Antimicrobial Resistance of Enterococci Isolated from Mastitic Bovine Milk Samples in Korea

Abstract

The aim of this study was to determine the antimicrobial resistance of various species of enterococci isolated from mastitic bovine milk samples. A total of 105 enterococci isolates were examined: Enterococcus faecalis (n = 47), Enterococcus faecium (n = 39), Enterococcus gallinarum (n = 6), Enterococcus avium (n = 6), Enterococcus hirae (n = 5) and Enterococcus durans (n = 2). All the isolates were susceptible to ampicillin, gentamicin and vancomycin, and only a single E. hirae isolate was resistant to ampicillin. In general, the most frequently observed resistance among the enterococcal isolates was to tetracycline (69.5%), followed by penicillin (64.7%), erythromycin (57.1%) and cephalothin (44.7%). A similar antimicrobial resistance pattern was observed among individual species except E. durans, which exhibited only tetracycline resistance. Resistance observed among isolates of E. hirae and E. gallinarum was almost as high as E. faecium and E. faecalis. Of 105 isolates, only six (5.7%) strains of E. faecium were susceptible to all the antimicrobials tested and about 52% (55/105) showed resistance to more than three antimicrobials. The most common multiple resistance pattern was penicillin, tetracycline and erythromycin, which was observed in 32 of 105 (30.4%) isolates. This study demonstrates that enterococcal isolates belonging to minor species showed antimicrobial resistance rates as high as those of E. faecium and E. faecalis, and that monitoring of antimicrobial resistance should not be restricted only to those two major species.

Distribution of Antibiotic Resistance Genes in Enterococcus spp. Isolated from Mastitis Bovine Milk

“…Findings about resistance to important antibiotics from isolated enterococci in our study were mostly found compatible with previously published results [22,23,25]. Resistance rates of tested antibiotics were low except for tetracycline and the encountered genes were resistance genes that normally exist in enterococci.…”

“…The E. faecium was detected in 21.3% of the samples. Obtained results are similar to other studies on the prevalence of Enterococcus in milk from cows with mastitis [19][20][21][22].…”

“…In a study carried out by Nam et al [22], all of the 105 Enterococcus isolates were found susceptible to ampicillin, gentamycin and vancomycin, but resistance to tetracycline was described at a rate of 69.5%. Multiple drug resistance was observed in 30.4% of all strains with penicillin, tetracycline and erythromycin.…”

Distribution of Multidrug Efflux Pump Genes in Enterococci spp. Isolated from Bovine Milk Samples and Their Antibiotic Resistance Patterns

“…본 연구 결과 장알균의 erythromycin과 tetracycline에 대한 내성균의 비율이 79.2%와 76.3%로 높게 나 타났으며 이러한 결과는 다른 국내, 외 다른 연구 결과와도 유사 한 경향을 보이고 있음을 알 수 있으며 (Mannu et al, 2003;Kwon et al, 2007;Jeong et al, 2008;Nam et al, 2009) 우리나 라 축산물 유래 장알균의 erythromycin과 tetracycline에 대한 내 성비율이 높음을 알 수 있었다( Table 2).…”

Antibiotic resistance genes and virulence factors in Enterococcus faecium and Enterococcus faecalis from diseased farm animals: pigs, cattle and poultry

“…Nevertheless, enterococci have been implicated in a number of infections in animals, mainly mastitis in cattle, diarrhea in swine and cattle, as well as endocarditis and Correspondence to: V. Šeputienė, e-mail: vaida.seputiene@gf.vu.lt, tel. : +370 5 2398233 septicaemia in poultry (Ok et al 2009, Bisgaard et al 2010, Nam et al 2010. Animal (mouse, rat, rabbit) models have been used for enterococci urinary tract infection and endocarditis studies (Singh et al 2009, Thurlow et al 2010.…”