An unusual case of polymicrobial anaerobic bacteraemia in a male with ureteral calculi

Received 26 February 2014 Accepted 16 June 2014 Department of Medicine, University Hospitals Case Medical Center, Cleveland, OH, USA Department of Medicine, Case Western Reserve University, Cleveland, OH, USA Department of Pathology, University Hospitals Case Medical Center, Cleveland, OH, USA Department of Pathology, Case Western Reserve University, Cleveland, OH, USA Clinical Microbiology, Pathology and Laboratory Medicine Services, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, USA Geriatric Research, Education and Clinical Center, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, US Infectious Diseases Section, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, OH, USA


Introduction
Part of the normal flora of the human oropharyngeal, gastrointestinal and genitourinary tracts, Fusobacterium spp.are anaerobic, Gram-negative bacilli that may cause a wide array of infections involving tissue necrosis and septicaemia (Bennett & Eley, 1993).Peptoniphilus asaccharolyticus (formerly Peptostreptococcus asaccharolyticus), also a common commensal bacterium of human mucosa, are anaerobic Gram-positive streptococci associated with abscesses, obstetrical infections and wounds (Brook, 1988).
We describe a case of polymicrobial bacteraemia caused by Fusobacterium gonidiaformans and P. asaccharolyticus probably due to disruption of the intestinal mucosal barrier during a routine colonoscopy with polypectomy.

Case report
A 65-year-old African-American man presented to our hospital with a 3-day history of severe left upper and lower abdominal pain, emesis, chills and intermittent left nostril epistaxis.Other symptoms included left mid-back pain and urinary frequency but no dysuria or haematuria.His medical history was notable for diabetes mellitus, hypertension, obstructive sleep apnoea and non-obstructing nephrolithiasis.He had had a routine colonoscopy 1 week prior to presentation with findings of diverticulosis; a single 2 mm sessile polyp was also removed from the ascending colon.
In the emergency room, the patient was febrile (38.6 u C) and tachycardic (113 min 21 ) with a blood pressure near his usual baseline (164/92 mmHg 21 ).Notable physical examination findings included clammy skin, moderate distress due to pain, a slightly distended abdomen with hypoactive bowel sounds and tenderness to palpation of the left upper and lower quadrants.He did not have suprapubic pain, costovertebral angle discomfort, rebound tenderness or guarding.Laboratory values included a white blood cell count of 25.5610 3 ml 21 with 91.8 % neutrophils, creatinine of 1.5 mg dl 21 , lactic acid of 3.3 mmol l 21 (normal range 0.5-2.2mmol l 21 ), a normal platelet count of 162 000 ml 21 and a normal international normalized ratio of 1.09.Liver transaminases were normal.His urinalysis showed positive nitrites, 59 white and 62 red blood cells per high-power field and 4+ bacteria.A computed tomography scan of the abdomen and pelvis revealed moderate left hydroureter and hydronephrosis in the setting of multipleureteral calculi (.5 stones, largest 7 mm), accompanied by periureteral and perinephric fat stranding.Following the collection of urine and blood cultures, the patient was started on vancomycin and aztreonam, the latter chosen because of the patient's history of anaphylactic reaction to b-lactams.
He was admitted to the medical intensive care unit and had a left-sided percutaneous nephrostomy tube placed by interventional radiology.He remained haemodynamically stable throughout the 6-day hospital course with resolution of his pain, fever, epistaxis and leukocytosis.Of note, while in the medical intensive care unit, his platelets decreased to 95 000 ml 21 with a concurrent increase in international normalized ratio to 1.43; these values returned to normal before discharge.
The urine culture obtained prior to antibiotics was negative, but blood cultures grew anaerobic Gram-positive cocci in clusters and Gram-negative bacilli less than 24 h after collection.The isolates were identified as P. asaccharolyticus and Fusobacterium species based on colony morphology and biochemical tests (Vitek-2 ANC anaerobe identification card; Biomerieux).A matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry system (Bruker Daltonics) confirmed the initial findings of P. asaccharolyticus and identified the Fusobacterium isolate as F. gonidiaformans.The F. gonidiaformans isolate was susceptible to penicillin, clindamycin and metronidazole.
The patient was discharged home to complete a 14-day course of therapy with metronidazole.Following an uneventful recovery, he received laser lithotripsy to remove the ureteral calculi.
Peptostreptococcus spp.are a more common cause of bacteraemia than Fusobacterium spp., with a recorded incidence of 0.9 per 100 000 of the population per year (Ngo et al., 2013).Many Peptostreptococcus spp., including P. asaccharolyticus, are part of the normal gut microbiome and are largely viewed as having low virulence (Minces et al., 2010).When found as a cause of disease, Peptostreptococcus spp.are usually part of polymicrobial infections, often detected in conjunction with Fusobacterium spp., as described above (Epaulard et al., 2006;Yang et al., 2011).They are also rare causes of infective endocarditis, often with high morbidity (Minces et al., 2010).
Beyond sepsis caused by a polymicrobial anaerobic bloodstream infection, this case has other unique features.First, clinically relevant bacteraemia following colonoscopies are exceedingly rare (Hartong et al., 1977;Kumar et al., 1982Kumar et al., , 1983;;Low et al., 1987).This remains true even with procedures that disrupt the mucosal barriers such as colorectal stent placement or endoscopic resection of colorectal tumours (Chun et al., 2012;Min et al., 2008).To our knowledge, this is the second description of sepsis due to anaerobic bacteraemia following routine colonoscopy with polypectomy; the first report described sepsis due to Clostridium perfringens (Kunz et al., 2009).Secondly, the patient presented with sepsis due to obstructive uropathy, probably caused by anaerobic organisms, as bacteria were noted on direct microscopy but aerobic culture did not yield any growth.We hypothesize that either transient bacteraemia during the colonoscopy or the procedure itself may have caused modest peritoneal inflammation that was sufficient to precipitate ureteral obstruction in this patient with ureteral calculi.Anaerobic organisms are rare causes of urinary tract infections (,0.1 %), but among patients with negative aerobic cultures and with persistent signs and symptoms of infection that localize to the genitourinary tract, anaerobic cultures may assist with diagnosis (Bannon et al., 1998).Thirdly, the patient presented with a 3-day history of epistaxis, moderate thrombocytopenia and a slightly elevated prothrombin time, all of which resolved with treatment of the underlying infection.These clinical features raise the possibility of a coagulopathy caused by the infection.Coagulopathy is a well-described feature of infection caused by F. necrophorum and may also be a feature of infection with F. nucleatum (Epaulard et al., 2006).Finally, our case underscores the utility of anaerobic blood cultures.With no a priori suspicion for anaerobic pathogens, the patient's urine was only cultured for aerobic organisms and was thus negative.Fortunately, the routine collection of blood for anaerobic culture led to pathogen identification and appropriate antimicrobial therapy for our patient's infection.