Gram positive coccus

Question 1

What are the 3 GPC’s that are medically important to us

Answer 1

1. Staphylococcus
2. Streptococcus
3. Enterococcus

Question 2

What test can be used to tell the difference between staphylococcus and streptococcus/enterococcus

Answer 2

Catalase

Staph= (+) catalase

Strep/entero= (-) catalase

Question 3

What test can used to tell the difference between staphylococcus aures and other staphylococcus species

Answer 3

Coagulase

Staph aureus= (+) coagulase

Other staph species= (-) coagulase

Question 4

Describe Staphylococcus aureus in terms of morphology and virulence factors

Answer 4

Morphology = GPC in clusters w/ large yellowish beta hemolytic colonies

Virulence= Toxins, invasive enzymes (coagulase, proteases…), and adhesive molecules

Question 5

True or False most Staphylococcus aureus is resistant to beta lactams

Answer 5

True, ~85% of staph aureus contain beta lactamase

also can have MRSA, VRSA, and MDRSA

Question 6

Where are the genes related to the pathogenicity of Staphylococcus aureus located

Answer 6

plasmids mostly

or lysogenized viral genes to a less extent

Question 7

What illnesses can Staphylococcus aureus cause

Answer 7

Skin infections

• folliculitis
• furuncles=boils
• cellulitis
• impetigo =small blisters w/ thin crust
• abscesses
• scalded skin syndrome=from exoliatin toxin, no bacteria in bullae

Food poisoning

• from preformed toxin
• onset 1-6 hrs of ingestion
• often seen in processed meats, salads, and creamy desserts

Toxic shock syndrome

• toxin (super antigen) mediated
• associated w/ tampoms

Endocarditis

Bacteremia

PNA=low frequency

Question 8

True of False Staphylococcus aureus is pyogenic

Answer 8

True along w/ Group A Streptococcus A’s

Question 9

Describe Staphylococcus epidermidis in terms of morphology and major illnesses associated w/ the microbe

Answer 9

• Morphology= GPC in clusters, coagluase negative

- Illness= normal microbiota (often contaminate in culture) , can cause bacteremia and endocarditis in ICU patients

Question 10

Describe Staphyloococcus saprophyticus in terms of morphology, and major illnesses associated w/ the microbe

Answer 10

• Morphology= GPC in clusters, coagulase negative

- Illness= 2nd most common cause of UTI in women of child bearing age

Question 11

Describe Streptococcus pyogenes in terms of morphology, virulence factors, and biochem identification

Answer 11

• Morphology= GPC’s in chains, Group A beta hemolytic ,coagulase and catalase negative
• Virulence factors= Capsule, toxin, numerous invasive enzymes
• Culture or PCR are standard for ID \, throat swap has low sensitivity

Question 12

True or False susceptibility test are needed for Streptococcus pyogenes

Answer 12

False, usually not needed

Question 13

What illnesses can Streptococcus pyogenes cause

Answer 13

Skin infections

• impetigo
• cellulitis
• necrotizing fasciitis
• scarlet fever= erythrogenic toxin related

Streptococcal Toxic Shock Syndrome

Acute exudative pharyngitis

Post streptococcal complications

• Rheumatic fever
• Acute glomerulonephritis

Question 14

What population predominately gets acute exudative pharyngitis from streptococcus pyogenes

Answer 14

School aged children in colder months

Question 15

What 2 microbes cause 90% of skin infections like cellulitis and impetigo

Answer 15

Staph aureus and strep pyogenes

Question 16

Describe Group B Streptococcus in terms of major illnesses associated w/ the microbe

Answer 16

meningitis in neonates from inoculation from vagina

that is why we screen women @ 35 weeks of pregnancy

Question 17

Describe Streptococcus pnuemoniae in terms of morphology, virulence factors and major illnesses associated w/ the microbe

Answer 17

Morphology= GPC’s in PAIRS, mucoid, alpha hemolytic, coagulase and catalase negative

Virulence= Capsule

Illness= normal microbe in upper respiratory tract in 30-60% population so illness is caused by translocation of these

• PNA=#1 cause
• Sinusitis
• Otis media
• Meningitis= children over 10

Question 18

Describe Enterococcus faecalis in terms of morphology, and major illnesses associated w/ the microbe, and Abx resistance

Answer 18

Morphology= GPC’s in chains, catalase and coagulase negative

Frequent nosocomial infection= surgical wounds and UTIs

MDR and VRE