Viridans Group Streptococci

Emery Haley, PhD, Scientific Writer

CHECK BACK SOON FOR OUR FULL BLOG ON THE IMPORTANCE OF VIRIDANS GROUP STREPTOCOCCI

Subscribe to our emails and get notified as soon as new blogs are published.

Clinical Summary

C. koseri is recognized as a classical gram-negative, urease-variable, biofilm-forming uropathogen. 
C. koseri is associated with complicated UTI in older adult and pediatric populations. 
In symptomatic UTI patients, C. koseri: 
- Is not a contaminant (is found in catheter-collected urine specimens). 
- Is viable (can grow out on culture). 
- Is pathogenic (associated with elevated urine biomarkers of infection). 
Reported severe complications of C. koseri UTI include pyelonephritis, polymicrobial bacteremia, and urosepsis. 
Multidrug-resistant C. koseri (especially among hospital-acquired UTIs) is a significant global health threat.

Bacterial Characteristics

Gram-stain

Gram-negative

Morphology

Bacillus

Growth Requirements

Non-fastidious (grows well in standard urine culture conditions)
Facultative anaerobe

Nitrate Reduction

Yes

Urease

Variable

Biofilm Formation

Yes

Pathogenicity

Colonizer or Pathobiont

Clinical Relevance in UTI

C. koseri is a urease-variable microorganism [1] capable of forming biofilms. C. koseri is typically considered to be among the common classical uropathogens in older adults,[2]  but is also being increasingly recognized as common in pediatric UTIs.[3]

In a study of older adult males and females with clinically suspected complicated UTI, C. koseri was detected in both midstream voided and in-and-out-catheter collected specimens indicating that it was truly present in the bladder, not simply a contaminant picked up during voiding.[4]  Furthermore, elevated markers of immune system activation in the urinary tract have been measured from the same clinical urine specimens in which C. koseri was detected, indicating that the presence of C. koseri was associated with an immune response to urinary tract infection.[5–7]   Hospital-acquired C. koseri UTIs pose a particularly serious threat, as these infections increasingly display multidrug- or pandrug-resistance.[8]  Severe complications of C. koseri UTI, including pyelonephritis, polymicrobial bacteremia, and urosepsis, have been reported.[9–11]

Hospital-acquired C. koseri UTIs pose a particularly serious threat, as these infections increasingly display multidrug- or pandrug-resistance.[8]  Although not considered one of the six highest priority “ESKAPE” pathogens, The World Health Organization (WHO) has included this organism in the 2024 Bacterial Priority Pathogens List (BPPL).[111] Severe complications of C. koseri UTI, including pyelonephritis, polymicrobial bacteremia, and urosepsis, have been reported.[9–11] 

Together, these findings indicate that C. koseri should be seriously considered as a uropathogen and demonstrate the value of detecting this organism, particularly in individuals with recurrent UTI and/or risk factors for persistent or complicated UTI.

Treatment

Evidence of Efficacy (Checkmarks): Amoxicillin/Clavulanate, Ampicillin/Sulbactam, Cefaclor, Cefazolin, Cefepime, Cephalexin, Ceftazidime, Ceftriaxone, Ciprofloxacin, Gentamicin, Levofloxacin, Meropenem, Nitrofurantoin, Piperacillin/Tazobactam, Sulfamethoxazole/Trimethoprim, and Trimethoprim.

References

1. Archer, G.T.L. Streptococcus Viridans in Urine. J. R. Army Méd. Corps 1938, 70, 97, doi:10.1136/jramc-70-02-03.
2. Andrewes, F.W.; Horder, T.J. A STUDY OF THE STREPTOCOCCI PATHOGENIC FOR MAN. Lancet 1906, 168, 852–855, doi:10.1016/s0140-6736(01)43302-2.
3. Thomas-White, K.; Forster, S.C.; Kumar, N.; Kuiken, M.V.; Putonti, C.; Stares, M.D.; Hilt, E.E.; Price, T.K.; Wolfe, A.J.; Lawley, T.D. Culturing of Female Bladder Bacteria Reveals an Interconnected Urogenital      Microbiota. Nat Commun 2018, 9, 1557, doi:10.1038/s41467-018-03968-5.
4. Chen, Y.B.; Hochstedler, B.; Pham, T.T.; Acevedo-Alvarez, M.; Mueller, E.R.; Wolfe, A.J. The Urethral Microbiota: A Missing Link in the Female Urinary Microbiota. J Urol 2020, 204, 303–309, doi:10.1097/ju.0000000000000910.
5. Komesu, Y.M.; Dinwiddie, D.L.; Richter, H.E.; Lukacz, E.S.; Sung, V.W.; Siddiqui, N.Y.; Zyczynski, H.M.; Ridgeway, B.; Rogers, R.G.; Arya, L.A.; et al. Defining the Relationship between Vaginal and Urinary Microbiomes. Am. J. Obstet. Gynecol. 2020, 222, 154.e1-154.e10, doi:10.1016/j.ajog.2019.08.011.
6. Jacobs, K.M.; Price, T.K.; Thomas-White, K.; Halverson, T.; Davies, A.; Myers, D.L.; Wolfe, A.J. Cultivable Bacteria in Urine of Women With Interstitial Cystitis: (Not) What We Expected. Female Pelvic Med. Reconstr. Surg. 2021, 27, 322–327, doi:10.1097/spv.0000000000000854.
7. Pearce, M.M.; Zilliox, M.J.; Rosenfeld, A.B.; Thomas-White, K.J.; Richter, H.E.; Nager, C.W.; Visco, A.G.; Nygaard, I.E.; Barber, M.D.; Schaffer, J.; et al. The Female Urinary Microbiome in Urgency Urinary Incontinence. Am J Obstet Gynecol 2015, 213, 347.e1-347.e11, doi:10.1016/j.ajog.2015.07.009.
8. Price, T.K.; Hilt, E.E.; Dune, T.J.; Mueller, E.R.; Wolfe, A.J.; Brubaker, L. Urine Trouble: Should We Think Differently about UTI? Int Urogynecol J 2018, 29, 205–210, doi:10.1007/s00192-017-3528-8.
9. Price, T.K.; Dune, T.; Hilt, E.E.; Thomas-White, K.J.; Kliethermes, S.; Brincat, C.; Brubaker, L.; Wolfe, A.J.; Mueller, E.R.; Schreckenberger, P.C. The Clinical Urine Culture: Enhanced Techniques Improve Detection of Clinically Relevant Microorganisms. Journal of Clinical Microbiology 2016, 54, 1216–1222, doi:10.1128/jcm.00044-16.
10. Hochstedler-Kramer, B.; Joyce, C.; Abdul-Rahim, O.; Barnes, H.C.; Mueller, E.R.; Wolfe, A.J.; Brubaker, L.; Burnett, L.A. One Size Does Not Fit All: Variability in Urinary Symptoms and Microbial Communities. Front. Urol. 2022, 2, 890990, doi:10.3389/fruro.2022.890990.
11. Moreland, R.B.; Choi, B.I.; Geaman, W.; Gonzalez, C.; Hochstedler-Kramer, B.R.; John, J.; Kaindl, J.; Kesav, N.; Lamichhane, J.; Lucio, L.; et al. Beyond the Usual Suspects: Emerging Uropathogens in the Microbiome Age. Frontiers in Urology 2023, 3, doi:10.3389/fruro.2023.1212590.
12. Guerrero-Del-Cueto, F.; Ibanes-Gutiérrez, C.; Velázquez-Acosta, C.; Cornejo-Juárez, P.; Vilar-Compte, D. Microbiology and Clinical Characteristics of Viridans Group Streptococci in Patients with Cancer. Braz. J. Infect. Dis. 2018, 22, 323–327, doi:10.1016/j.bjid.2018.06.003.
13. Prasad, A.; Ene, A.; Jablonska, S.; Du, J.; Wolfe, A.J.; Putonti, C. Comparative Genomic Study of Streptococcus Anginosus Reveals Distinct Group of Urinary Strains. mSphere 2023, 8, e00687-22, doi:10.1128/msphere.00687-22.
14. Miller, S.; Miller-Ensminger, T.; Voukadinova, A.; Wolfe, A.J.; Putonti, C. Draft Genome Sequence of Streptococcus Anginosus UMB7768, Isolated from a Woman with Recurrent UTI Symptoms. Microbiol. Resour. Announc. 2020, 9, e00418-20, doi:10.1128/mra.00418-20.
15. Wu, H.; Zheng, R. Splenic Abscess Caused by Streptococcus Anginosus Bacteremia Secondary to Urinary Tract Infection: A Case Report and Literature Review. Open Med. 2020, 15, 997–1002, doi:10.1515/med-2020-0117.
16. Chang, K.-M.; Hsieh, S.L.; Koshy, R. An Unusual Case of Streptococcus Anginosus Endocarditis in a Healthy Host With Bicuspid Aortic Valve. Cureus 2021, 13, e13171, doi:10.7759/cureus.13171.
17. Finn, T.; Schattner, A.; Dubin, I.; Cohen, R. Streptococcus Anginosus Endocarditis and Multiple Liver Abscesses in a Splenectomised Patient. BMJ Case Rep. 2018, 2018, bcr-2018-224266, doi:10.1136/bcr-2018-224266.
18. Mores, C.R.; Price, T.K.; Wolff, B.; Halverson, T.; Limeira, R.; Brubaker, L.; Mueller, E.R.; Putonti, C.; Wolfe, A.J. Genomic Relatedness and Clinical Significance of Streptococcus Mitis Strains Isolated from the Urogenital Tract of Sexual Partners. Microb Genom 2021, 7, mgen000535, doi:10.1099/mgen.0.000535.
19. Chou, Y.-S.; Horng, C.-T.; Huang, H.-S.; Hu, S.-C.; Chen, J.-T.; Tsai, M.-L. Reactive Arthritis Following Streptococcus Viridans Urinary Tract Infection. Ocul. Immunol. Inflamm. 2010, 18, 52–53, doi:10.3109/09273940903414517.
20. Ong, G.; Barr, J.G.; Savage, M. Streptococcus Mitis: Urinary Tract Infection in a Renal Transplant Patient. J. Infect. 1998, 37, 91–92, doi:10.1016/s0163-4453(98)91421-9.
21. Zhang, B.; Zhou, J.; Xie, G.; Zhang, L.; Zhang, Y.; Xu, K.; Feng, T.; Yang, S. A Case of Urinary Tract Infection Caused by Multidrug Resistant Streptococcus Mitis/Oralis. Infect. Drug Resist. 2023, 16, 4285–4288, doi:10.2147/idr.s416387.
22. Ren, J.; Sun, P.; Wang, M.; Zhou, W.; Liu, Z. Insights into the Role of Streptococcus Oralis as an Opportunistic Pathogen in Infectious Diseases. Front. Cell. Infect. Microbiol. 2024, 14, 1480961, doi:10.3389/fcimb.2024.1480961.
23. Basaranoglu, S.T.; Ozsurekci, Y.; Aykac, K.; Aycan, A.E.; Bıcakcigil, A.; Altun, B.; Sancak, B.; Cengiz, A.B.; Kara, A.; Ceyhan, M. Streptococcus Mitis/Oralis Causing Blood Stream Infections in Pediatric Patients. Jpn. J. Infect. Dis. 2019, 72, 1–6, doi:10.7883/yoken.jjid.2018.074.
24. Kotani, A.; Oda, Y.; Hirakawa, Y.; Nakamura, M.; Hamasaki, Y.; Nangaku, M. Peritoneal Dialysis-Related Peritonitis Caused by Streptococcus Oralis. Intern. Med. 2021, 60, 3447–3452, doi:10.2169/internalmedicine.6234-20.
25. Seo, H.; Hyun, J.; Kim, H.; Park, S.; Chung, H.; Bae, S.; Jung, J.; Kim, M.J.; Kim, S.-H.; Lee, S.-O.; et al. Risk and Outcome of Infective Endocarditis in Streptococcal Bloodstream Infections According to Streptococcal Species. Microbiol. Spectr. 2023, 11, e01049-23, doi:10.1128/spectrum.01049-23.
26. Cardoso, J.; Ferreira, D.; Assis, R.; Monteiro, J.; Coelho, I.; Real, A.; Catorze, N. Streptococcus Oralis Meningitis. Eur. J. Case Rep. Intern. Med. 2021, 8, 002349, doi:10.12890/2021_002349.
27. Poulsen, L.; Bisgaard, M.; Son, N.; Trung, N.; An, H.; Dalsgaard, A. Enterococcus and Streptococcusspp. Associated with Chronic and Self-Medicated Urinary Tract Infections in Vietnam. BMC Infectious Diseases 2012, 12, 320, doi:10.1186/1471-2334-12-320.
28. Li, Y.; Chen, X.; Zhang, Z.; Wang, L.; Wang, J.; Zeng, J.; Yang, J.; Lu, B. Microbiological and Clinical Characteristics of Streptococcus Gallolyticus Subsp. Pasteurianus Infection in China. BMC Infect. Dis. 2019, 19, 791, doi:10.1186/s12879-019-4413-5.
29. Teresa-Alguacil, J. de; Gutiérrez-Soto, M.; Rodríguez-Granger, J.; Osuna-Ortega, A.; Navarro-Marí, J.M.; Gutiérrez-Fernández, J. Clinical Interest of Streptococcus Bovis Isolates in Urine. Rev. espanola Quimioter. : publicacion Of. Soc. Espanola Quimioter. 2016, 29, 155–158.
30. Pereira, C.; Nogueira, F.; Marques, J.C.; Ferreira, J.P.; Almeida, J.S. Endocarditis by Streptococcus Pasteurianus. Cureus 2023, 15, e34529, doi:10.7759/cureus.34529.
31. Matesanz, M.; Rubal, D.; Iñiguez, I.; Rabuñal, R.; García-Garrote, F.; Coira, A.; García-País, M.J.; Pita, J.; Rodriguez-Macias, A.; López-Álvarez, M.J.; et al. Is Streptococcus Bovis a Urinary Pathogen? Eur. J. Clin. Microbiol. Infect. Dis. 2015, 34, 719–725, doi:10.1007/s10096-014-2273-x.
32. Zou, D.; Li, F.; Jiao, S.-L.; Dong, J.-R.; Xiao, Y.-Y.; Yan, X.-L.; Li, Y.; Ren, D. Infantile Bacterial Meningitis Combined with Sepsis Caused by Streptococcus Gallolyticus Subspecies Pasteurianus: A Case Report. World J. Clin. Cases 2024, 12, 6472–6478, doi:10.12998/wjcc.v12.i31.6472.
33. BacDive | The Bacterial Diversity Metadatabase Available online: https://bacdive.dsmz.de/ (accessed on 11 February 2025).
34. BioCyc Pathway/Genome Database Collection Available online: https://biocyc.org/ (accessed on 11 February 2025).
35. Wang, D.; Haley, E.; Luke, N.; Mathur, M.; Festa, R.; Zhao, X.; Anderson, L.A.; Allison, J.L.; Stebbins, K.L.; Diaz, M.J.; et al. Emerging and Fastidious Uropathogens Were Detected by M-PCR with Similar Prevalence and Cell Density in Catheter and Midstream Voided Urine Indicating the Importance of These Microbes in Causing UTIs. Infect. Drug Resist. 2023, Volume 16, 7775–7795, doi:10.2147/idr.s429990.
36. Haley, E.; Luke, N.; Mathur, M.; Festa, R.A.; Wang, J.; Jiang, Y.; Anderson, L.A.; Baunoch, D. The Prevalence and Association of Different Uropathogens Detected by M-PCR with Infection-Associated Urine Biomarkers in Urinary Tract Infections. Res. Rep. Urol. 2024, 16, 19–29, doi:10.2147/rru.s443361.
37. Akhlaghpour, M.; Haley, E.; Parnell, L.; Luke, N.; Mathur, M.; Festa, R.A.; Percaccio, M.; Magallon, J.; Remedios-Chan, M.; Rosas, A.; et al. Urine Biomarkers Individually and as a Consensus Model Show High Sensitivity and      Specificity for Detecting UTIs. BMC Infect Dis 2024, 24, 153, doi:10.1186/s12879-024-09044-2.
38. Parnell, L.K.D.; Luke, N.; Mathur, M.; Festa, R.A.; Haley, E.; Wang, J.; Jiang, Y.; Anderson, L.; Baunoch, D. Elevated UTI Biomarkers in Symptomatic Patients with Urine Microbial Densities of 10,000 CFU/ML Indicate a Lower Threshold for Diagnosing UTIs. MDPI 2023, 13, 1–15, doi:10.3390/diagnostics13162688.

About the Author

Dr. Emery Haley is a scientific writing specialist with over ten years of experience in translational cell and molecular biology. As both a former laboratory scientist and an experienced science communicator, Dr. Haley is passionate about making complex research clear, approachable, and relevant. Their work has been published in over 10 papers and focuses on bridging the gap between the lab and real-world patient care to help drive better health outcomes.

Urologists

Primary Care Physicians

Gastroenterologists

Gynecologists

Medical Directors

Post-Acute Care

Healthcare at Home

Urology Clinic

Immediate Care/Urgent Care

Telemedicine

Viridans Group Streptococci

CHECK BACK SOON FOR OUR FULL BLOG ON THE IMPORTANCE OF VIRIDANS GROUP STREPTOCOCCI

Clinical Summary

Bacterial Characteristics

Gram-stain

Morphology

Growth Requirements

Nitrate Reduction

Urease

Biofilm Formation

Pathogenicity

Clinical Relevance in UTI

Treatment

References

About the Author

Urologists

Primary Care Physicians

Gastroenterologists

Gynecologists

Medical Directors

Post-Acute Care

Healthcare at Home

Urology Clinic

Immediate Care/Urgent Care

Telemedicine

CHECK BACK SOON FOR OUR FULL BLOG ON THE IMPORTANCE OF VIRIDANS GROUP STREPTOCOCCI

Clinical Summary

Bacterial Characteristics

Gram-stain

Morphology

Growth Requirements

Nitrate Reduction

Urease

Biofilm Formation

Pathogenicity

Clinical Relevance in UTI

Treatment

References

About the Author

Related Posts

U. urealyticum

S. agalactiae

S. aureus