High level aminoglycoside resistance in Enterococcus, Pediococcus and Lactobacillus species from farm animals and commercial meat products

Abstract

Inappropriate use of aminoglycosides in animal husbandry has led to the selection and emergence of high-level aminoglycoside resistance (HLAR) in lactic acid bacteria (LAB). The objective of this study was to assess the presence of aminoglycoside resistant LAB in farm animals and meat products. Gentamicin resistant LAB (n = 138) were selectively isolated from 50 different meat and farm animal sources. These native isolates of LAB were subsequently characterized for their minimum inhibitory concentration to seven different aminoglycoside antibiotics. HLAR to gentamicin, kanamycin and streptomycin was found to be 38 %, 45 % and 15 %, respectively. Selected cultures of LAB were identified by random amplified polymorphic DNA (RAPD)-PCR and 16S rDNA gene sequencing. Subsequent detection for the presence of nine aminoglycoside modifying genes [aac(6′)Ie-aph(2″)Ia, aph(3′)IIIa, aad6, ant(6)Ia, ant(9)Ia, ant(9)Ib, aph(2″)Ib, aph(2″)Ic and aph(2″)Id] was carried out by PCR. The Enterococcus spp. (n = 64) and Lactobacillus plantarum (n = 6) isolated from farm animals and chicken sausages, respectively, were positive for the bifunctional gene, aac(6′)Ie-aph(2″)Ia in PCR. In addition, Enterococcus sp. (n = 17), Lactobacillus plantarum (n = 3), and Pediococcus lolii (n = 2) possessed the kanamycin resistance gene, aph(3′)IIIa. Other LAB viz. Enterococcus faecalis (n = 2), E. faecium (n = 2) and L. plantarum (n = 1) harbored the streptomycin resistance gene, aad6. The integrase (int) gene, characteristic to Tn 916-Tn 1545 was detected in Enterococcus faecalis CS11+ and Enterococcus cecorum I40a suggesting its involvement in antibiotic resistant gene transfer. Besides, strains of L. plantarum, a species used as probiotic, isolated in this study showed the occurrence of aph(3′)IIIa as well as aac (6′)Ie-aph(2″)Ia genes that could be of concern in human health. The findings of the study highlight the spread and emergence of multi-resistance genes for aminoglycoside antibiotics among beneficial LAB.