Microscopic landscape of bacteria exchanging DNA, symbolizing antibiotic resistance spread.

Superbugs Evolving: How Genomic Islands Spread Antibiotic Resistance

Lena Kashyap in Health & Wellness June 2025 • 4 min read.

"A deep dive into how Salmonella Genomic Islands (SGI1s) are evolving in Proteus mirabilis and what it means for the future of antibiotic resistance."

In an era where infectious diseases are becoming increasingly difficult to treat, the rise of antibiotic-resistant bacteria, often dubbed 'superbugs,' is a growing concern. Scientists are racing against time to understand how these bacteria evolve and spread their resistance. One key mechanism involves genomic islands—mobile pieces of DNA that can transfer between bacteria, carrying genes that confer resistance to antibiotics and heavy metals.

Among these genomic islands, Salmonella genomic island 1 (SGI1) has been identified as a significant player in the spread of antibiotic resistance. Initially found in Salmonella, SGI1 contains a cluster of genes that enable bacteria to resist multiple drugs. Its ability to jump between different bacterial species has raised alarms about the potential for widespread resistance.

Recent research has focused on Proteus mirabilis, a bacterium known to cause opportunistic infections, particularly in urinary tracts. Scientists have discovered new variants of SGI1 within this bacterium, indicating that P. mirabilis may be a key hub for the evolution and dissemination of antibiotic resistance. Understanding these variants is crucial for developing strategies to combat the spread of superbugs.

What Makes These Genomic Islands So Dangerous?

Microscopic landscape of bacteria exchanging DNA, symbolizing antibiotic resistance spread.

A study published in Frontiers in Microbiology shed light on five SGI1 variants found in P. mirabilis strains, highlighting how these genetic structures contribute to multidrug and heavy metal resistance. The research team, led by Luyao Bie, Meng Fang, and colleagues, identified new versions of SGI1 that are evolving in unique ways, enhancing the bacteria's ability to survive in environments with antibiotics.

The team analyzed five SGI1 variants in detail:

SGI1-PmCAU and SGI1-PmABB: These variants matched previously reported SGI1 structures, indicating a consistent pattern of resistance genes.
SGI1-PmJN16: This new variant is derived from SGI1-Z and contains a novel gene cassette array (dfrA12-orfF-aadA2-qacE△1-sul1-chrA-orf1) that adds to its resistance capabilities.
SGI1-PmJN40: Featuring an unprecedented structure, this variant contains two right direct repeat sequences separated by a DNA fragment rich in transcriptional regulators. This structure allows it to form two different extrachromosomal mobilizable DNA circles for dissemination.
SGI1-PmJN48: Lacking a common ORF S044, this variant has a unique genetic organization at its right junction due to the reverse integration of a P. mirabilis chromosomal gene cluster and the insertion of part of a P. mirabilis plasmid, making it the largest known SGI1 to date (189.1 kb).

These structural changes enable the bacteria to resist a broader range of antibiotics and heavy metals, making infections harder to treat. The SGI1 variants can also excise themselves from the chromosome and transfer to other bacteria, further spreading resistance.

Why This Matters to You

Understanding how bacteria evolve resistance is crucial for developing new strategies to combat infections. By identifying and characterizing these SGI1 variants, researchers can develop targeted interventions to prevent the spread of antibiotic resistance. This includes improving hygiene practices, developing new antibiotics, and implementing stricter regulations on antibiotic use. Staying informed and supporting these efforts is key to protecting public health and ensuring that antibiotics remain effective for future generations.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.3389/fmicb.2018.03172, Alternate LINK

Title: Identification And Characterization Of New Resistance-Conferring Sgi1S (Salmonella Genomic Island 1) In Proteus Mirabilis

Subject: Microbiology (medical)

Journal: Frontiers in Microbiology

Publisher: Frontiers Media SA

Authors: Luyao Bie, Meng Fang, Zhiqiang Li, Mingyu Wang, Hai Xu

Published: 2018-12-19

Everything You Need To Know

What are genomic islands, and why are they important in the context of antibiotic resistance?

Genomic islands are mobile genetic elements, meaning they are pieces of DNA that can move between bacteria. These elements contain genes that confer resistance to antibiotics and heavy metals, allowing bacteria to survive in environments where these substances are present. The significance of genomic islands lies in their ability to rapidly spread antibiotic resistance genes, potentially turning common infections into untreatable ones. The implications of this are severe, as it undermines the effectiveness of antibiotics, leading to prolonged illnesses, increased healthcare costs, and higher mortality rates.

What is Salmonella Genomic Island 1 (SGI1), and why is it significant?

Salmonella Genomic Island 1 (SGI1) is a specific type of genomic island initially identified in Salmonella bacteria. It contains a cluster of genes that provide resistance to multiple drugs. SGI1's importance stems from its capacity to transfer resistance genes across different bacterial species. This poses a significant threat because it enables the rapid dissemination of antibiotic resistance, making it difficult to control the spread of resistant bacteria. The consequences include the potential for widespread treatment failures in infections.

Why is the discovery of SGI1 variants in Proteus mirabilis important?

Proteus mirabilis is a bacterium commonly found in the environment and is also known to cause opportunistic infections, especially in the urinary tract. The discovery of new variants of SGI1 within Proteus mirabilis is critical because it suggests that this bacterium may act as a key hub for the evolution and dissemination of antibiotic resistance. This means that Proteus mirabilis can acquire, adapt, and transfer resistance genes to other bacteria. This has serious implications for public health, as infections caused by resistant Proteus mirabilis strains will be harder to treat, increasing the risk of complications and potentially death.

How do the different SGI1 variants impact antibiotic resistance?

The different SGI1 variants, such as SGI1-PmCAU, SGI1-PmABB, SGI1-PmJN16, SGI1-PmJN40, and SGI1-PmJN48, have unique structural characteristics. These variations lead to differences in the types of antibiotics and heavy metals the bacteria can resist. For instance, SGI1-PmJN16 has a novel gene cassette array, and SGI1-PmJN40 can form extrachromosomal DNA circles for dissemination. These structural changes broaden the range of resistance and can facilitate the transfer of these genes to other bacteria. This makes infections more difficult to treat and exacerbates the spread of antibiotic resistance.

What measures are being taken to combat the spread of antibiotic resistance?

Combating the spread of antibiotic resistance involves several key strategies. Researchers are working to identify and characterize genomic island variants like SGI1 to understand how resistance evolves. This knowledge is crucial for developing targeted interventions. These interventions include improving hygiene practices to reduce bacterial transmission, developing new antibiotics to overcome resistance, and implementing stricter regulations on antibiotic use to prevent overuse. Supporting these efforts is vital to protecting public health and ensuring that antibiotics remain effective.