Microbial Diseases of the Skin, Eyes, Nervous, Cardiovascular, and Lymphatic Systems: Study Guide

Microbial Diseases of the Skin and Eyes

Conditions Favoring Microbial Growth on Skin

• Moisture: Areas such as sweat glands and folds provide a humid environment.

• Nutrients: Sebum and dead skin cells serve as nutrients for microbes.

• Temperature: Skin temperature supports the growth of certain microorganisms.

• pH: The skin's slightly acidic pH (around 5.5) inhibits many pathogens but allows normal flora to thrive.

Microbial Adaptations for Skin Inhabitation

• Salt Tolerance: Ability to survive in salty conditions (e.g., Staphylococcus species).

• Lipid Utilization: Enzymes to break down sebum.

• Resistance to Drying: Formation of spores or thick cell walls.

Definitions of Skin Lesions

• Vesicle: Small, fluid-filled lesion (e.g., in chickenpox).

• Macule: Flat, reddened skin lesion (e.g., in measles).

• Pustule: Raised lesion containing pus (e.g., in impetigo).

Viral Latency Locations

• Varicella-Zoster Virus: Latent in dorsal root ganglia.

• Herpes Simplex Virus 1 (HSV-1): Latent in trigeminal nerve ganglia.

Pathogenic Factors of Group A Streptococci

• M Protein: Inhibits phagocytosis.

• Streptolysins: Lyse host cells.

• Enzymes: Hyaluronidase and streptokinase facilitate tissue invasion and spread.

Major Skin and Eye Diseases: Pathogen, Symptoms, Transmission, and Prevention

Disease	Pathogen	Symptoms	Port of Entry	Transmission	Prevention
Measles	Measles virus	Rash, fever, Koplik spots	Respiratory tract	Airborne droplets	MMR vaccine
Rubella	Rubella virus	Mild rash, fever	Respiratory tract	Airborne droplets	MMR vaccine
Impetigo	Staphylococcus aureus, Streptococcus pyogenes	Pustules, crusting	Skin	Direct contact	Hygiene
Folliculitis	Staphylococcus aureus	Pustules at hair follicles	Hair follicle	Direct contact, fomites	Hygiene
Toxic Shock Syndrome	Staphylococcus aureus	Fever, rash, shock	Skin/mucosa	Tampons, wounds	Proper tampon use
Chickenpox	Varicella-zoster virus	Vesicular rash	Respiratory tract	Airborne droplets	Varicella vaccine
Shingles	Varicella-zoster virus (reactivation)	Localized vesicular rash	Nerves/skin	Reactivation	Shingles vaccine
Herpes Simplex	HSV-1	Cold sores	Oral mucosa	Direct contact	Avoid contact
Necrotizing fasciitis	Streptococcus pyogenes	Rapid tissue destruction	Skin wound	Direct contact	Prompt wound care
Dermatomycoses	Dermatophytes	Ringworm, athlete's foot	Skin	Direct/indirect contact	Keep skin dry
Candidiasis	Candida albicans	White patches, itching	Mucosa/skin	Opportunistic	Antifungals
Conjunctivitis	Bacterial/viral	Redness, discharge	Conjunctiva	Direct contact	Hygiene
Ophthalmia Neonatorum	Neisseria gonorrhoeae	Pus, swelling in newborn eyes	Eyes	Birth canal	Antibiotic eye drops

Microbial Diseases of the Nervous System

Basic Definitions

• Central Nervous System (CNS): Brain and spinal cord.

• Peripheral Nervous System (PNS): Nerves outside the CNS.

• Blood-Brain Barrier: Protective barrier that restricts passage of substances from blood to CNS.

• Meningitis: Inflammation of the meninges (membranes covering CNS).

• Encephalitis: Inflammation of the brain itself.

Major Nervous System Diseases: Pathogen, Symptoms, Transmission, and Prevention

Disease	Pathogen	Symptoms	Transmission	Port of Entry	Prevention
Bacterial Meningitis (Hib)	Haemophilus influenzae type b	Fever, headache, stiff neck	Respiratory droplets	Respiratory tract	Hib vaccine
Meningococcal Meningitis	Neisseria meningitidis	Rash, fever, stiff neck	Respiratory droplets	Respiratory tract	Vaccine
Pneumococcal Meningitis	Streptococcus pneumoniae	Fever, headache, stiff neck	Respiratory droplets	Respiratory tract	Vaccine
Listeriosis	Listeria monocytogenes	Fever, muscle aches	Foodborne	GI tract	Food safety
Cryptococcosis	Cryptococcus neoformans	Headache, fever	Inhalation	Respiratory tract	Avoid bird droppings
Protozoan Meningitis/Encephalitis	Naegleria fowleri, others	Headache, fever, confusion	Waterborne	Nasal mucosa	Avoid warm freshwater
Arboviral Encephalitis	West Nile, Zika viruses	Fever, confusion, seizures	Mosquitoes	Blood	Insect control
Tetanus	Clostridium tetani	Muscle spasms	Wound contamination	Skin	Tetanus vaccine
Botulism	Clostridium botulinum	Flaccid paralysis	Foodborne	GI tract	Proper food handling
Poliomyelitis	Poliovirus	Paralysis	Fecal-oral	GI tract	Polio vaccine
Rabies	Rabies virus	Hydrophobia, agitation	Animal bite	Skin	Vaccination
Creutzfeldt Jakob Disease	Prion	Dementia, motor dysfunction	Unknown/iatrogenic	Brain tissue	Avoid contaminated tissue

Diagnosis and Differentiation of Meningitis

• Diagnosis: Lumbar puncture to obtain cerebrospinal fluid (CSF) for analysis.

• Gram Stain: Differentiates bacterial types:

  • Haemophilus influenzae: Gram-negative rods

  • Neisseria meningitidis: Gram-negative diplococci

  • Streptococcus pneumoniae: Gram-positive diplococci

Mechanisms of Tetanus and Botulinum Toxins

• Tetanus Toxin: Blocks inhibitory neurotransmitter release, causing muscle spasms.

• Botulinum Toxin: Blocks acetylcholine release, causing flaccid paralysis.

Polio Vaccines: Comparison

Vaccine	Advantages	Disadvantages
Oral Polio Vaccine (OPV)	Easy to administer, induces gut immunity	Rare risk of vaccine-derived polio
Inactivated Polio Vaccine (IPV)	No risk of vaccine-derived polio	Requires injection, less gut immunity

Rabies Diagnosis

• Diagnosis: Detection of viral antigens in tissue (e.g., Negri bodies in brain), PCR, or immunofluorescence.

Microbial Diseases of the Cardiovascular and Lymphatic Systems

Relationship Between Cardiovascular and Lymphatic Systems

• Cardiovascular System: Circulates blood, delivering oxygen and nutrients.

• Lymphatic System: Returns interstitial fluid to blood, filters pathogens via lymph nodes.

• Interconnection: Lymph drains into the bloodstream at the subclavian veins.

Definitions

• Septicemia: Growth of pathogens in the blood.

• Sepsis: Systemic inflammatory response to infection.

• Septic Shock: Sepsis with dangerously low blood pressure.

Signs and Symptoms of Septicemia and Sepsis

• Fever, chills, rapid breathing, increased heart rate, confusion, low blood pressure (in shock).

Organisms Responsible for Sepsis

• Escherichia coli

• Staphylococcus aureus

• Streptococcus pyogenes

• Pseudomonas aeruginosa

Transovarian Passage in Rickettsia rickettsii

• Definition: Transmission of pathogen from adult tick to offspring via eggs, ensuring persistence in tick populations.

Lyme Disease: Symptoms and Duration

Phase	Symptoms	Duration
1	Erythema migrans (bull's-eye rash), fever, fatigue	Days to weeks
2	Neurological symptoms, facial palsy, heart problems	Weeks to months
3	Arthritis, chronic neurological complaints	Months to years

Malaria Parasite Life Cycle in Humans

• Liver: Sporozoites infect liver cells and multiply.

• Red Blood Cells: Merozoites infect RBCs, leading to cycles of fever.

Periodic Symptoms of Malaria

• Fever and chills occur as merozoites are released from ruptured RBCs in a synchronized cycle.

Major Cardiovascular and Lymphatic Diseases: Pathogen, Symptoms, Transmission, and Prevention

Disease	Pathogen	Symptoms	Port of Entry	Reservoir	Transmission	Prevention
Endocarditis	Various bacteria	Fever, heart murmur	Bloodstream	Human	Dental procedures, IV drugs	Prophylactic antibiotics
Pericarditis	Various bacteria/viruses	Chest pain, fever	Bloodstream	Human	Spread from infection	Treat underlying infection
Rheumatic Fever	Streptococcus pyogenes	Joint pain, heart inflammation	Respiratory tract	Human	Post-strep infection	Prompt strep treatment
Infectious Mononucleosis	Epstein-Barr virus	Fever, sore throat, lymphadenopathy	Oropharynx	Human	Saliva	Avoid sharing drinks
Toxoplasmosis	Toxoplasma gondii	Flu-like, severe in immunocompromised	Oral	Cats	Ingestion of oocysts	Avoid cat litter
Lyme Disease	Borrelia burgdorferi	See above	Skin (tick bite)	Deer, rodents	Tick bite	Tick avoidance
Rocky Mountain Spotted Fever	Rickettsia rickettsii	Fever, rash	Skin (tick bite)	Ticks	Tick bite	Tick avoidance
Chagas Disease	Trypanosoma cruzi	Fever, swelling, chronic heart/GI disease	Skin/mucosa	Reduviid bugs	Bug feces	Insect control
Malaria	Plasmodium spp.	Fever, chills, anemia	Blood	Humans, mosquitoes	Mosquito bite	Insect control, prophylaxis
Gangrene	Clostridium perfringens	Tissue death, gas production	Wound	Soil	Contaminated wounds	Prompt wound care