micro exam 4

• Antimicrobial peptides


  • + charged chemicals that act by disrupting the - charged membranes of bacteria
  • Responsible for keeping the microbial count on the skin relatively low
• Sebum


  • Low pH makes the skin inhospitable to microorganisms
  • Oily due to its high concentration of lipids. Lipids serve as nutrients for normal microbiota
  • Toxic by-products of fatty acid metabolism inhibit the growth of microorganisms not adapted to the skin environment
• Sweat


  • Inhibitory to microorganisms due to low pH and high salt concentration
• Lysozyme


  • Enzymes found in sweat, tears and saliva. Breaks down peptidoglycan found in the cell walls of bacteria
• Keratinized surface


  • Stratum corneum
  • Outermost layer of the epidermis, made up of 10-30 thin layers of continually shedding, dead keratinocytes
  • Gives the cells their ability to withstand damage, abrasion, and water penetration
• Sloughing


  Process of shedding dead surface cells from the skin carrying bacteria and other pathogens with them
• Maculopapular rash diseases


  Skin eruptions caused by a variety of microbes, flat to slightly raised colored bumps
• Measles


  Rubeola, most contagious, serious airborne disease, lead to severe complications & death
• Symptoms & signs of measles include sore throat, dry cough, headache, conjunctivitis, lymphadenitis, fever, oral lesions (Koplik's spots), and a red, maculopapular exanthem that erupts on the head and progresses to the trunk and extremities. The rash gradually coalesces into red patches that fade to brown.
• Complications of measles


  • Laryngitis
  • Bronchopneumonia
  • Secondary bacterial infections (ear and eye infections)
  • Pneumonia
  • Encephalitis resulting in CNS changes ranging from disorientation to coma (can result in permanent brain damage or epilepsy)
• Subacute sclerosing panencephalitis (SSPE)


  Most serious complication of measles; progressive neurological degeneration of the cerebral cortex, white matter, and brain stem, causes profound intellectual and neurological impairment, spreads unchecked through the brain by cell fusion, destroying neurons and accessory cells and breaking down myelin, involves a defective virus, unable to form a capsid and be released from an infected cell
• Pathogenesis and virulence factors of measles


  1. Virus implants on respiratory mucosa and infects the tracheal and bronchial cells

  2. Travels to the lymphatic system where it multiplies and enters the bloodstream (viremia) which carries the virus to the skin and various organs

  3. Cell membranes of adjacent host cells fuse into large syncytia (giant cells with many nuclei) and no longer perform their proper function
• Causative organism of measles

  Measles virus
• Virulence factors of measles


  • Syncytium formation, ability to suppress CMI
• Transmission and epidemiology of measles


  One of the most contagious infectious diseases, transmitted by droplet contact, a human only reservoir, a person is infectious during the periods of incubation, prodrome phase, and the skin rash, but not during convalescence
• Prevention of measles


  MMR vaccine contains live, attenuated measles virus that confers protection for up to 20 years
• Treatment of measles


  Reducing fever, suppressing cough, replacing lost fluid, remedies to relieve neurological and respiratory symptoms and to sustain nutrient, electrolyte, and fluid levels, vitamin A supplements recommended
• Rubella


  German measles, relatively minor rash disease with few complications, serious damage can occur to the fetus in utero
• Signs and symptoms of postnatal rubella


  • Rash of pink macules and papules, milder than measles rash, appears first on the face and progresses down the trunk and toward the extremities
  • Adult rubella is often characterized by joint inflammation and pain rather than a rash
• Congenital rubella


  Teratogenic: causes harm to fetus, transmitted form the mother to fetus in utero
• Virulence factors of rubella


  • In fetuses: inhibition of mitosis, induction of apoptosis, and damage to vascular endothelium
• Causative agent of rubella


  Rubella virus, Rubivirus form the family Togaviridae, had the ability to stop mitosis, an important process for a developing embryo and fetus, induces apoptosis (programmed cell death) of normal tissue cells, causing irreversible organ harm, damages vascular endothelium leading to poor development of many organs
• Transmission and epidemiology of rubella


  Transmitted by droplet contact, worldwide distribution, initiated through contact with respiratory secretions and occasionally urine, shed through prodromal phase and up to a week after the rash appears, congenitally infected infants are contagious for a much longer time, moderately communicable; close living conditions are required for its spread
• Prevention and treatment of rubella


  Attenuated rubella vaccine is given in MMR at 12-15 months and a booster at 4-6 yrs. Postnatal rubella is usually benign and required only symptomatic treatment, no specific treatment is available for congenital manifestations
• Roseola


  Common disease in young children and babies, "sixth disease"
• Roseola results in maculopapular rash, but up to 70% of cases proceed without the rash stage. Usually accompanied by high fever that comes quickly and lasts up to 3 days; seizures may occur this period. On 4th day the fever disappears and rash appears, first on chest and trunk then less prominently on the face and limbs.
• Virulence factors of roseola


  • Ability to remain latent
• Causative agent of roseola


  Human herpesvirus 6 (HHV-6), can remain latent in the host indefinitely after the disease has cleared, occasionally, reactivates in childhood or adulthood causing mononucleosis-like or hepatitis-like symptoms
• Transmission and epidemiology of roseola


  Thought that 100% of the U.S. population is infected with the virus by adulthood, most common modes of transmission are unknown
• Scarlet fever


  An infection with an S. pyogenes strain that itself is infected with a bacteriophage. This lysogenic virus gives the streptococcus the ability to produce erythrogenic toxin. Sandpaper-like rash, most often on the neck, chest, elbows, and inner surfaces of the thighs. High fever accompanies the rash.
• Streptococcus pyogenes


  Gram + coccus that grows in chains
• "Fifth" disease


  Human parvovirus, also known as erythema infectiosum, ⅕ of the diseases recognized by doctors causing bright red cheek rashes in children
• Signs and symptoms of "fifth" disease include a mild disease that results in a "slapped cheek" appearance that begins on the face, within 2 days rash spreads on the body but is most predominant on arms, legs, and trunk. May recur for several weeks and may be brought on by ant activity that increases body heat.
• Causative agent of "fifth" disease

  Parvovirus B19
• Diagnosis of "fifth" disease


  Clinical presentation, rule out ribella by testing for IgM antibodies
• Transmission and epidemiology of "fifth" disease


  Very contagious, transmitted by droplet contact and direct contact
• Prevention and treatment of "fifth" disease


  No vaccine and no treatment, usually mild disease
• Mumps


  Self-limited, mildly epidemic illness associated with painful swelling at the angle of the jaw. Only humans are known host
• After an average incubation period of 2-3 weeks, mumps causes fever, nasal discharge, muscle pain, and malaise, which may be followed by inflammation of salivary glands, producing gopher-like swelling of the cheeks on one or both sides.
• Parotitis in mumps


  Swelling of the gland and can cause considerable discomfort