Hospital-acquired pneumonia due to Leclercia adecarboxylata in a neurosurgical centreMR Prakash1, R Ravikumar1, N Patra1, B Indiradevi2
1 Department of Neuromicrobiology, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
2 Department of Neurosurgery, National Institute of Mental Health and Neurosciences (NIMHANS), Bangalore, Karnataka, India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0022-3859.153108
Source of Support: None, Conflict of Interest: None
Leclercia adecarboxylata , a gram-negative bacillus of the Enterobacteriaceae family, is an uncommonly identified human pathogen. The organism has been reported worldwide and isolated from various environmental sources. Most human infections are polymicrobial and commonly occur in immunocompromised hosts, although nosocomial infections in immunocompetent hosts have been documented. We describe three case reports of L. adecarboxylata isolation from cases of hospital acquired pneumonia admitted to a tertiary care center for neurosurgical care.
Keywords: Emerging pathogen, enterobacteriaceae, Leclercia adecarboxylata, nosocomial infection, polymicrobial infection
Leclercia adecarboxylata , an ubiquitous gram-negative bacillus of the Enterobacteriaceae family, has been rarely isolated from environmental and clinical specimens. 
L. adecarboxylata shares characteristics of Enterobacteriaceae; they are Gram-negative, facultatively-anaerobic, oxidase-negative, mesophilic, peritrichate-flagellated bacilli. 
In clinical specimens, L. adecarboxylata has been commonly isolated from polymicrobial wound infections. , The majority of infections are seen in immunocompromised patients but there are reports of L. adecarboxylata infections in immunocompetent patients. ,, We present in this paper 3 patients infected with this bacillus one of whom succumbed.
A 41-year-old otherwise healthy male presented to casualty with severe head injury following a road traffic accident. Vital signs on admission were unremarkable but on physical examination, decorticate posturing was noted. While his chest x-ray was normal, Computed tomography (CT) scan of head without contrast revealed right fronto-temporo-parietal acute subdural hemorrhage. The patient was intubated, resuscitated and underwent right craniotomy and evacuation. On the third post-operative day he developed fever and tachypnea. Leukocyte count was 20,000/μl. A clinical diagnosis of ventilator-associated pneumonia (VAP) was made. Tracheal aspirate microscopy showed copious polymorphonuclear leukocytes with gram-negative bacilli. Culture revealed pure growth of large grey non-hemolytic colonies on blood agar and pale non-lactose-fermenting colonies on MacConkey agar after 24 hours of incubation. The strain was motile, produced indole, fermented mannitol and did not produce hydrogen sulfide and oxidase. Blood and urine culture demonstrated no bacterial growth. The organism was identified as Leclercia adecarboxylata by Vitek 2 system (bioMιrieux, Marcy-lͲEtoile, France) and was found to be resistant to ampicillin (MIC ≥ 32 μg/ml) but sensitive to amoxicillin-clavulanic acid (MIC ≤ 2 μg/ml), ciprofloxacin (MIC ≤ 0.25 μg/ml), cotrimoxazole (MIC ≤ 20 μg/ml), amikacin (MIC ≤ 2 μg/ml), gentamicin (MIC ≤ 1 μg/ml), piperacillin-tazobactum (MIC ≤ 4 μg/ml), ceftriaxone (MIC ≤ 1 μg/ml), cefuroxime (MIC ≤ 8 μg/ml), cefepime (MIC ≤ 1 μg/ml), cefoperazone-sulbactum (MIC≤ 8 μg/ml), tigecycline (MIC ≤ 0.5 μg/ml), meropenem (MIC ≤ 0.25 μg/ml) and imipenem (MIC ≤ 0.25 μg/ml). The patient received amikacin 80 mg intravenous daily. Repeat tracheal aspirate sent a week later demonstrated no growth. The patient improved clinically and was discharged after two weeks.
A 32-year-old otherwise healthy female patient presented to casualty with history of headache, vomiting and loss of consciousness. Vital signs on admission were notable for a blood pressure of 170/80 mm Hg but were otherwise unremarkable. Computed tomography angiography revealed anterior communicating artery aneurysm with sub-arachnoid hemorrhage. Seven weeks into her hospital stay after multiple surgical procedures and prolonged ventilation, she developed fever of 102 ° F and her leukocyte count was 12,300/μl. Chest x-ray showed few pulmonary infiltrates. Tracheal aspirate sent during this febrile episode revealed polymorphonuclear leukocytes and few gram-negative bacilli. Culture yielded pure growth of L. adecarboxylata identified by Vitek 2 system and sensitive to ampicillin (MIC ≤ 1 μg/ml), amoxicillin-clavulanic acid (MIC ≤ 0.5 μg/ml), ciprofloxacin (MIC ≤ 0.5 μg/ml), cotrimoxazole (MIC ≤ 20 μg/ml), amikacin (MIC ≤ 2 μg/ml), gentamicin (MIC ≤ 1 μg/ml), piperacillin-tazobactum (MIC ≤ 1 μg/ml), ceftriaxone (MIC ≤ 1 μg/ml), cefuroxime (MIC ≤ 2 μg/ml), cefepime (MIC ≤ 1 μg/ml), cefoperazone-sulbactum (MIC ≤ 2 μg/ml), tigecycline (MIC ≤ 0.25 μg/ml), meropenem (MIC ≤ 0.5 μg/ml) and imipenem (MIC ≤ 0.5 μg/ml). Blood and urine culture demonstrated no growth. The patient received imipenem 1 g intravenous every 6 hourly and amikacin 80 mg intravenous daily for 1 week. Repeat tracheal aspirate did not show growth of this organism. She became afebrile and her leukocyte count reduced to 8300/ μl.
A 32-year-old male presented to the out-patient department with history of upper back pain for 1 month and lower limb weakness for 6 days. The patient was HIV positive and was receiving anti-retrovirals efavirinez and zidovudine. His CD4 cell count on admission was 180 cells/μl. Vital signs were notable for a pulse rate of 110/min. Physical examination was unremarkable. Magnetic resonance imaging revealed multiple vertebral body signal changes with complete destruction of the C6 vertebral body and a paravertebral collection. With the provisional diagnosis of vertebral tuberculosis, he underwent laminectomy and C6-C7 decompression. On the fifth post-operative day, he developed fever of 101 ° F. Leukocyte count was 9200/μl. Chest X-ray showed right lobar consolidation. Tracheal culture demonstrated polymorphonuclear leukocytes and gram-negative bacilli and yielded pure growth of L. adecarboxylata, identified by Vitek 2 system. It was found to be sensitive to ampicillin (MIC ≤ 2 μg/ml), amoxicillin-clavulanic acid (MIC ≤ 1 μg/ml), ciprofloxacin (MIC ≤ 0.5 μg/ml), cotrimoxazole (MIC ≤ 20 μg/ml), amikacin (MIC ≤ 1 μg/ml), gentamicin (MIC ≤ 1 μg/ml), piperacillin-tazobactum (MIC ≤ 2 μg/ml), ceftriaxone (MIC ≤ 2 μg/ml), cefuroxime (MIC ≤ 2 μg/ml), cefepime (MIC ≤ 1 μg/ml), cefoperazone-sulbactum (MIC <= 2 μg/ml), tigecycline (MIC ≤ 0.5 μg/ml), meropenem (MIC ≤ 0.25 μg/ml) and imipenem (MIC ≤ 0.5 μg/ml). Histopathology of a vertebral lesion biopsy demonstated non-Hodgkin's lymphoma. He expired about a week later due to respiratory insufficiency. Follow-up cultures were not obtained in this patient.
L. adecarboxylata is a member of the Enterobacteriaceae family, the members of which are regarded as normal flora in the gut of animals.  The case series presented includes both immunocompetent and immunocompromised hosts. As per the definition by Centre for disease control and prevention (CDC), pneumonia contracted by a patient in a hospital about 48-72 hours after admission is considered as nosocomial pneumonia. All the three cases discussed above fulfill the criteria. The patients had been mechanically ventilated and the organisms were isolated from samples collected several days after admission, suggesting that these were nosocomial infections.
The presence of polymorphonuclear leukocytes in the gram stain of the aspirate along with the pure growth of the isolate in culture and associated leukocytosis may help to some extent in indicating the clinical significance of this organism that was isolated in the above three cases. The isolates reported here demonstrated sensitivity to most antibiotics; repeat cultures in patients #1 and #2 did not grow the organism. No investigation for the source of this organism in the hospital was performed. However, the hospital infection control team was notified and the hospital staff was instructed about hospital infection control measures. Although nucleic acid analyses like 16S rRNA sequencing are considered gold-standard methods for bacterial identification, we could not perform molecular tests as they were not available in our facility.
L. adecarboxylata is more commonly associated with polymicrobial infection. , However, in the three cases mentioned above, L adecarboxylata was recovered in pure culture without any co-existing pathogen. Similar findings were reported by Hess et al., wherein L. adecarboxylata was isolated from a wound infection as a single pathogen in an immunocompetent patient. 
L. adecarboxylata has been rarely isolated from cases of pneumonia. In a study done by Temesgen et al., L. adecarboxylata was isolated from sputum in a patient with pneumonia due to multiple bacteria. Another case of pneumonia due to multi-drug resistant L. adecarboxylata was described by Eiland et al. In our case series, we have described cases of pneumonia due to a single pathogen which was found to be sensitive to most of the antibiotics tested.
Forrester et al. have described isolation of L. adecarboxylata from blood and central venous catheter of a trauma patient.  Two of the three cases described by us are from trauma cases.
Due to significant morbidity and mortality associated with nosocomial infections, microbiologists and clinicians should be aware of unusual pathogens like L. adecarboxylata. Though most L. adecarboxylata isolates are sensitive to many of the antibiotics, their co-existence with multi-drug resistant organisms could result in the transmission of resistance elements. In view of prolonged hospital stay in one of the three cases, transfer of drug resistance is a matter of great concern. Vigilance for the development of resistance in L. adecarboxylata is essential.