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A case of bacteremia by Achromobacter xylosoxidans in an immunocompromised host and review of literature

1 Department of Microbiology, Mahatma Gandhi University of Medical Science and Technology, Jaipur, Rajasthan, India
2 Department of General Medicine, Mahatma Gandhi University of Medical Science and Technology, Jaipur, Rajasthan, India
3 Department of Anesthesiology, Mahatma Gandhi University of Medical Science and Technology, Jaipur, Rajasthan, India

Date of Submission28-Sep-2022
Date of Acceptance03-Dec-2022
Date of Web Publication03-Feb-2023

Correspondence Address:
Mukesh Kumar Sarna,
72, New Raja Park, Ram Gali 8, Jaipur - 302 004, Rajasthan
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/amhs.amhs_222_22


Achromobacter xylosoxidans is an uncommon nosocomial pathogen known to cause serious infections in immunocompromised patients. Long stays in critical care units often predispose to infection with this bacterium. A female patient, who is a known case of diabetes mellitus type 2, hypertension, and chronic kidney disease, presented to the emergency department with complaints of shortness of breath, generalized swelling, decreased urine output for 7 days, and altered sensorium for 1 day. A. xylosoxidans was isolated from paired blood culture. She was managed according to the antibiotic susceptibility report and was improving when she left against medical advice due to personal issues. The objective of presenting this case report is to stress upon the importance of communication between the microbiologist and the clinician. Embracing automation in microbiology laboratories is essential to identify such novel bacterium in time to achieve clinical and microbiological cures.

Keywords: COVID-19, emerging pathogen, immunocompromised

How to cite this URL:
Rajni E, Kataria S, Sarna MK, Garg VK. A case of bacteremia by Achromobacter xylosoxidans in an immunocompromised host and review of literature. Arch Med Health Sci [Epub ahead of print] [cited 2023 Mar 29]. Available from: https://www.amhsjournal.org/preprintarticle.asp?id=369091

  Introduction Top

Achromobacter is nonfermentative, Gram-negative aerobic bacillus belonging to the order Burkholderiales. It is widely distributed in nature, especially in soil and aquatic environment. It has also been reported to be part of normal human flora, especially of the gastrointestinal tract and skin.[1] There are 16 species described, with Achromobacter xylosoxidans being the most common. Although described by Yabuuchi in 1971 from purulent ear discharge of patients with chronic otitis media, its growing clinical significance as an emerging opportunistic pathogen is being recognized only in the recent past.[2]

It is considered to be an organism of low virulence, most common clinical scenarios encountered being respiratory tract infections in patients with cystic fibrosis and bacteremia in immunocompromised patients. Other presentations include catheter-related infections (peritoneal dialysis and central venous catheter), meningitis, pneumonia, and endocarditis. The case fatality rates have been seen to vary from 3% to 80%.[3] Many outbreaks have also been described. The source of infection is either endogenous or from the contaminated aquatic hospital environment.

Several features exhibited by Achromobacter have rekindled interest in this hitherto lesser-known pathogen. In addition to the large genome, it has the ability to survive in disinfectants, thereby presenting a challenge for infection control personnel. Its transmission needs to be curtailed because it may serve as a reservoir for horizontal genetic transfer thus contributing to growing antimicrobial resistance.[4] Microbiologists need to be aware of the possibility of encountering these novel bugs particularly because organism-specific antibiotic breakpoints are not available for Achromobacter, thereby necessitating the use of nonEnterobacterales Clinical and Laboratory Standards Institute breakpoints for interpreting the susceptibility testing results.

Current data on this uncommon pathogen is limited to a few case series or single case reports. It is important to disseminate information when such bugs are encountered in clinical settings. The following case report will help in generating awareness among microbiologists and clinicians to make timely and accurate diagnoses.

  Case Report Top

A 69-year-old known diabetic and hypertensive female with chronic kidney disease (CKD) for 2 years presented to the emergency department with complaints of shortness of breath, generalized swelling, decreased urine output for 7 days, and altered sensorium for 1 day. She was on maintenance hemodialysis for the last 1 month. There was a history of hospital admissions and antibiotic intake twice in the last 1 year, details of which could not be found. The patient was shifted to the intensive care unit (ICU) and intubated in view of poor sensorium and severe dyspnea with metabolic acidosis. Her total leukocyte count (TLC) was 12,000/μl, Hb was 9.1 g/dl, and platelets were 1.27 × 106/μl. Her serum urea and creatinine were 151 mg/dl and 3.3 mg/dl, respectively. Blood and urine were sent for culture before initiation of antibiotic therapy as per hospital policy.

She was started on intravenous ceftriaxone 1 g 12 hourly, insulin infusion according to blood sugar levels, antihypertensives, and hemodialysis with other supportive treatment. All basic investigations were sent. COVID-19 reverse transcriptase–polymerase chain reaction was done due to ground-glass opacities on chest X-ray and was reported positive. Treatment for COVID-19 was started with intravenous remdesivir 200 mg in 100 ml normal saline once a day on day 1, followed by 100 mg once a day from day 2 to day 5, intravenous methylprednisolone 40 mg 8 hourly, subcutaneous enoxaparin 0.6 ml once a day, and budesonide nebulization with other supportive treatment. During the hospital stay, the patient developed right-sided hemiparesis which was investigated and treated as per protocol and the neurologist's opinion. She continued to be on mechanical ventilation with increasing oxygen requirement, the fraction of inspired oxygen requirement went up to 80%. She developed fever spikes and went into septic shock despite ongoing treatment. Her TLC rose to 18,000/μl, Hb was 11 g/dl, platelets were 1.53 × 106/μl, urea was 116 mg/dl, and creatinine was 4 mg/dl on day 5 of admission. Considering the deteriorating clinical condition, rising TLC, and persistence of fever, ceftriaxone was discontinued, and therapy was escalated to intravenous meropenem and polymyxin B.

The paired blood culture bottles beeped positive within 6 h of incubation. The organism was found to be motile, Gram-negative nonfermenter. It produced smooth, pinpoint, nonhemolytic colonies on blood agar after overnight incubation at 37°C. It grew well on MacConkey agar as lactose-nonfermenting colonies. This Gram-negative organism was both oxidase and catalase positive. Further identification and antimicrobial susceptibility testing were done using VITEK 2 Compact (Biomerieux system) and the organism was found to be A. xylosoxidans. The antibiotic susceptibility testing revealed it to be resistant to aztreonam, amikacin, gentamicin, and ciprofloxacin, while sensitive to ceftazidime, cefepime, imipenem, meropenem, cefoperazone/sulbactam, piperacillin/tazobactam, and intermediate sensitive (I) to colistin. The minimum inhibitory concentration data and interpretive reporting are presented in [Table 1]. Since the patient had started to respond to the therapeutic regime and show clinical improvement, the same antibiotics were continued. She was extubated on the 10th day and continued to get oxygen support through nasal prongs. On day 11, the patient left against medical advice due to personal reasons.
Table 1: Results of antimicrobial susceptibility testing of Achromobacter xylosoxidans isolated from patient's paired blood culture

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This was the first occasion we experienced this rare pathogen in our ICU. To rule out environmental sources for this novel bug in our setup, surveillance samples were taken from several aquatic surroundings in the hospital such as intravenous fluids, sterile saline, ventilators, humidifiers, irrigation, and dialysis solutions. However, none of these samples yielded positive results. Nevertheless, infection control measures and hand hygiene compliance were reinforced. No further infection has been reported from our setup after this case.

Informed consent was obtained from the patient for the publication of this case report.

  Discussion Top

The isolation of nonfermenter from blood culture is often a clinical dilemma. It can be tricky task to ascertain the clinical significance of such isolate. There are several reasons for encountering these bugs more frequently now than ever in past. With growing automation in microbiology laboratories, the large spectrum of nonfermenters is being recognized. It is quite possible that these organisms were being missed earlier by laboratories using largely conventional methods. The frequency of these isolates may have been underestimated because of likely confusion with other nonfermenters such as Pseudomonas aeruginosa, Burkholderia cepacia complex, and Stenotrophomonas maltophilia.[5] Pandey and Nautiyal have opined that with the development of automated methods and their full utilization, it is better to keep a close watch on emerging nosocomial pathogens.[5]

Furthermore, advances in transplantation and oncology sectors have produced a huge pool of vulnerable populations. Long stays in critical care units often predispose to infections with these bugs. The isolation from paired blood culture, in the paradigm of immunocompromised hosts with invasive devices and previous antibiotic exposure, along with raised markers of systemic inflammation are key points toward the isolate being clinically significant.

In the current case, an elderly patient with previously diagnosed CKD and diabetes mellitus type 2 became COVID-19 positive, and developed pneumonia and ultimately sepsis due to A. xylosoxidans. The patient had a history of multiple hospital admissions, repeated dialysis, and prior exposure to antibiotics, details of which could not be found. The immune status of the patient may have been compromised due to old age, CKD, diabetes, and steroids administered during the present COVID-19 infection. Immunocompromised status of the patient, the presence of an indwelling device (hemodialysis catheter), multiple exposures to antimicrobials in the past, and prolonged ICU stay are probable risk factors for the development of sepsis with this infrequently reported pathogen.

The two most common settings seen to be associated with Achromobacter infection are nosocomial infection in immunocompromised, presenting mostly as bacteremia and cystic fibrosis lung infection. Bloodstream infections produce a syndrome complex which is akin to that caused by another Gram-negative bacilli sepsis. Aisenberg et al. reported that the most common presenting features of Achromobacter bacteremia were fever (52%), sepsis syndrome (22%), and respiratory complaints (17%).[6] This is in consonance with presenting features of the patient in question. Other studies have also reported the most common manifestations as fever (82%), chills (37.5%), hypotension (32.5%), and altered consciousness. A brief summary of bloodstream infections caused by Achromobacter spp as previously described in the literature is presented in [Table 2].
Table 2: Overview of recent reports on Achromobacter xylosoxidans bacteremia cases

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Treatment of A. xylosoxidans infection can be an arduous task. The bacterium is known to exhibit several resistance mechanisms including efflux pumps, extended-spectrum beta-lactamases, AmpC-beta-lactamases, and metallo-beta-lactamases. These confer resistance to a wide spectrum of substrates and hence therapy for individual patients needs to be customized as per antibiotic susceptibility reports. Being frequently found resistant to aminoglycosides and the majority of beta-lactam antibiotics, a good clinical response has been documented with co-trimoxazole, antipseudomonal penicillins (ceftazidime and piperacillin/tazobactam), and carbapenems.[7] Appropriate source control is the absolute requirement, and this includes the removal of infected catheters. Biofilm forming ability of Achromobacter renders salvaging the catheter difficult. As described in the literature, the isolate in our case was found resistant to aminoglycosides. This phenomenon has been ascribed to be due to efflux pumps. It was found sensitive to piperacillin/tazobactam which has been reported to be most active against this bug. Several published reports are testimony to the complex antimicrobial susceptibility profile of Achromobacter [Table 2].

The most probable cause of hemiparesis in our case could have been the ongoing COVID-19 infection that predisposed the patient to arterial thrombotic complications such as ischemic stroke.

  Conclusion Top

The objective of presenting this case report is to create awareness about the role of this bacterium in causing nosocomial infections and also to stress upon the importance of communication between the microbiologist and the clinician. Embracing automation in microbiology laboratories is essential to identify these novel bugs in time to achieve clinical and microbiological cures. Early identification is also essential for infection control.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that her name and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Spear JB, Fuhrer J, Kirby BD. Achromobacter xylosoxidans (Alcaligenes xylosoxidans subsp. xylosoxidans) bacteremia associated with a well-water source: Case report and review of the literature. J Clin Microbiol 1988;26:598-9.  Back to cited text no. 1
Yabuuchi E. Twenty-seven years with the nomenclature of Achromobacter xylosoxidans. Rinsho Biseibutshu Jinsoku Shindan Kenkyukai Shi 1999;10:1-12.  Back to cited text no. 2
Duggan JM, Goldstein SJ, Chenoweth CE, Kauffman CA, Bradley SF. Achromobacter xylosoxidans bacteremia: Report of four cases and review of the literature. Clin Infect Dis 1996;23:569-76.  Back to cited text no. 3
Traglia GM, Almuzara M, Merkier AK, Adams C, Galanternik L, Vay C, et al. Achromobacter xylosoxidans: An emerging pathogen carrying different elements involved in horizontal genetic transfer. Curr Microbiol 2012;65:673-8.  Back to cited text no. 4
Pandey K, Nautiyal S. Achromobacter: An emerging nosocomial pathogen. Int J Res Med Sci 2019;7:3090-5.  Back to cited text no. 5
Aisenberg G, Rolston KV, Safdar A. Bacteremia caused by Achromobacter and Alcaligenes species in 46 patients with cancer (1989-2003). Cancer 2004;101:2134-40.  Back to cited text no. 6
Dai J, Huen AO, Kestenbaum LA, Sarezky MD, Coughlin CC, Yan AC. Achromobacter xylosoxidans bacteremia and cellulitis: A report of a case. Pediatr Dermatol 2015;32:e186-7.  Back to cited text no. 7
Houlihan E, Lucey M, Pandian A, Hanahoe B, Higgins F, DeLappe N, et al. Case of recurrent Achromobacter xylosoxidans bacteraemia and PICC (peripherally-inserted central catheter) line infection in an immunocompromised patient. Infect Prev Pract 2022;4:100202.  Back to cited text no. 8
Rodrigues CG, Rays J, Kanegae MY. Native-valve endocarditis caused by Achromobacter xylosoxidans: A case report and review of literature. Autops Case Rep 2017;7:50-5.  Back to cited text no. 9
Suresh R, Henry R. A rare instance of recurrent Achromobacter infection in an immunecompetent individual. Int J Contemp Med Res 2019;6:1135-6.  Back to cited text no. 10


  [Table 1], [Table 2]


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