A case of disseminated mycosis in a German shepherd dog due to Penicillium purpurogenum

Penicillium and Talaromyces spp. emerging pathogens in dogs since 1990s

Penicillium and Talaromyces spp. are environmental saprophytic molds rarely encountered as infectious agents in humans and animals. This article summarizes the clinical features, treatment, and outcomes of proven infections caused by Penicillium or Talaromyces in four dogs in France. Two dogs had disseminated infections, while the other two had a localized form. All dogs had positive histopathological results showing the presence of hyaline septate hyphae and a positive fungal culture with typical Penicillium conidiophores. Talaromyces georgiensis (n = 1), Penicillium labradorum (n = 2), and Penicillium from section Ramosa series Raistrickiorum (n = 1), were identified based on Internal Transcribed Spacer (ITS) Sanger sequencing. The dogs were initially treated with ketoconazole or itraconazole. Second-line treatment was initiated in three dogs, but after several relapses, the prognosis remained poor. Since the 1990s, 18 cases of Penicillium or Talaromyces infections in dogs have been described worldwide. This series of four reports brings new cases to those already reported in the literature, which are probably underestimated in the world.

Disseminated Rasamsonia argillacea infection in a dog

CASE HISTORY

A 4-year-old, male neutered Borzoi presented for unlocalised pain and frequent episodes of vocalisation.

CLINICAL FINDINGS

Pain was localised to the lumbar spine and radiographs revealed a L3-L4 lesion consistent with discospondylitis. The dog was treated for presumptive bacterial discospondylitis with surgical debridement, spinal stabilisation, and cephalexin. Samples collected from the affected intervertebral disc at the time of surgery revealed lymphoplasmacytic inflammation with no causative agent identified on histopathology or bacterial culture. After an initial period of improvement, signs recurred despite an 8-week antibiotic course, with the development of inappetence, weight loss, polydipsia, and polyuria. Repeat radiographs revealed a new cervical intervertebral lesion, and concurrent pyelonephritis was diagnosed based on blood and urine results. Fungal culture of urine resulted in growth of Rasamsonia argillacea species complex and disseminated fungal disease was clinically diagnosed. Antifungal treatment was commenced, however the dog deteriorated, and euthanasia was performed.

PATHOLOGICAL FINDINGS

Multifocal white plaques were grossly visualised in the spleen, mesenteric lymph nodes, cervical vertebrae, and kidneys. Periodic acid-Schiff-positive, fine, parallel-walled, occasionally branching, septate hyphae 5-10 μm in diameter, and conidia 5-7 μm in diameter were found on sectioning all organs. R. argillacea species complex was identified by fungal culture of urine and was considered the species of fungal organism seen histologically. The isolate was subsequently confirmed as R. argillacea by DNA sequencing.

DIAGNOSIS

Disseminated Rasamsonia argillacea infection.

CLINICAL RELEVANCE

Rasamsonia argillacea species complex is a recognised invasive mycosis in veterinary medicine, with disseminated disease causing significant clinical complications and death. This is believed to be the first report of infection caused by R. argillacea in a dog in Australasia and highlights the importance of awareness of a potential fungal aetiology in dogs with discospondylitis.Abbreviations: CLSI: Clinical and Laboratory Standards Institute; CRI: Constant rate infusion; MEC: Minimum effective concentration; MIC: Minimum inhibitory concentration; PAS: Periodic acid-Schiff.

Talaromyces spp. infections in dogs from the Southern United States

Talaromyces spp. are soil-dwelling fungi sporadically reported to cause disease in humans and dogs. This study summarized the clinical presentations, histologic findings, and Talaromyces sp. involved in 5 dogs diagnosed through the panfungal polymerase chain reaction service (PCR) at Texas A&M University, with a review of previously reported cases. Of the 5 cases, 3 were Labrador Retrievers, 2 were male, and 3 were female. Three of 5 involved the musculoskeletal or lymphatic systems, and 2 of 5 dogs presented with meningoencephalitis. Talaromyces helicus, Talaromyces aurantiacus, and Talaromyces boninensis were identified based on panfungal PCR, showing 99% to 100% sequence matches in combination with morphologic features. Three of 5 dogs had static disease at the time of publication, 1 was euthanized, and 1 was lost to follow-up. This study describes Talaromyces spp. as a cause of meningoencephalitis in dogs, identifies 2 novel Talaromyces spp. involved in infections, and adds to the existing knowledge of clinical presentations and outcomes.

Novel Penicillium species causing disseminated disease in a Labrador Retriever dog

This report describes the phenotypic characteristics of a novel Penicillium species, Penicillium labradorum, isolated from a 3-year-old male, castrated, Labrador retriever with disseminated fungal disease. The dog's presenting clinical signs included lethargy, lymphadenopathy, tachypnea, moderate pitting edema, and nonweight bearing lameness associated with the right hind limb. Fine-needle aspirate biopsies from the sublumbar and prescapular lymph nodes were initially examined. The cytologic findings were consistent with pyogranulomatous inflammation with abundant extracellular and phagocytized fungal fragments and hyphae. Based on the morphology of the organisms and lack of endogenous pigment, hyalohyphomycosis was considered most likely, with Fusarium, Penicillium, and Paecilomyces species being considerations. Fungal isolates were obtained via culture of samples from the lymph nodes, and molecular identification testing originally identified an undescribed Penicillium species belonging to the Penicillium section Exilicaulis. BLAST searches and phylogenetic analyses performed approximately 1 year and 9 months after the isolation date revealed an isolate within the Penicillium parvum clade in the Penicillium section Exilicaulis but phylogenetically distant from the other species in the section, thus representing a new species, Penicillium labradorum. Antifungal susceptibility testing was also performed on the isolate and low minimum inhibitory concentrations were observed with terbinafine, voriconazole, and posaconazole, while in vitro resistance was observed with fluconazole. The dog had been previously treated with fluconazole, itraconazole, amphotericin B lipid complex, voriconazole, and terbinafine. Approximately 587 days after the initial diagnosis, the dog was euthanized due to worsening of clinical signs and concerns for quality of life.

Granulomatous polyarthritis caused by Talaromyces georgiensis in a dog

A 6-y-old, 3.5-kg, spayed female Toy Poodle was presented with left forelimb lameness of 2-d duration. Two months before the initial presentation, radiography showed osteolysis of the medial epicondyle of the left humerus, and the left forelimb was amputated. Grossly, the articular villi of the elbow joint were markedly thickened, and the articular cartilage surfaces of the distal humerus and proximal radius had partial erosion. Histologically, granulomatous arthritis and osteomyelitis characterized by the presence of abundant macrophages containing numerous fungi were observed. ITS and β-tubulin sequences amplified from the isolate from the specimen were 100% and 99% identical to type strain UTHSC D16-145^T of Talaromyces georgiensis, respectively. Canine osteoarthritis caused by T. georgiensis has not been reported previously, to our knowledge.

Computed tomographic and ultrasonographic findings of abdominal arterial pseudoaneurysms caused by systemic mycosis in dogs

OBJECTIVES

To describe multidetector CT and ultrasonographic characteristics of abdominal arterial pseudoaneurysms (segmental dilatations of an artery with a ruptured tunica intima) arising secondary to systemic mycosis in dogs.

MATERIALS AND METHODS

Retrospective study on dogs with confirmed histological diagnosis of a fungal pseudoaneurysm and the availability of multidetector CT or ultrasound images.

RESULTS

At the time of admission, the three dogs included in this study demonstrated segmental arterial dilation, irregular arterial wall thickening, and increased echogenicity or attenuation within the local perivascular fat on ultrasound and multidetector CT images. Follow-up examinations revealed progressive increase in arterial wall thickening and saccular dilation with formation of a pseudoaneurysm in affected vessels of two dogs.

CLINICAL SIGNIFICANCE

Multidetector CT and ultrasonography can be useful imaging modalities in the diagnosis and monitoring of abdominal arterial pseudoaneurysms caused by systemic mycosis.

Pneumonia due to Talaromyces marneffei in a Dog from Southern Brazil with Concomitant Canine Distemper Virus Infection

The pathological and molecular findings associated with Talaromyces marneffei-induced pneumonia with concomitant infection by canine distemper virus (CDV) are described in a dog. The principal pathological alteration occurred in the lungs. Histopathology confirmed multifocal granulomatous pneumonia associated with numerous intralesional and intracellular septate fission cells consistent with T. marneffei. A molecular assay designed to amplify a partial fragment of the 18S rRNA gene of T. marneffei provided positive results from two fungal cultures derived from the lung. Sequencing and phylogenetic analyses confirmed the results of polymerase chain reaction (PCR). Furthermore, antigens of the CDV N protein were identified within the bronchial epithelium by immunohistochemistry and a PCR assay amplified the CDV N gene from hepatic and pulmonary fragments. Collectively, the pathological and molecular techniques confirmed a diagnosis of T. marneffei-induced pneumonia with concomitant infection by CDV. These findings represent the first description of pulmonary penicilliosis in the dog and extend the geographical niche of this emerging infectious pathogen. In this case, infection by CDV may have induced immunosuppression, which facilitated the development of pulmonary penicilliosis.

Identification and Antifungal Susceptibility of Penicillium-Like Fungi from Clinical Samples in the United States

Penicillium species are some of the most common fungi observed worldwide and have an important economic impact as well as being occasional agents of human and animal mycoses. A total of 118 isolates thought to belong to the genus Penicillium based on morphological features were obtained from the Fungus Testing Laboratory at the University of Texas Health Science Center in San Antonio (United States). The isolates were studied phenotypically using standard growth conditions. Molecular identification was made using two genetic markers, the internal transcribed spacer (ITS) and a fragment of the β-tubulin gene. In order to assess phylogenetic relationships, maximum likelihood and Bayesian inference assessments were used. Antifungal susceptibility testing was performed according to CLSI document M38-A2 for nine antifungal drugs. The isolates were identified within three genera, i.e., Penicillium, Talaromyces, and Rasamsonia The most frequent species in our study were Penicillium rubens, P. citrinum, and Talaromyces amestolkiae The potent in vitro activity of amphotericin B (AMB) and terbinafine (TRB) and of the echinocandins against Penicillium and Talaromyces species might offer a good therapeutic alternative for the treatment of infections caused by these fungi.

Imaging characteristics of disseminated Geosmithia argillacea causing severe diskospondylitis and meningoencephalomyelitis in a dog

A 4-year-old male castrated Labrador Retriever presented for severe spinal pain. Radiographs and magnetic resonance imaging showed evidence of diskospondylitis and meningoencephalomyelitis. Blood culture revealed a Geosmithia argillacea fungal infection after DNA sequencing, initially misdiagnosed as Penicillium species. Geosmithia argillacea should be considered as a differential for disseminated fungal diskospondylitis.

Disseminated Scytalidium infection in a German shepherd dog

We report a systemic mycosis in a German shepherd dog caused by Scytalidium spp. The patient presented for progressive cervical pain and forelimb hemiparesis. Cervical computed tomography revealed lysis associated with multiple vertebrae and a soft tissue mass adjacent to the spinal cord, as well as prescapular lymphadenopathy. Fine needle aspirates of the lymph nodes yielded hyphae, and a subsequent culture obtained a Scytalidium spp. Itraconazole therapy was initiated, but the subject was euthanized three months later due to progressive neurologic disease and discomfort. This appears to be the first report of disseminated disease by this species in veterinary medicine.

Granulomatous lymphadenitis caused by Talaromyces helicus in a Labrador Retriever

A 3-year-old spayed female Labrador Retriever was presented for right prescapular lymphadenomegaly. Examination of fine-needle aspirates and impression smears of the node revealed many short hyphal structures found within macrophages and extracellularly. Hyphae were approximately 3 μm in diameter, were irregularly septate with nonparallel walls, and had a small clear halo surrounding a partially stained basophilic internal structure. Hyphae were tapered on one end and had oval to pyriform swellings of 7-10 μm on the other, resulting in a bulbous appearance. Fungal elements stained positively with Gomori methenamine silver and Periodic acid-Schiff stains. The dog was euthanized at the owner's request, and necropsy revealed marked peripheral and visceral lymphadenomegaly. Histopathologic examination of lymph nodes confirmed granulomatous lymphadenitis with many fungal hyphae. Fungal culture yielded pure cultures of organisms that failed to produce ascospores or conidia precluding morphologic identification. PCR was performed using pan-fungal primers, ITS-1 and ITS-2, to amplify the intergenic spacer regions of ribosomal RNA; the PCR product was sequenced and a BLAST search of the GenBank databases at NCBI revealed 100% identity of the organism with Talaromyces helicus, the sexual form of Penicillium helicum. Talaromyces helicus has not previously been reported to cause disease in people or animals.

Clinical, morphological, and molecular characterization of Penicillium canis sp. nov., isolated from a dog with osteomyelitis

Infections caused by Penicillium species are rare in dogs, and the prognosis in these cases is poor. An unknown species of Penicillium was isolated from a bone lesion in a young dog with osteomyelitis of the right ilium. Extensive diagnostic evaluation did not reveal evidence of dissemination. Resolution of lameness and clinical stability of disease were achieved with intravenous phospholipid-complexed amphotericin B initially, followed by long-term combination therapy with terbinafine and ketoconazole. A detailed morphological and molecular characterization of the mold was undertaken. Sequence analysis of the internal transcribed spacer revealed the isolate to be closely related to Penicillium menonorum and Penicillium pimiteouiense. Additional sequence analysis of β-tubulin, calmodulin, minichromosome maintenance factor, DNA-dependent RNA polymerase, and pre-rRNA processing protein revealed the isolate to be a novel species; the name Penicillium canis sp. nov. is proposed. Morphologically, smooth, ovoid conidia, a greenish gray colony color, slow growth on all media, and a failure to form ascomata distinguish this species from closely related Penicillium species.

Cytological, microbiological and therapeutic aspects of systemic infection in a dog caused by the fungus Phialosimplex caninus

A seven-year-old immunocompetent dog presenting with lymphadenopathy, mesenteric masses and splenic nodules was diagnosed with Phialosimplex caninus infection. Cytology of a mesenteric mass aspirate demonstrated few intact cells but numerous variably sized fungal cells and rare hyphal fragments. The identity of the cultured fungus was confirmed by DNA sequencing. Itraconazole therapy improved clinical signs, but the fungus was reisolated at follow-up. P. caninus systemic infection should be suspected in dogs presenting with lymphadenopathy and splenomegaly.

Delimitation and characterisation of Talaromyces purpurogenus and related species

Taxa of the Talaromyces purpurogenus complex were studied using a polyphasic approach. ITS barcodes were used to show relationships between species of the T. purpurogenus complex and other Talaromyces species. RPB1, RPB2, β-tubulin and calmodulin sequences were used to delimit phylogenetic species in the complex. These data, combined with phenotypic characters, showed that the complex contains four species: T. purpurogenus, T. ruber comb. nov. and two new species T. amestolkiae sp. nov. and T. stollii sp. nov. The latter three species belong to the same clade and T. purpurogenus is located in a phylogenetic distant clade. The four species all share similar conidiophore morphologies, but can be distinguished by macromorphological characters. Talaromyces ruber has a very distinct colony texture on malt extract agar (MEA), produces bright yellow and red mycelium on yeast extract sucrose agar (YES) and does not produce acid on creatine sucrose agar (CREA). In contrast, T. amestolkiae and T. stollii produce acid on CREA. These two species can be differentiated by the slower growth rate of T. amestolkiae on CYA incubated at 36 °C. Furthermore, T. stollii produces soft synnemata-like structures in the centre of colonies on most media. Extrolite analysis confirms the distinction of four species in the T. purpurogenus complex. The red diffusing pigment in T. purpurogenus is a mixture of the azaphilone extrolites also found in Monascus species, including N-glutarylrubropunctamine and rubropunctatin. Talaromyces purpurogenus produced four different kinds of mycotoxins: rubratoxins, luteoskyrin, spiculisporic acid and rugulovasins and these mycotoxins were not detected in the other three species.

Phialosimplex, a new anamorphic genus associated with infections in dogs and having phylogenetic affinity to the Trichocomaceae

Anamorphic members of the ascomycete family Trichocomaceae including Aspergillus, Penicillium, Paecilomyces, Geosmithia and Sagenomella have been reported from infections in canines. Six clinical isolates (five associated with infections in canines and one from a human source) demonstrated simple phialides producing conidia in long chains and were investigated for their potential relationship to Sagenomella chlamydospora, a known agent of canine disseminated mycosis. Phylogenetic analyses of internal transcribed spacer (ITS) and small subunit (SSU) region sequences revealed that all of the canine-associated isolates were distinct from Sagenomella species. The new anamorphic genus and species Phialosimplex caninus is described to accommodate the clinical isolates. Sagenomella chlamydospora and Sagenomella sclerotialis are transferred to the new genus as Phialosimplex chlamydosporus comb. nov. and Phialosimplex sclerotialis comb. nov.

Disseminated Geosmithia argillacea infection in a German shepherd dog

We report a systemic mycosis in a German Shepherd dog caused by Geosmithia argillacea. Although this etiologic agent microscopically resembles a Penicillium species, and is histopathologically compatible with members of the genus Aspergillus, morphologic features and molecular characterization clearly separate it from these genera. This appears to be the first report of disseminated disease by this species in humans or animals. In vitro antifungal susceptibility testing suggests resistance to amphotericin B and voriconazole and susceptibility to caspofungin, itraconazole, and posaconazole.

Immune response to fungal infections

The immune mechanisms of defence against fungal infections are numerous, and range from protective mechanisms that were present early in evolution (innate immunity) to sophisticated adaptive mechanisms that are induced specifically during infection and disease (adaptive immunity). The first-line innate mechanism is the presence of physical barriers in the form of skin and mucous membranes, which is complemented by cell membranes, cellular receptors and humoral factors. There has been a debate about the relative contribution of humoral and cellular immunity to host defence against fungal infections. For a long time it was considered that cell-mediated immunity (CMI) was important, but humoral immunity had little or no role. However, it is accepted now that CMI is the main mechanism of defence, but that certain types of antibody response are protective. In general, Th1-type CMI is required for clearance of a fungal infection, while Th2 immunity usually results in susceptibility to infection. Aspergillosis, which is a disease caused by the fungus Aspergillus, has been the subject of many studies, including details of the immune response. Attempts to relate aspergillosis to some form of immunosuppression in animals, as is the case with humans, have not been successful to date. The defence against Aspergillus is based on recognition of the pathogen, a rapidly deployed and highly effective innate effector phase, and a delayed but robust adaptive effector phase. Candida albicans, part of the normal microbial flora associated with mucous surfaces, can be present as congenital candidiasis or as acquired defects of cell-mediated immunity. Resistance to this yeast is associated with Th1 CMI, whereas Th2 immunity is associated with susceptibility to systemic infection. Dermatophytes produce skin alterations in humans and other animals, and the essential role of the CMI response is to destroy the fungi and produce an immunoprotective status against re-infection. The resolution of the disease is associated with a delayed hypersensitive response. There are many effective veterinary vaccines against dermatophytoses. Malassezia pachydermatis is an opportunistic yeast that needs predisposing factors to cause disease, often related to an atopic status in the animal. Two species can be differentiated within the genus Cryptococcus with immunologic consequences: C. neoformans infects predominantly immunocompromised hosts, and C. gattii infects non-immunocompromised hosts. Pneumocystis is a fungus that infects only immunosupressed individuals, inducing a host defence mechanism similar to that induced by other fungal pathogens, such as Aspergillus.