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Antimicrobial Agents and Chemotherapy, March 2001, p. 734-738, Vol. 45, No. 3
Department of Microbiology, The Prince of
Wales Hospital, Randwick, Sydney, New South Wales, Australia 2031
Received 25 August 2000/Returned for modification 26 September
2000/Accepted 19 November 2000
The in vitro activities of ciprofloxacin, trovafloxacin,
moxifloxacin, and grepafloxacin against 174 strains of Neisseria gonorrhoeae isolated in Sydney, Australia, were determined. The strains included 84 quinolone-less-sensitive and -resistant N. gonorrhoeae (QRNG) strains for which ciprofloxacin MICs were in the range of 0.12 to 16 µg/ml. The QRNG included strains isolated from patients whose infections were acquired in a number of countries, mostly in Southeast Asia. The gyrA and parC
quinolone resistance-determining regions (QRDR) of 18 selected QRNG
strains were sequenced, and the amino acid mutations observed were
related to the MICs obtained. The activities of moxifloxacin and
grepafloxacin against QRNG were comparable to that of ciprofloxacin.
Trovafloxacin was more active than the other quinolones against some
but not all of the QRNG strains. Increments in ciprofloxacin resistance
occurred in a step-wise manner with point mutations initiated in
gyrA resulting in amino acid alterations Ser91-to-Phe,
Ser91-to-Tyr, Asp95-to-Gly, and Asp95-to-Asn. Single gyrA
changes correlated with ciprofloxacin MICs in the range 0.12 to 1 µg/ml. The Ser91 changes in GyrA were associated with higher MICs and
further QRDR changes. QRNG strains for which ciprofloxacin MICs were
greater than 1 µg/ml had both gyrA and parC
QRDR point mutations. ParC alterations were seen in these isolates only
in the presence of GyrA changes and comprised amino acid changes
Asp86-to-Asn, Ser87-to-Asn, Ser87-to-Arg, Ser88-to-Pro, Glu91-to-Lys,
and Glu91-to-Gln. QRNG strains for which MICs were in the higher ranges
had double GyrA mutations, but again only with accompanying ParC
alterations. Not only did the nature and combination of GyrA and ParC
changes influence the incremental increases in ciprofloxacin MICs, but
they seemingly also altered the differential activity of trovafloxacin.
Our findings suggest that the newer quinolones of the type examined are
unlikely to be useful replacements for ciprofloxacin in the treatment
of gonorrhea, particularly where ciprofloxacin MICs are high or where
resistance is widespread.
0066-4804/01/$04.00+0 DOI: 10.1128/AAC.45.3.734-738.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Correlation of In Vitro Susceptibilities to Newer
Quinolones of Naturally Occurring Quinolone-Resistant Neisseria
gonorrhoeae Strains with Changes in GyrA and ParC
*
Corresponding author. Mailing address: Department of
Microbiology, The Prince of Wales Hospital, High Street, Randwick, NSW 2031, Australia. Phone: 61 2 9382 9084. Fax: 61 2 9398 4275. E-mail: shultztr{at}sesahs.nsw.gov.au.
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