Bacteremia Caused by Pantoea Agglomerans and Enterococcus Faecalis in a Patient with Colon Cancer

CASE REPORT

Bacteremia caused by Pantoea agglomerans and Enterococcus faecalis in a patient with colon cancer

G.B. Christakis1, S.P. Perlorentzou1, M. Aslanidou1, L. Savva2, I.K. Zarkadis3 1Department of Microbiology and 2Department of Medical Oncology-B, Metaxa Cancer Hospital, Piraeus; 3Department of Biology, School of Medicine, University of Patras, Rion, Patras, Greece

Summary identiﬁ ed as P. agglomerans by 16S rRNA gene sequencing. A case of bacteremia caused by Pantoea agglomerans (P. agglomerans) and Enterococcus faecalis in a male patient Key words: colon cancer, DNA sequencing, meropenem, with colon cancer is reported. He was successfully treated Pantoea agglomerans, polymicrobial bacteremia, 16S with vancomycin and meropenem. The clinical isolate was rRNA

Introduction implicated in a nosocomial outbreak of bacteremia associated with contaminated parenteral nutrition [7], P. agglomerans (formerly named Enterobacter whereas the organism is also associated with outbreaks agglomerans) is a Gram-negative organism of the of pseudobacteremia due to contaminated intravenous Enterobacteriaceae family. It can be found in human solutions, stored blood products and blood collection and animal faeces, and in plants. Human infections tubes [6,8]. Here, we describe a case of bacteremia caused by P. agglomerans more often involve bones caused by P. agglomerans and Enterococcus faecalis and joints and occur mainly after plant thorn injuries in a patient with colon cancer. [1,2]. In addition, clinical isolates have been recovered from blood and chronic ambulatory peritoneal dialysis fl uid [3,4]. Case presentation P. agglomerans is not as frequent a cause of en- dogenous nosocomial infection as Enterobacter spe- A 72-year-old man suffering from colon cancer cies. This probably refl ects the greater intrinsic sus- was admitted in October 2005 to our hospital because ceptibility of P. agglomerans than other Enterobacter of mild hemorrhage from sigmoidostomy. In June species to β-lactams antibiotics [5] and the opportu- 2004 he had undergone sigmoidectomy followed by nity for infection rather than the intrinsic virulence of adjuvant chemotherapy. Between the two hospital the organism involved [6]. P. agglomerans has been visits, prostate cancer had been diagnosed and treated with androgen blockage, while colon cancer had re- lapsed locally and had been re-operated twice. First- and second-line chemotherapy was given and contin- Received 25-10-2006; Accepted 2-12-2006 ued until last presentation. On admission, blood pres- Author and address for correspondence: sure was 100/60 mmHg. Laboratory results showed hemoglobin 12.3 g/dl, leukocytes 10 × 109 /l with 70% George B. Christakis, MD 9 106 Ipsilantou Street neutrophils and platelet count 360 × 10 /l. 187 58 Keratsini On day 5, while in an unstable condition, the pa- Greece tient developed rigors and a temperature of 40º C. No Tel: +30 210 4315443 Fax: +30 210 8909566 source of infection was clinically apparent. Laboratory 9 E-mail: [email protected] data was notable for a leukocyte count of 13 × 10 /l 288 with 80% neutrophils, hemoglobin 9.0 g/dl, activated (http://www.ncbi.nlm.nih.gov/BLAST/). Genetic partial thromboplastin time (APTT) 46.1 sec (normal analysis confi rmed that the isolate belonged to the range, 26.0-38.0) and international normalized ratio genus Pantoea, as it shared 95-99.5% identity in the (INR) 1.5 (normal range 0.8-1.2). Chest X-ray as well 16S rRNA sequences with P. agglomerans and 86- as CT scan of the brain, chest and abdomen showed no 95% identity with other Enterobacter strains. Regard- signs of infection. Urine, stool and sputum cultures ing the species level, the isolate showed the highest were negative. Two sets of blood cultures, which had identity score with the strains: E. agglomerans strain been taken from a peripheral vein on day 5 while no A40 (GenBank AF130912) and E. agglomerans A38 central venous catheter or other prosthetic material (GenBank AF130911), exhibiting 10 and 21 bases dif- were in place, yielded a Gram-negative rod and a ference, respectively. Multiple alignment of 16S rRNA Gram-positive coccus later identifi ed as P. agglomer- gene sequences was performed with the CLUSTAL W ans and E. faecalis, respectively. Because of the un- program [12] and phylogenetic trees were constructed stable condition the patient was treated with merope- with the neighbor-joining, minimum evolution and nem (6 g daily) and vancomycin (1.5 g daily) for 7 parsimony analyses using the MEGA version 3 soft- days, and recovered completely from his infection. ware [13]. The isolate clustered with P. agglomerans There was no evidence of relapse until day 30 when species is shown in Figure 1. the patient died because of heart failure. Antibiotic sensitivity was tested on Mueller– Environmental samples, e.g., sinks, showerhead, Hinton agar by the Kirby-Bauer disc diffusion method, taps, detergents, and disinfectants, from the patient’s and zone diameters were interpreted according to medical ward were collected and cultured as described Clinical Laboratory Standard Institute guidelines [14]. previously [9]. All environmental samples failed to Quality control was performed by testing American yield this organism. Finally, investigation revealed Type Culture Collection (ATCC) strains Escherichia strict adherence to well-established guidelines for coli 25922, E. coli 35218 and Staphylococcus aureus blood collection and blood culture processing [10]. 25923. The P. agglomerans strain was sensitive to aminoglycosides, quinolones, chloramphenicol, trim- ethoprim-sulfamethoxazole and β-lactams except Microbiological investigation ampicillin, while the E. faecalis strain was susceptible to vancomycin, teicoplanin and linezolid. Two sets of standard medium blood cultures in a total of 4 bottles were taken immediately after the onset of fever. Blood cultures were processed with the Discussion BacT/ALERT System (bioMerieux). The 4 bottles (2 aerobic and 2 anaerobic) were positive within 12 h of The clinical experience with P. agglomerans in- incubation for a yellow-pigmented, oxidase-negative, fection is relatively limited because of the recent es- fermentative Gram-negative bacterium identifi ed as tablishment of the genus [15] and the lack of confi dent Pantoea spp. (biotype 1007173; probability 95.1%) by identifi cation in most clinical laboratories [16]. Mem- the API 20E system (bioMerieux), and a Gram-posi- bers of the genus Enterobacter appear to confound tive coccus in pairs and chains identifi ed as E. faecalis commercial identifi cation systems more often than do by the same commercial system. other genera in the Enterobacteriaceae, because of the In order to identify the primary structure of 16S heterogenicity of several of the species. For example, rRNA gene, chromosomal DNA extraction, PCR am- 6 commonly employed systems failed to identify one plifi cation and sequencing of the 16S rRNA gene were or more of several species (E. cloacae, E. aerogenes, performed as described previously [11]. Amplifi cation E. sakazakii, and P. agglomerans) with ≥ 90% accu- of the 16S rRNA gene was carried out using the prim- racy a total of 14 times [17]. An additional reason is the ers PANTF1: 5΄-GCTCAGATTGAACGC TGGC G- very low incidence of P. agglomerans infections. A 3΄ and PANTR1: 5΄-CCCTACGGTTACCTTGT- total of 183 consecutive patients with Enterobacter TACG-3΄. The PCR product, 1,486 bp in size, was bacteremia were analyzed during the period of January subcloned in a pGEM-T plasmid vector (Promega) and 1998 through December 2002 at Seoul National Uni- sequenced by universal primers at least twice for both versity Hospital. P. agglomerans strains were isolated strands. The nucleotide sequence of the PCR product, only in 3 (1.6%) of the initial blood cultures [18]. which deposited in the EMBL bank (GenBank acces- We believe that P. agglomerans was one of the sion number AM234150), was compared with known causative organisms in the case described here for 16S rRNA gene sequences, using the BLAST software several reasons. First, the patient’s systemic symptoms 289

*Sequence obtained during this study; §Bar, 0.005 nucleotide changes per nucleotide position.

Figure 1. Dendrogram of the 16S rDNA sequences of the obtained clinical strain and related sequences. A rooted tree resulted from a neighbour-joining bootstrap analysis (100 replications) of 16S rRNA gene sequences from the clinical isolate and related species published in GenBank, with Aeromonas hydrophilia as an outgroup. were at their height on the day that the positive blood as no further instances of colonization or infection cultures were drawn. Second, it grew from both aero- with P. agglomerans occurred in the months shortly bic and anaerobic bottles and bacterial growth took 12 before or after the patient in question. Although P. ag- h, which is consistent with rapid-growth properties of glomerans was not isolated from stool we suggest that the organism [2]. In addition, positive blood cultures the damaged gastrointestinal tract was the portal of are signifi cantly more likely to be true positives if entry to the systemic circulation for both isolates. With obtained from patients with malignancies [19]. Third, the exception of the underlying illness, no other risk our patient made a complete recovery with treatment, factor was found. whereas E. faecalis was resistant to meropenem and P. In conclusion, this report adds one additional agglomerans resistant (intrinsically) to vancomycin. patient to the few published cases of P. agglomerans Finally, polymicrobial bacteremia due to Enterobacter infection since its new taxonomic status [15] and em- species is not an uncommon clinical fi nding [6] where- phasizes the necessity of a sequence-based typing 290 approach for the defi nite identifi cation of the organ- Sphingomonas paucimobilis-bacteremia associated with a ism. We also suggest that before beginning treatment multi-bacterial water-borne epidemic among neutropenic of a bacteremia by P. agglomerans, it is very important patients. J Hosp Infect 2002; 50: 196-201. 10. Dunne WM Jr, Nolte FS, Wilson ML. Cumitech 1B. 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