Molecular epidemiology, characterization of virulence factors and antibiotic resistance profile of Streptococcus agalactiae isolated from dairy farms in China and Pakistan

Streptococcus agalactiae is one of the most common pathogens that cause bovine mastitis worldwide. Identifying pathogen prevalence and virulence factors is critical for developing prevention and control approaches. Herein, 1 161 milk samples from various dairy farms in China(n=558) and Pakistan(n=603) were collected between 2019–2021 and were subjected to S. agalactiae isolation. Prevalence, serotyping, virulence genes, and antibiotic-resistant genes of S. agalactiae were evaluated by PCR assay. All isolates were characterized for haemolysis, biofilm production, cytotoxicity, adhesion, and invasion on bovine mammary epithelial cells. The prevalence of S. agalactiae-induced mastitis in cattle was found to be considerably higher in Pakistan than in China. Jiangsu and Sindh provinces had the highest area-wise prevalence in China and Pakistan, respectively. Serotypes Ia and II were prevalent in both countries, whereas serotype III was found only in Pakistan. Moreover, all isolates tested positive for PI-2b gene but negative for PI-1 and PI-2a genes. All isolates harboured cfb, cylE, hylB, and fbsB virulent genes, whereas many of them lacked bibA, rib and bca. However, the absence of bac and scp genes in Chinese isolates and cspA in Pakistani isolates was noted, while spb1 and lmb were not detected in isolates of both countries. Pakistani isolates, particularly serotype Iapositive, had a considerably higher ability to produce biofilm, haemolysis, cytotoxicity, adhesion, and invasion than Chinese isolates. Most of the isolates were phenotypically resistant to tetracycline, erythromycin, and clindamycin and genotypic resistance was confirmed by the presence of ermA, ermB, tetM and tetO genes. Our study highlights the antimicrobial resistance profile and virulence-related factors contributing to the epidemiological spread of mastitis-causing S. agalactiae in China and Pakistan. The findings may facilitate future studies designed to develop improved treatment and control strategies against this pathogen.

Antiviral activity of five Asian medicinal pant crude extracts against highly pathogenic H5N1 avian influenza virus

Objective: To study the antiviral properties of the five Asian medicinal plants against in vitro infection by the highly pathogenic avian influenza virus(H5N1).Methods: Crude extracts of Andrographis paniculata, Curcuma longa(C. longa),Gynostemma pentaphyllum, Kaempferia parviflora(K. parviflora), and Psidium guajava obtained by both water and ethanol extractions were investigated for their cytotoxicity in the Madin–Darby canine kidney cells. Thereafter, they were investigated in vitro for antiviral activity and cytokine response upon H5N1 virus infection.Results: The results revealed that both water and ethanol extracts of all the five studied plants showed significant antiviral activity against H5N1 virus. Among these plants,C. longa and K. parviflora showed strong anti-H5N1 activity. Thus, they were selected for further studies on their cytokine response upon virus infection. It was found that ethanol and water crude extracts of C. longa and K. parviflora induced significant upregulation of TNF-a and IFN-b m RNA expressions, suggesting their roles in the inhibition of H5N1 virus replication.Conclusions: To the best of the authors' knowledge, this study is among the earliest reports to illustrate the antiviral property of these Asian medicinal plants against the highly pathogenic avian H5N1 influenza virus. The results of this study shed light on alternative therapeutic sources for treatment of H5N1 influenza virus infection in the future.