Streptococcus suis: a kórokozó mikrobiológiája és laboratóriumi diagnosztikája : Irodalmi áttekintés – I. rész

Abstract

Streptococcus suis is a facultative pathogenic and zoonotic bacterium, that occurs worldwide. It can be found in all age groups in industrial pig farming, as well as in small backyard stocks, and has also been detected in wild boar samples. S. suis is primarily found in the mucous membranes of the upper respiratory tract, the nasopharyngeal cavity, the gastrointestinal and the genital tract, as well as in the tonsils of swine. The transmission of the pathogen mostly occurs through oral-faecal route, or as a result of physical contact between pigs, as well as through fomites. S. suis can cause clinical symptoms due to various stressors and other predisposing factors such as low maternal antibody levels in piglets at the time of weaning. The severity of the clinical disease is influenced by several environmental factors (poor ventilation, high humidity, high dust-ammonia, stress) or improper management (overcrowding, mixing pigs of different ages and lack of all in-all out system), and the presence of other viral or bacterial co-infections. Virulence factors like CPS (capsule polysaccharide), SLY (suilysin), MRP (murami- dase-released protein) and FHBP (H-factor binding protein) may play key role in the pathogenicity of S. suis strains. There are 29 true S. suis serotypes, but from a clinical perspective, most laboratories still identify 35 serotypes. A large proportion of the strains isolated from pigs showing clinical symptoms belong to serotypes 1-9. The most common serotypes, isolated from disease are type 2, type 9, type 3, type 1/2, and type 7. In routine laboratory diagnostics, the detection of serotypes 1-31, 33, and 1/2 is possible due to new molecular methods. A global analysis of the distribution of S. suis serotypes would be urgent and gap filling, while fresh serotype-prevalence data should be exceptionally important for effective control.