Microbiology Case Study–Infection at Wisdom Tooth Extraction Site

Clinical

56 year old male with stage IV chronic kidney disease, hypertension, and gout who underwent a left lower wisdom tooth extraction presented two days post-op with throbbing pain on left side of his face and neck, dysphagia and dyspnea. He was sent to an outside ED by his dentist. He was given 900 mg of clindamycin, a dose of steroids and pain management and was sent to our institution. Surgical site was intact, but there was massive swelling of the floor of the mouth, submandibular gland, and neck. Symptoms worsened despite being given IV clindamycin. Infectious disease was consulted he was started on meropenem and blood cultures were drawn.

Microbiology

Two anaerobic blood culture bottles became positive at 48 and 61 hours.

Gram stain:

Gram stain of organism 1
Gram stain of organism 1

 

Gram stain of organism 2
Gram stain of organism 2

 

Plates:

Anaerobic blood agar plate showing predominately two colony types
Anaerobic blood agar plate showing predominately two colony types

 

Isolate of organism 1 on anaerobic blood agar showing dry, white colonies.
Isolate of organism 1 on anaerobic blood agar showing dry, white colonies.
Isolate of organism 2 on anaerobic blood agar showing small, white colonies with no hemolysis
Isolate of organism 2 on anaerobic blood agar showing small, white colonies with no hemolysis

Discussion:

Two organisms were identified.

Organism 1: Fusobacterium nucleatum – anaerobic gram-negative, non-spore-forming rods. They are pale-staining, long, slender, spindle-shaped rods with sharply pointed or tapered ends; occasionally the cells occur in pairs end to end. Sometimes there are spherical swellings. Cells are usually 5-10 µm long, but can be shorter. They grow well on anaerobic blood agar plates under anaerobic conditions and are killed readily by exposure to ambient air. Colonies on anaerobic blood agar are 1-2 mm in diameter, slightly convex with slightly irregular margins and have a characteristic internal flecking referred to as “crystalline internal structures”. They can have three morphologies: bread crumblike (white), speckled, or smooth (gray to gray-white). There is greening of the agar on exposure to air, they are usually nonhemolytic and fluoresce chartreuse under UV light.

The Fusobacterium species are normally found in the upper respiratory, gastrointestinal, and genitourinary tracts of humans. They are common causes of serious infections in multiple body sites. They are associated with infections of the mouth, bite wounds, and respiratory tract. F. nucleatum are the most frequently involved in anaerobic pleuropulmonary infections (aspiration pneumonia, lung abscess, necrotizing pneumonia, thoracic empyema). They are also fairly common pathogens in brain abscesses, chronic sinusitis, metastatic osteomyelitis, septic arthritis, liver abscess, and other intraabdominal infections. Fusobacterium nucleatum is the species most commonly found in clinical materials. It can cause severe systemic infection in patients with neutropenia and mucositis following chemotherapy.

They can be differentiated from similar species of Bacterioides, Prevotella, Porphyromanas, and Leptotrichia by their production of butyric acid but not isobutyric or isovaleric acid. Bacterioides and Porphyromanas species produce all three acids.

Organism 2: Parvomonas micra – formerly called Peptostreptococcus micros or Micromonas micros, are anaerobic, gram-positive cocci, <0.7 µm in diameter; occur in packets and short chains. Grow on anaerobic blood agar. Colonies are tiny, white, opaque, nonhemolytic. This is a periodontal pathogen that contributes to periodontitis.

 

Kirsten J. Threlkeld, MD is a 4th year anatomic and clinical pathology resident at the University of Vermont Medical Center.

Wojewoda-small

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Assistant Professor at the University of Vermont.

 

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