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102 Cards in this Set

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Why do Staph aureus grow on the skin?
Because they like normal body temperature
Describe Streptococci
Non-spore forming
Nonmotile
Gram-positive
Falcultative anaerobe
Found in long beadlike chains
Describe Staphylococci
Gram-positive
Falcultative anaerobe
Non-spore forming
Nonmotile
Found in clusters
List and describe 5 virulence factors in regard to S. aureus
1. Coagulase--coagulates blood plasma
2. Hyaluronidase--digests connective tissue of host
3. Lipase--digests oils, bacteria more easily colonize skin
4. Hemolysins--lyse RBCs
5. Exfoliative toxins--Separates epidermis and dermis (desquamation)
What does TSST do?
Induces fever, vomiting, rash, organ damage (systemic) by releasing large amounts of interleukin 1 and 2 and tumor nucrosis factor
What does leukocidin significant for?
It is a exotoxin that damages cell membranes of neutrophils and macrophages, causing lysis
List the circumstances that predispose and individual to infection of S. aureus
~poor hygiene
~poor nutrition
~tissue injury
~preexisting primary infections
~diabetes mellitus
~immunodeficiency states
What is the third most common cause of infections in the newborn nursery and surgical wards ("hospital strains")
Staphylococcus aureus
What is another name for hyaluronidase? Why?
"Spreading factor" because it digests the intracellular "glue" that binds connecive tissue
What is the most important hemolysin? What are the others?
Alpha-toxin (most important)
B, g, and y (others)
What is the carriage rate of S. aureus in healthy adults? Where does carriage occur?
20-60%
Carriage occurs in nostrils and (less) on skin, in nasopharynx, and intestine
What happens after S. aureus becomes opportunistic?
It becomes the dominating cause of infection
What are the most important (prevalent) Staphylococcus pathogens in regard to humans?
1. S. aureus
2. S. epidermidis, S. capitis, S. hominis
3. S. saprophyticus
How many species of Staph have been discovered?
31
What is folliculitis?
Inflammation of hair follicles or glands
What is furuncle?
A boil that results when the inflammation of a single hair follicle or sebaceous gland progresses into a large, red abscess or pustule
What is a carbuncle?
A deeper lesion created by aggregation of a cluster of furuncles into a large mass
List 3 localized cutaneous infections
1. Folliculitis
2. Furuncle
3. Carbuncle
Name some diseases associated with toxin production by S. aureus
1. TSS
2. Food poisoning
3. Scalded skin poisoning
What is osteomyelitis?
A systemic staphylococcal infection. Pathogen is established in the metaphyses of bones (often the femur, tibia, ankle, or wrist)
What is staphylokinase known for?
Digestion of blood clots
What is the action of DNase?
Digestions of DNA
Alpha-toxin produces what action?
Beta-hemolysis
What condition (seen in people of all ages) is caused by the same exfoliative toxin that causes Scalded Skin in infants? Syndrome?
Bullous impetigo (local, blistering, bubblelike epidermal swellings)
What is the most powerful defense against Staph infections?
The phagocytic response by neutrophils and macrophages
What stimulates abcess formation?
Inflammation and cell-mediated immunity; they also help contain staph and prevent their further spread
What accounts for a large proportion of nosocomial and opportunistic infections in immunocompromised patients?
Coagulase-negative staphylococci
What is the normal habitat of Staph epidermidis? Staph hominis? Staph capitis?
S. epidermis--skin & mucous membranes
S. hominis--skin rich in apocrine glands
S. capitis--scalp, face, external ears
What is the primary importance of S. saprophyticus?
Urinary tract infections found almost exclusively in sexually active young women.
What conditions can S. epidermidis cause?
Endocarditis
Bacteremia
Urinary tract infections
Which infections usually occur after surgical procedures involving incisions through the skin?
S. epidermidis
S. hominis
S. capitis
Is S. aureus coagulase-positive or negative?
Coagulase positive
Which Staph. species are coagulase-negative
All except S. aureus
S. epidermidis
S. hominis
S. capitis
S. saprophyticus
How is a coagulase test performed?
A tube of plasma is inoculated with bacterium. If it remains a liquid, the test is negative. If it develops a lump or clots completely, it is postive.
Osteomyelitis is a __________ infection.
Staphylococcal
What is the primary origin of Staphylococcal bacteremia?
Bacteria that have escaped from an infection site or from colonized medical devices (catheters, shunts)
Enterotoxins in S. aureus are ______________.
Heat stable
95% of S. aureus have acquired genes for ____________.
Penicillinase
MRSA can carry multiple resistance to many antimicrobics. Name 6 of them.
Methicillin
Gentamicin
Cephalosporins
Tetracycline
Erthyromycin
Quinolones
HA-MRSA accounts for ______% of Staphylococcal infections.
80%
Recently there have been reports of S. aureus resistance to _____________.
Vancomycin
What is HA-MRSA?
MRSA contracted in hospital settings
What is CA-MRSA?
MRSA contracted outside the hospital (community contact) that has been implicated in fatal systemic diseases.
CA-MRSA is sensitive to a (wider/narrower) array of treatment options.
Wider
What is drug selection for staphyloccocal infections dependent on?
culture and sensitivity testing of staphylococcal isolates
Less resistant forms of S. aureus can be treated with what? (name 4 drugs)
Cephalexin
Sulpha drugs
Tetracyclines
Clindamycin
What specific drugs work on MRSA? (hint, there are 4)
Vancomycin
Teicoplanin
Linezolid
Daptomycin
For cases of VISA and VRSA, what is the last drug of choice?
Synercid (synthetic)
How are abscesses related to Staph infections treated?
They will not respond to therapy unless they are surgically perforated and cleared of pus and foreign bodies.
Systemic conditions related to staphylococcal infections include what?
Endocarditis
Septicemia
Osteomyelitis
Pneumonia
Toxemia
What is the required treatment for staph. related systemic infections?
Intensive, lengthy therapy by oral or injected drugs or a combination of the two. They usually respond slowly.
What are the 5 most significant strains in nosocomial infections?
MRSA
VRE
VRSA
VISA
DRSP
What does DRSP stand for?
Drug-resistant Staphylococcus aureus
What does VISA stand for?
Vancomycin intermediate Staphyloccus aureus
So far the rates of VRSA have been (high/low) and _______ cases have been reported.
low; 3
What are VISA infections named for?
Their primary drug resistance (Vancomycin)
Other than Vancomycin, what can VISA also be resistant to?
Cephalosporins
Macrolides
Fluoroquinolones
How is resistance acquired in VISA?
Conjugation, through transfer of resistance plasmids
What is a combination antibiotic designed to treat some types of VRE and stphylococcal infections?
Quinupristin/dalfopristin
What is Linezolid used for in regard to Staph infections?
It is NOT used for Staph infections. It is used for Group A and B streptococcal infections, pneumococcal pneumonia, and MRSA pneumonia
What has Daptomycin been approved for?
Skin infections caused by MRSA, VRE and certain streptococci
Which Spahyloccal species shows NO anaerobic growth?
Staphyloccus hominis
Of the Staph species that show anaerobic growth patterns, which produce urease?
S. epidermidis
S. saprophyticus
Is S. capitis anaerobic or aerobic?
Anaerobic
Streptococcus species can be further broken down into what groups?
17 different alphabetically named Lancefield groups based on cell wall carbohydrates displayed by each species (cell wall competence)
In regard to streptococcus, the Beta-hemolytic group consists of what Lancefield groups?
A, B, C, and some D
Which species belong to the Alpha-meolytic group?
S. pneumoniae and S. viridans
What is the main representative of Group A streptococcus?
Streptococcus pyogenes, a strict pathogen that inhabits the throat, nasopharynx, and occationally the skin of humans
What is the role of S. pyogenes in disease?
Due to the substantial array of surface antegens, toxins and enzymes it can generate.
Name 5 Cell surface antigens/virulence factors of Strep species.
C carbohydrates
Lipoteichoic acid
M protein
Capsule (Hyaluronic acid)
C5a protease
Which Strep species are human diseases most often connected with?
S. agalactiae
S. pneumoniae
S. pyogenes
Viridans Streptococci
Enterococcus faecalis
What is the difference between B-hemolysis and A-hemolysis?
A-hemolysis typically only partially lyses RBCs, while B-hemolysis completely lyses RBCs
What do C carboydrates do?
They are the basis for Lancefield groups. The protect the bacterium from being dissolved by the lysozyme defense of the host
What is Lipoteichoic acid bound to fimbriae do?
Promotes adherence in S. pyogenes
What is the significance of M protein?
Contribute to virulence by resisting phagocytosis and improving adherence
How many subgroups of M proteins exist?
About 80
What is the significance of the HA capsule?
It is formed by most S. pyogenes strains and is chemically indistinguishable from HA found in human tissues (does not provoke an immune response)
What does C5a protease do?
Interferes with the chemotactic response of neutrophils and stops the lysing of bacteria
What are streptolysins?
Hemolysins found in Group A streptococci that rapidly injure cells and tissues, including leukocytes, liver, and heart muscle
Name the two types of steptolysins
streptolysin O (SLO)
streptolysin S (SLS)
What is Erythrogenic (pyrogenic toxin)?
The key toxin in the development of scarlet fever. It is responsible for the bright red rash typical of scarlet fever and induces fever by acting upon the temperature regulatory center.
What are the only strains that can synthesis erythrogenic toxin?
Lysogenic strains of S. pyogenes that contain genes from a termperate bacteriophage
Name two groups of Streptococcus that have developed significant drug resistance.
Pneumococci
Enterococci
Name 5 characteristics of Streptococcus
1. Non-spore forming
2. Non-motile
3. Falcultative anaerobes
4. Peroxidase system (inactivates hydrogen peroxide)
5. Spherical shapes arranged in long beadlike chains
Where do many species of Atreptococcus exist as microbiota?
In the oral cavity
How do streptococcal toxins contribute to increased tissue injury?
By acting as superantigens
What is the likely mechanism behind the pathology of TSS and necrotizing fasciitis?
Stimulation of T lymphocytes that leads to overactive T cells which proliferate and produce a cascade of immune responses that release tumor necrosis factor and other cytokines.
What does Streptokinase do?
It is an enzyme that activates a pathway leading to digestion of fibrin clots (may play a role in invasion)
What does Hyaluronidase do?
Breaks down the binding substance in connective tissue and promotes spreading of the pathogen into tissues.
What is another name for DNase?
Streptodornase
How is infection of S. pyogenes tansmitted?
Direct contace, droplets, and occasionally fomites
T or F: Humans are not the only significant reservoir for S. pyogenes.
False. Humans ARE the only significant reservoir. About 5-15% of the population are subclinical carriers of virulent strains.
If not treated properly, S. pyogenes can give rise to what?
Various systemic infections and progressive sequelae
What drugs are S. pyogenes resistant to?
S. pyogenes are not usually drug resistant
What is the other name for Strep throat?
Streptococcal pharyngitis
Where does S. pharyngitis multiply?
Multiplies in the tonsils or pharyngeal mucous membranes.
What are the Pyogenic infections appearing after local invasion of the skin?
Pyoderma
Erysipelas
Name two infections that develop in the throat
Pharyngitis
Tonsillitis
What is Impetigo?
Pyoderma; marked by burning, itching papules that break and form highly contagious yellow crust
Erysipelas is (more/less) invasive than pyoderma
More; eventually spreads to the dermis and subcutaneous tissues
What are the most common infectious species belonging to the pyogenc cocci group?
Staphylococcus
Streptococcus
Enterococcus
Neisseria
What are the circumstances that predispose a person to infection by Staph species?
Poor hygiene
Poor nutrition
Tissue injury
Preexisting primary infection
Diabetes mellitus
Immunodeficiency states