Shujie Wang,Defu Zhang,Chenggang Jiang,Haijuan He,Chenchen Cui,Weitong Duan,Shouping Hu,Jun Wang,Xuehui Cai

Pathogens.2021 Feb 16;10(2):213.doi: 10.3390/pathogens10020213.

Abstract

Streptococcus suis  causes disease in pigs and is implicated increasingly in human disease worldwide. Although most clinical cases are associated with serotype 2, infections by other serotypes have sometimes been reported. Here, we sequenced the genome of a multidrug-resistant  S. suis  serotype 28 (strain 11313) and a multidrug-resistant  S. suis  serotype 31 (strain 11LB5). Strain 11313 was apathogenic in mouse infection models, whereas strain 11LB5 displayed ganglion demyelination, meningeal thickening, congestion, mononuclear cell infiltration, massive proliferation of cortical glial cells, and bacteria (>104 CFU/g) in the spinal cord and ganglia in mice. Furthermore, immunohistochemistry found that the heavily infiltrated glial cells were astrocytes. Strain 11313 harbored the resistance genes  ant(6)-Ia ,  erm(B) ,  optrA ,  tet(l) ,  tet(o) , and strain 11LB5 harbored the resistance genes  ant(6)-Ia ,  erm(B) ,  tet(40) ,  tet(o/w/32/o) ,  aac(6')-aph(2″) . Mouse studies showed that strain 11LB5 exhibited a similar virulence to serotype 2 strain 700794, highlighting the need for surveillance of the other serotype  S. suis  isolates, in addition to serotype 2, in farms. This is the first report of the aminoglycoside resistance gene  ant(6)-Ia  in  S. suis  from animals. This suggests that  S. suis  might serve as an antibiotic resistance reservoir, which spreads the resistance gene  ant(6)-Ia  or  optrA  to other streptococcal pathogens on farms.

Keywords: Streptococcus suis serotype 28; Streptococcus suis serotype 31; antibiotic resistance; characterization; genome.