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COAGULASE NEGATIVE STAPHYLOCOCCI
These cocci are distinguished from
Staphylococcus aureus by their negative reaction in the coagulase
test. Being present on the skin, in the mouth and in dust, they are
commonly encountered as commensals or contaminants in specimen from
skin lesions, wounds, burns, throat, sputum and faeces. The
coagulase-negative staphylococci of medical importance are the
Staphylococcus epidermidis and Staphylococcus saprophyticus. They
are opportunistic pathogens and can cause infection. Staphylococcus
epidermidis may cause peritonitis in patients on peritoneal
dialysis, chronic septicaemia or endocarditis in patients having
heart surgery, bacteraemic infection in patients treated with an
indwelling venous catheter left in place for more than 48 hours and
septicaemia in immuno-suppressed patients. Also Staphylococcus
saprophyticus is an important cause of urinary tract infections in
women of child-bearing age.
Novobiocin is used to differentiate
between these two species, where Staphylococcus epidermidis is
novobiocin sensitive and Staphylococcus saprophyticus is novobiocin
resistant.
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