Microbiology Lab Exam 2

Biofilms

• communities of bacteria that take in and share nutrients

• immune response blockers

Virulence factors

bacteria use virulence factors to defeat and trick our immune system so they can cause disease

Colonization factors

proteins that allow bacteria to colonize certain parts of the body

Toxins

• bacteria release poisons

• hemolysins, C diff.

Immune response blockers

inhibit the host immune system defenses

M proteins

fuzzy layer that is similar to proteins found on surface of host cell, help bacteria evade phagocytosis

Coagulases

enzymes that produce fibrin from fibrinogen at the site of infection, clot offers protection from phagocytosis

Capsule

glycocalyx that surrounds the bacterial cell, prevents phagocytosis

DNAse

lyse DNA, neutrophils spit out nets of DNA to capture invading bacteria, DNAse is a mechanism used by bacteria to escape these nets

Hemolysis

streak bacteria on sheep blood agar to see if it has the ability to lyse red blood cells

• identify hemolysis from isolated colony

• function in the body to lyse white blood cells

Gamma hemolysis

• no change around or under isolated colonies

Alpha hemolysis

change around isolated colonies → brownish or greenish circular zones around colonies (not transparent)

Beta hemolysis

change around isolated colonies → clear zones around colonies

Bacterial infection

high numbers of neutrophils indicate localized bacterial infection

Raised eosinophils

high numbers indicated allergic condition or parasitic (helminth/worm) infection

ABO-blood typing

• clumping = present

• don’t give a patient an antigen they don’t already have

• if specific surface antigens are present: anti-sera will cause antibody mediated crosslinking of cells and agglutination

Rh-factor

not natural so have IgG memory after first exposure

PCR

to test for the presence/absence of a gene

PFGE

to compare the relatedness of different isolates