Acinetobacter baumannii: emergence and spread in Israeli hospitals 1997-2002

Identifying risk factors for carbapenem-resistant Acinetobacter baumannii carriage upon admission: a case-case control study

BACKGROUND

Active screening programs and early detection of asymptomatic carriers are effective in preventing carbapenem-resistant Acinetobacter baumannii (CRAB) dissemination in healthcare facilities. This study aims to identify risk factors associated with CRAB carriage among patients upon admission to an acute care hospital.

METHODS

A case-case-control study was conducted at an acute care hospital. Starting in June 2020, new admissions to medical wards underwent rectal and buccal screening. Patients with CRAB or carbapenem-susceptible A. baumannii (CSAB) carriage were compared to controls, randomly selected from patients with negative cultures, at a one-to-one ratio. Multinomial logistic regression using a backward stepwise method was employed to identify factors associated with CRAB and CSAB carriage. A Chi-square Automatic Interaction Detector analysis was also conducted to further elucidate risk factors.

RESULTS

The study included 115 CRAB carriers, 117 CSAB carriers and 121 controls. Increasing age was associated with a reduced risk of CSAB (OR: 0.96, p < 0.001) and CRAB carriage (OR: 0.97, p = 0.02), while higher Charlson Comorbidity Index scores increased the risk for both. CRAB carriage was significantly associated with admission from long-term acute care hospitals (OR: 7.68, p < 0.001) and presence of pressure ulcers (OR: 89.98, p < 0.001). Decision tree analysis identified pressure ulcers, prior location, and Charlson score as key predictors, with CRAB carriage reaching 77.3% in patients admitted from long-term acute care hospitals with pressure ulcers.

CONCLUSION

Pressure ulcers were strongly associated with the carriage of both susceptible and resistant strains of A. baumannii. CRAB carriage was predominantly observed in patients transferred from long-term acute care hospitals, highlighting the need for targeted screening in this high-risk population.

Mortality and genetic diversity of antibiotic-resistant bacteria associated with bloodstream infections: a systemic review and genomic analysis

BACKGROUND

Bloodstream infections (BSIs) caused by antibiotic-resistant bacteria (ARB) represent a significant disease burden worldwide. However, a comprehensive analysis of the mortality rates and global epidemiology across different ARB species associated with BSIs is currently lacking.

METHODS

We conducted a systematic review by searching multiple databases (PubMed, Web of Science, and Embase) for studies reporting ARB-related BSIs data up to June 19, 2023. Additionally, we performed genomic analyses of all the publicly available bacterial genomes associated with BSIs to elucidate their molecular characteristics.

RESULTS

A total of 322 articles (N = 90,672 patients) were included in this study. For 28 or 30-day mortality, the overall mortality rate for all ARB species was 32.0%. Among them, antibiotic-resistant A. baumannii exhibited the highest rate (54.2%). And the top three ARB types with the highest mortality rates at 28 or 30-day were CefeR-PA (cefepime-resistant P. aeruginosa), CREC (carbapenem-resistant E. coli), and CRAB (carbapenem-resistant A. baumannii), all exceeding 50%, whereas the mortality rates of CRKP (carbapenem-resistant K. pneumoniae), CRPA (carbapenem-resistant P. aeruginosa), and VREfm (vancomycin-resistant E. faecium) were at least 40%. A total of 9,289 ARB genomes related to BSIs were acquired from the NPDIB database and are predominantly distributed in North America, Asia, and Europe. Antibiotic resistance gene (ARG) analysis identified a total of 613 ARG subtypes from the top six ARB species, with numbers ranging from 48 for E. faecium to 253 for K. pneumoniae. Furthermore, specific clones of ARB species were strongly associated with BSIs, such as ST131 in E. coli, ST8, and ST5 in S. aureus, ST2 in A. baumannii, and ST11 and ST258 in K. pneumoniae.

CONCLUSION

ARB contributed to the burden of BSIs, with a 30-day all-cause mortality rate as high as 32.0%. ARB strains causing BSIs display high genetic diversity, highlighting the importance of continuing to monitor high-risk clones to control the development of antibiotic resistance. Differences in ARGs patterns require tailored antibiotic management strategies for each ARB species.

Isolation of a blaNDM-1-positive strain in Israel predating the earliest observations from India

blaNDM, the most prevalent carbapenemase among carbapenem-resistant Enterobacteriaceae, is thought to have emerged in India, as its initial detection in 2008 was linked to this country, and subsequent retrospective surveys had so far established the earliest blaNDM-positive strains to be isolated in India in 2005. Molecular dating and analyses suggest blaNDM emerged within Acinetobacter species decades prior to 2005 on a Tn125 transposon. Despite early reports of elevated rates of carbapenem-resistant Acinetobacter species in Israel starting in the 1990s, limited molecular data are available from this location. We searched for blaNDM among Acinetobacter species isolated in Israel between 2001 and 2006. One A. junii strain, Ajun-H1-3, isolated in January 2004, carried blaNDM-1 within a Tn125-like transposon on a 49-kb plasmid, pNDM-Ajun-H1-3, making Ajun-H1-3 the earliest NDM-positive isolate observed to date. The pNDM-Ajun-H1-3 plasmid matched numerous BJ01-like NDM-positive plasmids identified from 2005 onward in Acinetobacter species as well as Enterobacterales. These results indicate the need for further retrospective work on global strain archives to shed light on the conditions favoring the emergence as well as subsequent evolution and spread of blaNDM.

IMPORTANCE

This study presents the earliest observation of blaNDM-1, isolated in a geographical region distant from where it is believed to have originated. In doing so, this study provides novel insights into the emergence and spread of blaNDM, the most prevalent carbapenemase among carbapenem-resistant Enterobacteriaceae, and its associated mobile genetic elements. It also sheds light on the conditions that foster the evolution of antimicrobial resistance, one of the greatest public health challenges we face.

Tailoring Interventions for Control of Endemic Carbapenem-Resistant Acinetobacter baumannii: An Interrupted Time Series Analysis

Background

We examined temporal trends in carbapenem-resistant Acinetobacter baumannii (CRAB) infections in a hospital with hyperendemic CRAB and assessed the efficacy of varied infection control strategies in different ward types.

Methods

We retrospectively analyzed all CRAB clinical samples from 2006 to 2019 and categorized infections as hospital-onset (HO) or community-onset. We used interrupted time series analysis to assess the impact of interventions on the incidence of all HO-CRAB infections and bloodstream infections (BSIs) at the hospital and ward group levels.

Results

Over 14 years, 4009 CRAB infections were identified (89.7% HO), with 813 CRAB BSI (93.2% HO). The incidence per 100 000 patient-days of CRAB infections peaked in 2008 at 79.1, and that of CRAB BSI peaked in 2010 at 16.2. These rates decreased by two-thirds by 2019. In the general intensive care unit (ICU), hand hygiene and environmental cleaning interventions were followed by a significant reduction in the level of HO-CRAB infections, with an additional decrease in the slope after the introduction of active surveillance and 2% chlorhexidine bathing. In the surgical ICU and surgical department, a reduction in slope or level of CRAB infection was observed after moving ventilated patients to single rooms. In medical wards, a multimodal intervention was followed by a reduction in the slope of HO-CRAB infections and BSIs. In wards where CRAB infections were uncommon, the incidence of HO-CRAB infections decreased throughout the study period.

Conclusions

Ward-specific variables determine the success of interventions in reducing CRAB infections; therefore, interventions should be tailored to each setting.

Contribution of active surveillance cultures to the control of hospital-acquired carbapenem-resistant Acinetobacter baumannii in an endemic hospital setting

BACKGROUND

Despite the increasing rates of carbapenem-resistant Acinetobacter baumannii (CRAB) carriage among hospitalized patients in endemic settings, the role of active surveillance cultures and cohorting is still debated. We sought to determine the long-term effect of a multifaceted infection-control intervention on the incidence of CRAB in an endemic setting.

METHODS

A prospective, quasi-experimental study was performed at a 670-bed, acute-care hospital. The study consisted of 4 phases. In phase I, basic infection control measures were used. In phase II, CRAB carriers were cohorted in a single ward with dedicated nursing and enhanced environmental cleaning. In phase III large-scale screening in high-risk units was implemented. Phase IV comprised a 15-month follow-up period.

RESULTS

During the baseline period, the mean incidence rate (IDR) of CRAB was 44 per 100,000 patient days (95% CI, 37.7-54.1). No significant decrease was observed during phase II (IDR, 40.8 per 100,000 patient days; 95% CI, 30.0-56.7; P = .97). During phase III, despite high compliance with control measures, ongoing transmission in several wards was observed and the mean IDR was 53.9 per 100,000 patient days (95% CI, 40.5-72.2; P = .55). In phase IV, following the implementation of large-scale screening, a significant decrease in the mean IDR was observed (25.8 per 100,000 patient days; 95% CI, 19.9-33.5; P = .03). An overall reduction of CRAB rate was observed between phase I and phase IV (rate ratio, 0.6; 95% CI, 0.4-0.9; P < .001).

CONCLUSIONS

The comprehensive intervention that included intensified control measures with routine active screening cultures was effective in reducing the incidence of CRAB in an endemic hospital setting.

Wall painting following terminal cleaning with a chlorine solution as part of an intervention to control an outbreak of carbapenem-resistant Acinetobacter baumannii in a neurosurgical intensive care unit in Israel

BACKGROUND

To describe the use of wall painting as part of an intervention to control an outbreak of carbapenem-resistant Acinetobacter baumannii (CRAB).

METHODS

An interrupted time-series analysis was performed analyzing an intervention in a neurosurgical intensive care unit (NSICU) and an inpatient hematology department in a tertiary level medical center in Israel. The intervention involved wall painting using a water based acrylic paint following patient discharge and terminal cleaning with sodium troclosene as part of an infection control bundle for an outbreak of CRAB in a NSICU and concurrent outbreaks of carbapenem-resistant Enterobacteriaceae (CRE) colonization/infection in the same NSICU and the hematology department.

RESULTS

Between January 2013 and December 2018, 122 patients hospitalized in the NSICU were identified with new CRAB colonization/infection. The median incidence in the periods prior to/post intervention were 2.24/1000 HD (interquartile range [IQR] 0.84-2.90/1000) vs. 0/1000 HD (IQR 0-0.49/1000), respectively. Poisson regression indicated a decrease of 92% in the CRAB incidence following the intervention onset (relative risk [RR] 0.080, 95% confidence interval [CI] 0.037-0.174, p < 0.001). Forty-seven patients in the NSICU and 110 in the hematology department were colonized/infected with CRE in the same time period; a significant change was not observed following the start of the intervention in either department (for NSICU RR 1.236, 95% CI 0.370-4.125, p = 0.731; for hematology RR 0.658, 95% CI 0.314-1.378, p = 0.267).

CONCLUSIONS

A. baumannii is able to survive on environmental surfaces despite decontamination efforts; wall-painting as part of a bundle may be a successful infection control measure.

Evaluation of ceftriaxone-sulbactam-disodium edetate adjuvant combination against multi-drug resistant Gram-negative organisms

Background

Multi-drug resistant (MDR) Gram-negative bacteria are an emerging threat, both in hospital and community settings. As very few antibiotics are effective against such infections, the need of the hour is a new antibiotic or drug combination which can overcome the effect of extended-spectrum β-lactamases (ESBL) and metallo β-lactamases (MBL). A new antibiotic combination of ceftriaxone, sulbactam and disodium edetate (CSE) has recently been proposed to tackle the MDR organisms.

Objective

Our study was carried out to assess the susceptibility of ESBL- and MBL-producing Gram-negative organisms to CSE.

Methods

The study was conducted in a tertiary-care hospital in Delhi, India, from February 2017 to June 2017. A total of 179 MDR (85 ESBL + 94 MBL) Gram-negative isolates from various clinical samples, identified by an automated system (Vitek 2) were tested against CSE using the Kirby-Bauer disc diffusion method. Susceptibility to CSE was recorded based on interpretative zone sizes of ceftriaxone as per 2017 Clinical and Laboratory Standards Institute guidelines.

Results

The most common isolate was Escherichia coli (76/179; 42.4%) followed by Klebsiella pneumoniae (53/179; 29.6%) and Acinetobacter baumanii (27/179; 15.1%). The in vitro susceptibility of ESBL- and MBL-producing Gram-negative isolates to CSE was found to be 58/85 (68.2%) for ESBL and 37/94 (39.4%) for MBL.

Conclusion

The in vitro susceptibility results obtained for CSE against ESBL-producing organisms is promising. It has the potential to emerge as a carbapenem-sparing antibiotic, active against ESBL-producing strains. Further clinical studies are required to establish the clinical efficacy of CSE against MDR pathogens.

Acinetobacter baumannii infection in a medical intensive care unit: The impact of strict infection control

Background

Acinetobacter baumannii is a waterborne organism that preferentially colonises aquatic environments. Infections usually involve organ systems that have a high fluid content. Multidrug-resistant (MDR) A. baumannii is recognised to be among the most difficult antimicrobial-resistant Gram-negative bacilli to prevent and treat in the nosocomial setting.

Objectives

To determine the utility of concomitant implementation of a strict antimicrobial stewardship programme and comprehensive infection control measures to control MDR A. baumannii in a medical intensive care unit (ICU).

Methods

We retrospectively compared the relative incidence of A. baumannii infections in our unit over a 1-year period before (2012) and after (2016) the implementation of strict infection control bundles. Patients with A. baumannii infections were identified using the microbiology database of the National Health Laboratory Service's central data warehouse. The total number of admissions and clinical data were derived from the ICU registry.

Results

A. baumannii was isolated from 43/263 patients (16.35%) in 2012 compared with 37/348 patients in 2016 (10.63%, p=0.03; relative risk reduction=35%). We found almost 100% sensitivity to colistin and tigecycline, but 90% resistance to carbapenem antibiotics.

Conclusion

The introduction of strict infection control bundles had a statistically significant and clinically meaningful impact on the incidence of nosocomial A. baumannii infection in the medical ICU.

Trimethoprim-sulfamethoxazole vs. colistin or ampicillin-sulbactam for the treatment of carbapenem-resistant Acinetobacter baumannii: A retrospective matched cohort study

OBJECTIVES

This study aimed to assess the effectiveness of trimethoprim-sulfamethoxazole (TMP/SMX) as monotherapy for the treatment of carbapenem-resistant Acinobacter baumannii (A. baumannii) (CRAB) infections.

METHODS

This retrospective cohort study included patients receiving TMP/SMX as the main treatment for severe infections caused by CRAB, who were matched with patients treated with colistin or ampicillin-sulbactam (AMP/SUL) by age, Charlson score, department, and source of infection. Outcomes were compared among all patients and in a subgroup of propensity-score (PS) matched patients. The PS matching was performed using a match tolerance of 0.15 with replacement.

RESULTS

Fifty-three patients treated with TMP/SMX and 83 matched patients treated with colistin or AMP/SUL were included. Variables that were independently significantly associated with TMP/SMX treatment included admission for infection and septic shock, while abnormal cognition on admission and intensive care unit admission were associated with colistin or AMP/SUL treatment. All-cause 30-day mortality was lower with TMP/SMX compared with the comparator antibiotics among all patients (24.5%, 13 of 53 vs. 38.6%, 32 of 83, P=0.09) and in the PS-matched subgroup (29%, 9 of 31 vs. 55.2% 16 of 29, P=0.04). Treatment failure rates were not significantly different overall (34%, 18 of 53 vs. 42.4%, 35 of 83, P=0.339) and in the PS-matched subgroup (35.5%, 11 of 31 vs. 44.8%, 13 of 29, P=0.46). Time to clinical stability and hospitalization duration were significantly shorter with TMP/SMX. Patients treated with TMP/SMX probably had less severe infections than those treated with other antibiotics, even after matching.

CONCLUSIONS

TMP/SMX might be a valuable treatment option for TMP/SMX-susceptible CRAB infections. Given the very limited available treatment options, further studies assessing its effectiveness and safety are necessary.

Postoperative infection caused by Acinetobacter baumannii misdiagnosed as a free-living amoeba species in a humeral head hemiarthroplasty patient: a case report

BACKGROUND

Acinetobacter baumannii is ubiquitous, facultative intracellular, and opportunistic bacterial pathogen. Its unique abilities allow it to survive in a diverse range of environments, including health care settings, leading to nosocomial infections. And its exceptional ability to develop resistance to multiple antibiotics leaves few drug options for treatment. It has been recognized as a leading cause of nosocomial pneumonia and bacteremia over the world.

CASE PRESENTATION

In this case, a 73-year-old woman presented with a Neer Group VI proximal humeral fracture. Six hours after a successfully performed hemiarthroplasty, she developed continuous fever. Clinical examination revealed that the vitals were regular. Laboratory and radiographic examinations revealed only elevated procalcitonin levels. Blood culture revealed no bacterial or fungal growth. Cooling treatment and empirical broad-spectrum antibiotic therapy showed no apparent effect.

CONCLUSIONS

We report a postoperative infection caused by Acinetobacter baumannii. The infectious pathogen was identified via molecular DNA sequencing and was initially misidentified as a free-living amoeba species upon microscopic examinations. The patient was mistreated with antiamebic combination therapy. Her symptoms persisted for over 4 months and were eventually followed by her death.

Clinical and molecular epidemiology of Acinetobacter baumannii bloodstream infections in an endemic setting

AIM

The transmission dynamics of Acinetobacter baumannii in endemic settings, and the relation between microbial properties and patients' clinical outcomes, are yet obscure and hampered by insufficient metadata.

METHODS & RESULTS

Of 20 consecutive patients with A. baumannii bloodstream infection that were thoroughly analyzed at a single center, at least one transmission opportunity was evident for 85% of patients. This implies that patient-to-patient transmission is the major mode of A. baumannii acquisitions in health facilities. Moreover, all patients who died immediately (<24 h of admission) were infected with a single clone (ST457; relative risk = 1.6; p = 0.05).

CONCLUSION

This preliminary analysis should prompt further investigation by mapping genomic virulence determinants among A. baumannii ST457 lineage compared with other strains.

Clinical and Epidemiological Significance of Carbapenem Resistance in Acinetobacter baumannii Infections

Carbapenems are considered the treatment of choice for Acinetobacter baumannii infections. Many facilities implement preventive measures toward only carbapenem-resistant A. baumannii (CRAB). However, the independent role of the carbapenem resistance determinant on patient outcomes remains controversial. In a 6-year analysis of adults with A. baumannii bloodstream infection (BSI), the outcomes of 149 CRAB isolates were compared to those of 91 patients with carbapenem-susceptible A. baumannii In bivariable analyses, CRAB BSIs were significantly associated with worse outcomes and with a delay in the initiation of appropriate antimicrobial therapy (DAAT). However, in multivariable analyses, carbapenem resistance status was no longer associated with poor outcomes, while DAAT remained an independent predictor. The epidemiological significance of A. baumannii should not be determined by its resistance to carbapenems.

Controlling endemic multidrug-resistant Acinetobacter baumannii in Intensive Care Units using antimicrobial stewardship and infection control

BACKGROUND/AIMS

Nosocomial infections caused by multidrug-resistant (MDR) Acinetobacter baumannii have become public-health problem. However, few studies have evaluated the control of endemic MDR A. baumannii in Intensive Care Units (ICUs). Therefore, we investigated the effectiveness of antimicrobial stewardship and comprehensive intensified infection control measures for controlling endemic MDR A. baumannii in ICUs at a tertiary care center.

METHODS

Carbapenem use was strictly restricted through antimicrobial stewardship. Environmental cleaning and disinfection was performed at least 3 times per day in addition to basic infection control measures. Isolation using plastic curtains and contact precautions were applied to patients who were colonized or infected with MDR A. baumannii. The outcome was measured as the incidence density rate of hospital-onset MDR A. baumannii among patients in the ICUs.

RESULTS

The incidence density rate of hospital-onset MDR A. baumannii decreased from 22.82 cases per 1,000 patient-days to 2.68 cases per 1,000 patient-days after the interventions were implemented (odds ratio, 0.12; 95% confidence interval, 0.03 to 0.4; p < 0.001). The mean monthly use of carbapenems also decreased from 134.99 ± 82.26 defined daily doses per 1,000 patient-days to 94.85 ± 50.98 defined daily doses per 1,000 patient-days (p = 0.016).

CONCLUSIONS

Concomitant implementation of strict antimicrobial stewardship and comprehensive infection control measures effectively controlled endemic MDR A. baumannii in our ICUs within 1 year.

National Survey of Thai Infectious Disease Physicians on Treatment of Carbapenem-Resistant Acinetobacter baumannii Ventilator-Associated Pneumonia: The Role of Infection Control Awareness

OBJECTIVE To evaluate the expected and treatment outcomes of Thai infectious disease physicians (IDPs) regarding carbapenem-resistant Acinetobacter baumannii (CRAB) ventilator-associated pneumonia (VAP) METHODS From June 1, 2014, to March 1, 2015, survey data regarding the expected and clinical success rates of CRAB VAP treatment were collected from all Thai IDPs. The expected success rate was defined as the expectation of clinical response after CRAB VAP treatment for the given case scenario. Clinical success rate was defined as the overall reported success rate of CRAB VAP treatment based on the clinical practice of each IDP. The expected and clinical success rates were divided into low (80%) categories and were then compared with standard clinical response rates archived in the existing literature. RESULTS Of 183 total Thai IDPs, 111 (60%) were enrolled in this study. The median expected and clinical success rates were 68% and 58%, respectively. Using multivariate analysis, we determined that working in a hospital that implemented the standard intervention combined with an intensified infection control (IC) intervention for CRAB (adjusted odds ratio [aOR], 3.01; 95% confidence interval [CI], 1.17-7.73; P=.02) was associated with standard and high expected rates (>60%). Being a board-certified IDP (aOR, 5.76; 95% CI, 2.16-15.37; P60%). We identified a significant correlation between expected and clinical success rates (r=0.58; P<.001). CONCLUSIONS Awareness of IC among IDPs can improve physicians' expected and clinical success rates for CRAB VAP treatment, and treatment experience impacts overall treatment success. Infect. Control Hosp. Epidemiol. 2015;37(1):61-69.

Multidrug-resistant Acinetobacter baumannii infections in lung transplant patients in the cardiothoracic intensive care unit

BACKGROUND

Multidrug-resistant (MDR) gram-negative bacteria are a growing threat to solid organ transplantation (SOT) patients in the intensive care unit (ICU). We aimed to examine the mortality rates of gram-negative MDR bacterial infection in SOT patients compared with patient population undergoing other cardiothoracic surgeries and hospitalized under similar ICU conditions.

METHODS

A retrospective study from a single medical center, including patients with MDR Acinetobacter baumannii and carbapenem-resistant Klebsiella pneumoniae infection, hospitalized in the cardiothoracic ICU. Data were collected from computerized databases, and data were verified using the hospitalization files. Microbiological data were provided by the microbiology laboratory.

RESULTS

During the study period, 205 SOT patients and 5031 other patients were hospitalized in the cardiothoracic ICU. Active infection with gram-negative MDR bacteria was identified in 147 patients, of which 37 underwent SOT (18% of total transplant recipients) and 110 underwent another cardiothoracic surgery (2% of total patients who are not transplant recipients). Mortality rates were high among both groups of patients, with no significant difference between them.

CONCLUSIONS

Infection with resistant bacteria is more prevalent among patients following SOT compared with patients following other cardiothoracic surgeries. Mortality is high in all patients regardless of the immunocompromised condition.

Effect of carbapenem consumption patterns on the molecular epidemiology and carbapenem resistance of Acinetobacter baumannii

This study investigated the molecular epidemiology of Acinetobacter baumannii in the University of Debrecen in relation to antibiotic consumption. Overall and ward-specific antibiotic consumption was measured by the number of defined daily doses (DDD) per 100 bed-days between 2002 and 2012. Consumption was analysed against the number of A. baumannii positive patients per 100 bed-days, number of isolates per positive sample, and proportion of carbapenem resistant A. baumannii, using time-series analysis. Altogether 160 A. baumannii isolates from different wards were collected and analysed. Carbapenemase genes blaOXA-23-like , blaOXA-24-like , blaOXA-48-like , blaOXA-51-like , blaOXA-58-like and integrons were sought by PCR. Relatedness of isolates was assessed by PFGE. Prevalence and carbapenem resistance of A. baumannii were statistically associated with carbapenem consumption. Prevalence data followed carbapenem usage with three quarterly lags (r = 0.51–0.53, P<0.001), and meropenem and ertapenem, but not imipenem usage, affected prevalence. Colistin usage, in turn, lagged behind prevalence with one lag (r = 0.68–0.70, P<0.001). Six clusters were identified; the neurology ward with the lowest carbapenem consumption was associated with the carbapenem-susceptible cluster, as well as with the carbapenem-susceptible isolates in the cluster with variable susceptibility. Wards with high carbapenem usage almost exclusively harboured isolates from carbapenem-resistant clusters. All clusters were dominated by isolates of one or two wards, but most wards were represented in multiple clusters. Increases in prevalence and carbapenem resistance of A. baumannii were associated with usage of meropenem and ertapenem but not of imipenem, which led to the spread of multiple clones in the University.

Epidemiologic and clinical impact of Acinetobacter baumannii colonization and infection: a reappraisal

Acinetobacter baumannii is one of the most important antibiotic-resistant nosocomial bacteria. We investigated changes in the clinical and molecular epidemiology of A. baumannii over a 10-year period. We compared the data from 2 prospective multicenter cohort studies in Spain, one performed in 2000 (183 patients) and one in 2010 (246 patients), which included consecutive patients infected or colonized by A. baumannii. Molecular typing was performed by repetitive extragenic palindromic polymerase chain reaction (REP-PCR), pulsed-field gel electrophoresis (PFGE), and multilocus sequence typing (MLST). The incidence density of A. baumannii colonization or infection increased significantly from 0.14 in 2000 to 0.52 in 2010 in medical services (p < 0.001). The number of non-nosocomial health care-associated cases increased from 1.2% to 14.2%, respectively (p < 0.001). Previous exposure to carbapenems increased in 2010 (16.9% in 2000 vs 27.3% in 2010, p = 0.03). The drugs most frequently used for definitive treatment of patients with infections were carbapenems in 2000 (45%) and colistin in 2010 (50.3%). There was molecular-typing evidence of an increase in the frequency of A. baumannii acquisition in non-intensive care unit wards in 2010 (7.6% in 2000 vs 19.2% in 2010, p = 0.01). By MSLT, the ST2 clonal group predominated and increased in 2010. This epidemic clonal group was more frequently resistant to imipenem and was associated with an increased risk of sepsis, although not with severe sepsis or mortality. Some significant changes were noted in the epidemiology of A. baumannii, which is increasingly affecting patients admitted to conventional wards and is also the cause of non-nosocomial health care-associated infections. Epidemic clones seem to combine antimicrobial resistance and the ability to spread, while maintaining their clinical virulence.

Efficacy and safety of polymyxins for the treatment of Acinectobacter baumannii infection: a systematic review and meta-analysis

BACKGROUND

Multi-drug resistance among Acinetobacter baumannii increases the need for polymyxins. We conducted a meta-analysis aimed to assess the efficacy and safety of polymyxins for the treatment of Acinetobacter baumannii infection.

METHODS

We searched PUBMED, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), CNKI, Chinese Biomedical Literature Database up to November 1, 2013, to identify published studies, and we searched clinical trial registries to identify completed unpublished studies. Randomized controlled trials and cohort studies were considered for inclusion. Data were extracted on clinical response, microbiological response, mortality, length of stay and adverse events.

RESULTS

12 controlled studies, comparing 677 patients, were included. Although clinical (odds ratio 1.421, 95% confidence interval 0.722-2.797) and microbiological (OR 1.416, 95% CI 0.369-5.425) response rates favored the polymyxins group, these differences were not significant. Treatment with polymyxins vs. controls did not affect hospital mortality (OR 0.506, 95% CI 0.101-2.536), lengths of hospital stay (standard mean difference -0.221, 95% CI 0.899-0.458) or nephrotoxicity (OR 1.192, 95% CI 0.436-3.261). The combination of polymyxins with other antibiotics achieved similar clinical response rates to its monotherapy regimen (OR 0.601, 95% CI 0.320-1.130).

CONCLUSIONS

Our results suggest that polymyxins may be as safe and as efficacious as standard antibiotics for the treatment of A. baumannii infection. There is no strong evidence that combination regimen of polymyxins is superior to monotherapy regimen.

Epidemiology of bloodstream infections caused by Acinetobacter baumannii and impact of drug resistance to both carbapenems and ampicillin-sulbactam on clinical outcomes

Acinetobacter baumannii has become a leading cause of bloodstream infections (BSI) in health care settings. Although the incidence of infection with carbapenem- and ampicillin-sulbactam-resistant (CASR) A. baumannii has increased, there is a scarcity of studies which investigate BSI caused by CASR A. baumannii. A retrospective cohort study was conducted on adult patients with BSI caused by A. baumannii and who were admitted to the Detroit Medical Center between January 2006 and April 2009. Medical records were queried for patients' demographics, antimicrobial exposures, comorbidities, hospital stay, and clinical outcomes. Bivariate analyses and logistic regression were employed in the study. Two hundred seventy-four patients with BSI caused by A. baumannii were included in the study: 68 (25%) caused by CASR A. baumannii and 206 (75%) caused by non-CASR A. baumannii. In multivariate analysis, factors associated with BSI caused by CASR A. baumannii included admission with a rapidly fatal condition (odds ratio [OR] = 2.83, 95% confidence interval [CI] = 1.27 to 6.32, P value = 0.01) and prior use of antimicrobials (OR = 2.83, 95% CI = 1.18 to 6.78, P value = 0.02). In-hospital mortality rates for BSI caused by CASR A. baumannii were significantly higher than those for non-CASR A. baumannii-induced BSI (43% versus 20%; OR = 3.0, 95% CI = 1.60 to 5.23, P value < 0.001). However, after adjusting for potential confounders, the association between BSI caused by CASR A. baumannii and increased risk of in-hospital mortality was not significant (OR = 1.15, 95% CI = 0.51 to 2.63, P value = 0.74). This study demonstrated that CASR A. baumannii had a distinct epidemiology compared to more susceptible A. baumannii strains; however, clinical outcomes were similar for the two groups. Admission with a rapidly fatal condition was an independent predictor for both CASR A. baumannii and in-hospital mortality.

Analysis of hospital departmental distribution and antibiotic susceptibility of Acinetobacter isolated from sputum samples

The current study investigated Acinetobacter baumannii isolated from sputum specimens. Compared with previous studies, we found that A baumannii was drug resistant to 14 common antibiotics listed in Clinical and Laboratory Standard Institute guidelines (mean drug resistance rate: 80.9%) and was only sensitive to cefoperazone/sulbactam (sensitivity rate: 65.5%). With growing abuse of antibiotics, multidrug-resistant and pandrug-resistant strains of A baumannii have increased steadily and become a leading cause of hospital infections.

Sulbactam-based therapy for Acinetobacter baumannii infection: a systematic review and meta-analysis

BACKGROUND

A number of studies have reported on the effectiveness of sulbactam-based therapies for Acinetobacter baumannii infection; however, there is little evidence that sulbactam-based therapies are more or less effective than alternative therapies. Unfortunately, there is a distinct lack of high quality data (i.e., from randomized controlled trials) available on this issue. Therefore, we conducted a systematic review and meta-analysis comparing the efficacy of sulbactam-based and non-sulbactam-based regimens in the treatment of A. baumannii infection.

METHODS

We searched PubMed, MEDLINE, Biomedical Central, Google Scholar, the China National Knowledge Infrastructure, the Cochrane library, and the Directory of Open Access using the terms "sulbactam and baumannii" or "maxtam and baumannii". Randomized controlled trials, controlled clinical studies, and cohort studies were considered for inclusion. The primary outcome was the clinical response rate for sulbactam-based therapy vs comparator therapies.

RESULTS

Four studies (1 prospective, 3 retrospective) were included in the meta-analysis. Sulbactam was given in combination with ampicillin, carbapenem, or cefoperazone (n=112 participants). Comparator drugs included colistin, cephalosporins, anti-pseudomonas penicillins, fluoroquinolones, minocycline/doxycycline, aminoglycosides, tigecycline, polymyxin, imipenem/cilastatin, and combination therapy (n=107 participants). The combined clinical response rate odds ratio did not significantly favor sulbactam-based therapy over comparator therapy (odds ratio=1.054, 95% confidence interval=0.550-2.019, p=0.874), nor did any of the individual study odds ratios.

CONCLUSIONS

The available evidence suggests that sulbactam-based therapy may be similarly efficacious to alternative antimicrobial therapies for the treatment of A. baumannii infection. Further research on this issue is warranted given the limited availability of data from high quality/randomized controlled trials.

ICU-associated Acinetobacter baumannii colonisation/infection in a high HIV-prevalence resource-poor setting

BACKGROUND

There are hardly any data about the incidence, risk factors and outcomes of ICU-associated A.baumannii colonisation/infection in HIV-infected and uninfected persons from resource-poor settings like Africa.

METHODS

We reviewed the case records of patients with A.baumannii colonisation/infection admitted into the adult respiratory and surgical ICUs in Cape Town, South Africa, from January 1 to December 31 2008. In contrast to colonisation, infection was defined as isolation of A.baumannii from any biological site in conjunction with a compatible clinical picture warranting treatment with antibiotics effective against A.baumannii.

RESULTS

The incidence of A.baumannii colonisation/infection in 268 patients was 15 per 100 person-years, with an in-ICU mortality of 26.5 per 100 person-years. The average length of stay in ICU was 15 days (range 1-150). A.baumannii was most commonly isolated from the respiratory tract followed by the bloodstream. Independent predictors of mortality included older age (p = 0.02), low CD4 count if HIV-infected (p = 0.038), surgical intervention (p = 0.047), co-morbid Gram-negative sepsis (p = 0.01), high APACHE-II score (p = 0.001), multi-organ dysfunction syndrome (p = 0.012), and a positive blood culture for A.baumannii (p = 0.017). Of 21 A.baumannii colonised/infected HIV-positive persons those with clinical AIDS (CD4<200 cells/mm(3)) had significantly higher in-ICU mortality and were more likely to have a positive blood culture. Conclusion In this resource-poor setting A.baumannii infection in critically ill patients is common and associated with high mortality. HIV co-infected patients with advanced immunosuppression are at higher risk of death.

Risk factors for mortality in patients with carbapenem-resistant Acinetobacter baumannii bacteremia: impact of appropriate antimicrobial therapy

This study investigated predictors associated with 14-day mortality, and focused especially on the impact of appropriate antimicrobial treatment among patients with carbapenem-resistant Acinetobacter baumannii (CRAB) bacteremia. This retrospective study was performed at a tertiary care hospital in Korea from June 2007 to June 2010. Antibiotic therapy was considered appropriate if the antibiotics were administered via an appropriate route within 24 hr after the result of blood culture, had in vitro sensitivity to isolated strains, and of an adequate dosage according to the current guidelines. Ninety-five patients with A. baumannii bacteremia were included; of these, 53 (55.8%) were infected with CRAB. The overall infection-related 14-day mortality was higher in patients receiving inappropriate antimicrobial therapy than in patients receiving appropriate therapy (59.5% [22/37] vs 13.8% [8/58], P < 0.05). Multivariate analysis showed that septic shock (OR 10.5, 95% CI, 1.93-57.4; P = 0.006), carbapenem-resistance (OR 7.29, 95% CI 1.57-33.8; P = 0.01), pneumonia as a source of bacteremia (OR 5.29, 95% CI 1.07-26.1; P = 0.04), and inappropriate antimicrobial therapy (OR 8.05, 95% CI 1.65-39.2; P = 0.009) were independent risk factors for 14-day mortality. Early definite antimicrobial therapy had an influence on favorable outcomes in patients with A. baumannii bacteremia.

Poly-N-acetyl-β-(1-6)-glucosamine is a target for protective immunity against Acinetobacter baumannii infections

Acinetobacter baumannii has emerged as a highly troublesome, global pathogen. Treatment is complicated by high levels of antibiotic resistance, necessitating alternative means to prevent or treat A. baumannii infections. We evaluated an immunotherapeutic approach against A. baumannii, focusing on the surface polysaccharide poly-N-acetyl-β-(1-6)-glucosamine (PNAG). We used a synthetic oligosaccharide of 9 monosaccharide units (9Glc-NH(2)) conjugated to tetanus toxoid (TT) to induce antibodies in rabbits. In the presence of complement and polymorphonuclear cells, antisera to 9Glc-NH(2)-TT mediated the killing of A. baumannii S1, a high-PNAG-producing strain, but not its isogenic PNAG-negative, in-frame deletion mutant strain, S1 Δpga. Complementing the pgaABCD locus in trans in the shuttle vector pBAD18kan-ori, plasmid Δpga-c, restored the high levels of killing mediated by antibody to PNAG observed with the wild-type S1 strain. No killing was observed when normal rabbit serum (NRS) or heat-inactivated complement was used. Antiserum to 9Glc-NH(2)-TT was highly opsonic against an additional four unrelated multidrug-resistant clinical isolates of A. baumannii that synthesize various levels of surface PNAG. Using two clinically relevant models of A. baumannii infection in mice, pneumonia and bacteremia, antisera to 9Glc-NH(2)-TT significantly reduced levels of A. baumannii in the lungs or blood 2 and 24 h postinfection, respectively, compared to levels of control groups receiving NRS. This was true for all four A. baumannii strains tested. Overall, these results highlight the potential of PNAG as a vaccine component for active immunization or as a target for passive antibody immunotherapy.

Hospital acquired antibiotic-resistant acinetobacter baumannii infections in a 400-bed hospital in Tehran, Iran

OBJECTIVES

Acinetobacter baumannii is an omnipresent pathogen known as a major agent in healthcare and nosocomoal-associated infections. Its ability to develop resistant pattern to the major and broad spectrum antibiotics is an important issue to be studied.

METHODS

In this study, 101 strains of Acinetobacter baumannii were isolated from the hospitalized patients during July 2007 to June 2009 in one teaching hospital in the southern Tehran. The identification of Acinetobacter baumannii and resistant pattern was performed by using conventional bacteriological methods and Clinical Laboratory and Standards Institute (CLSI).

RESULTS

Respiratory tract specimens were the most common place of Acinetobacter isolation. The organism was resistant to ceftazidime (96%), ceftizoxime (95%), ceftriaxone (93%), amikacin (58%), gentamicin (68%), co-terimoxazole (85%), and ciprofloxacin (85%). This pattern also pointed that imipenem had the lowest resistance rate (9%).

CONCLUSIONS

Susceptibility rates of Acinetobacter baumannii isolates to third-generation cephalosporins, fluoroquinolones, amikacin, gentamicin, and trimethoprim/sulfamethoxazole (SXT) were very low and the rate of resistant Acinetobacter baumannii to imipenem was significant. It would be a good idea to consider surveillance of antibiotic usage and restriction of using broad spectrum antibiotics before development of resistance to these agents.

In vitro activity of tigecycline and comparators on Acinetobacter spp. isolates collected from patients with bacteremia and MIC change during the Tigecycline Evaluation and Surveillance Trial, 2004 to 2008

The Tigecycline Evaluation and Surveillance Trial is a global surveillance study established in 2004 to monitor the activity of tigecycline, a new glycylcycline, and several comparators against an array of important Gram-positive and Gram-negative pathogens. In this study, we examined 1591 isolates of Acinetobacter from blood samples collected from 352 centers globally between 2004 and 2008. Tigecycline showed an MIC(90) (1 microg/mL) globally, with a maximum regional value of 4 microg/mL (Middle East) reported. Antimicrobial susceptibility was notably higher among nonintensive care unit (non-ICU) isolates than isolates collected from ICUs. Carbapenem-resistant Acinetobacter were more prevalent in the Middle East, Latin America, and Asia/Pacific rim than in Europe or North America. Tigecycline creep was noted between 2004 and 2007, corresponding closely to changes in MIC(90).

Antimicrobial activity against Streptococcus pneumoniae and Haemophilus influenzae collected globally between 2004 and 2008 as part of the Tigecycline Evaluation and Surveillance Trial

We report here on the in vitro activity of tigecycline and comparators against a global collection of Streptococcus pneumoniae and Haemophilus influenzae collected between 2004 and 2008 as part of the Tigecycline Evaluation and Surveillance Trial. A total of 6785 S. pneumoniae and 6642 H. influenzae isolates were collected, most from North America. The percentages of penicillin-intermediate resistance and penicillin resistance among S. pneumoniae in North America were 27.8% and 14.3%, respectively. Penicillin resistance ranged from 9.3% in Europe to 25.1% in the Asia-Pacific Rim. The rate of beta-lactamase-producing H. influenzae was 25.8% in North America, and among the other regions, it ranged from 8.7% in South Africa to 26.8% in the Asia-Pacific Rim. Tigecycline MIC(90)'s were 0.03 to 0.12 mg/L and 0.5 to 2 mg/L, depending on the region considered, against S. pneumoniae and H. influenzae, respectively. Tigecycline had low MIC(90)'s against S. pneumoniae and H. influenzae, irrespective of resistance to beta-lactams.

Trends in antimicrobial resistance of Acinetobacter baumannii isolates from a metropolitan Detroit health system

A phenotypic and genotypic analysis of Acinetobacter baumannii was conducted from 2003 to 2008 in Detroit, MI. The incidence of A. baumannii increased from 1.7 to 3.7/1,000 patient days during the study period. Susceptibility to ampicillin-sulbactam and imipenem decreased from approximately 90% to approximately 40%. Genotyping revealed polyclonality, suggesting either emergence of multiple resistant strains or spread of a common genetic element. The sharp rise mandates major multidisciplinary interventions to optimize management of this multidrug-resistant pathogen.

Epidemiologic characterization of nosocomial Acinetobacter baumannii infections in a Turkish university hospital by pulsed-field gel electrophoresis

BACKGROUND

Although members of the Acinetobacter genus are not commonly part of the human flora, their relatively high prevalence in hospital environment frequently results in colonization of the skin and respiratory tract.

OBJECTIVES

The present investigation was carried out to elucidate epidemiologic characteristics of nosocomial Acinetobacter baumannii infections in a teaching hospital.

METHODS

Epidemiologic, clinical, and demographic features of the 66 patients with A baumannii infection during a 14-month period were recorded. Antibiotic susceptibilities of the isolates were determined by the standardized disk-diffusion method, and the clonal relationship of the isolates was analyzed by pulsed-field gel electrophoresis (PFGE).

RESULTS

The incidence of A baumannii infection was especially high in January, April, May, and June 2006. The isolates were most frequently obtained from blood and tracheal aspirates sent from the intensive care unit and neurosurgery ward. Although the most frequently identified predisposing factors were cerebrovascular disease and surgical operation, the main risk factors identified in these patients were catheterization and mechanical ventilation. Genotype analysis of the 66 A baumannii strains by PFGE revealed the circulation of 36 different PFGE types, of which type A (12) and K (17) accounted for 44% of the isolates. We found high clonal relationship (80.3%) among the typed strains. Thirteen antibiotypes were observed. Most of the isolates were multidrug resistant. Resistance to imipenem, meropenem, gentamicin, amikacin, tobramycin, netilmicin, ampicillin-sulbactam, trimethoprim-sulfamethoxazole, piperacillin-tazobactam, cefoperazone-sulbactam, ciprofloxacin, and levofloxacin were found in 44%, 47%, 47%, 84.8%, 21.2%, 3%, 62.1%, 57.6%, 94%, 62.1%, 95.5%, and 95.5% of the isolates, respectively.

CONCLUSION

The epidemiologic data obtained suggested that the increase in the number of A baumannii infections in our hospital was caused by the interhospital spread of especially 2 epidemic clones. We determined that clonally related strains can survive for a long time in our hospital and cause nosocomial infections in the predisposed patients.

Mortality rates associated with multidrug-resistant Acinetobacter baumannii infection in surgical intensive care units

A retrospective, propensity-matched cohort study was conducted to determine the mortality rate in patients with healthcare-associated infection (HAI) due to multidrug-resistant (MDR) Acinetobacter baumannii. The 28-day mortality rate for patients with MDR A. baumannii HAI was not significantly different than that for patients with non-MDR A. baumannii HAI. The median length of hospital stay before diagnosis of HAI was 4.5 days longer for patients with MDR A. baumannii infection than for patients with non-MDR A. baumannii infection (P < .001).

Current control and treatment of multidrug-resistant Acinetobacter baumannii infections

Institutional outbreaks caused by Acinetobacter baumannii strains that have acquired multiple mechanisms of antimicrobial drug resistance constitute a growing public-health problem. Because of complex epidemiology, infection control of these outbreaks is difficult to attain. Identification of potential common sources of an outbreak, through surveillance cultures and epidemiological typing studies, can aid in the implementation of specific control measures. Adherence to a series of infection control methods including strict environmental cleaning, effective sterilisation of reusable medical equipment, attention to proper hand hygiene practices, and use of contact precautions, together with appropriate administrative guidance and support, are required for the containment of an outbreak. Effective antibiotic treatment of A baumannii infections, such as ventilator-associated pneumonia and bloodstream infections, is also of paramount importance. Carbapenems have long been regarded as the agents of choice, but resistance rates have risen substantially in some areas. Sulbactam has been successfully used in the treatment of serious A baumannii infections; however, the activity of this agent against carbapenem-resistant isolates is decreasing. Polymyxins show reliable antimicrobial activity against A baumannii isolates. Available clinical reports, although consisting of small-sized studies, support their effectiveness and mitigate previous concerns for toxicity. Minocycline, and particularly its derivative, tigecycline, have shown high antimicrobial activity against A baumannii, though relevant clinical evidence is still scarce. Several issues regarding the optimum therapeutic choices for multidrug-resistant A baumannii infections need to be clarified by future research.

Acinetobacter baumannii: emergence of a successful pathogen

Acinetobacter baumannii has emerged as a highly troublesome pathogen for many institutions globally. As a consequence of its immense ability to acquire or upregulate antibiotic drug resistance determinants, it has justifiably been propelled to the forefront of scientific attention. Apart from its predilection for the seriously ill within intensive care units, A. baumannii has more recently caused a range of infectious syndromes in military personnel injured in the Iraq and Afghanistan conflicts. This review details the significant advances that have been made in our understanding of this remarkable organism over the last 10 years, including current taxonomy and species identification, issues with susceptibility testing, mechanisms of antibiotic resistance, global epidemiology, clinical impact of infection, host-pathogen interactions, and infection control and therapeutic considerations.

Treatment options for multidrug-resistant Acinetobacter species

Multidrug-resistant Acinetobacter spp. are emerging nosocomial pathogens and have become a leading cause of Gram-negative infections in many parts of the world. Acinetobacter spp. are commonly implicated in bloodstream infection, hospital-acquired pneumonia, and wound and other surgical-site infections. They are difficult to treat, thus often leading to adverse patient outcome. Group II carbapenems (imipenem/cilastatin and meropenem) are the agents of choice for the treatment of severe infections caused by Acinetobacter spp. isolates susceptible to this antimicrobial group, but infection with carbapenem-resistant strains is increasingly encountered. Therapy of such infections necessitates the use of old drugs (e.g. colistin), unusual drugs (e.g. sulbactam) or drugs with which there is presently little clinical experience (e.g. tigecycline). Case reports, case series and small comparative observational studies suggest that these regimens are efficacious and demonstrate lower-than-expected toxicity, but there is substantial variation between these reports. Combination antimicrobial therapy is often used to treat infections caused by such multidrug-resistant strains. This article summarizes the cumulative experience with and the evidence for treating infections caused by multidrug-resistant Acinetobacter spp. infections. Special emphasis is placed on the use of 'non-traditional' antimicrobial agents, various aspects of combination therapy, alternative routes of drug administration, and discrete entities such as ventilator-associated pneumonia and postsurgical meningitis.

Use of sequence-based typing and multiplex PCR to identify clonal lineages of outbreak strains of Acinetobacter baumannii

Representatives (n = 31) of outbreak strains of Acinetobacter baumannii from five countries fell into three clear groups, designated Groups 1-3, based on their ompA (outer-membrane protein A), csuE (part of a pilus assembly system required for biofilm formation) and bla(OXA-51-like) (the intrinsic carbapenemase gene in A. baumannii) gene sequences. With the exception of the closely related alleles within the Group 1 clonal complex, alleles at each locus were highly distinct from each other, with a minimum of 14 nucleotide differences between any two alleles. Isolates within a group shared the same combination of alleles at the three loci, providing compelling evidence that the outbreak strains investigated belonged to three clonal lineages. These corresponded to the previously identified European clones I-III. Sequence differences among the alleles were used to design multiplex PCRs to rapidly assign isolates belonging to particular genotypes to sequence groups. In the UK, genotypes belonging to the Group 1 clonal complex have been particularly successful, accounting for the vast majority of isolates referred from hospitals experiencing problems with Acinetobacter.

Impact of multi-drug-resistant Acinetobacter baumannii on clinical outcomes

We conducted a retrospective matched cohort study to examine the impact of isolation of multi-drug-resistant (MDR) Acinetobacter baumannii on patient outcomes. Cases from whom MDR A. baumannii was isolated in a clinical culture (n = 118) were compared with controls from whom MDR A. baumannii was not isolated (n = 118). Cases and controls were matched according to ward, calendar month of hospitalization, and duration of hospitalization before culture. The following outcomes were compared in multivariable analysis: in-hospital mortality, length of stay, need for mechanical ventilation, and functional status at discharge. MDR A. baumannii was determined to be a pathogen in 72% of cases. In 36% of cases, the patient died, versus 21% of controls (odds ratio [OR] 2.21, 95% confidence interval [CI] 1.17-4.16, P = 0.014). Median length of stay for surviving cases was 17 days, versus 11 for surviving controls (multiplicative effect 1.55, 95% CI 0.99-2.44, P = 0.057). Fifty-two percent of cases required mechanical ventilation, versus 25% of controls (OR 3.72, 95% CI 1.91-7.25, P<0.001); 60% of surviving cases were discharged with reduced functional status, versus 38% of controls (OR 4.4, 95% CI 1.66-11.61, P = 0.003). In multivariable analysis, clinical isolation of MDR A. baumannii remained a significant predictor of mortality (OR 6.23, 95% CI 1.31-29.5, P = 0.021), need for mechanical ventilation (OR 7.34, 95% CI 2.24-24.0, P<0.001), and reduced functional status on discharge (OR 7.93, 95% CI 1.1-56.85, P = 0.039). Thus, MDR A. baumannii acquisition is associated with severe adverse outcomes, including increased mortality, need for mechanical ventilation, and reduced functional status.

Outcomes ofAcinetobacter baumanniiInfection in Critically Ill Surgical Patients

BACKGROUND

Multi-drug resistant (MDR) organisms in intensive care units (ICUs) are a growing concern. The emergence of several infections with MDR Acinetobacter baumannii prompted a review of cases and evaluation of the efficacy of intervention.

OBJECTIVE

To determine the rate of clinical cure, the incidence of drug resistance, and the mortality rate associated with A. baumannii infection.

METHOD

Retrospective review of A. baumannii infections in three surgical ICUs between January, 2004 and November, 2005. Infection was identified in 291 patients, 20 of whom were excluded because of incomplete documentation. Of the remaining 271 patients, 71% were male, and the mean age was 47 +/- 18 years (range 13-90 years).

RESULTS

Patients had a mean length of stay in the ICU of 14 days (range 0-136 days) before infection. The initial positive cultures were from bronchoalveolar lavage fluid (BAL) in 72.3%, blood in 16.2%, a catheter tip in 6.3%, urine in 1.8%, wound in 2.2%, and abscess in 1.1%. In 46.9% of patients, the first culture was polymicrobial. The Acinetobacter isolates were resistant or intermediate-resistant to imipenem-cilastatin in 81.2% of cases; 19.9% were resistant to all drugs except colistin, and two were resistant to all tested drugs. Colistin was used in 75.6% of patients (intravenous 61.5%, nebulized 38.5%). The mean duration of treatment was 13 +/- 8.9 days (range 0-56 days), and clinical cure was achieved in 73.8% of patients. Recurrent infection after initial cure was found in 19.2% of patients. There was no significant difference in clinical cure rates between patients treated with colistin and those treated with other culture-directed drugs (75.1% vs. 69.7%), or between patients treated with intravenous vs. nebulized colistin (72.4% vs. 79.5%). The mortality rate was 26.2% for the entire group and was significantly higher in the subgroup of transplant patients (n = 31) (64.5% vs. 21.4%; p < 0.001).

CONCLUSION

The majority of A. baumannii isolates were MDR, and a significant proportion were sensitive only to colistin. Treatment of A. baumannii infection with colistin is effective by both intravenous and nebulized routes of administration. However, infection with A. baumannii in critically ill surgical patients is associated with a high mortality rate, particularly in transplant patients.