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Table 1 Mean annular radius and expected ranges of WHO Neisseria gonorrhoeae reference strains (F, G, K, L, M, N, O and P)

From: Antimicrobial susceptibility testing of Neisseria gonorrhoeae isolates in Pakistan by Etest compared to Calibrated Dichotomous Sensitivity and Clinical Laboratory Standards Institute disc diffusion techniques

Methods Antibiotics tested F G K L M N O P
CDS Penicillin G Mean annular radius (range) 13.2 (12–15) 5.5 (3–7) 00 00 00 00 00 6 (5–7)
Expected result >9 (S) 3–9 (I) <3 (R) <3 (R) <3 (R) <3 (R) <3 (R) 3–9 (I)
β-lactamase production No No No No Yes Yes Yes No
Expected result No No No No Yes Yes Yes No
Ciprofloxacin Mean annular radius (range) 15 (14–17) 7.7 (7–9) 00 00 3.2 (02–4) 00 13.5 (12–15) 14.2 (13–16)
Expected result ≥11 (S) 6–10 (I) <6 (R) <6 (R) <6 (R) <6 (R) ≥11 (S) ≥11 (S)
Spectinomycin Mean annular radius (range) 11 (10–11) 10.2 (9–11) 16 (15–18) 9.5 (8–11) 11 (9–13) 13.5 (10–17) 00 13 (11–15)
Expected result ≥6 (S) ≥6 (S) ≥6 (S) ≥6 (S) ≥6 (S) ≥6 (S) <6 (R) ≥6 (S)
Azithromycin Mean annular radius (range) 12.5 (10–15) 14 (12–16) 13.5 (12–15) 11 (9–13) 12 (9–15) 11.5 (10–13) 13 (12–15) 1.5 (0–4)
Expected result ≥8 (S) ≥8 (S) ≥8 (S) ≥8 (S) ≥8 (S) ≥8 (S) ≥8 (S) <8 (R)
Ceftriaxone Mean annular radius (range) 14.2 (12–16) 14.7 (14–16) 6.7 (6–8) 5.5 (5–7) 13 (12–15) 13.2 (12–15) 13.2 (13–15) 13.7 (13–15)
Expected result ≥10 (S) ≥10 (S) 5–9 (DS) 5–9 (DS) ≥10 (S) ≥10 (S) ≥10 (S) ≥10 (S)
MIC by Etest Ceftriaxonea Etest MIC ranges <0.002 0.004–0.008 0.064–0.125 0.125–0.25 0.008–0.016 0.002–0.004 0.016–0.032 0.004–0.008
Expected result <0.002 (S) 0.004–0.016 (S) 0.032–0.125 (DS) 0.064–0.25 (DS) 0.008–0.032 (S) 0.002–0.008 (S) 0.016–0.064 (S) 0.002–0.008 (S)
  1. aMICs for control strains was performed only for ceftriaxone. DS Decreased susceptibility, S Sensitive, I intermediate, R resistant