Microbiology

• Staphylococcus aureus


  Gram-positive coccus that grows in clusters; nonmotile
• Staphylococcus aureus


  Can be highly virulent, but is also considered "normal" biota of the skin in 1/3 of the population
• Things Staphylococcus aureus can produce

  • hyaluronidase
  • staphylokinase
  • DNase
  • lipase
• Measles


  This virus causes oral lesions called Koplik's spots
• Measles


  Red, maculopapular exanthem that erupts on the head and progresses to the trunk and extremities
• Measles


  Sequelae complications can include Encephalitis resulting in CNS changes ranging from disorientation to coma resulting from brain damage or epilepsy
• Chicken pox


  Rash begins on the scalp, face, and trunk, and radiates in sparse crops to the extremities
• Chicken pox


  Becomes latent in the ganglia and may reemerge as shingles abruptly after reactivation by psychological stress, immunosuppressive therapy, surgery, or developing malignancy
• Smallpox (variola virus)


  This is an extremely serious disease contracted via the respiratory route, however, it causes lesions on the skin
• Variola major


  A highly virulent form causing toxemia, shock, and intravascular coagulation
• Dermatophytes


  A group of fungi that cause a variety of body surface conditions
• Causative agents of dermatophyte infections


  • Trichophyton
  • Microsporum
  • Epidermophyton
• Dermatophytes


  Have the ability to digest keratin
• Streptococcus pneumoniae


  Small, gram-positive flattened coccus that appears in end-to-end pairs
• Initial treatment for Streptococcus pneumoniae meningitis


  Vancomycin + ceftriaxone, but if isolate is found to be penicillin-sensitive then treatment can be switched
• Clostridium tetani


  Gram-positive, endospore forming obligate anaerobe that causes tetanus
• Clostridium tetani


  Organism is anaerobic, and endospores cannot become established unless tissues are necrotic and poorly supplied with blood
• Treatment for tetanus


  Patient should immediately receive human tetanus immune globulin (TIG) and also Penicillin G
• Rabies (Rhabdovirus)


  This virus multiplies in skeletal muscles
• Post-exposure treatment for rabies


  Combination of passive and active immunization is indicated: Wound is infused with human rabies immune globulin (HRIG)
• Toxoplasma gondii


  Can be transmitted via cat feces, most cases are asymptomatic or marked by mild symptoms such as sore throat, lymph node enlargement, and low-grade fever
• Prions


  Cause neurodegenerative diseases with very long incubation periods (years) but rapid progressions, including Creutzfeldt-Jakob disease (CJD), Gerstmann-Strussler-Scheinker disease, and fatal familial insomnia
• Clostridium botulinum


  Endospore-forming anaerobe that does damage through the release of an exotoxin
• Clostridium botulinum toxin


  Travels to the neuromuscular junctions of skeletal muscles and prevents the release of acetylcholine, the neurotransmitter that initiates the signal for muscle contraction
• Onset of botulism symptoms


  Usual time before onset of symptoms is 12 to 72 hours, depending on the size of the dose
• Septicemia


  Low blood pressure is a hallmark of this condition caused by the inflammatory response to infectious agents in the bloodstream, leading to a loss of fluids from the vasculature
• Gram-negative sepsis


  Gram-negative bacteria multiplying in the blood release large amounts of endotoxin
• Gram-positive sepsis


  Gram-positive bacteria can instigate a similar cascade of events when fragments of the cell wall are released into the blood
• Gram-negative bacteria commonly causing sepsis


  • E.coli
  • Proteus
  • Pseudomonas
  • Enterobacter
• Gram-positive bacteria commonly causing sepsis


  • Staphylococcus aureus
  • Streptococcus pyogenes
  • Group B streptococcus
  • Enterococcus faecium and E. faecalis
• Yersinia pestis


  Tiny, gram-negative rod also known as the "Black Death"
• Symptoms of plague


  Acute symptoms of headache, backache, fever, chills, coughing, and weakness appear. Presence of bacteria in the blood results in disseminated intravascular coagulation, subcutaneous hemorrhage, and purpura, which may degenerate into necrosis and gangrene
• Lyme disease


  Causes a rash at the site of a tick bite that looks like a bull's-eye with a raised reddish ring that gradually spreads outward with a pale central region
• Borrelia burgdorferi


  The bacterium is very good at evading the immune system by changing its surface antigens while it is in the tick and again after it has been transmitted to the mammalian host
• Immune response to Lyme disease


  Provokes a strong humoral and cellular immune response
• Malaria


  Caused by Plasmodium vivax and P. ovale, which are subject to relapses because some infected liver cells harbor dormant protozoans for up to 5 years
• Treatment for malaria


  Artemisinin, a plant compound, has been most effective in treatment of this disease
• Scarlet fever


  Result of an infection of Streptococcus pyogenes infected with a bacteriophage that produces erythrogenic toxin
• Scarlet fever symptoms


  Produces a sandpaper-like rash with high fever, with a fatality rate up to 95% if untreated
• Whooping cough


  The organism responsible is Bordetella pertussis