A rare case of non-clostridial infection in a non-diabetic patient

Abstract

A 76-year-old man presented with neck swelling associated with pain and fever. On examination, there was a submental neck swelling. His initial CT scan showed multiloculated abscess centred in the left submandibular gland. He remained febrile despite on intravenous ceftriaxone and metronidazole. A repeat CT scan revealed significant worsening with multiple pockets of fluids with gas locules in the deep neck spaces. He subsequently underwent neck exploration and drainage of neck abscess. Extensive necrotic tissue was found intraoperatively and thick pus was drained from the bilateral parapharyngeal, submental spaces and anterior mediastium. Pus culture profusely grew of Eggerthella species. Patient recovered well following further intravenous antibiotic therapy. Diabetes mellitus and odontogenic infections are the common risk factors in deep neck infections. Our patient is however non-diabetic and edentulous. Current case is presented to serve as a rare case of neck abscess with unusual cause in a non-diabetic patient.

Background

This is an unusual case of non-clostridium gas forming neck abscess affecting a non-diabetic patient, caused by P revotella buccae and Eggerthella species.

Case presentation

A 76-year-old man presented with fever for 4 days duration. It was associated with neck pain and swelling which initially started over the left side of the jaw and later on progressed over the submental region. He was started on oral cephalexin but unfortunately he did not respond well to the treatment. He also developed dysphagia but no odynophagia. He has background of hypertension, osteoarthritis, rheumatoid arthritis and benign prostate hyperplasia. He is non- diabetic.

Clinically there was tenderness and slight fullness over the submental area. It was non-fluctuant and there were no signs of local infections. He was edentulous and the floor of mouth was edematous. Flexible nasolaryngoscopy examination showed mild supraglottic oedema. Both vocal cords were normal and mobile. He was febrile at 38°C but not toxic looking.

Investigations

His total white count (TWC) was raised at 21 and C-reactive protein (CRP) at 335. Fasting blood sugar was within normal limits. Ultrasound neck showed diffuse soft tissue swelling in the left submandibular and submental region but there was no focal collection amendable to aspiration.

He subsequently had a CT neck and chest with contrast (figure 1) which showed large multiloculated abscess centred in the left submandibular gland with local extension into the surrounding spaces of the suprahyoid neck, no extension into the chest. There was diffuse soft tissue swelling in the left submandibular and submental region

Figure 1.

Initial contrast-enhanced CT of neck. (A) Axial through upper neck shows a collection in the parapharyngeal and masticator space (black arrow). (B) Collection in relation to submandibular gland (black arrow). (C) Fluid and oedema in submental region (black arrow). (D) Coronal shows the extent on coronal plane. Black arrow shows collection in parapharyngeal/masticator space and broken arrow in relation to submandibular gland.

Differential diagnosis

The patient was diagnosed to have a neck abscess/necrotising fasciitis/gas gangrene and the differential was mainly about the causative organisms. Clostridium perfringens is the most frequently isolated in clinical settings. It is associated with high mortality risk 27%–44% at 30 days.¹ Patients associated with multiple comorbities are at risk to acquire this infection.²

Treatment

Patient was initially treated with antibiotics. No significant clinical improvement was noted despite being on intravenous ceftriaxone 2 g once daily and intravenous metronidazole 500 mg three times per day. He remained febrile but not septic looking. The neck swelling was enlarged and more fluctuant on day 5 of admission. CRP was 153 and TWC remained elevated at 22.3

Repeated CT (figure 2) showed multiple pockets of fluid with gas locules within the masticator spaces tracking inferiorly to the left supraclavicular region, anterior cervical region and anterior chest wall.

Figure 2.

Second contrast-enhanced CT of neck. (A) Axial. Increased amount of gas in the masticator space (white arrow). (B). Axial. Gas and fluid collections in bilateral submandibular spaces (arrows). (C). Axial. Gas, fluid and oedema in submental regions (white arrow). (D) Coronal. White arrows showing extensive gas in submental region. (E) Coronal. White arrows showing gas in left submandibular space and neck. (F) White arrow showing gas collection in upper chest.

He was consented for urgent exploration and drainage of neck abscess. Intraoperatively there were extensive necrotic tissues with pungent smelling discharge. Pus was drained from the submental, both submandibular and parapharyngeal spaces. Tracheostomy was performed at the same sitting to secure his airway. The neck wound was packed with large ribbon gauze soaked with betadine.

The next day, he underwent re-exploration of the neck wound under general anaesthesia. There was overall improvement in the neck wound cavity. The cavity was packed with similar dressing which was subsequently changed daily on the ward. He was monitored closely in the intensive care unit for 5 days before he was fit to be transferred to the ENT ward.

Outcome and follow-up

His CT neck and chest 3 days post surgery showed improvement in the gas and fluid collections (figure 3). Pus culture grew profuse P revotella buccae and Eggerthella species which were sensitive to co-amoxiclav, clindamycin, erythromycin, metronidazole, penicillin and tetracycline. His antibiotics were changed to flucloxacillin, benzylpenicillin, Clindamycin and gentamicin after discussion with the microbiologist. His neck wound was healing well and his tracheostomy was decannulated day 26 after the surgery. He was started on diet before discharge.

Figure 3.

Post operation contrast CT. White arrows showing residual gas in masticator space (A), submandibular spaces (B, C), submental region (D), around hyoid (E), suprasternal (F) and on coronal reconstruction (G,H).

Discussion

We present an interesting case of a non-clostridial infection of the neck. Necrotising fasciitis of the head and neck is rare. The incidence is 0.40 cases per 100 000.³ It is a life-threatening condition due to progressive infection involving the skin, subcutaneous tissue and fascia. Diabetes mellitus is a known comorbidity related to this condition. Airway compromise, mediastinitis, arterial and venous occlusion are known complications.⁴ CT is useful to detect air pockets which is important in diagnosing the condition and to look for the extent of the infection preoperatively. Urgent and aggressive management with broad spectrum antibiotics and surgical intervention is warranted to treat this extensive infection

The neck is made up of multiple layers of cervical fascia which encase the contents of the neck forming potential spaces of the head and neck. These fascial planes not only serve as important anatomic limitations for the spread of infections but also provide pathways of infection spread to adjacent sites once the natural resistance is overcome.⁵ Odontogenic infection is the most common aetiology of deep neck infections followed by upper respiratory infections, lymphadenitis, direct trauma or salivary gland infection.

Eggerthella is an anaerobic, non-sporulating, Gram-positive bacillus that belongs to Coriobacteriaceae family. It was first identified in 1935 by Arnold H. Eggerth, who isolated it from human faeces.⁶ The organism has undergone a variety of name changes (initially Bacteroides lentus and then Eubacterium lentum), subsequently, it was renamed as Eggerthella lenta in 1999.⁶ The spectrum of disease caused by this organism is not well described. It has been most commonly associated with intra-abdominal infections, which are often polymicrobial. The overall mortality appears to be significant, ranging from 36% to 43%.⁶ Prevotella buccae is also uncommonly involved with neck infections, mostly as a polymicrobial infection.⁷

Immunocompromised conditions such as diabetes increases the risk of deep neck infections and life-threatening infections. In this case, the likely infection is due to left submandibular sialdenitis as shown on the earlier CT scan. In addition to that, our patient is also edentulous and is non-diabetic. The extension of submandibular space infection may spread to paraphyrangeal and retropharyngeal space.⁸ Acute airway obstruction is the most frequent complications of deep neck infections followed by mediastinitis, Lemierre’s syndrome, internal jugular vein thrombophlebitis, carotid artery aneurysm and necrotising cervical fasciitis.⁵

Diabetic patients tend to have higher incidence and increased severity of infections than non-diabetic patients due to impaired host defense. Lower production of interleukins in diabetic patients results in reduction of chemotaxis and phagocytic activity and poor response to infection.⁸ Multispace infections of the neck is also associated with diabetic patient compared with non-diabetic.⁹ The organisms involved in non-clostridial gas gangrene can be due to a single organism or mixed infections due to Gram-negative rods, Gram-positive cocci and anaerobic bacteria.

Contrast-enhanced CT scan is the imaging study of choice for deep neck infections. It has the sensitivity ranging from 95% to 100% in identifying deep neck infections.¹⁰ It helps to distinguish cellulitis from deep neck infections. Location, extent of the infections and involvement of vascular structures are important features seen on the imaging.

Appropriate antibiotic therapy should be commenced immediately. Prompt and aggressive surgical drainage is the appropriate treatment for gas gangrene. A combination of surgical and antibiotic therapy is the standard modality of treatment.

We have presented a rare case of neck abscess/necrotising fasciitis/gas gangrene caused by uncommon non-clostridial bacteria with absence of usual predisposing causes like diabetes and dental infections.

Learning points.

• Gas gangrene of the neck can uncommonly affect non-diabetic. Serial clinical assessment and high index of suspicion is important in order not to miss this life-threatening condition.

• Early imaging or repeat scan is mandatory, if there is no significant clinical improvement despite appropriate medical treatment.

• Early surgical intervention is life-saving in the management of extensive head and neck infections.