Antimicrobial susceptibility and molecular characteristics of Mycoplasma bovis isolated from cases of bovine respiratory disease in Australian feedlot cattle.

To date, antimicrobial susceptibility has not been reported for Australian Mycoplasma bovis isolates. This study determined minimal inhibitory concentrations (MICs) for 12 different antimicrobials against Australian M. bovis isolates and used whole genome sequencing to screen those showing high macrolide MICs for point mutations in target genes. Most lung tissue/swab samples from bovine respiratory disease cases (61/76, 80.3%) tested positive for M. bovis. A set of 50 representative isolates (50/61, 82.0%) that showed adequate growth, was used for MIC testing. Uniformly, low MIC values were confirmed for enrofloxacin (≤ 4 µg/mL), florfenicol (≤ 8 µg/mL), gamithromycin (≤ 2 µg/mL), spectinomycin (≤ 4 µg/mL), tetracycline (≤ 8 µg/mL), tiamulin (≤ 4 µg/mL), and tulathromycin (≤ 0.5 µg/mL). A small proportion (10%) of isolates exhibited high MICs (≥ 32 µg/mL) for tildipirosin, tilmicosin, tylosin, and lincomycin, which were above the epidemiological cut-off values for each antimicrobial (≥ 4 µg/mL). These isolates, originating from three Australian states, underwent whole genome sequencing/multilocus sequencing typing and were compared with the reference strain PG45 to investigate mutations that might be linked with the high macrolide/lincosamide MICs. All five belonged to ST52 and two macrolide associated mutations were identified within the 23 S rRNA gene (A2058G in two sequenced isolates and G748A in all sequenced isolates). Four additional 23 S rRNA gene mutations did not appear to be linked to macrolide resistance. Whilst the majority of Australian M. bovis isolates appear susceptible to the tested antimicrobials, emerging macrolide resistance was detected in three Australian states and requires continued monitoring.

Genetic cause for congenital methemoglobinemia in an Australian Pomeranian dog.

Little is known about genetic causes of congenital methemoglobinemia in dogs. Here, we report a CYB5 R3 mutation in a Pomeranian dog with congenital methemoglobinemia. A 6-year-old neutered female Pomeranian dog was investigated for cyanosis noticed during anesthesia for an orthopedic procedure. The history included lifelong mild exercise intolerance and bluish tongue. Methemoglobinemia was diagnosed using co-oximetry. The CYB5 R3 gene was analyzed by comparing the patient's genomic DNA with the reference canine sequence. Mutation functional significance was investigated using snpEff and multispecies protein homology analyses. A homozygous missense single nucleotide CYB5 R3 mutation (ATC ➔ CTC at codon 194) caused a p.Ile194Leu substitution. The pIle194 residue is highly conserved in other mammals, supporting the likely pathogenicity of the substitution. The mutation described here is identical to that associated with familial methemoglobinemia in a family of Japanese Pomeranian dogs. This observation, together with the homozygous mutation found in our case, indicates that the mutant allele may be widespread within the Pomeranian breed internationally.

Effect of vitamin E and selenium nanoparticles on post-thaw variables and oxidative status of rooster semen.

This study was conducted to determine the combined effects of adding vitamin E (VitE) and selenium nanoparticle (Nano-Se) as antioxidant supplements to rooster semen extender for freezing. Semen samples were collected from 12 White Leghorn roosters and pooled. Subsequently, the samples were divided into nine equal groups using modified Beltsville extender. Extenders were supplemented with either two amounts of VitE (5 and 10µg/mL) or two amounts of Nano-Se (1% and 2%) or a combination of both VitE and Nano-Se, and no antioxidants extender (control group). Using 5µg/mL VitE and 1% of Nano-Se improved (P<0.05) total sperm motility (79.28±3.86%), progressive sperm motility (18.03±1.02%), sperm viability (81.46±2.16%) and integrity of the sperm membrane (77.21±2.12%) after the freeze-thawing process compared with control group (54.08±3.86%, 10.96±1.02%, 60.53±2.16%, and 54.47±2.12%; respectively). Also, extenders supplemented with 5µg/mL Vit E or 5µg/mL VitE and 1% Nano-Se had a lesser malondialdehyde (MDA) concentration compared to control extender (1.15±0.32, and 1.29±0.32, respectively). Total abnormal morphology of sperm was decreased (P<0.05) by adding 5 or 10µg/mL VitE alone or in combined with 1% or 2% Nano-Se. Moreover, extenders containing Nano-Se demonstrated greater glutathione peroxidase (GPx) activity compared to other extenders. Catalase (CAT) activity was greater in extender supplemented with 10µg/mL VitE and 2% Nano-Se. Moreover, higher TAC was observed in extenders supplemented with VitE and Nano-Se. It can be concluded that addition of 5µg/mL vitamin E in combined with 1% Nano-Se improved the post-thawing quality and oxidative variables of rooster semen.