Abstract
Th e aim of this study was to describe the prevalence of antibiotic resistance to some aminoglycosides, streptomycin, spectinomycin and gentamicinand three aminoglycoside- resistance genes in Escherichia coli isolated from feces and lagoon manure in six swine farms in Republic of Bulgaria. Atotal of 274 E. coli isolates from 270 fecal samples and twelve samples from lagoon manure were tested by disk diff usion method to determine resistance patterns to 11 antimicrobial agents. Aminoglycosides resistance also was determined by E-test, agar dilution method, PCR and qPCR. Th e highest resistance observed to streptomycin (70.0%) and spectinomycin (65.5%). Multi-resistance patterns in studied E. coli strains showed that the resistance to streptomycin/spectinomycin was most frequently seen together with resistance to ampicillin, tetracycline, and sulfonamides (39.6%). The E. coli isolates resistant to streptomycin, spectinomycin were examined for the presence of strA/strB, aadA1 genes, and resistant isolates to gentamicin were evaluated for the presence of the aacC1 gene. Th e most common gene determining resistance to aminoglycosides was aadA1 which was found in 54.0% of swine isolates and lagoon manure isolates followed by straA/strB genes (32.3%). Th e aacC1gene was not identifi ed in E. coli isolates resistant to gentamicin.
Highlights
The concept of EMA (2014) on the use of aminoglycosides in livestock and companion animals in the EU, development of resistance and public health risks is grounded on data about the increasing resistance to aminoglycosides in animal and human bacterial isolates
From modifying enzymes coding for resistance to gentamicin in E. coli strains from livestock, adenyltransferase ACC(3) – IV whose production is coded by the аас3-IV gene and that determines a combined resistance to gentamicin and apramycin, is of special interest
Determination of the sensitivity of E. coli isolates to antibiotics The sensitivity of E. coli isolates to 11 chemotherapeutics was evaluated by the disk diffusion method as per CLSI, using Muller-Hinton agar (Emapol, Poland) and antibiotic disks (Emapol, Poland), loaded as followed: ampicillin (10 μg), amoxicillin/clavulanic acid (20/10 μg), cephalotin (30 μg), ceftazidime (10 μg), cefotaxime (30 μg), gentamicin (10 μg), streptomycin (10 μg), spectinomycin (25 μg), tetracycline (30 μg), ciprofloxacin (5 μg), sulfamethoxazole (25 μg)
Summary
The concept of EMA (2014) on the use of aminoglycosides in livestock and companion animals in the EU, development of resistance and public health risks is grounded on data about the increasing resistance to aminoglycosides in animal and human bacterial isolates. From modifying enzymes coding for resistance to gentamicin in E. coli strains from livestock, adenyltransferase ACC(3) – IV whose production is coded by the аас3-IV gene and that determines a combined resistance to gentamicin and apramycin, is of special interest. There are data, limited, on the prevalence of аасС1 and аас3-II genes in domestic animals (Guerra et al, 2003; Sãenz et al, 2004). These genes determine the production of acetyltransferases АСС (3)- I and ААС (3)-II, distinguished with their phenotype profile, which for the latter gene includes resistance to tobramycin apart to gentamicin (Vaculenko and Mobashery, 2003)
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