Horizontal gene transfer (HGT) is a very important way that harmful bacteria change and evolve.

HGT helps bacteria share DNA with each other. This means they can quickly gain new abilities, like resisting antibiotics and becoming more dangerous.

How HGT Works:

1. Transformation: Bacteria take in free DNA from their surroundings.
2. Transduction: Bacteria receive DNA with the help of viruses that attack them.
3. Conjugation: Bacteria directly share DNA with each other through contact.

How It Affects Harmful Bacteria:

• About 90% of harmful bacteria have parts of DNA, called plasmids, that often carry genes for resistance.
• More than 70% of bacterial infections show they can resist at least one type of antibiotic because of HGT.
• A study found that 80% of E. coli strains, which can cause serious infections outside the gut, had genes gained through HGT.

Facts About Resistance:

• The CDC says there are about 2.8 million antibiotic-resistant infections in the U.S. every year, which lead to around 35,000 deaths.
• In Europe, 25,000 deaths each year are due to infections that don't respond to drugs.

In short, HGT makes bacteria more adaptable, making it harder to control and treat infections. This shows how important it is to study these genetic processes in medical microbiology.