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QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India.
Indian J Med Res 2011; 134:214-23IJ

Abstract

BACKGROUND & OBJECTIVES

Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to several antimicrobials in a diarrhoea outbreak at Ahmedabad during 2000. The present study was done to identify several genes responsible for antimicrobial resistance and mobile genetic elements in the ETEC strains.

METHODS

Seventeen ETEC strains isolated from diarrhoeal patients were included in this study. The antimicrobial resistance was confirmed by conventional disc diffusion method. PCR and DNA sequencing were performed for the identification of mutation in the quinolone resistance-determining regions (QRDRs). Efflux pump was tested by inhibiting the proton-motive force. DNA hybridization assay was made for the detection of integrase genes and the resistance gene cassettes were identified by direct sequencing of the PCR amplicons.

RESULTS

Majority of the ETEC had GyrA mutations at codons 83 and 87 and in ParC at codon 80. Six strains had an additional mutation in ParC at codon 108 and two had at position 84. Plasmid-borne qnr gene alleles that encode quinolone resistance were not detected but the newly described aac(6')-Ib-cr gene encoding a fluoroquinolne-modifying enzyme was detected in 64.7 per cent of the ETEC. Class 1 (intI1) and class 2 (intI2) integrons were detected in six (35.3%) and three (17.6%) strains, respectively. Four strains (23.5%) had both the classes of integrons. Sequence analysis revealed presence of dfrA17, aadA1, aadA5 in class 1, and dfrA1, sat1, aadA1 in class 2 integrons. In addition, the other resistance genes such as tet gene alleles (94.1%), catAI (70.6%), strA (58.8%), bla TEM-1 (35.2%), and aphA1-Ia (29.4%) were detected in most of the strains.

INTERPRETATION & CONCLUSIONS

Innate gene mutations and acquisition of multidrug resistance genes through mobile genetic elements might have contributed to the emergence of multidrug resistance (MDR) in ETEC. This study reinforces the necessity of utilizing molecular techniques in the epidemiological studies to understand the nature of resistance responsible for antimicrobial resistance in different species of pathogenic bacteria.

Authors+Show Affiliations

National Institute of Cholera & Enteric Diseases (ICMR), Kolkata, India.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

21911975

Citation

Pazhani, G P., et al. "QRDR Mutations, Efflux System & Antimicrobial Resistance Genes in Enterotoxigenic Escherichia Coli Isolated From an Outbreak of Diarrhoea in Ahmedabad, India." The Indian Journal of Medical Research, vol. 134, 2011, pp. 214-23.
Pazhani GP, Chakraborty S, Fujihara K, et al. QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India. Indian J Med Res. 2011;134:214-23.
Pazhani, G. P., Chakraborty, S., Fujihara, K., Yamasaki, S., Ghosh, A., Nair, G. B., & Ramamurthy, T. (2011). QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India. The Indian Journal of Medical Research, 134, pp. 214-23.
Pazhani GP, et al. QRDR Mutations, Efflux System & Antimicrobial Resistance Genes in Enterotoxigenic Escherichia Coli Isolated From an Outbreak of Diarrhoea in Ahmedabad, India. Indian J Med Res. 2011;134:214-23. PubMed PMID: 21911975.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - QRDR mutations, efflux system & antimicrobial resistance genes in enterotoxigenic Escherichia coli isolated from an outbreak of diarrhoea in Ahmedabad, India. AU - Pazhani,G P, AU - Chakraborty,S, AU - Fujihara,K, AU - Yamasaki,S, AU - Ghosh,A, AU - Nair,G B, AU - Ramamurthy,T, PY - 2011/9/14/entrez PY - 2011/9/14/pubmed PY - 2012/1/20/medline SP - 214 EP - 23 JF - The Indian journal of medical research JO - Indian J. Med. Res. VL - 134 N2 - BACKGROUND & OBJECTIVES: Diverse mechanisms have been identified in enteric bacteria for their adaptation and survival against multiple classes of antimicrobial agents. Resistance of bacteria to the most effective fluoroquinolones have increasingly been reported in many countries. We have identified that most of the enterotoxigenic Escherichia coli (ETEC) were resistant to several antimicrobials in a diarrhoea outbreak at Ahmedabad during 2000. The present study was done to identify several genes responsible for antimicrobial resistance and mobile genetic elements in the ETEC strains. METHODS: Seventeen ETEC strains isolated from diarrhoeal patients were included in this study. The antimicrobial resistance was confirmed by conventional disc diffusion method. PCR and DNA sequencing were performed for the identification of mutation in the quinolone resistance-determining regions (QRDRs). Efflux pump was tested by inhibiting the proton-motive force. DNA hybridization assay was made for the detection of integrase genes and the resistance gene cassettes were identified by direct sequencing of the PCR amplicons. RESULTS: Majority of the ETEC had GyrA mutations at codons 83 and 87 and in ParC at codon 80. Six strains had an additional mutation in ParC at codon 108 and two had at position 84. Plasmid-borne qnr gene alleles that encode quinolone resistance were not detected but the newly described aac(6')-Ib-cr gene encoding a fluoroquinolne-modifying enzyme was detected in 64.7 per cent of the ETEC. Class 1 (intI1) and class 2 (intI2) integrons were detected in six (35.3%) and three (17.6%) strains, respectively. Four strains (23.5%) had both the classes of integrons. Sequence analysis revealed presence of dfrA17, aadA1, aadA5 in class 1, and dfrA1, sat1, aadA1 in class 2 integrons. In addition, the other resistance genes such as tet gene alleles (94.1%), catAI (70.6%), strA (58.8%), bla TEM-1 (35.2%), and aphA1-Ia (29.4%) were detected in most of the strains. INTERPRETATION & CONCLUSIONS: Innate gene mutations and acquisition of multidrug resistance genes through mobile genetic elements might have contributed to the emergence of multidrug resistance (MDR) in ETEC. This study reinforces the necessity of utilizing molecular techniques in the epidemiological studies to understand the nature of resistance responsible for antimicrobial resistance in different species of pathogenic bacteria. SN - 0971-5916 UR - https://www.unboundmedicine.com/medline/citation/21911975/QRDR_mutations_efflux_system_&_antimicrobial_resistance_genes_in_enterotoxigenic_Escherichia_coli_isolated_from_an_outbreak_of_diarrhoea_in_Ahmedabad_India_ L2 - http://www.ijmr.org.in/article.asp?issn=0971-5916;year=2011;volume=134;issue=2;spage=214;epage=223;aulast=Pazhani DB - PRIME DP - Unbound Medicine ER -