Bacterium in the Spotlight: Peptostreptococcus anaerobius

Peptostreptococcus anaerobius is a slow growing, Gram-positive anaerobic coccus (GPAC) found in the human oral, gastrointestinal and vaginal microbiome. The organism is mainly found in polymicrobial infections and is less commonly seen in monobacterial infections such as urinary tract infections, prosthetic and native endocarditis _[1,2] P. anaerobius is also a commensal of the rumen and is a hyper-ammonia- producing bacterium that can utilise amino acids as their sole carbon, nitrogen and energy source.

Research has shown that there is a correlation between the prevalence of certain bacteria and the incidence of colorectal cancer (CRC), through comparative analysis of faecal materials from CRC patients and healthy controls, one such organism being P. anaerobius. The organism preferentially infiltrates and adheres to the mucosa of CRC tissue, promoting tumorigenesis through the PCWBR2-integrin α2/β1 axis ₍₃₎.  Zhang et al (2023) recently investigated the potential to use P. anaerobius as a biomarker for CRC by studying 109 patients with CRC. As a baseline, they found 79.8% of CRC patients were positive for P. anaerobius compared to 55.4% of healthy controls. They then used this information to look at mortality during a follow up period and reported a higher mortality rate among patients who had higher abundance of P. anaerobius ₍₄₎.

P anaerobius may also contribute to chemoresistance in CRC. Gu et al (2023) implanted the colon cancer cell line MC-38 into mice to establish a tumour, and then treated the mice with P. anaerobius in conjunction with the chemotherapy agent oxaliplatin. Through quantitative PCR, they found that P. anaerobius preferentially accumulated within the tumour lesion and the bacterial presence significantly hindered the effectiveness of oxaliplatin compared to P. anaerobius-free controls _[5]. This chemoresistance is mediated by the recruitment of myeloid-derived suppressor cells (MDSCs) to the CRC tumour microenvironment as MDSCs were found to be more numerous in the P. anaerobius group _[5]. Moreover, IL-23 levels were also found to be elevated in the CRC mice treated with the bacteria _[5].

Written by DWS Microbiologist, Charlotte Austin

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References

1. Legaria M C, Nastro M, Camporro J, Heger F, Barberis C, Stecher D, Rodriguez C H, Vay C A (2021). Peptostreptococcus anaerobius: Pathogenicity, identification, and antimicrobial susceptibility. Review of monobacterial infections and addition of a case of urinary tract infection directly identified from a urine sample by MALDI-TOF MS. Anaerobe, 72, 102461.
2. Floch M (2020) Colorectal Neoplasia and the Colorectal Microbiome Dysplasia, Probiotics, and Fusobacteria. Academic Press
3. Long X, Wong CC, Tong L, Chu E, Szeto C, G, M, Coker O, Chan A, Chan F, Sung J, Yu J (2019) Peptostreptococcus anaerobius promotes colorectal carcinogenesis and modulates tumour immunity. Nature Microbiology 4, 2319–2330
4. Zhang Y, Fan K, Li L, He J, Sun Y (2023) Peptostreptococcus anaerobius is a potential diagnostic biomarker of colorectal cancer. Cellular and molecular Biology 0145-5680
5. Gu J, Lv X, Li W, Li G, He X, Zhang Y, Shi L, Zhang X (2023) Deciphering the mechanism of Peptostreptococcus anaerobius-induced chemoresistance in colorectal cancer: the important roles of MDSC recruitment and EMT activation. Frontiers in Immunology 1664-3224