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Conjugal transfer of aac(6′)Ie-aph(2″)Ia gene from native species and mechanism of regulation and cross resistance in Enterococcus faecalis MCC3063 by real time-PCR.

Jaimee, George and Prakash, M. Halami (2017) Conjugal transfer of aac(6′)Ie-aph(2″)Ia gene from native species and mechanism of regulation and cross resistance in Enterococcus faecalis MCC3063 by real time-PCR. Microbial Pathogenesis, 110. pp. 546-553.

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Abstract

High level aminoglycoside resistance (HLAR) in the lactic acid bacteria (LAB) derived from food animals is detrimental. The aim of this study was to investigate the localization and conjugal transfer of aminoglycoside resistance genes, aac(6')Ie-aph(2″)Ia and aph(3')IIIa in different Enterococcus species. The cross resistance patterns in Enterococcus faecalis MCC3063 to clinically important aminoglycosides by real time PCR were also studied. Southern hybridization experiments revealed the presence of aac(6')Ie-aph(2″)Ia and aph(3')IIIa genes conferring HLAR in high molecular weight plasmids except in Lactobacillus plantarum. The plasmid encoded bifunctional aac(6')Ie-aph(2″)Ia gene was transferable from Enterococcus avium (n = 2), E. cecorum (n = 1), E. faecalis (n = 1) and Pediococcus lolii (n = 1) species into the recipient strain; E. faecalis JH2-2 by filter mating experiments thus indicating the possible risks of gene transfer into pathogenic strains. Molecular analysis of cross resistance patterns in native isolate of E. faecalis MCC3063 carrying aac(6')Ie-aph(2″)Ia and aph(3')IIIa gene was displayed by quantification of the mRNA levels in this study. For this, the culture was induced with increasing concentrations of gentamicin, kanamycin and streptomycin (2048, 4096, 8192, 16384 μg/mL) individually. The increasing concentrations of gentamicin and kanamycin induced the expression of the aac(6')Ie-aph(2″)Ia and aph(3')IIIa resistance genes, respectively. Interestingly, it was observed that induction with streptomycin triggered a significant fold increase in the expression of the aph(3')IIIa gene which otherwise was not known to modify the aminoglycoside. This is noteworthy as streptomycin was found to confer cross resistance to structurally unrelated kanamycin. Also, expression of the aph(3')IIIa gene when induced with streptomycin, revealed that bacteria harbouring this gene will be able to overcome streptomycin bactericidal action at specific concentrations. HLAR in E. faecalis MCC3063 may be due to the combined expression of both the aac(6')Ie-aph(2″)Ia and aph(3')IIIa genes which could be therapeutically challenging. A combined expression of both the genes in E. faecalis MCC3063 may yield HLAR which could be therapeutically challenging. The study highlights the significant alterations in the mRNA expression levels of aac(6')Ie-aph(2″)Ia and aph(3')IIIa in resistant pathogens, upon exposure to clinically vital aminoglycosides.

Item Type: Article
Uncontrolled Keywords: AminoGlycoside; Conjugal transfer; Cross resistance; High level aminoglycoside resistance (HLAR); Real time; mRNA expression
Subjects: 500 Natural Sciences and Mathematics > 07 Life Sciences > 04 Microbiology > 02 Bacteriology
600 Technology > 08 Food technology > 16 Nutritive value > 02 Amino acids
Divisions: Food Microbiology
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 18 Jan 2018 08:27
Last Modified: 18 Jan 2018 08:27
URI: http://ir.cftri.com/id/eprint/13312

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