micropara 3

• Skin


  • Has normal flora
  • Low pH
  • Has lysozyme and sebum
• Common skin infections


  • Dermatitis
  • Folliculitis
  • Stye
  • Furuncle (boil)
  • Carbuncle
  • Macule
  • Papule
  • Vesicle
  • Pustule
• Viral skin infections


  • Chickenpox and Shingles
  • Rubella (German Measles)
  • Rubeola (Hard Measles)
  • Monkeypox
  • Smallpox
  • Warts
• Varicella (Chickenpox)


  • Caused by Varicella-zoster virus (a herpes virus)
  • Double-stranded DNA virus
  • Enveloped
  • Transmission: Direct contact, droplet, airborne
  • Fever and Skin Rash: Vesicles forming (mucous membrane)
  • Self-limiting, vaccine-preventable
  • Reye's syndrome – severe encephalomyelitis with liver damage
  • Latency – does not leave the body; stays in nerve root ganglia to remain in dormant stage
• Herpes Zoster (Shingles)


  • Reactivation due to IMMUNOSUPPRESSION (common after 50 years old)
  • Common at the TORSO/ABDOMINAL AREA – nerves known as dermatones
• Rubella (German Measles)


  • Rubella Virus
  • RNA virus
  • Transmission: Droplet and direct contact with secretions
  • Fever and flat, pink rashes; starts from the face-neck-trunk-extremities
• Rubeola (Hard Measles)


  • Rubeola
  • Single-stranded RNA virus
  • Enveloped
  • Fever, conjunctivitis, cough, photosensitivity
  • Koplik spots in the mouth and red blotchy skin
  • Transmission: Airborne and direct contact to secretions
• Monkeypox


  • Rare
  • Monkeypox virus
  • Transmission: Animal bite or direct contact with animal secretions and infected person
• Smallpox


  • Variola minor and variola major (20-40% fatal)
  • Double-stranded DNA
  • Systemic infection – fever, malaise, headache, severe backache, sometimes vomiting and abdominal pain
  • Transmission: Droplet
  • Biological warfare and bioterrorism
• Warts


  • Caused by HPV (human papillomaviruses)
  • Non-enveloped DNA virus
  • Have many types: common warts, flat warts, plantar warts, filiform warts
  • Most are cancerous
  • Transmission: direct contact, genital warts are STD's
• Bacterial skin infections


  • Acne
  • Anthrax
  • Gas Gangrene
  • Leprosy
  • Staphylococcal infections
  • Streptococcal infections
• Acne (Pimple)


  • Caused by Propionbacterium acnes and other Propionbacterium spp.
  • Anaerobic
  • Gram-positive bacilli
  • Not transmissible
  • Pimple types: papules, blackheads, whiteheads, nodules, pustules, cysts
• Anthrax (Woolsorter's Disease)


  • Types: Skin – cutaneous anthrax, Lungs – pulmonary anthrax, GIT – GIT anthrax
  • Caused by Bacillus anthracis
  • Gram positive bacilli
  • Encapsulated
  • Spore-forming
  • Transmission: Airborne and Direct contact
  • Fatal for Pulmonary & GIT Anthrax
• Gas Gangrene


  • Caused by Clostridium perfringens
  • Gram-positive bacilli in pair or chain (sometimes variable staining reaction)
  • Spore-forming
  • Can develop capsule
  • Non-motile
  • Obligate anaerobe
  • Vegetative pathogens produce necrotizing exoenzymes and toxins, which destroy muscle and soft tissue, allowing deeper penetration by the organisms
  • Tissue destruction immediate amputations
  • Severe complications: shock and renal failure
  • Reservoir: Soil
  • Transmission: Contact with soil - contaminated spores (to wound)
• Staphylococcal infections


  • Staph aureus – gram (+) cocci in grape-like cluster
  • Endotoxin forming
  • Commonly localized infections; can complicate to pneumonia, lung abscess, osteomyelitis, sepsis, septic arthritis, endocarditis, and toxic shock syndrome
• Common types of Staph. infections


  • Furuncles (Boils)
  • Carbuncles
  • Impetigo
  • Cellulitis
  • Staphylococcal Scalded Skin Syndrome (SSSS)
• Furuncles (Boils)


  Pus-filled bump under the skin, usually of the hair follicle
• Carbuncles


  Cluster of 2 or more sub-cutaneously connected furuncles
• Impetigo


  • Occurs in children; pus-filled blisters/pustules
  • There is impetigo of the newborn or impetigo neonatorum
• Cellulitis


  Non-necrotizing inflammation of the skin and subcutaneous tissues; its hyaluronidase breaks down hyaluronic acid of the connective tissue and can easily spread throughout the body

  
• Staphylococcal Scalded Skin Syndrome (SSSS)


  • The toxins cause the epidermis to separate from the dermis, causing the exfoliation (peeling) of the skin
  • Targets the protein that holds skin
  • Primarily affects the children and infants with immature immune system
• Methicillin-Resistant Staphylococcus Aureus (MRSA)


  • Commonly a nosocomial infection, however, there are community-associated MRSA
  • Cause: Overuse and misuse of antibiotics
  • Methicillin is a beta-lactam antibiotic that acts by inhibiting penicillin-binding proteins (PBP) that are involved in the synthesis of peptidoglycan layer
• Toxic Shock Syndrome (TSS)


  • A rare and fatal disease
  • Caused by Staphylococcus (also, by Streptococcus, and Clostridium)
  • Initial symptoms are fever and rash, but with hypotension, tachycardia, dyspnea, seizures
  • Often associated with tampon use
  • Immune system overreacts because of the response to the release of toxin
• Streptococcal infections


  • Gram (+) cocci in chain and in pair
  • Classification of Strep. According to Lancefield Groups (presence of specific carbohydrate antigen in the cell wall)
  • Classification according to hemolytic pattern on Blood Agar Plate (BAP) medium

  
• Common Streptococcal diseases


  • S. pyogenes – mostly skin infections, scarlet fever, rheumatic fever, strep throat/pharyngitis (Group A, Beta hemolytic)
  • S. agalactiae – commonly colonizes GIT and genitourinary tract to cause sepsis, pneumonia, meningitis (Group B)
• Penicillin-binding proteins (PBP)


  Proteins involved in the synthesis of peptidoglycan layer
• Inhibiting penicillin-binding proteins


  Mechanism of action of penicillin
• Toxic Shock Syndrome (TSS)


  • A rare and fatal disease
  • Caused by Staphylococcus (also, by Streptococcus, and Clostridium)
  • Initial symptoms are fever and rash, but with hypotension, tachycardia, dyspnea, seizures
  • Often associated with tampon use
  • Immune system overreacts because of the response to the release of toxin
• Streptococcal infections


  • Gram (+) cocci in chain and in pair
  • Classification according to Lancefield Groups (presence of specific carbohydrate antigen in the cell wall)
  • Classification according to hemolytic pattern on Blood Agar Plate (BAP) medium
• Common Streptococcal diseases


  • S. pyogenes - mostly skin infections, scarlet fever, rheumatic fever, strep throat/pharyngitis
  • S. agalactiae - commonly colonizes GIT and genitourinary tract to cause sepsis, pneumonia, meningitis to those with weak immune systems (esp. newborns)
  • S. dysgalactiae subsp. equisimilis - pharyngitis, cellulitis, abscesses, respiratory tract infections, rheumatic fever (less common)
  • Strep viridans - NF of the mouth and GIT but can cause opportunistic infections for the immune compromised
  • Strep mutans - dental caries or demineralize the tooth enamel by metabolizing sugar
• Alpha (a) hemolysis


  Incomplete hemolysis of blood around the colonies; light and greenish color around the colonies

  
• Beta (b) hemolysis


  Complete hemolysis around the colonies; transparent around the colonies
• Gamma (y) hemolysis


  No hemolysis of blood around the colonies

  
• Common Streptococcal skin infections


  • Impetigo
  • Scarlet fever
  • Erysipelas/St. Anthony`s fire
  • Necrotizing Fasciitis

  
• Mycobacterium leprae: Leprosy


  • Hansen disease
  • Long incubation period
  • Acid fast bacillus
  • Lepromatous form - many nodules of skin and nasal mucosa and eyes; contagious
  • Tuberculoid form - peripheral nerve involvement and loss of sensation; not contagious

  
• Conjunctivitis (Pink Eye)


  Infection/inflammation of the conjunctiva
• Causes of conjunctivitis


  • Viral: Herpes simplex and Adenovirus
  • Bacterial: Staphylococcus aureus, Streptococcus pneumoniae, Hemophilus influenzae
• Blepharitis


  Infection due to overgrowth of bacteria on the eyelid margin, commonly blockage of the oil glands by Staphylococcus aureus
• Stye (Hordeolum)


  Infection of the oil glands or sweat glands usually at the base of the eyelids; red tender bump with visible pus-filled center, commonly by Staphylococcus aureus
• Causes of keratitis


  • Viral: Herpes simplex, varicella-zoster
  • Bacterial: Staphylococcus aureus, Streptococcus pneumonia, Pseudomonas aeruginosa
  • Fungal: Fusarium, Aspergillus