Fig. 1

A schematic representation of how N. gonorrhoeae benzylpenicillin MIC distributions could change over time. A type A shift involves in the first stage, the emergence of a second population of less susceptible isolates (black, long-dashed line). With further selection pressure all the gonococci move into the higher MIC peak resulting in a right-shifted unimodal distribution (type A, stage 2, black, short-dashed line). This distribution could then develop a new subpopulation with higher MICs resulting in a new bimodal distribution (Type A, stage 3; grey, long-dashed line). Alternatively, the decrease in susceptibility results from a shift in the whole population (type B shift, green, short-dashed line)