Abstract
A set of 207 Streptococcus suis isolates were collected from ten autonomous communities from Spain in 2019 to 2020 from pigs with meningitis, pneumonic lungs, arthritic joints or other swollen viscera, to a lesser extent. Thirteen capsular types were detected being the most prevalent serotype 2 (21.7%), followed by serotypes 1 (21.3%), 9 (19.3%) and 3 (6.3%). Serotypes 2 and 9 were recovered mainly from the central nervous system (CNS), while serotype 1 was isolated mostly from swollen joints and serotype 3 from the lungs. Twenty-five isolates (12.1%) could not be typed. The most prevalent pathotype was epf + mrp + sly + luxS (49 isolates, 23.8%), and it was related mainly to serotypes 1 and 2. Serotypes 1–3 and 9 were significantly associated with anatomical sites of isolation and virulence factors, serotype 9 (CNS) and serotypes 3 and 9 (lungs) being associated with virulence profiles without the epf gene. S. suis isolates showed globally high antimicrobial resistances, but ampicillin followed by spectinomycin and tiamulin resulted in the highest activities, while the greatest resistances were detected for sulphadimethoxine, tetracyclines, neomycin, clindamycin and macrolides. A total of 87.4% isolates were positive to the tetO gene, 62.4% to the ermB gene and 25.2% to the fexA gene, while 14.6% were positive to all three genes simultaneously. A significative association between isolate resistances to tetracyclines and macrolides and the resistance genes tested was established, except for phenicol resistance and the fexA gene. A set of 14 multiresistance patterns were obtained according to the number of antimicrobials to which the isolates were resistant, the resistances to 12 or more agents being the most prevalent ones. A remarkable amount of multiresistance profiles could be seen among the S. suis serotype 9 isolates.
Highlights
Taken into account the serotypes and anatomical site of isolation (Table 1), the clinical strains recovered from the central nervous system (CNS), lungs and joints added up 94.2% of the locations
A collection of 207 S. suis genes recovered from all around Spain were tested for molecular typing, the main virulence genes, susceptibility to the common antimicrobial agents used for disorders in swine husbandry and the presence of six resistance genes in three antimicrobial classes
Samples were taken from the central nervous system (CNS), joints, lungs, liver and/or other viscera but only when they showed lesions suspicious of the infection caused by S. suis
Summary
The porcine respiratory disease complex (PRDC) is one of the most important health concerns affecting swine production, resulting in poor growth rates and high management costs [1]. Streptococcus suis is one of the secondary infectious agents frequently detected in PRDC and the only Gram-positive organism currently recognized within this complex. S. suis is responsible for a variety of infections such as meningitis, septicemia, arthritis, endocarditis or bronchopneumonia [2]. Clinically healthy pigs can carry these organisms in the tonsils and upper respiratory tract, which is a noticeable way for them to spread. Along with the economic losses caused in pig husbandry, the severity of S. suis relies upon its condition of being a zoonotic agent responsible for sporadic human cases of meningitis or septicemia [3]
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