The Emergence of Antimicrobial Resistance and Virulence Characteristics in <i>Enterococcus</i> Species Isolated from Bovine Milk

• Main Authors: Beatriz Rizzo Paschoalini (Author), Karen Vanessa Munive Nuñez (Author), Juliana Takahashi Maffei (Author), Hélio Langoni (Author), Felipe Freitas Guimarães (Author), Clarice Gebara (Author), Natylane Eufransino Freitas (Author), Marcos Veiga dos Santos (Author), Carlos Eduardo Fidelis (Author), Roberto Kappes (Author), Mônica Correia Gonçalves (Author), Nathália Cristina Cirone Silva (Author)
• Format: Book
• Published: MDPI AG, 2023-07-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/antibiotics12081243; 2079-6382
• Keywords: <i>E. faecium</i>; <i>E. faecalis</i>; Vancomycin-resistant enterococci (VRE); virulence factors; Therapeutics. Pharmacology; RM1-950
• Source: Antibiotics, Vol 12, Iss 8, p 1243 (2023)

<i>Enterococcus</i> spp., including <i>E. faecalis</i> and <i>E. faecium</i>, pose risks to dairy farms as opportunistic pathogens. The study evaluates antimicrobial resistance (AMR) and virulence characteristics of <i>Enterococcus</i> spp. isolated from bovine milk. Bile esculin agar was used to assess 1471 milk samples, followed by colony identification, gram staining, catalase tests, and 45 °C incubation. PCR analysis targeted <i>E. faecalis</i> and <i>E. faecium</i> in characteristic <i>Enterococcus</i> spp. colonies, with MALDI-TOF used for negative samples. Multiple tests, including disk diffusion, chromogenic VRE agar for vancomycin resistance, Vancomycin Etest^® for MIC determination, and PCR for virulence factors (<i>cyl</i>A, <i>esp</i>, <i>efa</i>A, <i>ace</i>, <i>asa</i>1, <i>gel</i>E, and <i>hyl</i> genes), were performed. Out of 100 identified strains, <i>E. durans</i> (30.66%), <i>E. faecium</i> (26.28%), and <i>E. faecalis</i> (18.25%) were predominant. AMR in <i>Enterococcus</i> spp. varied, with the highest rates against rifampicin (27%), tetracycline (20%), and erythromycin (18%). Linezolid (5%), vancomycin, ciprofloxacin, and teicoplanin (3% each) had lower prevalence. <i>E. faecium</i> and <i>E. faecalis</i> showed high AMR to rifampicin, erythromycin, and tetracycline. Thirty-two strains (18.98%) grew on VRE Chromoselect agar, while 4 (2 <i>E. faecalis</i> and 2 <i>E. faecium</i>) showed vancomycin resistance by MIC values. <i>E. faecalis</i> carried <i>gel</i>E (45.5%) and <i>asa</i>1 (36%), and <i>E. gallinarum</i> had 9.1% with the <i>asa</i>1 gene. Detecting resistant <i>Enterococcus</i> in bovine milk supports control strategies for enterococci on dairy farms, highlighting AMR concerns in the food chain.