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

Patient-derived pathogenic microbe deposition enhances exposure risk in pediatric clinics

Healthcare-associated infections (HAIs) pose significant risks to pediatric patients in outpatient settings. To prevent HAIs, understanding the sources and transmission routes of pathogenic microorganisms is crucial. This study aimed to identify the sources of opportunistic bacterial pathogens (OBPs) in pediatric outpatient settings and determine their transmission routes. Furthermore, assessing the public health risks associated with the core OBPs is important. We collected 310 samples from various sites in pediatric outpatient areas and quantified the bacteria using qPCR and CFU counting. We also performed 16S rRNA gene and single-bacterial whole-genome sequencing to profile the transmission routes and antibiotic resistance characteristics of OBPs. We observed significant variations in microbial diversity and composition among sampling sites in pediatric outpatient settings, with active communication of the microbiota between linked areas. We found that the primary source of OBPs in multi-person contact areas was the hand surface, particularly in pediatric patients. Five core OBPs, Staphylococcus epidermidis, Acinetobacter baumannii, Pseudomonas aeruginosa, Streptococcus mitis, and Streptococcus oralis, were mainly derived from pediatric patients and spread into the environment. These OBPs accumulated at multi-person contact sites, resulting in high microbial diversity in these areas. Transmission tests confirmed the challenging spread of these pathogens, with S. epidermidis transferring from the patient's hand to the environment, leading to an increased abundance and emergence of related strains. More importantly, S. epidermidis isolated from pediatric patients carried more antibiotic-resistance genes. In addition, two strains of multidrug-resistant A. baumannii were isolated from both a child and a parent, confirming the transmission of the five core OBPs centered around pediatric patients and multi-person contact areas. Our results demonstrate that pediatric patients serve as a significant source of OBPs in pediatric outpatient settings. OBPs carried by pediatric patients pose a high public health risk. To effectively control HAIs, increasing hand hygiene measures in pediatric patients and enhancing the frequency of disinfection in multi-person contact areas remains crucial. By targeting these preventive measures, the spread of OBPs can be reduced, thereby mitigating the risk of HAIs in pediatric outpatient settings.

Comparative analysis of pathogen distribution in patients with fracture-related infection and periprosthetic joint infection: a retrospective study

BACKGROUND

The purpose of this study is to investigate the microbial patterns of periprosthetic joint infection (PJI) and fracture-related infection (FRI), and guide for the formulation of more accurate empirical antimicrobial regimens based on the differences in pathogen distribution.

METHODS

A comparative analysis of pathogen distribution was conducted between 153 patients (76 with PJI and 77 with FRI). Predicted analyses against isolated pathogens from two cohorts were conducted to evaluate the best expected efficacy of empirical antimicrobial regimens (imipenem + vancomycin, ciprofloxacin + vancomycin, and piperacillin/tazobactam + vancomycin).

RESULTS

Our study found significant differences in pathogen distribution between the PJI and FRI cohorts. Staphylococci (61.3% vs. 31.9%, p = 0.001) and Gram-negative bacilli (GNB, 26.7% vs. 56.4%, p < 0.001) were responsible for the majority of infections both in the PJI and FRI cohorts, and their distribution in the two cohorts showed a significant difference (p < 0.001). Multi-drug resistant organisms (MDRO) were more frequently detected in the FRI cohort (29.3% vs. 44.7%, p = 0.041), while methicillin-resistant coagulase-negative Staphylococci (MRCoNS, 26.7% vs. 8.5%, p = 0.002) and Canidia albicans (8.0% vs. 1.1%, p = 0.045) were more frequently detected in the PJI cohort. Enterobacter spp. and Acinetobacter baumannii were detected only in the FRI cohort (11.7% and 8.5%, respectively).

CONCLUSIONS

Staphylococci and GNB were responsible for the majority of infections in both PJI and FRI. Empirical antimicrobial therapy should focus on the coverage of Staphylococci in PJI and GNB in FRI, and infections caused by MDROs should be more vigilant in FRI, while the high incidence of MRCoNS in PJI should be noted, which could guide for the formulation of more accurate empirical antimicrobial regimens. Targeted therapy for FRI caused by A. baumannii and PJI caused by C. albicans needs to be further investigated. Our study reports significant differences in pathogen distribution between the two infections and provides clinical evidence for studies on the mechanism of implant-associated infection.

Prognostic Value of Sequential Organ Failure Assessment (SOFA) Score in Critically-Ill Combat-Injured Patients

Background: Infection is a frequent and serious complication after combat-related trauma. The Sequential Organ Failure Assessment (SOFA) score has been shown to have predictive value for outcomes, including sepsis and mortality, among various populations. We evaluated the prognostic ability of SOFA score in a combat-related trauma population. Methods: Combat casualties (2009-2014) admitted to Landstuhl Regional Medical Center (LRMC; Germany) intensive care unit (ICU) within 4 days post-injury followed by transition to ICUs in military hospitals in the United States were included. Multivariate logistic regression was used to determine predictive effect of selected variables and receiver operating characteristic (ROC) curve analysis was used to evaluate overall accuracy of SOFA score for infection prediction. Results: Of the 748 patients who met inclusion criteria, 436 (58%) were diagnosed with an infection (32% bloodstream, 63% skin and soft tissue, and 40% pulmonary) and were predominantly young (median 24 years) males. Penetrating trauma accounted for 95% and 86% of injuries among those with and without infections, respectively (p < 0.001). Median LRMC admission SOFA score was 7 (interquartile range [IQR]: 4-9) in patients with infections versus 4 (IQR: 2-6) in patients without infections (p < 0.001). Thirty-day mortality was 2% in both groups. On multivariate regression, LRMC SOFA score was independently associated with infection development (odds ratio: 1.2; 95% confidence interval: 1.1-1.3). The ROC curve analysis revealed an area under the curve of 0.69 for infection prediction, and 0.80 for mortality prediction. Conclusions: The SOFA scores obtained up to 4 days post-injury predict late onset infection occurrence. This study revealed that for every 1 point increase in LRMC SOFA score, the odds of having an infection increases by a factor of 1.2, controlling for other predictors. The use of SOFA score in admission assessments may assist clinicians with identifying those at higher risk of infection following combat-related trauma.

Prediction of the Risk of Hospital Deaths in Patients with Hospital-Acquired Pneumonia Caused by Multidrug-Resistant Acinetobacter baumannii Infection: A Multi-Center Study

Purpose

To predict the risk of hospital deaths in patients with hospital-acquired pneumonia (HAP) caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) infection.

Patients and Methods

A total of 366 patients who were diagnosed with HAP caused by MDR-AB infection were enrolled between January 2013 and December 2016. The sociological characteristics and clinical data of these cases were collected. Univariate and multivariate logistic analyses were used to explore the risk factors of hospital deaths before medication and after drug withdrawal. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) were utilized to assess the predictive effectiveness of the models with or without the adjustment.

Results

Hospital deaths occurred in 142 cases (38.80%). The results showed that acute physiology and chronic health evaluation II (APACHE II) and sequential organ failure assessment (SOFA) scores before medication and after drug withdrawal were associated with the risk of hospital deaths. Adjusting the covariants including the age, autoimmune disease, venous cannula, transfer of patients from other hospitals, and APACHE II score at admission, then no differences were discovered in predicting the hospital deaths between adjusted APACHE II and adjusted SOFA scores before medication (AUC: 0.808 vs 0.803, P =0.614) and after drug withdrawal (AUC: 0.876 vs 0.878, P =0.789).

Conclusion

Before medication or after drug withdrawal, the adjusted APACHE II and adjusted SOFA scores all performed well in determining the predictive effectiveness of the hospital deaths in patients with HAP caused by MDR-AB infection, indicating that the appropriate infection control may reduce the occurrence of nosocomial deaths and improve the prognosis.

Near-infrared-excited upconversion photodynamic therapy of extensively drug-resistant Acinetobacter baumannii based on lanthanide nanoparticles

Extensively drug-resistant Acinetobacter baumannii (XDR-AB) has raised considerable concerns due to its mortal damage to humans and its high transmission rate of infections in hospitals. However, current antibiotics not only show poor anti-infection effects in vivo but also frequently cause high nephrotoxicity and neurotoxicity. Herein, we report a near-infrared (NIR) light-initiated antimicrobial photodynamic therapy (aPDT) to effectively treat in vivo XDR-AB infections based on photosensitizer (PS) loaded upconversion nanoparticles (UCNPs, LiYF₄:Yb/Er). Such nanoagents feature robust NIR triggered UC luminescence and high-efficiency energy transfer from UCNPs to the loaded PS, thereby allowing NIR-triggered generation of reactive oxygen species (ROS) for destroying the bacterial cell membrane. This strategy permits a high antibacterial activity against XDR-AB, resulting in a decline of 4.72 log₁₀ in viability at a dose of 50 μg mL^-1 UCNPs-PVP-RB with 980 nm laser irradiation (1 W cm^-2). More significantly, we can achieve excellent therapeutic efficacy against deep-tissue (about 5 mm) XDR-AB infections without causing any side effects in the murine model. In brief, such NIR-activated aPDT may open up new avenues for treating various deep-tissue intractable infections.

Monoclonal IgM Antibodies Targeting Candida albicans Hyr1 Provide Cross-Kingdom Protection Against Gram-Negative Bacteria

Recent years have seen an unprecedented rise in the incidence of multidrug-resistant (MDR) Gram-negative bacteria (GNBs) such as Acinetobacter and Klebsiella species. In view of the shortage of novel drugs in the pipeline, alternative strategies to prevent, and treat infections by GNBs are urgently needed. Previously, we have reported that the Candida albicans hypha-regulated protein Hyr1 shares striking three-dimensional structural homology with cell surface proteins of Acinetobacter baumannii. Moreover, active vaccination with rHyr1p-N or passive immunization with anti-Hyr1p polyclonal antibody protects mice from Acinetobacter infection. In the present study, we use molecular modeling to guide design of monoclonal antibodies (mAbs) generated against Hyr1p and show them to bind to priority surface antigens of Acinetobacter and Klebsiella pneumoniae. The anti-Hyr1 mAbs block damage to primary endothelial cells induced by the bacteria and protect mice from lethal pulmonary infections mediated by A. baumannii or K. pneumoniae. Our current studies emphasize the potential of harnessing Hyr1p mAbs as a cross-kingdom immunotherapeutic strategy against MDR GNBs.

Acinetobacter infections and outcomes at an academic medical center: a disease of long-term care

Background. Our study aims to describe the epidemiology, microbial resistance patterns, and clinical outcomes of Acinetobacter infections at an academic university hospital. This retrospective study analyzed all inpatient clinical isolates of Acinetobacter collected at an academic medical center over 4 years. The data were obtained from an Academic tertiary referral center between January 2008 and December 2011. All consecutive inpatients during the study period who had a clinical culture positive for Acinetobacter were included in the study. Patients without medical records available for review or less than 18 years of age were excluded.

Methods. Records were reviewed to determine source of isolation, risk factors for acquisition, drug resistance patterns, and clinical outcomes. Repetitive sequence-based polymerase chain reaction of selected banked isolates was used to determine patterns of clonal spread in and among institutions during periods of higher infection rates.

Results. Four hundred eighty-seven clinical isolates of Acinetobacter were found in 212 patients (in 252 admissions). Patients with Acinetobacter infections were frequently admitted from healthcare facilities (HCFs) (59%). One hundred eighty-three of 248 (76%) initial isolates tested were resistant to meropenem. One hundred ninety-eight of 249 (79.5%) initial isolates were multidrug resistant (MDR). Factors associated with mortality included bacteremia (odds ratio [OR] = 1.93, P = .024), concomitant steroid use (OR = 2.87, P < .001), admission from a HCF (OR = 6.34, P = .004), and chronic obstructive pulmonary disease (OR = 3.17, P < .001).

Conclusions. Acinetobacter isolates at our institution are frequently MDR and are more common among those who reside in HCFs. Our findings underline the need for new strategies to prevent and treat this pathogen, including stewardship efforts in long-term care settings.

Microbiology, resistance patterns, and risk factors of mortality in ventilator-associated bacterial pneumonia in a Northern Thai tertiary-care university based general surgical intensive care unit

Background

Ventilator-associated pneumonia (VAP) occurrence, causative pathogens, and resistance patterns in surgical intensive care units (SICU) are different between Western and developing Asian countries. In Thailand, resistant organisms have progressively increased in the last decade. However, the evidence describing causes of VAP and its outcomes, especially secondary to resistant pathogens, in Asian developing countries’ SICUs is very limited. Therefore, the objective of this study was to describe the incidence, pathogen characteristics, and risk factors that impact mortality and patient survival following VAP in a tertiary Northern Thai SICU.

Methods

Between 2008 and 2012, VAP occurred in a total of 150 patients in Chiang Mai University’s general SICUs (6.3±2.8 cases per 1,000 mechanical ventilator days). The following clinical data were collected from 46 patients who died and 104 patients who survived: microbiologic results, susceptible patterns, and survival status at hospital discharge. Antimicrobial susceptibility patterns were classified as susceptible, multidrug resistant (MDR), extensively drug resistant (XDR), and pan-drug resistant (PDR). The hazard ratio (HR) was calculated for risk factor analysis.

Results

Regarding the microbiology, gram negative organisms were the major pathogens (n=142, 94.7%). The first three most common organisms were Acinetobacter baumannii (38.7% of all organisms, mortality 41.4%), Klebsiella pneumoniae (17.3%, mortality 30.8%), and Pseudomonas aeruginosa (16.7%, mortality 16%) respectively. The most common gram positive organism was Staphylococcus aureus (4.0%, mortality 50%). The median day of VAP occurrence were significantly different between the three groups (P<0.01): susceptible (day 4), MDR (day 5), and XDR (day 6.5). Only half of all VAP cases were caused by susceptible organisms. Antibiotic resistance was demonstrated by 49.3% of the gram negative organisms and 62.5% of the gram positive organisms. Extensive drug resistance was evident only in Acinetobacter baumannii (30.6%) and Pseudomonas aeruginosa (1.3%). No pan-drug resistance was found during surveillance. The significant HR risk factors were age (P=0.03), resistant organisms (P=0.04), XDR (P=0.02), and acute physiology and chronic health evaluation II score (<0.01). Acinetobacter baumannii (P=0.06) and intubation due to severe sepsis (P=0.08) demonstrated a trend toward a significant increase in the HR. On the other hand, there were significantly decreased HRs in trauma patients (P=0.01). Initial administration of appropriate antibiotic therapy had a tendency toward a significant decrease in the HR (P=0.08).

Conclusion

Gram negative organisms were the primary cause of bacterial VAP in Chiang Mai University’s general SICU. Resistant strains were present in half of all VAP cases and were associated with the day of VAP onset. Regarding risk factors, age, acute physiology, chronic health evaluation II score, resistant organisms (especially XDR), and being a non-trauma patient increased the risk of mortality.

Case-control analysis of endemic Acinetobacter baumannii bacteremia in the neonatal intensive care unit

BACKGROUND

We aimed to characterize the clinical manifestations and outcomes of patients with Acinetobacter baumannii bacteremia in the neonatal intensive care unit (NICU).

METHODS

All patients with A baumannii bacteremia in our NICU from 2004 to 2010 were reviewed. A matched case-control study was performed by comparing each case of A baumannii to 2 uninfected controls and all cases of Escherichia coli and Klebsiella bacteremia, respectively.

RESULTS

Thirty-seven cases with A baumannii bacteremia were identified. Multidrug-resistant isolate was noted in only 2 cases (5.4%), and the overall mortality rate was 8.1%. Compared with matched, uninfected controls, infants with A baumannii were more likely to have had a central vascular catheter (CVC) (P = .009), use of total parenteral nutrition (TPN) (P = .021), longer duration of ventilator use (P = .002), and hospitalization (P = .010). Compared with E coli or Klebsiella bacteremia, infants with A baumannii bacteremia had lower birth weight (median of 1,090 g vs 1,300 g, P = .044) and a higher rate of CVC and TPN use (both P < .001) at the time of infection.

CONCLUSION

A baumannii bacteremia occurs endemically or sporadically in the NICU, primarily in low-birth-weight infants on TPN use and with CVC in situ. Although A baumannii does not often cause mortality, and multidrug-resistant A baumannii is uncommon, it contributes significantly to longer hospitalization.

Risk factors for acquisition of multidrug-resistant Acinetobacter baumannii among cancer patients

BACKGROUND

Data regarding multidrug-resistant (MDR) Acinetobacter baumannii infections among cancer patients are limited.

METHODS

We conducted a case-control study to investigate the risk factors for acquisition of MDR A baumannii and the outcomes among cancer patients. Cases were inpatients with malignancy who had MDR A baumannii from any cultures between 2008 and 2011. Controls were inpatients with malignancy but no MDR A baumannii.

RESULTS

A total of 31 case patients were matched with 62 control patients. Hematologic malignancy (P = .036), need for dialysis (P = .01), admission for other reasons except elective surgery (P = .03), transfer from other health care facilities (P = .02), prolonged intensive care unit stay (P = .004), mechanical ventilation (P < .001), pressor use (P = .001), tube feeding (P < .001), transfusion (P = .009), and prior antimicrobial use (P < .001) were identified as significant risk factors in univariate analysis. Need for dialysis (odds ratio [OR], 18.23; P = .04) and prolonged intensive care unit stay (OR, 19.28; P = .01) remained significant in multivariate analysis. Lengths of stay were 28 days for the case patients and 10 days for the control patients (P = .001). The 90-day mortality rates were 41.9% and 29.0%, respectively (P = .20).

CONCLUSIONS

Acquisition of MDR A baumannii among cancer patients appears to be associated with general nosocomial infection risk factors rather than underlying malignancies.

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.

Risk factors and outcomes in patients with carbapenem-resistant Acinetobacter infection

INTRODUCTION

Acinetobacter spp. are important pathogens increasingly reported as the cause of outbreaks of nosocomial infections. The aim of our study was to identify the risk factors and assess their influence on outcomes in patients with infections caused by carbapenem-resistant Acinetobacter spp.

METHODS

A retrospective data analysis was performed to evaluate risk factors and mortality in patients with Acinetobacter spp. infections. Methods used for the statistical analysis were the Student's t-test, Chi-square test, and multivariate analysis; p < 0.05 was considered statistically significant.

RESULTS

A total of 99 patients with an Acinetobacter spp. infection were identified. Comparing patients with carbapenem-sensitive and carbapenem-resistant Acinetobacter spp. infection, significant differences were found in the mean length of intensive care unit stay (4.17 ± 3.61 vs 7.92 ± 6.74 days, p = 0.038) and mechanical ventilation (3.25 ± 2.61 and 7.07 ± 5.79 days, p = 0.009). The previous use of carbapenems (odds ratio (OR) 10.1, 95% confidence interval (CI) 1.16-87.20) and fluoroquinolones (OR 3.6, 95% CI 1.13-11.51) was independently associated with resistance to carbapenems. Of the Acinetobacter spp. strains, 94.9% (n = 94) were resistant to piperacillin-tazobactam, 88.9% (n = 88) to ceftazidime, 85.9% (n = 85) to ciprofloxacin, 83.8% (n = 83) to gentamicin, 79.8 (n = 79) to amikacin, and 48.5% (n = 48) to cefepime.

CONCLUSIONS

Intensive care unit stay before infection and source of infection in the respiratory tract were independently associated with patient mortality. Resistance to carbapenems had no impact on mortality rates. Carbapenem-resistant Acinetobacter spp. isolates had high resistance rates to other antimicrobial drugs.

Identification of Ata, a multifunctional trimeric autotransporter of Acinetobacter baumannii

Acinetobacter baumannii has recently emerged as a highly troublesome nosocomial pathogen, especially in patients in intensive care units and in those undergoing mechanical ventilation. We have identified a surface protein adhesin of A. baumannii, designated the Acinetobacter trimeric autotransporter (Ata), that contains all of the typical features of trimeric autotransporters (TA), including a long signal peptide followed by an N-terminal, surface-exposed passenger domain and a C-terminal domain encoding 4 β-strands. To demonstrate that Ata encoded a TA, we created a fusion protein in which we replaced the entire passenger domain of Ata with the epitope tag V5, which can be tracked with specific monoclonal antibodies, and demonstrated that the C-terminal 101 amino acids of Ata were capable of exporting the heterologous V5 tag to the surface of A. baumannii in a trimeric form. We found that Ata played a role in biofilm formation and bound to various extracellular matrix/basal membrane (ECM/BM) components, including collagen types I, III, IV, and V and laminin. Moreover, Ata mediated the adhesion of whole A. baumannii cells to immobilized collagen type IV and played a role in the survival of A. baumannii in a lethal model of systemic infection in immunocompetent mice. Taken together, these results reveal that Ata is a TA of A. baumannii involved in virulence, including biofilm formation, binding to ECM/BM proteins, mediating the adhesion of A. baumannii cells to collagen type IV, and contributing to the survival of A. baumannii in a mouse model of lethal infection.

Active and passive immunization protects against lethal, extreme drug resistant-Acinetobacter baumannii infection

Extreme-drug-resistant (XDR) Acinetobacter baumannii is a rapidly emerging pathogen causing infections with unacceptably high mortality rates due to inadequate available treatment. New methods to prevent and treat such infections are a critical unmet medical need. To conduct a rational vaccine discovery program, OmpA was identified as the primary target of humoral immune response after intravenous infection by A. baumannii in mice. OmpA was >99% conserved at the amino acid level across clinical isolates harvested between 1951 and 2009 from cerebrospinal fluid, blood, lung, and wound infections, including carbapenem-resistant isolates, and was ≥89% conserved among other sequenced strains, but had minimal homology to the human proteome. Vaccination of diabetic mice with recombinant OmpA (rOmpA) with aluminum hydroxide adjuvant markedly improved survival and reduced tissue bacterial burden in mice infected intravenously. Vaccination induced high titers of anti-OmpA antibodies, the levels of which correlated with survival in mice. Passive transfer with immune sera recapitulated protection. Immune sera did not enhance complement-mediated killing but did enhance opsonophagocytic killing of A. baumannii. These results define active and passive immunization strategies to prevent and treat highly lethal, XDR A. baumannii infections.

Acinetobacter baumannii infection in patients with hematologic malignancies in intensive care unit: risk factors and impact on mortality

PURPOSE

We investigated the characteristics of Acinetobacter baumannii infection in critically ill patients with hematologic malignancies.

MATERIALS AND METHODS

The prospectively collected data of patients with hematologic malignancies admitted to a medical intensive care unit of a university hospital from 2007 through 2010 were reviewed retrospectively.

RESULTS

One hundred twenty-eight patients were included in the study, among whom 35 (27%) developed 39 A baumannii infections. Pneumonia was the most common infection site of A baumannii. Presence of neutropenia, underlying hematologic malignancy, and the disease status did not affect the acquisition of the infection. Advancing age, prior exposure to aminoglycosides, central venous catheterization, and presence of nasogastric tube were the independent risk factors for the development of A baumannii infections. The mortality rate was higher in patients with A baumannii infections compared with the ones without (P = .009). However, in multivariate analysis, low Glasgow coma scale, prior immunosuppressive treatment, neutropenia, invasive mechanical ventilation, and severe sepsis were independently associated with mortality, whereas presence of A baumannii infection was not.

CONCLUSIONS

Despite the high mortality rate in critically ill patients with hematologic malignancies, presence of A baumannii infection was not an independent risk factor for mortality.

Acanthamoeba sp. promotes the survival and growth of Acinetobacter baumanii

Acinetobacter baumanii, which may be found in water, is an important emerging hospital-acquired pathogen. Free-living amoebae can be recovered from the same water networks, and it has been shown that these protozoa may support the growth of other bacteria. In this paper, we have studied potential relationships between A. baumanii and Acanthamoeba species. Two strains of A. baumanii isolated from hospital water were co-cultivated with the trophozoites or supernatants of two free-living amoebae strains: Acanthamoeba castellanii or Acanthamoeba culbertsoni. Firstly, the presence of the amoebae or their supernatants induced a major increase in A. baumanii growth, compared with controls. Secondly, A. baumanii affected only the viability of A. culbertsonii, with no effect on A. castellanii. Electron microscopy observations of the cultures investigating the bacterial location in the protozoa showed persistence of the bacteria within cyst wall even after 60 days of incubation. In our study, the survival and growth of A. baumanii could be favored by Acanthamoeba strains. Special attention should consequently be paid to the presence of free-living amoebae in hospital water systems, which can promote A. baumanii persistence.

Risk of acquiring multidrug-resistant Gram-negative bacilli from prior room occupants in the intensive care unit

The objective of this prospective cohort study was to determine whether admission to an intensive care unit (ICU) room previously occupied by a patient with multidrug-resistant (MDR) Gram-negative bacilli (GNB) increases the risk of acquiring these bacteria by subsequent patients. All patients hospitalized for >48 h were eligible. Patients with MDR GNB at ICU admission were excluded. The MDR GNB were defined as MDR Pseudomonas aeruginosa, Acinetobacter baumannii and extended spectrum β-lactamase (ESBL) -producing GNB. All patients were hospitalized in single rooms. Cleaning of ICU rooms between two patients was performed using quaternary ammonium disinfectant. Risk factors for MDR P. aeruginosa, A. baumannii and ESBL-producing GNB were determined using univariate and multivariate analysis. Five hundred and eleven consecutive patients were included; ICU-acquired MDR P. aeruginosa was diagnosed in 82 (16%) patients, A. baumannii in 57 (11%) patients, and ESBL-producing GNB in 50 (9%) patients. Independent risk factors for ICU-acquired MDR P. aeruginosa were prior occupant with MDR P. aeruginosa (OR 2.3, 95% CI 1.2-4.3, p 0.012), surgery (OR 1.9, 95% CI 1.1-3.6, p 0.024), and prior piperacillin/tazobactam use (OR 1.2, 95% CI 1.1-1.3, p 0.040). Independent risk factors for ICU-acquired A. baumannii were prior occupant with A. baumannii (OR 4.2, 95% CI 2-8.8, p <0.001), and mechanical ventilation (OR 9.3, 95% CI 1.1-83, p 0.045). Independent risk factors for ICU-acquired ESBL-producing GNB were tracheostomy (OR 2.6, 95% CI 1.1-6.5, p 0.049), and sedation (OR 6.6, 95% CI 1.1-40, p 0.041). We conclude that admission to an ICU room previously occupied by a patient with MDR P. aeruginosa or A. baumannii is an independent risk factor for acquisition of these bacteria by subsequent room occupants. This relationship was not identified for ESBL-producing GNB.

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.