Could bacteriophage be an alternative to antibiotics for Group B Strep (GBS) in pregnant women?
GBS is a commensal bacteria, found harmlessly in the gut of some people. But it is an opportunistic pathogen that can cause significant disease - sepsis, meningitis, lung injury and bacteremia - in newborns exposed to it in the vaginal tract during birth, for example.
Lucy Furfaro is an Emerging Leadership Fellow at the University of Western Australia in Perth. I spoke to her about her research in this area, how she became interested in the microbiology of newborns and their mothers, and the advantages of living in the most remote city on Earth.
Lucy works at the King Edward Memorial Hospital, the referral center for all of Western Australia which covers an area approximately equal to the US west of the Rocky Mountains.
What makes the hospital unique is that it hosts The Raine Study, the world's oldest prospective birth cohort, which has been collecting ongoing health data on mothers and their babies for 35 years.
Preventing infection of newborns is done differently depending on where you are. The standard in Australia and the US is universal screening, typically a swab test. Expectant mothers testing positive for GBS in the vaginal tract (about 1 in 4) are given antibiotics pre-emptively.
The UK and New Zealand take a risk-based approach (e.g., a history of infection) to determine who gets the antibiotic. While antibiotic resistance is not an issue of concern in GBS yet, we know that eventually it can be. Also of interest is what antibiotics do to the microbiome of moms and their babies.
These concerns lead to the consideration of phage as a possible targeted therapy for GBS. At least a few challenges, both scientific and regulatory, remain to be solved.
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Bacteriophage or simply phage are viruses that infect and kill bacteria. They are typically specific to a single type or closely related bacteria. Some are obligately lytic phages that infect a bacterium, replicate inside, lyse the cell and move on to the next bacterium. Others can hedge their bet, taking either the lytic pathway or occasionally integrating their DNA into the DNA of the host bacteria. These temperate phage might later be induced to lyse their host cells and move on.
Ideally, phages chosen for antimicrobial therapies are of the lytic variety. But every phage found to infect Group B Strep so far is a temperate phage. That is either a sampling problem or an interesting biological question of why that is so.
Beyond the biology are the regulatory questions. Are phage biologicals? They aren’t alive. However, neither is an engineered antibody, which is subject to a lot of analysis to confirm its identity.
One possible solution is to avoid using intact phage particles. It involves the engineering of phage lysins, the enzymes that disrupt bacterial cell walls and membranes. These might be delivered in a topical cream to prevent infection at birth avoiding broad spectrum antibiotic resistance and causing minimal disruption to the maternal microbiome.
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