Molecular characterization of florfenicol and oxazolidinone resistance in Enterococcus isolates from animals in China

Pingping Li; Mengdi Gao; Chunlin Feng; Tielun Yan; Zhiqiong Sheng; Weina Shi; Shuang Liu; Lei Zhang; Anqi Li; Junwan Lu; Xi Lin; Kewei Li; Teng Xu; Qiyu Bao; Caixia Sun

doi:10.3389/fmicb.2022.811692

Molecular characterization of florfenicol and oxazolidinone resistance in Enterococcus isolates from animals in China

Front Microbiol. 2022 Jul 26:13:811692. doi: 10.3389/fmicb.2022.811692. eCollection 2022.

Authors

Pingping Li^{1

2

3

4}, Mengdi Gao^{1

3}, Chunlin Feng^{1

3}, Tielun Yan^{1

3}, Zhiqiong Sheng⁵, Weina Shi^{1

3}, Shuang Liu^{1

3}, Lei Zhang^{1

3}, Anqi Li^{1

3}, Junwan Lu^{1

3}, Xi Lin^{1

3}, Kewei Li^{1

3}, Teng Xu⁶, Qiyu Bao^{1

3}, Caixia Sun^{2

3}

Affiliations

¹ Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China.
² Nursing Department, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China.
³ Institute of Biomedical Informatics, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China.
⁴ Department of Clinical Laboratory, Zhoukou Maternal and Child Health Hospital, Zhoukou, China.
⁵ School of Nursing, Wenzhou Medical University, Wenzhou, China.
⁶ Institute of Translational Medicine, Baotou Central Hospital, Baotou, China.

Abstract

Florfenicol is widely used for the treatment of bacterial infections in domestic animals. The aim of this study was to analyze the molecular mechanisms of florfenicol and oxazolidinone resistance in Enterococcus isolates from anal feces of domestic animals. The minimum inhibitory concentration (MIC) levels were determined by the agar dilution method. Polymerase chain reaction (PCR) was performed to analyze the distribution of the resistance genes. Whole-genome sequencing and comparative plasmid analysis was conducted to analyze the resistance gene environment. A total of 351 non-duplicated enteric strains were obtained. Among these isolates, 22 Enterococcus isolates, including 19 Enterococcus. faecium and 3 Enterococcus. faecalis, were further studied. 31 florfenicol resistance genes (13 fexA, 3 fexB, 12 optrA, and 3 poxtA genes) were identified in 15 of the 19 E. faecium isolates, and no florfenicol or oxazolidinone resistance genes were identified in 3 E. faecalis isolates. Whole-genome sequencing of E. faecium P47, which had all four florfenicol and oxazolidinone resistance genes and high MIC levels for both florfenicol (256 mg/L) and linezolid (8 mg/L), revealed that it contained a chromosome and 3 plasmids (pP47-27, pP47-61, and pP47-180). The four florfenicol and oxazolidinone resistance genes were all related to the insertion sequences IS1216 and located on two smaller plasmids. The genes fexB and poxtA encoded in pP47-27, while fexA and optrA encoded in the conjugative plasmid pP47-61. Comparative analysis of homologous plasmids revealed that the sequences with high identities were plasmid sequences from various Enterococcus species except for the Tn6349 sequence from a Staphylococcus aureus chromosome (MH746818.1). The current study revealed that florfenicol and oxazolidinone resistance genes (fexA, fexB, poxtA, and optrA) were widely distributed in Enterococcus isolates from animal in China. The mobile genetic elements, including the insertion sequences and conjugative plasmid, played an important role in the horizontal transfer of florfenicol and oxazolidinone resistance.

Keywords: Enterococcus; IS1216; fexA; fexB; florfenicol; optrA; oxazolidinone; poxtA.