A 68-Year-Old Man With Follicular Lymphoma Presenting With Fever and Chills - ANSWER

Figure 1. 

Anaerobiospirillum species Gram stain from blood agar plate incubated anaerobically showing Gram-negative, spiral-shaped bacteria (arrows). The organism grows as circular, translucent, nonhemolytic colonies up to 0.5 mm in diameter. They are motile by bipolar tufts of flagella. Useful biochemical markers include negative results for oxidase, catalase, indole, and nitrate reduction.

Diagnosis: Anaerobiospirillum species.

A preliminary diagnosis of Anaerobiospirillum species was made on the basis of the findings presented above, with definitive identification of Anaerobiospirillum succiniciproducens based on 16S ribosomal RNA (rRNA) sequencing. The patient was treated with a 14-day course of ertapenem with no growth on follow-up blood cultures. We believe his bacteremia was related to diverticular  disease in the setting of animal exposures. He continues to follow up with his oncologist for management of his follicular lymphoma.

Anaerobiospirillum species are Gram-negative, spiral-shaped anaerobic bacteria (Figure 1) that were first described by Davis et al in 1976. Despite their spiral shape, they are more closely related to the genus Aeromonas than to Treponema or Borrelia. They exhibit corkscrew-like motility and have bipolar multitrichous flagella and are part of the normal gastrointestinal flora of cats and dogs. Anaerobiospirillum species are a rare cause of bacteremia in humans; diarrheal illnesses have also been reported to be caused by A. succiniciproducens and Anaerobiospirillum thomasii.

The gastrointestinal tract is considered the usual route of entry. Patients typically present with gastrointestinal symptoms such as abdominal pain, nausea, and vomiting. Septicemia is mostly seen in patients with underlying medical conditions including alcoholism, malignancy (often gastrointestinal), diabetes, gingival disease, and atherosclerosis.

It is important to distinguish Anaerobiospirillum species from Campylobacter species, which have a similar Gram stain and colony morphology but are oxidase and catalase positive and grow in microaerophilic conditions. Although commercial biochemical tests may help, 16S rRNA sequencing is definitive. This is an uncommon infection, and optimal therapy has not been established. A. succiniciproducens is resistant to clindamycin and metronidazole, which are among the most commonly prescribed agents for anaerobic infections. A. succiniciproducens is reported to be susceptible to chloramphenicol, cephalosporins, fluoroquinolones, carbapenems, and penicillin/b-lactamase combinations.

Clinical Infectious Diseases 2012;54(1):148–9