C O N F E R E N C E 16 25 January 2017
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Joint Pathology Center Veterinary Pathology Services WEDNESDAY SLIDE CONFERENCE 2016-2017 C o n f e r e n c e 16 25 January 2017 CASE I: AR-14-1021 (JPC 4066394). Gross Morphologic Diagnosis: Broncho- pneumonia, multifocal, subacute, severe, Signalment: Eight-month-old, Dorset ewe, necrotizing. (Ovis aries). Laboratory results: Bacterial culture of the History: This ewe was enrolled in a lung yielded a pure culture of Trueperella research study in which it underwent surgery pyogenes. and MRI the following day, both under general anesthesia. The ewe initially Histopathologic Description: The lung is recovered normally, displaying brief markedly hypercellular, owing to filling of weakness in the hindlimbs immediately after alveoli by degenerate inflammatory cells, surgery. However, over the next two weeks, amorphous and fibrillar eosinophilic it gradually became dull and lethargic, material (edema and fibrin, respectively), dehydrated, inappetent, and weakened basophilic streaming nuclear and despite supportive care. The animal was eosinophilic cytoplasmic debris, and myriad found recumbent, hypothermic, tachycardic, gram-positive bacterial rods. In some and dyspneic 13 days after surgery and died regions, well-defined areas with before it was able to be euthanized. architectural preservation without cellular Gross Pathology: The major gross lesion was in the lungs. The right cranial lung lobe was half normal size, mottled dark red to black, and firm on palpation. The cranial aspect of the right middle lung lobe appeared similarly. Dissection of the bronchial tree did not reveal the presence of foreign material. Additionally, several ulcers, up to 1 x 2 cm, were present in the Lung, ewe. At subgross magnification – there is diffuse severe alveolar edema and hemorrhage, marked trachea. intraseptal edema, and numerous well-demarcated areas of cellular infiltrate and necrosis. (HE, 5X) 1 detail (coagulative necrosis) are present. flora in the mammary gland, upper Bronchi and bronchiole lumina frequently respiratory, urogenital, and gastrointestinal contain abundant bacteria and sloughed tracts.6,10 Although T. pyogenes can act as a bronchial epithelium. Interlobular septa are primary pulmonary pathogen, infection thickened up to 2mm wide by fibrin and usually follows physical or microbial trauma edema, and blood vessels were congested which overcomes the pulmonary defense and contained bacteria. The pleura is mechanisms, allowing for colonization of expanded up to 3x normal with blood. the lungs.1,8 The pneumonia was initially suspected to be due to aspiration shortly Contributor’s Morphologic Diagnoses: after recovery from anesthesia, but foodstuff Bronchopneumonia, diffuse, subacute, was not present in the respiratory tract. The severe, necrotizing, with myriad gram- reason for the infection was likely due to a positive bacteria. combination of stressors, including what was interpreted as intubation-associated Contributor’s Comment: All findings in ulceration of the trachea. this case were consistent with bronchopneumonia caused by Trueperella Trueperella pyogenes produces and utilizes pyogenes (formerly Arcanobacterium a variety of virulence factors to colonize, pyogenes), a gram-positive non-motile, non- damage, and persist within a variety of sporeforming, short, rod-shaped bacterium.6 tissues in the host. The most important Trueperella pyogenes is one of the most factor is pyolysin (PLO), a cytolysin, which common opportunistic pathogens in is able to bind to and create pores in the cell domestic livestock and is often commensal membranes of erythrocytes, Lung, ewe. Multifocally airways and alveoli contain varying combinations and concentrations of necrotic debris, large colonies of bacilli, edema, and hemorrhage. (HE, 88X) 2 polymorphonuclear cells, and macrophages marked alveolar and septal edema and resulting in cell lysis.6 Trueperella pyogenes numerous large colonies of bacilli, Dorset mutants lacking the PLO gene were unable sheep, Ovis aries. to cause an intraperitoneal infection in mice injected with 108 bacteria, whereas Conference Comment: This case replacement of the PLO gene to the T. demonstrates the characteristic gross and pyogenes mutants restored full virulence.5 histologic lesions associated with bacterial Additional virulence factors used by T. bronchopneumonia. Conference participants pyogenes include fimbriae13, extracellular described the suppurative inflammation matrix binding proteins specific for filling bronchi and bronchioles surrounded collagen4, fibrinogen, fibronectin5, and by multifocal to coalescing areas of exoenzymes including DNases11, necrosis, and readily identified numerous proteases12, and neuraminidases7 which large colonies of bacilli within the areas of degrade host nucleic acids, proteins, and inflammation. Participants discussed the sialic acid residues, respectively. differential diagnosis for large colony forming bacteria in tissue section to include: Note: Multiple different tissue sections of Yersinia sp, Actinomyces sp., Actinobacillus lung were used for the slides submission; sp., Corynebacterium sp, Staphylococcus therefore, not all the participants will receive sp., Streptococcus sp., and T. pyogenes. similar serial microslide sections. Trueperella pyogenes is one of the most common opportunistic pathogens present on JPC Diagnosis: Lung: Bronchopneumonia, the mucosal surfaces of domestic necrotizing and fibrinosuppurative, animals.1,2,5,8 The bacterium induces multifocal to coalescing, severe, with suppurative inflammation within a wide Lung, ewe. There is extensive involvement of airways and necrosis is primarily relegated to the adjacent alveoli, suggesting an aerogenous entry for the causative agent. (HE, 96X) 3 variety of organs and is an important cause of abortion, arthritis, endocarditis, mastitis, osteomyelitis, and pneumonia resulting in significant losses in production animals.2,4 Additionally, T. pyogenes is widespread in the wild animal population and has been reported as an important cause of cerebral abscesses in young male white-tailed deer as a consequence of antler development and conspecific aggression between bucks. Mortality can reach up to 35% in affected free-ranging adult male deer.3 As mentioned by the contributor, while T. pyogenes can be a primary pathogen, it is usually associated with physiologic trauma to a mucosal membrane, concurrent primary Lung, ewe. Alveoli are filled with a combination of 1,2,3,8 degenerate epithelium and heterophils with streaming infection, or immune suppression. As nuclear material (consistent with “oat cells”) (black postulated by the contributor in this case, arrow) and large colonies of bacilli predominate in some there well may be an association with alveoli (green arrow.) placement of the endotracheal tube. Other common commensal organisms of the results in lifelong persistent viral infection ruminant upper respiratory tract that can and leads to ovine progressive pneumonia cause opportunistic bronchopneumonia (OPP), encephalitis, arthritis, and mastitis in include Mannheimia haemolyica, sheep. This lentivirus is a member of the Pasteurella multocida, and Bibersteinia family Retroviridae, and is closely related to trehalosi. Causes of primary infectious caprine arthritis-encephalitis virus. First pneumonia in sheep include parainfluenza reported in Iceland, the “maedi” (respiratory virus 3, respiratory syncytial virus, and form) occurs in sheep older than three years, Bordetella parapertussis, which can while the “visna” (neurologic form) occurs predispose sheep to secondary infection by in younger sheep.1,9 The respiratory form is the commensal bacteria mentioned characterized by interstitial pneumonia with above.1,3,8 Mycoplasma ovipneumoniae is prominent perivascular and peribronchial another important primary etiologic agent lymphoid nodules. This slowly progressive involved in chronic enzootic pneumonia; pneumonia is often complicated by also known as chronic non-progressive secondary bacterial infection, especially T. pneumonia, it is a multi-factorial disease pyogenes.1 Peste des petits ruminants complex affecting lambs less than one-year- (PPRV), a morbillivirus, has also been old. Mycoplasma ovipneumoniae usually reported to cause primary respiratory disease causes a mild, subclinical infection that in small ruminants in Africa and parts of results in poor growth unless complicated by Asia. This virus primarily affects the stressors such as over-crowding, inclement cranioventral lung lobes and causes a weather, or poor air quality.1,2,3,8 bronchointerstitial pneumonia.1,8,9 Another primary cause of pneumonia in Contributing Institution: sheep includes the maedi-visna virus, which Wake Forest School of Medicine 4 Department of Pathology/Comparative 7. Jost BH, Songer JG, Billington SJ. Medicine Cloning, expression, and Medical Center Boulevard characterization of a neuraminidase Winston Salem, NC 27157-1040 gene from Arcanobacterium http://www.wakehealth.edu/Comparative- pyogenes. Infect Immun. 2001; Medicine/ 69(7):4430-7. 8. Lopez A, Martinson SA. Respiratory References: system, mediastinum, and pleurae. In: Pathologic Basis of Veterinary 1. Caswell JL, Williams Disease. Zachary JM ed. 6th ed. St. KJ. Respiratory system. In: Maxie Louis: Elsevier; 2017:537-540. MG, ed. Jubb, Kennedy, and 9. MacLachlan NJ, Dubovi EJ, Palmers Pathology of Domestic eds. Fenners Veterinary Animals. 6th ed. Vol. 2. Philadelphia, Virology. 4th ed. London, UK: PA: Elsevier; 2016:557-560. Elsevier; 2011:267-268,308-323.