Quick Review Cards for Medical Laboratory Science

Streptococci/Enterococcicontinued Clinical Microbiology Review 163

ORGANISM PATHOGENICITY GRAM STAIN COLONIES ON SBA KEY CHARACTERISTICS OTHER

Streptococcus
pneumoniae

Viridans streptococci

No Lancefield group.

>80 serotypes based

on capsular antigens.

Football-shaped

(lancet-shaped)

GPC. Usually in

pairs. May be

single or in short

chains. Frequently

encapsulated

GPC in chains

Round, translucent,

glistening, dome

shaped when

young. Central

depression with

age (umbilicate)

due to autolysis.

Alpha hemolytic.

Encapsulated

strains are mucoid

Usually alpha he-

molytic, but may be

beta hemolytic or

nonhemolytic.

Normal in upper

respiratory tract

of some. Most

common cause

of community-

acquired pneumo-

nia. Major cause

of otitis media,

meningitis in

adults. Infects

sinuses, eyes

Normal in oral,

respiratory, GI mu-

cosa. Opportunistic

pathogens. Fre-

quent cause of

subacute bacterial

endocarditis.

Gingivitis & dental

caries (cavities)

Bile solubility pos.

Sensitive to optochin

Resistant to optochin.

Bile solubility neg

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