Achromobacter xylosoxidans in idiopathic cystic bronchiectasis

Abstract

This is the first case in the English language describing Achromobacter xylosoxidans in a patient with idiopathic bronchiectasis. A 66-year-old man with bronchiectasis presented with shortness of breath to the emergency department of our institution, a district hospital in the UK. His medications included long-term supplemental oxygen therapy and prophylactic azithromycin. Following 2 days admission to the respiratory unit, his saturations significantly deteriorated, and the patient was admitted to intensive care with type II respiratory failure. Following a week of intubation and ventilation, multidrug resistant A. xylosoxidans was isolated from the tracheal aspiration secretions. The patient recovered after receiving targeted intravenous antimicrobial therapy.

Background

This case highlights the importance of recognising several comorbidities in a patient with an atypical infection. In this case, the features contributing to environmental pathogen acquisition are suggested as idiopathic bronchiectasis and monoclonal gammopathy of uncertain significance.

Case presentation

A 66-year-old man presented with shortness of breath and productive cough to the emergency department of our institution, a district hospital in the UK. He had a long-standing diagnosis of bronchiectasis and was receiving long-term supplemental oxygen therapy at his home at 4 l min-1 for 15 hours per day. A retired painter and decorator, he had a medical history of monoclonal gammopathy of uncertain significance, which was under annual surveillance for conversion to multiple myeloma, and chronic bilateral otitis media and externa from childhood.

Swabs taken 5 years prior to admission, from the ear, due to chronic otorrhoea revealed colonisation with Achromobacter xylosoxidans. An arterial blood gas was obtained on admission, which showed a pH of 7.32, PaO₂ of 7.7 kPa, PaCO₂ of 10.0, consistent with mild type II respiratory failure. A chest X-ray on admission showed changes consistent with long-standing cystic bronchiectasis, with elements of opacification consistent with consolidation (figure 1). CT also demonstrated bronchiectasis with underlying consolidation (figure 2).

Figure 1.

Chest X-ray image of patient on admission.

Figure 2.

CT image demonstrating bilateral bronchiectasis and consolidation at T7.

Routine blood testing revealed raised inflammatory markers, with a C-reactive protein (CRP) of 150. Blood cultures were negative for bacteraemia. A working diagnosis of an infective exacerbation of bronchiectasis was made, and intravenous antibiotics initiated (co-amoxiclav and clarithromycin). He was transferred to the respiratory ward team for specialist care. Twenty-four hours after admission, he significantly deteriorated after poor toleration to non-invasive ventilation (NIV) and went into fulminant type II respiratory failure, which was recalcitrant to subsequent NIV therapy. An arterial blood gas analysis at this point was obtained due to his poor condition, which provided the following recordings: pH 7.22; PaCO₂ 13.57; PaO₂ 3.58; base excess of 8.0. Following discussion with the patient regarding the grave prognosis, a decision was made for transfer to intensive care for subsequent intubation and ventilation.

At this time, testing for pneumococcal antigen was positive from collected tracheal aspiration secretions samples. A tracheostomy was made 7 days after admission to the intensive care unit. During the stay on the intensive care unit, the patient underwent several episodes of unexplained desaturation. Further blood cultures, chest X-rays and routine blood tests were negative. On testing tracheal aspiration secretions samples obtained from lavage via suction from the tracheal tube, a rare atypical organism, A. xylosoxidans was cultured.

We suggest this organism contributed to worsening respiratory function and increased supplemental oxygen demands while on the intensive care unit, given the absence of this organism at intubation. Fibreoptic bronchoscopy for microbiological confirmation to differentiate this isolation from possible colonisation was not performed, but could have been considered. On sensitivity testing, the isolated organism was resistant to a number of antimicrobial agents (table 1). The antibiotic regimen was escalated with intravenous combination therapy piperacillin and tazobactam (Tazocin), and the patient recovered. Multiple repeat tracheal aspiration secretions samples taken at 6 and 8 weeks after final discharge revealed a mixed respiratory type flora from culture studies. Following a period of ward-based rehabilitation including pulmonary physiotherapy, the patient was successfully discharged with no further complications at 2 months follow-up.

Table 1.

Microbiological sensitivities of Achromobacter species isolated

Antibacterial agent	Presence of sensitivity
Amikacin	Resistant
Aztreonam	Resistant
Ciprofloxacin	Resistant
Chloramphenicol	Resistant
Colistin	Resistant
Co-trimoxazole	Sensitive
Gentamicin	Resistant
Meropenem	Intermediate
Piperacillin	Sensitive
Tazocin	Sensitive
Ticarcillin	Sensitive
Tetracycline	Resistant

Investigations

Investigations included chest X-ray (figure 1), CT of the thorax (figure 2), microbiological analysis of tracheal aspiration secretions, serial blood serum measurements of CRP and haematological analysis of white cells.

Differential diagnosis

The diagnosis was obtained through microbiological analysis of tracheal aspiration secretions and blood culture specimens.

Treatment

Treatment was with intravenous antimicrobial therapy targeted at the organism’s sensitivities (table 1). The mainstay of treatment included a 14-day course of Tazocin on the intensive care unit. In such patients, inhaled antibiotics might be considered, even in the presence of a tracheostomy.

Outcome and follow-up

At 6 months follow-up, the patient had fully recovered from infection with achromobacter. He was discharged from our care back into the community after 14 days of stepdown care from intensive therapy. In patients presenting with bronchiectasis and chronic otitis media, the possibility of primary ciliary dyskinesia (PCD) should be considered. These patients are at risk of acquiring chronic, pulmonary, Gram-negative infections like those contracted by cystic fibrosis patients. As the patient was over 60 years of age and not planning a family, nor had any family history of infertility, situs inversus or cell motility disorder, the patient was not tested for PCD.

Discussion

To our knowledge, this is the first full case report describing A. xylosoxidans infection in a patient with idiopathic bronchiectasis published in the English language. A comprehensive literature search was undertaken; we identified one case published in Spanish in 2009; and another case of non-cystic fibrosis bronchopneumonia we found was reported at the conference of the American Thoracic Society in 2014.^{1 2} A. xylosoxidans was described in 1971, following its isolation from otic discharge samples obtained from patients with chronic otitis media by Yambuuchi and Ohyama.³

Notably, our patient has suffered from recurrent otitis media from childhood to the present.

The organism has been described in patients with cystic fibrosis,^4–15 chronic obstructive pulmonary disease,¹⁶ rheumatoid arthritis,¹⁷ immunosuppression and HIV.¹⁸ A. xylosoxidans formerly known as Alcaligenes xylosoxidans, is a Gram-negative, peritrichous motile, non-spore-forming, conventional bacillus measuring 0.8×1.2–3.0 Gm.³ The bacterium is a strict aerobe and is non-fermenting.³ Achromobacter is characteristically of low virulence,^1–10 ubiquitously inhabits aquatic environments and is found in hospitals.⁸

A. xylosoxidans has been isolated from infections arising in the ear, eye, urinary tract, intra-abdominal infections, liver abscesses, soft tissue infections, osteomyelitis, arthroplasty prostheses, meningitis and endocarditis.^{1 3–10} The bacterium is also associated with indwelling medical devices.^{19 20} The most commonly described manifestation is bacteraemia and in the immunocompromised and neonates.¹⁶ Pulmonary cases of A. xylosoxidans infection may be attributable to a number of underlying comorbidities including IgM deficiency, haematological malignancies, chronic obstructive pulmonary disease and cystic fibrosis.^16–19 Other documented comorbidities include solid organ cancers, cardiac diseases and immunosuppression.^16–19

The prevalence of A. xylosoxidans is currently low in cystic fibrosis centres; however, colonisation rates are increasing.^5–10 Due to microscopic similarities with Pseudomonas species, there may be some underdiagnosis; however, this remain unquantified. There is a limited amount of data on the mode of acquisition of A. xylosoxidans, yet reports of intrahospital cross-infection are published in the cystic fibrosis population.²⁰

Case series of chronic carriers of A. xylosoxidans have failed to consistently correlate clinical deterioration with the organism.^1–5 The clinical outcomes of A. xylosoxidans infection in eight patients with cystic fibrosis was examined and, despite the requirement for increased doses of antibiotics, a decline in respiratory function was not demonstrated.² In another series, A. xylosoxidans was associated with a deterioration in pulmonary performance in the presence of rising specific antibodies in the serum.^{2 4 16} In the current case presentation, the isolation of A. xylosoxidans was concurrent with clinical deterioration, characterised by periods of unexplained desaturation on the intensive care unit, in the presence of monoclonal gammopathy of uncertain significance.

Importantly, A. xylosoxidans is multidrug resistant, refractory to all aminoglycosides and rifampin, with variable resistance to trimethoprim-sulfamethoxazole, and quinolones, such as ciprofloxacin.3–10 21 22 A. xylosoxidans is usually sensitive to carbapenems and penicillins.^16–19 There is no set treatment protocol for this Achromobacter and previous data in the literature suggest optimal antimicrobial compounds include minocycline, meropenem, piperacillin–tazobactam and chloramphenicol.^23–26 Our local microbiology service provided a list of sensitivities in the present case of A. xylosoxidans (table 1). In the present case, the patient was successfully treated with intravenous piperacillin–tazobactam (Tazocin); yet in instances of persistent organism culture, inhaled antibiotics are suggested.^3–6 Although Achromobacter infections are apparently rare, nosocomial acquisition appears to be increasing. Indeed, in such cases, repeated airway lavage or secretory cultures should be sought. In our patient, these were returned as negative; however in the presence of persistent organism culture, long-term inhaled antibiotics may have been required. Inhaled antibiotics are an ‘off-label’ therapy in non-cystic fibrosis respiratory infections, according to the US Food and Drug Administration and European Medicines Agency guidance.²⁷ Given the inherent resistance of the genus to antimicrobial therapy, timely identification and appropriate treatment are especially important in the management of patients with systemic comorbidities such as bronchiectasis and immunodeficiency.

Learning points.

• Achromobacter xylosoxidans infection in idiopathic bronchiectasis is newly described.

• In unexplained desaturation, atypical organisms should be considered in the differential diagnosis.

• A. xylosoxidans is resistant to several classes of antimicrobial compounds.