Review for Lab Exam #2 Notes

Adhesion

Proteins that help bacteria stick to the host

Colonization factors

Proteins that allows bacteria to colonize certain parts of the body

Biofilm

Communities of bacteria that take in and share nutrients

Toxins

Bacteria releases poisons, hemolysins, C. diff

M proteins

Proteins that help bacteria evade phagocytosis

Coagulases

Enzymes that produce fibrin from fibrinogen at the infection site, clot protects from phagocytosis

Capsule

Glycocalyx surrounding each bacterial cell, prevents phagocytosis

DNAse

Lyses DNA, helps bacteria escape DNA nets that neutrophils spit out

Why is hemolysis preformed on Sheep blood agar?

To see if it has the ability to lyse RBCs

• virulence factor

Gamma Hemolysis

No change around isolated colonies

Alpha Hemolysis

Change around isolated colonies, brownish/greenish zones around colonies

Beta Hemolysis

Change around isolated colonies, clear zones around colonies i.e yellow

What does an elevated WBC count mean?

INFECTION!

Neutrophils

High numbers mean localized bacterial infection

• phagocytic cells

• 40-75%

Lymphocytes

High numbers indicate viral infections, whooping cough, or some cancers

• low numbers may indicated HIV

• T/C cells

• 20-50%

Eosinophils

High numbers indicates allergic rxn or parasitic helminth worm infection

• 5%

Mnemonic for cell counts

• NEVER

• LET

• MONKEYS

• EAT BANANAS

How is blood type determined?

A specific surface antigen, and an anti-sera will cause antibody mediated crosslinking of cells and agglutination

• Blood type A → B antibodies

• cannot have the same type of would self react

  • O has both, AB has none

PCR

amplifies a specific region of DNA

• each product requires two individual primers

DNA Fingerprinting PFGE

Bands represent the entire chromosome

In PCR, which band tell you the organism?

16s rDNA

Catalase test

Differentiates Staphylococcus from Streptococcus

• + Staph

• - Strep

Coagulase test

Positive ID definitive for Staphylococcus aureus

Mannitol salt agar

Selective for salt tolerant skin flora (G + rod/cocci)

• Differentiates between organisms that ferment mannitol and don’t

BOTH

MacConkey Agar

Selective for gram neg enteric rods (gut flora)

• differentiates between lactose fermenters and non-lactose fermenter

BOTH

Staph Aureus

Gram positive

Catalase Positive

Coagulase +

Streptococcus Pyogenes

Gram positive

Catalase -

Beta hemolysis

Enterococccus

Gram Positive

Catalase -

Coagulase -

Gamma Hemolysis

E coli

Gram negative

Lactose fermenter on MacConkey

Indole +

Pseudomonas

Gram Negative

Non lactose fermenter on MacConkey

Oxidase +

Fruity Odor and Pigment

Proteus

Gram Negative

Non-lactose fermenter on MacConkey

Oxidase -

Swarming +

Antigens

Specific components of a pathogen that are recognized by the immune system

• antibodies bind to the epitope on the antigen

Direct ELISA

Detects pathogen directly using a capture antibody

Indirect ELISA

Detect antibodies produced in response to a pathogen by presenting a viral antigen as bait

Streptococcus pyogenes Group A strep

Beta hemolytic

Bacitracin senstive

Hektoen-Enteric agar

Selective for gram negative rods

• lactose fermenting, + yellow/orange