Gram Positive Cocci Flashcards by Melissa May

Staph common infections

wound (boils, carbunles, impetigo)
septicemia
UTI
pneumonia

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Staph virulence factors

toxins (enterotoxins, toxic shock syn., exfoliative toxin, cytolytic toxin)
enzymes (coagulase, protease, hyaluronidase, lipase)
Protein A (interferes w/ opsonization by binding Fc or immunoglobins)

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complications of Staph aureus toxins

enterotoxin A & B- food poisoning
Toxin 1- toxic shock syn., Super Antigen, and Cytokine release (IL-1, 2, 6; TNF)
exfoliative toxin- scalded skin syn. (infants)

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Toxic shock syn.

high fever, hypotension, shock, rash

TSST-1 (acts on vascular sys. causing inflam., fever, shock)``

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Staph. aureus identifying features

catalase +
uniform in size
coagulase positive
beta hemolytic
ferments mannitol
creamy buttery colony
DNAse +

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other coagulase negative Staph

S. epidermidis (UTI)
S. haemolyticus (wounds, UTI, endocarditis)
S. saphrophyticus (UTI)
S. lugdunensis (endocarditis, meningitis, joint infec., surgical wound infec.)
S. warneri/ S. capitis/S. simulans/S. schleiferi (endocarditis, wound infec., septicemia)

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Staph key test

catalase test (+ bubbles)
glucose fermentation (+ yellow)
Staph aureus vs. CNS= coagulase test

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Micrococcus

GPC in tetrads
M. luteus bright yellow-orange
oxidase +
bacitracin S
furazolindone R
lysostaphin R

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Streptococcus grouping

Lancefield: ABCDFG

non-lancefield: viridans, pneumoniae

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GAS (group a strep)

chains or pairs; very tiny
S. pyogenes
capsule
beta hemolytic
bacitracin A: S
pharyngitis, impetigo, pneumonia, wound infec.
PYR +

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GBS (group b strep) characteristics

chains, pairs
S. agalactiae
beta hemolytic
neonatal meningitis
CAMP test + (arrow head hemolysis)
Na hippurate +

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Group C, F, G strep

C, G beta hemolytic
C, G cause human disease
pharyngitis
normal oral, GI and vaginal flora

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group D strep & Enterococcus

D carbo in wall
grp D: bile esculin + , no growth 6.5%NaCl, PYR -
Entero: bile esculin +, grow in 6.5% NaCl, PYR +
alpha/gamma hemolysis

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Step pneumoniae

GPC pairs, lancet shaped
capsule
alpha hemolytic
optochin S
Na deoxycholate +

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viridans Strep

oral, vaginal, GI normal flora
endocarditis, meningitis, dental caries
6 grps
small cocci may b in chains

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other strep like orgainisms

Aerococcus, Gemella, Leuconostoc
rarely cause infec.
facultative anaerobes
A. viridans & A. urinae clusters and tetrads
viridans alpha hemo., PYR +, LAP -
urinae alpha hemo., PYR -, LAP +
Gemella catalase -, PYR -, LAP +, vancomycin R

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S. epidermidis

Normal skin flora

Path: community acquired infec/contamination, prostectic valve endocarditis, septicemia in immonocompromised

S. saprophyticus causes…

UTIs

S. lugdensis

Community/hospital acquired infec.
Most virulent contain mecA gene which codes oxacillin resistance
Endocarditis has high mortality rate

MRSA

Methicillin resistant staph aureus

Resistant to penicillin, oxacillin, and nafacilin

CA-MRSA

Community associated methicillin resistant staph aureus

VRSA

Vancomycin resistant staph aureus

Streptococcaceae

Streptococcus and Enterococcus
Negative catalase
Aerotolerant anaerobes
Capnoplilic

Capnophilic

Require increased CO2 to grow

Strep etc. Exotoxins

Hemolysins alpha and beta

Pyogenic Strep

``` (pus forming) S. pyogenes S. agalctaie S. dysgalactaie subsp. equisimilis S. anginosus ```

GAS infections

``` Bacterial pharyngitis Impetigo, cellulitis, scarlet fever Necrotizing fasciitis Toxic shock syndrome Post streptococcal sequelae ```

Complications of GAS

Rheumatic fever | Acute glomerulonephritis

Strep agalctiae

GBS Capsule GBS disease

GBS disease

Neonatal Early onset: under 7 days old- vertical transmission, 80% of cases, mortality rate high Late onset: 1wk-3mons after birth, meningitis, not usually vertical transmission

Group c and d strep

Beta hemolytic S. dysgalactaie subsp equisimilis (large colony) S. anginosus (small colony) S. equi subsp zooepidemicus (rare in humans- animal pathogen)

S. pneumoniae infections

Pneumonia, sinusitis, otitis media in kids <3, bacteremia, meningitis Spread through respiratory droplets Secondary infec.

S. pneumoniae vaccine

``` Pneumococcal vaccine (pcv): 13 serotypes used- polysaccharides conj. to diltheria {children starting at 2 mons} PPSV23- 23 polysaccharides {adults 65+} ```

S. pneumoniae morphology

``` gpc in pairs More oval lancet shaped Checked shaped colonies on plates Alpha hemolytic Auto lyses so hard to keep alive Optochin (S) & bile solubility (+) key tests ```

S. agalctiae morphology

Greyish white colonies on plates Beta hemolytic CAMP and hippurate useful tests

S. pyogenes morphology

Small transparent colonies Beta hemolytic GPC in short chains Bacitracin (S) and PYR (+) key tests

Viridians Streptococci

``` Normal Flora of resp.tract/female genital tract/GI tract S. mitis grp S. mutans grp S. salivarius grp S. bovis grp S. anginosus grp ```

Viridans Streptococci morphology

Viridans (green)- alpha hemolytic mostly Fastidious Pyr (-), lap (+) key tests Look like strep on plates

Enterococcus

Normal Flora intestinal tract E. faecalis E. faecium

Enterococcus infection

Noscomial infections: UTI Bacteremia

VRE

Vancomycin resistant Enterococcus Resistance to aminoglycosides, beta lactams, glycopeptides, vancomycin

Aerococcus

Airborne, opportunistic | Bacteremia, UTI in immunocompromised