Genomic homogeneity of the AHU/IA-1,2 phenotype of Neisseria gonorrhoeae during its disappearance from an urban population.
BACKGROUND
Isolates of Neisseria gonorrhoeae requiring arginine, hypoxanthine, and uracil (AHU) appeared in Denmark in 1946, were preponderant in Seattle during the 1970s, were associated with disseminated gonococcal infections (DGI), and were primarily of the IA-1,2 serovar.


OBJECTIVE
To investigate the disappearance of the AHU/IA-1,2 phenotype and to examine by pulsed-field gel electrophoresis (PFGE) the genomic homogeneity of this unique phenotype isolated from Seattle-King County during the past decade.


METHODS
This retrospective study used data extracted from previous publications for the period 1971 through 1984, and from existing records at the Neisseria Reference Laboratory, University of Washington for the period 1985 through 1996. Samples (n = 68) of AHU/IA-1,2 isolates from 1984 to 1985 and 1988 to 1993 were analyzed using endonucleases NheI and XbaI. For comparison, 10 AHU/IB isolates were included in the study.


RESULTS
AHU isolates, predominantly IA-1,2 strains accounted for 52% of the gonococcal isolates for the period 1971 through 1974, 40% for 1974 through 1976, 16% for 1984, and then declined from 7% in 1986 to 0% for each of the last 3 years, 1994 through 1996. Isolates with < or = 1 band difference after digestion with either NheI or XbaI were considered to belong to a single closely related pattern. Pulsed-field gel electrophoresis (PFGE) type designation was made from the combination of NheI and XbaI patterns. These criteria yielded 5 NheI and 8 XbaI PFGE patterns, and 11 PFGE types based on the combination of NheI and XbaI pattern. The most frequently occurring NheI and XbaI patterns accounted for 74% and 57% of isolates, respectively. One type persisted throughout the decade and accounted for 54% of the 68 isolates. Analysis of the 10 AHU/IB isolates yielded 7 NheI and 8 XbaI patterns that gave 9 types that were distinct from the types found in the AHU/IA-1,2 strains.


CONCLUSIONS
The AHU/IA-1,2 phenotype first documented 50 years ago in Denmark still shows a high degree of genomic homogeneity during the past decade in Seattle. The implementation of screening, decreased rates of sexual exposure in the acquired immune deficiency syndrome era, or other factors may explain its apparent elimination in Seattle-King County.
Xia
M
M
Department of Pathobiology, University of Washington, Seattle 98195, USA.
Whittington
W L
WL
Holmes
K K
KK
Roberts
M C
MC
D016521:Electrophoresis, Gel, Pulsed-Field; D014644:Genetic Variation; D006069:Gonorrhea / Q000382:microbiology*; D006801:Humans; D009344:Neisseria gonorrhoeae / Q000145:classification / Q000235:genetics*; D010641:Phenotype