Comparative Analysis of Chloramphenicol-Resistant Enterococcus faecalis Isolated from Dairy Companies in Korea.

Sung Hyun Bae,Yeong Bin Kim,Koeun Kim,Young Ju Lee,Sunghyun Yoon

doi:10.3390/vetsci8080143

Abstract

Although chloramphenicol is currently banned from use in livestock, other phenicols, such as florfenicol and thiamphenicol, have been used for the treatment of bacterial infections in domestic cattle in Korea. This study compares the characteristics of chloramphenicol-resistant Enterococcus faecalis isolated from the bulk tank milk of four major dairy companies in Korea. Although the distribution of multidrug resistance patterns showed no significant differences between the four companies, 85 chloramphenicol-resistant Enterococcus faecalis isolates showed a significantly high number of resistances against five or six antimicrobial classes (37.6%, respectively) (p < 0.05). When analyzing the distribution of phenicol resistance genes, 31 (36.5%) isolates only carried the catA gene, and two (6.3%) isolates from company A only carried the cfr gene. No isolates carried the catB or fexA genes. Regarding the distribution of other resistance genes, both the tetL and tetM (45.9%), ermB (82.4%), and both aac(6″)-Ie-aph(2″)-la and ant(6′)-Ia genes (30.6%) showed a high prevalence, and the optrA and poxtA genes were observed separately, each in only two (2.4%) isolates. Our results confirm that the dissemination of chloramphenicol-resistant Enterococcus faecalis and some antimicrobial resistance genes show significant differences between dairy companies. Therefore, our results support that each dairy company should undertake effective surveillance programs to better understand and minimize the emergence of resistance on a multidisciplinary level.

Highlights

Chloramphenicol, a broad-spectrum antimicrobial in human and veterinary medicine in use since the 1950s [1], inhibits translation in bacteria, by inhibiting peptidyl transferase activity, which is mediated by binding to several proteins in the 50S ribosomal subunit [2].since chloramphenicol has been shown to cause serious bone marrow suppression and fetal aplastic anemia [1,3], its use in humans and animals has been subsequently limited
Among the 301 E. faecalis isolates, 85 (28.2%) chloramphenicol-resistant E. faecalis isolates were found among the four dairy companies (Table 1)
Florfenicol is commonly recommended for the treatment of bacterial pneumonia and associated respiratory infections caused by Haemophilus somnus, Mannheimia (Pasteurella) haemolytica, and Pasteurella multocida in cattle [37]

Summary

Introduction

Since chloramphenicol has been shown to cause serious bone marrow suppression and fetal aplastic anemia [1,3], its use in humans and animals has been subsequently limited. It is currently banned from use in food-producing animals in many countries and regions, including the European Union [1], China [4], the United States [5], and Korea [6]. Enterococci are known as a genus of gut-equivalent microorganisms commonly found in animals and humans, but considered to be environmental mastitis-causing pathogens that can enter into milk and milk products via unhygienic food production and handling conditions [7,8,9]. Resistance to chloramphenicol is mainly caused by the production of inactivating chloramphenicol acetyltransferase (CAT) [1], the genes of which are widely disseminated on plasmids and capable of contributing to multidrug resistance (MDR)

Methods

Discussion

Conclusion