Bacteriophage endolysin treatment for systemic infection of Streptococcus iniae in hybrid striped bass.

Streptococcus iniae, a zoonotic Gram-positive pathogen, poses a threat to finfish aquaculture, causing streptococcosis with an annual economic impact exceeding $150 million globally. As aquaculture trends shift towards recirculating systems, the potential for horizontal transmission of S. iniae among fish intensifies. Current vaccine development provides only short-term protection, driving the widespread use of antibiotics like florfenicol. However, this practice raises environmental concerns and potentially contributes to antibiotic resistance. Thus, alternative strategies are urgently needed. Endolysin therapy, derived from bacteriophages, employs hydrolytic endolysin enzymes that target bacterial peptidoglycan cell walls. This study assesses three synthetic endolysins (PlyGBS 90-1, PlyGBS 90-8, and ClyX-2) alongside the antibiotic carbenicillin in treating S. iniae-infected hybrid striped bass (HSB). Results demonstrate that ClyX-2 exhibits remarkable bacteriolytic potency, with lytic activity detected at concentrations as low as ∼15 µg/mL, approximately 8-fold more potent than the PlyGBS derivatives. In therapeutic effectiveness assessments, both carbenicillin and ClyX-2 treatments achieved significantly higher survival rates (85 % and 95 %, respectively) compared to placebo and PlyGBS-based endolysin treatments. Importantly, no statistical differences were observed between ClyX-2 and carbenicillin treatments. This highlights ClyX-2 as a promising alternative for combating S. iniae infections in aquaculture, offering potent bacteriolytic activity and high survival rates.

Infectious laryngotracheitis: Etiology, epidemiology, pathobiology, and advances in diagnosis and control - a comprehensive review.

Infectious laryngotracheitis (ILT) is a highly contagious upper respiratory tract disease of chicken caused by a Gallid herpesvirus 1 (GaHV-1) belonging to the genus Iltovirus, and subfamily Alphaherpesvirinae within Herpesviridae family. The disease is characterized by conjunctivitis, sinusitis, oculo-nasal discharge, respiratory distress, bloody mucus, swollen orbital sinuses, high morbidity, considerable mortality and decreased egg production. It is well established in highly dense poultry producing areas of the world due to characteristic latency and carrier status of the virus. Co-infections with other respiratory pathogens and environmental factors adversely affect the respiratory system and prolong the course of the disease. Latently infected chickens are the primary source of ILT virus (ILTV) outbreaks irrespective of vaccination. Apart from conventional diagnostic methods including isolation and identification of ILTV, serological detection, advanced biotechnological tools such as PCR, quantitative real-time PCR, next generation sequencing, and others are being used in accurate diagnosis and epidemiological studies of ILTV. Vaccination is followed with the use of conventional vaccines including modified live attenuated ILTV vaccines, and advanced recombinant vector vaccines expressing different ILTV glycoproteins, but still these candidates frequently fail to reduce challenge virus shedding. Some herbal components have proved to be beneficial in reducing the severity of the clinical disease. The present review discusses ILT with respect to its current status, virus characteristics, epidemiology, transmission, pathobiology, and advances in diagnosis, vaccination and control strategies to counter this important disease of poultry.

Analysis of codon usage pattern in the viral proteins of chicken anaemia virus and its possible biological relevance.

Chicken anaemia virus (CAV) is an important poultry pathogen. CAV infection can lead to severe immunosuppression and mortality in birds. The viral proteins (VP1, VP2 and VP3) are major protective immunogens that determine the pathotype of CAV strains. The factors influencing the synonymous codon usage bias and the nucleotide composition of the viral protein genes of CAV have not been studied. In the present study, we have analysed the synonymous codon usage pattern in VP1, VP2 and VP3 genes of CAV. Our results showed that all the genes have a low codon usage bias; however, this bias was slightly higher in the VP2 gene as compared to VP1 and VP3. The major contributing factor for this pattern of codon usage bias in CAV is mutational pressure followed by the host factors. The conclusion was drawn based on codon usage, correspondence analysis, ENC-GC3 plot and correlation analyses among different indices. The study will help us to understand the codon usage bias of CAV and related single-stranded DNA viruses which could further be used to explore their biology.