Carbapenemase-producing Salmonella enterica serotype Kentucky ST198, North Africa.
Résumé
in the coding sequence. These mutations have previously been shown to result in increased azithromycin resistance due to induced expression of the MtrCDE efflux pump. 8 The genes erm(A), erm(B), erm(C) and erm(F), encoding rRNA methylases, and mef(A), encoding an efflux pump, were not present in these isolates. Molecular epidemiology analysis of the isolates was performed using the N. gonorrhoeae multiantigen sequence typing (NG-MAST) method, 9 which assigns an ST based on a combination of the highly variable por and tbpB alleles. The isolates were assigned ST3102 and ST1866, which are almost identical and differ only by one SNP in por. Thus far, the high-level azithromycin-resistant N. gonorrhoeae strains that have been isolated in various countries belong to 16 different STs, of which ST649 isolates appear to be most widespread. 5 – 7 The por and tbpB alleles of these STs differ by a total of 33–92 SNPs from the por and tbpB alleles of the strains described in this study, except for the Australian ST10133 isolate, 7 which contains an identical tbpB allele (33) and a por allele (2573) that only differs by 16 and 17 SNPs from the por alleles of ST3102 and ST1866, respectively. Interestingly, it was reported that this isolate was most likely contracted in China or Hong Kong, which might explain its closer genetic relationship. How widespread high-level azithromycin-resistant strains are in China remains to be determined. Several years earlier, in 2009, two ST1866 strains were isolated from patients in the city of Nanjing, 10 which is located in a neighbouring province. These strains were reported to have an azithromycin MIC of .64 mg/L. It is not known whether these strains actually are directly related to the ST1866 isolate described in this study, but if they are related it would indicate that this high-level azithromycin-resistant ST might be spreading in China. Azithromycin susceptibility testing is currently not the standard in China. However, the identification of high-level azithromycin-resistant N. gonorrhoeae isolates stresses the need for a more thorough overview of azithromycin susceptibility in China, particularly when ceftriaxone and azithromycin dual antimicrobial therapy is considered as a future first-line therapy. These high-level azithromycin-resistant isolates might have a major impact on the efficacy of this dual antimicrobial therapy.