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Cefixime resistance in Neisseria gonorrhoeae isolates from 2006 to 2010: correlation of MIC values with target gene alterations, the Italian experience

Abstract number: P988

Carannante A., Dal Conte I., Ghisetti V., Del Re S., Cusini M., Scioccati L., Prignano G., Palamara G., Di Carlo A., Sambri V., D'Antuono A., Cavrini F., Matteelli A., De Francesco M., Di Taranto A., De Nittis R., Stefanelli P.

Objectives: Reduced susceptibility to cephalosporins, now recommended as the mainstay of treatment, along with some treatment failures with cefixime have been reported for Neisseria gonorrhoeae.

Aim of this study was to test the cefixime and ceftriaxone susceptibility of strains isolated from 2006 to 2010 in Italy. Analyses of genetic mechanisms for resistance and the genetic relationship among the isolates have been also carried out looking for correlation with MICs.

Methods: Minimum inhibitory concentrations (MIC) for Ceftriaxone and Cefixime were determined by the E-test method (AB biodisk, Solna Sweden) and agar dilution on 265 N. gonorrhoeae strains isolated from 2006–2010. The EUCAST 2010 (MIC R >0.12 mg/L) and CLSI 2009 (MIC R geqslant R: gt-or-equal, slanted0.25 mg/L) breakpoints were taken into account. PenA, mtrR, porb1B and ponB sequences together with NGMAST analyses have been also determined.

Results: The majority of the gonococci were susceptible to both antibiotics. According to the EUCAST breakpoint 12% resulted resistant to cefixime compared to only 1% according to the CLSI reference breakpoint. However, the number of gonococci with cefixime MICs of 0.125–0.25 mg/L has increased in Italy during 2009–2010. These MICs lie on the edge of the breakpoints. The complete nucleotide sequence of penA from 45 isolates (either susceptible or with decreased susceptibility/resistance) were determined. Five amino acid sequence patterns in PBP2 were identified. These sequences were compared and isolates with MIC geqslant R: gt-or-equal, slanted0.125 mg/L all shared the sequence pattern XXXII. The majority of strains with MIC geqslant R: gt-or-equal, slanted0.125 mg/L belonged to ST1407 already described in cefixime resistant strains worldwide. The other target genes did not show any specific alterations compared to susceptible strains. All the examined strains were fully susceptible to ceftriaxone.

Conclusions: An upward rate of cefixime resistant or with decreased susceptibility has been found among Italian gonococci isolated from 2006–2010. Our findings show that the PBP2 is involved in resistance or reduced susceptibility equally. The remaining target genes do not influence the genetic mechanism of resistance or decreased susceptibility to cefixime. These data underline once more the usefulness of individual testing and local surveillance of N. gonorrhoeae in order to update treatment recommendations and therefore help in disease control.

Session Details

Date: 07/05/2011
Time: 00:00-00:00
Session name: Abstracts of 21st ECCMID / 27th ICC
Subject:
Location: Milan, Italy, 7 - 10 May 2011
Presentation type:
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