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

Inappropriate use of aminoglycosides in animal
husbandry has led to the selection and emergence of highlevel
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.