ETEST® Reading Guide ERG 001

Aerobic Bacteria 1)

organism effects

Ignore haemolysis (e.g. strep) Ignore swarming (e.g. Proteus spp.) S. maltophilia – trim/sulfa Pneumococci – ß-lactams Pneumococci – ß-lactams, read
Read growth; 0.032 μg/mL Read growth edge; 0.064 μg/mL Ignore haze in ellipse; 0.19 μg/mL Read all growth; 4 μg/mL haze/inner colonies; 1.5 μg/mL

drug effects

Bactericidal drugs – read hazes, Bactericidal drugs – read macro/ Bacteriostatic drugs – read at Tigecycline – read at 80 % Linezolid – read at 90%
microcolonies; 1.5 μg/mL microcolonies; ≥32 μg/mL 80 % inhibition; 0.032 μg/mL inhibition; 0.032 μg/mL inhibition; 1 μg/mL

Intrinsic activity, clavulanate ß-lactams – paradoxical effect Glycopeptides – slim ellipse Polypeptides – slim ellipse Polypeptides – read colonies in
Extrapolate curve; 3 μg/mL Read all growth; ≥256 μg/mL Read end of dip; 1 μg/mL Read bottom of dip; 0.38 μg/mL the dip; 3 μg/mL

RESISTANCE effects

GISA/hGISA – vancomycin ORSA – oxacillin KPC – carbapenems ß-lactamase induction by Small colony variants –
Read all growth; 8 μg/mL Read all growth; 64 μg/mL Read all colonies; 8 μg/mL clavulanate; ≥256 μg/mL bactericidal drugs; 32 μg/mL

technical and handling

Between markings – read upper Etest strip placed upside down Uneven – read upper value; if Ignore line of growth Distorted ellipse – wet surface,
value; 0.19 μg/mL Invalid; repeat the test >1 dilution, repeat the test alongside strip; 0.25 μg/mL invalid; repeat the test
1)
Please see CIS 006 (cidal/static chart), CIS 007 (reading endpoints) and product package inserts for additional reading information (www.abbiodisk.com/ETM).
ETEST® Reading Guide ERG 002
Antifungals
Azoles

Candida albicans – clear endpoint; Candida spp. – slim ellipse C. albicans – ignore lawn of C. parapsilosis – trailing Candida spp. – read all
0.047 µg/mL with trailing microcolonies; microcolonies, read at 80% microcolonies; 0.25 µg/mL macrocolonies in the ellipse,
0.125 µg/mL inhibition; 0.19 μg/mL (potential hetero-resistance);
1 µg/mL

Amphotericin B

C. krusei – read all C. glabrata – higher MIC with Candida spp. – clear endpoint; Candida spp. – read at complete Candida spp. – slim ellipse, read
macrocolonies in the ellipse; trailing colonies; 24 µg/mL 0.094 µg/mL inhibition of growth; 3 µg/mL all growth and microcolonies;
≥256 µg/mL 3 µg/mL

Flucytosine Echinocandins

C. tropicalis – read at 90% C. albicans – read all Candida spp. – 80%, ignore C. albicans –”dip effect” read C. tropicalis – ignore regrowth
inhibition. Ignore minute macrocolonies in the ellipse; microcolonies; 0.012 µg/mL MIC at bottom of the dip; at higher concentrations;
microcolonies; 1 µg/mL ≥32 µg/mL 0.064 µg/mL 0.125 µg/mL

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