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Weaknesses in Sepsis-Causing Bacteria in Premature Babies

Baby feet wrapped in a cream blanket.
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Scientists from the University of East Anglia and the Quadram Institute have tracked the bacterial strains behind life-threatening sepsis seen in premature babies. Their study, published in the journal Microbial Genomics, reveals the mystery of how the bacteria survive and succeed in causing this condition.

Premature babies are highly vulnerable

Around 11% of babies are born premature around the globe. These infants are highly susceptible to life-threatening infections and their time in neonatal care can be crucial for their survival and overall well-being.


One of these life-threatening infections includes bacteria, which can lead to late-onset sepsis that occurs from three days after birth. This condition starts when the bacteria get into the bloodstream and begin to replicate, causing potentially fatal complications. Babies with late-onset sepsis often undergo longer treatment with higher antibiotic exposure and prolonged stays in the neonatal intensive care unit (NICU).

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There are multiple types of bacteria that cause late-onset sepsis in premature babies, however, the most common comes from the Staphylococcus family, which are typically found in the healthy skin microbiome. While mostly harmless, this group of bacteria can become dangerous when they reside inside the human body, especially in immunocompromised individuals.

One particular strain – known as Staphylococcus capitis NRCS-A – has been identified as the cause of many serious neonatal infections. Although this strain was first believed to have emerged in the 1960s, the current circulating strains have resistance to multiple antibiotics and reduced susceptibility to antiseptics that are used on the skin of newborn infants. NRCS-A has therefore become a strong area of research to begin to understand how this infection can be treated.

“There are still many questions to answer as to why NRCS-A has become so globally spread amongst NICUs. But, working out how NRCS-A can evade the host immune system, spread and survive can also give us a head start with many other Staphylococcal species that cause sepsis in immunocompromised people in NICU and intensive care units.”

Dr. Heather Felgate from the Quadram Institute.

How does NRCS-A spread so easily?

Professor Mark Webber and his team from the Quadram Institute and the University of East Anglia analyzed the genomes of hundreds of S. capitis isolates taken from the skin and gut of neonatal infants with and without late-onset sepsis.

They discovered that the NRCS-A strain was commonly identified in both the skin and gut samples taken from uninfected neonatal babies. However, when the genomes of the disease-causing strains were compared to strains that do not cause disease, they observed tiny genetic differences.

These disease-causing NRCS-A strains were found to carry a set of genes believed to promote their survival in the gut and on the skin to act as a secondary infection source in their host. These strains were also resistant to nisin, an antimicrobial compound produced by gut bacteria, and carried genes that allow them to scavage for essential metals that are hard for many bacteria to access in the gut. The researchers also found that these strains grew better in similar acidic conditions as seen in the gut.

How can we control NRCS-A?

The study identified several ways in which NRCS-A has adapted to survive in the gut microbiome and contributes globally to the pathogenesis of late-onset sepsis. Understanding how these strains “have become globally successful is crucial to understanding how bacteria evolve to colonize different environments, and to give us new ideas about how to reduce the risks of infection in vulnerable populations,” said Prof. Webber.

The metal-scavenging capability of NRCS-A could also potentially serve as a vulnerability that may be targeted for treatment. There is evidence suggesting that the administration of probiotic supplements to infants may reduce the incidence of late-onset sepsis by allowing probiotic bacteria to extract metals ahead of pathogenic bacteria.

“We hope this work can be the starting point for more research to develop better ways to protect newborn babies from the terrible consequences of infection.”

Prof. Mark Webber from the Quadram Institute.


1. Felgate H, Sethi D, Faust K, et al. Characterisation of neonatal Staphylococcus capitis NRCS-A isolates compared with non NRCS-A Staphylococcus capitis from neonates and adults. Microb. Genom. 2023. doi: 10.1099/mgen.0.001106

2. Walani SR. Global burden of preterm birth. Intl J Gynecology & Obste. 2020;150(1):31-33. doi: 10.1002/ijgo.13195


This article is a rework of a press release issued by the Microbiology Society. Material has been edited for length and content.