Micro Lab 1 Flashcards
The total complement of normal flora at a particular body site is known as?
the microbiome
What parts of the body contain large amounts of bacteria?
the skin, nose, mouth, vagina, oropharynx, colon, anterior parts of the urethra
What is an iatrogenic infection?
an infection that is the result of a diagnostic or therapeutic procedure taken on a patient
The normal oropharynx (throat/mouth) contains what kind of bacteria?
viridans streptococci (the majority) Neisseria species Staphylococcus epidermidis Corynebacterium species anaerobic species
Viridans streptococci are all what kind of hemolytic?
alpha (green in BAP)
What bacteria causes strep throat?
Streptococcus pyogenes
What bacteria causes subacute bacterial endocarditis?
viridans Streptococcus
What bacteria is the major causes of dental caries (decay of the teeth turning it black)?
Streptococcus mutans
What flora are normally found on the skin?
staphylococcus epidermis and other ‘coagulase-negative’ staphlyococcus. These are a major cause of HAI, particularly central-line associated bloodstream infections (CLABSI).
What are diphtheroids?
gram positive pleomorphic bacilli. Found in the mouth
What kind of flora are found in the nose?
a variety of streptococcus, diphtheroids, and staphylococci including staphylococcus epidermis (~90% carriage) and staphylococcos aureus (~33% carriage)
What is the most common cause of surgical infections?
Staphylococcus aureus
What are the 5 most common pathogens associated with HAI?
Coagulase-negative staphylococcus (15.3%) Staphylococcus aureus (14.5%) Enterococcus species (12.1%) Candida species (10.7%) E. coli (9.6%)
The acid fast stain (as opposed to the common gram stain) is used to identify what kind of bacteria?
Mycobacteria
What is the basis of a gram stain?
the peptidoglycan of G+ cells is much thicker than that of G cells. A heat fixed smear of bacteria is stained with the dye crystal violet, followed by Gram’s iodine. The dye iodine complex is removed from g cells by alcohol, but is removed much slower from G+ cells
Is Eosin Methylene Blue (EMP) Agar selective, differential, both, or neither?
both
What is EMP Agar selective for? Why?
gram negative enteric bacilli because it contains dyes that inhibit the growth of gram + bacteria. Useful for detection and isolation of gram negative intestinal bacteria
What is EMP Agar differential for? Why?
on the basis of lactose; lactose fermenters forma purple or black colony, or one with a dark center and transparent, colorless periphery.
Differentiates between:
- Proteus species- lactose negative (appear uncolored, i.e same purple color as medium)
- E. coli- lactose positive (appear dark purple/black with a characteristic green sheen)
- Klebsiella- lactose positive- appear larger than E. coli, mucoid, and contain areas of brown/black
Are mannitol salt Agar selective, differential, both, or neither?
both
What is mannitol salt Agar selective for? Why?
staphylococci because its high salt content inhibits the growth of most other organisms
What is mannitol salt Agar differential for? Why?
gram positive, catalase positive staphylococcus species
mannitol salt agar contains the pH indicator phenol red, which turns from red to yellow below pH 6.8. Acid produced by S. aureus causes the color change. S. epidermidis does not ferment mannitol (i.e. no color change occurs)
May need 36 hrs to be accurate
Is Sodium chloride broth (6.5%) selective, differential, neither, or both?
selective
Why is Sodium chloride selective?
because high salt content typically kills other organisms, but not enterococci species.
What does the coagulase test differentiate between?
differentiates between staphylococcus aureus and other staphylococcus species.
Coagulase positive= aureus
negative= other (usually S. epidermidis
