- Staphylococcus epidermis: Staphylococcus epidermis, also known as S.
epidermis, is the frequent cause of urinary tract infections in the elderly
and also causes subacute bacterial endocarditis, which is a chronic in-
fection of the endocardium (a thin layer of connective tissue that lines
the chambers of the heart) and heart valves. - Staphylococcus saprophyticus. Staphylococcus saprophyticus, also
known as S. saprophyticus, causes urinary tract infections, usually in
adolescent girls. - Streptococcus. Streptococcus bacteria appear as a single, paired or chained
spherical gram-positive bacteria. Streptococci do not use oxygen, though
most are aerotolerant. Few may be obligately anarobic. Infections caused
by the Streptococcus bacteria are generally referred to as a strepinfection.
Microbiologists classify Streptococcus bacteria in three ways. - The type of hemolysis (destruction) of red blood cells caused by the
Streptococcus bacteria. There are three types characterized by: - Alpha-hemolytic group. Incomplete lysis (destruction of the cell)
within green pigment surrounding the colony. - Beta-hemolytic group. Total lysis and a clear area around the colony.
- Gamma-hemolytic group. Absence of lysis. This group is of no clin-
cal importance. - The Lance Field classification. There are four groups:
- Group A Streptococci. Characterized by Streptococcus pyogenesand
secrete of erthrogenic exotoxins responsible for scarlet fever. - Group B Streptococci. Characterized by Streptococcus agalactiae,
which is part of normal oral and vaginal flora and causes urogenital
(urinary and reproductive systems) infections in females. - Group C Streptococci. Causes animal diseases.
- Group D Streptococci. Characterized by Streptococcus faecalis, which
is a normal part of oral and intestinal flora. Diseases of S. faecalisare
endocarditis, urinary tract infections and septicemia (blood poisoning). - Ungrouped Streptococci. There are two kinds:
- Viridans streptococci.Characterized by Streptococcus viridansand
Streptococcus salvarius,which causes subacute bacterial endocardi-
tis, and Streptococcus mutanswhich causes a biofilm called plague
resulting in tooth decay. - Pneumococcal streptococci. Characterized by Streptococcus pneu-
moniaewhich causes lobar pneumonia and otitis media (middle ear
infection).
CHAPTER 10 The Prokaryotes^161