Prevotella buccae bacteremia in an immunocompetent host – A case report and review of the literature

INTRODUCTION

Prevotella spp. is common commensals on human mucosal surfaces and has been reported to cause localized infections. Bloodstream infection with Prevotella spp. is extremely rare and to date, only a few cases have been reported in the literature with Prevotella buccae infection. The paucity of data often leads to a dilemma in clinical management when encountering patients with such rare bacteremia. Here, we report the case of a patient with P. buccae bacteremia with a supplementary review of the literature to date.

CASE REPORT

A 74-year-old gentleman presented with complaints of worsening lethargy and non-vertiginous giddiness over a few days duration. He did not complain of any other systemic symptoms. He had a recent history of dental caries for which he was on follow-up with his dentist but did not have any recent dental intervention. He had a medical history of non-ischemic cardiomyopathy with a low ejection fraction of 27%, atrial fibrillation currently in sinus rhythm post-ablation, chronic kidney disease, and thyrotoxicosis post-ablation, now in a hypothyroid state. At presentation, his heart rate was 72 beats/min, blood pressure was 110/70 mm Hg, respiratory rate 18/min, and temperature 99.9 F. General examination was unremarkable except for poor oral hygiene and dental caries.

His systemic examination was unremarkable and there was no focal neurological deficit. His total white blood cell count (WBC) was elevated at 21,130/uL, with a significant left shift, hemoglobin, and platelet counts were normal. His metabolic panel was normal and his creatinine was at the baseline for his chronic kidney disease. Subsequent investigations revealed high C-reactive protein of 94.4 mg/L and procalcitonin of 41.9 ng/mL. Urine analysis was negative for pyuria, leukocyte esterase, and nitrites, and urine culture showed no growth. His chest roentgenography was unremarkable. A blood culture specimen was sent using BACTEC non-radiometric continuous monitoring blood culture system. At 48 h, his blood culture grew P. buccae. He underwent computed tomography scan of the abdomen and pelvis, which was negative for any abscess, or other sources of infection. Initially, he was commenced on intravenous augmentin empirically and it was continued as per the sensitivity report. He was advised to complete a course of 14 days per recommendations from the infectious disease team. Blood cultures repeated on day 5 of hospitalization were sterile. He completed the full course of antibiotics and had significant clinical improvement. Before discharge, his WBC count had returned to normal. On follow-up at the ambulatory clinic, he was well and symptom-free following the course of antibiotics.

DISCUSSION

The Prevotella genus derives its name from Prevol, a renowned French microbiologist. These Gram-negative, anaerobic, pleomorphic, pigmented, or non-pigmented rods were previously designated as Bacteroides spp.^[1] They are sensitive to bile salts and are differentiated from Bacteroides which can tolerate bile salt. The genus Prevotella now includes 50 species that ferment glucose and hydrolyze gelatin.^[2] These are common commensals on human mucosal surfaces including oral mucosa, the pharynx, the human intestinal microbiome, and the female genital tract.^[3] They have been reported in dental, oropharyngeal, pleuropulmonary, abdominal, and genitourinary infections as a part of mixed flora. Members of Prevotella spp. have also been reported to cause bacteremia, chronic sinusitis, brain abscess, spinal abscess, endocarditis, skin and soft-tissue infection including necrotizing fasciitis, peritonitis, empyema, and ventilator-associated pneumonia.^[4,5] Prevotella spp. has been identified to contribute to 0.1% of bloodstream infections.^[6,7]

P. buccae was described in 1982 as a Bacteroides buccae. The name buccae refers to its major habitat, mouth.^[1,2,8] It is non-pigmented and pentose fermenting, commonly implicated in oral, dental, and respiratory infections. Normally, it is a commensal but is thought to reach the bloodstream through a mucosal breach.^[1,9] To date, only a few cases of P. buccae infection have been reported in the literature, of these three had evidence of bacteremia [Table 1]. Both sexes were involved equally. Among the reported patients, only one was immunodeficient. Three of these patients were immunocompetent and had a breach in the integrity of oral mucosal in the form of mucositis, dental treatment, or extraction. Two of them had oropharyngeal involvement, one patient had a right ileorenal vascular graft infection, and one had a breast abscess respectively. Our patient however is the oldest patient to be reported to have P. buccae bacteremia and is the first patient with bacteremia without any obvious dental procedure or a breach in the integrity of oral mucosa. Most of these patients were treated with augmentin similar to our patient and had complete clinical recovery. Piperacillin and Tazobactam were used in one patient. Metronidazole resistance was reported in one of these patients.^[1,10-13]

CONCLUSION

Prevotella spp. is a normal commensal of the oral cavity associated with odontogenic infection. P. buccae can cause bacteremia in immunocompetent patients following a breach in oral mucosal integrity following mucositis, dental caries, and extraction. Even though the site of infection could be identified in most patients, bacteremia without any identifiable foci of infection can also occur. Clinical response to treatment with augmentin is optimal. Mortality is reduced with the identification of the organism and prompt initiation of the appropriate antibiotics, hence the importance of early diagnosis and intervention.