Test 2 Flashcards
Characteristics of Staphylococcus
G+ ubiquitous-almost everyone will have a staph infection non-Motile do Not form Spores Facultative anaerobe produce Catalase most are Halotolerant (up to 9%) grow over Wide range of temperature (15-45 C)
What are the characteristics of Staphylococcus epidermidis
mostly opportunistic
often in implanted devices and joints
part of the normal flora
grows on Blood agar
What do we use to grow Staphylococcus aureus in the Lab
Blood Agar
Where is S. aureus found?
GI tract
urogenital tract
transient vaginal carriage
moist skin folds (problems with school and gyms)
Nasal carriage (is biggest problem-skin sheds, found on 25-50% adults and 60% of health care workers)
How is S. aureus transmitted by?
Direct Indirect -fomite Survive on surfaces for a long period of time (hours-months) depending on the amount of Nutrients and Moisture -Survives on clothing and linens
Name groups of infection for
Staphylococcus aureus?
- people with breaks in the skin ( follicles, bug bites, IV users, needles)
- people taking broad spectrum antibiotics (major resistance to S. aureus)
- people ingesting food containing enterotoxins
- elderly
- children
- immuno compromised people
- people undergone through surgery (stitches and sutures)
- pre-mature babies
What are the 3 Surface virulent factors that S. aureus have?
- capsule
- protein A
- peptidoglycan
How does the surface factor capsule work as a virulent factor for S. aureus?
the polysaccharide thick layer of the capsule
- provides Adhesion
- is Anti-phagocytic
- prevents from Drying out
- contains Multiple Serotypes
How does the surface factor protein A work as a virulent factor for S. aureus?
the protein A coats the surface of the cell
- acts as an adhesin (it needs a receptor to attach to the host)
- binds and disables IgG (delaying initial immune response-it extends time to allow high multiplication->causes a lot of damage)
How does the surface factor peptidoglycan work as a virulent factor for S. aureus?
- causes release of Cytokines (IL-1 pro-inflammatory)->drives immune response to cell-mediated avoiding phagocytosis
- endotoxin activity
- facilitates abscess formation
Name the different kinds of virulent factors that S. aureus has
- Surface factors
- Binding proteins
- Membrane damaging exotoxins
- Super-antigens
- Enzymes
What are binding proteins that serve as virulent factors for S. aureus?
- Fibronectin binding protein (FBP)
- allows adhesion & internalization to host tissue
- Clumping factor
- allows attachment to blood= it clots using platelets-> damages tissue
What are some of the characteristics of membrane damaging exotoxins for S. aureus?
- lyse PMNs->PMNs release lysosomal enxymes->tissue damage
- destroy cells: erythrocytes, hepatocytes, fibroblasts, platelets
what is the effect of alpha toxin of S. Aureus?
It damages host cell membrane by inserting into membrane->osmotic lysis
- major mediator of tissue damage
- Disrupts smooth muscle in vessels
- high levels leads to shock
What does the S. aureus beta toxin do?
- Sphingomyelinase C causes hydrolysis of membrane lipids
- It is highly hemolytic (RBC damage)
What is Sphingomyelinase C?
It is a Beta toxin (S. aureus)
It causes hydrolysis of membrane lipids
It is highly hemolytic
What are the 3 D’s of Delta toxin?
- causes high levels of Diarrhea (associated with food intoxication)
- act as a Detergent
- Dissolves cell membrane in a wide range of cell types
What are the characteristics of Gamma toxin in Staph. aureus?
-Lyses PMN’s and macrophages dodging the immune system
There are 2 separate proteins required for toxin to work:
-fast eluting protein
-slow eluting protein
What are leukocidin in Staph aureus?
They are Gamma toxins that damages WBC's (PMN's & macrophages) They dodge the immune system This toxin has to components: 1. F component- fast eluting protein 2. S component- slow eluting protein
Panton-Valentine Leukocidin (PVL)
- Lyses many types of WBC’s
- It is used as a marker to identify CA-MRSA strain
- It has a F & S component (protein subunits)
- It is related to severe skin and lung infections
What are the superantigens located on the same pathogenicity island?
- Toxic shock syndrome toxin 1 (TSST1)
- Enterotoxin
- Exfoliative toxin
What are the characteristics of TSST1?
- It binds directly to T cells without MHCII antigen presentation
- Toxin is expressed under conditions of high oxygen levels and neutral pH
- Toxin is related 100% of menstrual TSS and 75% of non-menstrual TSS cases
What is the toxin that is in the CDC list of bioterrorism agents (category B)?
Enterotoxin B of Staph. aureus
If aerosolized=major respiratory problem and shock
at minimum, it causes 2 weeks of incapacitation
at maximum, it is fatal
What are the characteristics of enterotoxin of Staph. aureus?
- Heat stable-survives boiling
- survives gastric acid
- most commonly implicated in food intoxication=emesis (vomiting & diarrhea
- enterotoxin B is potent (bioterrorism)
- many versions (up to 50% of strains produce at least one)
What are characteristics and the name of the toxin that produces Staphylococcal Scalded Skin Syndrome (SSSS)?
The Exfoliative toxin has 2 forms:
1. ETA: heat stable
2. ETB: heat labile
The exfoliative toxin binds to cells in the stratum granulosum of keratinized epidermis=disruption of junctions between stratum granulosum and spinosum
What are the enzymes that Staph. aureus uses as a virulent factor? What are their functions
- Hyaluronidase: hydrolysis of hyaluronic acid in host=damages connective tissue=facilitates spreading
- Coagulase: activates fibrinogen to fibrin=clotting is produced=abscess formation (protective from immune system)
- Catalase: breaks down hydrogen peroxide
- Lipase: hydrolysis of lipids and sebum from skin= essential for survival on skin= these are used as nutrients
- Penicillinase: greater than 90% of strain are resistant to B-lactam drugs. breaks down penicillin
Give some characteristics of folliculitis
-Minor infection in hair follicle
-It can come from a wound infection
-It is purulent
-Spontaneous resolution= no need of antibiotics, only drainage necessary
-single focus infection
Ex: stye: infection around the eye (easy to inoculate)
Give some characteristics of furuncle
- it can develop from a folliculitis= gets worse
- from sebaceous glands, sweat glands, and hair follicles
- Spontaneous resolution= no need of antibiotics (drainage necessary)
- single focus infection
Give some characteristics of a carbuncle
- It is several furuncles infections in the same area
- Antibiotics are necessary
- potential to be a systemic infection if it enters the blood
What are the symptoms and characteristics of SSSS (Staph Scalded Skin Syndrome)?
- Exfoliative toxin produces desquamation= erythema and cutaneous blisters
- skin is replaced after 7days
- Immunity to toxin
- no antibiotic therapy necessary (spontaneous resolution)
- common in children under 5 yrs old
What are the symptoms of TSS (toxic shock syndrome)?
- fever
- sore throat
- vomiting
- rash
- muscle pain
- diarrhea
- desquamation of palm and soles after 48 hours
What are some characteristics of TSS (toxic shock syndrome)?
- TSST1 is usually involved, or enterotoxin B & C
- can be associated with menstruation & the use of highly absorbent tampons
- disease progresses over 48 hours to cause desquamation of soles & palms widespread organ damage
- Staph. aureus needs to be present in vagina to onset syndrome
- it occurs after 5 days of menstruation
What are the symptoms of Staph. Food Intoxication?
Symptoms start in 1-5 hours after ingestion of toxin
-NO fever
-Emesis: vomiting
-Diarrhea
Symptoms last until toxin is clear out of the system
What is Staph. Food intoxication?
-Food poisoning is related to ingestion of contaminated food with toxins
& store and food/handling
-Toxins survive gastric acid enzymes, boiling, reheating is not effective
-It can last about 24 hrs
-Toxin needs to be clear out of the system
through the symptoms: emesis, vomiting, diarrhea
What are Staph. aureus Pneumonia characteristics?
Found in the nose
Infection comes from breathing strain from a distant site
Strain related to CA-MRSA
necrotizing pneumonia, virulent, aggressive=septicemia
What is osteomyelitis?
- It is an infection due to an open wound or bone fracture or spread of infection
- where osteocytes are internally infected
- it cause high fever and pain
- it is difficult to treat
- nanotechnology therapy of antibiotics is used at the site of the open bone injury
How is Staph. aureus bacteremia acquired?
- Usually through nosocomial infections through a skin lesion
- It can lead to endocarditis affecting the left atrium of the heart
- antibiotic therapy is necessary
What are the methods used to diagnose and differentiate Staph?
Culture
use coagulase and catalase test to differentiate other Staphs
-Antibiotic susceptibility test critical to check for resistance
How can CA-MRSA can be differentiate from HA-MRSA?
CA-MRSA has a specific PVL (panton-valentine leukocidin)
What is the name of the gene related to resistance in MRSA?
mecA gene-codes for a penicillin binding protein preventing B-lactam to bind
What is LRSA?
Linezolid Resistant Staph. aureus
-Some types are single point mutation
-Latest cases are plasmid mediated: plasmid confers resistance to other drugs
-some strains are resistant to vancomycin
-it might come from a staph that affects cows
-
What are the drugs used for serious Staph infections?
Vancomycin
Linezolid (Zyvox)
Daptomycin (Cubicin)
Ceftaroline (Teflaro)
Does Staph aureus require a low or high infectious dose?
High Infectious Dose
Can Staph aureus be part of a Biofilm?
Yes, but not usually
What does multifactorial Pathogenesis mean in Staph aureus?
Staph aureus express different virulent factors depending on the location
Do all strains of Staph aureus contain all virulence factors?
not all strains contain all virulence factors
Is there any immunity to Staph aureus?
- low immunity
- Re-infection is common
Do streptococcus form spores?
NO, it is no-spore forming
Is streptococcus motile?
No, it is non-motile
Is streptococcus G+ or G-?
G+
Is streptococcus Catalase + or Catalase -?
Catalase -
What kind of media is use to culture streptococcus?
- Enriched media-(blood, co-factors) streptococcus can be fastidious
- Blood agar is used to differentiate hemolysis
How do you differentiate alpha hemolysis from beta hemolysis?
alpha hemoplysis=partial hemolysis, green or brown
beta hemolysis= complete hemolysis
List the major pathogenic streptococcus species:
- S. pyogenes (pyogenic, group A) =GAS
- S. agalactiae (pyogenic, group B)
- S. pneumonia (pneumococcus)
- S. mutants group (viridian)
Name 2 species of bacteria that can survive well on surfaces or fomites:
S. aureus
S. pyogenes
Describe the colonization of GAS?
- Colonization of the upper respiratory tract of healthy people
- >5-10% of people - Colonization is transient (a month from now it can be gone)
- Colonization increases when competition is wiped out
- It requires High infectious dose
- Infection occurs when normal defenses have been penetrated
Name the virulence factors of GAS
- Surface factors
2. Extracellular products
Name the surface factors that GAS uses
- Capsule
- M protein
- LipoTeichoic acid (LTA)
- Protein F
How does the capsule of GAS work as a virulent factor?
-Capsule is made of hyaluronic acid.
-Hyaluroninc acid is found in connective tissue= evades immunity
or non-immunogenic
-antiphagocytic
Describe how M protein of GAS acts as a virulent factor
- structural similar to Myosin-evades immune response
- Molecular mimicry,
- Major antigenic variation=100+ types
- anti-phagocytic=buys more time
- interferes with alternate complement pathway
- facilitates invasion of epithelial tissues
What is the function of LipoTeichoic Acid (LTA) in GAS?
It serves as adhesin
Used to bind fibronectin in host tissue
What is the function of F protein of GAS?
The function serves as adhesin
It binds to epithelial tissues
What are the extracellular products that act as virulent factors for GAS?
- C5a peptidase
- Superantigens= Spe (Streptococcal Pyrogenic Exotoxin)
- Streptolysins
- Streptokinases
- DNases
- Hyaluridonase
What is the function of C5a peptidase?
-It destroys C5a complement protein= disables activation of complement
How does Spe (Streptococcal Pyrogenic Exotoxin) of GAS act as a virulent factor?
- There are 4 types of Spe(A, B, C, F) produced by different strains
- The superantigens produces clonal expansion of C8+T cells
- releases a cytokine storm=>inflammation=>shock
- > there is suppression of B cell expansion or humoral response use for bacterial infection
- Associated with TSS, scarlet fever, & necrotizing fascitis
What are streptolysins of GAS?
- They serve as hemolysins
- There are 2 types: S & O hemolysins
- Streptolysins S= non-immunogenic, lyses all types of blood cells, lysosomes, & phagocytes
- Streptolysins O= immunogenic, oxygen labile, lyses WBC’s, platelets, & other tissues
What are the function of the following virulence factors?:
- C5a peptidase
- Superantigens= Spe (Streptococcal Pyrogenic Exotoxin)
- Streptolysins
- Streptokinases
- DNases
- Hyaluridonase
- C5a peptidase=destroys C5a=deactivates complement cascade
- Spe= acts as Sags=evasion
- Streptolysin= hemolysins=B hemolysis
- Streptokinase= breaks down fibrin (dissolves clots)=spreading
- DNase= depolymerises DNA=spreading
- Hyaluronidase=spreading=hydrolysis of hyaluronic acid=damages connective tissue
What are the diseases cause by GAS? (8)
- Pharyngitis or tonsillitis
- Scarlet fever
- Skin infections
- Puerperal fever
- Necrotizing fasciitis
- Acute Rheumatic Fever (ARF)
- Glomerulonephritis
- Streptococcal Toxic Shock Syndrome
Give some characteristics of Pharyngitis?
also called tonsillitis, or strep throat
Incubation: 2-4 days
Transmission: via respiratory droplets (2-5 feet)
Symptoms: malaise, fever(102), sore throat, pustules
Treatment: necessary, if not self-resolving
What is the pathogen that causes Scarlet Fever?
GAS Streptococcus pyogenes group A
It is a developed from a Pharyngitis infection.
Strain contains Spe (Streptococcus pyorogenic exotoxin) acts as Sags
What are the main characteristics of impetigo?
- Superficial skin infection
- Transient skin colonization
- It forms pustules and crust
- problems with secondary infection of Staph. aureus
What is Erysipelas?
It is a dermal infection usually occurs on face
- may follow phayngitis
- Symptoms: major redness, edema, rash border demarcated, fever, swollen glands
- It can progress to Necrotizing fasciitis
What is cellulitis?
It is an acute skin infection that occurs deep in the tissue
- Symptoms: great inflammation, swelling, usually fever
- It can progress to necrotizing fasciitis
What is necrotizing fasciitis?
It can start as erysipelas or cellulitis
-damage of muscle and fat tissue
full expression of virulence factors
systemic infection (24-48hrs)=>shock, organ damage=death
What causes Puerperal infection or “childbed fever”?
GAS- it is acquired during childbirth due to hygiene procedures (hand washing)
- often leads to sepsis
- highest rate C-sections deliveries
How can you differentiate Staph from Strep?
Run a catalase test
Staph= +
Strep= -
Grow on agar=B-hemolysis of strep + other tests
sensitivity testing of Bacitracin all strep strains are susceptible
What is the difference between Staph TSS vs Strep TSS?
The symptoms are similar (hypotension, fever, rash, vomiting, diarrhea) with the exception that the Strep TSS presents necrotizing fasciitis.
-Tampons is related to the Staph infection
-HIV+, cancer, heart disease, alcoholic, diabetic people are related to Strep
Strep’s virulent factors are: M protein, prominent capsule, SpeA
Staph virulent factors is TSST1
What causes ARF (acute rheumatic fever)?
- manifests after 3 weeks of the above untreated Pharyngitis or scarlet fever
- Fever, damage to joints, vessels, valves
- Chronic progressive damage to heart valves=creation of antibodies against the molecular mimicry of M protein
- no need of prophylactic antibiotics prior to dental procedures
How do you develop glomerulonephritis?
It is a complication of previous infection/disease occurring after 1-6 weeks
- autoimmune disease
- can lead to progressive loss of renal function
What would you prescribe for a Strep infection?
Penicillin
or Cephalosporins if patient is allergic to penicillin
What would you prescribe for a Mixed infection of Strep and Staph?
Erythromycin
Oxacillin
Vancomycin
