Staph & Strep Flashcards
Staph organism, growth characteristics
Gram positive cocci in clusters
Catalase +, salt tolerant up to 9%NaCl
Staph differentiation
(?)
Hemolysis (S. aureus)
Coagulase + S.aureus) - associated with virulence
Coagulase negative staph
CNS = S. epidermidis, S. saprophyticus
*opportunists
S. aureus - some presentations due mainly to ________.
What is the classic S. aureus lesion?
growth of bacteria
Furuncle (walled off by coagulase)
Staph localized to hair follicles
folliculitis
S. aureus is a frequent complication of ________ via invasion of sebacious glands.
What is the PRIMARY cause of this?
complication of acne
Primary cause = Propionibacterium acnes
_______ is the most common cause of _______, which is an infection of the superficial epidermis (most common bacterial skin disease)
Symptoms mainly due to….
Staph aureus causes non-bullous impetigo
*Due to immune response
Deep incisional staph infections often present as
cellulitis
(20% from staph aureus, 14% from coaulase negative staph)
Frequent complication of staph bacteremia
How do you detect?
How do you treat?
Endocarditis
Echocardiography to detect
Gentamycin to treat
Some staph presentations are due to bacterial growth, while others are due to _____________
Exotoxin release
Bullous exfoliation a.k.a. _________
What are the symptoms/presentation? Who is affected?
Staph Scalded Skin Syndrome (SSSS)
- Intraepidermal splitting of top layers
- Mostly in children (better prognosis than adults, who have bacteremia)
Bullous impetigo symptoms and who it affects
Fluid filled blisters within epidermis (Exfoliative toxin causes)
Almost always in kids under 2 years old
Toxic shock syndrome presentation
- abrupt fever
- rash with desquamation
- hypotension
- multisystem involvement
- DIC
Toxic shock syndrome underlying pathology
caused by immune reaction to TSST
Food poisioning Sx from Staph
What particular type of cell is involved?
nausea, vomit, diarrhea, NO FEVER
QUICK (4-24 hours)
Treg cells involved in limiting inflammatory response?
Staph epidermidis associated with…
implanted devices (biofilm formation)
___ can also cause surgical implant infections, but…
Staph aureus
but Epidermidis doesn’t cause the diseases that S. aureus causes
Staph epidermidis is native flora in ___% of patients
100%
Staph saprophyticus is associated with ____ because of ________.
Most UTIs are caused by…
UTI because of specific adhesin for UT epithelium
UPEC E. coli
Menstrual TSS associated with…
use of retained tampons
Staph is difficult to treat beacuse of…
rapid MDR
ex. MRSA (mecA on SCC cassette)
Staph virulence factors (antigens)
- Peptidoglycan (inflammatory PAMP)
- Teichoic acids (check patients for alpha-TA antibodies!)
- Protein A (binds Fc)
- Iron-Binding Proteins
Other Staph virulence factors (7)
- Coagulase - (wall off infctn)
- Hyaluronidase, Staphylokinase (tissue invasion)
- Hemolysins (Alpha toxin (RBC) and Beta Toxin (sphingomyelin), leukocidin (WBC)
- Exfoliative toxin - SSSS, bullous impetigo
- TSST-1 - (superantigen, induces IL-1/TNF)
- Enterotoxin (also superantigens…food poisoning)
- **Quorum Sensing **(turns on biofilm genes)
What is the big virulence factor that is associated with mrsa?
Panton-Valentine Leukocidin
Forms pores, causes leukopenia
Superantigens are located on ____ and spread via ______
PAI’s
transduction
Four control measures that have helped deal with MRSA
Better hand hygeine
catheter routes targeted
MRSA-specific detection and decolonization
*Isolation of carriers and Daily chlorhexadine wash
Recurrent furuncles from staph treated by…
drainage and tetracycline
(uncomplicated one may only need draining)
MRSA Tx
Bactrim, clindamycin, doy, linezolid
Severe = Vancomycin
Staph saprophyticus Tx
quinolones, bactrim, augmentin
Staph optomized treatment requires…
susceptibility testing
broth dilution, E test, or Kirby Bauer
Antibiotic resistance spreads via
R plasmids (conjugation)
Strep organism and appearance
Gram positive cocci
- may be oval
- in chains or pairs
Strep capsule
-growth characteristics/requirements
capsule – hyaluronic acid (group A) or polysaccharide
-fastidious growth, facultative, but prefers 5-10% CO2
__% of patients are carriers for beta hemolytic strep
10%
Strep classification is based on what four things?
- Hemolysis (alpha, beta, or gamma/none)
- Lancefield serotyping (specific amino-sugar and teichoic acid cell wall antigens)
- Biochemistry (AB resistance, NaCl tolerance, bile esculin)
- Colonization patterns (Entero, Lacto, Pneumo-cocci)
Strep pyogenes classification
- Group A
- Beta hemolytic
- Bacitracin-sensitive
S. pyogenes causes ____ infections. Six examples?
Invasive infections
- Human erysipelas (dermis and SubQ)
- Puerperal fever (postpartum)
- Surgical sepsis
- Scarlet Fever (bacteremia - characteristic rash and strawberry tongue)
- Streptococcal toxic shock-like syndrome (TSLT superantigen)
- Necrotizing fasciitis (deep fascia cellulitis)
Scarlet fever rash appearance
Ddx from which other rash?
Diffuse upper body rash
Ddx from measles rash (top-down)
Scarlet fever usually starts as…
Pharyngitis
Necrotizing fasciitis may be caused by ___ or ____
TSST (staph) or TSLT (strep)
Two other invasive infections from s. pyogenes
- PNA
- Bacteremia
*both are serious infections
Two local infections from s. pyogenes
Pharyngitis (fever, anterior lymphadenopathy)
Impetigo (non-bullous)
Two post-infection sequellae (due to ____ )
d/t immune mimicry (immune complexes)
Acute Rheumatic Fever - valve damage
Acute glomerulonephritis - blood/protein in urine
Animal carriers of s. pyogenes
None. Only humans (10-20% carrier rate)
Strep throat spread via ____, common during ____, and usual age of onset.
Spread in nasal droplets and by contact
Common in winter
Kids 6-13
Strep impetigo most common during ____, spread by _____, and age of onset.
- Common in summer
- Spread by contact, contiguity, and fomites
- Preschool kids
Strep rheumatic fever occurs how long after disseminated strep infection?
Condition is more likely to be brought on by…
1-4 weeks
The second infection
What are the virulence factors of Strep pyogenes?
- M protein
- Hyaluronic acid capsule
- C substance
- C5a peptidase
- streptokinase/streptodornase
- hyaluronidase
- exotoxins
- hemolysins
Strep M protein is associated with…
thrumatic sequellae
Strep’s Hyaluronic acid capsule function
mimics host, antiphagocytic
What is C substance?
capsular polysaccharide
*enhances invasiveness
- Streptokinase function
- Streptodornase function
- dissolves fibrin clots
- DNAse
Strep “spreading factor”
hyaluronidase
Strep. pyogenes exotoxins (types, function, and associated with…)
A, B, C
pyrogenic
Associated with scarlet fever, strep TSS
S. pyogenes Hemolysins - O2 sensitivity
Streptolysin O = O2 sensitive
Streptolysin S = Not
Control measures for S. pyogenes
pasturization of milk
isolate carriers from susceptible patients (not quarantine)
Group A strep are sensitive to…
PenG
How do you treat ARF/AGN
anti-inflammatory drugs and rest
Rheumatic fever management?
Long term PenG prophylaxis (prevents recurrence)
S. agalactiae classification
(group, hemolysis, cAMP, bacitracin)
- Group B
- Beta hemolytic
- cAMP positive
- Bacitracin-resistant
S. agalactiae typed by…
its polysaccharide capsule
Acute S. agalactiae diseases in infants and elderly
- Neonatal Sepsis (and PNA 1-7 days post-partum) – most common cause of neonatal sepsis in US
- Neonatal Meningitis (1 week - 3 months)
- Respiratory Distress Syndrome “RDS” (bacteremia, soft tissue infections)
S. agalactiae spread when?
From infected mom to baby during delivery (chance of vertical transmission is 50%)
Group B strep control
Screen before delivery (36 weeks)
How to treat if there is a positive GBS screen in pregnant mom?
Do we ever use these prophylactically?
Intrapartum **Ceph3 **or **Ampicillin + Streptomycin **
Yes. Give prophylactically if baby is premature or if there was no GBS screening done
Enterococci and S. bovis are ___ strep
Group D
GDS hemolysis
Growth characteristics in NaCl and Bile esculin
non hemolytic, but sometimes alpha
Growth in 6.5% NaCl, bile-esculin growth
GDS members
E. faecalis
E. faecium
Strep bovis
GDS is a common ____ infection, which causes what conditions?
nosocomial infeciton
Bacteremia, endocarditis, UTI
- GDS transmitted mostly via…
- What is the portal of entry?
- hospital workers’ hands
- Enter GI tract and bacteremia from colon lesions
Big problem with Group D strep
MDR
Intrinsic resistance of enterococci to ______
…but OK for ____
GDS resistant to ____ because it can steal ____ from host
resistant to B-lactams
OK for S. bovis
SxT resistant because it can use host’s folate
Antibiotic Tx for GDS
Preferred Tx for S. bovis?
Tx for Enterococcus? Problems?
- GDS = High-dose Penicillin + aminoglycoside
- Bovis = Penicillin or ceftriaxone
- Enterococcus = Vancomycin (but vanR is a problem)
80% of infective endocarditis are caused by…
Staph or strep infections
Indications for antibiotic prophylaxis against endocarditis has been restricted to…
invasive dental procedures in patients with:
- a prosthetic valve
- history of endocarditis
- unrepaired cyanotic congenital heart disease
Viridans strep hemolysis, and growth resistances
alpha hemolytic
optochin resistant
ox-bile resistant
most common viridans strep infection?
Sx?
sub-acute bacterial endocarditis
(especially after tooth extraction or dental surgery)
Sx = heart murmur, weakness, embolism, anemia
VIrians strep is normal flora of
URT
Viridans strep prophylaxis and Tx
prophylactic AB before and after oral surgery
Long term Penicillin or Vancomycin
Better Strep viridans outcome with…
surgical management of endocarditis
Pneumococci hemolysis and growth characteristics
alpha hemolytic
optochin sensitive
ox bile sensitive
Pneumococci appearance and structure (capsule)
diplococci with large polysaccharide capsule
Bad types of pneumococcus
- 3
- 19A
- 23F
Test for pneumococci
Quellung reaction
- polyvalent antiserum against capsule
- added to sputum
- if pneumococcus is present the capsule swells
- visualize with negative stain
S. pneumoniae presentation
- sudden onset lobar PNA
- Fever, chills, pain, mental status change
- HIGH leukocytes
Patterns of PNA
- Lobar =** **(consolidation of one/more lobe, bronchi often OPEN – bronchogram Xray)
- BronchoPNA = peribronchial thickening, alveolar consolidation
- Interstitial = inflammation/edema of interstitial tissue of the lung, fibrosis
Four routes of acquisition of pneumococcus
Community
Hospital
Ventilator-associated
Aspiration
Causes of Aytpical bacterial PNA
- Mycoplasma pneumoniae
- Chlamydia pneumoniae + psittaci
- Legionella pneumophila
- Coxiella burnetti
- Bordetella pertussis
60% of bacterial Community-acquired PNA is caused by _____
pneumococcal disease
pneumococcus is the number 2 cause of _____
and the number one cause of _____
2 cause of Otitis Media
Risk factors for pneumococcus infection
mucus accumulation
alcohol/drug use
general debility
Pneumococcus pathogenesis based on… (3)
colonization of tissues
polysaccharide capsule
debilitated host
**IgA protease is of limited virulence
Pneumococcal vax
23 valent capsule vaccine
PPSV23
for ADULTS (especially at-risk)
