BlaCTX-M-15, (emerging or already disseminated in argentina?) Is immersed in different genetic contexts.

DI CONZA JOSÉ; SENATTI SAMANTA; SANTELLA GISELA; PALLECCHI LUCCIA; PINO MARYLÚ; ROSOLLINI GIAN MARIA; RADICE MARCELA; GUTKIND GABRIEL

Chicago

Conferencia; 51st ICAAC Interscience Conference on Antimicrobial Agents and Chemotherapy; 2011

America Society of Microbiology

Background: CTX-M-2 constituted not only the most prevalent but almost the unique cefotaximase described in Argentina. This survey was conducted to determine the current prevalence of ESBL, the eventual emergence of new cefotaximases and to characterize their genetic context. Method: All third generation cephlosporins (3GC) resistant enterobacteria recovered at 15 hospitals in Argentina during October 2010 were included. ESBL confirmatory test were performed according CLSI and AAM Antimicrobial Committee. Genetic characterization was performed by PCR amplification using specific primers and sequencing. The environments surrounding blaCTX-M-2 and blaCTX-M-15 were investigated by PCR mapping and DNA sequencing. Results: From 1,586 enterobacteria, 207 (13.1%) displayed 3GC. 50/55 isolates, recovered in one week within this period, were ESBL producers. blaCTX-M-2 was identified in 24 isolates while blaCTX-M-15 in 19. Also blaCTXM-14 was identified in 3 isolates and a non identified cefotaximase in other 3. All isolates harboring blaCTX-M-2 gene were associated downstream to ISCR1 element. Different genetic environments were found surrounding blaCTX-M-15. Thus 12/16 harbored the international blaCTX-M-15 genetic environment (Ac. NC013121.1), which contains ISEcp1 located 48 bp upstream of blaCTX-M-15. The remaining 4 isolates showed other surrounding structures. Conclusion: Although cefotaximases constitutes the main resistance mechanism, the absolute prevalence of CTX-M-2 reported previously has been displaced by the emergence and remarkable spread of CTX-M-15 and to a lesser extent of other group of cefotaximases. As previously described in Argentina, blaCTX-M-2 was located downstream to ISCR1 probably as part of an unusual class 1 integron. Although most blaCTX-M-15 showed the international blaCTX-M-15 genetic environment, different environments were found among studied isolates, suggesting the dissemination from different origins.