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J Antimicrob Chemother. 2010 Dec;65(12):2543-7. doi: 10.1093/jac/dkq377. Epub 2010 Oct 12.

Alterations of the pilQ gene in Neisseria gonorrhoeae are unlikely contributors to decreased susceptibility to ceftriaxone and cefixime in clinical gonococcal strains.

Author information

1
Queensland Children's Medical Research Institute, Children's Health Service District, Brisbane, Queensland, Australia.

Abstract

OBJECTIVES:

Gonorrhoea remains a global public health problem and the treatment options are diminishing through the emergence of gonococci resistant to most antimicrobials. Previous in vitro studies have indicated a role for Neisseria gonorrhoeae pilQ alterations in conferring resistance to antimicrobials, including penicillin. In this study, we investigated whether pilQ polymorphisms were associated with decreased susceptibility to extended-spectrum cephalosporins (ESCs) in clinical gonococcal strains.

METHODS:

Full-length pilQ nucleotide and PilQ amino acid sequences from geographically and temporally diverse gonococcal clinical isolates (n = 63), including the 2008 WHO reference strains, representing a range of ceftriaxone and cefixime MICs (≤0.008-0.25 and <0.016-0.5 mg/L, respectively) and 38 N. gonorrhoeae multiantigen sequence types, were examined. Previously described alterations associated with decreased ESC susceptibility (mosaic penA, mtrR and penB alterations) were also examined.

RESULTS:

Fifteen different pilQ nucleotide sequence types and nine different PilQ amino acid sequence types were observed, with two PilQ types accounting for 53 (84%) of the isolates. Independent of other genetic resistance determinants (penA mosaic, mtrR promoter deletion and penB), only one pilQ alteration, a D526N substitution, provided a statistically significant association with ceftriaxone (P < 0.01) and cefixime (P < 0.05) MICs. However, the two isolates exhibiting D526N lacked all three previously described alterations associated with decreased ESC susceptibility, thereby providing an alternative basis for the low MICs (≤0.008 mg/L) observed for these strains. The previously described E666K (pilQ2) and F595L (pilQ1) mutations were absent in all 63 isolates.

CONCLUSIONS:

pilQ polymorphisms are unlikely contributors to decreased susceptibility to ESCs in clinical gonococcal strains.

PMID:
20940180
DOI:
10.1093/jac/dkq377
[Indexed for MEDLINE]

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