Biosensor zeroes in on dangerous bacteria

Staphylococcus or Staph aureus is a type of infectious bacteria that commonly causes skin and respiratory infections in addition to food poisoning. In some cases, it can lead to life-threatening diseases such as pneumonia, and brain, bone or heart infections. As well, it’s a common hospital acquired infection.

Now, a team of scientists from Saudi Arabia and Jordan have developed a point-of-care diagnostic test as effective in food samples as it is in clinical samples to detect the bacteria. It’s cheap, instrument-free, and takes less than a minute, according to lead researcher Mohammed Zourob, professor of chemistry at Alfaisal University in Saudi Arabia.

The researcher and his colleagues tested the biosensor in food and clinical isolates from a hospital but instead of targeting bacterial cells, as traditional sensors would, they targeted poteases enzymes released by the cells or expressed on the cells’ surface. The former’s sensitivity is too poor to detect infectious dozes of most bacteria, according to Zourob, unlike the latter method, invented by Zourob et al.

The probe itself is made up of a specific peptide sequence, cleaved by Staph aureus proteases, and sandwiched between magnetic nanobeads and gold surface on top of a paper support.

Another perk to the test, according to its developer, is that it does not require special training to use, so it can be easily administered by food inspectors and hospital nurses.

Zourob and his colleagues say they are now establishing a spin off in order to commercialize this new technology.

Bacterial methylomes and antibiotic potentiation

Cohen et al., Nature Genetics, 2016

Cohen et al., Nature Genetics, 2016

Antibiotics emerged as miracle drugs and “silver bullets” in the early 20th century, revolutionizing medicine and our ability to combat infectious disease while positively impacting health and lifespans on a large scale. This remarkable triumph held steady for many years, and consequently antibiotic research and development diminished as a priority due to the seeming defeat of bacterial infections. However, the selective pressure that came with antibiotic exposure led to the development of bacterial resistance to these compounds, motivating renewed interest in what is now an extremely important public health issue. Mechanisms of resistance are many and ever-evolving, and we know now that it is not a matter of IF bacteria will become resistant to a class of antibiotics, but when. The search for new and potentially exploitable bacterial vulnerabilities, then, becomes a constant enterprise in order for us to keep pace with the bacteria in the antibiotics/resistance arms race.

Cohen et al., Nature Genetics, 2016

Cohen et al., Nature Genetics, 2016

A new study this week in Nature Genetics describes how manipulating the bacterial DNA methylome affects susceptibility to multiple classes of antibiotics. The authors observed that deleting the dam gene, encoding a DNA methyltransferase, from E. coli causes increased susceptibility to sub-lethal doses of the β-lactam antibiotic ampicillin. Dam specifically methylates GATC sites, and deletion of any of the other three DNA methyltransferases found in E. coli had no effect on the level of antibiotic susceptibility. Using SMRT sequencing, the authors saw that genome-wide GATC methylation patterns did not change after exposure to ampicillin, so they sought alternative explanations for the observed phenotype. Continue reading