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.
Highlights
Streptococcus suis, an organism of the upper respiratory tract of pigs, can cause septicemia, meningitis, endocarditis, bronchopneumonia, arthritis and sudden death, and is divided into 29 serotypes based on capsular polysaccharide (CPS) according to recent studies to date [1,2,3,4]
Strains 11313 and 11LB5 are Gram-positive cocci that occur in pairs, and short chains
The biochemical reactivity profiles of these two strains are in conformity to S. suis
Summary
Streptococcus suis, an organism of the upper respiratory tract of pigs, can cause septicemia, meningitis, endocarditis, bronchopneumonia, arthritis and sudden death, and is divided into 29 serotypes (types 1–19, 21, 23–25, 27–31, and 1/2) based on capsular polysaccharide (CPS) according to recent studies to date [1,2,3,4]. S. suis infections are responsible for major economic losses in the swine industry and are important drivers of the spread of antibiotic resistance throughout the world [5]. Accurate S. suis serotyping is important for the epidemiologic control of pig infections, since the prevalent serotypes vary in different parts of the world [6]. S.suis serotypes have been isolated from animals and humans worldwide [8,11,12,13], there are limited studies on the pathogenesis, genetic evolution, and drug resistance of S. suis and other serotypes
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