Gram positive pathogens (complete) Flashcards
Are Staphylococcus normal flora
yes, but they can be opportunistic pathogens
What are the nine groups of Gram positive pathogens we study
- Staphylococcus Aureus
- Streptococcus Pyogenes (A)
- Streptococcus pneumoniae
- Bacillus Anthracis
- Clostridium (perfringins, dificile, tetani, and botulinum)
- Listeria monocytogenes
- Corynebacterium diptheriae
- propionibacterium acnes
- Actinomyces species
Staphylococcus is motile or nonmotile?
non-motile
how does Staphylococcus interact with oxygen (anarobe, aerobe)
facultative aerobe
What does Staphylococcus look like under a microscope
cocci in irregular clusters (grapes)
What is the most common organism found on the skin
Staphylococcus epidermis
Where is Staphylococcus aureus typically carried in 30-50% of the healthy population
nose and perineum
How can you tell between Staphylococcus aureus and Staphylococcus epidermis
Staphylococcus Areus is
coagulase positive, mannitol positive
Staphylococcus Epidermis
coagulase negative, mannitol negative
which is more virulent Staphylococcus Aureus or Staphylococcus epidermis
Staphylococcus Aureus
How many bacteria are required for disease to result from a staph infection
only a few hundred bacteria
what are the three things about Staphylococcus that cause pathogenicity
- It’s ability to evade phagocytosis
- Production of enzymes
- production of toxins
What are the three categories of Staphylococcus diseases
Noninvasive disease
Cutaneous disease
Systemic disease
What is a non-invasive Staphylococcus disease
food poisoning that results from ingested food contaminated with enterotoxin
What are examples of cutaneous Staphylococcus disease
scalded skin syndrome
impetigo
folliculitis
furuncles
How does Staphylococcus defend itself against phagocytosis
Protein A
Bound Coagulase:
how does Protein A help Staphylococcus defend against phagocytosis
Protein A onthe bacterial surface binds antibodies by the Fc end. This inhibits opsonization and complement
how does bound coagulase help Staphylococcus defend against phagocytosis
converts blood protein fibrinogen into fibrin molecules, which make blood clots, the Staphylococcus hides from the phagocytes in the clots
What are the 5 enzymes created by Staphylococcus that attribute to its virulence
Cell-free coagulase hyaluronidase staphylokinase lipases B-lactamase
What does Cell-free coagulase do for Staphylococcus
triggers fibrin formation, which helps the Staphylococcus hide from phagocytes
What does hyaluronidase do for Staphylococcus
breaks down hyaluronic acid, which allows the bacteria to spread between cells
what does staphylokinase do for Staphylococcus
dissolves fibrin threads in blood clots, which allows Staphylococcus aureus to free itself from clots
what do lipases do for Staphylococcus
digests lipids, allows Staphylococcus to grow on the skins surface and in oil glands
what do B-lactamases do for Staphylococcus
Breaks down penicilins, makes them resistant to beta-lactams
What are the 4 toxins produced by Staphylococcus
Cytolytic toxins
exfoliative toxins
Toxic shock syndrome toxins
Enterotoxins
What are the two cytolytic toxins created by Staphylococcus and what do they do
alpha-toxins- pore forming toxins
PVL - beta pore forming toxin that lyses leukocytes
What do the exfoliative toxins of Staphylococcus cause
they cause the patients skin cells to separate from each other and slough off the body
What does the toxic shock syndrome toxin of Staphylococcus cause
it causes toxic shock syndrome, which is caused by the creation of a superantigen
What do enterotoxins of Staphylococcus cause
they stimulate intestinal muscle crampings, naseua, and intense vomiting (staph food poisoning)
Does Staphylococcus aureus cause food poisoning
yes
Does Staphylococcus cause colitis
yes
what is colitis (caused by Staphylococcus )
overgrown Staphylococcus aureus in the bowels (caused by broad-spectrum antibiotic treatment), when they produce enterotoxin B you get damage to intestinal mucosa, cramps, pain, diarrhea, and fever
What are the 4 skin diseases caused by Staphylococcus aureus
impetigo
furuncles (boils) (infected hair follicle)
Carbuncler (many boils)
Scalded skin syndrome
What are the 5 systemic diseases caused by Staphylococcus
Toxic shock syndrome Bacteremia Endocarditis Pneumonia Osteomyelitis
What causes Toxic shock syndrome
the TSS toxin (from Staphylococcus ) being absorbed into the blood, and being used as a superantigen, which causes T-cells to produce far too many cytokines
what are the symptoms of toxic shock syndrome
high fever, rash, vomiting, diarrhea
renal, liver, and blood involvement
What is bacteremia
bacteria in the blood
What is endocarditis
when bacteria attack the lining of the heart
what is pneumonia
inflammation of the lungs in which the alveoli and bronchioles become filled with water
what is osteomyelitis
inflammation of the bone marrow and surrounding bone
What is the drug of choice to treat staph infections
Methicilins
Are any Staphylococcus organisms resistant to methicilins? what are they called
yes, MRSA (methicilin resistant staph. aureus)
What is the drug used for MRSA
vancomycin
how are staph infections prevented
- proper food prep and storage
- hand antisepsis
- proper cleansing of wounds, catheters, and needles
Which type of bacteria is tracked by phage typing
Staphylococcus
What is the arrangement of cocci in streptococcus
cocci arranged in pairs or chains
how does streptococcus interact with oxygen
aerotolerant anaerobes
What is the system of classification often used for streptococcus
lancefield classification
What are the two groups of streptococcus that are common pathogens of humans
Group A and Group B strep
What is used to determine the group of streptococcus organisms
the bacterias C antigens
What is the name for the only organism in Group A strep
streptococcus pyogenes
what does strep pyogenes cause on blood agar plates
it forms white colonies surrounded by beta-hemolysis on blood agar
What does strep pneumoniae cause on blood agar plates
it does alpha hemolysis
do pathogenic strains of streptococcus pyogenes often form capsules
yes
When do Group A strep generally cause disease
- normal microbiota are depleted
- large inoculum enable strep to establish themselves before antibodies are formed against them
- specific immunity is impaired
What does protein M of streptococcus pyogenes do
it interferes with opsonization and lysis of the bacteria, and helps the bacteria attach to keratinocytes of the host
What does a hyaluronic acid capsule do for streptococcus pyogenes
it camoflages the bacteria
What are the enzymes produced by streptococcus pyogenes, and what do they do?
Streptokinases
Deoxynucleases
C5a
They facilitate the spreading of streptococcus through the tissues
What are the toxins released by streptococcus pyogenes and what do they do
they are pyrogenic toxins, and they induce macrophages and T-helper cells to release cytokines
What do streptolysins do
they lyse RBCs, WBCs and platelets
What are the 6 diseases caused by group A strep
- Pharyngitis (strep throat)
- Scarlet fever
- Pyoderma (impetigo)
- Erysipelas
- streptococcal Toxic Shock syndrome
- Necrotizing Fasciitis
Scarlet fever is caused by a toxin of streptococcus pyogenes, what else is caused by that toxin
puerperal sepsis (an infection of the uterus)
What is scarlet fever
a rash that begins on the chest and spreads across the body, it is caused by erythrogenic toxin
What is pyoderma (impetigo)
confined, pus-producing lesions, usually on the face, arms or legs
What is erysipelas
lymph node involvement with pain and inflammation (bright red face-mask shaped inflammation)
What is streptococcal toxic shock syndrome
bacteremia and severe multisystem infections
What is necrotizing fasciitis
Flesh eating strep
strep that spreads in the deep tissues along fascia, it destroys tissues including fat and muscle. 50% mortality
What are two post-streptococcal diseases? (poststreptococcal sequelae) and what cause them
Rheumatic fever and glomerulonephritis
cross reactive antibodies
Which age group is the most common carrier and infected by streptococcus pyogenes
Children 1-15
How is Group A strep transmitted
by respiratory droplets, direct and indirect contact
How is Group A strep diagnosed
hemolysis, bacitracin sensitivity, gram morphology, catalase tests
What is used to treat Group A Strep
penicilliin G
how is group A strep prevented and controlled
isolation, early and complete treatment