Result reliability


The detection of antimicrobial substances in a sample for bacterial culture is important for correct result interpretation.
In the absence of clinical data the Residual Antimicrobial Activity (RAA) test result is of value to the microbiologist in the interpretation of the culture test, especially in case of not reported antibiotic therapies, and helps to avoid the reporting of false negative results.


Sidecar, Alfred 60AST and HB&L systems perform the RAA test and bacterial culture simultaneously (1).
Using Staphylococcus epidermidis as a growth control it is possible to check for the presence of antibiotics and drugs or foods with antibacterial properties that inhibit bacterial growth in a sample.
Simultaneously with bacterial culture, the native sample is inoculated into a vial containing a Staphylococcus epidermidis suspension which is sensitive to most of the commonly used antibiotics.
The systems allow the determination of Residual Antibiotic Activity in the sample by comparing the Staphylococcus epidermidis with the bacterial culture growth curves.
The Alifax RAA test is also useful to monitor the effectiveness of therapy and verify if the antibiotic has reached the infection site (2,3).
RAA test results are simultaneously displayed with bacterial growth results in Urine and Human Biological Liquid cultures.


Results Interpretation
RAA- Culture- Culture test result is confirmed
RAA- Culture+ Culture test result is confirmed
RAA+ Culture- Residual antimicrobial activity detected
Further investigations are required
RAA+ Culture+ Residual antimicrobial activity detected
Therapy is not working or not reaching the site Further investigations are required