Skip to main page content

• HOME
• Current Issue
• Archive
• Alerts
• About ASM
• Contact us
• Tech Support
• Journals.ASM.org

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cordeiro, N. F. Articles by Vignoli, R. Search for Related Content PubMed PubMed Citation Articles by Cordeiro, N. F. Articles by Vignoli, R.

 Previous Article  |  Next Article 

Antimicrobial Agents and Chemotherapy, February 2008, p. 806-807, Vol. 52, No. 2
0066-4804/08/$08.00+0     doi:10.1128/AAC.00444-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

LETTER TO THE EDITOR

Ciprofloxacin-Resistant Enterobacteria Harboring the aac(6')-Ib-cr Variant Isolated from Feces of Inpatients in an Intensive Care Unit in Uruguay

Top LETTER REFERENCES

 
The presence of aac(6')-Ib-cr is associated with decreased susceptibility to aminoglycosides (kanamycin, amikacin, and tobramycin) and to norfloxacin and ciprofloxacin (9). This allelic variant of aac(6')-Ib was found to be linked to the extended-spectrum β-lactamase (ESBL) gene bla_CTX-M-15 in isolates from many countries (4, 6, 7), while association of aac(6')-Ib with the bla_CTX-M-2 ESBL gene has been widely reported in Uruguay and Argentina (3, 11).

In this work we looked for the presence of aac(6')-Ib and the aac(6')-Ib-cr variant and their putative ESBL coresistance markers in fecal isolates of enterobacteria resistant to ciprofloxacin and/or ceftazidime from inpatients in an intensive care unit (ICU) in Montevideo, Uruguay.

From 1 March to 31 October 2006, 106 patients were admitted to this ICU and followed daily until discharge. Rectal swabs obtained at 1, 4, 7, 10, 13, and 16 days after admission were plated on MacConkey agar plus ceftazidime (4 mg/liter) or ciprofloxacin (2 mg/liter). Enterobacterial isolates were identified by classical methods, including only the first isolate of each bacterial species per patient in this study.

Antibiotic resistance profiling, screening, and confirmatory testing for ESBL detection were performed by disk diffusion assay, and results were interpreted following the CLSI guidelines (2).

A total of 58/106 patients (55.2%) were colonized with ciprofloxacin- and/or ceftazidime-resistant enterobacteria, and 68 isolates were included in this study. Of these, 48 were resistant to gentamicin and 24 to amikacin (Table 1).

View this table: [in this window] [in a new window]

TABLE 1. Main characteristics of the 68 studied isolatesa

All aminoglycoside-resistant isolates were screened for aac(6')-Ib by PCR; amplicons were analyzed by restriction with BstF5I, as described by Park et al. (8). PCR products that were not digested by the enzyme [tentatively assigned to aac(6')-Ib-cr] were confirmed to contain aac(6')-Ib-cr by double-strand sequencing. Only two Escherichia coli isolates were positive for aac(6')-Ib-cr detection.

Recalling the observed links between bla_CTX-M-15 and aac(6')Ib-cr (4, 6, 7) and between aac(6')Ib and bla_CTX-M-2, the two aac(6')-Ib-cr-positive isolates were further analyzed by PCR to detect CTX-M-1 and CTX-M-2 group ESBL genes using previously described primers (3, 5). Both isolates were positive only for CTX-M-1 group genes, identified as bla_CTX-M-15 after sequencing.

Both isolates were obtained at the time of patient admission into the ICU and showed identical pulsed-field gel electrophoresis patterns (10). Both patients were previously hospitalized before ICU admission, suggesting that this strain could be endemic in the hospital, where it could be horizontally transferred. All the other E. coli isolates yielded different pulsotypes (data not shown) compared with these.

PCR assays for the detection of class 1 integrons and ISCR1 elements were performed according to the method of Di Conza et al. (3). Both isolates carried a class 1 integron containing the dfr17 and aadA5 gene cassettes, while ISCR1 elements were not detected.

So far we have not been able to transfer these resistance genes, either by transformation or by conjugation.

This is the first report of aac(6')-Ib-cr in Uruguay. In accordance with a previous report (6), bla_CTX-M-15 and aac(6')-Ib-cr do not seem to be associated with class 1 integrons. Demonstration of a link to IS26 as previously reported (1) is pending.

 
This work was partially supported by grants from S/C/OP/76/30 PDT (Programa de Desarrollo Tecnológico, Ministerio de Educación y Cultura Uruguay) to R.V. and also by grants from CSIC (Comisión Sectorial de Investigación Científica Uruguay) to N.F.C. Part of this work was also supported by grants LSHM-CT-2003-503335 from the European Community and BFU2006-04574 from Ministerio de Educación y Ciencia, España, to J.A.A. and grants from UBACYT and ANPCYT and a Carrillo-Oñativia fellowship to G.G.

 
Published ahead of print on 12 November 2007.

N.F.C. and L.R. contributed equally to the experimental work and to the elaboration of this report.

Top LETTER REFERENCES

 

1
1. Boyd, D. A., S. Tyler, S. Christianson, A. McGeer, M. P. Muller, B. M. Willey, E. Bryce, M. Gardam, P. Nordmann, M. R. Mulvey, and the Canadian Nosocomial Infection Surveillance Program, Health Canada. 2004. Complete nucleotide sequence of a 92-kilobase plasmid harboring the CTX-M-15 extended-spectrum beta-lactamase involved in an outbreak in long-term-care facilities in Toronto, Canada. Antimicrob. Agents Chemother. 48:3758-3764.[Abstract/Free Full Text]
2
2. Clinical and Laboratory Standards Institute. 2007. Performance standards for antimicrobial susceptibility testing; 17th informational supplement. CLSI/NCCLS M100-S17. Clinical and Laboratory Standards Institute, Wayne, PA.
3
3. Di Conza, J., J. A. Ayala, P. Power, M. Mollerach, and G. Gutkind. 2002. Novel class 1 integron (InS21) carrying bla_CTX-M-2 in Salmonella enterica serovar Infantis. Antimicrob. Agents Chemother. 46:2257-2261.[Abstract/Free Full Text]
4
4. Karisik, E., M. J. Ellington, R. Pike, R. E. Warren, D. M. Livermore, and N. Woodford. 2006. Molecular characterization of plasmids encoding CTX-M-15 beta-lactamases from Escherichia coli strains in the United Kingdom. J. Antimicrob. Chemother. 58:665-668.[Abstract/Free Full Text]
5
5. Kim, J., and Y. M. Lim. 2005. Prevalence of derepressed AmpC mutants and extended-spectrum β-lactamase producers among clinical isolates of Citrobacter freundii, Enterobacter spp., and Serratia marcescens in Korea: dissemination of CTX-M-3, TEM-52, and SHV-12. J. Clin. Microbiol. 43:2452-2455.[Abstract/Free Full Text]
6
6. Machado, E., T. M. Coque, R. Cantón, F. Baquero, J. C. Sousa, L. Peixe, and the Portuguese Resistance Study Group. 2006. Dissemination in Portugal of CTX-M-15-, OXA-1-, and TEM-1-producing Enterobacteriaceae strains containing the aac(6')-Ib-cr gene, which encodes an aminoglycoside- and fluoroquinolone-modifying enzyme. Antimicrob. Agents Chemother. 50:3220-3221.[Free Full Text]
7
7. Pallecchi, L., A. Bartoloni, C. Fiorelli, A. Mantella, T. Di Maggio, H. Gamboa, E. Gotuzzo, G. Kronvall, F. Paradisi, and G. M. Rossolini. 2007. Rapid dissemination and diversity of CTX-M extended-spectrum β-lactamase genes in commensal Escherichia coli isolates from healthy children from low-resource settings in Latin America. Antimicrob. Agents Chemother. 51:2720-2725.[Abstract/Free Full Text]
8
8. Park, C. H., A. Robicsek, G. A. Jacoby, D. Sahm, and D. C. Hooper. 2006. Prevalence in the United States of aac(6')-Ib-cr encoding a ciprofloxacin-modifying enzyme. Antimicrob. Agent Chemother. 50:3953-3955.[Abstract/Free Full Text]
9
9. Robicsek, A., J. Strahilevitz, G. A. Jacoby, M. Macielag, D. Abbanat, C. H. Park, K. Bush, and D. C. Hooper. 2006. Fluoroquinolone-modifying enzyme: a new adaptation of a common aminoglycoside acetyltransferase. Nat. Med. 12:83-88.[CrossRef][Medline]
10
10. Vignoli, R., E. Calvelo, N. F. Cordeiro, R. Lucero, E. Ingold, A. Quintana, A. del Monte, and F. Schelotto. 2006. Association of broad-spectrum antibiotic use with faecal carriage of oxyiminocephalosporin-resistant enterobacteriaceae in an intensive care unit. J. Hosp. Infect. 63:306-315.[CrossRef][Medline]
11
11. Vignoli, R., N. Cordeiro, V. Seija, F. Schelotto, M. Radice, J. Ayala, P. Power, and G. Gudkind. 2006. Genetic environment of CTX-M-2 in Klebsiella pneumoniae isolates from hospitalized patients in Uruguay. Rev. Arg. Microbiol. 38:84-88.

						Nicolás F. Cordeiro Luciana Robino Departamento de Bacteriología y Virología Instituto de Higiene Facultad de Medicina Universidad de la República 11600 Montevideo, Uruguay Julio Medina Unidad Cuidados Intensivos del Hospital de Clínicas Facultad de Medicina Montevideo, Uruguay Verónica Seija Departamento de Laboratorio Clínico Área Microbiología Hospital de Clínicas Facultad de Medicina Montevideo, Uruguay Inés Bado Virginia García Departamento de Bacteriología y Virología Instituto de Higiene Facultad de Medicina Universidad de la República 11600 Montevideo, Uruguay Maximiliano Berro Julio Pontet Lucía López Unidad Cuidados Intensivos del Hospital de Clínicas Facultad de Medicina Montevideo, Uruguay Cristina Bazet Departamento de Laboratorio Clínico Área Microbiología Hospital de Clínicas Facultad de Medicina Montevideo, Uruguay Gloria Rieppi Unidad Cuidados Intensivos del Hospital de Clínicas Facultad de Medicina Montevideo, Uruguay Gabriel Gutkind Cátedra de Microbiología Facultad de Farmacia y Bioquímica Universidad de Buenos Aires 1113 Buenos Aires, Argentina Juan A. Ayala Centro de Biología Molecular Severo Ochoa CSIC-UAM Campus de Cantoblanco 28049 Madrid, Spain Rafael Vignoli* Departamento de Bacteriología y Virología Instituto de Higiene Facultad de Medicina Universidad de la República Alfredo Navarro 3051 11600 Montevideo, Uruguay
						* Phone and fax: (598 2) 487 57 95 E-mail: rvignoli{at}higiene.edu.uy

---

Antimicrobial Agents and Chemotherapy, February 2008, p. 806-807, Vol. 52, No. 2
0066-4804/08/$08.00+0     doi:10.1128/AAC.00444-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Strahilevitz, J., Jacoby, G. A., Hooper, D. C., Robicsek, A. (2009). Plasmid-Mediated Quinolone Resistance: a Multifaceted Threat. Clin. Microbiol. Rev. 22: 664-689 [Abstract] [Full Text]  
• Kim, E. S., Jeong, J.-Y., Jun, J.-B., Choi, S.-H., Lee, S.-O., Kim, M.-N., Woo, J. H., Kim, Y. S. (2009). Prevalence of aac(6')-Ib-cr Encoding a Ciprofloxacin-Modifying Enzyme among Enterobacteriaceae Blood Isolates in Korea. Antimicrob. Agents Chemother. 53: 2643-2645 [Abstract] [Full Text]  
• Jacoby, G. A., Gacharna, N., Black, T. A., Miller, G. H., Hooper, D. C. (2009). Temporal Appearance of Plasmid-Mediated Quinolone Resistance Genes. Antimicrob. Agents Chemother. 53: 1665-1666 [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Cordeiro, N. F. Articles by Vignoli, R. Search for Related Content PubMed PubMed Citation Articles by Cordeiro, N. F. Articles by Vignoli, R.