Anaerobiospirillum succiniciproducens bacteremia in a young child

We report a case of Anaerobiospirillum succiniciproducens bacteremia in a young child who had no underlying disease. The case should alert microbiologists and physicians to an uncommon organism that is very often resistant to antibiotics normally prescribed empirically for infections caused by organisms of similar morphology and characteristics such as Campylobacter species. Anaerobiospirillum succiniciproducens is a spiral, motile Gram-negative anaerobic rod. It is part of normal intestinal flora of cats and dogs, and it has occasionally caused diarrheal disease in humans. 1 McNeil et al. 2 summarized 22 case reports of bacteremia, and subsequently 4 additional reports of bacteremia, totaling 26 patients, have appeared in the literature. 3–6 Of the 28 reported patients 27 (96%) had underlying diseases or conditions. We report a case of A. succiniciproducens bacteremia in an otherwise healthy infant. Case report. An 11-month-old female infant was seen in the emergency department with a 2-day history of fever (39°C], irritability, vomiting and loss of appetite. Other than having thalassemia minor the child was healthy, with unremarkable prenatal and postnatal history. In the emergency department the child had a fever of 38.4°C but appeared well. She was hemodynamically stable, with a heart rate of 160 and oxygen saturation of 93%. Physical examination was unremarkable except for very mild hepatosplenomegaly, inflamed pharynx and bilateral otitis media. Laboratory data were as follows: leukocytes 23.5 × 106/ml with 48% neutrophils, hemoglobin 8.7 g/dl, mean corpuscular volume 57 fl, normal serum biochemistry and erythrocyte sedimentation rate of 30 mm/h. Routine urinalysis was normal as was the chest radiogram. Urine and blood cultures were drawn. The child was discharged with a diagnosis of upper respiratory tract infection and bilateral otitis media, and a 10-day course of amoxicillin was prescribed. Three days later two anaerobic bottles from two blood culture sets were positive in our BACTEC 9240 system (Becton Dickinson, Sparks, MD), growing Gram-negative spiral rods that were subsequently identified by the API rapid ID 32 A kit (bioMérieux, Marcy l’Étoile, France) as A. succiniciproducens. Antibiotic susceptibility testing showed the organism to be susceptible to amoxicillin/clavulanic acid and chloramphenicol, intermediately susceptible to amoxicillin and resistant to penicillin, erythromycin, clindamycin and metronidazole. On follow-up the child had a complete and uneventful recovery; follow-up blood cultures were not done. Discussion. A. succiniciproducens is a rare cause of human infection. The organism appears to be part of the normal intestinal flora of dogs and cats but not of asymptomatic humans. 6 The organism has been associated with diarrheal disease in humans, possibly reflecting a zoonosis transmitted by contact with dogs or cats. 1 The manifestation of bacteremia appears to be almost exclusive to patients with underlying disease such as alcoholism, malignancy or diabetes, and all reported cases were adults. 2–6 Despite the high frequency of gastrointestinal symptoms observed in patients with A. succiniciproducens bacteremia, nausea, vomiting and bleeding are more common than diarrhea. 2 The possibility exists that A. succiniciproducens bacteremia is more common than thought, but the organism has mistakenly been identified as Campylobacter spp. because of similar Gram stain morphologic characteristics. Differentiation from Campylobacter spp. is very important from epidemiologic and treatment perspectives. Unlike Campylobacter spp., A. succiniciproducens is usually resistant to erythromycin, as in our patient. In addition it is most important to identify A. succiniciproducens, in that it is often resistant to many antibiotics normally prescribed for anaerobic infections, such as clindamycin and metronidazole. Our patient was a child without underlying disease, in contrast to all other reported patients, all of whom were adults and most of whom had some underlying disease. The lack of underlying disease might explain why our patient made an uneventful recovery despite not having received optimal antibiotic therapy. Although a clinical diagnosis of upper respiratory tract infection and otitis media was made, the possibility that the organism was simply a contaminant is unlikely because it grew from two separate blood culture sets. Coincidental respiratory tract infection and A. succiniciproducens bacteremia of unknown origin cannot be ruled out. The source of infection in our patient was not determined, and the patient had no known contact with dogs and cats.