An outbreak characterized by clinical signs of diarrhea and paralysis, occasionally progressing to fatal outcomes, occurred at an ostrich breeding facility. Conventional antibiotic treatments proved ineffective. To investigate the etiology of the disease, brain and liver specimens were collected for diagnostic analysis. An Escherichia coli (E. coli) isolate, designated strain HZDC01, was obtained from cerebral tissues, and whole-genome sequencing was performed for genomic characterization. Genomic analysis revealed that the chromosomal DNA harbors numerous resistance genes, conferring multidrug resistance through complex mechanisms. Furthermore, a p0111-type plasmid carrying the bla_CTX-M-55 gene and an IncX1-type plasmid harboring rmtB, sul1, APH(6)-Id, tet(A), AAC(3)-IIc, aadA2, bla_TEM-1B, and floR genes were identified. These plasmids carry numerous mobile genetic elements that can disseminate via horizontal gene transfer, thereby amplifying the risk of resistance-gene spread within bacterial populations. Additionally, the ibeB and ibeC genes, which encode proteins involved in the invasion of brain microvascular endothelial cells, were identified. These genes may facilitate E. coli penetration of the blood–brain barrier, potentially leading to meningitis and posing a life-threatening risk to the host. This is the first report of the isolation and characterization of extended-spectrum beta-lactamase E. coli from the brain of an ostrich with paralysis. The findings provide valuable genomic insights into the antimicrobial resistance profiles and pathogenic mechanisms of ostrich-derived E. coli isolates.

Colibacillosis caused by avian pathogenic Escherichia coli (APEC) remains an important bacterial disease in poultry production and is increasingly difficult to control because of antimicrobial resistance. In this study, a lytic phage, ND-4, was isolated from poultry-farm sewage using the O2:K1 APEC strain IMT5155 as the host, and its biological characteristics, genome features and preliminary application potential were evaluated. ND-4 formed clear plaques on IMT5155 and showed a tailed morphology, with an elliptical head of 110 ± 5 nm by 82 ± 5 nm and a tail of 97 ± 5 nm by 18 ± 2 nm, giving a total virion length of approximately 204 ± 10 nm. The phage had an optimal multiplicity of infection of 0.01, a latent period of 20 min, a 50 min burst period and a burst size of 231 PFU/cell. ND-4 remained active across pH 4–9 and at temperatures up to 60 °C, and it retained titers above 10⁸ PFU/mL after exposure to chloroform concentrations up to 15%. Whole-genome sequencing revealed a 154,669 bp double-stranded DNA genome with 184 predicted open reading frames and a G + C content of 48.98%. No virulence or antimicrobial resistance genes were detected. ND-4 reduced biofilm biomass in vitro and decreased tissue bacterial loads and alleviated hepatic inflammation and vacuolar degeneration in IMT5155-challenged chicks. These results indicate that ND-4 is a promising candidate for further development as a phage-based control agent against APEC infection, although larger in vivo studies are needed to define its efficacy, dosing window and biosafety profile.

Since 2020, a disease characterized by paralysis and diarrhea has affected ostriches in southern China, resulting in significant economic losses for ostrich farms. Initial analyses of clinical samples from affected birds indicated the presence of a parvovirus as a potential causative agent. This study aimed to identify and characterize the involved pathogenic parvovirus, analyze its genetic features, determine its phylogenetic relationship with known parvovirus strains, and investigate its role in the observed clinical symptoms. We collected 15 clinical samples ((including sciatic nerve, spleen, kidney, and other visceral organs) from 15 affected ostriches and performed gross pathological and histopathological examinations. Whole-genome sequencing of the detected ostrich parvovirus (OsPV) was conducted, followed by phylogenetic, genetic distance, and recombination analyses. Ostrich parvovirus (OsPV) was detected in the collected clinical samples, and viral genomic DNA was identified across multiple tissues, indicating broad tissue distribution. Phylogenetic analysis revealed that OsPV forms a unique branch within the goose parvovirus (GPV) group and is closely related to Chinese GPV strains, particularly the DY16 strain. Notably, the identified virus possessed two 14 bp deletions in its inverted terminal repeats. Furthermore, the virus (designated GX-2020) was identified as carrying recombination signals derived from the SYG61v and B strains of GPV. Recombination among classical GPV strains likely facilitated the emergence of OsPV and may point to possible cross-species transmission or host-range expansion of GPV. This study offers new insights into the evolution, molecular biology, and host adaptation of parvoviruses in China.

This study investigated the effects of composite postbiotic preparation on the growth performance, immune function, and microbiota composition of Nubian black goats. Thirty healthy Nubian black goats with similar body weights were randomly assigned to two groups (n = 15 per group): a control group fed a basal diet and a treatment group fed the basal diet supplemented with 0.5% composite postbiotic preparation (equal-ratio co-fermentation of Bacillus subtilis GX15 and Lentilactobacillus buchneri GX0328-6). The results indicated that while compound postbiotic supplementation did not significantly alter the average daily gain (ADG) and the serum biochemical indices (p > 0.05), it significantly increased the concentrations of immunoglobulins (IgG and IgA) compared to the control group (p < 0.05). Despite comparable α- and β-diversity, CPP supplementation selectively enriched Bacteroides, UCG-005, and Ruminococcaceae while reducing Turicibacter (LEfSe LDA > 2.0; STAMP p < 0.05), suggesting targeted modulation of gut microbiota. In conclusion, dietary supplementation with 0.5% composite postbiotic preparation improves immune function and modulates intestinal microbiota composition without significantly affecting growth performance in black goats while improving intestinal microbial composition and promoting overall gut health.