Microbiology Case Study: 68 Year Old Female with Streptococcus anginosus in a Tracheostomy Wound

Case History

A 68 year old female was admitted to our hospital for emergent tracheostomy due to airway obstruction. Her symptoms began months ago with cough, dysphagia, and hoarseness of voice, difficulty breathing, slowly growing neck mass, and weight loss. Surgical biopsy from the neck mass confirmed the presence of squamous cell carcinoma of the hypopharynx “stage IVB”.

Chest CT scan indicated the possibility of metastatic disease to the lungs. Recently, she experienced a slow onset of paraparesis and blurring of vision in her left eye, which raised a concern about the disease metastasized to the brain. Brain MRI was performed and came back negative for metastasis to the brain. Additionally, she is at risk of refeeding syndrome due to muscle wasting, cachexia, dysphagia, 25% body weight loss, and significant failure to thrive. Radiation oncologists recommended concurrent radiation with chemotherapy, with a prescribed 70 Gray of radiation dose.

Physical examinations showed bilateral coarse lung sounds. Prior to her presentation, she had been treated with docusate, hydrocodone-acetaminophen, morphine, ondansetron, and labetalol. Her past medical history was notable for essential hypertension and an extensive history of smoking 1 PPD for 45 years. She was also started on weekly carboplatin and paclitaxel for five weeks.

The surgical biopsy from the tracheostomy lesions was sent to the microbiology laboratory for bacterial culture. The Gram stain of the culture showed gram positive cocci in chains. After 48 hours of incubation, the cultures grew a pure culture of α-hemolytic colonies (Figure 1). The organism was identified as Streptococcus anginosus by MALDI-TOF mass spectrometry (VITEK MS).

Image 1. Alpha-hemolytic colonies of Streptococcus anginosus growing on Sheep Blood Agar (SBA) plate after 48 hours of incubation.

Discussion

Streptococcus anginosus group (SAG) “formerly named as streptococcus milleri” are members of the Viridians Streptococci group, which are known to cause endocarditis due to their ability to bind extracellular matrix proteins such as fibronectin, fibrinogen, and laminin, by facilitating bacterial adhesion to the heart valves.1

In general, SAG consists of three main strains: Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus. Streptococcus intermedius tends to be associated with central nervous system (CNS) infections, while S. anginosus is commonly found as commensals at the genitourinary and gastrointestinal systems.2 Since S. anginosus strains can be virulent due to its ability to survive in an acidic environment and cause systemic bacteremia, skin and soft tissue infections (SSTIs), osteomyelitis, and CNS infections, isolation of this organismfrom invasive sites should not be regarded as a contaminant. Besides, S. anginosus infection is occasionally associated with liver abscesses and colonic adenocarcinoma.3

Notably, the recovery of this organism from our patient’s tracheostomy biopsy wound indicates the likely association of S. anginosus and oral squamous cell carcinoma (OSCC). Sasaki M et al. demonstrated that the dental plaques in oral squamous cell carcinoma patients could act as a reservoir for SAG, which might cause significant DNA damage in oral mucosa, thus predisposing to accumulated mutations.4 Two other studies have also shown that SAG is recovered exclusively in oral squamous cell carcinoma patients compared to individuals without oropharyngeal cancer.5,6

SAG are usually susceptible to penicillin, ampicillin, or ceftriaxone, while sometimes they can be resistant to clindamycin.7 In our case, the patient received multiple doses of IV ampicillin-sulbactam and metronidazole in the emergency department. After S. anginosus had been identified from her tracheostomy wound, the patient was discharged on oral ampicillin-sulbactam, along with the carboplatin and paclitaxel treatment.

References

  1. Asam D, Spellerberg B. Molecular pathogenicity of Streptococcus anginosus. Mol Oral Microbiol. 2014;29(4):145-155. doi:10.1111/omi.12056
  2. Whiley RA, Beighton D, Winstanley TG, Fraser HY, Hardie JM. Streptococcus intermedius, Streptococcus constellatus, and Streptococcus anginosus (the Streptococcus milleri group): association with different body sites and clinical infections. J Clin Microbiol. 1992;30(1):243-244. doi:10.1128/JCM.30.1.243-244.1992.
  3. Masood U, Sharma A, Lowe D, Khan R, Manocha D. Colorectal Cancer Associated with Streptococcus anginosus Bacteremia and Liver Abscesses. Case Rep Gastroenterol. 2016;10(3):769-774. Published 2016 Dec 13. doi:10.1159/000452757
  4. Sasaki M, Yamaura C, Ohara-Nemoto Y, et al. Streptococcus anginosus infection in oral cancer and its infection route. Oral Dis. 2005;11(3):151-156. doi:10.1111/j.1601-0825.2005.01051.x
  5. Robayo DAG, Erira HAT, Jaimes FOG, Torres AM, Galindo AIC. Oropharyngeal Squamous Cell Carcinoma: Human Papilloma Virus Coinfection with Streptococcus anginosus. Braz Dent J. 2019;30(6):626-633. doi:10.1590/0103-6440201902805.
  6. Tateda M, Shiga K, Saijo S, Sone M, Hori T, Yokoyama J, Matsuura K, Takasaka T, Miyagi T. Streptococcus anginosus in head and neck squamous cell carcinoma: implication in carcinogenesis. Int J Mol Med. 2000 Dec;6(6):699-703. doi: 10.3892/ijmm.6.6.699. PMID: 11078831.
  7. Tracy M, Wanahita A, Shuhatovich Y, Goldsmith EA, Clarridge JE 3rd, Musher DM. Antibiotic susceptibilities of genetically characterized Streptococcus milleri group strains. Antimicrob Agents Chemother. 2001;45(5):1511-1514. doi:10.1128/AAC.45.5.1511-1514.2001.

-Ahmed Ismail Younes, MD., is a first year pathology (AP/CP) resident at the East Carolina University Brody School Medicine. He is interested in specializing in dermatopathology. He is also passionate about conducting translational research. In his spare time, Ahmed enjoys spending his time watching movies, baking homemade pizza, and playing soccer.

-Phyu M. Thwe, Ph.D., MLS (ASCP)CM is Technical Director/Technical Consultant at Vidant Medical Center Clinical Microbiology Laboratory. She completed a Clinical and Public Health Microbiology Fellowship through a CPEP-accredited program at the University of Texas Medical Branch (UTMB) in Galveston, Texas. She is interested in extrapulmonary tuberculosis pathophysiology and developing diagnostic algorithms.

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