Proposal of serovars 17 and 18 of Actinobacillus pleuropneumoniae based on serological and genotypic analysis

The aim of this study was to investigate isolates of Actinobacillus pleuropneumoniae previously designated serologically either as NT or as ‘K2:07’, which did not produce serovar-specific amplicons in PCR assays. We used whole genome sequencing to identify the capsule (CPS) loci of six previously designated biovar 1 non-typable (NT) and two biovar 1 ‘K2:O7’ isolates of A. pleuropneumoniae from Denmark, as well as a recent biovar 2 NT isolate from Canada. All of the NT isolates have the same six-gene type I CPS locus, sharing common cpsABC genes with serovars 2, 3, 6, 7, 8, 9, 11 and 13. The two ‘K2:O7’ isolates contain a unique three-gene type II CPS locus, having a cpsA gene similar to that of serovars 1, 4, 12, 14 and 15. The previously NT isolates share the same O-antigen genes, found between erpA and rpsU, as serovars 3, 6, 8, and 15. Whereas the ‘K2:O7’ isolates, have the same O-antigen genes as serovar 7, which likely contributed to their previous mis-identification. All of the NT and ‘K2:O7’ isolates have only the genes required for production of ApxII (apxIICA structural genes, and apxIBD export genes). Rabbit polyclonal antisera raised against representative isolates with these new CPS loci demonstrated distinct reactivity compared to the 16 known serovars. The serological and genomic results indicate that the isolates constitute new serovars 17 (previously NT) and 18 (previously ‘K2:O7’). Primers designed for amplification of specific serovar 17 and 18 sequences for molecular diagnostics will facilitate epidemiological tracking of these two new serovars of A. pleuropneumoniae

Comparative sequence analysis of the capsular polysaccharide loci of Actinobacillus pleuropneumoniae serovars 1-18, and development of two multiplex PCRs for comprehensive capsule typing

Problems with serological cross-reactivity have led to development of a number of PCRs (individual and multiplex) for molecular typing of Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia. Most of these assays were developed for detection of specific amplicons within capsule biosynthetic genes before the availability of complete sequences for the different serovars. Here we describe comparative analysis of the complete capsular loci for all 18 serovars of A. pleuropneumoniae, and development of two multiplex PCRs for comprehensive capsule typing of this important pig pathogen

Acute Actinobacillus pleuropneumoniae infection in one-month-old piglets Case report

SUMMARY Background: Actinobacillus pleuropneumoniae is an important pathogen of swine, it can cause respiratory disease in piglets sometimes from 6 weeks of age, but typically 12-16 week-old feeder pigs are susceptible. It has two biotypes and 16 serotypes, and due to the different pattern of toxin production there are great differences in the virulence of the strains. Objectives: Besides reaching etiologic diagnosis, the objective of the examina tion was to prove that in case of special circumstances sometimes young pig lets around weaning age can show the clinical signs and post mortem lesions caused by Actinobacillus pleuropneumoniae. Materials and methods: Lungs of six 28 and 31-day-old piglets showing lesions of acute haemorrhagic-necrotic pneumonia and fibrinous pleuritis were sent from a large scale farm with 3000 sows in the Eastern part of Hungary. According to our previous examinations A. pleuropneumoniae was present in the herd; serotype 16 strains were isolated earlier but the pigs in the farm were not vaccinated against A. pleuropneumoniae. The lung samples were inoculated on blood agar plates; they were cross-inoculated with Staphylococcus aureus and incubated at 37 ºC for 24 hours in the presence of 5% carbon dioxide. The isolated A. pleuropneumoniae strains were serotyped using the indirect haemagglutination test. Results and Discussion: Actinobacillus pleuropneumoniae biotype 1 serotype 11 strains were isolated from the lungs; this serotype was not detected in this farm earlier. The examinations confirmed that A. pleuropneumoniae can cause disease not only in grower and feeder pigs, but a newly introduced serotype can also result severe clinical signs and lesions of the disease around weaning in the absence of maternal protection. The age of the diseased animals can be informative in setting up the diagnosis of an infectious disease; however the circumstances have to be always carefully evaluated

Isolation of Biotype 1 Serotype 12 and Detection of <i>Actinobacillus pleuropneumoniae</i> from Wild Boars

Actinobacillus pleuropneumoniae is a major pathogen of swine, which can cause severe pleuropneumonia in pigs, but sometimes the disease can be generalized. Diseases caused by A. pleuropneumoniae are frequent all over the world, resulting in high losses among domestic pigs. However, our knowledge on the occurrence of A. pleuropneumoniae in wild boars and feral pigs is limited. We aimed to examine the carriage of A. pleuropneumoniae by hunted wild boars. The presence of A. pleuropneumoniae was examined in tonsils of 68 hunted wild boars collected at a game processing unit. An in-house designed species-specific PCR test was used to detect the gene of Apx IV toxin, and the samples were inoculated on a modified selective agar. A. pleuropneumoniae was detected in 10 animals (14.7%) by PCR and one A. pleuropneumoniae serotype 12 strain was isolated. The antibiotic resistance pattern of the strain resembled field strains that were isolated from farmed pigs in Hungary. This is the first case for the detection of A. pleuropneumoniae not only using PCR or ELISA, but also its isolation, identification, and serotyping