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How do ‘superbugs’ occur?

This article introduces what superbugs are, how they occur, and the dangers of superbug-induced infections.
© BSAC

The term ‘superbugs’ describes a group of bacteria resistant to multiple (multi-resistant), or all (pan-resistant), commonly used and tested antibiotics. Multi- and pan-resistance is, however, seen against all antimicrobials for other microbes.

How do superbugs arise?

Superbugs commonly occur with overexposure to antibiotics, as a result of antibiotic overuse.

Intrinsic and acquired resistance mechanisms can be shared between bacteria via horizontal gene transfer, and how such movement of genetic material remains an important factor in the development of AMR.

With such positive selection pressures as antibiotics (especially when used inappropriately), bacteria resistant to the antibiotics being used survive the treatment of infections and can share acquired or intrinsic genes – some of which may encode different mechanisms of resistance.

Evolution of resistance to antibiotics by bacteria: resistant bacteria which fail to respond to antibiotic therapy persist and spread, infecting other individuals Evolution of resistance to antibiotics by bacteria. Image taken from Harvard University Special Edition on Infectious Disease.

If you require a screen-reader compatible version of the above image, it is available as a PDF.

Common superbugs

Some common superbugs include:

  • Methicillin-resistant Staphylococcus aureus (MRSA) – a form of S. aureus with resistance to penicillin-type antibiotics (e.g. methicillin)
  • Carbapenem-resistant Enterobacteriaceae (CRE) or carbapenemase-producing Enterobacteriaceae (CPE) – a family of Gram-negative bacteria (e.g. Escherichia coli, Klebsiella spp. and Salmonella spp.) with resistance to carbapenems (broad-spectrum penicillin class antibiotics).
  • Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae – bacteria producing carbapenem-degrading ESBL enzymes.
  • Vancomycin-resistant Enterococcus (VRE) – Enterococci bacteria with resistance to the antibiotic vancomycin.
  • Multidrug-resistant Pseudomonas aeruginosa – a common type of bacteria resistant to multiple antibiotics.
  • Multidrug-resistant Acinetobacter – a group of bacteria with resistance to multiple antibiotics.

The dangers of superbugs

When these common superbugs cause infections (such as endocarditis, pneumonia and sepsis), they become serious and/or life-threatening as the multi- and pan-resistant nature of superbugs to common antimicrobials means that readily-available treatment options are limited – alternative effective antibiotics/treatments are sought.

Other resistant microbes

For other resistant microbes, similar issues exist. For fungi, only three primary classes of antifungals are used in treating invasive infections; thus, resistance to just one drug class reduces treatment options by >33%.

With multi-resistant microbes commonly also showing increased virulence and an enhanced capacity to spread, superbugs pose a great threat to global health. In the next step, you will learn just how challenging these infections can be to manage in hospitals.

For more on superbugs, and other multi- and pan-resistant microbes, check out the full online course, from BASC, below.

© BSAC
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Introduction to Practical Microbiology

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