Description of blaTEM-48 ESBL gene carried in addition to blaSHV-5 gene within the same megaplasmid of nosocomial Klebsiella pneumoniae strains

Abstract number: 1733_171

Alcántar-Curiel M., Ortíz J., Morfin R., Gayosso C., Esparza S., Carlos A., Rodríguez-Noriega E., Santos J., Alpuche-Aranda C.

Background: Prevalence of ESBL-producing Klebsiella pneumoniae (Kpn) and other Gram-negatives in the United States of America (USA) is relatively lower compare to Mexico. The most common ESBLs (85%) described in México are SHV-5 and TLA-1 and in contrast to US there was no description of TEM ESBLs in Mexico before.

Methods: We collected nosocomial Kpn strains isolated over a 45 month period in a Mexican Hosp. Antimicrobial susceptibility patterns were determined by diffusion and dilution methods. Genotyping was determined by PFGE. E-test, isoelectrical point focusing (pI) and kinetic studies by spectrophotometric assay were used to define ESBL production. Conjugation, restriction endonuclease and Southern blot were used to characterise plasmids. PCR and sequencing analysis were used to molecular characterise ESBLs.

Results: Sixty two per cent of the 168 Kpn strains collected were ESBL producers and they were part of 23 different clones. ESBL in addition to other antibacterial resistance phenotype were transferred by conjugation of one plasmid. Most of the clones produced ESBLs with pI 7.5 and 8.2 and only two (G18 and G56) produced ESBL pI 6.0, 7.5 and 8.2. Those with pI 6.0 and 8.2 were transferred in the same identical megaplasmid in both clones. ESBL pI 8.2 corresponded to SHV-5. ESBL pI 6.0 preferentially hydrolyzed cefotaxime and it was PCR amplified by blaTEM specific primers. The deduced protein sequences showed to be 100% identical to blaTEM-48.

Conclusion: Prevalence of ESBL-producing Kpn strains in Mexico is very high mostly related to blaSHV-5 gene carried in a plasmid. However blaTEM genes can also be present in these plasmids. This is the first report of an ESBL-TEM family produced in Mexico.