Failure of Antimicrobial Therapy

FAILURE OF ANTIMICROBIAL THERAPY

The success of antimicrobial therapy can be measured either clinically in terms of improvement in symptoms/signs or microbiologically as eradication of the infecting organism.

Antimicrobials may fail to cure an infection/ fever, or there may be relapses. This is rare when antimicrobial therapy was begun, in the first place, on sound clinical and/or bacteriological basis. When a real or apparent failure of the antimicrobial regimen occurs, the diagnosis and therapy should be reviewed. One of the following causes will usually be identified.

1.       Improper selection of drug, dose, route or duration of treatment.

2.       Treatment begun too late.

3.       Failure to take necessary adjuvant measures, e.g. drainage of abscesses, empyema, etc.; removal of renal stones, other foreign bodies or infected gall bladder, adjustment of proper urinary pH in case of urinary tract infection; cavity closure; control of diabetes, etc.

4.       Poor host defence—as in leukaemias, neutropenia and other causes, especially if a bacteriostatic AMA is used.

5.       Infecting organism present behind barriers, such as vegetation on heart valves (SABE), inside the eyeball, blood brainbarrier.

6.       Trying to treat untreatable (viral) infections or other causes of fever (malignancy, collagen diseases).

7.       Presence of dormant or altered organisms (the persisters) which later give rise to a relapse.