Abstract
To the Editor:
P
A 77-year-old diabetic male was admitted to our hospital because of cholelithiasis. His medical history included hypertension. An open cholecystectomy was performed, and the patient had an uncomplicated post-operative course. Three weeks later, he complained of anorexia, upper-abdominal discomfort, and vomiting. Laboratory tests revealed a white blood cell count of 19,500/mm3. The abdominal computed tomography (CT) scan showed two heterogeneous hypoechoic images suggesting intraperitoneal abscesses. The first was located in the upper abdomen, between the left lobe of the liver and the stomach, and measuring 13.1 × 10.3 × 16 cm, whereas the second was a subhepatic abscess measuring 8.6 × 4.2 cm. Two blood cultures yielded no pathogens, and magnetic resonance cholangiopancreatography did not reveal abnormalities in the biliary tree.
The patient underwent CT-guided percutaneous drainage of the abscesses. The purulent material was white yellow, with no bile content. In the microbiology laboratory, the growth of a gram-negative bacillus from the abscess fluid was detected in BACTEC Peds Plus F broth (Becton Dickinson, Meylan, France). After 24 h, lactose-fermenting colonies were obtained, which were identified as P. agglomerans by Phoenix 100, an automated microbiology system (BD Medical Supplies, Franklin Lakes, NJ). Identification was confirmed by conventional microbiological methods (citrate −, urease −, TSI Alk/A hydrogen sulfide −, indole −, Voges-Proskauer +, motility +, yellow pigment +, oxidase −, catalase +). Antimicrobial susceptibility testing showed the isolate was sensitive to ciprofloxacin (minimum inhibitory concentration [MIC] ≤1 mcg/mL), ceftriaxone (MIC ≤2 mcg/mL), levofloxacin (MIC ≤4 mcg/mL), and meropenam (MIC 8 mcg/mL) and resistant to ceftazidime, aztreonam, and imipenam (MIC >16 mcg/mL). The patient received ciprofloxacin (400 mg/day in two doses), had an uneventful recovery, and was discharged two weeks after his admission. He received a further 10-day course of oral ciprofloxacin (500 mg/day in two doses), and ultrasonographic resolution of both abscesses was observed at three months.
Currently, seven Pantoea species are distinguished: P. agglomerans, P. ananatis, P. stewartii, P. dispersa, P. citrea, P. punctata, and P. terrea [3]. The biochemical heterogeneity of P. agglomerans and related strains makes species identification difficult. Phylogenetic relations among Pantoea species were based initially on 16S rRNA analysis and sequencing of the three protein-coding genes atpD, carA, and recA [4]. Both methods showed that P. agglomerans, P. ananatis, and P. stewartii are closely related.
The approach to defining bacterial species uses both genomic and phenotypic characteristics. Multi-locus sequence analysis (MLSA) can define species and explore sequence discontinuities [5]. Pantoea agglomerans strains can be differentiated using fluorescent-amplified fragment-length polymorphism or pulsed-field gel electrophoresis [5]. Multi-locus sequence typing (MLST) consists of sequencing internal portions of several protein-coding genes. It is now a widely accepted method for studying strain relations [5].
This is our first human case of intra-abdominal infection caused by P. agglomerans, which was the only pathogen isolated from cultures of the purulent drainage material. This raised the suspicion of thorn injury, and the patient was asked to recollect any prior such injury. He denied a thorn injury, declaring that he never was an agricultural worker and never had farmland or even a garden. He reported that he had some symptoms of gastroenteritis ten days before admission. Although the hypothesis is not well documented, we think it possible that the preceding gastrointestinal insult facilitated bacterial translocation across the gut mucosa, leading to abscess formation.