Pathological Features and Genomic Characterization of an Actinobacillus equuli subsp. equuli Bearing Unique Virulence-Associated Genes from an Adult Horse with Pleuropneumonia.

Actinobacillus equuli subsp. equuli is the etiological agent of sleepy foal disease, an acute form of fatal septicemia in newborn foals. A. equuli is commonly found in the mucous membranes of healthy horses' respiratory and alimentary tracts and rarely causes disease in adult horses. In this study, we report a case of a 22-year-old American Paint gelding presenting clinical signs associated with an atypical pattern of pleuropneumonia subjected to necropsy. The gross and histopathological examinations revealed a unilateral fibrinosuppurative and hemorrhagic pleuropneumonia with an infrequent parenchymal distribution and heavy isolation of A. equuli. The whole genome sequence analysis indicated that the isolate shared 95.9% homology with the only other complete genome of A. equuli subsp. equuli available in GenBank. Seven virulence-associated genes specific to the isolate were identified and categorized as iron acquisition proteins, lipopolysaccharides (LPS), and capsule polysaccharides. Moreover, four genes (glf, wbaP, glycosyltransferase family 2 protein, and apxIB) shared higher amino acid similarity with the invasive Actinobacillus spp. than the reference A. equuli subsp. equuli genome. Availability of the whole genome sequence will allow a better characterization of virulence determinants of A. equuli subsp. equuli, which remain largely elusive.

Etiology of acute respiratory disease in fattening pigs in Finland.

BACKGROUND: The objective of our study was to clinically and etiologically investigate acute outbreaks of respiratory disease in Finland. Our study also aimed to evaluate the clinical use of various methods in diagnosing respiratory infections under field conditions and to describe the antimicrobial resistance profile of the main bacterial pathogen(s) found during the study. METHODS: A total of 20 case herds having finishing pigs showing acute respiratory symptoms and eight control herds showing no clinical signs suggesting of respiratory problems were enrolled in the study. Researchers visited each herd twice, examining and bleeding 20 pigs per herd. In addition, nasal swab samples were taken from 20 pigs and three pigs per case herd were necropsied during the first visit. Serology was used to detect Actinobacillus pleuropneumoniae (APP), swine influenza virus (SIV), porcine reproductive and respiratory syndrome virus (PRRSV), porcine respiratory coronavirus (PRCV) and Mycoplasma hyopneumoniae antibodies. Polymerase chain reaction (PCR) was used to investigate the presence of porcine circovirus type 2 (PCV2) in serum and SIV in the nasal and lung samples. Pathology and bacteriology, including antimicrobial resistance determination, were performed on lung samples obtained from the field necropsies. RESULTS: According to the pathology and bacteriology of the lung samples, APP and Ascaris suum were the main causes of respiratory outbreaks in 14 and three herds respectively, while the clinical signs in three other herds had a miscellaneous etiology. SIV, APP and PCV2 caused concurrent infections in certain herds but they were detected serologically or with PCR also in control herds, suggesting possible subclinical infections. APP was isolated from 16 (80%) case herds. Marked resistance was observed against tetracycline for APP, some resistance was detected against trimethoprim/sulfamethoxazole, ampicillin and penicillin, and no resistance against florfenicol, enrofloxacin, tulathromycin or tiamulin was found. Serology, even from paired serum samples, gave inconclusive results for acute APP infection diagnosis. CONCLUSIONS: APP was the most common cause for acute respiratory outbreaks in our study. SIV, A. suum, PCV2 and certain opportunistic bacteria were also detected during the outbreaks; however, viral pathogens appeared less important than bacteria. Necropsies supplemented with microbiology were the most efficient diagnostic methods in characterizing the studied outbreaks.

A retrospective study of equine actinobacillosis cases: 1999-2011.

Several Actinobacillus spp. are common commensal bacteria of the oral cavity, gastrointestinal tract, and reproductive tract of horses and can cause disease in both foals and adults. The current retrospective study was designed to review Actinobacillus spp. isolated from clinical samples or necropsies of 99 horses during 1999-2011. The cases consisted of 43 foals (<6 months of age), 4 young adults (6 months-2 years), 39 adults (>2 years of age), 2 aborted fetuses, and 11 with unspecified ages. Clinical history, signs, bacterial species isolated, and associated lesions were documented. Actinobacillus spp. were isolated 111 times. The most common isolates were Actinobacillus equuli subsp. equuli (38.7%) and hemolytic Actinobacillus spp. (24.3%). Other isolates were Actinobacillus lignieresii (5.4%), Actinobacillus pleuropneumoniae (1.8%), and unclassified Actinobacillus spp. (28.8%). Actinobacillus equuli subsp. equuli was most commonly isolated from clinical and necropsy cases of septicemia and respiratory disease in both foals and adults. Embolic nephritis, the classical septicemic lesion of equine neonatal actinobacillosis, was also present in several adult septicemic actinobacillosis cases. Predisposing factors such as failure of passive transfer of colostral antibodies as well as concurrent pathogenic bacterial or viral infections were present in numerous actinobacillosis cases. There were many cases, however, for which a predisposing factor or concurrent infection was not documented or apparent, suggesting that Actinobacillus spp. can be primary pathogens under the right circumstances and in the right location.

Caracterização patológica e imuno-histoquímica das lesões de actinobacilose em bovinos / Pathological and immunohistochemical characterization of actinobacillosis lesions in cattle

Actinobacilose é uma doença infecciosa, não contagiosa, geralmente crônica, caracterizada por reação inflamatória piogranulomatosa que ocorre em bovinos e, menos comumente, em ovinos, suínos e equinos. Tecidos moles de cabeça, pescoço e linfonodos regionais são afetados. Neste estudo foram compilados e avaliados 18 casos de bovinos dos livros de registro de janeiro de 1997 a maio de 2011 com diagnóstico de actinobacilose. As lesões foram caracterizadas histologicamente, avaliadas por técnicas de histoquímica e imuno-histoquímica. No exame histológico foram evidenciados piogranulomas típicos de actinobacilose contendo clavas eosinofílicas radiadas, circundadas por neutrófilos, macrófagos, linfócitos e abundante tecido conjuntivo fibroso. Todas as lesões apresentaram cocobacilos Gram negativos na coloração de Gram histológico. Abundantes macrófagos tiveram marcação positiva para CD68, especialmente células epitelioides e células gigantes multinucleadas. Foi observada marcação positiva para CD3 (Linfócitos T) em cerca de 1:3 das células do infiltrado inflamatório linfocitário, e marcação positiva para CD79αcy (Linfócitos B) em 2:3 dos linfócitos, indicando que estes correspondem à maioria dos linfócitos nas áreas inflamatórias das lesões de actinobacilose.

Actinobacillosis is a not contagious infectious disease, usually chronic, and characterized by pyogranulomatous inflammatory reaction that occurs in cattle and is less common in sheep, pig, and horse. Soft tissues of head, mouth, and regional lymph nodes are affected. In this retrospective study, lesions suggestive of Actinobacillosis from 18 cases of anatomopathologic bovine samples were retrieved from the archives of Setor de Patologia Veterinária of Universidade Federal do Rio Grande do Sul, from January 1997 to May 2011. The lesions were classified histologically, evaluated by histochemistry, and immunohistochemistry (IHC) in order to standardize inflammatory infiltration. The most frequent histological findings were typical pyogranulomas of actinobacillosis contained radiating eosinophilic clubs surrounded by neutrophils, macrophages, lymphocytes and abundant fibrous connective tissue. Gram-negative coccobacillus bacteria were shown in all lesions by Gram stain. Abundant macrophages were immunopositive for CD68, especially epithelioid cells and multinucleated giant cells. In addition, a positive immunostaining for CD3 (T lymphocyte) was observed in proportion of 1:3 in lymphocyte inflammatory infiltration, while IHC for CD79αcy (B lymphocytes) was obtained in proportion of 2:3. These results indicated that B lymphocytes are the majority of lymphocyte in the inflammatory area.

Atypical actinobacillosis in bulls in Argentina: granulomatous dermatitis and lymphadenitis / Actinobacilose atípica em touros na Argentina: dermatite granulomatosa e linfadenite

Actinobacillosis is a common cause of sporadic infection in cattle. It was mostly characterized as a pyogranulomatous inflammation of the tongue, but also soft tissues as lymph nodes, other digestive tract localization and skin. The aim of this study was to describe an episode of granulomatous dermatitis and lymphadenitis affecting a bull herd in Argentina during 2010. Actinobacillus lignieresii was isolated from samples collected from one of the affected bulls, and characteristic lesions were observed. Lesions other than 'wooden tongue' are usually uncommon; however, actinobacillosis should be included as a differential diagnosis for cutaneous diseases.

A actinobacilose é causa comum de infecções esporádicas em bovinos. Esta afeção tem sido caracterizada como uma infecção piogranulomatosa não somente da língua como também de tecidos moles tais como linfonodos, ou outras localizações no trato digestivo e na pele. O objetivo do presente trabalho é descrever um episódio de dermatite piogranulomatosa e linfadenite que afetou um rebanho de touros na Argentina em 2010. As amostras recolhidas de um dos animais afetados permitiram o isolamento de Actinobacillus lignieresii. Observaram-se as lesões características da doença. Habitualmente não são comuns outras lesões para além das descritas como "língua de pau", no entanto, a actinobacilose deve ser incluída como um possível diagnóstico diferencial de doenças cutâneas.

An atypical case of respiratory actinobacillosis in a cow

A not pregnant 4-year-old Jersey cow was presented with the sudden appearance of respiratory noise, nasal discharge and moderate respiratory difficulty. Upon physical examination a snoring-like noise, extended head and neck position, exaggerated abdominal effort, bilateral nasal discharge and left prescapular lymph node enlargement were noted. Sub-occlusion of the initial portion of the respiratory tract was suspected. Radiographic and endoscopic examinations revealed a pedunculate mass on the dorsal aspect of the rhinopharynx, which was removed with endoscopically assisted electrosurgery. Histologic examination revealed a chronic pyogranulomatous inflammation with eosinophilic club-like bodies surrounding small colonies of rod-shaped bacteria. Results of histochemical staining were consistent with Actinobacillus-like bacteria and a diagnosis of respiratory actinobacillosis was reached. Surgery and antibiotic therapy were resolutive, as demonstated by an endoscopic check at the second month after surgery, even without the association of the traditional iodine cure, which is regarded as the treatment of choice for actinobacillosis.