Pharyngeal and peritonsillar abscess due to Leclercia adecarboxylata in an immunocompetant patient

Leclercia adecarboxylata was isolated in pure culture from a peritonsillar and lateral pharyngeal abscess in an immunocompetent host. To our knowledge, this is the first case of infection caused by this microorganism being found in an odontogenic area of the head and neck.


Case report
A 32-year-old otherwise healthy male patient reported to the department with a chief complaint of unilateral neck pain, along with difficulty in swallowing, breathing and talking for two days.He had no history suggestive of a medically compromised state.There was a positive history of tobacco chewing for 15 years; however, there was no history of other health-compromising personal habits such as smoking or betel leaf chewing (with or without areca nut and slaked lime paste).No history of immunosuppressive therapy or previous antibiotics or steroid use was present.He was febrile for the past two days and his vitals at the time of admission were as follows: temperature38.5 o C, respiratory rate 21/minute, blood pressure 120/84, and pulse rate 89/minute.The patient's liver function tests, renal function tests, random blood sugar, HIV test and complete blood counts showed no abnormality except that he had neutrophillic leucocytosis (TLC 8900 and neutrophils 79%).
On extraoral examination, facial asymmetry was evident, the left angle region of the mandible was tender, and the left submandibular lymph nodes were palpable, enlarged, tender, discreet and non-fixed.Swelling of 2 x 3 cm in size, extending on an angle from the mandible 2 cm anteriorly and 3 cm inferiorly was noted (Figure 1).The swelling was soft, tender and compressible, and the overlying skin temperature was raised.On intra-oral examination, swelling was present in the left lateral pharyngeal region, 4 x 3 cm in size, soft, compressible, fluctuant, and tender, and the overlying mucosa was inflamed.The patient displayed poor oral hygiene and his mandibular left third molar was associated with pericoronitis and purulent discharge.A diagnosis of left peritonsillar and left lateral pharyngeal space abscess was made.
Based on examination of vital signs, the patient was diagnosed with severe inflammatory response syndrome (SIRS) likely to progress towards sepsis.Immediate Ringer's Lactate infusion was started and surgical intervention was planned.The mandibular left third molar was identified as the focus of infection and it was extracted under local anaesthesia with sedation.An 18-gauge needle was inserted in the swelling intraorally; a pus sample was aspirated and transferred to a sterile Hiculture collecting device for aerobic culture and a Hiculture transport swab with Amies medium with charcoal (all from HiMedia Laboratories Private Limited, Mumbai, India) was taken for anaerobic culture.The pus sample was sent for culture sensitivity testing.An intraoral incision in the lateral pharyngeal wall was performed and the infection was drained.A corrugated rubber drain was placed and stabilized with sutures (Figure 2).
The patient was started with empirical antibiotic therapy as follows: amoxicillin-clavulanic acid 1.2 gm three times daily and metronidazole 500 mg three times daily intravenously for three days followed by oral doses of the same antibiotics for another three days.The causative organism in the pus was found to be Leclercia Adecarboxylata.No other micro-  organism, aerobic or anaerobic, could be isolated.On culture and sensitivity testing, the pathogen was obtained in pure culture.Antibiotic sensitivity was checked using the Vitek system (Vitek 2 System and Test Cards, bioMérieux SA, Marcy l'Etoile, France).The pathogen was found to be sensitive to the following antibiotics: amoxicillin-clavulanic acid, imipenem, colistin, tigecycline, tetracycline, meropenem, cotrimoxazole, ciprofloxacin, amikacin, gentamycin ceftriaxone, ceftazidime, cefepime, ciprofloxacin (MIC ≤ 0.25) and levofloxacin (MIC ≤ 0.12).The patient recovered uneventfully.

Discussion
L. adecarboxylata was first described by Leclerc in 1962 as Escherichia adecarboxylata [1].It is an aerobic, motile, Gram-negative bacillus of the Enterobacteriaceae family.Lysine decarboxylase, malonate assimilation and acid production from arabitol and cellobiose, but not from adonitol and sorbitol, allows definitive separation of L. adecarboxylata from Escherichia coli.It is universal in distribution, found in a variety of foods, water, and animals (snails and slugs), and commensal in the gut.Only a few instances of pathogenicity have been reported so far, thus emphasizing its nature as an opportunistic agent.In clinical specimens, it has been found primarily as one of the components of polymicrobial infections, which suggests the dependence of this micro-organism on co-flora to cause a disease.Pure cultures have been isolated almost exclusively in immunocompromised patients with only one such culture reported in an immunocompetent individual [1].It has been shown to be sensitive to most of the antimicrobial agents, although resistance to ceftazidime, cefotaxime, aztreonam, and cefepime [2] has been noted in one study.The table shows the reported cases depicting the immune status of the host, along with the site of isolation of the pathogen and of the co-infection status in each case.We would like to emphasize that this pathogen has so far not been reported in scientific literature from any head and neck space infection, infections in the latter being usually being caused by Staphylococci, Streptococci, Bacteroides, Fusobacterium, Porphyromonas and Prevotella species.In the current case, L. adecarboxylata was identified as the lone pathogen causing a peritonsillar and lateral pharyngeal abscess in a nonimmunocompromised host.Thus the significance of this case report lies in the fact that this is an infrequent pathogen gaining entry into the head and neck fascial spaces.It is also suggestive of advancements in the isolation and culturing techniques that have led to accurate identification and segregation of L. adecarboxylata from E. coli.

Figure 1 .Figure 2 .
Figure 1.Left lateral view showing deep neck space involvement

Table 1 .
Summary of studies relating to Leclercia adecarboxylata S. No.