Extended-spectrum β-lactamases: Difference between revisions

Revision as of 09:06, 12 September 2020

Background

Extended-spectrum β-lactamases (ESBLs) are generally defined as β-lactamases that hydrolyze penicillins, first-, second-, and third-generation cephalosporins, and aztreonam, but not cephamycins or carbapenems
This definition excludes AmpC (which hydrolyze cephamycins) and carbapenemases (which hydrolyze carbapenems)
Includes primarily Ambler Class A β-lactamases

Identification

ESBLs are screened for by identifying organisms with increased MICs to one or more third-generation cephalosporin or monobactam
- CLSI uses cefpodoxime, ceftazidime, aztreonam, cefotaxime, or ceftriaxone

Screening for ESBL production
Bacterium	Antibiotic	Disc Diffusion	Broth Microdilution
Klebsiella pneumoniae, Klebsiella oxytoca, and Escherichia coli	cefpodoxime	≤17 mm	≥8 μg/mL
	ceftazidime	≤22 mm	≥2 μg/mL
	aztreonam	≤27 mm	≥2 μg/mL
	cefotaxime	≤27 mm	≥2 μg/mL
	ceftriaxone	≤25 mm	≥2 μg/mL
Proteus mirabilis	cefpodoxime	≤22 mm	≥2 μg/mL
	ceftazidime	≤22 mm	≥2 μg/mL
	cefotaxime	≤27 mm	≥2 μg/mL

For organisms that screen positive, they are then tested for third-generation cephalosporin resistance that is attenuated by clavulanic acid
- CLSI uses either ceftazidime or cefotaxime, with and without clavulanic acid
- An increase in the zone of ≥5 mm is diagnostic of ESBL production

@@ Line 1: / Line 1: @@
+== Background ==
-#REDIRECT [[Β-lactamases]]
+* Extended-spectrum β-lactamases (ESBLs) are generally defined as [[β-lactamases]] that hydrolyze [[penicillins]], first-, second-, and third-generation [[cephalosporins]], and [[aztreonam]], but not [[cephamycins]] or [[carbapenems]]
+* This definition excludes AmpC (which hydrolyze [[cephamycins]]) and carbapenemases (which hydrolyze [[carbapenems]])
+* Includes primarily Ambler Class A β-lactamases
+=== Identification ===
+* ESBLs are screened for by identifying organisms with increased MICs to one or more third-generation [[Cephalosporins|cephalosporin]] or [[Monobactams|monobactam]]
+** CLSI uses [[cefpodoxime]], [[ceftazidime]], [[aztreonam]], [[cefotaxime]], or [[ceftriaxone]]
+{| class="wikitable"
+|+Screening for ESBL production
+!Bacterium
+!Antibiotic
+!Disc Diffusion
+!Broth Microdilution
+|-
+| rowspan="5" |[[Klebsiella pneumoniae]], [[Klebsiella oxytoca]], and [[Escherichia coli]]
+|[[cefpodoxime]]
+|≤17 mm
+|≥8 μg/mL
+|-
+|[[ceftazidime]]
+|≤22 mm
+|≥2 μg/mL
+|-
+|[[aztreonam]]
+|≤27 mm
+|≥2 μg/mL
+|-
+|[[cefotaxime]]
+|≤27 mm
+|≥2 μg/mL
+|-
+|[[ceftriaxone]]
+|≤25 mm
+|≥2 μg/mL
+|-
+| rowspan="3" |[[Proteus mirabilis]]
+|[[cefpodoxime]]
+|≤22 mm
+|≥2 μg/mL
+|-
+|[[ceftazidime]]
+|≤22 mm
+|≥2 μg/mL
+|-
+|[[cefotaxime]]
+|≤27 mm
+|≥2 μg/mL
+|}
+* For organisms that screen positive, they are then tested for third-generation [[Cephalosporins|cephalosporin]] resistance that is attenuated by [[clavulanic acid]]
+** CLSI uses either [[ceftazidime]] or [[cefotaxime]], with and without [[clavulanic acid]]
+** An increase in the zone of ≥5 mm is diagnostic of ESBL production