Detecting the cefazolin inoculum effect with a rapid test. #IDWeek2022
Sara I. Gomez Villegas, MD; @SuperBugDoc
When S. aureus MIC to cefazolin increases in vitro when inoculum increased
Prevalence 3-15%
Retrospective studies find CzIE associated with poorer outcomes
Sara I. Gomez Villegas, MD; @SuperBugDoc
When S. aureus MIC to cefazolin increases in vitro when inoculum increased
Prevalence 3-15%
Retrospective studies find CzIE associated with poorer outcomes
Looking at dataset from pediatric OM
250 MSSA with 14.4% CzIE+. These were associated with progression from acute to chronic OM
Gold standard for detection is BMD. Cumbersome test. 3 days for test.
250 MSSA with 14.4% CzIE+. These were associated with progression from acute to chronic OM
Gold standard for detection is BMD. Cumbersome test. 3 days for test.
CzIE+ isolates release more BlaZ enzyme. Nitrocefin changes colour in the presence of B-lactamase
Novel 3 hr assay to detect CzIE
Aim: evaluate accuracy of nitrocefin test
Novel 3 hr assay to detect CzIE
Aim: evaluate accuracy of nitrocefin test
Sensitivity ~80%, specificity ~90% compared to reference BMD. Overall accuracy of 89%
BlaZ type A most commonly associated with CzIE. Sens 96%, spec 80% for these
BlaZ type A most commonly associated with CzIE. Sens 96%, spec 80% for these
Looks like v useful test - probably needs further validation and validation in other labs
And of course the clinical Q remains: is the CzIE clinically relevant?
And of course the clinical Q remains: is the CzIE clinically relevant?
This is something @snap_trial can look at. Among MSSA cases randomised to flucloxacillin or cefazolin, determine CzIE. If relevant, hypothesis no diff in fluclox arm regardless of CzIE, but poorer outcomes in cefazolin arm if CzIE present (vs not)
@SuperBugDoc
@SuperBugDoc
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