Researchers study science behind drug resistant bacteria

E. coli

E. coli

Klebsiella pneumoniae strains of bacteria, or those better known as being resistant to antibiotics, are the focus on a new study where scientists are using genome sequencing capabilities to find out how exactly antibiotic resistant strains of bacteria come to be.

The scientists have already identified several mechanisms that bacteria use to share genes and expand their antibiotic resistance. In fact, they found that in some cases, bacteria can receive a new set of genes all at once and in the process become pathogenic.

As explained in a recent article, the scientists involved in the story are focusing on the large mobile DNAs, such as plasmids, which exist as free DNA circles apart from the bacterial chromosome, and genomic islands, which can splice themselves into the chromosome. These mobile DNAs are major mechanisms for evolution in organisms that lack a true nucleus. Genomic islands and plasmids carry genes that contribute to everything from metabolism to pathogenicity, and move whole clusters of genes all at once between species.

“Identifying how genomic islands move and their effect on bacterial physiology could lead to new approaches to bypass bacterial defenses,” researcher Corey Hudson of Sandia National Laboratories in California, said in the article.

Eventually, the hope is that their effort might lead to a way to predict new pathogens before they emerge as public health threats.

“We’re just starting on this path,” researcher Kelly Williams said in the article. “It’s a harder problem to predict emerging pathogens, rather than just observe them. Determining what is pathogenic in the first place and how it might become more pathogenic is a research challenge.”

For some background, Williams said that it’s important to understand that bacteria share genetic material through free virus particles or through a cell-to-cell process called conjugation, where one bacterium sends out a tube from its surface into another’s and injects genes into the other cell.

For example, consider you have a local water supply that is contaminated with a pathogenic E. coli strain that is not antibiotic-resistant. Klebsiella pneumoniae enters the water, comes into contact with the E. coli, and donates genes. Now a pathogenic E. coli has acquired resistance, making it harder to eradicate.

The article goes on to explain that over the two decades that various bacterial genomes have been sequenced, researchers have found rampant gene sharing and have used the same knowledge to look into infectious diseases which according to the Centers for Disease Control and Prevention (CDC), about one in 25 hospital patients experience, with them turning lethal in about one of every nine cases.

The team’s research will continue with the help of a database they created of genomic islands they found in a survey of all sequenced bacteria. So far, the database contains nearly 4,000 genomic islands—only a partial list of what bacteria share. The database reveals both global features of genomic islands and unique features in select groups of bacteria.

To go along with this, his team also invented a new experimental approach to detect islands as they pop out of the genome. The team stimulates this beginning stage of island mobilization by stressing the cells in certain ways. During this stage, the mobilized islands take circular form, independent of the chromosome. The islands are now free to move into other bacterial cells, bringing with them new sets of genes.

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