Novel Antibiotic Treatment for Bovine Mastitis

Inventor:

Richard Novick, Ph.D, Hope F. Ross, Ph.D, Geeta Ram, Ph.D

Background: 

Staphylococcal bovine mastitis is extremely difficult to treat and most certainly fatal mammary gland infection in dairy cattle in United States incurring considerable losses to the dairy industry. Staphylococcus aureus, long considered a dangerous, antibiotic resistant pathogen, has become even more virulent, contagious and resistant, especially to b-lactams (MRSA) and glycopeptides (VRSA). Today, it causes a wide variety of life-threatening infections, many of which cannot be treated effectively with conventional antibiotics, due to a paucity of new antibiotics being developed. This is because pathogens such as staphylococci rapidly acquire resistance to new antibiotics, leading to a global crisis of drug resistance and rise of almost untreatable infections. 

Recently, researchers at the NYU School of Medicine, have developed a novel non-antibiotic method for treating staphylococcal infections. This method is based on the naturally-occurring, highlymobile staphylococcal pathogenicity islands (SaPIs). SaPIs are ~15 kb genetic elements that are stably inserted in the staph chromosome but can be induced to excise and replicate. The replicated SaPI DNA is packaged in infectious phage-like particles which are released from the bacterial cell upon phage-induced lysis, resulting in high frequency SaPI transfer. The SaPIs carry and consequently disseminate genes encoding toxins and other virulence factors.

Summary:

Drs. Richard Novick, Hope F. Ross and Geeta Ram have designed a unique strategy to exploit and harness SaPI spread by converting these agents of disease into agents of therapy – antibacterial drones (ABDs). To create the ABDs, the group re-engineered the SaPIs, deleting their natural cargo (toxin genes), increasing their packaging capacity from 15 to >40 kb, and inserting any of variety of antibacterial modules. They also modified the helper phage so that ABD particles are produced in the absence of functional phage. The ABD particles are administered to infected animals, where they reach the site of infection and thus, abrogate the infection. The researchers incorporated into ABDs either CRISPR/cas9 or CRISPR/dcas9 modules with spacers targeting a chromosomal gene or the promoter region of a global virulence regulator, respectively. Subsequent studies involving the CRISPR/cas9-containing ABD demonstrated that ABDs kill S. aureus in vitro by DNA cleavage, block the development of a subcutaneous S. aureus abscess, and rescue mice given a lethal dose of S. aureus intraperitoneally. Studies also demonstrated that the CRISPR/dcas9 containing ABD blocks the expression of staphylococcal virulence in vitro and blocks the formation of a subcutaneous abscess in vivo. As proof of principle, the inventors have now shown that the technology can eliminate a whole range of S. aureus that are known to cause Bovine mastitis and that the technology is milk insensitive.

As the ABD system is based upon discrete individual particles, rather than soluble small molecules such as antibiotics, the ABD system is, in principle, akin to the therapeutic use of bacteriophages.

However, the ABD system has many advantages over phage therapy, including wide versatility in antibacterial activity, great capacity for the attachment of novel DNA cargo, wide host range, and the ability to prevent the development of resistance. The ABD system is a rapid, efficient, easy to use technology and can readily be scaled up for therapeutic purposes.

Advantages: 

  • It is not a phage
  • ABDs may contain more than one module targeting the same process
  • Can work independent of CRISPR
  • ABDs can target any bacterial function
  • Broader host range
  • Can penetrate biofilms and other sites of bacterial sequestration

Intellectual Property:

Patent Pending