MCB 2010 Final Exam Review: Infectious Diseases of Organ Systems

Respiratory System Infections

Overview of Respiratory Tract Infections

The respiratory tract is a primary entry point for pathogens due to constant exposure to airborne particles. Its susceptibility is increased by factors such as smoking, which impairs mucociliary clearance and weakens immune defenses.

• Portal of Entry: The respiratory tract is the most common route for microbial entry.

• Smoking: Damages cilia, impairs clearance, and increases infection risk.

Major Respiratory Diseases and Clinical Features

• Diphtheria: Thick gray membrane in throat, sore throat, fever.

• Pertussis (Whooping Cough): Severe coughing fits with characteristic "whoop" sound.

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

• Tuberculosis: Chronic cough, weight loss, night sweats, blood-tinged sputum.

Key Respiratory Terms

• Dyspnea: Difficulty breathing.

• Sinusitis: Inflammation of the sinuses.

• Pneumonia: Infection of the lungs.

• Laryngitis: Inflammation of the larynx.

• Pharyngitis: Inflammation of the pharynx.

Common Pathogens and Transmission

• Rhinoviruses: Leading cause of the common cold.

• Influenza A: Most associated with seasonal epidemics.

• Scarlet Fever: Caused by Streptococcus pyogenes.

• Otitis Media: Caused by Streptococcus pneumoniae and Haemophilus influenzae.

• Hemagglutinin (HA): Viral protein for host cell attachment.

• Neuraminidase (NA): Assists in release of new viral particles.

• Tuberculosis: Caused by Mycobacterium tuberculosis, forms granulomas, can remain latent.

• Pneumocystis Pneumonia: Caused by Pneumocystis jirovecii, affects immunocompromised individuals.

• Strep Throat: Caused by Streptococcus pyogenes, symptoms include sore throat, fever, swollen lymph nodes.

• Croup: Viral infection in children, barking cough, stridor.

Diagnosis and Transmission of Respiratory Diseases

• Pneumonia Diagnosis: Chest X-rays, sputum cultures, blood tests, pulse oximetry.

• Transmission:

  • Hantavirus: Inhalation of rodent droppings.

  • SARS: Respiratory droplets.

  • RSV: Direct contact and droplets.

  • Rheumatic Fever: Autoimmune complication of untreated strep throat.

  • Psittacosis: Inhalation of bird droppings infected with Chlamydia psittaci.

Other Respiratory Pathogens

• Legionella pneumophila: Found in freshwater systems.

• Histoplasma capsulatum: Causes histoplasmosis.

• Coxiella burnetii: Causes Q fever.

• Francisella tularensis: Causes tularemia.

• Blastomyces dermatitidis: Causes blastomycosis.

• Aspergillus species: Cause aspergillosis.

Skin and Eye Infections

Overview of Skin and Eye Pathogens

Skin and eye infections are caused by a variety of bacteria, viruses, fungi, and parasites. The skin's normal microbiota provides protection, but breaches can lead to disease.

• Acne: Caused by Cutibacterium acnes.

• Herpesviruses: Cause cold sores, genital herpes, chickenpox, shingles, herpetic whitlow.

• Leishmaniasis: Transmitted by sandfly vector.

• Chickenpox/Shingles: Caused by Varicella-zoster virus, transmitted via droplets or direct contact.

• Keratitis: Caused by Herpes simplex virus, Pseudomonas aeruginosa, or fungi.

• Impetigo: Caused by Staphylococcus aureus and Streptococcus pyogenes.

• Necrotizing Fasciitis: Caused by Streptococcus pyogenes or mixed infections.

• Otitis externa: Often caused by Pseudomonas aeruginosa.

Key Terms and Clinical Features

• Septicemia: Pathogens in blood causing systemic inflammation.

• Folliculitis: Inflammation of hair follicles.

• Furuncle: Painful, pus-filled bump under skin.

• Impetigo: Honey-colored crusted lesions, often around nose/mouth.

• Cold Sores: Treated with antivirals; prevention by avoiding contact during outbreaks.

• Trachoma: Treated with antibiotics, prevented by hygiene.

• Rubella/Measles: Prevented by MMR vaccine.

• Ringworm: Fungal infection caused by Trichophyton, Microsporum, Epidermophyton.

• Neonatal Eye Infections: Caused by Neisseria gonorrhoeae and Chlamydia trachomatis.

• Warts: Caused by Human papillomavirus (HPV).

• Measles: Koplik spots, high fever, cough, conjunctivitis, descending rash.

• Pseudomonas aeruginosa: Opportunistic, affects burns/wounds, produces blue-green pigment.

• Trachoma: Leading cause of infectious blindness.

• Herpetic Whitlow: Caused by Herpes simplex virus.

• Hand, Foot, and Mouth Disease: Caused by Coxsackievirus A16 or Enterovirus 71.

Skin Microbiota and Treatment

• Common Skin Residents:

  • Staphylococcus epidermidis: Gram-positive cocci.

  • Corynebacterium spp.: Gram-positive rods.

  • Malassezia spp.: Yeast.

• MRSA Treatment: Vancomycin, linezolid, daptomycin.

Eye Infections and Other Diseases

• River Blindness: Caused by Onchocerca volvulus (blackflies).

• Fungal Keratitis: Caused by Fusarium or Aspergillus.

• Bacterial Keratitis: Caused by Pseudomonas aeruginosa or Staphylococcus aureus.

• Herpetic Keratitis: Caused by Herpes simplex virus.

Nervous System Infections

Overview of Nervous System Pathogens

The central nervous system (CNS) is normally sterile. Infections can cause severe symptoms and are often life-threatening. Meningitis is a key disease, with bacterial forms being more severe than viral.

• Meningitis: Inflammation of meninges; symptoms include fever, headache, stiff neck, photophobia, nausea, vomiting, altered mental status.

• Bacterial Causes: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, Listeria monocytogenes.

• Pregnancy Risk: Listeria monocytogenes can cross placenta, cause miscarriage/neonatal meningitis.

• Toxoplasma gondii: Transmitted via cat feces, risk for pregnant women.

• CSF Analysis: Bacterial meningitis: high neutrophils, low glucose, high protein.

Transmission Routes and Key Diseases

• Polio: Fecal-oral route.

• Rabies: Bite from infected animal.

• Cryptococcus neoformans: Inhalation of fungal spores.

• Sleeping Sickness: Tsetse fly bite (Trypanosoma brucei).

• West Nile Virus: Mosquito bite.

• Naegleria fowleri: Causes primary amoebic meningoencephalitis from warm freshwater exposure.

Toxins and Other Pathogens

• Clostridium tetani: Causes tetanus (muscle rigidity, spasms).

• Clostridium botulinum: Causes botulism (flaccid paralysis).

• Prion Diseases: Creutzfeldt-Jakob disease, spongiform encephalopathy.

• Zoonotic Diseases: Rabies, West Nile virus, toxoplasmosis, sleeping sickness.

• Trypanosoma brucei: Causes African sleeping sickness.

• Mycobacterium leprae: Causes leprosy, targets peripheral nerves.

• Rabies: Progresses from flu-like symptoms to neurological impairment and hydrophobia.

• Cryptococcus neoformans: Thick capsule evades phagocytosis, crosses blood-brain barrier.

Comparison Table: Bacterial Causes of Meningitis

Pathogen	Gram Stain	Shape
Neisseria meningitidis	Gram-negative	Diplococcus
Streptococcus pneumoniae	Gram-positive	Diplococcus
Haemophilus influenzae	Gram-negative	Coccobacillus
Listeria monocytogenes	Gram-positive	Rod

Digestive System Infections

Anatomy and Pathogens of the GI Tract

The gastrointestinal tract is a complex system susceptible to a variety of infections. Normal microbiota play a crucial role in health, while pathogens can cause disease through toxin production or direct invasion.

• Anatomical Order: Mouth → pharynx → esophagus → stomach → small intestine → large intestine → rectum → anus.

• Dental Cavities: Caused by Streptococcus mutans.

• Toxin-Producing Bacteria: Clostridium difficile, Escherichia coli (EHEC), Vibrio cholerae, Clostridium botulinum.

• Normal Gut Microbiota: Aid in digestion, vitamin production, immune modulation, pathogen resistance.

Transmission and Viral Causes

• Non-fecal-oral Transmission: Helicobacter pylori, Entamoeba histolytica, Trichinella spiralis.

• Viral Gastroenteritis: Norovirus, Rotavirus, Astrovirus, Adenovirus.

• Hepatitis Viruses:

  • HAV & HEV: RNA, fecal-oral.

  • HBV: DNA, blood/sexual.

  • HCV & HDV: RNA, bloodborne.

• Giardia lamblia: Causes giardiasis, greasy foul-smelling diarrhea.

Bacterial and Parasitic Infections

• Gram-positive, Endospore-forming Rods: Clostridium difficile, Clostridium botulinum, Bacillus cereus.

• Tapeworms: Taenia species, proglottid release.

• Salmonellosis: Diarrhea, fever, abdominal cramps; foodborne.

• Peptic Ulcers: Caused by Helicobacter pylori.

• Pseudomembranous Colitis: Clostridium difficile, post-antibiotic.

Other Digestive Diseases and Morphologies

• Mumps: Swollen parotid glands, fever, headache.

• Pinworms: Enterobius vermicularis, perianal itching.

• Hookworms: Necator americanus, anemia, fatigue.

• Ascaris lumbricoides: Large roundworm, intestinal obstruction.

• Cysticercosis: Taenia solium eggs, larval cysts in tissues.

• Campylobacter: Gram-negative curved rod.

• Cryptosporidium: Acid-fast oocysts.

• Escherichia coli: Gram-negative rod.

• Salmonella: Gram-negative rod.

• Trichinella spiralis: Helminth (roundworm).

• Cryptosporidium parvum: Oocysts in contaminated water.

• Taenia saginata: Most common tapeworm infection (beef).

• Schistosoma: Life cycle involves snails, skin penetration by cercariae.

• Trichinellosis: GI symptoms, muscle pain, inflammation.

Oral Health Conditions

• Dental Plaque: Biofilm of bacteria.

• Dental Tartar: Calcified plaque.

• Gingivitis: Gum inflammation.

• Thrush: Oral candidiasis (Candida albicans).

• Periodontal Disease: Inflammation/destruction of supporting tooth structures.

Urinary and Reproductive System Infections

Overview of Urinary and Reproductive Pathogens

Urinary and reproductive system infections are common and can have significant health consequences. Women are more susceptible to UTIs due to anatomical differences.

• UTI Symptoms: Dysuria, urgency, frequency, cloudy/foul-smelling urine.

• Cystitis: Bladder inflammation, similar symptoms to UTI.

• Pyelonephritis: Kidney infection, fever, flank pain, nausea, vomiting.

TORCH Panel and Vaginal Microbiota

• TORCH Panel: Screens for Toxoplasma gondii, Other (syphilis), Rubella, Cytomegalovirus, Herpes simplex virus.

• Bacterial Vaginosis: Clue cells, fishy odor, pH > 4.5.

• Dominant Vaginal Microbiota: Lactobacillus species.

Common Diseases and Pathogens

• Trichomoniasis: Trichomonas vaginalis, frothy greenish discharge.

• Gonorrhea: Neisseria gonorrhoeae.

• HPV: Genital warts, cervical cancer.

• Bacterial Vaginosis: Gardnerella vaginalis.

• Syphilis: Treponema pallidum.

• Genital Herpes: Herpes simplex virus, painful vesicular lesions.

• Yeast Infections: Candida albicans, thick white discharge, itching.

• Chlamydia: Chlamydia trachomatis, often asymptomatic.

• Pelvic Inflammatory Disease: Pelvic pain, fever, abnormal discharge, infertility risk.

• Common UTI Bacteria: Escherichia coli, Staphylococcus saprophyticus, Proteus mirabilis.

• Non-curable STIs: Herpes simplex virus, HIV, HPV.

• Genital Warts: Certain strains of HPV.

• Women and UTIs: Shorter urethra, proximity to anus increases risk.

• Urine Dipstick Test: Detects nitrites, leukocyte esterase, blood, protein.

Cardiovascular and Lymphatic System Infections

Blood Flow and Pathogens

The cardiovascular and lymphatic systems can be affected by a range of pathogens, including bacteria, viruses, and protozoa. Blood flow through the heart follows a specific sequence, and infections can lead to severe systemic effects.

• Blood Flow: Right atrium → right ventricle → pulmonary arteries → lungs → pulmonary veins → left atrium → left ventricle → aorta → body.

• HIV/AIDS: Weakens immune system, increases susceptibility to infections/cancers.

• Zika Virus: Fever, rash, joint pain, conjunctivitis; microcephaly in infants.

• Dengue Virus: High fever, severe headache, muscle/joint pain, hemorrhagic symptoms.

• Yellow Fever Virus: Fever, jaundice, bleeding, organ failure.

• Lyme Disease: Bullseye-shaped rash (Borrelia burgdorferi).

• Septic Shock: Low blood pressure, rapid heart rate, fever/hypothermia, confusion, organ dysfunction.

• Antibiotics and Septic Shock: Can worsen symptoms by causing endotoxin release.

Vector-Borne and Protozoan Diseases

• Tick-borne Diseases: Lyme disease, Rocky Mountain spotted fever, tularemia, ehrlichiosis.

• Mosquito-borne Diseases: Malaria, Zika, Dengue, Yellow fever, West Nile virus.

• Protozoan Diseases: Malaria, toxoplasmosis, leishmaniasis, Chagas disease, African sleeping sickness.

Etiological Agents and Clinical Features

• Lyme Disease: Borrelia burgdorferi.

• Malaria: Plasmodium species.

• Bubonic Plague: Yersinia pestis.

• Rocky Mountain Spotted Fever: Rickettsia rickettsii.

• Burkitt's Lymphoma: Associated with Epstein-Barr virus (EBV), jaw tumor.

• Mononucleosis: EBV, fever, sore throat, swollen lymph nodes, fatigue.

• Bacillus anthracis: Gram-positive, spore-forming rod.

• Bacterial Endocarditis: Staphylococcus aureus, Streptococcus viridans, Enterococcus species.

Comparison Table: Vector-Borne Diseases

Disease	Vector	Pathogen
Lyme Disease	Tick	Borrelia burgdorferi
Rocky Mountain Spotted Fever	Tick	Rickettsia rickettsii
Tularemia	Tick	Francisella tularensis
Ehrlichiosis	Tick	Ehrlichia chaffeensis
Malaria	Mosquito	Plasmodium spp.
Zika Virus	Mosquito	Zika virus
Dengue Virus	Mosquito	Dengue virus
Yellow Fever	Mosquito	Yellow fever virus
West Nile Virus	Mosquito	West Nile virus

Additional info:

• For all diseases, diagnosis and treatment may involve laboratory tests, imaging, and antimicrobial therapy as appropriate.

• Prevention strategies include vaccination, hygiene, vector control, and safe food/water practices.