Chapter 6 Gram Positive

Staphylococcus
 Anaerobes
  (motile/nonmotile)
Grows best   (anerobically or aerobically)

What is this organism?

Staphylococcus are Catalase-  (Streptococcus are catalase- 

3 most important species of staph
1. 
2.  
3.  

S. aureus most  (coagulase- ) **** Only S. aureus is

S. epidermidis (agent of opportunistic infections associated with
  equipment ( ,  , …)

S. saprophyticus (agent of ,  )

Coagulase-Positive:   (carrier);  (person
with lesion),   (person with lesion) or  (Survive
long periods of drying);

Coagulase-Negative
  (infections associated with
implanted catheters and prosthetic devices; UTI)

About 30% of individuals carry  in the anterior nares

Coagulase-negative species are   flora of skin, nares and ear canals

Staphylococcus aureus causes furuncles ( ) and carbuncles ( )

Most Relevant Virulence Factor for Staphylococcus is  
  toxin that damages membranes of
the skin cells (and erythrocytes); causes marked
 of the skin and  

Staphylococcus aureus causes  .  cause large blister in superficial skin. Causes bullae rupture-oozing yellow crusts.   causes pruritic lesions that form honey crusts.

Bullous impetigo has   which targets   and it degrades  

Staphylococcus aureus causes scalded skin syndrome. It causes  ,  , and  of remote sites. It has   which targets  .

Scalded skin syndrome is AKA  

Staphylococcus aureus causes infectious  

Symptoms of staphylococcus aures invlude symptoms of   (heart murmur, shortness of breath, swoleen feet), ,   on hands and soles, and  noduces, r hemorrage,  lesions, and conjuctival  .

Infectious endocardidits can only occur with existing  .

Infectious endocardidits can  to a distant site.

 
(dark-red, linear lesions in nail
beds)

 
(microbleed from broken
capillaries due to emboli)

 
(tender subcutaneous nodules
usu. found on distal pads of
digits)

 
(painless macula on the palms
& soles)

Staphylococcus aureus causes pneumonia and the primary virulence factor is  

With pneumonia,   activates   and activates the secretion of   and . Respiratory epithelial cells express  and undergo apoptossis.

Osteomyelitis, post-surgical wounds, and conjunctivitis are caused by 

 is causes by superantigen activity in blood stream. Causes a diffuse, macular   that progresses to desqumation

Food posioning with an incubating of   is caused by staphylococcus aureus    and  . It is caused by a   acting in the GI that stimulates a lot of  .

While nausea, vomiting, watery nonbloody diarrhea are all associated with food posioning, there is   in food poisining.

MRSA
• <10% of  susceptible to Penicillin but many still susceptible
to  

In both cases, MRSA expressed a new resistance gene on a plasmid,
  – encodes for an alternate penicillin binding protein (PBP) or  
that resists penicillin binding and inactivation

CA-MRSA genetic distinction resided in the production of new types of
 
o  toxin that damages cell membranes (esp white blood cells)
o Severe necrotizing  attributed to CA-MRSA PVL production

Staph can be differeniated by strep because staph is  positive

S. aureus is differentiated because it is the only one that is   positive.

S. epidermidis and S. saprophyticus can be differentiated because only is sensitive to it.

Staphylococcus
Gram stain of pus, surgave swab, blood, and sputum = gram-  clusters

For staphylococcus, you are looking for the presence of variable hemolysis on a  agar plate.

 hemolysis = incomplete (has a brown/olive green color)
  hemolysis = complete lysis of RBC
  hemolysis = no lysis of RBC

Mannitol salt agar has   to inhibit normal flora growth.

Staphylococcus auerus ferments mannitol ( ) and other media remains  

Streptococccus are  ,  , form  

Blood agar is preferred because satisfies growth requirements and can
differentiate groups based upon  patterns

What organism is this?

Streptococcus is transmitted by   or  ;
In utero or during birth  ; Direct contact with   or
Contaminated   (  or  )

Streptococcus pyogenes (GAS)
-  week duration
-Causes  
- ,  ,  

Streptococcus pyogenes has an   (antiphagocytic protein),   (antiphagocytic hyaluronic acid), but the main agent is   (superantigen activty produced by certain stains lysogenized by a phage carrying the gene)

Streptococcus pyogenes (GAS)
Can cause scarlet fever in  
Occurs when the steptococci produces   (superantigen) and the host lacks antibody against toxin
Biggest symptoms are   and 

Streptococcus pyogenes (GAS)
 
Caused by untreated strep throat or scarlet fever
- ,  (jerky motion), and painful  

RHEUMATIC FEVER
Occurs as a cross-reactive Ig against   recognizes heart and joint antigens, activates complement and phagocytes

Streptococcus pyogenes (GAS)
ACUTE POST-STREPTOCOCCAL
GLOMERULONEPHRITIS (PSGN)
-10 days after   or 3 weeks after  
-Dark /  (high protein)
- 
-Decreased  

ACUTE POST-STREPTOCOCCAL
GLOMERULONEPHRITIS (PSGN)
Cross-reactive Ig against streptococcal antigens bind and form   which deposit in the kidney
  – triggers complement and phagocytes

Impetigo (both bollous and non-bullous forms) can also be formed by  

Streptococcus can cause   infections deep in the tissue. It has a "shiny" texture

Erysipelas
-Rash on face that has  
-  is also present

  can also be called by streoptococcus pyogenes, but it is caused by pyrigenic exotoxin A, which releases large amounts of cytokines friom T cells and macrophages

Streptococcus pyogenes can cause necrotizing fascitis due to  , which is a protease that rapidly destroys tissue

Both staph and strep do   hemolysis

S. pyogenes is high suspectible to  

Streptococcus agalactiae (GBS)
-Causes disease in  
- ,  , and  

Streptococcus agalactiae (GBS)
Main virulence factors is the capsule, which is 
Also binds to   in serum to aid in degrading  to prevent  

To test for Streptococcus agalactiae (GBS), use the   test. It detects sodium  . Positive for  .

The CAMP tets is also used for Streptococcus agalactiae (GBS). It is the the only -hemolytic streptoccoi which has a positive camp test! It grows in an arrow towards  

Viridans Group Streptococci (VGS)
-Agenets of  
-Alpha hemolytic and lack a  , resistent to  

S. mutans
Are isolated from  cavity
Associated with  

VGS can lead to
1. Infectious  
2. Brain  
3. Abcesses of    , and  

VGS diseases are diagnosed using   hemolysis on blood agar plate and resistence to   on  

Group D Are
 and  

Growth in 6.5% NaCl = only  ; all others are
 

Bile esculin test
• Bile inhibits Gram- 
• Esculin is hydrolyzed to
  + d 
• Esculetin reacts with ferric
chloride to form 

ENTEROCOCCUS
E. Facealis
-Part of gut flora and causes  
-  or   hemolytic; positive for bile   test

 complex
-  on blood agar; negative for   test
-Associated with  ,   and many  
(IBD, bleeding, etc)

Streptococcus pneumoniae causes both   and  . Leading cause of   world-wide. Causes 1 in 3 cases of  .

The main virulence factor for streptococcus pneumoniae is  . Directly cytotoxic to   and impairs action of  . It suppresses  .

The three leading causes of bacterial meingitis are  ,  ,  

Pneymoncoccal disease is the most frequent cause of   infection.

For s. pneumonaie, the organism is specific because it is gram    

S. pneumoniae has a bile test that is   for  

S. pneumoniae expresses   that disrupts the cell wall and kills bacteria as a means to release   which causes tissue damage. Bile salt activates .

Microccus luteus
Strict  ;   or irregular  

Micrococcus luteus is a pigmented bacteria that produces   colonies on nutrient agar

Micrococcus luteus is sensitive to   and can withstand massive doses of   radiation

Micrococcus luteus can cause odors in humans and leads to common infection in  

Transmission of micrococcus luteus is often by direct or indirect contact with contaminated person or objects (often transmitted due to poor   practices)

Micrococcus luteus are considered to be opportunistic because they do not impact  

Micrococcus luteus causes
1.  
2.  
3.  
4.  

M. luteus has gram   (shape),   on nutrient agar, positive for  . Similar to staph, it is catalase