16S rRNA Methyltransferase RmtC in Salmonella enterica Serovar Virchow

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Volume 16, Number 4–April 2010
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16S rRNA Methyltransferase RmtC in Salmonella enterica Serovar Virchow
Katie L. Hopkins, Jose A. Escudero, Laura Hidalgo, and Bruno Gonzalez-Zorn
Author affiliations: Health Protection Agency Centre for Infections, London, UK (K.L. Hopkins); and Universidad Complutense de Madrid, Madrid, Spain (J.A. Escudero, L. Hidalgo, B. Gonzalez-Zorn)

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Abstract
We screened Salmonella and Escherichia coli isolates, collected 2004–2008 in the United Kingdom, for 16S rRNA methyltransferases. rmtC was identified in S. enterica serovar Virchow isolates from clinical samples and food. All isolates were clonally related and bore the rmtC gene on the bacterial chromosome. Surveillance for and research on these resistance determinants are essential.

Aminoglycosides are used in treating a wide range of infections caused by both gram-negative and gram-positive bacteria and have been classified by the World Health Organization as critically important antimicrobial drugs in human medicine (1). They inhibit bacterial protein synthesis by binding irreversibly to the bacterial 16S ribosomal subunit, which thereby leads to cell death. Resistance to these antimicrobial agents usually results from production of aminoglycoside-modifying enzymes (such as acetyltransferases, phosphorylases, and adenyltransferases), reduced intracellular antimicrobial drug accumulation, or mutation of ribosomal proteins or rRNA. An additional mechanism, methylation of the aminoacyl site of 16S rRNA, confers high-level resistance to clinically important aminoglycosides such as amikacin, tobramycin, and gentamicin. Six types of 16S rRNA methyltransferase genes conferring resistance to these antimicrobial agents, armA, rmtA, rmtB, rmtC, rmtD, and npmA, have been identified (2,3). armA and rmtB are spread in enterobacteria worldwide, and the presence of other methyltransferase genes have not previously been reported in Europe (3). With the exceptions of armA and rmtB in porcine Escherichia coli from Spain and the People's Republic of China, respectively (4,5), all methyltransferase genes described have been identified in human clinical samples, for which a possible role for food in transmission of these determinants remains largely unknown. Despite large surveys performed to identify 16S rRNA methyltransferases, the rmtC gene has been detected in only 2 Proteus mirabilis clinical isolates from Japan and Australia in 2006 and 2008, respectively (3,6,7). In this study, 81,632 Salmonella and 10,700 Escherichia coli isolates obtained from the Health Protection Agency (HPA) Centre for Infections culture collection (isolated from January 2004 through December 2008) were screened for the presence of 16S rRNA methyltransferases.

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Suggested Citation for this Article
Hopkins KL, Escudero JA, Hidalgo L, Gonzalez-Zorn B. 16S rRNA methyltransferase RmtC in Salmonella enterica serovar Virchow. Emerg Infect Dis [serial on the Internet]. 2010 Apr [date cited]. http://www.cdc.gov/EID/content/16/4/712.htm

DOI: 10.3201/eid1604.090736