Antibiotic Susceptibility tests (AST)

What are antibiotic susceptibility tests (AST) ?

AST are part of the routine process of infection disease diagnosis. Once the germ responsible for an infection has been identified, a subsequent antibiotic susceptibility test is run to determine which antibiotic the germ is sensitive to. The patient then receives the appropriate antibiotic, at the right concentration.

Key Figures

of mis-prescriptions per year in US hospitals

deaths per year caused by antibiotic resistance in Europe


increase in mortality per hour delay in appropriately treating sepsis

annual overall cost in the US

What is the medical need today?

Susceptibility testing methods are based on exposing bacteria to antibiotics and observing the response (phenotypic testing) or specific genetic tests (genetic testing). Methods used may be qualitative, meaning a result indicates resistance is or is not present; or quantitative, using a minimum inhibitory concentration (MIC) to describe the concentration of antibiotic to which a bacterium is sensitive.

Current methods take up to 8 to 16 hours to perform an AST. The current turn-around time is so long, that patients are most of the time prescribed with broad-spectrum antibiotics while waiting for the AST results. This typical antibiotic misuse and/or overuse leads to antimicrobial resistance which is a global concern today, as listed by the World Health Organization (WHO).

What are the main features of C4AST diagnostic test ?

The C4AST kit is composed of an automated system to test isolated colony for their antibiotic resistance. The test leverages on C4Diagnostics’s patented click-chemistry technology and is designed to reduce by 8 the time to results compared to the gold standard. Overall the AST is performed in less than 2 hours.

The time saved in critical as in cases of acute infections such as sepsis, the mortality rate increases by 4% every hour without the appropriate antibiotic. Moreover it helps reducing the empirical prescription of “broad-spectrum” antibiotics, which are responsible for the rapid increase in antibiotic resistance and burdens healthcare costs.