An outbreak of imipenem-resistant Acinetobacter baumannii in critically ill surgical patients

A systematic review and meta-analysis for risk factor profiles in patients with resistant Acinetobacter baumannii infection relative to control patients

BACKGROUND

Acinetobacter baumannii is a major cause of nosocomial infections and high mortality rates. Evaluation of risk factors for such resistant infections may aid surveillance and diagnostic initiatives, as well as, can be crucial in early and appropriate antibiotic therapy.

OBJECTIVE

To identify the risk factors in patients with resistant A. baumannii infection with respect to controls.

METHODS

Prospective or retrospective cohort and case-control studies reporting the risk factors for resistant A. baumannii infection were collected through two data sources, MEDLINE/PubMed and OVID/Embase. Studies published in the English language were included while animal studies were excluded. The Newcastle-Ottawa Scale was used to assess the quality of studies. The odds ratio of developing antibiotic resistance in patients with A. baumannii infection was pooled using a random-effect model.

RESULTS

The results are based on 38 studies with 60878 participants (6394 cases and 54484 controls). A total of 28, 14, 25, and 11 risk factors were identified for multi-drug resistant (MDRAB), extensive-drug resistant (XDRAB), carbapenem-resistant (CRAB) and imipenem resistant A. baumannii infection (IRAB), respectively. In the MDRAB infection group, exposure to carbapenem (OR 5.51; 95% CI: 3.88-7.81) and tracheostomy (OR 5.01; 95% CI: 2.12-11.84) were identified with maximal pool odd's ratio. While previous use of amikacin (OR 4.94; 95% CI: 1.89-12.90) and exposure to carbapenem (OR 4.91; 95% CI: 2.65-9.10) were the foremost factors associated with developing CRAB infection. Further analysis revealed, mechanical ventilation (OR 7.21; 95% CI: 3.79-13.71) and ICU stay (OR 5.88; 95% CI: 3.27-10.57) as the most significant factors for XDRAB infection.

CONCLUSION

The exposure of carbapenem, amikacin (previous) and mechanical ventilation were the most significant risk factors for multidrug, extensive-drug, and carbapenem resistance in patients with A. baumannii infection respectively. These findings may guide to control and prevent resistant infections by identifying the patients at higher risk of developing resistance.

Management of a Major Carbapenem-Resistant Acinetobacter baumannii Outbreak in a French Intensive Care Unit While Maintaining Its Capacity Unaltered

We describe bundle measures implemented to overcome a protracted carbapenem-resistant Acinetobacter baumannii (CRAB) outbreak in an 18-bed trauma Intensive Care Unit (ICU) at Strasbourg University Hospital, a tertiary referral center in France. Outbreak cases were defined by a positive CRAB sample with OXA-23 profile during or after ICU say. To sustain the capacity of the busy trauma ICU, infection control bundles were purposely selected to control the outbreak without closing the ICU. During the outbreak, from May 2015 to January 2019, 141 patients were contaminated by CRAB, including 91 colonized and 50 infected patients. The conventional infection and prevention control (IPC) measures implemented included weekly active surveillance of patients’ samples, enhancement of environmental cleaning, interventions to improve hand hygiene compliance and antibiotic stewardship with audits. Supplemental measures were needed, including environmental samplings, health care workers’ (HCWs) hand sampling, chlorhexidine body-washing, relocation of the service to implement Airborne Disinfection System (ADS), replication of crisis cells, replacement of big environmental elements and improvement of HCW organization at the patient’s bedside. The final measure was the cohorting of both CRAB patients and HCW caring for them. Only the simultaneous implementation of aggressive and complementary measures made it possible to overcome this long-lasting CRAB epidemic. Facing many CRAB cases during a rapidly spreading outbreak, combining simultaneous aggressive and complementary measures (including strict patients and HCW cohorting), was the only way to curb the epidemic while maintaining ICU capacity.

Importance of control groups when delineating antibiotic use as a risk factor for carbapenem resistance, extreme-drug resistance, and pan-drug resistance in Acinetobacter baumannii and Pseudomonas aeruginosa: A systematic review and meta-analysis

BACKGROUND

Carbapenem-resistant (CR), extremely drug-resistant (XDR), and pan-drug-resistant (PDR) Acinetobacter baumannii and Pseudomonas aeruginosa pose a huge clinical threat. This study reviews the impact of control groups on the association of antecedent antibiotic use and the acquisition of CR/XDR/PDR A. baumannii and P. aeruginosa.

METHODS

Studies investigating the role of antibiotics as a risk factor for CR/XDR/PDR A. baumannii and P. aeruginosa acquisition in adult hospitalized patients from 1950 to 2016 were identified in the databases. These were divided into two groups: antibiotic-resistant versus antibiotic-sensitive pathogens (group I); antibiotic-resistant versus no infection (group II). A random-effects model was performed.

RESULTS

Eighty-five studies (46 A. baumannii, 38 P. aeruginosa, and one of both) involving 22 396 patients were included. CR was investigated in 60 studies, XDR in 20 studies, and PDR in two studies. Prior antibiotic exposure was associated with significant acquisition of CR/XDR/PDR A. baumannii and P. aeruginosa in both groups I and II (p<0.05). Antibiotic classes implicated in both groups included aminoglycosides, carbapenems, glycopeptides, and penicillins. Cephalosporin use was not associated with resistance in either group. Fluoroquinolone exposure was only associated with resistance in group I but not group II.

CONCLUSIONS

Control groups play an important role in determining the magnitudes of risk estimates for risk factor studies, hence careful selection is necessary. Antibiotic exposure increases the acquisition of highly resistant A. baumannii and P. aeruginosa, thus appropriate antibiotic use is imperative.

The Organisms and Factors Affecting Outcomes of External Ventricular Drainage Catheter-Related Ventriculitis: A Penang Experience

Introduction:

Ventriculostomy-related infection (VRI) from external ventricular drain (EVD) insertion is a common complication and carries a high mortality rate. Choice of empiric antibiotics depends on the institutions common causative organisms and their susceptibility. We determined risk factors for mortality in patients with VRI, the common organisms causing VRI, and the rate of EVD-related VRI at our institution.

Methods:

Medical records and operative data of patients with cerebrospinal fluid positive cultures with an EVD inserted from 2012 to 2015 were traced. Forty-five patients with EVD-related VRI were included in the study.

Results:

The overall rate of VRI was 6.3%, and the overall mortality rate due to VRI was 48.9%. Acinetobacter baumannii was the most common organism causing VRI (14 patients, 29.2%) with a mortality rate of 64.3%. Only 14.3% of A. baumannii are sensitive to meropenem and imipenem. We found that patients that had a decompressive craniectomy (DC) had a lower mortality rate (P = 0.042) and patients with a longer duration of the EVD being in place before the diagnosis of VRI had poor outcome (P = 0.040). Multivariate logistic regression was performed and we found that the use of steroid (P = 0.014), Pseudomonas aeruginosa infection (P = 0.010), multiple organism infection (P = 0.017), lower Glasgow Coma Scale (P = 0.043), and a longer duration the EVD was in place before the diagnosis of VRI (P = 0.008) were related with higher mortality.

Conclusion:

VRI mortality rate is high with an alarming resistance pattern seen in Acinetobacter VRI. EVDs should be removed as soon as feasible, and DC may be offered to patients with severe ventriculitis or meningitis.

A realist analysis of hospital patient safety in Wales: applied learning for alternative contexts from a multisite case study

Background

Hospital patient safety is a major social problem. In the UK, policy responses focus on the introduction of improvement programmes that seek to implement evidence-based clinical practices using the Model for Improvement, Plan-Do-Study-Act cycle. Empirical evidence that the outcomes of such programmes vary across hospitals demonstrates that the context of their implementation matters. However, the relationships between features of context and the implementation of safety programmes are both undertheorised and poorly understood in empirical terms.

Objectives

This study is designed to address gaps in conceptual, methodological and empirical knowledge about the influence of context on the local implementation of patient safety programmes.

Design

We used concepts from critical realism and institutional analysis to conduct a qualitative comparative-intensive case study involving 21 hospitals across all seven Welsh health boards. We focused on the local implementation of three focal interventions from the 1000 Lives+patient safety programme: Improving Leadership for Quality Improvement, Reducing Surgical Complications and Reducing Health-care Associated Infection. Our main sources of data were 160 semistructured interviews, observation and 1700 health policy and organisational documents. These data were analysed using the realist approaches of abstraction, abduction and retroduction.

Setting

Welsh Government and NHS Wales.

Participants

Interviews were conducted with 160 participants including government policy leads, health managers and professionals, partner agencies with strategic oversight of patient safety, advocacy groups and academics with expertise in patient safety.

Main outcome measures

Identification of the contextual factors pertinent to the local implementation of the 1000 Lives+patient safety programme in Welsh NHS hospitals.

Results

An innovative conceptual framework harnessing realist social theory and institutional theory was produced to address challenges identified within previous applications of realist inquiry in patient safety research. This involved the development and use of an explanatory intervention–context–mechanism–agency–outcome (I-CMAO) configuration to illustrate the processes behind implementation of a change programme. Our findings, illustrated by multiple nested I-CMAO configurations, show how local implementation of patient safety interventions are impacted and modified by particular aspects of context: specifically, isomorphism, by which an intervention becomes adapted to the environment in which it is implemented; institutional logics, the beliefs and values underpinning the intervention and its source, and their perceived legitimacy among different groups of health-care professionals; and the relational structure and power dynamics of the functional group, that is, those tasked with implementing the initiative. This dynamic interplay shapes and guides actions leading to the normalisation or the rejection of the patient safety programme.

Conclusions

Heightened awareness of the influence of context on the local implementation of patient safety programmes is required to inform the design of such interventions and to ensure their effective implementation and operationalisation in the day-to-day practice of health-care teams. Future work is required to elaborate our conceptual model and findings in similar settings where different interventions are introduced, and in different settings where similar innovations are implemented.

Funding

The National Institute for Health Research Health Services and Delivery Research programme.

Infection Control Programs and Antibiotic Control Programs to Limit Transmission of Multi-Drug Resistant Acinetobacter baumannii Infections: Evolution of Old Problems and New Challenges for Institutes

Background: Acinetobacter baumannii complex (A. baumannii) has been isolated worldwide. The rapid spread of multidrug-resistant A. baumannii complex (MDRAB) in clinical settings has made choosing an appropriate antibiotic to treat these infections and executing contact precautions difficult for clinicians. Although controlling the transmission of MDRAB is a high priority for institutions, there is little information about MDRAB control. Therefore, this study evaluated infection control measures for A. baumannii infections, clusters and outbreaks in the literature. Methods: We performed a review of OVID Medline (from 1980 to 2015), and analyzed the literature. Results: We propose that both infection control programs and antibiotic control programs are essential for control of MDRAB. The first, effective control of MDRAB infections, requires compliance with a series of infection control methods including strict environmental cleaning, effective sterilization of reusable medical equipment, concentration on proper hand hygiene practices, and use of contact precautions, together with appropriate administrative guidance. The second strategy, effective antibiotic control programs to decrease A. baumannii, is also of paramount importance. Conclusion: We believe that both infection control programs and antibiotics stewardship programs are essential for control of MDRAB infections.

Epidemiology of Multidrug-Resistant Bacteria in Patients With Long Hospital Stays

Objective.

To determine rates of colonization with multidrug-resistant (MDR) bacteria (ie, methicillin-resistantStaphylococcus aureus[MRSA], vancomycin-resistantEnterococcus[VRE], extended-spectrum β-lactamase [ESBL]-producing Enterobacteriaceae, andAcinetobacter baumannii) after prolonged hospitalization and to assess the yield of surveillance cultures and variables associated with colonization with MDR bacteria.

Design.

Prospective observational cohort study conducted from February 6 to May 26, 2006.

Methods.

All patients who spent more than 30 days in our university hospital (Paris, France) were included. Rectal and nasal swab samples obtained during day 30 screening were examined for MRSA, VRE, ESBL-producing Enterobacteriaceae, andA. baumannii.

Results.

Of 470 eligible patients, 439 had surveillance culture samples available for analysis, including 51 patients (11.6%) with a history of colonization or infection due to 1 or more types of MDR bacteria (MRSA, recovered from 35 patients; ESBL-producing Enterobacteriaceae, from 16 patients;A. baumannii, from 6 patients; and VRE, from 0 patients) and 37 patients (9.5% of the 388 patients not known to have any of the 4 MDR bacteria before day 30 screening) newly identified as colonized by 1 or more MDR bacteria (MRSA, recovered from 20 patients; ESBL-producing Enterobacteriaceae, from 16 patients;A. baumannii, from 1 patient; and VRE, from 0 patients). A total of 87 (19.8%) of 439 patients were identified as colonized or infected with MDR bacteria at day 30. Factors that differed between patients with and without MRSA colonization included age, McCabe score, comorbidity score, receipt of surgery, and receipt of fluoroquinolone treatment. Patients with ESBL-producing Enterobacteriaceae colonization were younger than patients with MRSA colonization.

Conclusions.

Differences in the variables associated with MRSA colonization and ESBL-producing Enterobacteriaceae colonization suggest differences in the epidemiology of these 2 organisms. Day 30 screening resulted in a 72.5% increase in the number of patients identified as colonized with at least 1 type of MDR bacteria.

Nosocomial Outbreak of Infection With Pan–Drug-ResistantAcinetobacter baumanniiin a Tertiary Care University Hospital

Objective.

TO describe what is, to our knowledge, the first nosocomial outbreak of infection with pan–drug-resistant (including colistin-resistant)Acinetobacter baumannii,to determine the risk factors associated with these types of infections, and to determine their clinical impact.

Design.

Nested case-control cohort study and a clinical-microbiological study.

Setting.

A 1,521-bed tertiary care university hospital in Seville, Spain.

Patients.

Case patients were inpatients who had a pan-drug-resistantA. baumanniiisolate recovered from a clinical or surveillance sample obtained at least 48 hours after admission to an intensive care unit (ICU) during the time of the epidemic outbreak. Control patients were patients who were admitted to any of the “boxes” (ie, rooms that partition off a distinct area for a patient's bed and the equipment needed to care for the patient) of an ICU for at least 48 hours during the time of the epidemic outbreak.

Results.

All the clinical isolates had similar antibiotic susceptibility patterns (ie, they were resistant to all the antibiotics tested, including Colistin), and, on the basis of repetitive extragenic palindromic-polymerase chain reaction, it was determined that all of them were of the same clone. The previous use of quinolones and glycopeptides and an ICU stay were associated with the acquisition of infection or colonization with pan-drug-resistant A.baumannii.To control this outbreak, we implemented the following multicomponent intervention program: the performance of environmental decontamination of the ICUs involved, an environmental survey, a revision of cleaning protocols, active surveillance for colonization with pan-drug-resistantA. baumannii,educational programs for the staff, and the display of posters that illustrate contact isolation measures and antimicrobial use recommendations.

Conclusions.

We were not able to identify the common source for these cases of infection, but the adopted measures have proven to be effective at controlling the outbreak.

Risk factors and outcomes for patients with bloodstream infection due to Acinetobacter baumannii-calcoaceticus complex

Identifying patients at risk for bloodstream infection (BSI) due to Acinetobacter baumannii-Acinetobacter calcoaceticus complex (ABC) and providing early appropriate therapy are critical for improving patient outcomes. A retrospective matched case-control study was conducted to investigate the risk factors for BSI due to ABC in patients admitted to the Detroit Medical Center (DMC) between January 2006 and April 2009. The cases were patients with BSI due to ABC; the controls were patients not infected with ABC. Potential risk factors were collected 30 days prior to the ABC-positive culture date for the cases and 30 days prior to admission for the controls. A total of 245 case patients were matched with 245 control patients. Independent risk factors associated with BSI due to ABC included a Charlson's comorbidity score of ≥ 3 (odds ratio [OR], 2.34; P = 0.001), a direct admission from another health care facility (OR, 4.63; P < 0.0001), a prior hospitalization (OR, 3.11; P < 0.0001), the presence of an indwelling central venous line (OR, 2.75; P = 0.011), the receipt of total parenteral nutrition (OR, 21.2; P < 0.0001), the prior receipt of β-lactams (OR, 3.58; P < 0.0001), the prior receipt of carbapenems (OR, 3.18; P = 0.006), and the prior receipt of chemotherapy (OR, 15.42; P < 0.0001). The median time from the ABC-positive culture date to the initiation of the appropriate antimicrobial therapy was 2 days (interquartile range [IQR], 1 to 3 days). The in-hospital mortality rate was significantly higher among case patients than among control patients (OR, 3.40; P < 0.0001). BSIs due to ABC are more common among critically ill and debilitated institutionalized patients, who are heavily exposed to health care settings and invasive devices.

Control of a Clonal Outbreak of Multidrug-Resistant Acinetobacter baumannii in a Hospital of the Basque Country after the Introduction of Environmental Cleaning Led by the Systematic Sampling from Environmental Objects

Background. Between July 2009 and September 2010, an outbreak of multidrug-resistant (MDR) Acinetobacter baumannii was detected in one critical care unit of a tertiary hospital in the Basque Country, involving 49 infected and 16 colonized patients. The aim was to evaluate the impact of environmental cleaning and systematic sampling from environmental objects on the risk of infection by MDR A. baumannii. Methods. After systematic sampling from environmental objects and molecular typing of all new MDR A. baumannii strains from patients and environmental isolates, we analyzed the correlation (Pearson's r) between new infected cases and positive environmental samples. The risk ratio (RR) of infection was estimated with Poisson regression. Results. The risk increased significantly with the number of positive samples in common areas (RR = 1.40; 95%CI = 0.99–1.94) and positive samples in boxes (RR = 1.19; 95%CI = 1.01–1.40). The number of cases also positively correlated with positive samples in boxes (r = 0.50; P < 0.05) and common areas (r = 0.29; P = 0.18). Conclusion. Once conventional measures have failed, environmental cleaning, guided by systematic sampling from environmental objects, provided the objective risk reduction of new cases and enabled the full control of the outbreak.

Repeated colonization by multi-drug-resistant Acinetobacter calcoaceticus-A. baumannii complex and changes in antimicrobial susceptibilities in surgical intensive care units

BACKGROUND

A nosocomial outbreak of multi-drug-resistant Acinetobacter calcoaceticus-A. baumannii (MDR-ACB) complex infection occurred in a newly constructed building at a 2,500-bed tertiary medical center in Taiwan.

METHODS

An investigation was carried out by molecular approaches to trace the bacteria. Antimicrobial susceptibilities, risk factors, and the occurrence of nosocomial MDR-ACB infections were investigated. From January to December 2009, 53 patients were infected with MDR-ACB, and 23 environmental surveys were performed in two surgical intensive care units (ICUs) within the new building. Forty-two clinical isolates were obtained from patients and 22 samples from nine environmental surveys.

RESULTS

Forty clinical isolates (95.2%) and 18 environmental samples (81.8%) were positive for MDR-ACB of type A, the predominant outbreak strain. This strain was identical to that isolated in an outbreak in the old hospital in 2006, as proved by repetitive extragenic palindromic-based polymerase chain reaction and pulsed-field gel electrophoresis. Although the outbreak isolates contained blaOXA-23-like and blaOXA-51-like genes, analysis of the antimicrobial susceptibilities demonstrated increases in resistance to cefepime and imipenem-cilastatin in MDR-ACB isolated in the later outbreak.

CONCLUSIONS

Not only patients or healthcare workers, but also medical equipment, might have carried the predominant outbreak strain from the old district to the new building. Therefore, even in a new environment, infection control programs must be enforced continually, and healthcare providers must be educated repeatedly to prevent recurrent outbreaks of MDR-ACB infection in the hospital setting.

Preventing multidrug-resistant gram-negative organisms in surgical patients

Multidrug-resistant gram-positive infections have consumed the attention of health care organizations as well as the media, but recently multidrug-resistant gram-negative organisms (MDR-GNOs) have become more and more prevalent. Limited treatment options are available for MDR-GNO infections; thus, prevention is key. Patients who are at high risk for developing infections must be identified, and specialized prevention interventions must be developed for their care. Surgical patients are one subset of patients at high risk for developing MDR-GNOs. Advanced practice nurses must support nurses and other health care personnel in preventing MDR-GNO infections. Education should include active surveillance, contact precautions, cohorting patients and staff members, unit closures, reinforced hand hygiene practices, and environmental cleaning tailored to the care of surgical patients in regard to their preoperative, intraoperative, and postoperative care.

In vitro activity of minocycline alone and in combination with cefoperazone-sulbactam against carbapenem-resistant Acinetobacter baumannii

The aim of this study was to investigate the in vitro activity of minocycline combined with cefoperazone-sulbactam against carbapenem-resistant Acinetobacter baumannii (CRAB). A total of 53 nonduplicate CRAB were collected from inpatients of intensive care units in three hospitals in China from February 2009 to August 2011. Minimum inhibitory concentrations were determined by the broth microdilution method. The checkerboard method was used to determine whether combinations of the two agents act synergistically. Among the 53 A. baumannii, 64.2% of the isolates were susceptible to amikacin and 69.8% were susceptible to cefoperazone-sulbactam. More than 80% of isolates were resistant to the other agents and no isolates were found resistant to polymyxin B and minocycline. The combination of minocycline and cefoperazone-sulbactam demonstrated synergism in 39 isolates, partial synergism in 11 isolates, and indifference in 3 isolates. No antagonistic interactions were observed. Our study demonstrated that minocycline has good activity against CRAB and the combination of minocycline with cefoperazone-sulbactam had significant synergistic activity against these strains in vitro. The combination of minocycline and cefoperazone-sulbactam may be an alternative option for the treatment of infections caused by CRAB.

Activity of a dry mist-generated hydrogen peroxide disinfection system against methicillin-resistant Staphylococcus aureus and Acinetobacter baumannii

BACKGROUND

The aim of this study was to evaluate the activity of a dry mist-generated hydrogen peroxide (DMHP) system (Sterinis; Gloster Sante Europe, Labege cedex, France) against methicillin-resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii.

METHODS

McFarland 0.5 suspensions of 2 test bacteria, either pure or containing 5% sterile serum, were prepared and inoculated onto sterile stainless steel disks. Each disk in a Petri dish-with the Petri dish cover either closed or open-was placed in different locations in an intensive care unit room. Quantitative cultures were performed after the cycle.

RESULTS

No growth occurred on the disks in the absence of a barrier, except 1 disk containing serum. Existence of a barrier, as a drawer or a covered Petri dish, caused failure in the disinfection activity. The mean reduction in initial log(10) bacterial count was lower for both of the test bacteria in presence of a barrier: 4.44- to 4.70-log(10) colony-forming units (cfu) decrease was observed in absence of a barrier, whereas 1.49- to 3.79-log(10) cfu decrease was observed in presence of a barrier. When the culture results were compared according to organic load content, the mean (±standard deviation) reduction of initial contamination in pure and in serum containing MRSA suspensions was 4.25 ± 1.20- and 3.34 ± 1.89-log(10) cfu, respectively. The mean (±standard deviation) reduction in pure and in serum containing A baumannii suspensions was 4.34 ± 0.89- and 3.87 ± 1.26-log(10) cfu, respectively. The differences were statistically significant (P < .001).

CONCLUSION

Sterinis was capable of killing MRSA and A baumannii on open surfaces; however, it was not effective in closed or semiclosed areas. Presence of serum also caused failure in the disinfection activity of the system.

Multidrug resistant acinetobacter

Emergence and spread of Acinetobacter species, resistant to most of the available antimicrobial agents, is an area of great concern. It is now being frequently associated with healthcare associated infections. Literature was searched at PUBMED, Google Scholar, and Cochrane Library, using the terms ‘Acinetobacter Resistance, multidrug resistant (MDR), Antimicrobial Therapy, Outbreak, Colistin, Tigecycline, AmpC enzymes, and carbapenemases in various combinations. The terms such as MDR, Extensively Drug Resistant (XDR), and Pan Drug Resistant (PDR) have been used in published literature with varied definitions, leading to confusion in the correlation of data from various studies. In this review various mechanisms of resistance in the Acinetobacter species have been discussed. The review also probes upon the current therapeutic options, including combination therapies available to treat infections due to resistant Acinetobacter species in adults as well as children. There is an urgent need to enforce infection control measures and antimicrobial stewardship programs to prevent the further spread of these resistant Acinetobacter species and to delay the emergence of increased resistance in the bacteria.

Clonal diversity of nosocomial epidemic Acinetobacter baumannii strains isolated in Spain

Acinetobacter baumannii is one of the major pathogens involved in nosocomial outbreaks. The clonal diversity of 729 epidemic strains isolated from 19 Spanish hospitals (mainly from intensive care units) was analyzed over an 11-year period. Pulsed-field gel electrophoresis (PFGE) identified 58 PFGE types that were subjected to susceptibility testing, rpoB gene sequencing, and multilocus sequence typing (MLST). All PFGE types were multidrug resistant; colistin was the only agent to which all pathogens were susceptible. The 58 PFGE types were grouped into 16 clones based on their genetic similarity (cutoff of 80%). These clones were distributed into one major cluster (cluster D), three medium clusters (clusters A, B, and C), and three minor clusters (clusters E, F, and G). The rpoB gene sequencing and MLST results reflected a clonal distribution, in agreement with the PFGE results. The MLST sequence types (STs) (and their percent distributions) were as follows: ST-2 (47.5%), ST-3 (5.1%), ST-15 (1.7%), ST-32 (1.7%), ST-79 (13.6%), ST-80 (20.3%), and ST-81 (10.2%). ST-79, ST-80, and ST-81 and the alleles cpn60-26 and recA29 are described for the first time. International clones I, II, and III were represented by ST-81, ST-2, and ST-3, respectively. ST-79 and ST-80 could be novel emerging clones. This work confirms PFGE and MLST to be complementary tools in clonality studies. Here PFGE was able to demonstrate the monoclonal pattern of most outbreaks, the inter- and intrahospital transmission of bacteria, and their endemic persistence in some wards. MLST allowed the temporal evolution and spatial distribution of Spanish clones to be monitored and permitted international comparisons to be made.

The impact of Acinetobacter baumannii infections on outcome in trauma patients: a matched cohort study

OBJECTIVE

To determine the impact of Acinetobacter baumannii infection on the outcome of trauma patients.

DESIGN AND SETTING

A retrospective 1:2-matched cohort study. Level I trauma intensive care unit patients with confirmed Acinetobacter baumannii infection were defined as cases.

PATIENTS

Thirty-one Acinetobacter baumannii patients were matched to 62 controls with evidence of infection caused by other microorganisms.

MEASUREMENTS AND MAIN RESULTS

There were 12 matching criteria, including focus of infection, demographics, severity, and characteristics of injury. In-hospital mortality rate, intensive care unit length of stay, and complications of Acinetobacter baumannii including multidrug-resistant strains in patients were compared to those of their controls; 81% had hospital-acquired pneumonia, 13% had bloodstream infections, and 6% had urinary tract infections in both groups. Acinetobacter baumannii cultures were multidrug resistant in 42% (13/31) of cases. The initial empirical antibiotic therapy was adequate in 71% (22/31). Although the in-hospital mortality was higher in the Acinetobacter baumannii group (16% vs. 13%; odds ratio, 1.23; 95% confidence interval, 0.38-4.36; p = .67), the difference did not reach statistical significance. Using the test of equivalence or clinical indifference, the impact of an Acinetobacter baumannii infection on mortality is inconclusive. This applies also to multidrug-resistant strains. Overall intensive care unit stay was prolonged for Acinetobacter baumannii when compared to controls (median, [range], 28 [7-181] days vs. 17 [2-130] days, respectively; p = .05). ARDS and acute liver failure were more frequent in the Acinetobacter baumannii group compared to the control group (35% vs. 15%; odds ratio, 3.24; 95% confidence interval, 1.17-5.48; p = .02 and 26% vs. 10%; odds ratio, 3.25; 95% confidence interval, 3.25-10.40; p = .04).

CONCLUSIONS

In this single-center experience, Acinetobacter baumannii infection, including multidrug-resistant strains, has inconclusive impact on mortality in a cohort of trauma patients. Larger studies are needed to support a definite conclusion. Acinetobacter baumannii infection was, however, associated with a longer intensive care unit stay and a higher rate of organ failure.

Effect of 1-(1-Naphtylmethyl)-piperazine, an efflux pump inhibitor, on antimicrobial drug susceptibilities of clinical Acinetobacter baumannii isolates

In this study, the effects of 1-(1-naphtylmethyl)-piperazine (NMP), an efflux pump inhibitor, on antimicrobial drug susceptibilities of 42 clinical Acinetobacter baumannii isolates were investigated by the disc diffusion method. The inhibition zone diameters of antibiotic discs were tested in the presence and absence of NMP and then these zone diameters were compared. Presence of NMP restored ciprofloxacin susceptibility in 15 intermediate and 2 resistant isolates. One ciprofloxacin resistant isolate became intermediate in the presence of NMP. One isolate resistant to gentamicin became intermediate with NMP. Interestingly, one isolate susceptible to meropenem became resistant in the presence of NMP. Although NMP increased the inhibition zone diameters of some of the tested antibiotics against the resistant isolates, the increase was not enough to restore susceptibility. In conclusion, the presence of NMP increases the zone diameters of ciprofloxacin and levofloxacin. Intermediate strains become susceptible but the resistant isolates do not.

A multicenter study of risk factors and outcome of hospitalized patients with infections due to carbapenem-resistant Acinetobacter baumannii

BACKGROUND

Risk factors and outcome in patients who acquire nosocomial infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) are rarely investigated.

METHODS

A multicenter retrospective study was conducted to analyze the clinical and microbiological data of patients with nosocomial infections due to A. baumannii in 10 hospitals around Taiwan from May 2004 to December 2006. Comparisons were made between patients with infections due to CRAB and patients with infections due to carbapenem-susceptible A. baumannii (CSAB).

RESULTS

One hundred and twenty-one patients carrying CRAB (infections, n=91) and 127 patients carrying CSAB (infections, n=97) were recruited for analysis. Compared with patients with CSAB infections, patients with CRAB infections had a longer duration of hospital stay before A. baumannii was isolated (median 48 vs. 21 days, p<0.001) and were more likely to have had exposure to a carbapenem (adjusted odds ratio (AOR) 2.57, 95% confidence interval (95% CI) 1.43-5.35; p=0.02) and an intensive care unit (ICU) stay (AOR 3.42, 95% CI 1.76-5.26; p=0.008). Risk factors associated with CRAB bacteremia included duration of hospital stay before onset of bacteremia (AOR 1.009 per 1-day longer, 95% CI 1.03-1.24; p=0.049), prior colonization with A. baumannii (AOR 3.27, 95% CI 1.99-5.93; p=0.002), and hospitalization in the ICU (AOR 6.12, 95% CI 1.58-13.68; p=0.009). Patients with CRAB bacteremia had a higher mortality rate than patients with CSAB bacteremia (46.0% vs. 28.3%, p=0.04). Multivariate analysis showed that carbapenem resistance (AOR 5.31, 95% CI 1.88-13.25; p=0.002), central venous catheterization (AOR 3.27, 95% CI 1.55-10.56; p=0.009), and ICU stay (AOR 2.56, 95% CI 1.15-8.85; p=0.04) were independent variables associated with mortality in patients with A. baumannii bacteremia.

CONCLUSIONS

Patients with CRAB infections have a higher mortality rate than those with CSAB infections. Longer hospital stay, colonization with A. baumannii, and admission to the ICU were associated with the development of CRAB bacteremia.

Risk factors and outcome of Acinetobacter baumanii infection in severe trauma patients

OBJECTIVE

To investigate incidence, risk factors and outcome of Acinetobacter baumanii infection in trauma patients.

DESIGN AND SETTING

A retrospective analysis of prospectively collected data of all trauma patients admitted to a general intensive care unit (ICU) of a 1,500-bed university hospital over 3 years.

PATIENTS

Three hundred thirty trauma patients were included in the study.

RESULTS

Thirty-six (10.9%) cases of A. baumanii infection were observed; 29 of them were late onset pneumonia. Patients with A. baumanii infection had a significantly higher Injury Severity Score (ISS) (p = 0.02), a lower Glasgow Coma Scale (GCS) on ICU admission (p = 0.03), stayed longer in the ICU (p = 0.00001), were mechanically ventilated for a longer period of time (p = 0.00001), were more frequently admitted to the emergency department with hypotension (p = 0.02), and had trans-skeletal traction for more than 3 days (p = 0.003) in comparison to the 294 patients who did not develop A. baumanii infection. At multivariate analysis the time spent on mechanical ventilation (p = 0.02) and the presence of long-term trans-skeletal traction (p = 0.04) were the only independent risk factors for A. baumanii infection. Patients with A. baumanii infection had a high mortality rate (9 out of 36; 25.0%). ISS (p = 0.003), GCS (p = 0.001) and older age (p = 0.00001), but not A. baumanii infection (p = 0.15), were independently correlated with mortality.

CONCLUSIONS

In trauma patients prolonged mechanical ventilation and delayed fracture fixation with the persistence of trans-skeletal traction were major risk factors for A. baumanii infection. The presence of this infection was not correlated with mortality.

Outbreak of carbapenem-resistant Acinetobacter baumannii carrying the carbapenemase OXA-23 in a German university medical centre

A prolonged outbreak of carbapenem-resistant Acinetobacter baumannii in a German university medical centre in 2006 was investigated; the investigation included a descriptive epidemiological analysis, a case-control study, environmental sampling, molecular typing of A. baumannii isolates using PFGE and repetitive-sequence-based PCR (rep-PCR) typing, and detection of OXA-type carbapenemases by multiplex PCR. Thirty-two patients acquired the outbreak strain in five intensive care units (ICUs) and two regular wards at a tertiary care hospital within 10 months. The outbreak strain was resistant to penicillins, cephalosporins, ciprofloxacin, gentamicin, tobramycin, imipenem and meropenem, and carried the bla(OXA-23)-like gene. Based on PFGE and rep-PCR typing, it was shown to be related to the pan-European A. baumannii clone II. The most likely mode of transmission was cross-transmission from colonized or infected patients via the hands of health-care workers, with the severity of disease and intensity of care (therapeutic intervention scoring system 28 score >median) being independently associated with acquisition of the outbreak strain (odds ratio 6.67, 95 % confidence interval 1.55-36.56). Control of the outbreak was achieved by enforcement of standard precautions, education of personnel, screening of ICU patients for carbapenem-resistant A. baumannii and cohorting of patients. This is believed to be the first report of an outbreak of A. baumannii carrying the carbapenemase OXA-23 in Germany.

Multidrug resistant Acinetobacter baumannii--the role of AdeABC (RND family) efflux pump in resistance to antibiotics

Acinetobacter baumannii is an opportunistic pathogen which play the more and more greater role in the pathogenicity of the human. It is often attached with the hospital environment, in which is able easily to survive for many days even in adverse conditions. Acinetobacter baumannii is the species responsible for a serious nosocomial infections, especially in the intensive care units. Option of surviving in natural niches, and in the hospital environment could also be associated with the efflux pump mechanisms. Mechanisms of efflux universally appear in all cells (eukaryotic and prokaryotic) and play the physiological important role. In prokaryote, the main functions are evasion of such naturally produced molecules, removal of metabolic products and toxins. These pumps could also be involved in an early stage of infection, such as adhesion to host cells and the colonization. Importantly, they remove commonly used antibiotics from the cell in therapy of infections caused by these bacteria. Efflux pumps exemplify a unique phenomenon in drug resistance: a single mechanism causing resistance against several different classes of antibiotics. In Acinetobacter baumannii, the AdeABC efflux pump, a member of the resistance-nodulation-cell division family (RND), has been well characterized. Aminoglicosides, tetracyclines, erythromycin, chloramphenicol, trimethoprim, fluoroquinolones, some beta-lactams, and also recently tigecycline, were found to be substrates for this pump. Drugs, as substrates for the AdeABC pump, can increase the expression of the AdeABC genes, leading to multidrug resistance (MDR). From this reason, treatment failure and death caused by Acinetobacter baumannii infections or underlying diseases are common. Because the AdeABC pump is widespread in Acinetobacter baumannii, similarly to other pumps in Gram-negative and Gram-positive bacteria, exists a need of searching a new therapeutic solutions. Specific efflux inhibitors of pumps (EPIs), including AdeABC inhibitors, could be suppress the activity of pumps and restore the sensitivity of such important bacteria as Acinetobacter baumannii to commonly used antibiotic.

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.

Multidrug-resistant Acinetobacter baumannii outbreak in an intensive care unit

Carbapenem-resistant Acinetobacter baumannii was isolated from 15 colonized or infected patients (carriers) between April and July 2004, in a teaching hospital ICU in Rome, Italy. All isolated strains were susceptible only to gentamicin, ampicillin-sulbactam and colistin and displayed the same Random Amplified Polymorphic DNA (RAPD) 1 pattern. Twelve out of 15 strains were susceptible to tigecycline, whereas the remaining three showed intermediate susceptibility. Although infection control measures were reinforced and carriers isolated in separate rooms, A. baumannii transmission continued. Therefore, finally A. baumannii carriers were moved to another available subintensive unit, which was re-equipped, and cared for by dedicated personnel, whereas only the non infected/colonized patients remained in the ICU. This study shows that during an outbreak by multiresistant A. baumannii it may be indispensable to geographically isolate not only patients but also dedicated staff.

Acinetobacter baumannii: a universal threat to public health?

Acinetobacter spp. are non-fermentative, strictly aerobic, Gram-negative microorganisms with a confusing taxonomic history. The Acinetobacter baumannii-Acinetobacter calcoaceticus complex is the species most commonly isolated from clinical specimens. It is ubiquitous in nature and has been found as part of the normal skin, throat and rectal flora as well as in food and body lice. It colonises patients in Intensive Care Units and contaminates inanimate hospital surfaces and devices as well as wounds, including war injuries. Although a frequent coloniser, Acinetobacter can be the cause of severe and sometimes lethal infections, mostly of nosocomial origin, predominantly ventilator-associated pneumonia. Bacteraemic infections are rare but may evolve to septic shock. Acinetobacter also emerges as a cause of nosocomial outbreaks and is characterised by increasing antimicrobial multiresistance. Antibiotic use, especially carbapenems and third-generation cephalosporins, is recognised as the most important risk factor for multiresistance. Described resistance mechanisms include hydrolysis by beta-lactamases, alterations in outer membrane proteins and penicillin-binding proteins, and increased activity of efflux pumps. Today, Acinetobacter resistant to carbapenems, aminoglycosides and fluoroquinolones presents a challenge to the clinician. However, sulbactam, tigecycline and colistin represent the current therapeutic approaches, which are associated with satisfactory efficacy.

Risk factors for nosocomial imipenem-resistant Acinetobacter baumannii infections

OBJECTIVES

To identify the risk factors for nosocomial imipenem-resistant Acinetobacter baumannii (IRAB) infections.

METHODS

A prospective case-control study, set in an 1100-bed referral and tertiary-care hospital, of all patients who had nosocomial A. baumannii infections between January 1 and December 31, 2004. Only the first isolation of A. baumannii was considered.

RESULTS

IRAB was isolated from 66 (53.7%) patients and imipenem-sensitive Acinetobacter baumannii (ISAB) was isolated from 57 (46.3%) patients during the study period. The mean duration of hospital stay until A. baumannii isolation was 20.8+/-13.6 days in IRAB infections, whereas it was 15.4+/-9.4 days in ISAB infections. Of the patients, 65.2% with IRAB infections and 40.4% with ISAB infections were followed at the intensive care unit (ICU). Previous carbapenem use was present in 43.9% of the patients with IRAB and 12.3% of the patients with ISAB infection. In univariate analysis female sex, longer duration of hospital stay until infection, ICU stay, emergent surgical operation, total parenteral nutrition, having a central venous catheter, endotracheal tube, urinary catheter or nasogastric tube, previous antibiotic use, and previous administration of carbapenems were significant risk factors for IRAB infections (p<0.05). In multivariate analysis, longer duration of hospital stay until A. baumannii isolation (odds ratio (OR) 1.043; 95% confidence interval (CI) 1.003-1.084; p=0.032), previous antibiotic use (OR 5.051; 95% CI 1.004-25.396; p=0.049), and ICU stay (OR 3.100; 95% CI 1.398-6.873; p=0.005) were independently associated with imipenem resistance.

CONCLUSIONS

Our results suggest that the nosocomial occurrence of IRAB is strongly related to an ICU stay and duration of hospital stay, and that IRAB occurrence may be favored by the selection pressure of previously used antibiotics.

The increasing role of Acinetobacter species as nosocomial pathogens

Among gram-negative organisms playing a significant role in nosocomial infections, Acinetobacter species have attracted increasing attention in intensive care units during the past two decades. Acinetobacter species are implicated in a wide spectrum of infections (eg, bacteremia, nosocomial pneumonia, urinary tract infections, secondary meningitis, superinfections in burn patients). One of the most striking features of Acinetobacter species is their extraordinary ability to develop multiple resistance mechanisms against major antibiotic classes. They have become resistant to broad-spectrum β-lactams (third-generation cephalosporins, carboxypenicillins, and increasingly to carbapenems); they produce a wide range of aminoglycoside-inactivating enzymes; and most strains are resistant to fluoroquinolones. In Acinetobacter nosocomial infections, the major problems confronting clinicians in intensive care units are related to the severity of Acinetobacter nosocomial infections and to resistance to major antibiotic classes of these organisms.

Exposure to quinolones is associated with carbapenem resistance among colistin-susceptible Acinetobacter baumannii blood isolates

In this study, we explored risk factors associated with bacteraemia caused by colistin-susceptible/carbapenem-resistant (Co(S)/Ca(R)) Acinetobacter baumannii. A retrospective cohort study of hospitalised patients with A. baumannii bacteraemia was performed at a tertiary care hospital over a 44-month period. Thirty-nine patients with bacteraemia due to A. baumannii (35 Intensive Care Unit and 4 ward patients) were included in the analysis. Twenty-five patients (64%) had bacteraemia due to Co(S)/Ca(R)A. baumannii and 14 patients (36%) had bacteraemia due to colistin-susceptible/carbapenem-susceptible A. baumannii. Mortality was 56% (14/25) and 35.7% (5/14) for patients in the two groups, respectively (P=0.22). Bivariate analysis showed that prior exposure to fluoroquinolones (P=0.01) and antipseudomonal penicillins (P=0.004) as well as a higher number of antibiotics in use on the day of bacteraemia (P=0.02) were associated with isolation of a Co(S)/Ca(R) strain among patients with A. baumannii bacteraemia. Multivariate analysis using a backward logistic regression model showed that only exposure to fluoroquinolones was associated with development of Co(S)/Ca(R)A. baumannii bacteraemia (odds ratio=11.6; 95% confidence interval 2.4-55.9; P=0.02). The appearance of Co(S)/Ca(R)A. baumannii infections represents a major threat to critically ill hospitalised patients. Exposure to fluoroquinolones is an independent risk factor for development of Co(S)/Ca(R)A. baumannii bacteraemia.

Carbapenem-resistant Acinetobacter baumannii in intensive care unit patients: risk factors for acquisition, infection and their consequences

A retrospective case-control study was performed to assess risk factors and the clinical and economic consequences associated with acquisition of carbapenem-resistant Acinetobacter baumannii (CR-AB) in an intensive care unit (ICU) over a 24-month period. CR-AB was acquired by 64 of 1431 ICU admissions; each was matched with two controls. Risk factors associated with CR-AB acquisition included ICU-wide variables, such as 'colonization pressure' (the prevalence of ICU colonized patients) and ICU antibiotic use over the preceding three months, as well as patient-related variables. Among colonized patients, risk factors for CR-AB infection included transfusion and 'colonization density' (the proportion of body sites colonized with CR-AB). CR-AB infection was independently associated with increased hospital mortality [mortality difference: 20%; 95% confidence interval (CI): 1-40%], prolonged ICU stay (median length of stay difference: 15 days; 95% CI: 9-21 days) and prolonged hospital stay (30 days, 11-38 days) compared with matched controls.

Impact of imipenem resistance on mortality in patients with Acinetobacter bacteraemia

OBJECTIVES

To investigate the impact of imipenem resistance on the mortality rate among patients with Acinetobacter bacteraemia.

METHODS

A retrospective, pairwise-matched (1:1), risk-adjusted (age, Pitt bacteraemia score) cohort study was performed at three tertiary care hospitals in Korea from January 2000 to June 2005.

RESULTS

Forty patients with imipenem non-susceptible Acinetobacter bacteraemia (INAB group) and 40 matched subjects (1:1 ratio) with imipenem-susceptible Acinetobacter bacteraemia (ISAB group) were included. Both groups had similar clinical features related to the severity of illness. The 30 day mortality rate was higher in the INAB group (57.5%) than the ISAB group (27.5%) (P = 0.007). The rate of discordant antimicrobial therapy was higher in the INAB group (65.0%) than the ISAB group (20.0%) (P < 0.001). The 30 day mortality rate was higher in the patients with discordant antimicrobial therapy (67.6%) than concordant antimicrobial therapy (23.9%) (P < 0.001). Multivariate analysis showed that age, the Pitt bacteraemia score, immunosuppressive status, and discordant antimicrobial therapy were independent risk factors for 30 day mortality among patients with Acinetobacter bacteraemia (P < 0.05). When discordant antimicrobial therapy was excluded in the multivariate analysis, the imipenem resistance was associated with 30 day mortality (P = 0.005).

CONCLUSIONS

Imipenem resistance has a significant impact on the mortality rate among patients with Acinetobacter bacteraemia, and this is mainly attributable to the higher rate of discordant antimicrobial therapy.

How long do nosocomial pathogens persist on inanimate surfaces? A systematic review

BACKGROUND

Inanimate surfaces have often been described as the source for outbreaks of nosocomial infections. The aim of this review is to summarize data on the persistence of different nosocomial pathogens on inanimate surfaces.

METHODS

The literature was systematically reviewed in MedLine without language restrictions. In addition, cited articles in a report were assessed and standard textbooks on the topic were reviewed. All reports with experimental evidence on the duration of persistence of a nosocomial pathogen on any type of surface were included.

RESULTS

Most gram-positive bacteria, such as Enterococcus spp. (including VRE), Staphylococcus aureus (including MRSA), or Streptococcus pyogenes, survive for months on dry surfaces. Many gram-negative species, such as Acinetobacter spp., Escherichia coli, Klebsiella spp., Pseudomonas aeruginosa, Serratia marcescens, or Shigella spp., can also survive for months. A few others, such as Bordetella pertussis, Haemophilus influenzae, Proteus vulgaris, or Vibrio cholerae, however, persist only for days. Mycobacteria, including Mycobacterium tuberculosis, and spore-forming bacteria, including Clostridium difficile, can also survive for months on surfaces. Candida albicans as the most important nosocomial fungal pathogen can survive up to 4 months on surfaces. Persistence of other yeasts, such as Torulopsis glabrata, was described to be similar (5 months) or shorter (Candida parapsilosis, 14 days). Most viruses from the respiratory tract, such as corona, coxsackie, influenza, SARS or rhino virus, can persist on surfaces for a few days. Viruses from the gastrointestinal tract, such as astrovirus, HAV, polio- or rota virus, persist for approximately 2 months. Blood-borne viruses, such as HBV or HIV, can persist for more than one week. Herpes viruses, such as CMV or HSV type 1 and 2, have been shown to persist from only a few hours up to 7 days.

CONCLUSION

The most common nosocomial pathogens may well survive or persist on surfaces for months and can thereby be a continuous source of transmission if no regular preventive surface disinfection is performed.

Risk factors for the isolation of multi-drug-resistant Acinetobacter baumannii and Pseudomonas aeruginosa: a systematic review of the literature

An understanding of the epidemiology of multi-drug-resistant (MDR) Acinetobacter baumannii and Pseudomonas aeruginosa infections is necessary in order to develop strategies to curtail their spread. For this purpose, the evidence linking the isolation of MDR A. baumannii and P. aeruginosa with specific risk factors was evaluated. PubMed was searched for the 20-year period from September 1985 to September 2005, and eligible studies were considered to be those that: (1) linked the isolation of A. baumannii and P. aeruginosa with specific risk factors; (2) described the characteristics of the affected patients in detail; and (3) provided data on the antibiotic resistance profile of the isolated micro-organisms. Fifty-five studies were found referring to A. baumannii (28 with case-control methodology and 27 outbreak investigations without case-control methodology), and 42 studies were found referring to P. aeruginosa (25 with case-control methodology and 17 outbreak investigations without case-control methodology). Although heterogeneous study designs and investigated risk factors limited this analysis, it was concluded that acquisition and spread of these micro-organisms appear to be related to a large number of variables. Among the most important were deficiencies in the implementation of infection control guidelines and the use of broad-spectrum antibiotics. Use of carbapenems and third-generation cephalosporins appear to be related to the development of an MDR phenotype by A. baumannii, while carbapenems and fluoroquinolones are implicated in MDR P. aeruginosa. The diversity of risk factors associated with the development of MDR A. baumannii and P. aeruginosa suggests that a separate outbreak investigation should be performed in each hospital setting. The development of innovative control strategies is needed in order to limit the spread of these pathogens.

Retrospective analysis of multidrug-resistant Acinetobacter baumannii strains isolated during a 4-year period in a university hospital

OBJECTIVE

To describe the epidemiology of Acinetobacter baumannii infection during 2000-2003 and to determine whether the multidrug-resistant strains were already present in our Toulouse hospital before the 2003 French national outbreak.

DESIGN

Descriptive molecular and clinical epidemiologic study of A. baumannii isolates using a combination of antibiotyping and pulsed-field gel electrophoresis (PFGE).

SETTING

A 1,000-bed university hospital in Toulouse, France.

METHODS

All clinical samples that had tested positive for A. baumannii between January 1, 2000, and December 31, 2003, were collected. Multidrug-resistant isolates of A. baumannii were then submitted to PFGE, and clinical characteristics of the source patients were noted.

RESULTS

A total of 1,277 A. baumannii samples were identified, 791 of which had not been previously identified; 148 were positive for multidrug-resistant strains. These strains were more likely to have been isolated in the intensive care unit (ICU) than were susceptible strains (P<.001; relative hazard, 3.77). The positive clinical samples were of various types (eg, nonprotected respiratory samples [43%] and blood [5%]), but no difference in type of source was seen between resistant and susceptible strains. A simultaneous analysis of pulsotypes and antibiotypes proved that the outbreak in the ICU in 2003 could be linked to an initially endemic clone that had been isolated in 2001. Furthermore, a second clone responsible for an extended-spectrum beta -lactamase phenotype was sporadically present in our institution. Although the strains isolated in the burn unit were also genetically related one to another, the specific responsible clone only appeared in 2003.

CONCLUSION

Several multidrug-resistant clones can coexist endemically for several years and can be detected during an outbreak by close survey of epidemic sources.

Acquisition of imipenem-resistant Acinetobacter baumannii in a pediatric intensive care unit: A case-control study

OBJECTIVE

To investigate the risk factors associated with nosocomial acquisition of imipenem-resistant Acinetobacter baumannii (IRAB) among pediatric intensive care patients. A retrospective case control study was conducted in a pediatric intensive care unit (PICU).

PATIENTS AND PARTICIPANTS

Cases were children in whom IRAB was isolated from any clinical specimen obtained at least 48 h following admission to PICU. Controls were children without IRAB matched to cases in 2:1 ratio. Twenty-six cases were matched with 52 controls according to the chronological order of admission.

MEASUREMENTS AND RESULTS

Between July 2001 and December 2003, 52 (62%) of 84 clinical A. baumannii isolates were found nonsusceptible to imipenem (MIC > or = 8 microg/ml). Demographic variables, comorbid conditions, clinical picture at admission, invasive procedures, use of antimicrobials and other drugs were analyzed as potential risk factors. Use of carbapenems and other beta-lactams, aminoglycosides, ranitidine, mechanical ventilation, central venous or urinary catheters and length of stay in PICU were among the factors significantly associated with IRAB acquisition in the univariate analysis. By multivariate analysis, however, only aminoglycoside use and length of stay in the PICU were independent risk factors.

CONCLUSIONS

Acquisition of IRAB by PICU patients was independently associated with aminoglycoside use and prolonged stay in the unit. Studies of evaluation of infection control policies need to be pursued.

Control of an outbreak of multidrug-resistant Acinetobacter baumannii-calcoaceticus colonization and infection in an intensive care unit (ICU) without closing the ICU or placing patients in isolation

OBJECTIVE

To describe the control of multidrug-resistant Acinetobacter baumannii-calcoaceticus (MDRABC) colonization and infection in an intensive care unit (ICU).

SETTING

An 18-bed ICU in a large tertiary care teaching hospital in London.

INTERVENTIONS

After recognition of the outbreak, a range of infection control measures were introduced over several months that were primarily aimed at reducing environmental contamination with the outbreak strain. Strategies included use of a closed tracheal suction system for all patients receiving mechanical ventilation, use of nebulized colistin for patients with evidence of mild to moderate ventilator-associated pneumonia, improved availability of alcohol for hand decontamination, and clearer designation of responsibilities and strategies for cleaning equipment and the environment in the proximity of patients colonized or infected with MDRABC.

RESULTS

The outbreak lasted from June 2001 through November 2002 and involved 136 new cases of MDRABC infection or colonization. The number of newly diagnosed cases per month reached a maximum of 15 in February 2002, and the number of new cases slowly decreased over the next 9 months.

CONCLUSION

This outbreak was controlled by emphasizing the control of environmental reservoirs and did not require recourse to ward closure or placement of affected patients in isolation.

L'isolement septique des patients colonisés–infectés par Acinetobacter baumannii est-il totalement superflu, utile ou indispensable ?

Until 2001, the infection control department of the Besançon university hospital (France) recommended isolation precautions for all patients colonized-infected by Acinetobacter baumannii (Ab) whatever the antibiotic susceptibility of the strain. These systematic isolation procedures were given up at the beginning of 2002 since the number of colonized-infected patients remained stable from 1998 to 2001.

OBJECTIVE

The aim of this study was to evaluate the impact of this decision on the risk of Ab infection.

METHOD

Incidence rates of colonization-infections that were observed during years 2002 and 2003 were compared with expected incidence rate, based on data from 1998-2001 period. Infection control practices and antibiotics consumption were evaluated for each ward of hospitalisation. Genotyping made it possible to determine diversity of clones inside each unit and the whole hospital.

RESULTS

The expected incidence per 1000 patients-days was 0.22 in comparison with observed data in 2002, 0.34 (CI(95%) [0.28-0.42]), and in 2003, 0.53 (CI(95%) [0.45-0.63]). The expected number of Ab bloodstream infections, about two per year compared with the observed numbers in 2002 and 2003 respectively seven and 17. The number of unit with more than three cases per year increased from seven in 1999 to 18 in 2003. Antibiotics consumption did not change significantly.

CONCLUSION

Genotyping results show the importance of cross-transmission in these units. Finally, observed results suggest that some measures of isolation precautions in addition to standard precautions are needed to prevent outbreaks of Ab.