Effects of low-concentration erythromycin on protein expression, cross resistance and capsular polysaccharides of Streptococcus suis

Abstract:

[Objective] To explore the effects of low-concentration erythromycin on protein expression, cross resistance and capsular polysaccharide of Streptococcus suis, so as to lay a foundation for further studying the effects of low-concentration antibiotic growth promoters in feed on microorganisms in the environment. [Methods] After S.suis was exposed to low-concentration erythromycin, key differentially expressed proteins were screened by iTRAQ. At the same time, we measured the cross resistance of S.suis and the content of capsular polysaccharide.[Results] A total of 181 differentially expressed proteins were identified, accounting for 12% of the total identified proteins. In order to adapt to the selective pressure of erythromycin, S.suis changed the expression of its own proteome. Most differentially expressed proteins were involved in catalytic and metabolic processes, and they belonged to membrane proteins. Among them, 13 ATP-binding cassette transporters, 3 ribosomal proteins and DNA gyrase were up-regulated, while 8 capsular polysaccharide proteins and DNA polymerase Ⅳ were down-regulated. When S.suis was exposed to low-concentration erythromycin, it revealed cross resistance to a variety of antibiotics, whereas there was no significant change in the content of capsular polysaccharide. After elimination of erythromycin, the drug sensitivity recovered. [Conclusion] To adapt to the selective pressure of low-concentration erythromycin, S.suis up-regulated the expression of multidrug resistance efflux pumps to increase the levels of ribosomal protein and decrease the levels of capsular polysaccharide protein.