Clusters of circulating Neisseria gonorrhoeae strains and association with antimicrobial resistance in Shanghai.
OBJECTIVE
(i) To distinguish Neisseria gonorrhoeae isolates in Shanghai by porB typing; (ii) to ascertain the congruence of porB DNA sequence typing with cases linked epidemiologically; (iii) to determine the association of specific PorB mutations with antimicrobial resistance to penicillin or tetracycline.


METHODS
porB DNA sequences of 174 N. gonorrhoeae isolates, collected from 143 male patients and 31 female sexual partners in Shanghai were determined. Phylogenetic analysis was used to determine sequence associations and concordance with epidemiologically linked cases. PorB protein sequences were compared with the wild-type sequence to identify mutations associated with antimicrobial resistance to penicillin and tetracycline.


RESULTS
porB1a genotypes comprised 27.0% of the isolates and included 15 distinct DNA sequences, while 73.0% of the isolates carried porB1b genotypes with 63 distinct DNA sequences. porB DNA sequence typing was congruent with patient-reported sexual contacts. In addition, porB DNA sequence analysis revealed a number of strains with identical DNA sequences not identified through traditional epidemiological methods. The porB1b isolates had a significantly higher percentage of chromosomally mediated resistance to tetracycline and higher MIC50s to penicillin and ciprofloxacin. G120K/A121D mutations were observed in 71.1% of PIB isolates and were associated with resistance to penicillin and/or tetracycline. The majority of the PIA isolates (82.1%) also carried G120D/A121G double mutations. The index of discrimination for porB DNA sequence analysis was 95%.


CONCLUSIONS
The porB1b genotype was found to be predominant in Shanghai. porB DNA sequence typing was sufficiently discriminatory for differentiating N. gonorrhoeae isolates and was congruent with epidemiological linkages. Novel porB sequences of N. gonorrhoeae and novel mutations of PorB proteins were identified.
Liao
Mingmin
M
Vaccine and Infectious Disease Organization, University of Saskatchewan, 120 Veterinary Road, Saskatoon, Saskatchewan, Canada S7N 5E3.
Bell
Kelli
K
Gu
Wei-Ming
WM
Yang
Yang
Y
Eng
Nelson F
NF
Fu
Wenkai
W
Wu
Lei
L
Zhang
Chu-Guang
CG
Chen
Yue
Y
Jolly
Ann M
AM
Dillon
Jo-Anne R
JA
D002681:China; D016000:Cluster Analysis; D004352:Drug Resistance, Microbial / Q000235:genetics*; D005260:Female; D006069:Gonorrhea / Q000188:drug therapy / Q000453:epidemiology* / Q000235:genetics*; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics; D009344:Neisseria gonorrhoeae / Q000235:genetics* / Q000302:isolation & purification*; D010802:Phylogeny; D017422:Sequence Analysis, DNA