia species, Enterobius vermicularis

Symptoms and Transmission

• Peptic Ulcer: Abdominal pain, nausea, vomiting

• Cholera: Profuse watery diarrhea ("rice water stools"), dehydration

• Transmission: Fecal-oral route, contaminated food/water

Urinary and Reproductive System Infections (Chapter 20)

Major Diseases and Causative Agents

• Genital Warts: Human papillomavirus (HPV)

• Genital Herpes: Herpes simplex virus types 1 & 2 (HSV-1, HSV-2)

• Vaginosis: Gardnerella vaginalis and others

• Chlamydia: Chlamydia trachomatis

• Syphilis: Treponema pallidum

• Gonorrhea: Neisseria gonorrhoeae

• Candidiasis/Vaginitis: Candida albicans (fungus)

Symptoms and Transmission

• Chlamydia, Gonorrhea, Syphilis: Often asymptomatic, but can cause discharge, pain, infertility

• Candidiasis: Itching, discharge, irritation

• Transmission: Sexual contact, perinatal (mother to child), contaminated surfaces (rare)

Cardiovascular and Lymphatic Infections (Chapter 21)

Major Diseases and Causative Agents

• Dengue/Yellow Fever: Flaviviruses (Dengue virus, Yellow fever virus)

• Chikungunya/Zika: Chikungunya virus, Zika virus

• Ebola, Marburg, Lassa Hemorrhagic Fevers: Filoviruses (Ebola, Marburg), Arenavirus (Lassa)

• Mononucleosis: Epstein-Barr virus (EBV)

• AIDS/HIV: Human immunodeficiency virus (HIV)

• Lyme Disease: Borrelia burgdorferi

• Malaria: Plasmodium species (protozoan)

Symptoms and Transmission

• Lyme Disease: Bull's-eye rash, fever, joint pain

• Malaria: Cyclical fever, chills, anemia

• Transmission: Vector-borne (mosquitoes, ticks), blood, sexual contact (HIV)

Classification of Diseases by Pathogen Type

Table: Major Diseases by Pathogen Type and Organ System

Pathogen Type	Example Diseases	Organ System
Virus	Influenza, HIV/AIDS, Measles, Rabies, Polio, Hepatitis, HPV	Respiratory, Nervous, Digestive, Reproductive, Cardiovascular
Bacteria	Tuberculosis, Diphtheria, Syphilis, Gonorrhea, Anthrax, Lyme Disease	Respiratory, Skin, Nervous, Reproductive, Cardiovascular
Protozoa	Malaria, Giardiasis, Toxoplasmosis, African Sleeping Sickness	Digestive, Nervous, Cardiovascular
Fungi	Candidiasis, Histoplasmosis, Cryptococcosis, Dermatophytosis	Skin, Respiratory, Nervous, Reproductive
Helminths	Schistosomiasis, Tapeworm, Pinworm	Digestive, Cardiovascular

Key Concepts and Additional Information

Virulence Factors

• Staphylococcus aureus: Produces coagulase (clots plasma), hyaluronidase (spreads infection), toxins

• Streptococcus pyogenes: Produces streptolysins, hyaluronidase, and other enzymes

• Enzyme Functions:

  • Hyaluronidase: Breaks down hyaluronic acid in connective tissue, aiding spread

  • Coagulase: Clots blood plasma, protecting bacteria from immune response

  • Cellulase: Breaks down cellulose (mainly in plant pathogens)

Transmission Methods

• Pinworms: Fecal-oral, contaminated surfaces

• Pneumonia: Respiratory droplets

• Toxoplasmosis: Ingestion of oocysts from cat feces or undercooked meat

• Tetanus: Entry of spores via wounds

• Botulism: Ingestion of preformed toxin in food

• Hepatitis C: Bloodborne, sexual contact

Reservoirs and Vectors

• SARS: Bats, civet cats

• Sleeping Sickness: Tsetse fly (vector), wild animals (reservoir)

• Malaria: Anopheles mosquito (vector), humans (reservoir)

• Histoplasmosis: Soil enriched with bird or bat droppings

Vaccines

• Rabies: Inactivated virus vaccine

• HIV: No effective vaccine yet

• Tetanus: Toxoid vaccine

• Measles: Live attenuated vaccine (MMR)

• Diphtheria: Toxoid vaccine (DTaP)

• Pertussis: Acellular vaccine (DTaP)

• HPV: Recombinant subunit vaccine

Diagnostic Tests

• Cervical Cancer: Pap smear, HPV DNA test

• Tuberculosis: Tuberculin skin test (Mantoux), chest X-ray, sputum culture

• HIV: ELISA, Western blot, PCR

• Salmonellosis: Stool culture

Hospital-Acquired (Nosocomial) Infections

• Common Agents: Staphylococcus aureus (including MRSA), Clostridium difficile, Pseudomonas aeruginosa

• Prevention: Hand hygiene, sterilization, isolation protocols, antibiotic stewardship

Stages of Selected Diseases

• Pertussis: Catarrhal stage (mild), paroxysmal stage (severe cough), convalescent stage (recovery)

• HIV: Acute infection, clinical latency, AIDS

• Syphilis: Primary (chancre), secondary (rash), latent, tertiary (gummas, neurological symptoms)

Cellular Targets

• HIV: CD4+ T lymphocytes

• Plasmodium falciparum: Red blood cells (erythrocytes), liver cells

Prevalent Intestinal Protozoa

• USA: Giardia lamblia (giardiasis)

• Worldwide: Entamoeba histolytica (amoebiasis)

Food, Sex/Contact, Blood, and Airborne Transmission

• Foodborne: Salmonellosis, Botulism, Hepatitis A

• Sexually Transmitted: HIV, Syphilis, Gonorrhea, Chlamydia, HPV

• Bloodborne: HIV, Hepatitis B and C, Ebola

• Airborne: Tuberculosis, Measles, Influenza

Additional info:

• Some details (e.g., page numbers, specific textbook references) are omitted for generalization.

• For each disease, students should be able to identify the pathogen, organ system affected, symptoms, transmission, diagnosis, and prevention.