Gemella sanguinis Bacteremia Associated with a Hemodialysis Catheter in an Immunocompromised Patient with End-Stage Renal Disease: A Case Report

Bacteriemia por Gemella sanguinis asociada a catéter de hemodiálisis en un paciente inmunocomprometido con enfermedad renal crónica terminal. Reporte de caso

Abstract

Introduction: Gemella sanguinis is a facultative anaerobic Gram-positive coccus that is part of the commensal microbiota of the oral cavity and the gastrointestinal tract. Although primarily associated with infectious endocarditis, it may act as an opportunistic pathogen in hosts with predisposing conditions.

Case presentation: A 31-year-old female with a history of heart failure, type 1 diabetes mellitus, end-stage renal disease (ESRD) on hemodialysis, and iron deficiency anemia presented to the emergency department due to abdominal, lumbar and joint pain, diarrhea, fever, chills, and general weakness and malaise over the last 24 hours. Polymicrobial infectious endocarditis due to Enterobacter cloacae and Enterococcus faecalis was documented and successfully treated with ertapenem (1g intravenous every 24 hours) + ampicillin (2g intravenous every 12 hours), resulting in her discharge after 28 days of hospitalization. However, 29 days later, she was readmitted to the emergency department due to fever (39.1°C) and hypotension (101/56mmHg) refractory to crystalloids. On the same day of readmission, empirical management was initiated with vancomycin (1g intravenous [IV] loading dose, followed by 500mg IV every 48 hours adjusted to renal function until completing 14 doses) and meropenem (1g IV every 12 hours, adjusted to 500mg IV every 12 hours). During this second stay, Gram-positive cocci (G. sanguinis) were isolated in all serial blood cultures (bottles 1, 2, 3, and 4), confirming dialysis catheter-associated bacteremia. After adjusting the antibiotic treatment, the patient’s condition evolved favorably, and she was discharged 6 days after readmission in stable clinical condition.

Conclusion: G. sanguinis can behave as an aggressive opportunistic pathogen in patients with immunosuppression secondary to ESRD. This report highlights the need for further microbiological characterization and strengthens the evidence regarding the clinical behavior of this microorganism.

Resumen

Introducción. Gemella sanguinis es un coco grampositivo, anaerobio facultativo, que forma parte de la microbiota comensal de la cavidad oral y del tracto gastrointestinal. Aunque se asocia principalmente a endocarditis infecciosa, puede actuar como patógeno oportunista en huéspedes con condiciones predisponentes.

Presentación del caso. Mujer de 31 años con insuficiencia cardíaca, diabetes mellitus tipo 1, enfermedad renal terminal (ERT) en hemodiálisis y anemia ferropénica, quien inicialmente asistió al servicio de urgencias por dolor abdominal, lumbar y articular, diarrea, fiebre, escalofríos y debilidad y malestar general durante las últimas 24 horas. Se documentó endocarditis infecciosa polimicrobiana por Enterobacter cloacae y Enterococcus faecalis, tratada exitosamente con ertapenem (1g intravenoso cada 24 horas) + ampicilina (2g intravenoso cada 12 horas). La paciente fue dada de alta tras 28 días de hospitalización. A los 29 días del egreso, reingresó a urgencias por fiebre (39.1°C) e hipotensión (101/56mmHg) refractaria a cristaloides. El mismo día del reingreso, se inició manejo empírico con vancomicina (dosis de carga de 1g intravenoso [IV], seguida de 500mg IV cada 48 horas ajustada a la función renal hasta completar 14 dosis) y meropenem (1g IV cada 12 horas, ajustado a 500mg IV cada 12 horas). Durante esta segunda estancia, se aislaron cocos grampositivos (G. sanguinis) en todos los hemocultivos seriados (frascos 1, 2, 3 y 4), lo que confirmó una bacteriemia asociada a catéter de diálisis. Tras el ajuste del tratamiento antibiótico, la paciente evolucionó favorablemente y fue dada de alta a los 6 días del reingreso en adecuadas condiciones clínicas.

Conclusión. G. sanguinis puede comportarse como un patógeno oportunista agresivo en pacientes con inmunosupresión secundaria a ERT. El presente reporte resalta la necesidad de profundizar en la caracterización microbiológica y fortalece la evidencia sobre el comportamiento clínico de este microorganismo.

Introduction

Species of the genus Gemella are facultative anaerobic, non-spore-forming Gram-positive cocci that are catalase and oxidase negative. When grown in culture media, they typically cluster in pairs, tetrads, or short chains (1-5). These bacteria are commensal organisms found in the oral cavity, upper respiratory tract, and gastrointestinal tract (1,3,4), but they are rare causes of human disease (4).

Currently, seven Gemella species are recognized: Gemella haemolysans, Gemella morbillorum, Gemella bergeri, Gemella sanguinis, Gemella asaccharolytica, Gemella palaticanis, and Gemella cuniculi, though the latter two are found exclusively in animals (6). G. sanguinis, the most recently identified species (1998) (1,2), has been primarily described in association with infective endocarditis (1-4,7).

Gemella species belong to the resident microbiota of human mucous membranes, particularly in the oral cavity and upper digestive tract (1). Despite this, they can act as opportunistic pathogens in immunocompromised individuals, such as those with end-stage renal disease (ESRD)—a condition associated with immune system dysfunction (8). In the literature, Gemella infections have been mainly described in patients with predisposing factors, including valvular heart disease, invasive procedures, and underlying comorbidities (1-4,9,10). Less frequently, some Gemella species have been identified as causative agents of invasive infections, such as meningitis, and other systemic conditions (11).

Variability in beta-lactam susceptibility has been reported among Gemella species. Nevertheless, third-generation cephalosporins have shown superior activity compared to penicillin (12). Similarly, evidence indicates that all Gemella species are susceptible to vancomycin, gentamicin, and teicoplanin (9,12).

Despite its low prevalence, the incidence of G. sanguinis infections may be underestimated due to challenges in microbiological identification, as its morphology can often be confused with other Gram-positive cocci such as Streptococcus or Enterococcus (5). Advances in rapid identification technologies, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and molecular panels, have optimized microbial detection and speciation in recent years. This has allowed for better recognition of the role of certain microorganisms as opportunistic pathogens in susceptible populations (7,9).

Case presentation

A 31-year-old female with heart failure and preserved left ventricular ejection fraction (LVEF) of 56%, type 1 insulin-dependent diabetes mellitus, end-stage renal disease (ESRD) on hemodialysis, and iron deficiency anemia presented to the emergency department of a quaternary care hospital in Tunja, Colombia, on August 22, 2024. She reported abdominal, lumbar, and joint pain, multiple episodes of watery diarrhea without blood, fever, chills, weakness, and general malaise over the previous 24 hours. The patient also reported dyspnea at rest during the last week.

The physical examination upon admission revealed an alert patient in acceptable general condition with a temperature of 39.3°C, a heart rate of 102bpm, and 95% oxygen saturation requiring 2L/min of supplemental oxygen. A left jugular hemodialysis catheter was well-positioned, and mild lower limb edema was noted. Auscultation detected a systolic murmur audible in all cardiac areas and fine crackles at both lung bases.

Admission laboratory tests showed mild leukocytosis (11 200/µL) with neutrophilia (8 870/µL), normocytic anemia (Hb: 9.7g/dL), mild thrombocytopenia (199 000/µL), and renal function impairment consistent with ESRD. Additionally, alterations in coagulation times and elevated inflammatory markers were reported.

Based on these clinical findings, a chest X-ray was requested, showing cardiomegaly. An abdominal ultrasound—technically limited by abundant intestinal gas—revealed hepatosplenomegaly, gallbladder wall edema with anechoic content, free fluid in the abdominal cavity, and signs of non-obstructive bilateral nephropathy. Due to multisystem involvement and suspected infection, the patient was hospitalized.

On August 23, blood cultures isolated Enterobacter cloacae and Enterococcus faecalis, confirming the diagnosis of bacterial endocarditis. The following day, a 42-day antibiotic regimen was initiated with IV ertapenem (1g every 24 hours) and IV ampicillin (2g every 12 hours).

A transesophageal echocardiogram performed on August 26 showed the dialysis catheter positioned in the right atrium. At the tip of the device, an area of hyperechogenicity and a 0.5 cm thickening compatible with vegetation were observed, along with a mobile hyperechogenic image measuring 0.6 x 0.4 cm.

The patient’s condition improved significantly with treatment. Consequently, she was discharged on September 19 with instructions for management at her renal unit and to continue antibiotic treatment at home until the regimen was complete. She was also instructed to undergo weekly blood counts and C-reactive protein (CRP) tests, and to return to the emergency department if fever or chills recurred.

On October 18, the patient had a new admission to the emergency department, referred from her renal unit due to fever (39.1°C) and hypotension (101/56 mmHg) that did not improve with crystalloid administration. She reported fatigue, weakness, chills, and muscle pain starting the previous day.

Upon physical examination, the patient was alert with blood pressure of 101/56mmHg, mean arterial pressure of 71mmHg, heart rate of 100bpm, respiratory rate of 20rpm, temperature of 37°C, and 86% oxygen saturation with a fraction of inspired oxygen (FiO2) of 24%. Lung auscultation identified alveolar hypoventilation in the lower right lung.

Admission laboratory tests (Table 1) showed arterial gases with metabolic alkalosis but no evidence of pulmonary dysfunction or signs of hypoperfusion. A marked elevation of procalcitonin (39.77ng/mL) was noted. On the same day of readmission, antibiotic therapy was initiated with IV vancomycin (1g loading dose, followed by 500mg every 48 hours adjusted for renal function until completing 14 doses) and IV meropenem (1g every 12 hours, adjusted to 500mg).

Table 1. Admission laboratory tests.

Test	Result	Reference values
Creatinine	3.52mg/dL	0.51-0.95mg/dL
Blood urea nitrogen (BUN)	15.74mg/dL	10-20mg/dL
Procalcitonin	39.77ng/mL (positive)	>0.25ng/mL (high)
Sodium	138mEq/L	135-145mEq/L
Potassium	4.1mEq/L	3.4-5.4mEq/L
Chloride	103mEq/L	95-105mEq/L
Thyroid-stimulating hormone (TSH)	1µUI/mL	0.271-4.201µUI/mL
Free T4	1.10ng/dL	1.3-1.7ng/dL
Transferrin	141mg/dL	200-380mg/dL
Ferritin	377.30ng/mL	11-307ng/mL
Leukocytes	11 200/µL	4 5000-11 300/µL
Neutrophils	8 870/µL	2 250-8 480/µL
Hemoglobin	9.7g/dL	12.30-15.30g/dL
Hematocrit	30.4%	35-47%
Platelets	199 000 /µL	150 00-450 000/µL

Source: Own elaboration.

Upon admission, serial blood cultures were also collected and a chest X-ray was performed, which showed peripheral reticulogranular opacities in both lung fields without other significant alterations.

On October 20, blood culture reports (bottles 2 and 4) revealed the growth of Gram-positive cocci, suggesting dialysis catheter-associated bacteremia. Consequently, the antibiotic regimen was adjusted by discontinuing meropenem. On the same day, a FilmArray BCID2 blood panel was performed with a negative result. The following day, a transthoracic echocardiogram showed mild concentric left ventricular hypertrophy, grade II diastolic dysfunction, mild ventricular dilation, and a mild pericardial effusion without hemodynamic repercussions. No findings of active endocarditis or evidence of masses or thrombi were identified.

On October 22, Gram-positive cocci were isolated in all blood cultures (bottles 1, 2, 3, and 4) and identified as G. sanguinis, confirming hemodialysis catheter-associated bacteremia (Figure 1). Two days later, a follow-up transesophageal echocardiogram showed mild concentric left ventricular remodeling with preserved systolic function (LVEF 59%), normal diastolic function, minimal aortic and mitral regurgitation, and grade 1 tricuspid regurgitation. Notably, this study showed no images compatible with endocarditis.

Figure 1. Small, circular, non-pigmented, and translucent-to-opaque bacterial colonies on a blood agar plate.

Source: Image obtained while conducting the study.

The patient was discharged 6 days after admission. She received instructions for outpatient follow-up, including an evaluation by dentistry or maxillofacial surgery regarding periodontal disease, and was educated on recognizing red flags such as fever or chills. Figure 2 presents the timeline of the medical care provided to the patient.

Figure 2. Timeline of the patient’s clinical course and therapeutic management.

Source: Own elaboration

Discussion

In patients with ESRD, infections are a leading cause of morbidity and mortality, representing the second most common cause of death in this population (8). Evidence indicates that both the innate and adaptive immune systems are impaired in patients with ESRD, increasing susceptibility to infections and virus-associated cancers while diminishing vaccine response. Consequently, the mortality risk due to sepsis in hemodialysis patients is approximately 250-fold higher than in the general population (8). Furthermore, this immune dysfunction involves an increased production and a decreased clearance of proinflammatory cytokines, which promotes a chronic proinflammatory state (8).

Due to its low prevalence, literature on G. sanguinis infections is scarce, with reports primarily focusing on infective endocarditis (1-4,10) and, to a lesser extent, pericarditis, meningitis (6), and extra-abdominal infections (11). Following a literature review, no previous cases of infection by this pathogen in patients with ESRD were found. Therefore, to our knowledge, this report constitutes the first documented case of G. sanguinis bacteremia in a patient with ESRD.

The treatment described for G. sanguinis includes the use of aminoglycosides (especially gentamicin), as well as glycopeptides such as vancomycin and teicoplanin (9,12). In the present case, the patient responded satisfactorily to management with vancomycin.

While G. sanguinis has not been shown to possess intrinsic virulence with high lethal potential, it can behave as an opportunistic pathogen in immunocompromised patients—such as those with ESRD or predisposing factors like valvular alterations, neoplasms, or invasive procedures—, so it is frequently associated with valvular pathologies or oral conditions such as ulcers, caries, or periodontal disease. In these cases, the risk of mortality from infections increases significantly due to the previously mentioned immunosuppression mechanisms (2,8,9). Nevertheless, previous reports have not specifically addressed ESRD as a predisposing factor associated with immunosuppression, even though this condition constitutes a state of immune dysfunction (8), which highlights the clinical relevance of the present case.

Conclusion

G. sanguinis can act as an opportunistic pathogen in immunocompromised patients. In this regard, the present case highlights the importance of maintaining a high index of suspicion for unusual pathogens in patients with multiple comorbidities, especially those in chronic hemodialysis programs. Furthermore, it emphasizes the need to include ESRD as a relevant immunosuppressive condition in the medical literature, both to guide the clinical management of these patients and to generate new lines of research regarding susceptibility to infections.

Conflicts of interest

None stated by the authors.

Funding

None stated by the authors.

Acknowledgments

None stated by the authors.

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