Characteristics of High-Level Aminoglycoside-Resistant Enterococcus faecalis Isolated from Bulk Tank Milk in Korea

Abstract

Enterococci, which are considered environmental mastitis-causing pathogens, have easily acquired aminoglycoside-resistant genes that encode various aminoglycoside-modifying enzymes (AME). Therefore, this study was conducted to compare the distribution of high-level aminoglycoside-resistant (HLAR) and multidrug-resistant (MDR) Enterococcus faecalis (E. faecalis) bacteria isolated from bulk tank milk in four dairy companies in Korea. Moreover, it analyzed the characteristics of their antimicrobial resistance genes and virulence factors. Among the 301 E. faecalis bacteria studied, 185 (61.5%) showed HLAR with no significant differences among the dairy companies. Furthermore, 129 (69.7%) of the 185 HLAR E. faecalis showed MDR without significant differences among companies. In contrast, HLAR E. faecalis from companies A, B, and C were significantly higher in resistance to the four classes than those in company D, which had the highest MDR ability against the three antimicrobial classes (p < 0.05). In addition, in the distribution of AME genes, 72 (38.9%) and 36 (19.5%) of the isolates carried both aac(6′)Ie-aph(2″)-la and ant(6)-Ia genes, and the ant (6)-Ia gene alone, respectively, with significant differences among the companies (p < 0.05). In the distribution of virulence genes, the ace (99.5%), efa A (98.9%), and cad 1 (98.4%) genes were significantly prevalent (p < 0.05). Thus, our results support that an advanced management program by companies is required to minimize the dissemination of antimicrobial resistance and virulence factors.

Safety evaluation of enterococci isolated from raw milk and artisanal cheeses made in Slovenia and Serbia

“…In contrast to our results, 59 high-level aminoglycoside resistant dairy enterococci were found to have aph(3 ′ )-IIIa (94.9%) as the most prevalent gene, but none of the isolates contained the aac(6 ′ )-Ie-aph(2 ′′ )-Ia gene (Özdemir and Tuncer, 2020). Kang et al (2021) demonstrated that 61.5% of E. faecalis isolates from bulk tank milk in Korea had HLAR, with 38.9% and 19.5% of isolates carrying both the aac(6 ′ )-Ie-aph(2 ′′ )-la and ant(6) genes, and the ant(6) gene alone, respectively.…”

Resistant enterococci isolated from raw sheep’s milk and cheeses from South region of Brazil

“…Strains were also not susceptible to quinolones (ciprofloxacin/norfloxacin) (12.2%; -------------------------------------------------------------------------Cheese (76)---------------------------------------------------------------------------- 4 (13.8) 22 (75.9) 0 2 (6.9) 1 (3.5) Feta-type ( 29 n=5), and chloramphenicol (7.3%; n=3) (Figure 1). Resistant enterococci have been isolated from the raw milk of cows, goats, and buffalos around the world (PRICHULA et al, 2013;PALMERI et al, 2020;KANG et al, 2021). Ampicillin, erythromycin, gentamicin, and tetracycline resistant enterococci were isolated from raw sheep milk samples in Slovakia (DUCKOVÁ et al, 2009).…”

Antimicrobial Resistance in Veterinary Medicine and Public Health

“…Kang and colleagues [ 11 ] focused on environmental mastitis-causing enterococci as an emerging cause of nosocomial infections of relevance due to their antimicrobial resistance traits. The survey underlined a dramatically high proportion of the bulk tank milk-derived enterococci as the vector of resistance traits against single- and multi-antimicrobial drugs.…”