Background N. gonorrhoeae(Ng) has developed resistance to most antimicrobial used for treatment. The report of the first resistant isolates of Ceftriaxone (CRO) in Japan, France and Spain, highlighted the lack of alternatives for syndromic treatment of Ng. In Argentina, although no resistance has been reported, the first isolates with decreased susceptibility to CRO (CROLS) appear in 2011.

Materials and Methods: We studied 5649 Ng isolates since 1993 derived from Argentine Gonococcal Antimicrobial-Susceptibility Network. MIC was determined by agar dilution according to CLSI recommendations. We studied extended spectrum cephalosporins (ESCs) resistance determinant ( mtr, penA, porB) by sequencing and carry out the molecular typing by Ng multi-antigen sequence typing (NG-MAST).

Results We detected 10 CROLS isolates, 4 showed a CRO MICs of 0.064 μg/ml and 6 of them of 0.125 μg/ml. All isolates were also resistant to two or more antimicrobial agents (Penicilin and Tetracycline and/or Ciprofloxacin) and showed decreased susceptibility to Cefixime with MICs between 0.125 and 0.5 µg/ml.

Six NG-MAST sequence types (STs) were detected, with ST925 (n = 3) and ST1407 (n = 3) being most common. Also found ST225, ST3620 and two new STs: ST8508 and ST8509.

The penA gene analysis revealed three different no mosaic alleles patterns: V (n = 1), IX (n = 1) and XII (n = 1) and two mosaic alleles patterns: XXXIV (n = 4) and X (n = 3). Nine isolates showed mutations in G120 and A121 positions in porB1b allele and one isolate revealed A121G substitution in allele porB1a, both previously described. All isolates carried a nucleotide (A) deletion in the inverted region of mtrR gene.

Conclusion The evidence of the first isolates with decreased susceptibility to ESC in Argentina and the presence of ST1407 involved in the extensively drug resistant Ng raise the need for emphasise surveillance studies to ESC and know the distribution of ST1407 in our Region and its associated resistance.