Jar. Dillon et al., DISCRIMINATORY POWER OF TYPING SCHEMES BASED ON SIMPSON INDEX OF DIVERSITY FOR NEISSERIA-GONORRHOEAE, Journal of clinical microbiology, 31(10), 1993, pp. 2831-2833
Simpson's index of diversity was used to produce a single numerical va
lue to compare the abilities of single or combined typing schemes to d
iscriminate between unrelated isolates. This calculation was used to c
ompare the discriminating power of auxotype and serovar determination
and plasmid content analysis, either singly or in combination, for Nei
sseria gonorrhoeae isolates having different antimicrobial susceptibil
ities (i.e., antibiotic-susceptible isolates and those that produce pe
nicillinase, carry plasmid-mediated resistance to tetracycline, have c
hromosomally mediated penicillin resistance, or both produce penicilli
nase and carry plasmid-mediated resistance to tetracycline). Plasmid c
ontent analysis and auxotype determination produced the lowest level o
f discrimination, while a combination of auxotype and serovar typing s
chemes generally provided higher levels of discrimination. Addition of
plasmid content analysis to auxotype and serovar typing provided addi
tional discrimination only with penicillinase-producing isolates. For
isolates that carried plasmid-mediated resistance to tetracycline, iso
lates that were tetracycline resistant, isolates that both produced pe
nicillinase and carried plasmid-mediated resistance to tetracycline, o
r isolates that had chromosomally mediated penicillin resistance, none
of the typing methods produced high discriminatory indices, indicatin
g that these isolates are probably derived from relatively few clones.