prokaryotic lab:Lecture 15?

Presumptive Test(1)

-water placed on lauryrl tryptase broth

-contains sodium luryl sulfate(acts as a detergent similar to that found in bile which enteric bacteria can tolerate)

-bacteria able to grow here can withstand stomach surfactants

-lactose promoting growth of SLS-tolerant enteric bacteria

-bile- fluid secreted by liver into gallbladder, contains surfactants that lower surface tension

-durham tube is placed in broth, if gas is present then bacteria contains coliforms

Confirmed Test(2)

-lauryl tryptose broth used to make brillirate green lactose bile(BGLB) broth

-BGLB Broth has green dye, that inhibits gram(+) bacteria growth

-bovine bile that kills bacteria not suited for intestine

-lactose that promotes growth of enteric bacteria

-if durham tube has gas→positive for fecal coliforms

Completed Test(3)

-BGLB broth streaked on EMB plate of agar

-contain eosin and methylene blue that passes through peptidoglycan layer of Gram(+) but stop growth of gram(-) bacterial wall

-this is differential media that distinguishes bacteria that ferment lactose by excress acid production from those that dont

EMB result for E.coli

produces acid→dark colonies with green metallic shine

EMB result for Enterobacter aerogenes

non coliform→produce light pink or colorless colonies with fisheye morphology

4 tests in litmus milk

pH- due to excreted acid or alkaline products(red→acidic/blue,purpose→alkaline)

change in O/R-potential for oxygen depletion(no O2→white)

milk curdling→due to acid production making casein loose its structure

proteolysis-casein is hydrolyzed by extracellular enzymes

Fomites

nonliving objects capable of transferring disease

Nosocomial Infections

-infections acquired in a medical facility

-commonly caused by Fomites

endogenous nosocomial infections

caused by members of the patient’s own natural microflora(opposed to microorganisms that invade from the outside environment)

-from immunosuppressant drugs or large doses of antibiotics

-hard to prevent

exogenous nosocomial infections

caused by microorganisms that invade the patient from surround environment

Serratia marcescens

can cause opportunistic infection

-used in supplemental exersize

Staphylococci characteristics

Inhabit skin and mucous membranes of animals, Gram positive, Non-motile, Non-spore forming, Aerobic, Facultative anaerobic

4 characteristics of Staphylococcus epidermidis

1.)Nonpathogenic

2.)no pigment(rare)
3.)Non hemolytic

4.)Coagulase Negative

4 characteristics of Staphylococcus aureus

1.)Opportunistic pathogenic

2.)pigmented

3.)Hemolytic

4.)Coagulase Positive

Coagulation

caused by the production of coagulase enzyme by bacteria

where do we see coagulation?

in the bloodstream, for example coagulase causes a clot to form around the bacteria and prevents it from being attacked

-this is one of the virulence factors in S. aureus

Coagulase Test

agglutination=presence of bound coagulase(clumping factor)

opportunistic bacteria

normal inhabitants, but when the opportunity arises, they can cause problems

blood plasma

the remaining liquid after blood is prevented from coagulating and the formed components are removed by centrifugation

serum

the liquid that remains after plasma(contains all the soluble components) is removed

fibrinogen

soluble blood protein whose overall structure is very negative, they repel each other

thrombin

enzyme that forms bloodclot by removing the negatively charged amino acids in fibrogen

prothrombin

circulating precursor to thrombin, enzyme breaks the prothrombin to release thrombin when something abnormal happens

coagulase(textbook info)

-structure not well known

-enzyme like protein

-antigenic protein

-heat stable protein

genes that code for coagulase production occur on

plasmids

coagulase protects the staphylococci from

phagocytosis

coagulase-positive bacteria are said to be more _____ than coagulase negative bacteria

virulent

virulence factors

substances produced by bacteria that help it survive and grow(coagulase)

Hemolysis

-extracellular proteins(exotoxins)

-enhance virulence

-break down red blood cells

Hemolysin Clostridium →

gangrene

staphylococus Hemolysins→

abscesses in skin, may affect bone, joints, kidneys, lungs, heart

Alpha Hemolysins

• Causes greenish/brownish region to form under/around colonies

• Partial lysis of red blood cells – enough for hemoglobin to escape

• The green/brown color is caused by the reduction of hemoglobin

Beta Hemolysins

• Causes distinct zone of clearing

• Complete lysis of red blood cells

Gamma Hemolysins

Only growth present

Streptococcus types

produces two major hemolysins, streptolysin S(SLS) and streptolysin O(SLO)

-lyse blood cells by altering membrane permeability by damaging sterols in infected tissue cell membrane

-SLO is more important in the disease process

-SLO is inactivated by oxygen, SLS is not

blood agar

-used to detect hemolytic activity

-complex, all purpose medium, 5% sterile blood added

fastidious

microorganisms that have unusually complex nutrient requirements, a common

Blood agar serves as

differential medium because it discriminates between microorganisms that affect RBCs in one or more ways