Comparative analysis of Streptococcus agalactiae serotypes Ia and II isolates from China and Pakistan in a murine model: A focus on pathogenesis and immune response

Bovine mastitis, caused by Streptococcus agalactiae (Group B Streptococcus; GBS), poses significant economic challenges to the global dairy industry. Mouse models serves as valuable tools for assessing GBS-induced infections as an alternative to large animals. This study aimed to investigate the LD5...

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Published in:Microbial pathogenesis 2024-06, Vol.191, p.106675-106675, Article 106675
Main Authors: Leghari, Ambreen, Sabir, Rabia, Laghari, Sheereen, Khand, Faiz Muhammad, Chandio, Muhammad Ali, Magsi, Abdul Samad, Bhutto, Khaliq ur Rehman, Hassan, Mohammad Farooque, Lakho, Shakeel Ahmed, Lin, Huixing, Fan, Hongjie
Format: Article
Language:English
Subjects:
Animals
Bacterial Load
Cattle
China
Cytokines
Cytokines - blood
Cytokines - metabolism
Disease Models, Animal
Female
Lethal Dose 50
Mastitis
Mastitis, Bovine - microbiology
Mice
Mice, Inbred BALB C
Mouse model
Pakistan
Pathogenicity
Serogroup
Streptococcal Infections - immunology
Streptococcal Infections - microbiology
Streptococcus agalactiae
Streptococcus agalactiae - classification
Streptococcus agalactiae - genetics
Streptococcus agalactiae - immunology
Streptococcus agalactiae - pathogenicity
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Summary:Bovine mastitis, caused by Streptococcus agalactiae (Group B Streptococcus; GBS), poses significant economic challenges to the global dairy industry. Mouse models serves as valuable tools for assessing GBS-induced infections as an alternative to large animals. This study aimed to investigate the LD50 dose, organ bacterial load, and quantification of peritoneal leukocyte populations for GBS serotypes Ia and II isolates from China and Pakistan. Additionally, we measured indicators such as lactoferrin, albumin, and myeloperoxidase (MPO) activity. Pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, and IL-2) and anti-inflammatory cytokines (IL-10 and TGF-β) in serum and tissue samples were evaluated using ELISA and qPCR, respectively. BALB/c mice (4 mice per group) received individual intraperitoneal injections of 100 μl containing specific bacterial inoculum concentrations (ranging from 105 to 109 CFU per mouse) of Chinese and Pakistani GBS isolates (serotypes Ia and II). Control groups received 100 μL of sterile PBS. Results revealed that the LD50 bacterial dose causing 50 % mortality in mice was 107 CFU. The highest bacterial load in all experimental groups was quantified in the peritoneum, followed by blood, mammary gland, liver, spleen, lungs, and brain. The most significant bacterial dissemination was observed in mice inoculated with Pakistani serotype Ia at 24 h, with a subsequent notable decline in bacterial counts at day 3. Notably, infection with Pakistani serotype Ia showed a trend of increased total leukocyte counts, significantly higher than Pakistani serotype II, Chinese Serotype Ia, and Chinese serotype II. A substantial influx of neutrophils and lymphocytes was observed in response to all tested serotypes, with Pakistani serotype Ia inducing a significantly higher influx compared to other groups (Pakistani serotype II, Chinese serotype Ia, and Chinese serotype II). Furthermore, TNF-α, IL-1β, IL-2, and IL-6 expressions were significantly increased in mice one day after infection with the Pakistani serotype Ia. Compared to mice infected with the Pakistani serotype II, Chinese Serotype Ia, and Chinese serotype II, those infected with the Pakistani serotype Ia isolate exhibited the highest production of IL-10 and TGF-β, along with significantly increased concentrations of lactoferrin, albumin, and MPO. These findings suggest that the persistence and severity of infection caused by the Pakistani serotype Ia may be linked to its ability to spread to deep
ISSN:0882-4010
1096-1208
DOI:10.1016/j.micpath.2024.106675