RT Book, Section
A1 Washam, Matthew C.
A1 Connelly, Beverly L.
A2 Kline, Mark W.
SR Print(0)
ID 1182936701
T1 Staphylococcal Infections
T2 Rudolph's Pediatrics, 23e
YR 2018
FD 2018
PB McGraw-Hill Education
PP New York, NY
SN 9781259588594
LK accesspediatrics.mhmedical.com/content.aspx?aid=1182936701
RD 2024/04/20
AB Staphylococci  are  ubiquitous  inhabitants  of  the  skin  and  mucous  membranes  of  humans  and  other  mammals.  They  exist  in  a  commensal  relationship  until  a  breach  in  a  cutaneous  or  mucosal  barrier  permits  staphylococci  access  to  deeper  tissues  and  the  bloodstream  or  until  a  foreign  body  or  medical  device  provides  a  foothold.  The  production  of  coagulase,  an  enzyme  that  clots  plasma,  distinguishes  Staphylococcus  aureus  from  other  medically  important  staphylococci.  Those  that  do  not  produce  coagulase  are  grouped  collectively  as  coagulase-negative  staphylococci  (CoNS)  and  represent  the  most  common  resident  bacteria  of  humans.  All  staphylococci  are  nonmotile,  non–spore-forming,  facultative  anaerobic  bacteria.  In  gram-stained  specimens,  they  appear  as  gram-positive  cocci  in  clusters,  as  well  as  in  pairs  and  tetrads.  Peptidoglycans  and  lipoteichoic  acids  form  the  basic  cell  wall  structures  of  staphylococci,  and  most  exhibit  microcapsule  formation.  Colony  morphology  followed  by  selected  biochemical  reactions  allows  identification  of  pathogenic  staphylococci.  Typical  24-hour  S  aureus  colonies  are  larger,  yellow  pigmented,  and  surrounded  by  a  small  zone  of  hemolysis.  Colonies  of  Staphylococcus  epidermidis  are  typically  small,  white  or  beige,  and  approximately  1  to  2  mm  in  diameter  after  overnight  incubation.  Small-colony  variants  of  S  aureus,  important  in  some  persistent  infections,  may  be  missed  initially  because  of  their  pinpoint  size.  Staphylococcal  colonies  in  general  will  be  catalase-positive,  distinguishing  them  from  streptococci.