RT Book, Section
A1 Hooper, David C.
A2 Jameson, J. Larry
A2 Fauci, Anthony S.
A2 Kasper, Dennis L.
A2 Hauser, Stephen L.
A2 Longo, Dan L.
A2 Loscalzo, Joseph
SR Print(0)
ID 1155965990
T1 Bacterial Resistance to Antimicrobial Agents
T2 Harrison's Principles of Internal Medicine, 20e
YR 2018
FD 2018
PB McGraw-Hill Education
PP New York, NY
SN 9781259644016
LK accesspharmacy.mhmedical.com/content.aspx?aid=1155965990
RD 2024/04/20
AB The  action  of  antimicrobial  agents  on  a  range  of  targets  within  the  bacterial  cell  can  result  in  inhibition  of  bacterial  growth  or  in  killing  of  the  bacterial  cell  (Chap.  139).  Reduction  in  or  loss  of  an  agent’s  antibacterial  effect  is  referred  to  as  resistance,  and  the  properties  of  or  alterations  in  the  bacterium  that  result  in  reduced  antimicrobial  activity  are  termed  resistance  mechanisms.  Bacteria  can  be  resistant  to  single  or  multiple  antimicrobials,  as  detailed  in  the  sections  that  follow.  The  occurrence  and  magnitude  of  resistance  are  often  assessed  in  clinical  microbiology  laboratories  by  measurement  of  the  lowest  drug  concentration  that  inhibits  growth  of  a  bacterium  (minimal  inhibitory  concentration,  or  MIC)  with  a  standardized  inoculum  and  growth  conditions.  MIC  values  are  generally  interpreted  as  representing  bacterial  susceptibility,  intermediate  susceptibility,  or  resistance;  the  interpretation  is  based  on  correlations  of  the  MIC  values  with  the  pharmacokinetics  and  delivery  of  a  drug  to  the  site  of  infection  in  the  body  as  well  as  with  data  from  clinical  trials.  Thus,  a  clinical  laboratory  result  of  “susceptible”  for  a  bacterium  predicts  a  likely  clinical  response  to  an  appropriately  dosed  antimicrobial  drug  by  a  patient  infected  with  that  organism,  whereas  a  result  of  “resistant”  predicts  poor  or  no  clinical  response  to  that  drug.  Breakpoint  MIC  values  for  categorization  of  bacteria  as  susceptible,  intermediate,  or  resistant  are  generally  developed  by  regulatory  and  advisory  groups  and  are  often  based  on  the  distribution  of  MIC  values  from  a  large  collection  of  recent  clinical  bacterial  isolates.  Research  studies  on  the  mechanisms  and  epidemiology  of  resistance  may  in  some  cases  use  different  and  less  rigid  definitions  of  resistance  based  on  determination  of  a  reproducible  increase  in  an  MIC  value  relative  to  a  baseline  reference  MIC,  independent  of  clinical  breakpoints.