Outcomes ofAcinetobacter baumanniiInfection in Critically Ill Surgical Patients

Prevention of microbial colonization of feeding tubes in the intensive care unit

BACKGROUND

Various microorganisms which increase the mortality rate in the intensive care unit (ICU) cause microbial colonization of the nasogastric tube (NGT) and use the NGT as a reservoir.

AIM

To detect the colonization on the NGT and to determine the effect that training regarding hand hygiene, NGT management, and enteral feeding (EF) provided to ICU nurses and auxiliary service staff (ASS) has on the level of NGT colonization.

STUDY DESIGN

A quasi-experimental pre-test and post-test control design was used in this study. Microbial samples were taken from the outer and inner parts of NGT. The microorganisms were categorized as: group 1, no risk; group 2, low risk pathogenic; group 3, high-risk pathogenic group. The training was given to nurses (n = 15) and ASS (n = 7). Hand hygiene, NGT, and EF care training are provided to nurses and ASS by researchers. A total of three training sessions were scheduled to be held in 3 weeks so that all health care staff members were trained. Each session lasted 2 h in total. Patients were assigned to a group if one of the microorganisms presented on the outer surface of the patient's feeding tube and/or on the hub. The hand hygiene compliance was evaluated by direct observation according to the World Health Organization hand hygiene indications.

RESULTS

The study was conducted with 46 patients. Evaluating the patients for the presence of microorganisms before education revealed that 4.3% were in group 1, 21.8% were in group 2, and 73.9% were in group 3. After the education, evaluating the samples for the presence of microorganisms revealed that 39.1% were in group 1, 13% were in group 2, and 47.8% were in group 3. A statistically significant difference was found between the number of samples included in the groups after the participants had received training (H = 8.186; p = .017).

CONCLUSIONS

An NGT could act as a reservoir of microbial colonization and high-risk microorganisms could be on the tube. Providing training not only to nurses but also to ASS will help reduce the risk of colonization.

RELEVANCE TO CLINICAL PRACTICE

Eliminating such colonization with effective hand hygiene during NGT feeding is a cost-effective method. Providing training not only to nurses but also to ASS will help obtain the optimum benefit from patient care.

Clinical efficacy and safety of polymyxins based versus non-polymyxins based therapies in the infections caused by carbapenem-resistant Acinetobacter baumannii: a systematic review and meta-analysis

Background

The prevalence of infections due to carbapenem-resistant Acinetobacter baumannii (CRAB) is on the rise worldwide. Polymyxins are considered as last-resort drugs for CRAB infections, but there is still controversy regarding the efficacy and safety of polymyxins based therapies in CRAB infections. The present systematic review was designed to compare the efficacy and safety of polymyxins based therapies versus non-polymyxins based therapies in CRAB infections.

Methods

We performed a systematic literature search in PubMed, Embase, CINAHL, Cochrane Library, and clinicaltrials.gov to identify eligible studies reporting the clinical outcomes of patients with CRAB infections. The meta-analysis employed a random-effects model to estimate the odds ratio (OR) and standardized mean difference (SMD) with 95% confidence interval (CI). The primary outcome was 1-month mortality for any cause. We also examined clinical response, microbiological response, length of stay in hospital, and adverse events.

Results

Eleven eligible studies were analyzed (1052 patients in total), including 2 randomized clinical trials. Serious risk of bias was found in 8 out of the 11 studies. There was no statistically significant difference between polymyxins based therapies and non-polymyxins based therapies in 1-month mortality for any cause (OR, 0.95; 95% CI, 0.59 to 1.53), microbiological response (OR, 3.83; 95% CI, 0.90 to 16.29) and length of stay in hospital (SMD, 0.24; 95% CI, − 0.08 to 0.56). The pooled OR of clinical response indicated a significant difference in favor of polymyxin based therapies (OR, 1.99; 95% CI, 1.31 to 3.03). The pooled OR of adverse events showed that non-polymyxins based therapies were associated with fewer adverse events (OR, 4.32; 95% CI, 1.39 to 13.48).

Conclusion

The performance of polymyxins based therapies was better than non-polymyxin based therapies in clinical response rate and similar to non-polymyxin based therapies in terms of 1-month mortality and microbiological response in treating CRAB infections. Due to the limitations of our study, we cannot draw a firm conclusion on the optimal treatment of CRAB infections, but polymyxins would be a relatively effective treatment for CRAB infections. Adequate and well-designed large scale randomized controlled trials are required to clarify the relative efficacy of polymyxins based and non-polymyxins based therapies.

Therapeutic drug monitoring-guided high dose meropenem therapy of a multidrug resistant Acinetobacter baumannii - A case report

Background

Infections with multidrug resistant Acinetobacter baumannii in immunocompromised patients are life-threatening. Therapeutic options are rare in this context, but patients are dependent on an effective antibiotic therapy. Thus, new antibiotic strategies are deemed necessary.

Case presentation

This case report recounts the therapeutic drug monitoring-guided meropenem therapy of a 32 years old patient admitted with acute exacerbation of cystic fibrosis. Veno-venous extracorporeal membrane oxygenation was initiated on the first day of admission to the intensive care unit. The patient showed insufficient serum trough levels of meropenem despite the maximum approved dose (2g every 8h) was administered which was due to augmented renal clearance. Through continuous infusion of the same cumulative dose, target levels were reached. On day 17 of admission, the patient underwent successful double-lung-transplant surgery and extracorporeal membrane oxygenation was ended. Unfortunately, the donor's lung was colonized with a multidrug resistant Acinetobacter baumannii that was positive for OXA-23 carbapenemase. Hence a combination therapy of intravenous sulbactam, tigecycline, meropenem and inhalative colistin was established, with a known minimal inhibitory concentration for meropenem of 32 mg/l. Under continuous infusion of 8 g meropenem/day, serum levels exceeded 32 mg/l over 12 days. The patient was transferred from the intensive care unit to a general ward without any signs of infection.

Conclusions

Therapeutic drug monitoring-guided meropenem may be a sound new therapeutic option in eradicating multidrug resistant Acinetobacter and offer a novel therapeutic option in the field of personalized medicine.

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.

Clinical Characteristics of Acinetobacter baumannii Infection in Solid-Organ Transplant Recipients

OBJECTIVES

Acinetobacter baumannii, depending on the immune status of the host, may result in one of the most serious hospital infections. Infections involving A. baumannii infection have been recently rising. However, little is known about the clinical features of A. baumannii infection in solid-organ transplant recipients. We aimed to share our clinical experiences with A. baumannii infection in our transplant recipients.

MATERIALS AND METHODS

Between 2011 and 2017, 41 solid-organ transplant patients developed A. baumannii infection at Baskent University Hospital. Medical records were reviewed, and patient demographics, microbiology results, and overall outcome data were noted.

RESULTS

Of 41 solid-organ transplant patients with A. baumannii infection, 29 were male and 12 were female patients with mean age of 47.15 ± 13.24 years. Our infection rate with A. baumannii infection was 6.1%. The most common sites of infection were deep tracheal aspirate (48.8%)and bloodstream (36.6%). Onset of infection 1 year posttransplant was identified in 58.5% of recipients. Risk factors included presence of invasive procedures (56.1%) and administration of high-dose corticosteroids for rejection 1 year before infection (68.3%). Thirty-day mortality rate was 41.5% (17/41 patients) and was not associated with the infection site, microbiological cure, clinical cure, and drug resistance in our study group.

CONCLUSIONS

Acinetobacter baumannii is an important cause of hospital-acquired infection and mortality worldwide. A major problem with A. baumannii infection is delayed initiation of appropriate antibiotic treatment and the rising numbers of extensively drug-resistant organisms. Predicting the potential risk factors, especially in the already at-risk solid-organ transplant population, has an important role in patient outcomes.

Impact of empirical antimicrobial therapy on the outcome of critically ill patients with Acinetobacter bacteremia

RATIONALE:

Empirical antimicrobial therapy (EAT) for Acinetobacter infections may not be appropriate as it tends to be multidrug-resistant. This study evaluated the relationship between appropriate EAT and the outcomes of Intensive Care Unit (ICU) patients with Acinetobacter bacteremia.

METHODS:

This is a retrospective study of patients admitted to a medical-surgical ICU (2005-2010) and developed Acinetobacter bacteremia during the stay. Patients were categorized according to EAT appropriateness, defined as administration of at least one antimicrobial agent to which the Acinetobacter was susceptible before susceptibility results were known. The relation between EAT appropriateness and outcomes was evaluated.

RESULTS:

Sixty patients developed Acinetobacter bacteremia in the 6-year period (age = 50 ± 19 years; 62% males; Acute Physiology and Chronic Health Evaluation II score = 28 ± 9; 98.3% with central lines; 67% in shock and 59% mechanically ventilated) on average on day 23 of ICU and day 38 of hospital stay. All isolates were resistant to at least three of the tested antimicrobials. Appropriate EAT was administered to 60% of patients, mostly as intravenous colistin. Appropriate EAT was associated with lower ICU mortality risk (odds ratio: 0.15; 95% confidence interval: 0.03-0.96) on multivariate analysis.

CONCLUSIONS:

In this 6-year cohort, Acinetobacter bacteremia was related to multidrug-resistant strains. Appropriate EAT was associated with decreased ICU mortality risk.

Acinetobacter baumannii Extracellular OXA-58 Is Primarily and Selectively Released via Outer Membrane Vesicles after Sec-Dependent Periplasmic Translocation

Carbapenem-resistant Acinetobacter baumannii (CRAb) shelter cohabiting carbapenem-susceptible bacteria from carbapenem killing via extracellular release of carbapenem-hydrolyzing class D β-lactamases, including OXA-58. However, the mechanism of the extracellular release of OXA-58 has not been elucidated. In silico analysis predicted OXA-58 to be translocated to the periplasm via the Sec system. Using cell fractionation and Western blotting, OXA-58 with the signal peptide and C terminus deleted was not detected in the periplasmic and extracellular fractions. Overexpression of enhanced green fluorescent protein fused to the OXA-58 signal peptide led to its periplasmic translocation but not extracellular release, suggesting that OXA-58 is selectively released. The majority of the extracellular OXA-58 was associated with outer membrane vesicles (OMVs). The OMV-associated OXA-58 was detected only in a strain overexpressing OXA-58. The presence of OXA-58 in OMVs was confirmed by a carbapenem inactivation bioassay, proteomic analysis, and transmission electron microscopy. Imipenem treatment increased OMV formation and caused cell lysis, resulting in an increase in the OMV-associated and OMV-independent release of extracellular OXA-58. OMV-independent OXA-58 hydrolyzed nitrocefin more rapidly than OMV-associated OXA-58 but was more susceptible to proteinase K degradation. Rose bengal, an SecA inhibitor, inhibited the periplasmic translocation and OMV-associated release of OXA-58 and abolished the sheltering effect of CRAb. This study demonstrated that the majority of the extracellular OXA-58 is selectively released via OMVs after Sec-dependent periplasmic translocation. Addition of imipenem increased both OMV-associated and OMV-independent OXA-58, which may have different biological roles. SecA inhibitor could abolish the carbapenem-sheltering effect of CRAb.

Predictors of mortality in solid-organ transplant recipients with infections caused by Acinetobacter baumannii

Acinetobacter baumannii can cause a serious infection in solid-organ transplant (SOT) recipients, and more data on A. baumannii infection is needed. We sought to investigate the epidemiology and distribution of A. baumannii isolates in SOT recipients. We also investigated the risk factors for overall in-hospital mortality and infection-related 30-day mortality using multivariate logistic regression analysis. A double-center retrospective study of SOT recipients who were infected with A. baumannii between January 2003 and January 2015 was conducted. A total of 71 individuals developed 93 episodes of A. baumannii infection, with a mean age of 44.5 years (44.5±11.9 years). Ninety percent of recipients had nosocomial origin A. baumannii infection, with the bloodstream as the most common site of infection (32.4%). Septic shock developed in 23.9% (17 of 71) of all recipients with A. baumannii infection. Morbidity and mortality rates of A. baumannii infections were high in SOT recipients. The incidence rate of A. baumannii infection in SOT recipients was 3.9% (71 of 1,821). Overall in-hospital mortality and infection-related 30-day mortality were 53.5% (38 of 71) and 40.8% (29 of 71), respectively. Risk factors independently associated with overall in-hospital mortality were mechanical ventilation at onset of A. baumannii infection (odds ratio [OR] 6.29, 95% confidence interval [CI] 1.48–26.85; P=0.013), liver or liver–kidney transplantation (OR 15.33, 95% CI 1.82–129.18; P=0.012), and late-onset A. baumannii infection (OR 7.61, 95% CI 1.07–54.36; P=0.043). A platelet count <50,000/mm³ (OR 12.76, 95% CI 1.28–126.81; P=0.030) and mechanical ventilation at onset of A. baumannii infection (OR 189.98, 95% CI 13.23–2,728.81; P<0.001) were identified as independent risk factors for infection-related 30-day mortality. In conclusion, the morbidity and mortality rates of A. baumannii infections were high in SOT recipients. Mechanical ventilation at onset of A. baumannii infection was associated with higher overall in-hospital mortality and infection-related mortality. For overall in-hospital mortality, liver or liver–kidney transplantation and late-onset A. baumannii infection, and for infection-related mortality, thrombocytopenia were also risk factors, respectively.

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.

Detection of AmpC β-lactamases in Acinetobacter baumannii in the Xuzhou region and analysis of drug resistance

The aim of the present study was to determine the prevalence and related drug resistance of AmpC β-lactamases in Acinetobacter baumannii in tertiary-level hospitals in the Xuzhou region in China. A total of 134 clinical isolates of non-repetitive Acinetobacter baumannii were collected from different hospitals in the Xuzhou region, and multiplex polymerase chain reaction (PCR) was employed to determine the genotype of AmpC. The PCR products were purified and sequenced. The susceptibility to antibiotics was tested using the biometrics automated microbiological-assay system, VITEK-2. Amongst the 134 isolated strains, 96 strains were found to produce AmpC β-lactamases, and the positive rate was 72%, all of which carried acinetobacter-derived cephalosporinase (ADC) type AmpC resistance genes. The drug sensitivity tests indicated that the positive Acinetobacter baumannii strains were resistant to the majority of extended-spectrum β-lactam antibiotics, but were only sensitive to polymyxin. In conclusion, the incidence of AmpC enzymes in Acinetobacter baumannii strains in tertiary-level hospitals in the Xuzhou area is relatively high, and resistance to the majority of extended-spectrum β-lactam antibiotics may be related to the ADC type of AmpC.

Fulminant endocarditis and disseminated infection caused by carbapenem-resistant Acinetobacter baumannii in a renal-pancreas transplant recipient

Acinetobacter baumannii is an important cause of healthcare-associated infections, and is particularly problematic among patients who undergo organ transplantation. We describe a case of fulminant sepsis caused by carbapenem-resistant A. baumannii harboring the blaOXA-23 carbapenemase gene and belonging to international clone II. This isolate led to the death of a patient 6 days after simultaneous kidney-pancreas transplantation. Autopsy findings revealed acute mitral valve endocarditis, myocarditis, splenic and renal emboli, peritonitis, and pneumonia. This case highlights the severe nature of certain A. baumannii infections and the vulnerability of transplanted patients to the increasingly intractable "high-risk" clones of multidrug-resistant organisms.

Carbapenem-resistant Enterobacteriaceae and Acinetobacter baumannii: assessing their impact on organ transplantation

PURPOSE OF REVIEW

This review highlights the impact of carbapenem-resistant Enterobacteriaceae and carbapenem-resistant Acinetobacter baumannii on patients who have undergone organ transplantation and explores both available and potential agents to treat infections caused by these multidrug-resistant (MDR) pathogens.

RECENT FINDINGS

Few antimicrobials exist to treat carbapenem-resistant Gram-negative infections, and resistance to salvage therapies is escalating. Organ transplantation appears to be a risk factor for infections with Klebsiella pneumoniae carbapenemase-producing Enterobacteriaceae. Isolation of these MDR bacteria is increasing and may be associated with allograft failure and mortality. In the majority of cases, aminoglycosides, polymyxins, and tigecycline have been employed to treat these infections. Anecdotal successes exist but these antibiotics may be unreliable. Few novel agents are in development.

SUMMARY

Bacterial infections remain a leading cause of posttransplantation morbidity and mortality. Carbapenem resistance is a significant threat to allograft and patient survival. With few antimicrobials being developed, transplant centers may be forced to make decisions regarding surveillance, empiric antimicrobial regimens, and transplant candidacy in the setting of carriage of MDR pathogens. There is an urgent need for collaborative studies to address the clinical impact of these infections on transplantation.

Sheltering effect and indirect pathogenesis of carbapenem-resistant Acinetobacter baumannii in polymicrobial infection

The role of carbapenem-resistant Acinetobacter baumannii (CRAb) in polymicrobial infection remains elusive. Having observed the ability of CRAb to shelter other susceptible bacteria from carbapenem killing, we sought to determine the factors contributing to this sheltering effect by transforming different recombinant plasmids into recipient A. baumannii cells. The sheltering effects of CRAb were reproduced in recipient A. baumannii cells that highly expressed carbapenem-hydrolyzing class D β-lactamases (CHDLs) through their associated strong promoter. With the use of Western blot analysis and a bioassay, the highly expressed CHDLs were found to be extracellularly released and led to hydrolysis of carbapenem. The level of extracellular CHDLs increased after challenge with a higher concentration of CHDL substrates, such as carbapenem and ticarcillin. This increased CHDL may, in part, be attributed to cell lysis, as indicated by the presence of extracellular gyrase. In the planktonic condition, the sheltering effect for the cocultured susceptible bacteria might represent an indirect and passive effect of the CRAb self-defense mechanism, because coculture with the susceptible pathogen did not augment the amount of the extracellular CHDLs. Polymicrobial infection caused by CRAb and a susceptible counterpart exerted higher pathogenicity than monomicrobial infection caused by either pathogen alone in mice receiving carbapenem therapy. This study demonstrated that CHDL-producing CRAb appears to provide a sheltering effect for carbapenem-susceptible pathogens via the extracellular release of CHDLs and, by this mechanism, can enhance the pathogenesis of polymicrobial infection in the presence of carbapenem therapy.

Trauma is associated with a better prognosis in intensive care patients with Acinetobacter infections

PURPOSE

Acinetobacter baumannii has emerged as a common cause of infection in war-related trauma, civilian trauma and other surgical emergencies. The aim of this study was to determine prognostic factors especially trauma, in critically ill surgical patients with Acinetobacter spp. infection in a reference emergency ICU.

METHODS

A retrospective review of medical records was conducted for all patients admitted to the ICU who developed Acinetobacter spp. infection from January 2007 to December 2009. Bivariate and multivariate analyses were made for 36 patients. The end-point analyzed was the in-hospital mortality.

RESULTS

The initial analysis revealed a majority of young (43.6 years ± 17.1) men (92 %), trauma victims (78 %) and an in-hospital mortality of 30 %. Patients who had not suffered trauma presented with other surgical conditions and were on average older than trauma patients (57 ± 12 versus 40 ± 16 years). The overall APACHE II score average was 15.3. The ventilator-associated pneumonia was the main Acinetobacter infection diagnosed. In bivariate analysis lower Glasgow coma scale (p = 0.01) was associated with increased chance of death and being victim of trauma was a protecting factor (OR: 0.16; 95 % CI: 0.03-0.89). Receiving adequate treatment made no difference to outcome (OR: 0.55; 95 % CI: 0.05-3.15). Multivariate analysis showed that only the presence of trauma was independently associated with prognosis and was a protecting factor.

CONCLUSION

Trauma was a marker of good prognosis in emergency ICU patients with Acinetobacter spp. infection.

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.

The influence of carbapenem resistance on mortality in solid organ transplant recipients with Acinetobacter baumannii infection

Background

Infection with carbapenem-resistant Acinetobacter baumannii has been associated with high morbidity and mortality in solid organ transplant recipients. The main objective of this study was to assess the influence of carbapenem resistance and other potential risk factors on the outcome of A. baumannii infection after kidney and liver transplantation.

Methods

Retrospective study of a case series of A. baumannii infection among liver and renal transplant recipients. The primary outcome was death associated with A. baumannii infection. Multivariate logistic regression was used to assess the influence of carbapenem resistance and other covariates on the outcome.

Results

Forty-nine cases of A. baumannii infection affecting 24 kidney and 25 liver transplant recipients were studied. Eighteen cases (37%) were caused by carbapenem-resistant isolates. There were 17 (35%) deaths associated with A. baumannii infection. In unadjusted analysis, liver transplantation (p = 0.003), acquisition in intensive care unit (p = 0.001), extra-urinary site of infection (p < 0.001), mechanical ventilation (p = 0.001), use of central venous catheter (p = 0.008) and presentation with septic shock (p = 0.02) were significantly related to a higher risk of mortality associated with A. baumannii infection. The number of deaths associated with A. baumannii infection was higher among patients infected with carbapenem-resistant isolates, but the difference was not significant (p = 0.28). In multivariate analysis, the risk of A. baumannii-associated mortality was higher in patients with infection acquired in the intensive care unit (odds ratio [OR] = 34.8, p = 0.01) and on mechanical ventilation (OR = 15.2, p = 0.04). Appropriate empiric antimicrobial therapy was associated with significantly lower mortality (OR = 0.04, p = 0.03), but carbapenem resistance had no impact on it (OR = 0.73, p = 0.70).

Conclusion

These findings suggest that A. baumannii-associated mortality among liver and kidney transplant recipients is influenced by baseline clinical severity and by the early start of appropriate therapy, but not by carbapenem resistance.

Severe infection in a lung transplant recipient caused by donor-transmitted carbapenem-resistant Acinetobacter baumannii

We describe a case of proven donor transmission of carbapenem-resistant Acinetobacter baumannii, which resulted in severe infectious complications after lung transplantation. A single bla(OXA-23) positive strain, belonging to a new multilocus sequence type (ST231), was isolated from donor and recipient, who died 65 days after transplantation. This report highlights the current challenges associated with the potential transmission of multidrug-resistant infections through organ transplantation.

Comparative evaluation of intratracheal colistimethate sodium, imipenem, and meropenem in BALB/c mice with carbapenem-resistant Acinetobacter baumannii pneumonia

OBJECTIVE

The identification of the optimal agent for administration via the respiratory tract when treating pneumonia caused by carbapenem-resistant Acinetobacter baumannii (CRAB).

METHODS

A murine model of acute CRAB pneumonia was established by intratracheal (i.t.) inoculation with 2.5 × 10⁷ colony-forming units (CFU) of A. baumannii strain Ab396 plus 10% porcine mucin. After 4h the infected BALB/c mice were treated intratracheally with 25μl of either 0.85% saline (control group), colistimethate sodium (CMS) (166 666 U/kg, CMS group), imipenem/cilastatin (30/30 mg/kg, imipenem group), or meropenem (20mg/kg, meropenem group), every 8h. The therapeutic efficacy of these agents was examined.

RESULTS

A. baumannii strain Ab396 was susceptible to CMS only. However, meropenem treatment did give a significantly superior survival rate (100%) compared to treatment with imipenem (50%), CMS (33%), or saline (0%) (p<0.001 vs. the control and CMS groups, p=0.006 vs. the imipenem group, by log-rank test). Furthermore, compared to the other groups, the meropenem group demonstrated significantly more favorable results in terms of tissue penetration of the antibiotic, bacterial clearance, normalization of the wet lung-to-body weight ratio, and down-regulation of pro-inflammatory cytokine levels in the lungs.

CONCLUSIONS

Administration of meropenem via the respiratory tract proved to have the best therapeutic efficacy among the antibiotics tested when treating advanced murine CRAB pneumonia.

Rifampicin combined regimens for gram-negative infections: data from the literature

Multidrug-resistant (MDR) gram-negative bacterial infections are associated with high morbidity and mortality. Given the lack of availability of new highly effective antimicrobial drugs against multiresistant strains, combination regimens are administered that include rifampicin for its demonstrated in vitro synergism with multiple drugs. A literature review was performed of clinical studies reporting the use of rifampicin in the treatment of MDR gram-negative bacterial infections. Nineteen studies were found, including only one randomised controlled study. Data in the literature on combined therapeutic regimens with rifampicin are limited and refer mostly to uncontrolled studies. Therefore, the real clinical benefit of using rifampicin-containing therapies for the treatment of gram-negative multiresistant bacteria in terms of clinical outcome and survival rates still needs to be assessed.

Carbapenem-resistant Acinetobacter baumannii infections after organ transplantation

Multi-drug resistant (MDR) gram-negative infections among solid organ transplant (SOT) recipients have long been associated with high morbidity and mortality. Acinetobacter baumannii has emerged as a potent nosocomial pathogen with the recent acquisition of resistance to broad-spectrum beta-lactams, aminoglycosides, fluoroquinolones, and most notably, carbapenems. Despite a national rise in carbapenem-resistant A. baumannii (CRAB) infections, outcomes among SOT recipients with this emerging MDR pathogen are largely unknown. This single-center cohort is the first to describe the characteristics, complications, and outcomes among abdominal organ transplant recipients with CRAB. The current study suggests that SOT patients with CRAB suffer from prolonged hospitalization, infection with other MDR organisms, allograft dysfunction and loss, and high overall infection-related mortality.

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.

Acinetobacter baumannii infection during pregnancy and puerperium

Acinetobacter baumannii is a multidrug-resistant bacterium that is normally a commensal pathogen. This bacterium can lead to severe complications such as pneumonia, fever and septicaemia, because of limited treatment options. This case report describes a cervical A. baumannii infection during pregnancy and puerperium in a case of a patient treated in our hospital, because of insufficiency of cervix diagnosed in the 28 + 3 week of gestation. In spite of antibiotic treatment, the patient developed increasing contractions and chorioamnionitis, resulting in caesarean section in the 31st week of gestation. Moreover, although being treated with carbapenems, the patient presented postpartal with fever and septic symptoms, which could only be treated by escalation of the dosage of the given carbapenem. In conclusion, A. baumannii can lead to premature contractions and can be associated with chorioamnionitis during pregnancy. Moreover, it can also cause septic complications in the puerperium associated with long duration of hospitalisation. The management and therapy of this vaginal infection during pregnancy and puerperium is a real challenge to gynaecologists and obstetricians.

Re-emergence of colistin in today's world of multidrug-resistant organisms: personal perspectives

BACKGROUND

Infections due to multidrug-resistant Gram-negative bacteria (including Acinetobacter baumannii, Pseudomonas aeruginosa, and Klebsiella pneumoniae) are being reported with increasing frequency from various parts of the world.

OBJECTIVE

To share personal perspectives on the clinical use of colistin based on the available evidence reported in the literature as well as on knowledge obtained through our clinical experience with the use of colistin in a considerable number of patients during the past 7 years.

METHODS

Literature review and personal experience.

RESULTS/CONCLUSION

During the last decade, clinicians in several countries have resorted to colistin (polymyxin E), an antibiotic that has been shown to be clinically effective and acceptably safe for intravenous, aerosolized, and intrathecal/intraventricular administration. However, more data are needed to answer important clinical questions, including the appropriate colistin dosage, comparison of colistin monotherapy with combination therapy, and the possible preventive and therapeutic role of aerosolized colistin.