Resistance mechanisms in S. pneumoniae in the Netherlands
Abstract number: p1275
Mouton J.W., Klomberg D., Meijers S., Klaassen C.
In 1999, 20012002 and 2003 we performed surveys in The Netherlands (NL) to monitor antimicrobial resistance in S. pneumoniae (SP). We found increasing prevalence of macrolide resistance but virtually no resistance to quinolones. We here report the survey in 2005; we also determined the resistance mechanisms to macrolide and quinolone resistance, if present. In particular, we looked at the number of non-wild-type at the right tail of the MIC distribution of levofloxacin (Le).
34 laboratories equally distributed throughout NL participated in the study. Each lab was asked to collect up to 25 strains of consecutive samples. Only blood or sputum (including lavage) was allowed. Strains were identified by participating laboratories using their own standard identification technique. MIC's were determined using the E-test on site for (Le), Moxifloxacin (Mo), Penicillin (Pe), Amoxicillin, Clarithromycin (Cl), Azithromycin, Cefotaxim (Ce), Cotrimozazole and Doxycyclin; control ATCC strains were included. Afterwards, strains were collected by the central lab for further analysis. Identification confirmation of SP was performed by bile solubility testing and also by LytA PCR for resistant strains. Resistance genes were identified using validated PCR-based methods for all strains with a MIC of >1 mg/L for Le, >0.5 mg/L for Cl and >0.06 for Pe.
Overall, 12.7% of strains were Cl R, 0.5% Le R and 5.9% Pe I or R. 5.2% of strains had a MIC of 1.5 or 2 mg/L for Le. Of these, 32% were non SP (LytA-), comparable to results from earlier surveys in NL. Of the remaining strains, 25% had a known ParC or GyrA mutation, no mutations of ParE or GyrB were found. Of the Cl R strains, 41% was LytA-. Of the LytA + strains, 43% possessed the ErmB gene, 30% MefA, 5% MefE, 5% a 23S mutation, one strain a L4 mutation and no strains with ErmTR or L22 mutation. No mechanism was found for 6 strains. Interestingly, one Pe I strain was ErmB positive but susceptible to Cl. All strains were Ce susceptible.
Routine identification of true Sp remains problematic. Macrolide resistance in Pneumococci is still increasing in The Netherlands and approaches values that may prohibit blind prescribing. Analysis of less susceptible Le strains indicate that a ParC or GyrA mutation is present in a significant portion at the tail of the wildtype distribution. Given the PkPd characteristics, Le treatment may pose a risk for selection of double mutants.
|Session name:||XXIst ISTH Congress|
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