Variability of Inc group of conjugative plasmids and CTX-M gene environments in Enterobacteriaceae nosocomial strains isolated from Russia

Abstract number: O197

Fursova N.K., Abaev I.V., Pryamchuk S.D., Shishkova N.A., Pecherskikh E.I., Korobova O.V., Kruglov A.N., Weigel L.M., Rasheed J.K.

Objectives: CTX-M is the most prevalent type of extended-spectrum b-lactamase (ESBL) among clinical isolates [85% including Escherichia coli (n = 205) and Klebsiella pneumoniae (n = 151)] collected from 2003 to 2007 in Russia. Subtypes of blaCTX-M genes were identified: blaCTX-M-1 (92%), blaCTX-M-9 (6%), blaCTX-M-2 (1%), and a combination of blaCTX-M-1 and blaCTX-M-9 (1%). Plasmid localisation of blaCTX-M genes and a description of their gene environments are the focus of this study.

Methods: PCR mapping and DNA sequencing were used for detection, localisation, and identification of the genes under study. Conjugation was performed in broth using E. coli C600 (RifRAzR) as the recipient strain. Antimicrobial resistance phenotypes were determined by broth microdilution. Plasmid DNA was extracted by the method of Kado & Liu (1981) and plasmid incompatibility (Inc) group identification was determined by PCR-based replicon typing (Carattoli et al., 2005).

Results: All isolates examined carried blaCTX-M genes on large plasmids (~70–160 kb). Sixty plasmids were confirmed to be conjugative. Restriction fragment length polymorphism (RFLP) analysis indicated several different subgroups among plasmids of equivalent size. Plasmids appeared to belong to different Inc groups varying by genus and blaCTX-M allele (Fig.1). IncF, a major conjugative plasmid group in E. coli producing CTX-M1-like enzymes, included ISEcp1, IS26, and mucA structures. IncL/M, a major plasmid group in K. pneumoniae CTX-M1-positive strains demonstrated the same gene arrangement, but with more variants because of additional combinations and small insertions. Gene environments of CTX-M9-like genes include ISEcp1, IS26, and IS903 structures on IncI1, IncF, IncA/C (E. coli), and IncN (K. pneumoniae) plasmids. A unique E. coli strain had ORF153 upstream of a CTX-M2-like gene on an IncI1/IncP plasmid.

Conclusion: Nosocomial E. coli and K. pneumoniae isolates from different regions of Russia carry blaCTX-M genes on high-molecular weight plasmids belonging to various Inc groups. CTX-M gene environments are different for blaCTX-M subgroups and bacterial genera indicating differences in gene transmission mechanisms.

Acknowledgements: This study was done on the frame of the ISTS#2913/BTEP#62 Project.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Location: Barcelona, Spain
Presentation type:
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