Anti-cancer microbe

Could a strain of genetically modified bacteria become the next cancer therapy? Researchers at Stanford Medicine recently discovered that Staphylococcus epidermidis, a bacterium that lives on the surface of healthy human skin, can help kill cancer tumors in mice.

The scientists genetically engineered the bacteria to express an antigen (a protein that triggers an immune response) to skin cancer tumors. They then used a swab to gently rub the “designer” bacteria onto the fur of mice. A control group of mice received swab treatments of unmodified S. epidermidis. Researchers injected both treated and control mice with skin cancer cells and watched for tumor growth over the subsequent weeks. Tumor growth in mice that received the engineered bacteria was significantly slowed in comparison with tumor growth in control mice. The treatment also worked in mice that already had skin cancer tumors. The study was published April 13 in Science.

S. epidermidis produces cytotoxic T cells, capable of killing ­cancer cells. Lead author Michael Fischbach was surprised the mild treatment was so effective. Insertion of the tumor antigen tricked the mouse’s immune system into producing these cells. Ultimately, the T cells migrated to matching tumors and proliferated.

Fischbach’s team plans to test engineered bacteria in human ­cancer patients. But S. epidermidis may have a different response in humans, so they’ll first need to determine the right microbe to use. Another challenge will be to find a human cancer protein that triggers the desired immune response.

A troubling U.S. health trend

Sexually transmitted infections (STIs) in the U.S. rose significantly in 2021, according to the Centers for Disease Control and Prevention. An April 11 annual surveillance report measured an overall 7 percent increase in syphilis, gonorrhea, and chlamydia between 2017 and 2021. The 176,713 syphilis cases in 2021 signaled the highest number in over 70 years and a 32 percent increase from 2020. The number of babies born with congenital syphilis also increased by 32 percent, resulting in 220 stillbirths and infant deaths.

Gay and bisexual men and some ethnic minorities continue to be disproportionately affected by STIs. The CDC attributed the increase in STIs to interruptions in healthcare during the COVID-19 pandemic, but also said lockdowns could have affected sexual behaviors. Experts say decreased condom use and increased substance abuse could also be factors. —H.F.