Atypical Multibacterial Granulomatous Myositis in a Horse: First Report in Italy

Abstract

Infectious causes of myositis are reported relatively uncommonly in horses. Among them, bacterial causes include Streptococcus equi subsp. zooepidemicus, Actinobacillus equuli, Fusobacterium spp. Staphylococcus spp, and Corynebacterium pseudotuberculosis. Infection can be spread to muscles via haematogenous or extension from skin lesions. Parasitic myositis has also been documented. In this report, a 12 year-old Italian Quarter Horse mare presented with diffuse subcutaneous nodules and masses ranging from 2 × 3 to 5 × 20 cm in size, and adherent to subcutis and muscles that were first macroscopically and cytologically diagnosed as pyogranulomas. Subsequently, histological, molecular, bacteriological, and biochemical investigations were performed. All the data obtained allowed to diagnose a severe and diffuse multibacterial granulomatous myositis caused by Corynebacterium pseudotuberculosis and Corynebacterium amycolatum. Following the therapy and an initial disappearance of most of the lesions together with a general improvement of the mare, the clinical condition deteriorated, and new nodules appeared. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and PCR techniques revealed the presence of bacteria as Glutamicibacter creatinolyticus and Dietzia spp. To the authors’ knowledge, this case report represents the first description of multibacterial granulomatous myositis due to Corynebacterium pseudotuberculosis, Corynebacterium amycolatum, Glutamicibacter creatinolyticus, and Dietzia spp. in a horse reared in Italy.

Molecular characterization of Corynebacterium pseudotuberculosis, C. silvaticum, and C. auriscanis by ERIC-PCR

“…The absence of genotype patterns associated with hosts and biovars may have been related to the low representative sampling for these categories, since 4 of the 78 strains of C. pseudotuberculosis belonged to biovar Equi, and most isolates were from goats. Recently it has been observed that the C. pseudotuberculosis biovar Equi can also infect small ruminants (DoMENIS et al, 2018) and the biovar ovis has previously been isolated from horses (RIFICI et al, 2020), showing that there is no host specificity regarding the different C. pseudotuberculosis biovars.…”

Perfil de sensibilidade a antibióticos de um isolado de Providencia rettgeri proveniente de equino

“…As colônias obtidas no ágar chocolate tiveram identificação realizada em equipamento Biotyper (Bruker Daltonics, Billerica, MA), baseado em MALDI TOF MS. Após cultivo em ágar BHI (infusão de cérebro e coração) por 24 horas a 37°C, uma colônia isolada foi aplicada em um poço da placa de aço alvo MALDI Biotyper. Adicionou--se ao poço 1 μl de ácido fórmico (70%) e 1 μl de matriz MALDI-TOF MS (composta por uma solução saturada de ácido α-ciano-4-hidroxicinâmico), deixando-se secar em temperatura ambiente (ASSIS et al, 2017;RIFICI et al, 2020).…”

“…Antes que as medições da amostra fossem registradas, o espectrômetro foi calibrado usando-se um padrão de teste bacteriano (E. coli DH5 alfa). Pontuações de corte recomendadas pelo fabricante foram usadas para identificação, com pontuações ≥2.000, indicando identificação em nível de espécie, enquanto pontuações ≥1,700 e <2.000 indicam identificação em nível de gênero e pontuações <1.700 não indicam uma identificação confiável (ASSIS et al, 2017;RIFICI et al, 2020).…”