# Pneumonia due to a Rare Pathogen:Achromobacter xylosoxidans, Subspeciesdenitrificans

Authors: Hesham Awadh; Munthir Mansour; Obadah Aqtash; Yousef Shweihat
Journal: Case Reports in Infectious Diseases
 (2017)

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## Abstract

Achromobacter xylosoxidans, subspeciesdenitrificans, is a gram-negative rod recently implicated as an emerging cause of infection in both immunosuppressed and immunocompetent populations. Few cases are reported in literature involving multiple body systems. Diagnosis depends on cultures of appropriate specimens, and management usually is by administration of appropriate antibiotics (usually agents with antipseudomonal activity). We report a rare case of pneumonia due to infection with this organism, in a patient with preexisting bronchiectasis secondary to chronic aspiration.


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## Body

## 1. Introduction

Achromobacter xylosoxidans subspeciesdenitrificans is a gram-negative bacillus recently emerging as a causative agent of infection [1]. TheAchromobacterspecies has many subspecies the most clinically important of which arexylosoxidans anddenitrificans [1]. There are infrequent reports of infections with this organism involving various organs (Table 1). It seems that a dysfunctional immune status and/or prior structural damage plays a role in the pathogenicityAchromobacter xylosoxidans,subspeciesdenitrificans. We report a rare case of pneumonia due to this organism in a 45-year-old female with bronchiectasis secondary to recurrent aspiration.Table 1
Previous reports of infections withAchromobacter xylosoxidans subspecies denitrificans, detailing type of infection, antimicrobial sensitivity, and duration of treatment.
Year reported
Type of infection
Isolation specimen
Comorbid conditions
Sensitivity
Antibiotic of choice
Treatment duration
2011[6]
Prostheticvalve endocarditis
Blood
Tetralogy of Fallot
Cefepime, ceftazidime, ciprofloxacin, imipenem, levofloxacinPiperacillin/tazobactamTicarcillin/clavulanic acid, trimethoprim-sulfamethoxazole
Piperacillin/tazobactam(not specified), then imipenem
6 weeks of piperacillin/tazobactam, then 8 weeks of imipenem
2011[5]
Meningitis
Cerebrospinal fluid
ProstaticadenocarcinomaEpilepsyHyperlipidemiaAtrial fibrillationRemote history of cranial trauma
Not reported
Meropenem 2 gintravenously (IV)
15 days
2014 [9]
Peritoneal dialysiscatheter Exit site infection
Pus collected from exit site
Diabetes mellitus, chronic kidneydisease (near end stage renal disease)
Not reported
Ciprofloxacin 250 mg every twelve hours
14 days
2012[8]
Right renal abscess withrenocutaneous fistula
Pus collected from intrarenal abscess
Hypertension, chronic kidney disease, benignprostatic hyperplasiaRecurrent bilateral nephrolithiasis
Colistin, imipenem, meropenem,piperacillin/tazobactam
Meropenem 1 g IV
60 days
2013[7]
Prosthetic valveendocarditis with aortic root abscess
Blood
Congenital aortic stenosis, history ofaortic valve valvotomy
Not reported
Meropenem, trimethoprim-sulfamethoxazole,then levofloxacin
4 weeks
2014[4]
Pneumonia
Sputum
History of tuberculosis
Meropenem, imipenem, piperacillin/tazobactam,ticarcillin, trimethoprim-sulfamethoxazole, third-generation Cephalosporins
Meropenem 1 g q 8 hours
2 weeks
2014[9]
Peritoneal dialysisCatheter related peritonitis
Effluent dialysate
End stage renal disease on peritonealdialysis
Ciprofloxacin (other antibiotics not specified)
Ciprofloxacin(not specified)
Duration not specified
2017
Current case Pneumonia /Bronchiectasis
Bronchoalveolar lavage
Gastroesophageal reflux disease, asthma
Amikacin, cefepime, ceftazidime, gentamicin,levofloxacin, meropenem,piperacillin/tazobactam, tobramycin,trimethoprim/sulfamethoxazole
Levofloxacin
6 weeks


## 2. Case Presentation

This is a 45-year-old White female with past medical history of asthma and gastroesophageal reflux disease (GERD) treated with Nissen fundoplication in the past. She presented to our clinic with chronic cough productive of greenish sputum. She improved with previous antibiotic use of levofloxacin on several occasions but her symptoms would recur as soon as she stops the antibiotics. Chest X-ray at initial evaluation showed an infiltrate bilaterally more pronounced on the right lower lobe. A CT scan of the chest was obtained and confirmed the infiltrates and showed bronchiectatic changes bilaterally in the lower lobes (Figure1). Her autoimmune screen came back negative for rheumatoid arthritis and Sjogren’s syndromes, yet her immunoglobulins were elevated and her alpha one antitrypsin and immunoglobulin E (IgE) were at normal levels. Her sweat chloride test was normal. Chronic recurrent aspiration was suspected and an esophageal PH monitor along with esophageal manometry confirmed our suspicion of chronic aspiration secondary to severe acid reflux with elevated DeMeester score. Bronchoscopy was performed to rule out an obstructive disease and to obtain samples to rule out mycobacterial disease. Cultures came back positive for heavy growth of a nonfermenter later identified asAchromobacter xylosoxidans,subspeciesdenitrificans. Sensitivities were evaluated and the bacteria was sensitive to levofloxacin, amikacin, cefepime, ceftazidime, gentamicin, meropenem, piperacillin/tazobactam, tobramycin, and trimethoprim-sulfamethoxazole. It was found to be resistant to aztreonam, cefotaxime, and ciprofloxacin, with incubation period of 5 days. Airway clearance techniques with percussion and flutter valve and bronchodilator therapy with hypertonic saline nebulizers were initiated. She was started on a 3-week course of levofloxacin but her symptoms recurred one month after stopping the antibiotic despite airway clearance techniques. She was started again on levofloxacin for two more weeks with good clinical response and no recurrence of symptoms after a total 5 weeks of antibiotic therapy. She was referred for surgical intervention to abolish the ongoing injury to the airway and stop the aspiration insult to the airways.Figure 1
Infiltrates and bronchiectatic changes in lower lobes bilaterally.


## 3. Discussion

Achromobacter denitrificans is an aerobic, nonglucose fermenter gram-negative bacillus and flagellated and motile and produces acid from xylose [1]. The genusAchromobacterhas multiple subspecies:xylosoxidans, ruhlandii, piechaudii,denitrificans, spanius, insolitus, andmarplatensis. The most clinically significant subspecies areAchromobacter xylosoxidans anddenitrificans[2]. It can be found in nature in soil, and thexylosoxidans subspecies has an affinity for aquatic surfaces. There are more clinically significant isolates of the subspeciesxylosoxidans compared todenitrificans in terms of incidence of infection and clinical variety. Reports about infections withAchromobacter denitrificans are rare as an emerging pathogen.There is a multitude of respiratory system infection cases due toAchromobacter xylosoxidans, subspeciesxylosoxidans but notdenitrificans [3]. The first reported pneumonia case due toAchromobacter denitrificans was reported from India in a 48-year-old male clerk in a chemical factory. It was isolated from sputum at two different occasions with no other concomitant isolates. It was sensitive to meropenem, imipenem, piperacillin-tazobactam, ticarcillin, trimethoprim-sulfamethoxazole, and third-generation cephalosporins. It was successfully treated with two weeks of meropenem [4]. Our case is to date the second reported case ofAchromobacter xylosoxidans subspeciesdenitrificans. Other reported infections in adults include meningitis [5], endocarditis [6], endocarditis with aortic root abscess [7], renal abscess [8], peritoneal dialysis catheter related peritonitis [9], and exit site infection [10] (Table 1).Diagnosis depends on isolation of the organism depending on site of the infection. So far, we have reported isolates from septum, pus, peritoneal fluid, and cerebrospinal fluid (Table1). Identification can be via standard culturing methods. In our case bronchoalveolar lavage samples have been incubated in Blood Agar (TSA with 5% Sheep Blood)/MacConkey Agar Plate using a BioMérieux VITEK-2 system, incubated at 36-37 degrees Celsius.The immunosuppressed population are at higher risk of infection due toAchromobacter species [3], yet as seen in Table 1 most of the patients had not been overtly immunocompromised but may have had predisposing conditions (end stage renal disease, presence of catheters, etc.). Both cases with involvement of respiratory system had a background of bronchiectasis. The former [4] was most likely secondary to tuberculosis while in our case it is most likely secondary to recurrent aspiration. We theorize that the damaged bronchiectatic lung tissue predisposed to the infection with this organism. This had been illustrated before in thatAchromobacterspecies is known to colonize and infect cystic fibrosis patients [11]. In the other reported cases (Table 1), we can notice that structural damage and/or foreign body had been present: previous trauma, prosthetic valve, peritoneal dialysis catheter, and renal stones. Pathogenicity ofAchromobacter species has been previously studied [12] with demonstrated ability to form biofilms and motility (via pili and flagella) which can potentiate infections in setting of structural damage and devices.Management depends on administration of appropriate antibacterial agents, yet duration of treatment is not exactly defined due to lack in specific guidelines in this regard. The cases reported so far (Table1) had been managed with different regimens but the most palpable response was to carbapenems with durations ranging from 2 to 14 weeks (Table 1). The sensitivity of the isolates is outlined below in Table 1, but theAchromobacter species had been historically responsive to antipseudomonal agents [1] with various success rates depending on site of infection and complexity of the cases. Our patient was cured after 5 weeks of oral levofloxacin therapy (after initial failure after three weeks). The outcome is generally excellent with clearance of the infection.


## 4. Conclusion

Rare causes of pneumonia should be investigated since appropriate detection can facilitate accurate antibacterial management. We theorize that structural damage (bronchiectasis secondary to chronic aspiration) plays a role in the pathogenesis of pneumonia in our patient. Combined management with antibiotics and airway clearance techniques resulted in an excellent outcome.



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