Prebiotic effects of dietary xylooligosaccharides on fish gut microbiota, growth, and immunological parameters – a review

Abstract Xylooligosaccharides (XOSs) are increasingly being explored as prebiotics in fish diets; however, their effects and modes of action have not been well evaluated. Reports have shown that dietary XOS has the potential to improve the proliferation of beneficial gut microbes, and their metabolites, and enhance disease resistance in several fish species. In contrast, other studies report no substantial changes in immune and growth parameters compared to control groups. Like all prebiotics, the mode of action of XOS is based on their selective stimulation of beneficial gut microbiota, which will outcompete and prevent pathogen proliferation in the gut, and produce metabolites that modulate host immune responses. The reports of improved growth performance of XOS fed fish may be due improved intestinal microbiome, enhanced glycolysis activity and elevated gastrointestinal enzymatic activities. Dietary XOSs have different effects on fish performance depending on the fish species and the structure of XOSs (degree of XOS polymerization and substitution). Nevertheless, further research is essential to determine the optimal dosage, degree of polymerization, and substitution levels required to improve each fish species' gut health and growth performance. This review highlights the prebiotic effects of XOSs, their mechanism of action, and knowledge gaps.</jats:p

Antibiotic Susceptibility of Mastitogenic Bacteria Isolated From Clinical Mastitis Cows in Midlands Province, Zimbabwe

Mastitis is a global challenge for the dairy industry and mastitogenic bacteria play a critical role among other causes. Many mastitogenic bacteria are becoming resistant to single or combination antibiotic therapy, making mastitis cases difficult to cure. Nevertheless, there is insufficient evidence on the occurrence and antibiotic resistance patterns of mastitogenic bacteria in commercial dairy and communal farms in the Midland Province of Zimbabwe that might support a holistic approach to mastitis mitigation. A cross-sectional study aimed to isolate and evaluate the antibiotic susceptibility patterns of mastitogenic bacteria from cattle with clinical mastitis was conducted. A total of 164 milk samples were analyzed, of which 36.6% (60) samples were collected from commercial farmers, and 63.4% (104) came from communal farmers. The samples were cultured on standard media and sensitivity patterns of the identified bacteria were tested against 14 antibiotics using the Kirby-Bauer disc diffusion method. All milk samples from communal farms were positive for mastitogenic bacteria compared to 88% (53) of mastitogenic positive milk samples from commercial farms. The most common microorganisms from all the 157-mastitogenic positive milk samples were Staphylococcus aureus (37.5%) and Escherichia coli (23.3%). The highest resistance was observed against Penicillin, Erythromycin, Ampicillin, and Lincomycin, whereas most isolates were susceptible to Sulphamethoxazole, gentamycin, neomycin, kanamycin, cloxacillin, ertapenem, ceftriaxone, Amp-Ampicillin, amikacin, vancomycin, and tetracycline. Futher research to investigate the significance of resistant mastogenic bacteria in terms of Veterinary costs, production losses and potential public health transmission of antibiotic resistant mastogenic bacteria is recommende

Prevalence and Antibiograms of Salmonella in Commercially Produced Crocodile meat in Zimbabwe

The presence of Salmonella in food products and emergence of antibiotic resistance are the major challenges facing public health policies. A total of 2749 crocodile meat samples obtained from the Central Veterinary Laboratories in Zimbabwe were screened for Salmonella specieswere collected from three Zimbabwean commercial farms between the year 2012 and 2019 for a retrospective observational study to determine the prevalence and magnitude of antibiotics resistant Salmonella species in crocodile meat. The isolation of Salmonella was in accordance with the ISO 6579:2002 and the antibiotic susceptibility testing was carried out based on Clinical and Laboratory Standard Institute’s recommendations by means of the Kirby-Bauer disk diffusion method. SILAB Database was used to determine the prevalence of Salmonella species. Prevalence was stratified by year and farms. Twenty Salmonella isolates were identified using biochemical tests, and 15 were confirmed by polymerase chain reaction (PCR). Antimicrobial susceptibility profiles of the confirmed Salmonella isolates were examined using 14 antibiotics. The overall prevalence of Salmonella species in crocodile meat samples was 0.5%. The prevalence of Salmonella species ranged from 0.04% to 0.44% in the crocodile meat samples and annual prevalence ranged from 0.01% to 1%. The highest prevalence of Salmonella (4.4%) was recorded in the year 2012. Salmonella isolates from one of the three tested farms were resistant to Erythromycin (73.33%), Ampicillin (80%), and Penicillin G (100%). Generally, Salmonella isolates displayed lower resistance to Cefepime, Ceftriaxone, Amikacin, Tetracycline, Ertapenem, Florfenicol, and Erythromycin (0-53.33%) whereas all Salmonella isolates showed susceptibility to Cefepime, Ceftriaxone, Ertapenem, and Florfenicol. Although the study indicates low prevalence of Salmonella species in crocodile meat, there is a need for strict implementation of Hazard Analysis Critical Control Point (HACCP) to reduce contamination rates in meat and its product