Publications by authors named "Heba Atalla"

Bovine milk contains bioactive components that are nutritionally and immunologically important to calves and humans. Dairy cows classified as high (H) immune responders using the patented high immune response technology have higher concentrations of immunoglobulin and specific antibodies in sera and milk compared with average (A) and low (L) responders. MicroRNA post-transcriptionally regulate expression of milk bioactive components and are enriched in extracellular vesicles known as exosomes, which protect them from degradation.

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Infectious diseases are the outcome of complex interactions between the host, pathogen, and environment. After exposure to a pathogen, the host immune system uses various mechanisms to remove the pathogen. However, environmental factors and characteristics of pathogens can compromise the host immune responses and subsequently alter the outcome of infection.

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Mastitis is one of the most prevalent and costly diseases in the dairy industry with losses attributable to reduced milk production, discarded milk, early culling, veterinary services, and labor costs. Typically, mastitis is an inflammation of the mammary gland most often, but not limited to, bacterial infection, and is characterized by the movement of leukocytes and serum proteins from the blood to the site of infection. It contributes to compromised milk quality and the potential spread of antimicrobial resistance if antibiotic treatment is not astutely applied.

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Background: Staphylococcus aureus is one of the most prevalent pathogens to cause mastitis in dairy cattle. Intramammary infection of dairy cows with S. aureus is often subclinical, due to the pathogen's ability to evade the innate defense mechanisms, but this can lead to chronic infection.

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Persistent or difficult-to-treat Staphylococcus aureus infections in animals and humans may be related to small colony variants (SCVs) that can hide inside host cells and modulate host defenses. S. aureus SCVs have gained much attention in human medicine but have been underestimated and overlooked in veterinary medicine.

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Persistence of bovine Staphylococcus aureus mastitis may be associated with the small colony variant (SCV) form that is adapted to intracellular life and resists elimination by the immune system. This study evaluated antibody-mediated (AMIR) and cell-mediated immune responses (CMIR) to two bovine SCV forms and their parent strains isolated from cows with mastitis. Four groups of healthy cows, five cows/treatment group, were challenged by the intramammary route with naturally occurring bovine SCV Heba3231, its parent strain 3231, a hemB mutant displaying the SCV phenotype or its parent strain, Newbould 305.

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Persistent bovine Staphylococcus aureus mastitis is attributable to the versatility of this pathogen within the mammary gland environment and to the formation of small colony variants (SCVs) that can survive within host cells. Previous studies had shown that S. aureus SCV Heba3231, isolated from a cow with chronic mastitis, had invaded and persisted in primary bovine aortic endothelial cells but caused minimal deleterious effects.

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A recently isolated bovine Staphylococcus aureus small colony variant (SCV) was shown to persist within cultured endothelial cells. However, the clinical importance of S. aureus SCV in persistent infection of the mammary gland is unknown.

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Article Synopsis
  • Staphylococcus aureus is a significant pathogen causing chronic bovine mastitis and various diseases in humans, with this study examining the role of small colony variants (SCVs) in such infections.
  • Isolates from chronically infected cows showed differences in morphology and hemolytic activity, with some typical forms transitioning to SCVs under gentamicin exposure, indicating a potential for adaptation in response to antibiotics.
  • The study highlights the unique properties of SCV Heba3231, including slow growth and reduced virulence compared to typical S. aureus strains, suggesting SCVs could contribute to the persistence of infections like mastitis.
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