Antimicrobial sensitivity testing. Lab technician analysing inhibition zones on an agar plate inoculated with a Pseudomonas aeruginosa bacteria. Susceptibility testing is being carried out using an etest, a type of antimicrobial sensitivity test. It uses an antimicrobial infused strip (centre). The antimicrobials diffuse into the culture medium. A sensitive species will show a zone of inhibition, while uninhibited bacterial growth will indicate resistance to the antimicrobial. The bacteria don't show any inhibition against the antimicrobials tested here.