Chryseobacterium spp. (formerly known as Flavobacterium) is an emerging Gram-negative microbe belonging to the CDC group IIb. It has been isolated earlier from various environmental samples like soil as well as from hospital surfaces.^1,2 Although the clinical significance of this organism is still under research, it has been reported from cases of septicemia, pneumonia, pyelonephritis, peritonitis, pyomyositis, meningitis, cellulitis, wound sepsis, etc.^3-6 The most commonly isolated species from clinical specimens are C. indologenes, and C. meningosepticum. Four more species namely C. multivorum, C. gleum, C. breve, and C. odoratum have also been implicated to cause clinical infections.⁷ Among all of these species, C. meningosepticum, also known as Elizabethkingia meningoseptica, is considered to be the most pathogenic species.^8,9

Being a ubiquitous organism, Chryseobacterium sustain well on the environmental surfaces and also may be resistant to chlorination used for water supplies.⁸ It finds its way to colonize hospitalized patients via both invasive (prosthetic valves and intravascular catheters) and non-invasive (humidifiers, respirators, endotracheal tubes, etc.) medical devices and equipment as well as hands of the healthcare personnel.^8,10,11 The predisposing factors are diabetes mellitus, immuno-compromised state including neutropenia, malignancy, and prolonged use of antibiotics like colistin, and tigecycline.^12-15

C. indologenes in particular is intrinsically resistant to multiple antibiotics viz. aminopenicillins, first generation cephalosporins, aztreonam, and aminoglycosides.³ The resistance rates against other antibiotics like cefepime, imipenem, meropenem, piperacillin-tazobactam, fluoroquinolones were also found to be extremely high (≥70%) in different studies.^16-17 Besides, the multi-drug resistance trait, its inextricable virulent nature posed by the biofilm forming ability and production of protease enzyme made it a formidable pathogen in the clinical set up.^18,19 Furthermore, the laboratory confirmation of the bacterium remains a challenge owing to its fastidious nature and inability to grow on routinely used culture medium like MacConkey agar.^20,21

Since the beginning of the 21^st century, the application of automated systems with some cutting edge technologies has revolutionized the microbial detection of pathogens in Microbiology laboratories. Relatively unknown microbes are being identified more frequently which were earlier overlooked or missed. This privilege has brought the opportunity of further research and assessment on the spectrum of infection and pathogenicity of rarely reported bacterial isolates like C. indologenes. Albeit, the reports on this particular bacterial infection among cancer patients, specially from India, are still very limited in the literature.^22,23 The occurrence of infection with C. indologenes among cancer patients are primarily attributed to the immunosuppression caused due to administration of chemotherapeutic agents, prolonged hospitalization and requirement for indwelling devices, and invasive procedures.¹⁴ The putative oncogenic potential of the bacterium has also been suggested in a micro-array based genetic assessment in ovarian cancer patients. In the study by Banerjee et al., it was listed among the top four bacterial signatures with the highest hybridization signal detected in the ovarian cancer patients.²⁴ Here, in this report we present a case of bacteremia with Chryseobacterium indologenes in a patient with B-cell Non-Hodgkin Lymphoma (NHL).

Case Report

A 32-year-old Indian male of lower-middle socio-economic class from an urban area in the national capital region of Delhi was referred to our hospital outpatient department from a private clinic. He presented with painless lumps under the skin in the bilateral axilla and on the sides of the neck for three weeks. The swelling was insidious in onset and gradually progressed in size. He also complained of diffuse abdominal swelling of the abdomen, multiple episodes of vomiting (4-5 times per day), and low-grade fever. There was a history of easy fatigability but no loss of appetite and loss of body weight. There was no history of cough, chest pain, shortness of breath, and night sweats. The patient neither suffered any similar complaints in the past nor had a history of diabetes, hypertension, tuberculosis, or any other chronic diseases. He was a non-smoker and non-alcoholic. There was no family history of malignancy.

The patient’s vitals were stable. On general examination, he had icterus and generalized lymphadenopathy. There were enlarged lymph nodes in the cervical region at level II, III, IV, V (largest at level III on the right side; 3 x 2 cm), axillary regions (16 x14 cm on the right side and 20 x 12 cm on the left side) with tenderness and skin discoloration noted on the right side, and inguinal regions (2 x 1 cm on the right side and 1 x 1 cm on the left side). Palpation of the abdomen revealed enlarged liver, tender, and firm in consistency, palpable up to 4 cm below the right costal margin. Findings of other systemic examinations were unremarkable.

A decision was made to admit the patient for detailed diagnostic workup and management.

His initial blood investigation at admission revealed decreased haemoglobin (11.1 g/dL), red blood cell count (3.9 X 10 6 / mm 3 ), platelet count (25 x 10 3 / mm 3 ) and increased white blood cell count (17.3 X 10 3 / mm 3 ), bilirubin (9.1 mg/dL), SGPT (282 U/L), SGOT (1112 U/L), alkaline phosphatase (651 U/L), serum urea (85.6 mg/dL), uric acid (16.9 mg/dL), and lactate dehydrogenase (8273 U/L) values. The patient was seronegative for HIV 1&2 Ab, HBsAg, and anti-HCV Ab. Prothrombin time was markedly increased (18.8 seconds). Contrast-enhanced CT (CECT) scan of neck, thorax, abdomen, and pelvic region revealed generalized lymphadenopathy, hepatosplenomegaly, and multiple lung nodules suggestive of lymphoma. Peripheral smear examination of the bone-marrow showed erythroid hyperplasia and megaloblastic change (M: E= 1:1) with thrombocytopenia, dimorphic anemia, and 5% atypical cells. Finally, bone marrow biopsy examination with immune-histochemistry confirmed the diagnosis of B-cell non-Hodgkin lymphoma (NHL), immune-positive for CD20.

He was started on injection cyclophosphamide, steroids (pre-phase) along with supportive care for tumor lysis syndrome and liver dysfunction. During this course of inpatient management, the patient remained afebrile and his vitals were stable. He initially responded to cytoreductive pre-phase with improvement in liver dysfunction. However, on the 12^th day of admission, the patient developed a fever of 102.2°F. His WBC count was reduced to 6.62 X 10³/ mm³ from the initial count. Multiple blood samples were received consequently, for culture and susceptibility testing on two separate occasions (2 bottles on each occasion with a gap of 2 days). He was started on injection cefoperazone-sulbactam empirically. However, the therapy was escalated to meropenem and teicoplanin when the patient continued to deteriorate. The blood cultures were processed on an automated blood culture system (BACTEC, Becton Dickinson, USA). All samples flashed positive within 10 hours. The Gram stain made from the positive bottles showed Gram-negative bacilli. The samples were subcultured on Blood and MacConkey agar as per the laboratory protocols. After 24 hours of incubation at 37°C, the blood agar grew 0.5-1 mm, non-hemolytic, yellow-colored moist colonies with smooth surface and entire edges (Figure 1). The MacConkey agar grew non-lactose fermenting colonies (Figure 1). They were oxidase and catalase positive. The colonies were further processed for identification and susceptibility testing on the automated system (Phoenix M50, Becton Dickinson, USA). All four blood samples were identified as Chryseobacterium indologenes which were resistant to ampicillin, amoxicillin-clavulanate, cefixime, ceftriaxone, ceftazidime, cefepime, cefoperazone-sulbactam, piperacillin-tazobactam, colistin, gentamicin, amikacin, and susceptible to levofloxacin and cotrimoxazole. The minimum inhibitory concentrations (MIC) values of different antibiotics against the isolate have been mentioned in Table. A subculture was also made to nutrient agar to check for the flexirubin pigment. The yellow colonies on nutrient agar turned red (Figure 2) on the addition of 10% potassium hydroxide (KOH) solution.⁶ Injection levofloxacin was started, and the patient became afebrile. Subsequent two blood cultures yielded no growth. However, despite the intense effort in management, the patient’s liver dysfunction and DIC worsened. The patient succumbed on the 26^th day of admission due to refractory status epilepticus with massive pulmonary bleeding and recurrent ventricular fibrillation resulting from subacute liver failure.

Table:
Minimum inhibitory concentrations of different antibiotics and their susceptibility profile against the Chryseobacterium indologenes isolate.

*Breakpoints for this emerging pathogen is not yet available. Hence, the breakpoints of Pseudomonas aeruginosa has been used for interpretation of the susceptibility against different antibiotics.³⁰