Using a Virus to Keep Baby Spinach Safe from Harmful Bacteria

Jenn Hoskins
16th August, 2024

Using a Virus to Keep Baby Spinach Safe from Harmful Bacteria

Image Source: Natural Science News, 2024

Key Findings

  • Researchers at Seoul Women's University isolated a virus called phage SSP49 from sewage that specifically targets and kills Staphylococcus aureus
  • Phage SSP49 effectively inhibited the growth of S. aureus on baby spinach leaves, showing potential as a natural biocontrol agent in fresh produce
  • The phage is safe for food use as its genome lacks genes for bacterial toxicity, antibiotic resistance, or lysogen formation
Staphylococcus aureus is a notorious foodborne pathogen, often found in fresh produce, and is a common cause of food poisoning. Symptoms typically include abdominal pain, diarrhea, and vomiting. The overuse of antibiotics to control S. aureus has led to the rise of antibiotic-resistant strains, such as methicillin-resistant S. aureus (MRSA). This has necessitated the search for alternative methods to combat this pathogen. One promising alternative is the use of bacteriophages, which are viruses that specifically target and kill bacteria. A recent study conducted by researchers at Seoul Women's University has isolated a lytic phage named SSP49 that specifically infects S. aureus, showing potential as a biocontrol agent in fresh produce[1]. The study involved isolating phage SSP49 from a sewage sample and characterizing its morphological, biological, and genetic properties. Phage SSP49 belongs to the Straboviridae family and is part of the Caudoviricetes class. It demonstrated the ability to inhibit the growth of S. aureus for up to 30 hours in vitro and showed high specificity and a broad host range against various S. aureus strains. This high specificity is crucial as it ensures that the phage targets only S. aureus without affecting beneficial bacteria. Receptor analysis revealed that phage SSP49 uses cell wall teichoic acid as a host receptor. This finding aligns with previous research that highlighted the importance of wall teichoic acids in the cell wall structure of S. aureus. Wall teichoic acids are glycopolymers attached to the peptidoglycan layer of the bacterial cell wall and are vital for the bacterium's virulence and structural integrity[2]. The absence of wall teichoic acids can disrupt the localization and function of crucial proteins like penicillin-binding protein 4 (PBP4), leading to decreased peptidoglycan cross-linking and increased susceptibility to lysozyme[2]. Whole genome sequencing of phage SSP49 revealed a genome size of 137,283 base pairs with 191 open reading frames. Importantly, the genome did not contain genes associated with lysogen formation, bacterial toxicity, or antibiotic resistance, indicating that phage SSP49 is safe for use in food applications. This safety profile is essential for any potential biocontrol agent used in food, as it ensures that the phage does not introduce new risks. The study also tested the stability of phage SSP49 under various temperature and pH conditions, finding that it remained active and stable. Furthermore, phage SSP49 effectively inhibited the growth of S. aureus on baby spinach leaves at both 4°C and 25°C, with reductions of 1.2 and 2.1 log CFU/cm², respectively. This demonstrates the phage's practical application in real-world conditions, making it a viable option for controlling S. aureus contamination in fresh produce. Previous research has shown the effectiveness of PCR approaches using nuc-targeted primers for detecting S. aureus in food. These methods, combined with growth techniques, can improve the detection of S. aureus in various food matrices[3]. The use of phage SSP49 as a biocontrol agent could complement these detection methods by providing a means to actively reduce the presence of the pathogen in food products. Phage therapy has been recognized as a promising strategy in the fight against antimicrobial resistance. Understanding the receptors involved in phage adsorption can lead to the development of intelligent phage cocktails and new phage-derived antimicrobials[4]. The identification of cell wall teichoic acid as the receptor for phage SSP49 adds valuable knowledge to this field and could guide future research in designing effective phage therapies. In conclusion, the study conducted by Seoul Women's University demonstrates the potential of phage SSP49 as a natural biocontrol agent against S. aureus contamination in fresh produce. By targeting cell wall teichoic acids, phage SSP49 effectively inhibits the growth of S. aureus, offering a promising alternative to traditional antibiotics and contributing to the ongoing efforts to combat antibiotic-resistant bacteria.

AgricultureBiotechPlant Science

References

Main Study

1) Isolation, characterization, and application of a lytic bacteriophage SSP49 to control Staphylococcus aureus contamination on baby spinach leaves.

Published 15th August, 2024

https://doi.org/10.1016/j.foodres.2024.114848

Related Studies

2) Teichoic acids are temporal and spatial regulators of peptidoglycan cross-linking in Staphylococcus aureus.

https://doi.org/10.1073/pnas.1004304107

3) PCR-based procedures for detection and quantification of Staphylococcus aureus and their application in food.

Journal: Journal of applied microbiology, Issue: Vol 100, Issue 2, Feb 2006

4) Unlocking the next generation of phage therapy: the key is in the receptors.

https://doi.org/10.1016/j.copbio.2020.10.002


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