A Unique Capsule Locus in the Newly Designated Actinobacillus pleuropneumoniae Serovar 16 and Development of a Diagnostic PCR Assay

Abstract

Actinobacillus pleuropneumoniae causes pleuropneumonia, an economically significant lung disease of pigs. Recently, isolates of A. pleuropneumoniae that were serologically distinct from the previously characterized 15 serovars were described, and a proposal was put forward that they comprised a new serovar, serovar 16. Here we used whole-genome sequencing of the proposed serovar 16 reference strain A-85/14 to confirm the presence of a unique capsular polysaccharide biosynthetic locus. For molecular diagnostics, primers were designed from the capsule locus of strain A-85/14, and a PCR was formulated that differentiated serovar 16 isolates from all 15 known serovars and other common respiratory pathogenic/commensal bacteria of pigs. Analysis of the capsule locus of strain A-85/14 combined with the previous serological data show the existence of a sixteenth serovar—designated serovar 16—of A. pleuropneumoniae.

Actinobacillus pleuropneumoniae serotypes in Hungary

“…In conclusion, the IHA test is still one of the most sensitive classical serotyping methods. New molecular biological methods can be very helpful in serotyping A. pleuropneumoniae but they cannot completely replace the classical detection of antigens (Bossé et al, 2017(Bossé et al, , 2018. Serotyping is very important in the identification of A. pleuropneumoniae, since the haemagglutinating antigens of A. pleuropneumoniae are involved in the pathogenicity and in the protection against the disease caused by this agent.…”

Update onActinobacillus pleuropneumoniae-knowledge, gaps and challenges

“…So far, 16 serovars of App are known, which differ in their capsular polysaccharide composition, with serovar 16 identified only recently (Bossé, Li, Sárközi, et al., ; Sárközi et al., ). Depending on their requirement for nicotinamide adenine dinucleotide (NAD) to grow, App strains can be further classified as biovar I (also called “typical”) that are NAD‐dependent, or biovar II (or “atypical”) that are NAD‐independent.…”

“…High levels of hyaluronidase (an enzyme involved in the degradation of the interstitial barrier), that may lead to enhanced infiltration of the pathogen in the lung, were detected in bronchoalveolar lavage fluid (BALF) of pigs experimentally infected with App(Kahlisch, Buettner, Naim, & Gerlach, 2009). 4 | EPID EMIOLOGY OF APP STRAINSSo far, 16 serovars of App are known, which differ in their capsular polysaccharide composition, with serovar 16 identified only recently (Boss e,Li, S ark€ ozi, et al, 2017;S ark€ ozi et al, 2015). Depending on their requirement for nicotinamide adenine dinucleotide (NAD) to grow, App strains can be further classified as biovar I (also called "typical") that are NAD-dependent, or biovar II (or "atypical") that are NAD-independent.…”

Galactose-1-phosphate uridyltransferase (GalT), an in vivo-induced antigen of Actinobacillus pleuropneumoniae serovar 5b strain L20, provided immunoprotection against serovar 1 strain MS71

“…According to previous studies, this model is a far less laborious and resource intensive than the standard porcine model [2,3]. 15 serovars have been reported over the past several decades, and a new serovar 16 was reported in 2017 [4,5]. Traditionally, protection obtained from immunization has been serovar-specific; vaccines have typically lacked cross protective ability between different serovars [6].…”