microbio test 2

-most pathogenic of the staphs
-Produce and secrete several toxins and enzymes that act on host immune system to mediate cell destruction
-causes superficial skin infections, deep infections that can cause bacteremia, scaled skin syndrome, toxic shock syndrome

-Ubiquitous member of normal flora and often encountered in the laboratory as a contaminant
-Normal flora: skin and mucous membranes; distributed widely over body surface
-Can cause infections in immunocompromised patients.
-associated with indwelling prosthetic devices, catheters, cardiac valves & joints, UTIs

-Second most common cause of uncomplicated UTIs in women
-Normal flora: skin and mucosa of the urogenital tract
-can cause UTIs in young sexually active females

-related to staph, similar to s. epi
-part of normal flora but like s. epi it can cause infections in immunocompromised
-can have yellow pigment, can also be white like s. epi

-The catalase test detects the presence of the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide to H20 and O2
-Hydrogen peroxide is toxic to cells therefore bacteria must produce enzymes responsible for breaking it down
-only certain bacteria produce the enzyme test

staph sap or microccoucs

-Coagulase is an enzyme that converts fibrinogen into fibrin, which results in a visible
clot
-rabbit plasma is used
-staph aureus is the only staph that is + or forms a clot

mix bacteria and certain bacteria grows, not all bacteria grows

we will see different colors and different things

-a growth medium containing the sugar mannitol and high concentrations of salt
-Mannitol salt agar is both a selective and differential medium used to detect staphylococci
-Selective because it contains a high concentration of salt (7.5% NaCl) which allows for growth of only salt-tolerant (halophiles) staphylococci to grow
-Differential because it contains mannitol and the pH indicator phenol red. Fermentation of mannitol by pathogenic staphylococci produces acid, which decreases the pH and causes the agar to change from red to yellow

-staph aureus, will grow yellow
-all coag negative staph, won't ferment

-used for additional testing when it is known the bacteria is not staph aureus
-staph sap is novobiocin positive meaning it grows right on the disk
-all other CNS are novobiocin negative, meaning they have a zone of inhibition when they grow

-micrococcus species are FX disk positive, meaning they grow right up to the disk
-all other CNS are negative, meaning they have a zone of inhibition

-also selective and differential media
-one side has S. aureus CHROMagar (cloudy side)
-one side has MRSA CHROMagar (clear side)
-cloudy side has colonies= S. aureus
-both sides have colonies= MRSA

-nasal hairs, lysozyme, convoluted passages, coughing, sneezing, swallowing

bacteria is most commonly found in the upper respiratory tract which includes streptococci (teeth, mucus membranes, throat)

the lower respiratory tract is free of micororganisms

-most common cause of strep throat
-can produce toxins and hemolysins that contribute to tissue destruction and invasion aka necrotizing fasciitis
-never normal in body

-if not treated sequeale can occur leading to rheumatic fever, scarlet fever, or acute glomerulonephritis

-can cause significant neonatal infection
-normal flora in female genital tract, lower GI tract, and can colonize in upper respiratory tract
-infections most common in neonates and infants
-passed from mother to baby during birth, can be caused by UTI's

-number one cause of acquired bacterial pneumonia
-causes infections in the upper respiratory tract (pneumonia, sinitius, and ear infections)
-can become invasive and cause bacterima and meningitis

-Important nosocomial infection, especially vancomycin resistant strains (VRE)
-normal in gastrointestinal tract
-most infections are hospital acquired

-Blood agar is both an enriched and differential medium and is used to detect hemolytic microorganisms
-Enriched because it contains iron and other nutrients from the blood that are needed by certain bacteria to grow (many are pathogenic)
-Differential because Streptococcus and Staphylococcus produce toxins called hemolysins that can break down RBCs causing a visual change in the media

causes partial lysis of RBCs and breakdown of hemoglobin which leads to a green color change in the agar

causes complete lysis of RBCs and breakdown of hemoglobin which leads to a colorless clearing in the agar

an organism that is non-hemolytic

strep. pyogenes

strep. agalactiae