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 Table of Contents  
Year : 2020  |  Volume : 7  |  Issue : 1  |  Page : 30-34

Acinetobacter infections: Overview and treatment dilemma

Department of Microbiology, Ayushman Hospital and Health Services, New Delhi, India

Date of Submission23-Mar-2019
Date of Decision01-Sep-2019
Date of Acceptance13-Jan-2020
Date of Web Publication19-Jun-2020

Correspondence Address:
Sana Ali
9A, Shiv Shakti Apartment, Plot-10, Sector-10, Dwarka, New Delhi - 110 075
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/cjhr.cjhr_30_19

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Introduction: Acinetobacter species are known to cause serious hospital-acquired infections (HAIs), especially in the intensive care unit (ICU). The aim of this study is to estimate the burden of such infections and also to determine their sensitivity to currently available antimicrobials. Materials and Methods: The study was conducted at a tertiary care hospital in New Delhi from June 2017 to December 2018 to estimate the number of Acinetobacter isolates from clinical samples. Organisms were identified, and their susceptibility to antimicrobials was tested using VITEK-2 automated system. Results: Of the total 701 isolates recovered from clinical samples during the study, 28 (4%) were Acinetobacter species. Among them, majority (57%) of the isolates were isolated from ICU patients. Respiratory specimen yielded maximum number of isolates (46.4%). About 71.4% of isolated strains were extremely drug resistant, 10.7% were multidrug resistant, whereas 3.5% were pandrug resistant (PDR). PDR strains were found to be resistant to even the last resort antibiotics such as tigecycline and colistin. Acinetobacter baumannii was also the most common cause for HAIs (57.1%), resulting in overall mortality of 42.8% due to HAI. Conclusion: Acinetobacter has gained great importance in health-care setting by posing serious threat to patients, which is compounded by its tendency of antibiotic resistance. HAIs are usually difficult to treat, resulting in therapeutic failure and increased mortality. It signifies the need to implement strict preventive measures in hospitals and to use higher antimicrobials or combination therapy judiciously.

Keywords: Acinetobacter, antibiotic resistance, hospital-acquired infection, intensive care unit

How to cite this article:
Ali S. Acinetobacter infections: Overview and treatment dilemma. CHRISMED J Health Res 2020;7:30-4

How to cite this URL:
Ali S. Acinetobacter infections: Overview and treatment dilemma. CHRISMED J Health Res [serial online] 2020 [cited 2021 Mar 3];7:30-4. Available from: https://www.cjhr.org/text.asp?2020/7/1/30/286886

  Introduction Top

Acinetobacter baumannii is a rapidly emerging pathogen in health-care institutions, leading to bloodstream infection, pulmonary infection, urinary tract infection, wound infection, and central nervous system infections.[1] It can survive under varying environmental conditions for long durations, thereby causing an outbreak as well as endemic infections. It is also well known for its role in the causation of hospital-acquired infections (HAIs).[2],[3]

A. baumannii started to spread rapidly among patients in intensive care units (ICUs) in the 1980s. The incidence of nosocomial infections by A. baumannii has been reported from 3.7% to 8.2% in Spain in 1992[4] and 9% in Europe as a whole in 1995.[5]A. baumannii complex contains isolates that are often resistant to multiple antibiotics and are often implicated in outbreaks of infection worldwide.[6]

Risk factors for colonization or infection include increased duration of hospital stay, ICU stay, and receipt of mechanical ventilation, administration of multiple antimicrobial agents, recent surgery, invasive procedures or devices and underlying the severity of illness.[2],[7] Infection caused by resistant strains have been reported among patients in rehabilitation centers, long-term care facilities, and in acute care hospitals.[8],[9]

Outbreaks of infection have been often linked to respiratory care equipment such as ventilators, humidifiers, and other patient care items. Increasing resistance is also observed owing to selective pressure from the reckless use of broad-spectrum antimicrobial therapy, especially carbapenems and third-generation cephalosporins.[1] The role of antimicrobial selective pressure, resulting in the emergence of resistance in Acinetobacter species has not been elucidated.

This study was done to determine the frequency of isolation and antibiotic resistance pattern of Acinetobacter spp. from clinical samples and its role in HAIs.

  Materials and Methods Top

This retrospective study was done from June 2017 to December 2018 in a hospital in New Delhi. The study included a total of 701 clinical samples that showed growth of bacterial isolates on routine culture in the microbiology laboratory. Respiratory tract samples (sputum, endotracheal secretion, and bronchoalveolar lavage), blood, urine, catheter tips, and pus were included in the study. Procedures followed were in accordance with the institutional ethical standards. Ethical clearance was not procured as it is a retrospective study and does not involve any patient for the sole purpose of research. All clinical samples were cultured on blood agar and MacConkey agar and incubated under aerobic conditions. Blood culture was done using BacT/ALERT (BioMerieux, India) automated system. All positive blood samples were subcultured on solid media (blood agar and MacConkey agar). Only first isolate from the patient was included, and subsequent isolates were excluded. Isolates were identified and tested for antibiotic resistance by VITEK-2 (BioMerieux, India) automated instrument.

Results were interpreted according to the Clinical and Laboratory Standards Institute guidelines.[10] Isolates were categorized into multidrug resistant (MDR), extremely drug resistant (XDR), and pandrug resistant (PDR) depending of resistance pattern observed. MDR was defined as acquired nonsusceptibility to at least one agent in three or more antimicrobial categories. XDR was defined as nonsusceptibility to at least one agent in all, but two or fewer antimicrobial categories (i.e., bacterial isolates remain susceptible to only one or two antimicrobial categories). PDR was defined as nonsusceptibility to all agents in all antimicrobial categories.[11]

  Results Top

Clinical samples received from June 2017 to December 2018 yielded a total of 701 bacterial isolates. Of these, 28 (4%) isolates were of Acinetobacter species. Twenty-seven isolates belonged to A. baumannii complex, while one was Acinetobacter lwoffii.

Majority of isolates were recovered from endotracheal secretion (32%) followed by blood (21%). [Table 1] shows the distribution of Acinetobacter species isolated from various clinical samples.
Table 1: Distribution of Acinetobacter species in clinical samples (n=28)

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Sixteen (57%) isolates were recovered from ICU patients, while 8 (28.5%) from wards and 4 (14%) from outpatients.

Susceptibility pattern was studied for all the isolates tested for commonly used antibiotics as shown in [Table 2]. Strains were categorized into MDR, XDR, and PDR according to the type of resistance observed [Table 3]. Majority of them were XDR (71.4%) followed by MDR (10.7%) and PDR (3.5%), while 14.2% were susceptible to most of the antibiotics tested and did not fall in any of these categories. Two (7.1%) strains were found to be colistin resistant. Both of them were isolated from the urine sample of ICU patients. A. lwoffii was sensitive to all the antibiotics tested.
Table 2: Susceptibility pattern of isolates (n=28) for different antibiotics tested

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Table 3: Type of resistance in different isolates

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A. baumannii was also responsible for 57.1% of the HAIs in the hospital, and overall mortality of 42.8% due to HAI. They were implicated in the causation of catheter-associated urinary tract infection, central line-associated bloodstream infection, and ventilator-associated event, as well as surgical site infection (14.2% each).

  Discussion Top

Acinetobacter species are the second-most frequent nonfermenting bacteria after Pseudomonas species recovered from patients, especially in association with HAIs.[12] They have emerged as a significant cause of nosocomial infections, especially in ICUs. It could be a result of increased invasive diagnostic procedures and devices, increased usage of broad-spectrum antimicrobials, and prolonged duration of hospital stay.

Increasing the incidence of infections by MDR bacteria has become a major concern in hospitals, as it increases mortality as well as morbidity in patients.[13]

Antimicrobial resistance is a crucial problem in the treatment of Acinetobacter infections, as they are known to acquire resistance rapidly.[14] In our study, Acinetobacter comprised 4% of the bacterial isolates from clinical samples, of which A. baumannii complex constituted 3.9%. Only one isolate of A. lwoffii was found. A. baumanni is the main species isolated in other studies as well.[15]

A maximum number of isolates were recovered from respiratory samples (46%), especially endotracheal secretion (32%). Other studies have also demonstrated respiratory tract (53%), to be a major source of Acinetobacter isolation.[16]

Acinetobacter species have shown markedly increased antimicrobial resistance in the past decade.[17] Strains that are resistant to all antimicrobial agents, including polymyxins, have been reported in the literature, leading to a significant challenge in the treatment of such infections.[18],[19] About 71.4% of isolates in our study were XDR, and 3.5% were PDR that were resistant even to colistin and tigecycline. Dash et al.[15] reported that 54.7% of the Acinetobacter isolates were MDR, and among them, eight isolates were PDR in their study. Majority of the isolates were sensitive to colistin (89.3%), followed by tigecycline (57.1%).

Mostofi et al.[20] have reported Acinetobacter species isolates to be least resistant to tobramycin (26%) followed by meropenem (31%) and piperacillin/tazobactam (40%), but highly resistant to imipenem (76%).

The study conducted by Taneja et al.[21] also reported the occurrence of PDR in 3.5% of their isolates, which were resistant to tigecycline and colistin as well. Various authors have reported a resistance rate to colistin between 1.8% and 2%[22],[23] and resistance to tigecycline between 0% and 66%.[24]

Uma Karthika et al.[25] showed that most of the Acinetobacter isolates showed complete or high resistance to imipenem (100%), meropenem (89%), amikacin (80%), cefotaxime (89%), and ciprofloxacin (72%).

Acinetobacter is widespread in the hospital setting. Its capacity to thrive for long periods along with the tendency for antimicrobial resistance has made it a successful hospital pathogen.[26] In health-care sector, it has resulted in 26% mortality rate and even higher in ICUs 43%.[27]

Acinetobacter (57.1%) was the major cause of HAI in the current study as well accounting for 42.8% of the mortality in HAI patients in ICU. In the study conducted by Kanafani et al.,[16] majority of infections in the study group were hospital acquired (84%) and predominantly consisted of respiratory infections (53.1%).

Since MDR Acinetobacter infection is more prevalent in critically ill patients admitted in the ICU, the associated crude mortality rate is high (26%–68%).[28],[29] Several studies have demonstrated that Acinetobacter independently does not lead to increased mortality.[30] It could be explained by the fact that Acinetobacter infection is a marker of increased death rate in patients with comorbid illness but not an independent predictor of mortality.

  Conclusion Top

It can be concluded from this study that Acinetobacter is an emerging cause of HAIs, especially in ICU and predominantly implicated in lower respiratory tract infections. Majority of the isolates were XDR suggesting reduced susceptibility to currently used antimicrobials, including higher ones. This has led to therapeutic dilemma where even higher antibiotics such as colistin and tigecycline do not work. It is the need of the hour to use antimicrobials judiciously and follow strict infection control measures to contain such infections.

Avoiding the urge to use higher antibiotics empirically and more stringent application of antibiotic policies in hospitals can curb the emergence of MDR strains in future.

The limitation of this study was that patients with Acinetobacter colonization were not included and more number of isolates need to be tested to determine the magnitude of problem with greater accuracy.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Table 1], [Table 2], [Table 3]


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