Acta Veterinaria et Zootechnica Sinica ›› 2022, Vol. 53 ›› Issue (1): 290-303.doi: 10.11843/j.issn.0366-6964.2022.01.029

• BASIC VETERINARY MEDICINE • Previous Articles     Next Articles

Effects of Prophage on Virulence, Environmental Adaptability, Drug Resistance and Metabolic Activity of Streptococcus suis

HAN Xuejiao1, LI Liang1, ZHAN Songhe2, DUAN Qianqian1, CUI Lirong1, LIU Xuelan1, SUN Pei1, WEI Jianzhong1, LI Yu1*   

  1. 1. College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, China;
    2. Anhui Animal Disease Prevention and Control Center, Hefei 230091, China
  • Received:2021-04-23 Online:2022-01-23 Published:2022-01-26

Abstract: To understand and master the relationship between prophage and virulence, environmental adaptability, drug resistance and metabolic activity of Streptococcus suis (SS), in this study, the pathogenicity test, LD50 test, the number of bacteria loaded in tissue, histopathological observation, biofilm formation(BF) ability test, drug sensitivity test and transcriptome sequencing were carried out for the prophage positive strains (positive bacteria for short) and prophage negative strain(negative bacteria for short). The results showed that among 39 strains of positive bacteria and 7 strains of negative bacteria, 11 strains and 2 strains of bacteria had a lethal rate of more than 80.0%, The LD50 of 11 positive bacteria ranged from 8.4×108 to 2.36×109CFU·piece-1, and that of 2 negative bacteria were 1.88×109 and 2.72×109 CFU·piece-1, respectively. There was no significant difference in LD50 between positive and negative bacteria (P>0.05). After being challenged with positive bacteria with LD50 of 8.4×108CFU·piece-1, the number of bacteria in the organs (lung, liver, spleen, kidney, heart and brain) of mice was the most, and the pathological changes were the most obvious, after being challenged with the negative bacteria with LD50 of 2.72×109CFU·piece-1, the number of bacteria in each organ tissue of mice was the least, and the pathological changes were the least; The positive rate of BF formation was 97.4% for positive bacteria and 100.0% for negative bacteria; Both positive and negative bacteria showed multiple drug resistance to tetracycline, erythromycin, clindamycin, azithromycin, ceftriaxone and doxycycline, and there was no significant difference in drug resistance between them (P>0.05); Compared with positive bacteria, virulence related genes, BF formation related genes, drug resistance genes, fatty acid biosynthesis pathway and arginine and proline metabolism pathway related genes were up-regulated in negative bacteria. the results showed that there was no significant correlation between the presence or absence of prophage and the increase or decrease of SS virulence, high or low drug resistance and BF formation ability; However, the presence of prophage will lead to the down-regulation of genes associated with SS fatty acid biosynthesis and arginine and proline metabolism, resulting in the reduction of fatty acid and amino acid metabolism.

Key words: Streptococcus suis, prophage, virulence, drug resistance, environmental adaptability

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