medical

• Bacteria


  Medically important
• Staphylococcaceae


  • Gram positive, spherical cells, arranged in grapelike clusters
  • Non-motile and non-spore forming
• Staphylococcus


  • Facultative anaerobes
  • Non-motile, non-sporadic, non-encapsulated
  • Halotolerant
  • Habitat: Human skin and nose, dust, sputum samples
  • Mode of transmission: via contaminated hands
• Scalded Skin Syndrome


  • Sloughing off of the epidermis
  • Reddening and wrinkling of the skin
  • Blisters that contain fluids but lacks white blood cells and bacteria
• Toxic Shock Syndrome


  • Multiple organ involvement; epidemic in women using tampons
  • Sudden onset of fever, chills, vomiting, diarrhea, hypotension, severe red rash which progresses to desquamation
  • Hypotension
• Staphylococcal Food Poisoning


  • Primary means of bacterial intoxication due to the presence of enterotoxin from contaminated food
  • Nausea, diarrhea, abdominal cramping, loss of appetite, vomiting, fever, difficulty of breathing, headache and weakness
  • Self-limiting infection and does not progress to fatal disease
• Staphylococcus epidermidis


  • Normal flora (microbiota) of the skin
  • Novobiocin susceptible
  • Often contaminant (blood cultures)
  • Normal on skin & mucous membrane
  • Opportunistic pathogen
  • Common cause of hospital acquired UTI
  • Infects prosthetic devices (endocarditis)
• Staphylococcus saprophyticus


  • Putrid odor (Sapro-putrid)
  • Novobiocin resistant
  • Normal flora of female genital tract and perineum
  • Urinary Tract Infection in young healthy, sexually active women
  • Second cause of cystitis "Honeymooner's cystitis" (apart from Escherichia coli)
  • Uroepithelial tropism
• Streptococcaceae


  • Gram positive cocci in chains or in pairs
  • Non-motile, non-spore forming
  • Facultative anaerobe
  • Some are fastidious organisms
  • Capnophilic
• Streptococcus


  • Susceptible to bacitracin
  • Habitat: Human throat and the skin (but NOT a normal flora of the upper respiratory tract and the skin)
  • Mode of transmission: Via respiratory droplets and cutaneous lesions
• Erysipelas


  • When impetigo spreads to the lymph nodes
  • Reddening of the face and upper extremities (distinct red margin)
  • Swollen lymph nodes with pain
  • Fever and chills
  • Leukocytosis
• Necrotizing fasciitis


  • Flesh eating bacteria
  • Causes intense pain and swelling at the site of infection
• Scarlet Fever


  • Formation of diffused red rash on the face
  • Butterfly rash (cheeks); strawberry tongue
• Streptococcus agalactiae


  • Normal flora of human vagina and rectum
  • Major pathogen of newborn
  • Neonatal meningitis and sepsis
  • Pneumonia (nosocomial infection)
• Streptococcus pneumoniae


  • Encapsulated, non-motile, non-spore forming
  • Habitat: Human throat and nasopharynx
  • Mode of transmission: Via respiratory droplets
  • Pneumonia: Produces digestive enzymes in the alveoli, which dissolves the lining of the alveoli
  • Empyema: Prevents the distention of the lungs to accommodate oxygen
• Pseudomonas aeruginosa


  • Gram-negative rods
  • Motile (polar flagella - monotrichous)
  • Strict aerobes
  • Habitat: Environmental water sources, hospital respirators and humidifier; small amounts on the skin, upper respiratory tract and colon
  • Mode of transmission: Via water aerosols, aspiration and fecal contamination
• Pathogenesis


  1. UTI

  2. Pneumonia

  3. Meningitis

  4. Sepsis

  5. Mild otitis (swimmer's ear)

  6. Eye infection

  7. Folliculitis- associated with poorly chlorinated hot tubs and swimming pools

  8. Wound infection: Produces water soluble pigments produces the characteristic blue-green pus

  9. Ecthyma gangrenosum - black necrotic lesion surrounding the wound