Characterization of florfenicol resistance genes in the coagulase-negative Staphylococcus  (CoNS) isolates and genomic features of  a  multidrug-resistant Staphylococcus lentus strain H29

Abstract

BackgroundWith the wide use of florfenicol to prevent and treat the bacterial infection of domestic animals, the emergence of the florfenicol resistance bacteria is increasingly serious. It is very important to elucidate the molecular mechanism of the bacteria’s resistance to florfenicol. MethodsThe minimum inhibitory concentration (MIC) levels was determined by the agar dilution method, and polymerase chain reaction (PCR) was conducted to analyze the distribution of florfenicol resistance genes in 39 CoNS strains isolated from poultry and livestock animals and seafood. The whole genome sequence of one multidrug-resistant strain, Staphylococcus lentus H29, was characterized, and comparative genomics analysis of the resistance gene-related sequences was also performed. ResultsAs a result, the isolates from the animals showed a higher resistance rate (23/28, 82.1%) and much higher MIC levels of florfenicol than those from seafood. Twenty-seven animal isolates carried 37 florfenicol resistance genes (including 26 fexA , 6 cfr and 5 fexB genes), of which 1 carried a cfr gene, 16 carried a fexA gene, 5 carried both fexA and fexB genes and 5 carried both fexA and cfr genes. On the other hand, all 11 isolates from seafood were sensitive to florfenicol, and only 3 carried a fexA gene each. The whole genome sequence of S. lentus H29 was composed of a chromosome and two plasmids ( pH29-46 , pH29- 26) and harbored 11 resistance genes, including 6 genes [ cfr, fexA, ant(6)-Ia , aac A -aph D , mecA and mph(C) ] encoded on the chromosome, four genes [ cfr, fexA, aac A -aph D and tcaA ] on pH29-46 and one gene ( fosD ) on pH29-26. It was interested to find that the S. lentus H29 genome carried two identical copies of the gene arrays of radC - tnpABC - hp - fexA (5,671 bp) and IS 256 - cfr (2,690 bp), of which one copy of the two gene arrays was encoded on plasmid pH29-46, while the other was encoded on the chromosome. ConclusionsThe current study revealed the wide distribution of florfenicol resistance genes ( cfr, fexA and fexB ) in animal bacteria, and to the best of our knowledge, this is the first report of one CoNS strain carrying two identical copies of florfenicol resistance-related gene arrays.

Molecular epidemiology and characterization of antimicrobial-resistant Staphylococcus haemolyticus strains isolated from dairy cattle milk in Northwest, China

“…Previously, Qian et al (2015) reported that blactam antimicrobial agents such as penicillin, cephalosporin, and monobactams were extensively used for the treatment of bovine mastitis caused by Staphylococcus species. Among the amphenicol ARGs, only the floR gene was harbored by S. haemolyticus strains, which is in accordance with the previously published study by Wu et al (2021). Florfenicol is one of the most commonly used antimicrobials in the dairy sector because of its wide range of antimicrobial activity (Kawalek et al, 2016).…”

“…NAS is one of the most important and widespread groups of pathogens including numerous species such as S. chromogenes, S. haemolyticus, S. sciuri, S. saprophyticus, S. simulans, S. succinus, and S. epidermidis (Wald et al, 2019). NAS pathogens are not only opportunistic in animals and humans but are also widely distributed in the environment such as dust, soil, water, and air (Wu et al, 2021). Although NAS species are considered to be a pathogen of low clinical incidence, it has recently been identified as the relatively common causative agent of bovine mastitis in many countries including China (Al-Harbi et al, 2021).…”