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Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 1 of 8
Gram + = gram positive; Staphylococcus aureus (SA); S. epidermidis (SE); Virulence factor (VF)
Gram Positive Bacteria
I. Objectives [S1]:
a. Introduction to several group of important groups of microorganisms that cause human disease; talk about their
habitats, types of infections they cause, specific virulence factors, laboratory characteristics, how you identity
people with the disease, and insights into their importance in the overall contribution to human disease.
b. Two step approach: lectures and labs where you will be able to see the microorganisms and look at the case
studies with different diagnostic tests and how they can be identified in a laboratory.
c. [S2] Go over the characteristics, epidemiology, virulence factors, associated diseases, and laboratory
detections of clinically important gram + positive cocci and gram + positive bacilli.
d. Will discuss staphylococcus, streptococcus, enterococcus, listeria, corynebacterium, and bacillus.
e. Other gram + bacteria that are important but do not need to know all of them.
II. Staphylococcus [S3]
a. General information
i. Very important human pathogen---most important in the genus Micrococcaceae.
ii. Two other genera in the family—stomatococcus & micrococcus
1. Not important causes of human disease
2. Undergoing taxonomic changes; organisms found in mouth and skin, but rarely cause human
diseases except in extraordinary circumstances
iii. Diagram of Staphylococcus aureus (SA) on the slide—looks like a bunch of grapes; bacteria are really
colorless; must be colored in order to see them in clinical specimens—reason for the gram stain.
iv. Gram staining is used to characterize and color bacteria
v. SA is a gram + that appears and grows in groups or clusters; name means “grape-like.”
III. Habitat [S4]
a. SA
i. is the most important pathogen in the staphylococcus group—most important human pathogens overall
ii. Very successful pathogen due to the way it can exploit the niches in the human body; some bacteria can
cause disease in normally healthy people; other bacteria must wait until defenses are down to cause
disease—called “opportunists.”
iii. Reason for success it because it can find a way to live in body without causing disease; found in the nares
of 50-75% of healthy people
iv. Adapted micro ecological habitat so it can exist in human without causing disease, yet successful pathogen
because if the given the right circumstances or if it is found in the right part of the body, it can cause
devastating diseases.
v. Important pathogen in healthcare setting due to nosocomial infections—infection acquired in a healthcare
setting; many people get infections from being at the hospital due to the fact that hospitals harbor bacteria,
there are lots of antibiotics present that selective for the most resistant bacteria and the most successful
bacteria can move around and live on inanimate surfaces like bedside toilets, bed rails, etc. and from
person to person from people that are colonized with the organisms that can cause disease.
vi. Very important nosocomial organism because it can live on inanimate surfaces for long periods of time
b. S. epidermidis & other groups of staphylococci—not as important human pathogens
i. Staphylococcus epidermidis is common on the skin; on the skin of everyone in the room; as long as it stays
on the skin, it usually doesn’t cause problems; much less of a virulent organism than SA
ii. SE is also in your conjunctiva even though it does not usually cause disease there.
c. S. saprophyticus
i. Mainly known to cause urinary tract infections in young women; not usually cause infections in men
because they are not as common in men due to the fact that women have a short urethra and it is easier
for the bacteria to get into the urinary tract from the outside.
IV. Lab Characteristics of all staphylococci and differentiating characteristics that will allow you to separate them—if
you suspect a patient has a staphylococcal disease, you must collect a diagnostic specimen so you can find the
staphylococcus and then determine what type it is so you can determine if it is likely to cause disease, the type of
management that you would provide for the patient, etc. [S5]
a. Picture of what staphylococcus looks like on a gram stain—dark purple cocci in clusters, typically in small or
large groups—can tell it is a staphylococcus but not what particular type it is—look at the gram stain and be
pretty sure that it is a staphylococcus though some bacteria can look similar
b. When looking at gram stains and bacteria in general, a gram + cocci such as a staphylococcus or a
streptococcus are about 1 micron in size (a RBC is about 6-9 microns in size), so about 1/6th the size of RBC for
comparison
c. Grow aerobically—not particular about what they grow on—very hardy organisms
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 2 of 8
d. Are beta-hemolytic—means that on a blood agar plate (soy agar with 5% sheep blood to grow bacteria—
important because most common bacteria will grow on agar; the blood cells provide enrichment and nutrients
that the bacteria need) you COMPLETELY lyse the RBC and you can see through the plate because the RBC
are lysed by the hemolysin that is present.
e. One of SA virulence factors (VF) is that it has a hemolysin that lyses the RBC; allows the RBC to open and get
the things out of the cells that it needs to grow; this is a characteristic that you can see and it is a great trait at
differentiating bacteria—whether or not they are hemolytic
i. Beta hemolytic – complete lysis of the RBC
f. Produces an enzyme called coagulase—enzyme that will convert fibrinogen into fibrin and produce a clot;
staphylococcus secretes coagulase into its environment as well as produces a bound coagulase called clumping
factor on the surface of the cells.
i. Important VF because it allows staphylococcus to protect itself by coating itself with fibrin in order to protect
it from antibodies, complement, WBC, and other things that are part of the body’s immune system that
would be trying to fight it—way of protection.
ii. Trait that will differentiate SA from other staphylococci that we refer to collectively as the coagulase
negative staphylococcus.
g. Catalase enzyme is another one produced that will help differentiate a staphylococcus from a streptococcus;
enzyme that converts hydrogen peroxide to water and oxygen;
i. Produces bubbles
ii. VF that allow it to protect itself from peroxide—can use peroxides as an antiseptic if you have an infection
you could put peroxide on the infection or wound
iii. Can it will help kill bacteria because bacteria that LACK catalase to break down the peroxides will be killed
because the hydrogen peroxide will be toxic
h. Fermentation of mannitol
i. One way to selectively grow SA in clinical specimens is to grow specimen on mannitol salt agar; contains
high concentration of about 7.5% NaCl that will keep many bacteria except staphylococcus from growing
ii. Also has mannitol in there as the sole carbohydrate source with a pH indicator—a SA will produce acid
from mannitol; the plate will change from red to yellow (depicted on the image on the slide)
iii. Mannitol fermentation (changing the plate to yellow) is another characteristic of SA.
V. Catalase Test [S6]—this test is a way to differentiate staphylococcus from streptococcus
a. Catalase test will separate staph from strep
b. 1st test to do if you have a gram + coccus and are not sure if it’s in the strep or staph group
c. See bubbles when you add hydrogen peroxide to some of the colonies—MEANS IT’S A POSITIVE TEST AND
ITS NOT A STREPTOCOCCUS and it is probably a staphylococcus
VI. Coagulase Test [S7]
a. 1st way—measure the production of coagulase by taking rabbit plasma and putting some bacteria into the tube
and wait to see if clotting occurs
b. If the plasma clots, then it’s a positive test for coagulase
c. SA will usually be positive fairly quickly; however, if the clot is not produced right way, it must be incubated for at
least 24 hours before you can conclusively say it is not an SA.
d. Microbiologists like to do things quickly so they have a more rapid coagulase test where you can actually do the
test faster by looking for clumping of latex particles that have the fibrinogen coated on the latex particles
VII. Cell Wall [S8]—many of the bacteria have various VF and antigens that can be expressed on the bacteria’s surface
a. Some VF are secreted into the environment; others are expressed on the cell’s surface
b. Some strains will have a capsule or a polysaccharide slime layer; capsule is important to help protect the
organism from phagocytosis
c. SA is an extracellular pathogen that produces disease if it can escape white cells; if white cells phagocytise it,
the organism will be killed so it cannot go out and do it’s business as a bacteria
i. capsule helps prevent its opsonizaiton
d. The slime layer that is seen in some strains of SA and other strains of staphylococci help it attach to things—
one of the best ways to get inside the blood stream of a patient that has an IV cathedar in their vein is to attach
to plastic—some staphylococci can easily attach to inanimate surfaces that allows them to hang on to keep from
being washed off or removed; important way to have organisms attach to things
e. Peptidoglycan layer—peptidoglycan is important in the cell wall structure of gram + bacteria; acts as an antigen
and helps hold the crystal violet in the cell wall during a grain stain
f. Teichoic acids—important antigenic structures—part of the structures that help bind the organism to the
epithelial cells in the host; bacteria have to have a way to attach to host to cause disease; part of the attachment
structures in gram + bacteria are related to teichoic acids and the polysaccharides there.
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 3 of 8
g. Protein A is another VF of SA—helps it to cause disease because it binds to the Fc fragment of IgG; it binds the
Fc fragment of IgG and destroys the antibody, the antibody can’t opsonize the bacteria; another way bacteria
has in order to evade the host’s immune response
h. All of the stuff provides the rigidity of the cell wall to keep the bacteria osmotically stable; on the outside of the
cytoplasmic membrane
i. Clumping factor—bound coagulase mentioned earlier
VIII. Antigenic Structures & VF of SA [S9]
a. In addition to things about binding the fibronectin on the host cell, teiochic acid is part of the staphylococcal cell
wall that helps produce the pyogenic effect—hallmark feature of staphylococcal infections are puss-forming
abscesses; pyoderma or pyogenic infections of inflammatory cells, primarily neutrophils—typical of
staphylococcal infection
b. Peptidoglycan of the cells wall is partly responsible for the stimulation of neutrophils to come to the site of
staphylococcal infection which causes the pyogenic effect
c. Production of interleukin and opsonic antibody isvalso part of the peptidoglycan cell wall and activation of
complement—important in terms of VF
IX. Soluble VF of SA [S10]
a. Secreted by the cell—ex. coagulase and catalase
b. Hyaluronidase—hyaluronic acid is part of the glue that holds the tissues together
i. Keeps the skin and tissues solid—not many bacteria can cause disease if skin is intact because skin is one
of the most important forms of protection in bacterial infections
ii. A break in the skin will allow bacteria to get into subcutaneous tissues.
iii. One of the 1st things that a staphylococcus or a streptococcus does once it gets inside the skin is to start to
produce hyaluronidase that breaks down the hyaluronic acid and allows the organism to spread through the
facial planes to the tissues to spread throughout the body and get into the blood stream
iv. Very important VF
c. 90 plus % produce beta lactamase—enzyme that bacteria produce that breaks down beta lactam antibiotics like
penicillin
i. When penicillin was 1st introduced into clinical practice in the 1940’s, all staphylococci were susceptible to it
because it would prevent the cell walls from being formed; in a few years, the bacteria developed the beta
lactamase enzyme that would destroy the antibiotic before it could destroy the bacteria; the antibiotics are
not active any more—once the beta lactam ring of penicillin is broken open, it can’t do anything to the cell
well
d. MRSA (methicillin resistant SA)—comprise about 60% of all staphylococci that are seen in the hospital;
becoming more important as a cause of community acquired infections; are altered penicillin binding proteins
i. Bacteria synthesize cell walls with the chains of the carbohydrates, NAM & NAG, bound together by amino
acids
ii. The cross linking of the cell wall carbohydrates are catalyzed by enzymes, the carboxypeptidases and the
endopeptidases that we know collectively as the penicillin binding proteins.
iii. Penicillin works because the beta lactams resemble the substrates for the amino acids of the penicillin
binding proteins; bind irreversibly to the penicillin binding proteins and prevent them from cross linking the
cell walls
iv. Staphylococci that are the MRSA strains have an altered penicillin binding protein that does not recognize
the beta lactam so the cell wall cross linking takes place—important VF because it entirely wipes out a
whole class of antibiotics and gets these bacteria
v. Makes them much for difficult to treat and then they spread from person to person and cause lots of
morbidity and mortality in the hospital
vi. Now seeing these in the community acquired variety of staphylococcal infections so doctors are now
learning about this and realize about the altered penicillin binding proteins
1. recognize that they have to prescribe different antibiotics.
e. Other important enzymes are the fibrinolysins, the lipases, and the nucleases—also things that help destroy
components of the host that help cause the inflammatory process and necrosis of tissue that you get in
association with the pathologic lesions
f. Very diverse organism because it can do all kinds of different things—among the many different VF that SA has,
not every strain produces every one of them; some are only produced by some strains and not by others.
g. [S11] Leukocidins—VF that are produced by some strain of staphylococcus that kills WBC; the PatonValentine leukocidin is one of the characteristics of the community acquired MRSA infections
i. If you kill the WBC then the WBC cannot kill you; so the bacteria see an advantage in doing this
h. Some of the other enzymes release lysomal enzymes which damage tissue and further causes the necrosis and
abscesses that you see
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 4 of 8
i. Scalded skin syndrome—produced by the exfoliating toxin of SA that interrupts the intercellular junctions of the
skin and causes the skin to fall off and exfoliate
j. Toxic shock syndrome—occurs as a super antigen—stimulates T cells to release cytokines, causes significant
endothelial damage and causes a rash and the overall appearance of the toxic shock syndrome was especially
associated with tampon use by women.
k. These are all exotoxins—all exotoxins that are produced by the staphylococcus
l. Some strains of staphylococcus also produce enterotoxins—can cause food poisoning because it interacts with
GI neuroreceptors and causes a lot of nausea and vomiting
i. Example of food poising that is an entoxication because you can actually ingest the performed toxin that
the staphylococcus has produced by foods such as potato salad
ii. Ingest the toxin already and the toxin causes the disease in your body even if you don’t ingest the bacteria
X. [S12] SA Diseases
a. Lots of SA infections start out as skin diseases
b. Image—impetigo on man’s face—honey crusted lesions—referred to as furuncles which are infections around a
hair follicle that actually spread and coalesce; carbuncles produced this way
c. Typically of SA disease—impetigo could also be caused by streptococci but in association with this, you can
also get cellulitis, which is a spreading inflammation of the skin (don’t have collection of pus, but is a more
diffuse inflammations)
d. Can progress to bactermia in which bacteria spread throughout the blood stream—in the worst cases of
bacteremia you can get the bacteria on heart valves and have a very bad endocarditis
e. SA can cause severe endocarditis and destroy a heart valve and patient has to undergo surgery to have valve
replaced
f. Not usual, but can cause meningitis—more common to see it as an epidural abscess around the spinal cord
g. Occasionally SA can cause brain abscesses.
XI. S. Aureus Diseases [S13]
a. Child with scalded skin syndrome; person with toxic shock syndrome rash
i. Examples of toxin-mediated diseases
b. We see pneumonia that occurs in hospitalized patients; don’t think of S. aureus as a cause of community
acquired pneumonia
c. People in hospital, especially with respiratory failures - MRSA can be a significant for ventilator associated
pneumonia in hospitalized patients
d. S. Aureus – single most common cause of osteomylitis (bone infections); can get into joints and cause septic
arthritis
e. Can sometimes get into the urinary tract cause infections; not a common cause of these
XII. Treatment of S. Aureus [S14]
a. Not going to talk about treatment – get that in pharmacology
b. Reemphasize that MRSA has caused the requirement that we have to use lots of Vancomycin in the hospital;
seeing this in the community as well
i. Causing concern for possibility Vancomycin resistant S. Aureus
ii. Seen this at UAB (intermediately resistant strains)
iii. Infections caused by the resistance factor was transmitted by conjugation from the enterococcus
iv. Vancomycin resistant entercoccus was created by over use of Vancomycin to treat MRSA
XIII. Coagulase negative staphylococci [S15]
a. Coagulase negative staphylococci
b. Opportunistic organisms
c. Don’t’ cause such severe disease in normal hosts with normal immune systems
d. Can cause blood stream and heart valve infections
i. Surgery to repair damaged heart valve – break in sterile technique in operating room – common cause
endocarditis
ii. People with damaged heart valve at risk
e. Lacking white cells (neutropenic patients) are at risk
f. Newborns, especially premature or immunosupressed – common cause of bacteremias
g. S. Saprophyticus is one of the more important organism in the coagulase negative staphylococci group that
causes urinary tract infections
h. Lump coagulase negative staphylococci, many different species, in one group because they all lack the
virulence factor coagulase
i. Few of other staphylococci positive organisms besides S. aureus; won’t deal with them today
j. Coagulase negative staphylococci is a very important common organism because it is common on the skin;
seen as a contaminant in lab specimens
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 5 of 8
i. Important to do coagulase test to know what staphylococci you are dealing with
ii. Usually not important which coagulase negative staphylococci you have because it does not make a
difference
k. Main virulence factors that these organisms have is the slime coating on the outside of the cells; protects it and
allows it to attach to catheters
XIV.
Streptococcacae [S16]
a. Includes two important genre – streptococcus and enterococcus
b. 1984- enterococcus were in streptococcus genus, but now each has its own genus
c. Both members of the Streptococcacae, different from the mircococcacae because they do not have catalase
d. See a comparison of staphylococcus (clusters) verse streptococcus – typically in chains and pairs
e. Streptococcus can produce “necklaces” or chains; appear in short chains or pairs
f. Suggestions you have looking at a gram stain to know what organism you might have
XV. Classifications [S17]
a. Many ways to classify streptococcus, including hemolysis
b. S. Aureus is beta hemolytic organism; many streptococci are also beta hemolytic
c. These are the 3 types of hemolysis (picture)
i. See how it is used to classify streptococcus
1. Complete hemolysis – complete lysis of the RBC’s in the agar
2. Alpha hemolysis – incomplete lysis. Makes the sheep’s blood agar look green
3. Gamma hemolysis – no hemolysis at all
ii. Will need to be able to classify bacteria based on their hemolysis (in lab); that will determine which ones of
these groups they belong too
d. Beta hemolytic streptococci can also be classified by Lancefield groups
i. Beta hemolytic streptococci can be grouped according to carbohydrate antigens in their cell wall
ii. Grouped and named alphabetically; start with A and go out through the letter T
1. Small number of Lancefield groups, A, B, C, F, and G, that are common causes of human disease
2. Antigenically different, different carbohydrates in the cell wall that can be recognized by antiserum;
that’s why they get different names of different Lancefield groups (group A streptococcus, group B
streptococcus, group C streptococcus, etc)
3. In some cases, Lancefield group can almost be synonymous with an important species
a. Streptococcus group A – S. pyogenes – important cause of pharygitis, rheumatic fever,
glomerulonephritis
b. Almost all of the group A streptococcus are the S. pyogneous
c. Group B streptococcus is represented by S. agalatae – important cause of sepsis, meningitis
in new borns, urinary tract infections, food borne disease
d. More complicated - number of streptococcal species that carry the group C carbohydrate;
can’t always equate Lancefield group with a specific species
e. Talk about Lancefield groups and specific species both ways; understand that some
Lancefield groups actually contain more than one species
f. Separate the streptococci based on biochemical reactions
i. Important in alpha hemolytic streptococci because we don’t have a group specific
carbohydrate that we can separate them by
XVI.
Streptococcus habitat [S18]
a. Streptococci are successful human pathogens; very common in human host
b. occur in the skin, mucous membranes, respiratory tract, urinary tract, GI tract, depending on the species
c. Agent that causes strep throat, group A strep- 1 in 5 children (20%) carry this in the winter months in their upper
respiratory tract
i. Comes out and causes the sore throat (tonsillitis)
d. S. pneumonia – most common and important cause of community acquired pneumonia and ear infections in
children, is commonly isolated from respiratory tract in low numbers from healthy people
e. Commensal organisms, occur in the absence of disease
f. The enterococci are present in the GI tract; everyone has it
i. If they stay in GI tract you are okay, but if you have a gunshot wound to be abdomen etc, they can cause
severe disease
ii. Especially hospital acquired infections
iii. Very important nosocomial pathogens where they are selected for in places where there is a lot of antibiotic
usage (hospitals)
iv. Resistant to many antibiotics
1. Giving patients many antibiotics can cause enterococcus to be all that is left and causes problems
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 6 of 8
g. Streptococcus can be spread by droplets, direct contact and fomites
i. Fomites - inanimate objects that transmit infections
1. Dirty needles
2. Stethoscopes
3. Blood pressure cuffs, etc
XVII. Streptococcus – Lab characteristics [S19]
a. Streptococci in the lab, need to be able to recognize from a staphylococcus.
b. Few clues to get:
i. Look at the gram stain
1. Image shows a positive blood culture in a patient who has a bacteremia; grown on a blood culture
a. Note the long chains of gram positive streptococci
2. Look at the S. pneumoniae in the sputum
a. Background is the WBC’s; see the gram positive diplococcic (in pairs and short chains)
b. See the pairs – think streptococcus pneumoniae
c. Are catalase negative; distinguish them from staphylococcus
d. Most grow sheep blood agar
e. Can see the hemolytic reactions on the blood agar
f. Not particular about atmosphere - aerobic or anaerobic
i. Refer to capnophilic organisms – like CO2
ii. Some strains don’t grow unless CO2 is present (enhanced environment)
g. Can be grouped according to group specific carbohydrate if they are beta hemolytic
h. Have to do biochemical typing if they are non beta hemolytic because the group carbohydrates aren’t there
XVIII. Antigenic Structures [S20]
a. Many antigenic structures and virulence factors associated with the streptococcus
b. Streptococcus produces a hyaluronic capsule that is antiphagocytic
c. Produces hyaluronidases (tissue penetration)
i. Idea is that S. pyogenes (prototype) produces capsule to avoid phagocytosis to establish itself in the host,
but once implanted in the host, it wants to grow and spread
1. Enzyme helps the spread even if the capsule has to be sacrificed to spread throughout tissues
d. S. pyogenes is beta hemolytic
e. [S21] M protein
i. Basis for some autoimmune diseases
ii. Present on the pilis (attachment structure) along with the teichoic acid
iii. Know it is a virulence factor because those that lack it are easily oposonized and phagocytized
1. Helps prevent being phagocytized by host
iv. Binds fibrinogen and fibrin degradation products and forms a coating on the surface of the bacteria to help
block complement from attaching
v. When group A streptococcus is encountered in our body, antibodies are produced against M protein
1. Over 80 different M protein types
2. Why you can get a strep A infection over and over because antibody is only specific for the type you
had before
vi. M protein is the basis for the auto antibodies produced in some people
1. Group A strep – antibodies produced against M protein of the group A strep can cross react with
antigens on heart tissue
a. Why heart values get damaged (micro and aortic value) which cause you to be at risk for
endocarditis
f. Get rheumatic fever when auto antibodies attack the heart values
i. Dental importance – a patient that has had rheumatic fever or a damaged heart value increases risk for
infections on heart value (why you ask in patient history about heart issues, values, because you are put at
risk for endocarditis).
1. Give antibiotics before invasive dental procedures (prophylatically) that might induce a transient
bacteremia.
2. This is not a problem in a person with a normal heart value; big problem for patients that have had
previous issues with their heart valves
3. Dentists should understand history of rheumatic fever heart value diseases
g. Can get glomerulonephritis following a strep infections with some group A strep
1. Type 3 immune complex – antigens from the strep with antibodies being produced against this that
precipitate in the kidneys and can cause glomerulonephritis and hematuria as a result following
group A strep infection
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 7 of 8
h. [S22] showing cellulitis of the skin due to a strep infection
i. Streptokinases are enzymes that digest fibrin
j. Erythrogenic toxin – exotoxin – what you get with Scarlet Fever
k. DNAses, various hemolysins – you can get this
l. Streptolysis O is a hemolysin that is produced by streptococci
i. How you can tell if someone has had a recent strep infection (i.e. nephritis due to this )
ii. Measure antibody produced against streptolysin O – high titer indicates a recent strep infection
m. Streptolysin S is responsible for beta hemolytic reaction
n. [S23] showing erysipelas – skin disease
i. More severe than impetigo
ii. Type of cellulitis
o. Protein F, G, D, P, A, C5 peptidases – all enzymes that are produced by strep pyogenes that help enhance the
attachment abilities and destroy antibodies; anything to help it produce local pathological lesions
p. [S24] Group B streptococcus is a pathogen of new borns and the debilitated elderly
i. Antibody against type specific polysaccharide is protective
ii. See in lab a way to differentiate group B strep from group A strep
1. Production of CAMP factor
2. CAMP test is done by taking strain of S. Aureus and put streptococcus strain on the agar plate next
to it, (not touching)
3. If group B strep – group B will produce a sphingomyelinase that will interact with the beta hemolysin
from the S. Aureus and produce an arrowhead (see image)
4. Result not seen with other streps
iii. Group B can also be separated from other groups because it can hydrolyze hippurate
XIX.
Diseases Due to Beta Hemolytic streptococci [S25]
a. Put on here to appreciate (read the names off the chart)
b. See the diseases caused by beta hemolytic cocci
XX. S. pneumoniae [S26]
a. Important organism because it is the most common cause of community acquired pneumonia—can lead to
bacteremia in about 25% of cases
b. Most common cause of ear infections in children (otis media), cause of meningitis
c. S. pneumonaie, pneumococcus, usually alpha hemolytic organism.
i. Does not contain Lancefield antigens
ii. Does have a species specific C polysaccharide as part of cell wall
d. 90 different capsular serotypes
i. Capsule is most important virulence factor
ii. Does not produce all the exotoxins that some of the other strains do
e. Lab characteristics
i. Bile soluble
ii. Optochin susceptible
1. Antibiotic compound put on filter paper, put on agar, grow S. pneumonia around it, it would be
inhibited around the disk—if you have an alpha hemolytic streptococcus that is inhibited by optochin,
that is how we identify s. pneumoniae
f. Likes CO2 for growth
g. [S27] See in sputum – inflammation. See the Quellung reaction showing the remarkable capsule of the
organism that swells when you add specific antibody against it
h. S. pneumonia – virulence factors
i. Immunogenic, anti phagocytic capsule
ii. Surface protein A –produced by all pneunomococcal strains-- inhibits opsonization
iii. Autolysisn – releases cell components—grow pneumococcus in culture after a day or so, it starts lysing
itself
iv. Pneumolysin – substance produced that is a cytotoxic; inhibits cilia activity, lyses RBC’s, activates
complement, stimulates cytokine release, which stimulates tissue damage
1. This is why pneumonia causes an outpouring of WBC’s in alveoli-- causes lobular pneumonia.
2. Get large numbers of the bacteria and white cells that are coming because of chemotaxis
3. Causes consolidation or opacity of a chest x-ray
v. See other factors that help cause disease
i. [S28] Brain of someone with fatal pneumococcal meningitis
i. Note the swelling and see pus on the base of the brain
ii. Very important cause of meningitis
FUN2: 11:00-12:00
Scribe: Maggie Law
Tuesday, November 4, 2008
Proof: Kallie Law
Dr. Waites
Gram Positive Bacteria
Page 8 of 8
j. [S29] Vaccines
i. Way to protect against the disease
ii. 23 valent vaccine that protects against 23 of the most common serotypes
1. Given to adults over 65
2. People without functional spleen or abnormal immune response or people that smoke should get it
iii. 2000 onward – 7 valent vaccine given to children
1. Reduced the occurrence in children
2. Has had some effect on otis media—now strains that are not found in the vaccine are becoming
important causes of diseases
iv. Very important respiratory pathogen; vaccine gives protection
XXI.
Viridans Streptococci [S30]
a. Alpha hemolytic – not pneumoccous that are resistant to optochin
b. Important because they are present in mouth
c. Most oral streptococci belong to mutans group
i. Cause of dental caries because they polymerize dextran to product caries
ii. If you have an abnormal heart value – can cause endocarditis
iii. Another reason to give preventative antibiotics for people receiving dental work in order to prevent the
endocarditis
d. Since they are alpha hemolytic, they do not have Lancefield antigens
e. In lab, if there is an alpha hemolytic streptococci that is resistant to optochin, it’s a viridians group streptococci;
there are other tests to use to distinguish them beyond this
XXII. Enterococcus [S31]
a. 12 species
b. E. faecalis is the most important
c. E. faecium is becoming important because it is resistant to Vancomycin.
i. Nosocomial pathogen
d. Distinguish from streptococci because they:
i. Hydrolyze esculin
ii. Grow in 6.5% NaCl
iii. Hydrolyze PYR
1. Be differentiated from other streptococci except group A strep by the PYR reaction
e. Group D strep can hydrolyze esculin, but none of the other streps will actually grow in the high NaCl
concentration
f. Present in the GI tract; low virulence but resistance to many antibiotics.
i. Hard to treat when you get one
ii. Important in hospital infections because of urinary tract infections, abscesses, abdominal infections,
(anything with abdominal surgery)
iii. Very easily can get into the body (if a patient has bowel incontinence and it gets onto the cathedar and can
get into the bladder and cause a urinary tract infection)
iv. Because of Vancomycin resistance, hard to treat but very important to do so
v. Will see this in the lab on Thursday
g. This is the completion of staphylococci, streptococci and enterococci.
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