Detection of antibiotic resistance profiles and aminoglycoside-modifying enzyme (AME) genes in high-level aminoglycoside-resistant (HLAR) enterococci isolated from raw milk and traditional cheeses in Turkey


Molecular Biology Reports, vol.47, no.3, pp.1703-1712, 2020 (Peer-Reviewed Journal) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 47 Issue: 3
  • Publication Date: 2020
  • Doi Number: 10.1007/s11033-020-05262-4
  • Journal Name: Molecular Biology Reports
  • Journal Indexes: Science Citation Index Expanded, Scopus, Aquatic Science & Fisheries Abstracts (ASFA), BIOSIS, CAB Abstracts, Chemical Abstracts Core, EMBASE, MEDLINE, Veterinary Science Database
  • Page Numbers: pp.1703-1712
  • Keywords: High-level aminoglycoside resistance, Enterococcus, Raw milk, Cheese, Aminoglycoside-modifying enzymes, aph(3MODIFIER LETTER PRIME)-IIIa, LACTIC-ACID BACTERIA, MOLECULAR CHARACTERIZATION, VIRULENCE GENES, MULTIPLEX PCR, PREVALENCE, FAECALIS, STRAINS, FAECIUM, FOOD, IDENTIFICATION


The aim of this study was isolation and identification of the high-level aminoglycoside-resistant (HLAR) enterococci in raw milk and dairy products and to analyze their antibiotic resistance and the presence of aminoglycoside-modifying enzyme (AME) genes. A total of 59 HLAR enterococci were isolated from raw milk and traditional cheese samples. Thirty-nine of the 59 HLAR enterococci were isolated on streptomycin-containing agar medium, while the other 20 HLAR strains were isolated on gentamicin containing agar medium. The 59 HLAR enterococci were identified as 26 E. faecalis (44.07%), 18 E. faecium (30.51%), 13 E. durans (22.03%), and two E. gallinarum (3.39%) by species-specific PCR. Disk diffusion tests showed that teicoplanin were the most effective antibiotics used in this study, while 89.83% of isolates were found to be resistant to tetracycline. High rates of multiple antibiotic resistance were detected in HLAR isolates. Minimum inhibitory concentration (MIC) values of HLAR enterococci against streptomycin and gentamicin were found in the range of 64 to > 4096 mu g/mL. Forty-seven (79.66%) of the 59 HLAR enterococci were found to be both high-level streptomycin-resistant (HLSR) and high-level gentamicin-resistant (HLGR) by MIC tests. However, no correlation was found between the results of the disk diffusion and MIC tests for gentamicin and streptomycin in some HLAR strains. The aph(3MODIFIER LETTER PRIME)-IIIa (94.92%) was found to be most prevalent AME gene followed by ant(4MODIFIER LETTER PRIME)-Ia (45.76%), ant(6MODIFIER LETTER PRIME)-Ia (20.34%) and aph(2MODIFIER LETTER PRIMEMODIFIER LETTER PRIME)-Ic (10.17%). None of the isolates contained the aac(6MODIFIER LETTER PRIME)-Ie-aph(2MODIFIER LETTER PRIMEMODIFIER LETTER PRIME)-Ia, aph(2MODIFIER LETTER PRIMEMODIFIER LETTER PRIME)-Ib or aph(2MODIFIER LETTER PRIMEMODIFIER LETTER PRIME)-Id genes. None of the AME-encoding genes were identified in E. durans RG20.1, E. faecalis RG22.4, or RG26.1. In conclusion, HLAR enterococci strains isolated in this study may act as reservoirs in the dissemination of antibiotic resistance genes.