Haemophiles Flashcards
What are some general characteristics of haemophilus ?
- tiny gram (-) rods (cocco bacillary)
- require growth factors (x and v factor)
- fastidious aerobes (specific nutritional needs)
What is x factor ?
hemin from hemoglobin
- comes from RBCs
- is heat stable (can resist heat)
What is v factor ?
nicotinamide adenine dinucleotide (NAD)
- coenzyme in production of ATP
- heat labile (heat will destroy it)
- also contained in RBCs
Where is v factor found in ?
yeast extract, staph and Neisseria species
On what types of agar do we see the maximum grow of haemophilus ?
rabbit and horse blood agar
On what agar does haemophilus not grow on and why ?
sheep blood agar plate (BAP)
- also has v inhibiting substance that makes v factor unavailable
What factors are on sheep blood agar plates (BAP) ?
both X and V factor
- also has v inhibiting sustance
What factors are on rabbit and horse blood agar ?
both X and V factor
- doesn’t have V inhibiting substance
- not commonly used in lab as its less stable then sheep BAP
What type of agar is most commonly used in for isolating haemophillus ?
chocolate agar (heated BAP)
What factors are required for H. influenzae growth ?
both X and V
How can we grow haemophilus on a sheep agar plate ?
by using the satellite test/method
How do you perform a satellite test on sheep BAP ?
- streak bacteria you suspect is haemophilus then make a heavy/thick streak of S. aureus over it then incubate and look for growth
Where is the growth of haemophilus going to be found with a satellite test and why ?
only in the hemolytic zone (where RBS lysis has occured) that is along the S. aureus line
- V inhibiting factor is gone in the hemolytic zones because the S. aureus has destroyed it and v factor is produced in these areas
What is chocolate agar ?
variant of BAP containing RBCs that have been lysed by heating
- kills RBCs and releases X and V factor for RBC
- destroyed V inhibiting substance
- changes blood color to chocolate color
What is the factor test for Haemophilus ?
Tryptic Soy Agar (TSA) plate
- identification of type of haemophilus
What is the Tryptic Soy Agar (TSA) plate ?
basic nutrient agar with no growth factors
- you put discs impregnated with X, V, and XV factors onto the plate
- examine growth around the disc
How do you perform the factor test ?
- spread bacteria first on plate, get paper discs that are impregnated with X, V, and XV factor, then incubate for 24 hrs and look for growth
- whereever there is growth is the factor the bacteria need to grow
What factors are needed for growth of H. influenzae ?
both XV
What factors are needed for growth of H. parainfluenzae ?
V factor
- as long as it has V factor in to
(V factor, XV)
What infections are caused by H. influenzae ?
- meningitis
- pneumonia (after viral pneumonia)
- epiglottitis (often fatal)
- pink eye (most common- contagious)
What infections are caused by H. parainfluenzae ?
rarely seen as pathogens
- normal throat flora
What are some characteristics of H. influenzae ?
- both X and V factor to grow
- small greyish colonies on Choc agar
- no growth of pure culture on Sheep Blood Agar
- shows growth of pure culture on Choc agar
- tiny gram (-) rods
What are some characteristics of H. parainfluenzae ?
- requires at least V factor
- small greyish colonies on Choc agar
- tiny gram (-) rods
- no growth on sheep blood agar
How is the Beta Lactamase test done ?
- PCN is suspended in broth
- bacteria placed in suspension
- Is bacteria possesses beta lactamase, penicillin is broken down into penicilloic acid which causes a drop in pH
