Serotype distribution of Actinobacillus pleuropneumoniae isolated from diseased pigs in Argentina (2020-2024).

Streptococcus suis is an economically important pathogen of pigs as well as a zoonotic cause of human disease. Serotyping is used for further characterization of isolates; some serotypes seem to be more virulent and more widely spread than others. This study characterizes a collection of German field isolates of Streptococcus suis from pigs dating from 1996 to 2016 with respect to capsular genes (cps) specific for individual serotypes and pathotype by multiplex PCR and relates results to the clinical background of these isolates. The most prominent finding was the reduction in prevalence of serotype-2/serotype-1/2 among invasive isolates during this sampling period, which might be attributed to widely implemented autogenous vaccination programs in swine against serotype 2 in Germany. In diseased pigs (systemically ill; respiratory disease) isolates of serotype-1/serotype-14, serotype-2/serotype-1/2, serotype 3 to 5 and 7 to 9 were most frequent while in carrier isolates a greater variety of cps types was found. Serotype-1/serotype-14 seemed to be preferentially located in joints, serotype 4 and serotype 3 in the central nervous system, respectively. The virulence associated extracellular protein factor was almost exclusively associated with invasive serotype-1/serotype-14 and serotype-2/serotype-1/2 isolates. In contrast, lung isolates of serotype-2/serotype-1/2 mainly harbored the gene for muramidase-released protein. Serotype 4 and serotype 9 isolates from clinically diseased pigs most frequently carried the muramidase-released protein gene and the suilysin gene. When examined by transmission electron microscopy all but one of the isolates which were non-typable by molecular and serological methods showed various amounts of capsular material indicating potentially new serotypes among these isolates. Given the variety of cps types/serotypes detected in pigs, not only veterinarians but also medical doctors should consider other serotypes than just serotype 2 when investigating potential human cases of Streptococcus suis infection.

Streptococcus suis is an important zoonotic agent causing severe diseases in pigs and humans. To date, 33 serotypes of S . suis have been identified based on antigenic differences in the capsular polysaccharide. The capsular polysaccharide synthesis (cps) locus encodes proteins/enzymes that are responsible for capsular production and variation in the capsule structures are the basis of S . suis serotyping. Multiplex and/or simplex PCR assays have been developed for 15 serotypes based on serotype-specific genes in the cps gene cluster. In this study, we developed a set of multiplex PCR (mPCR) assays to identify the 33 currently known S . suis serotypes. To identify serotype-specific genes for mPCR, the entire genomes of reference strains for the 33 serotypes were sequenced using whole genome high-throughput sequencing, and the cps gene clusters from these strains were identified and compared. We developed a set of 4 mPCR assays based on the polysaccharide polymerase gene wzy, one of the serotype-specific genes. The assays can identify all serotypes except for two pairs of serotypes: 1 and 14, and 2 and 1/2, which have no serotype-specific genes between them. The first assay identifies 12 serotypes (serotypes 1 to 10, 1/2, and 14) that are the most frequently isolated from diseased pigs and patients; the second identifies 10 serotypes (serotypes 11 to 21 except 14); the third identifies the remaining 11 serotypes (serotypes 22 to 31, and 33); and the fourth identifies a new cps cluster of S . suis discovered in this study in 16 isolates that agglutinated with antisera for serotypes 29 and 21. The multiplex PCR assays developed in this study provide a rapid and specific method for molecular serotyping of S . suis .

Background: Actinobacillus pleuropneumoniae (A. pleuropneumoniae) is one of the most important bacterial respiratory pathogens. It is the only etiological agent of porcine pleuropneumonia (PPP) or it appears as a secondary bacterial infection in the swine respiratory disease complex (PRDC). In Serbia, apart from the identification of serotype 2, no tests have been performed to establish the presence of other A. pleuropneumoniae serotypes in the pig population. The aim of this study was to perform genotyping of A. pleuropneumoniae isolates originating from pig farms in Serbia by apx genes and using multiplex polymerase chain reaction (mPCR).Materials, Methods & Results: Isolates of A. pleuropneumoniae examined in this study were obtained from lungs with macroscopically visible alterations characteristic of a A. pleuropneumoniae. A total of 46 isolates were examined. They were extracted from the lung tissue samples of pig carcasses from 9 farms across different parts of Serbia. Genotyping of isolates was performed in the previously described manner. Briefly, 5 pairs of oligonucleotide primers were used for amplification of 4 different apx genes which encode synthesis of exotoxins (ApxI , ApxII , ApxIII i ApxIV) characteristic for all A. pleuropneumoniae serotypes and biovars. Amplification of appropriate genome parts was performed with a reaction chain polymerase (PCR) in multiplex (m) format using appropriate diagnostic kits to extract DNA from bacteria and perform mPCR reaction. The results of genotyping of 46 isolates of A. pleuropneumoniae indicate the existence of a large number of different serotypes of A. pleuropneumoniae on the studied farms or that different serotypes of this microorganism circulate in the pig population in Serbia. In addition to the detection of dominant serotype 2, which was established on 7 farms, of which in 4 farms it was the only detected serotype, in the examined pig population the presence of serotypes 3, 5, 6, 7 and 9 was also found. Furthermore, the presence of 2 different serotypes of A. Pleuropneumoniae was also detected on 3 farms; on the first farm serotypes 2 and 3, on the second farm serotypes 2 and 6, and on the third farm serotypes 2 and 7.Discussion: Although the research was done with a relatively small number of isolates of A. pleuropneumoniae, comparing the obtained results with the results on the presence and prevalence of appropriate serotypes from other countries, we concluded that there is significant diversity of this pathogen in the pig population in farms of Serbia. Detection of different serotypes of A. pleuropneumoniae in the pig population and the presence of several different serotypes on 1 farm was established for the very first time in Serbia. All isolates from our study can be characterized as highly virulent, considering that the clinical symptoms, pathological findings and the results of bacteriological examination indicated A. pleuropneumoniae to be the cause of animal death. Like in the neighbouring countries, the strongly pathogenic serotype 9 and the less pathogenic serotype 2 are the most frequently identified causative agents of porcine pleuropneumonia in the AutonomousProvince of Vojvodina, Republic of Serbia. The necessity to establish the presence of all A. pleuropneumoniae serotypes in the pig population, and in particular to determine the presence of different serotypes on individual farms, is crucial for several reasons: making a definitive diagnosis; development of prophylactic strategies for medicines; implementation of immunoprophylactic vaccination. Keywords: swine, porcine pleuropneumonia, PPP, serovar 2, serotype, lung, PCR.

Antimicrobial usage in pig industry in Taiwan for prevention and treatment of bacterial diseases has been applied for decades. The pressure of antimicrobial selection contributes to the emergence of antimicrobial-resistant porcine bacterial pathogens. Three common bacterial pathogens, Actinobacillus pleuropneumoniae, Escherichia coli, and Salmonella enterica serovar Choleraesuis, were investigated for antimicrobial susceptibility and mechanisms of antimicrobial resistance in this study. The quinolone resistance-determining regions (QRDRs) of the gyrA gene of nalidixic acid-resistant S. enterica serovar Choleraesuis isolated from swine were sequenced. Four types of point mutation were found in this regions: Ser-83-to-Phe (TCC→TTC), Ser-83-to-Tyr (TCC→TAC), Asp-87-to-Gly (GAC→GGC), and Asp-87-to-Asn (GAC→AAC). PCR-RFLP and MAS-touch down PCR were developed for detected of point mutations in QRDRs of the gyrA gene. Fifty swine isolates of S. enterica serovar Choleraesuis collected from 1997 to 2002 were examined by PCR-RFLP and MAS-touch down PCR. The result indicated 7 isolates with point mutations in codon 83, 13 with point mutations in codon 87, and 30 with double mutations in both codons 83 and 87. The minimum inhibition concentrations (MICs) of enrofloxacin of the isolates with a single mutation in codon 83 or 87 were 128 mg/ml. A class I integron comprised of dhfr, orfF and aad2 was also identified in both human and swine S. enterica serovar Choleraesuis isolates. In addition, the susceptibility of 16 common antimicrobials among 60 isolates of each of A. pleuropneumoniae, E. coli, and S. enterica serovar Choleraesuis isolated from diseased pigs from 1997 to 2001 were tested. The MIC values indicated that ceftiofur and amikacin were highly active against isolates of A. pleuropneumoniae, E. coli, and S. enterica serovar Choleraesuis; cephalothin, doxycycline, florfenicol, and gentamicin were highly to A. pleuropneumoniae but moderately active to E. coli, and S. enterica serovar Choleraesuis; trimethoprim was only highly active against A. pleuropneumoniae; flumequine was only moderately active against S. enterica serovar Choleraesuis; ampicillin, chloramphenicol, kanamycin, and tetracycline were moderately active against A. pleuropneumoniae only. The other antimicrobials tested were inactive. E. coli and S. enterica serovar Choleraesuis isolates were analyzed for antimicrobial resistance genes, integrase gene and virulence factor by multiplex PCR. The prevalence of integrase gene in E. coli and S. enterica serovar Choleraesuis were 97% and 95%, respectively. The prevalence of extended- spectrum β-lactamase (tem) and florfenicol resistance (floR) in E. coli were 38% and 55%, respectively. The prevalence of tem, floR and spvC (Salmonella plasmid virulence C gene) in S. enterica serovar Choleraesuis were 60%, 25%, and 98%, respectively. This study indicated the emergence of multidrug resistance in A. pleuropneumoniae, E. coli and S. enterica serovar Choleraesuis is a serious problem in swine industry. A surveillance system is necessary on the swine industry to monitor the emergence of fluoroquinolone and/or multidrug resistant bacterial pathogens in Taiwan.

BackgroundHaemophilus parasuis is the etiological agent of Glässer’s disease, and causes severe economic losses in the swine industry. Serovar classification is intended as an indicator of virulence and pathotype and is also crucial for vaccination programs and vaccine development. According to a polysaccharide biosynthesis locus analysis, H. parasuis isolates could be classified by a molecular serotyping assay except serovars 5 and 12 detected by the same primer pair. The aim of this study was to identify H. parasuis isolates from diseased pigs in Taiwan by using a molecular serotyping assay and to analyze the relationship between serovars and pathological patterns.MethodsFrom August 2013 to February 2017, a total of 133 isolates from 277 lesions on 155 diseased animals from 124 infected herds serotyped by multiplex PCR and analyzed with pathological data.ResultsThe dominant serovars of H. parasuis in Taiwan were serovars 5/12 (37.6%), 4 (27.8%) and 13 (15%) followed by molecular serotyping non-typable (MSNT) isolates (13.5%). Nevertheless, the serovar-specific amplicons were not precisely the same sizes as previously indicated in the original publication, and MSNT isolates appeared with unexpected amplicons or lacked serovar-specific amplicons. Most H. parasuis isolates were isolated from nursery pigs infected with porcine reproductive and respiratory syndrome virus. The percentage of lung lesions (30.4%) showing H. parasuis infection was significantly higher than that of serosal lesions.DiscussionCollectively, the distribution of serovars in Taiwan is similar to that found in other countries, but MSNT isolates remain due to genetic variations. Furthermore, pulmonary lesions may be optimum sites for H. parasuis isolation, the diagnosis of Glässer’s disease, and may also serve as points of origin for systemic H. parasuis infections in hosts.

Porcine pleuropneumonia (PPP) is one of the main causes leading to massive losses in the pig industry, with high economic impacts. Among different etiological agents, Actinobacillus pleuropneumoniae (APP) is responsible for severe fibrinous-necrotizing pleuropneumonia. A total of 19 different APP serotypes are currently recognized. This study aimed to identify APP serotypes isolated from pneumonic lesions in naturally infected and dead pigs in the Piedmont Region and to describe lesions. A total of 107 dead pigs with a suspected PPP diagnosis were included in this study. Lungs were evaluated using gross-pathology scoring systems, histopathology, and APP isolation and serotypes identification by multiplex PCR were conducted. Gross lung lesions were mainly represented by fibrinous pneumonia and pleuropneumonia. APP was isolated in 20/107 (18.7%) samples. PCR indicated APP DNA presence in 53/107 (49.5%) of lung samples. The most observed serotypes were serotype 2 in 24/53 (45.3%) and serotype 6 in 13/53 (24.5%) samples. Moreover, multiplex PCR results suggested a coinfection of different serotypes in five samples. This study emphasizes the importance of an integrated approach, utilizing various techniques, such as gross- and histopathology, and bacteriological culture and PCR, to enhance the diagnosis of APP infections.

Background: Southeast Asian (--SEA) deletion of α-thalassemia is the most common α-thalassemia-1 mutation in Thailand and neighborhood countries. The absence of α-globin gene production in a homozygous fetus is the most serious and leads to death in utero or soon after birth and life-threatening maternal complications. Therefore, sensitive and accurate assays for detecting α-thalassemia--SEA deletion are crucial for thalassemia diagnosis. Materials and Methods: The present study evaluated multiplex polymerase chain reaction (PCR)--SEA, comparing with the routinely performed gap-PCR for α-thalassemia diagnosis in prenatal thalassemia prevention and control strategy commonly used in Thailand. Four primers were employed to detect the deleted region of α-globin gene family. This, thus, provides high accuracy in discriminating heterozygous and homozygous --SEA deletion. Results: Multiplex PCR--SEA assay showed the results with 100% sensitivity, specificity, positive predictive value, negative predictive value, and efficiency in comparison to the routinely performed gap-PCR used in prenatal thalassemia prevention and control strategy. In addition, the multiplex PCR--SEA assay displayed lower detection limit for heterozygous detection. Conclusion: The novel multiplex PCR--SEA in the present study was proofed to be a good alternative for thalassemia diagnosis in thalassemia prevention and control strategy. The advantage of the assay is the capability to identify three wild types and one deleted fragment comparing with one wild type and one deleted fragment in the routinely performed gap-PCR. This is very useful, especially in the genes where polymorphism is common. Therefore, the multiplex PCR--SEA provides a better protocol for α-thalassemia--SEA diagnosis. Keywords: α-thalassemia, Hemoglobin Bart’s hydrop fetalis, Multiplex PCR, Polymerase chain reaction, Prenatal diagnosis, --SEA deletion

ABSTRACTBackground: Actinobacillus pleuropneumoniae (APP) causes porcine pleuropneumonia (PP).Objective: Serotypes and antimicrobial resistance patterns in APP isolates from pigs in Korea were examined.Methods: Sixty-five APP isolates were genetically serotyped using standard and multiplex PCR (polymerase chain reaction). Antimicrobial susceptibilities were tested using the standardized disk-agar method. PCR was used to detect β-lactam, gentamicin and tetracycline-resistance genes. The random amplified polymorphic DNA (RAPD) patterns were determined by PCR.Results: Korean pigs predominantly carried APP serotypes 1 and 5. Among 65 isolates, one isolate was sensitive to all 12 antimicrobials tested in this study. Sixty-two isolates was resistant to tetracycline and 53 isolates carried one or five genes including tet(B), tet(A), tet(H), tet(M)/tet(O), tet(C), tet(G) and/or tet(L)-1 markers. Among 64 strains, 9% and 26.6% were resistance to 10 and three or more antimicrobials, respectively. Thirteen different antimicrobial resistance patterns were observed and RAPD analysis revealed a separation of the isolates into two clusters: cluster II (6 strains resistant to 10 antimicrobials) and cluster I (the other 59 strains).Conclusion: Results show that APP serotypes 1 and 5 are the most common in Korea, and multi-drug resistant strains are prevalent. RAPD analysis demonstrated that six isolates resistant to 10 antimicrobials belonged to the same cluster.

Multiplex PCR assays for the detection and identification of various Streptococcus suis strains in tonsillar specimens from pigs were developed and evaluated. In two separate reactions, five distinct DNA targets were amplified. Three targets, based on the S. suis capsular polysaccharide (cps) genes specific for serotypes 1 (and 14), 7, and 9, were amplified in multiplex PCR I. Two other targets, based on the serotype 2- (and 1/2-) specific cps gene and the epf gene, encoding the EF proteins of virulent serotype 2 and highly virulent serotype 1 strains, were amplified in multiplex PCR II. To identify false-negative results, firefly luciferase (luc) DNA and primers based on the luc gene were included in the assay. The multiplex PCR assays were evaluated with tonsillar specimens from pigs infected with S. suis strains. The results obtained with the PCR assays were compared with the results obtained with a bacteriological examination. Most (94%) of the results obtained with multiplex PCR assays were confirmed by the bacteriological examination. The PCR method seems to be more sensitive compared to the bacteriological method, since the remaining 6% of the samples were positive by PCR and negative by bacteriological examination. These results indicate that the PCR method is highly specific for the detection of S. suis strains most frequently involved in clinical disease in infected pig herds. The serotypes found by PCR in tonsillar specimens from diseased pigs were compared with the serotypes of the strains isolated from the affected tissues of the same pigs. The results showed that there is significant association between carriership and clinical illness for S. suis serotype 9 and EF-positive serotype 2 strains and not for serotype 7 and EF-negative serotype 2 (or 1/2) strains.

Streptococcus suis is an opportunistic pathogen or pathobionts in pigs and a zoonotic pathogen for humans. S. suis Serotype 2 (SS2) is the predominant serotype isolated from diseased pigs but rarely isolated from healthy pigs. This study aims to investigate whether the growth of SS2 can be inhibited by commensal S. suis non-serotype 2 (non-SS2) sharing tonsillar habitats. Agar co-culture (CI<1.0) and transwell assays confirmed that two non-SS2 strains inhibited the growth of patients, diseased and asymptomatic pig SS2 isolates by contact-dependent mechanism. Kinetic co-culture demonstrated that the consequence of this competition was the coexistence of SS2 at the low density. Moreover, non-SS2 also interfered SS2 adhesion on IPEC-J2 cells. Comparative whole genome analysis elucidated that contact-dependent growth inhibition involved with T7SS homologs and apparently non-lethal interaction. Complete semi-phosphorylative Entner-Doudoroff, CMP-Neu5Ac, and Catechol meta-cleavage pathways distinctively found in non-SS2 and their increased expression during co-culture might facilitate them to outcompete the growth of SS2. In conclusion, this study identified a novel contact-dependent growth competition phenotype in non-SS2 that might contribute to maintaining a low density of the SS2 target in natural habitats.

Actinobacillus pleuropneumoniae causes porcine pleuropneumoniae which is one of severe threats to the swine industry. In total, 54 strains of Actinobacillus pleuropneumoniae were isolated from 443 pigs between 2012 and 2013 in Korea. Isolates were classified into serotypes 1, 2, 5, 7, 12, and unclassified by multiplex PCR. Genotypes of isolates were divided into three groups according to the sequence of the omlA gene. The antimicrobial resistance rate of serotype 1 was slightly higher than that of serotype 5. In conclusion, to block and treat porcine pleuropneumonia, it is necessary to conduct ongoing characterization of A. pleuropneumoniae isolated from pigs.

Tropical theileriosis, bovine babesiosis and anaplasmosis are tick-borne protozoan diseases that impose serious constraints on the health and productivity of domestic cattle in tropical and sub-tropical regions of the world. A common feature of these diseases is that, following recovery from primary infection, animals become persistent carriers of the pathogen and continue to play a critical role in disease epidemiology, acting as reservoirs of infection. This study describes development and evaluation of multiplex and single PCR assays for simultaneous detection of Theileria annulata, Babesia bovis and Anaplasma marginale in cattle. Following in silico screening for candidate target genes representing each of the pathogens, an optimised multiplex PCR assay was established using three primer sets, cytob1, MAR1bB2 and bovar2A, for amplification of genomic DNA of T. annulata, A. marginale and B. bovis respectively. The designed primer sets were found to be species-specific, generating amplicons of 312, 265 and 166 base pairs, respectively and were deemed suitable for the development of a multiplex assay. The sensitivity of each primer pair was evaluated using serial dilutions of parasite DNA, while specificity was confirmed by testing for amplification from DNA of different stocks of each pathogen and other Theileria, Babesia and Anaplasma species. Additionally, DNA preparations derived from field samples were used to evaluate the utility of the single and multiplex PCRs for determination of infection status. The multiplex PCR was found to detect each pathogen species with the same level of sensitivity, irrespective of whether its DNA was amplified in isolation or together with DNA representing the other pathogens. Moreover, single and multiplex PCRs were able to detect each species with equal sensitivity in serially diluted DNA representing mixtures of T. annulata, B. bovis and A. marginale, and no evidence of non-specific amplification from non-target species was observed. Validation that the multiplex PCR efficiently detects single and mixed infections from field samples was demonstrated. The developed assay represents a simple and efficient diagnostic for co-detection of tropical theileriosis, bovine babesiosis and anaplasmosis, and may be a valuable tool for epidemiological studies aimed at assessing the burden of multiple infection with tick-borne pathogens and improving control of the associated diseases in endemic regions.

A total of 218 isolates of Staphylococcus hyicus from pigs in eight countries (Belgium, Croatia, Germany, Japan, Korea, Slovenia, the UK and the USA) and 44 isolates from other animals...

Development of an improved species specific PCR test for detection of Haemophilus parasuis

The aim of this review is to provide practical guidance for the molecular diagnosis of parasitic diseases in Korea in 2024. Specifically, the prevalence of parasitic diseases, commercially available molecular diagnostic kits, and reference laboratories for molecular diagnosis are presented. It is based on the literature and the medical diagnosis device database of the Korea Disease Control and Prevention Agency. In Korea, molecular diagnostic kits are available for intestinal protozoa (Giardia lamblia, Entamoeba histolytica, Cryptosporidium hominis, and Cryptosporidium parvum), Trichomonas vaginalis, and malarial parasites. Molecular diagnosis of other parasites is also possible; however, there is no commercially available kit. Therefore, parasite samples or derivatives for molecular diagnosis should be sent to specific laboratories, the parasitology departments of medical schools, or the Division of Vectors and Parasitic Diseases, Bureau of Infectious Disease Diagnosis Control at the Korea Disease Control and Prevention Agency. In commercial diagnostic kits, multiplex real-time polymerase chain reaction (PCR) is used to rapidly and easily detect the amplified parasitic DNA. The loop-mediated isothermal amplification (LAMP) was developed to diagnose T. vaginalis and Acanthamoeba infections. Its merits are that it does not require a PCR machine and has a short test time of approximately 60 min. Although LAMP is not commercially available, it may be widely used to screen for parasitic diseases. Commercial molecular diagnostic kits for parasitic diseases are limited to the clinical setting in Korea. Available kits are used to diagnose certain intestinal protozoa, T. vaginalis, and to differentiate Plasmodium species using multiplex PCR.