Aerobic gram positive cocci

Question 1

streptococcus pyogenes

Answer 1

G+ cocci in chains, beta hemolytic on blood agar
GAS carb, type specific protein M
numerous toxins, adhesins, antiphago compts
ID: Catalase negative, bactiracin sensitive, group A ag

Disease: pharyngitis, scarlet fever, pyoderma, erypsipelas, cellulitis necrtizing fascilitis, rheumatic heart disease, acute glomerlonephritis, TSS

Question 2

strep agalactiae

Answer 2

G+ cocci in chains, beta hemolytic
GBS carb, type specific antiphago capsular polysacch.
ID: catalase neg, CAMP positive, Group B ag

Disease: meningitis newborn, early onset neonatal disease, late onset neonatal disease, infection in adults is various and disseminated

Question 3

VIridans streptococci

Answer 3

G+ cocci in chains, alpha hemolytic
antigenic typing- no Lancefield carb ag
ID: must diff. from alpha hemolytic S. pneumonia, catalase -, optochin resistant
many species: S. mitts, S. mutans, S. salivaris

Diseases: Endocarditis, bacteremia in neutropenic patients, dental caries

Question 4

Streptococcus pneumoniae

Answer 4

Lancet-shaped, G+ cocci in pairs, alpha hemo
Ag typing- antiphago capsular polysacch
ID: diff. from viridans streptococci
Vaccine: capsular polysacch. or CPS- protein congugate

Diseases: pneumonia, meningitis, bacteremia, sinusitis and otitis media, sickle cell disease is risk factor

Question 5

Enterococci

Answer 5

G+ cocci
Ag typing- Group D cell wall polysacch
E. faecalis and E. faecium most impt.
highly resistant to Abios, esp. vancomycin and environmental stress

Diseases: UTI, wound (esp. intra abdominal), bacteremia and endocarditis,

Question 6

Staphylococcus aureus

Answer 6

G+ cocci in clusters, catalase positive, COAGULASE +, protein A on surface, no capsule
adhesive and antiphago, toxins, enzymes
MRSA- altered PBP (PBP2’) encoded by mecA gene

D: impetigo, folliculitis, furuncles/boils, carbuncles, bacteremia, endocarditis, osteomyelitis, septic arthritis, pneumo, empyema, brain abscess, food poisoning, TSS, scalded skin syndrome

Question 7

Coagulase- negative staphylococci

Answer 7

G+ cocci, catalase +, coag (-), extracellular polysacch. contributes to biofilm
primary species: S. epidermidis

D: endocarditis, catheter and shunt infections, UTI, S. saprophyticus- UTI in young sexually active females