Risk factors for bacteremic pneumonia and mortality (28-day mortality) in patients with Acinetobacter baumannii bacteremia

BACKGROUND

Patients infected with Acinetobacter baumannii (AB) bacteremia in hospital have high morbidity and mortality. We analyzed the clinical characteristics of pneumonia and nonpneumonia-related AB bloodstream infections (AB BSIs) and explored the possible independent risk factors for the incidence and prognosis of pneumonia-related AB BSIs.

METHODS

A retrospective monocentric observational study was performed. All 117 episodes of hospital-acquired AB bacteremia sorted into groups of pneumonia-related AB BSIs (n = 45) and nonpneumonia-related AB BSIs (n = 72) were eligible. Univariate/multivariate logistic regression analysis was used to explore the independent risk factors. The primary outcome was the antibiotic susceptibility in vitro of pneumonia-related AB BSIs group. The secondary outcome was the independent risk factor for the pneumonia-related AB BSIs group.

RESULTS

Among 117 patients with AB BSIs, the pneumonia-related group had a greater risk of multidrug resistant A. baumannii (MDRAB) infection (84.44%) and carbapenem-resistant A. baumannii (CRAB) infection (80%). Polymyxin, minocycline and amikacin had relatively high susceptibility rates (> 80%) in the nonpneumonia-related group. However, in the pneumonia-related group, only polymyxin had a drug susceptibility rate of over 80%. Univariate analysis showed that survival time (day), CRAB, MDRAB, length of hospital stay prior to culture, length of ICU stay prior to culture, immunocompromised status, antibiotics used prior to culture (n > = 3 types), endotracheal tube, fiberoptic bronchoscopy, PITT, SOFA and invasive interventions (n > = 3 types) were associated with pneumonia-related AB bacteremia. The multivariate logistic regression analysis revealed that recent surgery (within 1 mo) [P = 0.043; 0.306 (0.098-0.962)] and invasive interventions (n > = 3 types) [P = 0.021; 0.072 (0.008-0.671)] were independent risk factors related to pneumonia-related AB bacteremia. Multivariate logistic regression analysis revealed that length of ICU stay prior to culture [P = 0.009; 0.959 (0.930-0.990)] and recent surgery (within 1 mo) [P = 0.004; 0.260 (0.105-0.646)] were independent risk factors for mortality in patients with pneumonia-related AB bacteremia. The Kaplan‒Meier curve and the timing test showed that patients with pneumonia-related AB bacteremia had shorter survival time compared to those with nonpneumonia-related AB bacteremia.

CONCLUSIONS

Our study found that A. baumannii had a high rate of antibiotic resistance in vitro in the pneumonia-related bacteremia group, and was only sensitive to polymyxin. Recent surgery was a significantly independent predictor in patients with pneumonia-related AB bacteremia.

Effect of Delays in Concordant Antibiotic Treatment on Mortality in Patients With Hospital-Acquired Acinetobacter Species Bacteremia: Emulating a Target Randomized Trial With a 13-Year Retrospective Cohort

Delays in treating bacteremias with antibiotics to which the causative organism is susceptible are expected to adversely affect patient outcomes. Quantifying the impact of such delays to concordant treatment is important for decision-making about interventions to reduce the delays and for quantifying the burden of disease due to antimicrobial resistance. There are, however, potentially important biases to be addressed, including immortal time bias. We aimed to estimate the impact of delays in appropriate antibiotic treatment of patients with Acinetobacter species hospital-acquired bacteremia in Thailand on 30-day mortality by emulating a target trial using retrospective cohort data from Sunpasitthiprasong Hospital in 2003–2015. For each day, we defined treatment as concordant if the isolated organism was susceptible to at least 1 antibiotic given. Among 1,203 patients with Acinetobacter species hospital-acquired bacteremia, 682 had 1 or more days of delays to concordant treatment. Surprisingly, crude 30-day mortality was lower in patients with delays of ≥3 days compared with those who had 1–2 days of delays. Accounting for confounders and immortal time bias resolved this paradox. Emulating a target trial, we found that these delays were associated with an absolute increase in expected 30-day mortality of 6.6% (95% confidence interval: 0.2, 13.0), from 33.8% to 40.4%.

Bactericidal Permeability Increasing Protein Deficiency Aggravates Acute Colitis in Mice by Increasing the Serum Levels of Lipopolysaccharide

Objective

The objective of this study was to understand the role of bactericidal permeability increasing protein (BPI) in the pathogenesis of experimental murine colitis.

Methods

We used the Cre-LoxP system to generate BPI knockout (BPI KO) mice. Acute colitis was induced in BPI KO mice and wild-type (WT) mice by subjecting the mice to 5% dextran sulfate sodium (DSS). Mice were observed for symptoms of experimental colitis. The survival of BPI KO mice to infection with Acinetobacter baumannii, a gram-negative bacterium, was also assessed.

Results

Southern blot, RT-PCR, and western blot results showed that the 2nd and 3rd exons of the murine Bpi gene were knocked out systemically, confirming successful construction of the BPI KO mouse. BPI KO mice subjected to DSS showed increased symptoms of experimental colitis, increased colonic mucosal damage, increased epithelial permeability, elevated levels of serum LPS, and a disrupted fecal microbiome as compared with WT mice. Furthermore, BPI KO mice challenged intraperitoneally with A. baumannii died sooner than WT mice, and the total number of bacteria in the abdominal cavity, spleen, and liver was increased in BPI KO mice as compared to WT mice.

Conclusions

We successfully generated BPI KO mice. The BPI KO mice developed worse colitis than WT mice by increased colitis symptoms and colonic mucosal damage, elevated levels of serum LPS, and a disrupted microbiome. BPI could be a potential target for treatment of ulcerative colitis in humans.

Excess mortality due to pandrug-resistant Acinetobacter baumannii infections in hospitalized patients

BACKGROUND

Pandrug-resistant Acinetobacter baumannii (PDRAB) is increasingly being reported as a nosocomial pathogen worldwide, but determining its clinical impact is challenging.

AIM

To assess the spectrum of excess mortality attributable to PDRAB infection in acute care settings.

METHODS

This four-year cohort study was conducted in a tertiary-care referral hospital in Greece to estimate excess in-hospital mortality due to PDRAB infection by comparing patients infected to those colonized with PDRAB by means of competing risks survival analysis.

FINDINGS

The study cohort comprised 91 patients (median age: 67 years; 77% men). For most patients, PDRAB was first isolated in the intensive care unit (ICU) (N = 51; 57%) or following ICU discharge (N = 26; 29%). Overall in-hospital mortality was 68% (95% confidence interval (CI): 57.5-77.5%). PDRAB-infected patients (N = 62; 68%) and PDRAB-colonized patients (N = 29; 32%) had similar baseline characteristics, but the absolute excess risk of 30-day mortality in infected patients compared to colonized patients was 34% (95% CI: 14-54%). Multivariable competing risks regression showed that PDRAB infection significantly increased the daily hazard of 30-day in-hospital death (cause-specific hazard ratio (csHR): 3.10; 95% CI: 1.33-7.21) while simultaneously decreasing the daily rate of discharge (csHR: 0.24; 95% CI: 0.08-0.74), thereby leading to longer hospitalization. Stronger effects were observed for bloodstream infections.

CONCLUSION

New effective antimicrobials would be expected to prevent mortality in one of every three patients treated for PDRAB infection and reduce their length of hospitalization. However, available therapeutic options remain extremely limited and emphasis on preventing healthcare-associated transmission of PDRAB is ever more important.

Treatment efficacy of tigecycline in comparison to cefoperazone/ sulbactam alone or in combination therapy for carbapenenm-resistant Acinetobacter baumannii infections

Tigecycline (TGC) and cefoperazone/sulbactam (CPS) both have been shown good in vitro activity against carbapenem-resistant Acinetobacter baumannii (CRAB) isolates. We aim to compare the efficacy of TGC versus CPS for CRAB infections. We conducted a retrospective cohort study of patients with CRAB at a single center in China from 2013 to 2015. Outcomes comprised in-hospital mortality, clinical and microbiological response. The method of inverse probability of treatment weighting and multivariable logistic regression analysis incorporated with propensity score were employed to estimate the effect of treatment groups. There were 130 subjects included in our study. The patients in TGC, CPS and TGC plus CPS combination group were 42, 66, and 22, respectively. After adjustment, in-hospital mortality was lower in CPS group than TGC group (weighted OR 0.173; 95% CI 0.06-0.497; P=0.001) but without differences in clinical success and microbiological eradication (P>0.05). TGC monotherapy had a similar outcome with TGC plus CPS combination group. This is the first study comparing the efficacy of tigecycline and cefoperazone/sulbactam for CRAB infections. Cefoperazone/sulbactam appears to be more efficacious than tigecycline during treatment.

Mortality from acinetobacter infections as compared to other infections among critically ill patients in South India: A prospective cohort study

Background

Acinetobacter baumannii has become a common pathogen causing hospital-acquired infections (HAIs). Although acquiring any nosocomial infection is associated with increased mortality, we do not know if the acquisition of Acinetobacter infection confers a worse prognosis as compared to non-Acinetobacter-related HAI. The aim of the current study is to compare the clinical outcomes of ventilator-associated pneumonia (VAP) and central line associated blood stream infections (CLABSIs) caused by A. baumannii with those caused by other bacterial pathogens.

Materials and Methods

This prospective cohort study was conducted among critically ill adults admitted to a tertiary care hospital in South India from January 2013 to June 2014. We enrolled patients who developed new-onset fever ≥48 h after admission and fulfilled pre-specified criteria for VAP or CLABSI. The patients were followed up until the primary outcomes of death or hospital discharge.

Results

During the study period, 4047 patients were admitted in the intensive care units, among which 129 eligible HAI events were analysed. Of these, 95 (73.6%) were VAP, 34 (26.4%) were CLABSI, 78 (60.4%) were A. baumannii-related HAI (AR-HAI) and 51 (39.6%) were non-A. baumannii-related HAI (NAR-HAI). Mortality among AR-HAI was 57.6% compared to 39.2% in NAR-HAI (P = 0.04) which on multivariate analysis did not achieve statistical significance, although the trend persisted (odds ratio [OR] = 4.2, 95% confidence interval [CI]: 0.95-18.4, P = 0.06). The acquisition of VAP due to A. baumannii was associated with poor ventilator outcomes even after adjusting for confounders (adjusted OR = 3.5, 95% CI: 1.07-11.6, P = 0.04).

Conclusion

In our cohort of critically ill adults with VAP and CLABSI, AR-HAI was associated with poor ventilator outcomes and a trend towards higher mortality. These findings add to the evidence suggesting that A. baumannii is a dangerous pathogen, perhaps even more so than others.

Incidence of infections caused by carbapenem-resistant Acinetobacter baumannii

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CR-Ab) has become a worrying health care problem, mainly in developing countries, such as Brazil. The objective was to investigate the prevalence and prognostic factors for CR-Ab infections at a Brazilian university hospital and examine the impact of inappropriate antimicrobial therapy on patient outcome.

METHODS

A retrospective study on hospitalized patients with CR-Ab infections was carried out from January 2013 to December 2017. An epidemiologic analysis was carried out to determine the frequency of infections, the epidemiologic indicators by year, the risk factors for 30-day mortality, and the impact of inappropriate therapy.

RESULTS

A total of 489 patients were included in the study. A rate of 0.7 per 1,000 patient-day CR-Ab infections was observed, mostly in the lungs (54.7%), and predominantly in the adult intensive care unit. The occurrence of infections by CR-Ab per 1,000 patient-days in November 2014 exceeded the established control limit, confirming an outbreak.

CONCLUSIONS

The prevalence of CR-Ab increased in the investigated hospital, passing to an endemic pathogen with a direct impact on mortality and the control of these strains.

PgaB is a Putative Marker for Early Predicting the Virulence of Acinetobacter baumannii Clinical Isolates

BACKGROUND

Acinetobacter baumannii (Ab) is an important opportunistic pathogen in a hospital setting. The virulence varies among different clinical isolates, which can be measured by cytotoxicity assay or Galleria mellonella killing assay. However, these measurements are not suitable for routine clinical laboratory application. Thus, a putative marker for early prediction and intervention of these virulent isolates is desirable.

METHODS

PgaB is part of the pgaABCD cluster, which is considered to be essential for the biofilm formation and pathogenesis of Ab. Sixty-five non-repetitive Ab clinical isolates were randomly collected from respiratory tract specimens in our hospital, which were pgaB positive as determined by PCR. The mRNA expression level of pgaB was measured by quantitative real-time PCR, with Taqman probe targeting the conserved region of pgaB. 16S rRNA was used as an internal control. The virulence was determined by the ability to kill A549 human lung epithelial cells with different MOIs and different time points. The virulence was also determined by Galleria mellonella killing assay and analyzed by Kaplan-Meier survival analysis. The statistical analysis was performed with SPSS 13.0 and Graphpad Prism 5.0.

RESULTS

Sixty-five isolates were divided into pgaB high and low expression groups by the values of adjusted pgaB expression, the median values of which were 25.81 ± 6.34 (n = 41) and 4.16 ± 2.82 (n = 24), respectively (p < 0.05). The Ab virulence determined by cytotoxicity assay was significantly higher in the pgaB high expression group than in the low expression group (MOI = 100, incubated for 18 hours, p < 0.05). The killing rate of Galleria mellonella was significantly higher in the pgaB high expression group than in the low expression group (inoculum of 106 CFU/larva at 37°C, p < 0.05), with the median survival time of 40 hours and 75 hours, respectively.

CONCLUSIONS

The adjusted expression level of pgaB was in agreement with the virulence of Ab in cytotoxicity assays and Galleria mellonella killing assay, thus it may be used potentially as a putative marker for early prediction of the virulence of Ab clinical isolates.

Risk factors for acquisition and mortality of multidrug-resistant Acinetobacter baumannii bacteremia: A retrospective study from a Chinese hospital

Bloodstream infection caused by Acinetobacter baumannii has become a major clinical concern, especially multidrug-resistant A baumannii (MDRAB). The aim of this study was to identify the risk factors of nosocomial acquired MDRAB bacteremia and to determine the risk factors related to the mortality of patients with MDRAB bacteremia. Patients with nosocomial acquired A baumannii bacteremia were enrolled between January, 2013 and December, 2017 at the First Affiliated Hospital, School of Medicine, Zhejiang University. Medical records were reviewed, and the clinical and microbial characteristics were collected. Among the 338 patients suffering from A baumannii bacteremia, 274 patients were infected with MDRAB bacteremia. Bacteremia-related mortality was 46.4% for the overall sample; 56.2% for MDRAB bacteremia patients, 4.7% for non-MDRAB bacteremia patients. The identified risk factors for developing MDRAB bacteremia were previous exposure to carbapenems [odds ratio (OR) 5.78, P = .005] and penicillins+β-lactamase inhibitors (OR 4.29, P = .009). Primary bacteremia tended to develop non-MDR bacteremia (OR 0.10, P = .002). The risk factors for MDRAB bacteremia-related mortality were old age (OR 1.02, P = .036), a high Pitt bacteremia score (OR 1.32, P < .001), bacteremia occurring after severe pneumonia (OR 8.66, P < .001), while catheter-related infection (OR 0.47, P = .049) and operations for treating infection (OR 0.51, P = .043) may have a better outcome. Patients with MDRAB had a higher mortality rate. Patients with previous carbapenems and penicillins+β-lactamase inhibitor exposure are at an increased risk of MDRAB bacteremia, whereas patients with primary bacteremia tended to develop non-MDR bacteremia. The risk factors for MDRAB bacteremia-related mortality were old age, a high Pitt bacteremia score, and bacteremia occurring after severe pneumonia, whereas catheter-related infection and operations for the treatment of infection may have a better outcome.

A high mortality rate associated with multidrug-resistant Acinetobacter baumannii ST79 and ST25 carrying OXA-23 in a Brazilian intensive care unit

The global spread of carbapenem-resistant Acinetobacter baumannii (A. baumannii) strains has restricted the therapeutic options available to treat infections due to this pathogen. Understanding the prevalence of such infections and the underlying genetic mechanisms of resistance may help in the implementation of adequate measures to control and prevent acquisition of nosocomial infections, especially in an intensive care unit setting. This study describes the molecular characteristics and risk factors associated with OXA-23-producing A. baumannii infections. A case-control study was undertaken from September/2013 to April/2015. Acquisition of OXA-23-producing A. baumannii was found to be associated with the use of nasogastric tubes, haemodialysis, and the use of cephalosporins. These isolates were only susceptible to amikacin, gentamicin, tigecycline, and colistin, and contained the ISAba1 insertion sequence upstream ofbla_OXA-23 and bla_OXA-51 genes. Twenty-six OXA-23-producing A. baumannii strains belonged to the ST79 (CC79) clonal group,and patients infected or colonised by these isolates had a higher mortality rate (34.6%). In conclusion, this study showed a dissemination of OXA-23-producing A. baumannii strains that was associated with several healthcare-related risk factors and high mortality rates among intensive care unit patients.

IL-33 Treatment Attenuates the Systemic Inflammation Reaction in Acinetobacter baumannii Pneumonia by Suppressing TLR4/NF-κB Signaling

Interleukin (IL)-33 treatment has been reported to reduce mortality in a rat model of sepsis, and the present study aimed to determine whether this effect of IL-33 is achieved through a reduction in the systemic inflammatory response in Acinetobacter baumannii pneumonia. After induction of pneumonia, rats were treated with normal saline or IL-33, and mortality over 5 days was recorded. Inflammation within lung tissues was evaluated by hematoxylin and eosin staining as well as measurement of the concentrations of IL-8 and tumor necrosis factor alpha (TNF-α) in the bronchoalveolar lavage fluid (BALF) and plasma by enzyme-linked immunosorbent assay. In addition, the expression of Toll-like receptor 4 (TLR4), ST2, and nuclear factor kappa B (NF-κB) in rat lung tissues was assessed by western blotting. The result showed that the mortality rate and systemic inflammation were significantly increased in rats upon infection with A. baumannii, as evidenced by significant increases in the IL-8 and TNF-α levels in BALF and plasma as well as increased NF-κB activity and TLR4 expression in rat lung tissues. Importantly, IL-33 (1 μg/kg) treatment significantly decreased mortality and pulmonary inflammation in A. baumannii-infected rats. Moreover, IL-33 treatment suppressed the elevation of IL-8 and TNF-α levels and inhibited TLR4 expression and NF-κB activation. Overall, these results suggest that IL-33 may decrease the mortality and inhibit the systematic inflammatory response associated with A. baumannii pneumonia by suppressing TLR4/NF-κB signaling.

Natural prognosis of carbapenem-resistant Acinetobacter baumannii bacteremia in patients who did not receive appropriate antibiotic treatment: A retrospective multicenter study in Korea

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is a major issues in current era. The aim of study was to investigate the natural prognosis and prognostic factors associated with 28-day mortality in patients with CRAB bacteremia who were not receiving appropriate antibiotic treatment.Adult patients with CRAB bacteremia were retrospectively identified between April 2012 and March 2015 at 5 tertiary hospitals in Republic of Korea. Patients who were transferred to another hospital within 28 days of onset of bacteremia and who receive appropriate antibiotics more than 48 hours were excluded. We investigated prognostic factors associated with 28-day mortality in patients with CRAB bacteremia without appropriate antibiotic treatment.Of enrolled 205 patients, 143 (69.8%) patients died within 28 days after blood culture. Of patients with 28-day mortality, 88.9% (127/143) of patients died within 5 days. Of 78 patients who survived more than 5 days, the 28-day mortality was 20.5% (16/78). Diabetes mellitus (adjusted odds ratio [aOR] 3.81, 95% confidence interval [95% CI] 1.19-12.20), immunocompromised (aOR 8.72, 95% CI 2.62-29.70), sequential organ failure assessment (SOFA) ≥ 10 (aOR 13.87, 95% CI 3.70-51.96), vasopressor use (aOR 7.03, 95% CI 1.79-27.60), and pneumonia (aOR 4.44, 95% CI 1.67-11.78) were found to be the factors independently associated with the 28-day mortality.The 28-day mortality in patients with CRAB bacteremia without appropriate treatment was high, although some patients could survive. Severity and underlying conditions were important prognostic factors in patients with CRAB bacteremia.

Treatment outcomes of patients with non-bacteremic pneumonia caused by extensively drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii complex isolates: Is there any benefit of adding tigecycline to aerosolized colistimethate sodium?

Few therapeutic options exist for various infections caused by extensively drug-resistant Acinetobacter calcoaceticus-Acinetobacter baumannii (XDR-Acb) complex isolates, including pneumonia. This study investigated the clinical efficacy between aerosolized colistimethate sodium (AS-CMS, 2 million units thrice a day) treatment alone or in combination with standard-dose tigecycline (TGC) in patients with non-bacteremic pneumonia due to XDR-Acb, and explored the factors influencing patients' 30-day mortality.A 1:1 case (n = 106; receiving TGC plus AS-CMS) control (receiving AS-CMS alone with matching scores) observational study was conducted among adult patients with non-bacteremic XDR-Acb complex pneumonia in a Taiwanese medical center from January 2014 through December 2016. The clinically relevant data were retrospectively recorded. The primary endpoint was 30-day case fatality. Secondary endpoints investigated that if the co-morbidities, XDR-A. baumannii as a pneumonic pathogen, therapy-related factors, or airway colonization with colistin-resistant Acb negatively influenced the 14-day clinical condition of enrolled patients.A higher 30-day mortality rate was noted among the group receiving combination therapy (34.0% vs 22.6%; P = .17). The ≥7-day AS-CMS therapy successfully eradicated > 90% of airway XDR-Acb isolates. Nevertheless, follow-up sputum specimens from 10 (6.4% [10/156]) patients were colonized with colistin-resistant Acb isolates. After the conditional factors were adjusted by multivariate logistic analysis, the only factor independently predicting the 30-day case-fatality was the failure of treating XDR-Acb pneumonia at 14 days (adjusted odds ratio [aOR] = 38.2; 95% confidence interval [CI] = 9.96-142.29; P < .001). Cox proportional regression analysis found that chronic obstructive pulmonary disease (COPD) (adjusted hazard ratio [aHR] = 2.08; 95% CI = 1.05-4.10; P = .035), chronic renal failure (aHR = 3.00; 95% CI = 1.52-5.90; P = .002), non-invasive ventilation use (aHR = 2.68; 95% CI = 1.37-5.25; P = .004), and lack of TGC therapy (aHR = 0.52; 95% CI = 0.27-1.00; P = .049) adversely influenced the 14-day clinical outcomes. Conversely, the emergence of colistin-resistant Acb isolates in the follow-up sputum samples was not statistically significantly associated with curing or improving XDR-Acb pneumonia.In conclusion, aggressive pulmonary hygiene care, the addition of TGC, and corticosteroid dose tapering were beneficial in improving the 14-day patients' outcomes.

Intravenous colistin combination antimicrobial treatment vs. monotherapy: a systematic review and meta-analysis

BACKGROUND

To evaluate whether intravenous colistin in combination with other antibiotics (IVCC) is associated with lower mortality compared with intravenous colistin monotherapy (IVCM), and to identify factors influencing study outcomes.

METHODS

PubMed and Scopus were searched up to November 2016. Studies were included if they evaluated adult patients with multi-drug-resistant (MDR) or extensively-drug-resistant Gram-negative infections, and reported comparative mortality data (adjusted and unadjusted) for patients receiving IVCC vs. IVCM. Random effects meta-analyses were performed.

FINDINGS

Thirty-two studies (29 observational, three randomized) were included. The overall quality of data was low to very low, and studies were characterized by the lack of adjusted data. The majority of studies were not designed to evaluate the outcome of the meta-analysis, and focused mainly on infections due to Acinetobacter baumannii and Klebsiella pneumoniae. Colistin was administered at variable doses, with or without a loading dose, and in combination with several antibiotics. Overall, IVCC was not associated with lower mortality than IVCM [32 studies, 2328 patients, risk ratio (RR) 0.91, 95% confidence interval (CI) 0.81-1.02, I2 8%]. A significant difference was observed in favour of IVCC when high-dose (>6 million international units) colistin was used (RR 0.80, 95% CI 0.69-0.93), in studies conducted in Asia (RR 0.82, 95% CI 0.71-0.95), in patients with bacteraemia (RR 0.75, 95% CI 0.57-0.98) and in patients with acinetobacter infections (RR 0.88, 95% CI 0.78-1.00).

INTERPRETATION

Overall, low-quality data suggest that IVCC did not lower mortality in patients with MDR Gram-negative infections. However, there is some evidence for a benefit observed with high intravenous doses of colistin.

Impact of reduced tigecycline susceptibility on clinical outcomes of Acinetobacter bacteremia

The higher 14-day mortality rate for patients with Acinetobacter bacteremia receiving tigecycline appropriately compared to other appropriate antibiotics (36.4% versus 14.2%, P = 0.028) was due to the poor effect of tigecycline for isolates with a minimum inhibitory concentration of 2 μg/mL (63.6% of 11 versus 14.2% of 127, P = 0.001).

Should we treat patients with only one set of positive blood cultures for extensively drug-resistant Acinetobacter baumannii the same as multiple sets?

Acinetobacter species are not considered skin commensals and under-treatment is an overriding concern when caring for critically-ill patients who are mostly at risk of extensively drug-resistant Acinetobacter baumannii (XDRAB) infections. Hence even a single blood culture yielding XDRAB will tend to prompt intervention. However, field observations suggest that patients with single-positive blood cultures had milder disease and were more likely to be recruited in interventional studies than those with multiple-positive blood cultures, yet no distinction is made in current clinical or trial recruitment practices. To our knowledge, this is the first study to compare the clinical characteristics and outcomes of patients with single-positive versus multiple-positive blood cultures for XDRAB. In this multicenter prospective cohort study of XDRAB bacteremic patients from July 2010 to June 2015, only patients with at least two simultaneously drawn blood cultures were included. The patients were classified as having single-positive or multiple-positive blood cultures according to the number of positive blood cultures yielding XDRAB. The primary end-point was the 28-day mortality. Of a total of 155 patients enrolled, 69 had a single-positive and 86 had multiple-positive blood cultures. Leukopenia (37.2% vs. 16.2%; P = 0.004), thrombocytopenia (56.0% vs. 26.5%; P < 0.001), higher Pitt bacteremia scores (6.6 vs. 5.5, P = 0.03) and higher 28-day mortality rates (70.9% vs. 43.5%; P = 0.001) distinguished patients with multiple-positive from those with single-positive cultures. Multivariate logistic regression showed that multi-positivity independently predicted 28-day mortality (adjusted odds ratio, 2.34; 95% confidence interval (CI), 1.03–5.28; P = 0.04) and the Cox regression confirmed that multi-positivity (adjusted hazard ratio, 1.80; 95% CI, 1.13–2.85; P = 0.01) predicted rapid mortality. Patients with multiple versus single positive blood cultures yielding XDRAB had greater morbidity and mortality. Investigators and clinicians should be aware that the blood culture positivity rate impacts outcomes of XDRAB bacteremia.

Mortality In Patients With Respiratory And Nonrespiratory Carbapenem Resistant-Multidrug Resistant Acinetobacter Infections

BACKGROUND

Mortality from carbapenem-multi-drug resistant Acinetobacter infections may vary according to site of infection. The objective of this study was to compare mortality in respiratory vs. non-respiratory infection with Carbapenem-Multi-drug Resistant Acinetobacter (C-MRAB).

METHODS

We conducted a prospective cohort study to compare mortality rate in patients with respiratory vs. nonrespiratory infection (n=30 each).

RESULTS

Results showed that mortality was 40% in the respiratory group compared to 23% in non-respiratory group; the difference was not statistically significant (p=0.165, RR=1.71, CI=0.73-3.75). There was a significantly higher prior admission rate in patients with respiratory infection (p=0.028). Logistic regression did not reveal any modifier effect from other variables.

CONCLUSIONS

This study showed no significant difference in mortality in patients with carbapenem-multi-drug resistant acinetobacter respiratory vs. non-respiratory infections.

Polymyxin B and Doxycycline Use in Patients with Multidrug-Resistant Acinetobacter baumannii Infections in the Intensive Care Unit

Background:

Multidrug-resistant Acinetobacter baumannii (MDR-Ab) has emerged as an increasingly problematic cause of hospital-acquired infections in the intensive care unit (ICU). MDR-Ab is resistant to most standard antimicrobials but often retains susceptibility to polymyxin B and doxycycline.

Objective:

To evaluate the efficacy and toxicity of polymyxin B and doxycycline in the treatment of MDR-Ab infections.

Methods:

A retrospective chart review was conducted between March 2002 and May 2005 in patients who received doxycycline or polymyxin B for treatment of MDR-Ab infections in ICUs within Grady Memorial Hospital, Atlanta, GA.

Results:

Thirty-seven patients with MDR-Ab infections were treated with polymyxin B or doxycycline. Median age was 41 years and median ICU length of stay was 18 days prior to acquisition of MDR-Ab. Clinical cure was observed in 22 of 29 (76%) evaluable patients treated with polymyxin B and 2 of 4 (50%) patients treated with doxycycline. In patients with follow-up cultures, microbiological cure was observed in 17 of 21 (81%) patients treated with polymyxin B and 2 of 3 (67%) patients treated with doxycycline. Nephrotoxicity developed in 21% (7 of 33) of patients who received polymyxin B. Neurotoxicity was observed in 2 (6%) patients who received polymyxin B. No adverse reactions were observed with doxycycline. Overall, crude mortality was 27% (9 of 33) and 75% (3 of 4) among those who received polymyxin B and doxycycline, respectively. Three (9%) deaths were attributed to polymyxin B treatment failure, and no deaths were attributed to doxycycline treatment failure.

Conclusions:

Polymyxin B was effectively used to treat a substantial proportion of critically ill patients with MDR-Ab infection and was associated with a similar rate of nephrotoxicity as previously reported. Doxycycline monotherapy was used in a limited number of patients for the treatment of MDR-Ab; further evaluation of its efficacy in larger numbers of patients is warranted.

Predictors of mortality in patients with extensively drug-resistant Acinetobacter baumannii pneumonia receiving colistin therapy

The ratio of the area under the free (unbound) concentration-time curve to minimum inhibitory concentration (fAUC/MIC) was proposed to be the pharmacokinetic/pharmacodynamic index most strongly linked to the antibacterial effect of colistin against Acinetobacter baumannii. A retrospective study of patients who received colistin to treat pneumonia caused by extensively drug-resistant (XDR) A. baumannii over a 4-year period was performed to assess the impact of the colistin MIC on mortality. A total of 227 patients were included in the analysis. The 7-day and 14-day mortality rates of patients with XDR A. baumannii pneumonia receiving colistin therapy were 15.0% and 23.8%, respectively. In the multivariate analysis, Acute Physiology and Chronic Health Evaluation (APACHE) II score, days from index culture to first dose of colistin, underlying tumour and septic shock at presentation were independent predictors of mortality in patients with XDR A. baumannii pneumonia receiving colistin therapy. In the univariate analysis, the colistin dose based on ideal body weight (IBW) correlated with patient outcome. Therefore, the use of IBW appeared to be more appropriate to calculate the colistin dosage. In addition, these results highlight the clinical significance of colistin MIC in patients with XDR A. baumannii pneumonia receiving colistin therapy. Although MICs were in the 'susceptible' range, patients infected with isolates with high colistin MICs showed a poorer clinical response rate than patients infected with isolates with low colistin MICs. Further clinical studies are needed to evaluate the roles of colistin MIC for predicting mortality in XDR A. baumannii pneumonia with a high colistin MIC.

Blood stream infections caused by Acinetobacter baumannii group in Japan - Epidemiological and clinical investigation

Acinetobacter calcoaceticus-Acinetobacter baumannii complex, especially A. baumannii, Acinetobacter pittii and Acinetobacter nosocomialis, constitutes an important group of nosocomial pathogens; however, epidemiological or clinical characteristics and prognosis is limited in Japan. From 2009 to 2013, 47 blood stream infection cases resulting from A. baumannii group were reviewed at the National Defense Medical College, an 800-bed tertiary hospital. To determine the genospecies, further comparative nucleotide sequence analyses of the RNA polymerase b-subunit (rpoB) gene were performed. Sequence analysis of rpoB gene showed that 25 (49.0%), 17 (33.3%) and 5 (9.8%) cases were caused by A. baumannii, A. pittii and A. nosocomialis, respectively. The 30-day and in-hospital mortality rates of A. baumannii were 8.5% and 25.5%, respectively, and there were no significant differences between Acinetobacter species. Clinical characteristics were statistically insignificant. Multidrug-resistant Acinetobacter species were detected in 3 cases (5.9%) with same pulsed-field gel electrophoresis (PFGE) pattern and A. baumannii was less susceptible to amikacin and levofloxacin. In this study, the mortality and clinical characteristics were similar among A. baumannii group isolate cases despite some showing drug resistance. However, identification of Acinetobacter species helps to initiate appropriate antibiotic therapy in earlier treatment phase, because A. baumannii shows some drug resistance.

Risk Factors and Clinical Outcomes for Patients With Acinetobacter baumannii Bacteremia

Acinetobacter (A.) baumannii, an opportunistic nosocomial pathogen that can cause significant morbidity and mortality, has emerged as a worldwide problem. This study aimed to analyze the clinical features and outcomes of patients with A. baumannii bacteremia and determine the factors influencing survival by using 14-day mortality as the primary endpoint. A 6-year retrospective study of 122 cases with monomicrobial A. baumannii bacteremia was conducted in Chinese People's Liberation Army (PLA) General Hospital from January 2008 to April 2014. Predictors of 14-day mortality were identified by logistic regression analysis. The overall 14-day mortality rate was 40.2% (49 of 122 patients). Multivariable analysis revealed that independent predictors of 14-day mortality included severity of illness defined by Pitt Bacteremia Score (PBS) (odds ratio [OR], 0.46; 95% confidence interval [CI], 0.340-0.619; P < 0.001), neutropenia (OR, 18.02; 95% CI, 1.667-194.67; P = 0.017), and malignancy (OR, 4.63; 95% CI, 1.292-16.588; P = 0.019). The effect of malignancy was influenced by neutropenia (OR for interaction term, 1.60; 95% CI, 1.15-2.22; P = 0.005). A subgroup analysis revealed that 14-day mortality rate for patients with underlying hematological malignancies and solid tumors was 75% (12/16) and 40% (12/30), respectively. Survival analysis revealed that mortality in patients with hematological malignancies was higher than that in patients with solid tumors (P = 0.032). The outcomes of patients with A. baumannii bacteremia were related to PBS, neutropenia, and malignancy. Compared with solid tumors, patients with hematological malignancies had a higher mortality in the setting of A. baumannii bacteremia.

Clinical manifestations of pneumonia according to the causative organism in patients in the intensive care unit

BACKGROUND/AIMS

Whether the causative organism influences the clinical course of pneumonia in the intensive care unit (ICU) is controversial. We assessed the clinical manifestations and prognosis of pneumonia according to the causative pathogens in patients in a medical ICU.

METHODS

A retrospective observational study was performed in a medical ICU. Among 242 patients who were admitted to the ICU, 103 who were treated for pneumonia were analyzed.

RESULTS

The causative pathogen was identified in 50 patients (49.0%); 22 patients (21.6%) had multidrug-resistant (MDR) pathogens. The distribution of causative micro-organisms was Staphylococcus aureus (20%), Pseudomonas species (16%), Klebsiella pneumoniae (14%), and Acinetobacter baumannii (12%). No significant difference in ICU mortality rate, duration of ICU stay, duration of mechanical ventilation, or frequencies of re-intubation and tracheostomy were detected based on the identification of any pathogen. In sub-analyses according to the pneumonia classification, the number of pathogens identified did not differ between pneumonia types, and a higher incidence of identified MDR pathogens was detected in the hospital-acquired pneumonia group than in the community-acquired or healthcare- acquired pneumonia groups. However, the clinical outcomes of pneumonia according to identification status and type of pathogen did not differ significantly between the groups.

CONCLUSIONS

Neither the causative micro-organism nor the existence of MDR pathogens in critically ill patients with pneumonia was associated with the clinical outcome of pneumonia, including ICU mortality. This result was consistent regardless of the pneumonia classification.

Risk factors and outcome for colistin-resistant Acinetobacter nosocomialis bacteraemia in patients without previous colistin exposure

The clinical characteristics of patients with colistin-resistant Acinetobacter baumannii bacteraemia have been documented, but those of patients with bacteraemia caused by other Acinetobacter species remain unknown. Previous exposure to colistin has been shown to be associated with the emergence of colistin resistance, but may be not the only predisposing factor. In the current study, we highlight the risk and outcome of patients without previous exposure to colistin who acquired colistin-resistant Acinetobacter nosocomialis (ColRAN) bacteraemia. This 11-year single-centre retrospective study analysed 58 patients with ColRAN bacteraemia and 213 patients with colistin-susceptible A. nosocomialis (ColSAN) bacteraemia. Antimicrobial susceptibilities were determined with an agar dilution method. The clonal relationship of ColRAN isolates was determined with pulsed-field gel electrophoresis. A conjugation mating-out assay was conducted to delineate the potential transfer of colistin resistance genes. Multivariable analysis was performed to evaluate the risk factors for ColRAN bacteraemia. Chronic obstructive pulmonary disease (COPD) was independently associated with ColRAN bacteraemia (OR 3.04; 95% CI 1.45-6.37; p 0.003). Patients with ColRAN bacteraemia had higher APACHE II scores, but the two groups showed no significant differences in 14-day mortality (10.3% vs. 10.3%) or 28-day mortality (15.5% vs. 15.0%). ColRAN isolates had greater resistance than ColSAN isolates to all antimicrobial agents except for ciprofloxacin (0% vs. 6.6%). There were 16 different ColRAN pulsotypes, and two major clones were found. Colistin resistance did not transfer to colistin-susceptible A. baumannii or A. nosocomialis. These results show that COPD is an independent risk factor for acquisition of ColRAN bacteraemia. The mortality rates were similar between patients with ColRAN and ColSAN bacteraemia.

Attributable Mortality of Nosocomial Acinetobacter Bacteremia

Objective.

To determine the attributable mortality and outcome of nosocomial Acinetobacter bacteremia.

Design.

Matched, retrospective cohort study.

Setting.

Large, university-based, tertiary care center.

Patients.

Of 219 patients with nosocomial Acinetobacter bacteremia identified by prospective surveillance during a 3-year period, 52 met the criteria for the study and were matched to a control patient by age, sex, primary and secondary diagnosis, operative procedures, and date of admission.

Results.

A 100% success rate was achieved in the proportion of case patients and control patients matched for the compared criteria, except for major operative procedures (88%) and the presence of an important secondary underlying disease (54.5%). Twenty-nine (55.7%) of the case patients died, compared with 10 (19.2%) of the control patients (P < .001). The attributable mortality was 36.5% (95% CI, 27%-46%) and the risk ratio for death was 2.9 (95% CI, 1.58-5.32). In a multivariate survival analysis, older age, mechanical ventilation, renal failure, and Acinetobacter bacteremia (hazard ratio [HR], 4.41; 95% confidence interval [CI], 1.97-9.87; P < .001) were found to be independent predictors of mortality. There was a trend for a longer median duration of hospitalization among case patients, compared with control patients (11.5 vs. 6.5 days; P = .06). Three isolates were resistant to all but 1 antibiotic tested (colistin), and 45 isolates (86.5%) were resistant to 4 or more different antibiotic classes.

Conclusions.

When adjusted for risk-exposure time and severity of disease at admission, nosocomial Acinetobacter bacteremia is associated with mortality in excess of that caused by the underlying diseases alone.

Nosocomial infections in the medical ICU: a retrospective study highlighting their prevalence, microbiological profile and impact on ICU stay and mortality

OBJECTIVES

1. To study the prevalence of nosocomial infections in the Medical ICU. 2. To determine common microorganisms causing nosocomial infections in the ICU and their antibiotic- sensitivity profile. 3. To study the impact of nosocomial infections on ICU stay and mortality.

METHODS

A retrospective 1 year analysis of nosocomial infections in the Medical ICU at Smt. Kashibai Navale Medical College and Hospital, Pune, between January and December 2011 was carried out. Prevalence of nosocomial infections was determined; sites of nosocomial infections and common causative microorganisms were identified; their antibiotic-sensitivity profiles were studied. The group of patients with nosocomial infections was matched with a control group drawn from the pool of patients without nosocomial infections; this matching was done with respect to age, gender and clinical diagnosis. Period of ICU stay and patient mortality rates in the two groups were analysed.

RESULTS

A total of 366 ICU patient records were analysed. Of these, 32 patients were found-to have developed 35 nosocomial infections (9.6% prevalence), of which respiratory infections were the commonest (65.8%), followed by urinary infections (17.1%) and dual infections (urinary plus respiratory) (17.1%).The most frequently isolated microorganism causing respiratory infections was Acinetobacter (40.4%), 21% isolates of which were multidrug resistant; whereas the most frequently isolated microorganism causing urinary tract infections was Pseudomonas (38.4%). Average ICU stay in patients with and without nosocomial infections was 16.5 and 6.4 days respectively; whereas mortality in the two groups was 28.1% and 31.2% respectively. Overall ICU mortality was 19.9%.

CONCLUSION

The nosocomial infection rate in our ICU was in keeping with the rate in many industrialised countries. The most common site of nosocomial infection was the respiratory tract, followed by the urinary tract. Acinetobacter was the commonest respiratory isolate, whereas Pseudomonas was the commonest urinary isolate. One fourth of Acinetobacter isolates were multidrug resistant. Nosocomial infections resulted in a statistically significant increase in ICU stay; whereas there was no impact on ICU mortality.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The minimal inhibitory concentration for sulbactam was not associated with the outcome of infections caused by carbapenem-resistant Acinetobacter sp. treated with ampicillin/sulbactam

OBJECTIVE

The objective of this study was to evaluate whether the outcomes of carbapenem-resistant Acinetobacter infections treated with ampicillin/sulbactam were associated with the in vitro susceptibility profiles.

METHODS

Twenty-two infections were treated with ampicillin/sulbactam. The median treatment duration was 14 days (range: 3-19 days), and the median daily dose was 9 g (range: 1.5-12 g). The median time between Acinetobacter isolation and treatment was 4 days (range: 0-11 days).

RESULTS

The sulbactam minimal inhibitory concentration (MIC) ranged from 2.0 to 32.0 mg/L, and the MIC was not associated with patient outcome, as 4 of 5 (80%) patients with a resistant infection (MIC≥16), 5 of 10 (50%) patients with intermediate isolates (MIC of 8) and only 1 of 7 (14%) patients with susceptible isolates (MIC ≤4) survived hospitalization.

CONCLUSION

These findings highlight the need to improve the correlation between in vitro susceptibility tests and clinical outcome.

Genomic and functional analysis of the type VI secretion system in Acinetobacter

The genus Acinetobacter is comprised of a diverse group of species, several of which have raised interest due to potential applications in bioremediation and agricultural purposes. In this work, we show that many species within the genus Acinetobacter possess the genetic requirements to assemble a functional type VI secretion system (T6SS). This secretion system is widespread among Gram negative bacteria, and can be used for toxicity against other bacteria and eukaryotic cells. The most studied species within this genus is A. baumannii, an emerging nosocomial pathogen that has become a significant threat to healthcare systems worldwide. The ability of A. baumannii to develop multidrug resistance has severely reduced treatment options, and strains resistant to most clinically useful antibiotics are frequently being isolated. Despite the widespread dissemination of A. baumannii, little is known about the virulence factors this bacterium utilizes to cause infection. We determined that the T6SS is conserved and syntenic among A. baumannii strains, although expression and secretion of the hallmark protein Hcp varies between strains, and is dependent on TssM, a known structural protein required for T6SS function. Unlike other bacteria, A. baumannii ATCC 17978 does not appear to use its T6SS to kill Escherichia coli or other Acinetobacter species. Deletion of tssM does not affect virulence in several infection models, including mice, and did not alter biofilm formation. These results suggest that the T6SS fulfils an important but as-yet-unidentified role in the various lifestyles of the Acinetobacter spp.

Risk factors for occurrence and 30-day mortality for carbapenem-resistant Acinetobacter baumannii bacteremia in an intensive care unit

To assess the risk factors for carbapenem-resistant Acinetobacter baumannii (CRAB) bacteremia and for 30-day mortality in patients with CRAB bacteremia in the intensive care unit (ICU), we conducted a retrospective study in the ICU at Severance Hospital in Korea from January 2008 to December 2009. Patients who acquired CRAB bacteremia in the ICU were enrolled as the case group and patients whose specimens of blood culture, sputum/endotracheal aspirate and urine revealed no AB were enrolled as controls. The case group comprised 106 patients and 205 patients were included as controls. Risk factors independently associated with CRAB bacteremia included prior chemotherapy or radiotherapy treatment (Odds ratio [OR], 3.6; P = 0.003), recent central venous catheter insertion (OR, 5.7; P < 0.001) or abdominal drainage insertion (OR, 21.9; P = 0.004), the number of antibiotics treated with (OR, 1.3; P = 0.016), and respiratory failure in the ICU (OR, 2.5; P = 0.035). The 30-day mortality was 79.8%. Renal failure during ICU stay was independently associated with 30-day mortality (OR, 3.7; P = 0.047). It is important to minimize invasive procedures, and to restrict excessive use of antibiotics, especially in immunocompromised patients, in order to prevent the development of CRAB bacteremia. Greater concern for CRAB bacteremia patients is needed when renal failure develops during ICU stay.

Factors influencing survival in patients with multidrug-resistant Acinetobacter baumannii infection

Multidrug-resistant (MDR) Acinetobacter baumannii (Acb) is a rapidly emerging pathogen in healthcare settings. The aim of this study was to evaluate the predictors of poor outcome in patients with MDR Acb. This is the first report documenting factors influencing survival in patients with MDR Acb in this tertiary hospital. This study is a prospective of the hospital epidemiology database. A total of 73 patients with 84 Acb isolates were obtained between August 2009 and October 2010 in this hospital. In the present study, the 30-day mortality rate was 39.7%. Of 84 Acb isolates, 50 (59%) were MDR, nine (11%) were pan-resistant, and 25 (30%) were non-MDR. The non-MDR isolates were used as the control group. The factors significantly associated with multidrug resistance included previous surgeries, presence of comorbidity (renal disease), use of more than two devices, parenteral nutrition, and inappropriate antimicrobial therapy. Significant predictors of 30-day mortality in the univariate analysis included pneumonia, diabetes mellitus, renal disease, use of more than two devices, and inappropriate antimicrobial therapy administered within two days of the onset of infection. The factors associated with mortality in patients with MDR Acb infection in this study were: age > 60 years, pneumonia, diabetes mellitus, renal disease, use of more than two invasive procedures, and inappropriate antimicrobial therapy. Vigilance is needed to prevent outbreaks of this opportunistic and deadly pathogen.

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

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

[Factors associated with mortality in Acinetobacter baumannii infected intensive care unit patients]

Acinetobacter baumannii can survive for prolonged periods in unsuitable environmental conditions and easily spread to patients in the hospital settings leading to healthcare-associated infections. Major risk factors for A.baumannii infections are mechanical ventilation, invasive procedures such as central venous catheter or urinary catheter and the use of broad-spectrum antibiotics. The mortality rates of nosocomial A.baumannii infections have been reported between 50-60%, changing due to several factors. The aim of this study was to investigate the factors associated with mortality in intensive care unit (ICU) patients diagnosed as nosocomial A.baumannii infections. The demographical, clinical and microbiological data of the patients who were followed in ICUs between September 2008 to March 2010 were evaluated retrospectively, and analyzed regarding the factors related to mortality. Blood, urine and tracheal aspirate samples were collected from suspected patients and cultivated on conventional agar media. The identification of the isolates and antibiotic susceptibilities were performed by using VITEK-2 (bioMerieux, USA) automated system. The patients with A.baumannii infections were grouped as "died" and "survived" cases, and the groups were compared according to following factors: age, gender, isolation day of bacteria in intensive care unit, type of clinical sample, implementation day of the central venous catheter, implementation of tracheotomy and/or intubation, operation, presence of diabetes mellitus, antibiotic use, day of hospitalization, day of mechanical ventilation and APACHE (Acute Physiology and Chronic Health Evaluation)-II score. A.baumannii infection was identified in 56 patients (29 female, 27 male; mean age: 63 years) in the intensive care units during the study period, and the total mortality rate was estimated as 77% (43/56). The implementation of intubation, mechanical ventilation, high APACHE II score and recovery of bacteria from respiratory tract were found statistically significant for A.baumannii infections related mortality (p< 0.05 for each parameter). Our data showed that Acinetobacter infection in the respiratory tract, implementation of intubation, mechanical ventilation and high APACHE II scores were the major risk factors related to mortality.

Differences in Acinetobacter baumannii strains and host innate immune response determine morbidity and mortality in experimental pneumonia

Despite many reports documenting its epidemicity, little is known on the interaction of Acinetobacter baumannii with its host. To deepen our insight into this relationship, we studied persistence of and host response to different A. baumannii strains including representatives of the European (EU) clones I–III in a mouse pneumonia model. Neutropenic mice were inoculated intratracheally with five A. baumannii strains and an A. junii strain and at several days morbidity, mortality, bacterial counts, airway inflammation, and chemo- and cytokine production in lungs and blood were determined. A. baumannii RUH875 and RUH134 (EU clone I and II, respectively) and sporadic strain LUH8326 resulted in high morbidity/mortality, whereas A. baumannii LUH5875 (EU clone III, which is less widespread than clone I and II) caused less symptoms. A. baumannii type strain RUH3023^T and A. junii LUH5851 did not cause disease. All strains, except A. baumannii RUH3023^T and A. junii LUH5851, survived and multiplied in the lungs for several days. Morbidity and mortality were associated with the severity of lung pathology and a specific immune response characterized by low levels of anti-inflammatory (IL-10) and specific pro-inflammatory (IL-12p40 and IL-23) cytokines at the first day of infection. Altogether, a striking difference in behaviour among the A. baumannii strains was observed with the clone I and II strains being most virulent, whereas the A. baumannii type strain, which is frequently used in virulence studies appeared harmless.

High mortality associated with Acinetobacter species infection in liver transplant patients

BACKGROUND

Acinetobacter species have become increasingly important nosocomial pathogens worldwide and can result in a wide range of infections, including bacteremia, pneumonia, urinary tract infection, peritonitis, among others. The aim of this study was to investigate clinical characteristics, mortality, and outcomes among liver transplant recipients with Acinetobacter species infections.

METHODS

We retrospectively analyzed 451 subjects who had undergone living donor liver transplantations between January 2001 and May 2010. Pandrug-resistant (PDR) Acinetobacter species were defined as resistant to all commercially available antibiotics except colistin.

RESULTS

Infectious complications due to Acinetobacter species appeared in 26 patients (5.8%) with a total of 37 episodes. Of the species identified, 34 were Acinetobacter baumannii and 3 Acinetobacter Iwoffiii. The presumed sources of infection were the biliary tract (n = 21, 56.8%), lung (n = 7, 18.9%), intra-abdomen (n = 6, 16.2%), catheter (n = 2, 5.4%), and urinary tract (n = 1, 3.6%). Among the 37 Acinetobacter species, 75.7% (28/37) were PDR species. Age, duration of intensive care unit stay, Child-Pugh score, and Model for End-stage Liver Disease score were not significant risk factors for Acinetobacter species infection. However, the overall mortality among patients with Acinetobacter species infections was 50% (13/26), which was significantly higher than that among those free of infection (50% vs 11.5%, P < .05). Multivariate analysis using a Cox regression model showed that inappropriate antimicrobial treatment was a significant independent risk factor for mortality among patients with Acinetobacter species infections (hazard Ratio = 4.19, 95% confidence interval 1.1-18.7; P = .06).

CONCLUSION

Patients with Acinetobacter species infections after liver transplantation show a significantly worse prognosis. PDR Acinetobacter species have been a major problem in our center.

Mortality attributable to carbapenem-resistant nosocomial Acinetobacter baumannii infections in a Turkish university hospital

This study was performed to compare the mortality associated with carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-sensitive A. baumannii (CSAB) infections, to identify potential risk factors for CRAB infections, and to investigate the effects of potential risk factors on mortality in CRAB and CSAB patients. This retrospective case-control study was conducted in a university hospital between January 1, 2005 and December 30, 2006. One hundred and ten patients with CRAB and 55 patients with CSAB infection were identified during the study period. The mortality rate was 61.8% and 52.7% in CRAB and CSAB cases, respectively (P = 0.341). In CRAB cases, the risk factors for mortality were identified as intubation (odds ratio [OR], 3.3; 95% confidence interval [CI], 1.0-10.1; P = 0.042) and high APACHE II score (OR, 1.2; 95% CI, 1.1-1.3; P = 0.000), by multivariate analysis. Previous use of carbapenem (OR, 6.1; 95% CI, 2.2-17.1; P = 0.001) or aminopenicillin (OR, 2.5; 95% CI, 1.2-5.1; P = 0.013) were independently associated with carbapenem resistance. Although the mortality rate was higher among patients with CRAB infections, this difference was not found to be statistically significant. Previous use of carbapenem and aminopenicillin were found to be independent risk factors for infections with CRAB.

Clinical characteristics of tertiary hospital patients from whom Acinetobacter calcoaceticus-Acinetobacter baumannii complex strains were isolated

OBJECTIVE

Acinetobacter baumannii is a worldwide nosocomial pathogen that has become increasingly common over the past few decades, and strains of multidrug-resistant A. baumannii have been increasing. The aim of this study was to assess the clinical characteristics of A. calcoaceticus-A. baumannii complex (Acb complex) strains and to determine the risk factors of this infection.

METHODS

The medical records of 121 patients at Nagasaki University Hospital from whom Acb complex had been isolated between January 2007 and December 2009 were retrospectively reviewed. Patient backgrounds, sensitivity to antibiotics, risk factors for infection, and prognosis were evaluated.

RESULTS

Lower respiratory isolates accounted for 73% (147 strains) of all 201 isolates. Most of the isolates were sensitive to carbapenems. Of the 121 patients (74 males and 47 females; mean age: 62.1 years), 48 (39.7%) had malignancy and 75 (62.0%) were treated with antibiotics prior to isolation. Thirty-seven of the patients in this study (30.6%) were infected by Acb complex and the most frequent clinical manifestation was pneumonia (18 cases; 48.6%). Approximately 60% of infected patients were treated with β-lactam agent in combination with β-lactamase inhibitors or carbapenems. The mortality rate of infected patients was significantly higher than that of colonized patients (infected: 24.3%, colonized: 6.0%, p<0.05). Risk factors for Acb complex infection include being over 60 years of age, chronic liver disease, and the use of first-generation cephalosporins prior to isolation.

CONCLUSION

Acb complex was relatively sensitive to antibiotics. The appropriate usage of antibiotics should be continued for the prevention of drug resistance in Acb complex.

[Acinetobacter baumannii - related mortality in intensive care units in Colombia]

OBJECTIVE

Compare mortality in multidrug-susceptible Acinetobacter baumannii infected patients and multidrug-resistant A. baumannii-infected patients hospitalized in intensive care units (ICUs) in Colombia.

METHODS

A prospective, observational, and multicenter study. A total of 165 patients admitted to the participating ICUs from April 2006 to April 2010 were included. On day 14 and day 30 of hospitalization, mortality in multidrug-resistant patients with clinical isolates of A. baumannii was compared with that in multidrug-susceptible patients.

RESULTS

Of the 165 adult patients who had health care-associated infections (HAI) caused by A. baumannii, multidrug-susceptible bacteria were found in 62 patients and multidrug-resistant bacteria in 103. Statistically significant differences in mortality on day 14 of hospitalization in the ICU were not found. On the other hand, significant differences (P < 0.05) in mortality on day 30 of hospitalization were observed between patients with multidrug-resistant isolates and those with multidrug-susceptible isolates. This difference was maintained when the patients' risk factors were evaluated by multivariate analysis.

CONCLUSIONS

The presence of multidrug resistance is the primary risk factor for mortality in patients with HAI caused by A. baumannii in Colombian ICUs.

[Acinetobacter baumannii: an important pathogen with multidrug resistance in newborns]

Nosocomial sepsis agents with multidrug resistance have led to higher morbidity and mortality in premature infants in the recent years. Acinetobacter baumannii has become a leading cause of nosocomial sepsis in several neonatal intensive care units. In this study, the demographic, clinic, microbiologic characteristics and risk factors of 21 premature infants hospitalized in newborn intensive care unit between January 2010-February 2011 and developed A.baumannii infection, have been evaluated retrospectively. The isolates were identified by conventional methods and antibiotic susceptibility tests were performed by Vitek 2 GN and AST-N090 using Vitek 2 Compact system (BioMerieux, France). A.baumannii was isolated from the blood samples of 10 patients, central venous catheter samples of three patients, CSF samples of two, tracheal aspirate of two and urine sample of one patient. In two patients both blood and central venous catheter samples and in one patient both blood and CSF samples revealed A.baumannii. Gestational age was between 22-30 weeks and birth weight was between 500-1320 grams (17 were < 1000 g) in 19 patients. A.baumannii caused early onset (≤ 3 days) sepsis in four, and late onset (≥ 4 days) sepsis in 17 patients. The main risk factors were detected as mechanical ventilation (n= 20, 95%), prematurity (n= 19, 91%), total parenteral nutrition (n= 17, 81%) and central catheter use (n= 14, 67%). Antibiotics with highest rates of susceptibility were gentamicin (18/21), amikacin (14/21), and colistin (10/21). Twenty (95%) isolates had multiple drug resistance. Amikacin, gentamicin, colistin and imipenem were used for treatment, however 12 infants, 8 of which due to sepsis, died. In conclusion, A.baumannii which is an important nosocomial sepsis agent with multidrug resistance, is increasing in incidence. To control Acinetobacter infections especially in low-birth weight infants, the use of invasive procedures, total parenteral nutrition and broad spectrum antibiotics should be limited and infected patients should be isolated besides establishment of other appropriate infection control measures.

Clinical outcomes of patients infected with carbapenem-resistant Acinetobacter baumannii treated with single or combination antibiotic therapy

OBJECTIVE

To evaluate treatment outcomes in patients with carbapenem-resistant Acinetobacter baumannii (CRAB) nosocomial infections treated with antimicrobial agent either alone or in combination.

MATERIAL AND METHOD

Clinical data were retrospectively evaluated in patients with CRAB nosocomial infections admitted to Songklanagarind Hospital, Songkhla, Thailand from January-December 2008.

RESULTS

One hundred ten patients with CRAB nosocomial infections were identified. Most patients (57.3%) had site of infection in the lower respiratory tract and the majority of them (61.8%) received a single antimicrobial agent. Crude mortality was 30%. The presumptive success rate was 60.3% (41/68) for patients given monotherapy and 81.0% (34/42) for patients given combination therapy (p = 0.024). Patients given combination therapy were more likely to have been given at least one antibiotic to which the organism was susceptible (p = 0.004). In multivariate analysis, renal impairment, bloodstream infection, and inappropriate antimicrobial regimen were independent predictors of treatment failure.

CONCLUSION

The combination therapy regimen yielded more presumptive treatment success by increasing the likelihood of an appropriate antimicrobial therapy. Additionally, inappropriate antimicrobial treatment, renal impairment, and bloodstream infection were associated with poor treatment outcomes in patients with CRAB nosocomial infections.

The outcomes of using colistin for treating multidrug resistant Acinetobacter species bloodstream infections

Despite the identification of Acinetobacter baumannii isolates that demonstrate susceptibility to only colistin, this antimicrobial agent was not available in Korea until 2006. The present study examined the outcomes of patients with multidrug resistant (MDR) Acinetobacter species bloodstream infection and who were treated with or without colistin as part of their regimen. The colistin group was given colistin as part of therapy once colistin became available in 2006. The non-colistin group was derived from the patients who were treated with other antimicrobial regimens before 2006. Mortality within 30 days of the onset of bacteremia occurred for 11 of 31 patients in the colistin group and for 15 of 39 patients in the non-colistin group (35.5% vs 38.5%, respectively, P = 0.80). Renal dysfunction developed in 50.0% of the 20 evaluable patients in the colistin group, but in 28.6% of the 35 evaluable patients in the non-colistin group (P = 0.11). On multivariate analysis, only an Acute Physiological and Chronic Health Evaluation II score ≥ 21 was associated with mortality at 30 days. This result suggests that administering colistin, although it is the sole microbiologically appropriate agent, does not influence the 30 day mortality of patients with a MDR Acinetobacter spp. bloodstream infection.

Prediction of patient outcome from Acinetobacter baumannii bacteremia with Sequential Organ Failure Assessment (SOFA) and Acute Physiology and Chronic Health Evaluation (APACHE) II scores

OBJECTIVE

Acinetobacter baumannii is an important nosocomial pathogen associated with a high mortality rate. However, no objective and quantitative severity scores are available for the severity stratification. We aimed to assess the effectiveness of SOFA and APACHE II scores calculated at the onset of bacteremia in predicting the mortality of patients with A. baumannii bacteraemia.

PATIENTS AND METHODS

A total of 110 patients with A. baumannii bacteremia were included in this retrospective study during the 40-month study period. Information including clinical and laboratory data was collected.

RESULTS

Multivariate analysis showed that both SOFA and APACHE II scores were independent outcome predictors after adjustment for other parameters. Goodness-of-fit was good for SOFA and APACHE II, and both models displayed excellent AUROCs (SOFA: 0.83 ± 0.06, APACHE II: 0.82 ± 0.08 in predicting 14-day mortality; SOFA: 0.85 ± 0.04, APACHE II: 0.81 ± 0.04 in predicting in-hospital mortality). There was no significant difference in the predictions of the two scoring systems, and the scores were highly correlated (r(2)=0.724, p <0.001). We found that SOFA >8, APACHE II >29 and SOFA >7, APACHE II >23 are associated with significantly higher 14-day and in-hospital mortality rates, respectively.

CONCLUSION

SOFA and APACHE II scores assessed at the onset of bacteremia are reliable risk stratifying tools in predicting 14-day and in-hospital mortality in A. baumannii bacteremia. For ease of calculation, the use of SOFA rather than APACHE II score to predict mortality of A. baumannii bacteremia might have clinical application.

High and increasing Oxa-51 DNA load predict mortality in Acinetobacter baumannii bacteremia: implication for pathogenesis and evaluation of therapy

Background

While quantification of viral loads has been successfully employed in clinical medicine and has provided valuable insights and useful markers for several viral diseases, the potential of measuring bacterial DNA load to predict outcome or monitor therapeutic responses remains largely unexplored. We tested this possibility by investigating bacterial loads in Acinetobacter baumannii bacteremia, a rapidly increasing nosocomial infection characterized by high mortality, drug resistance, multiple and complicated risk factors, all of which urged the need of good markers to evaluate therapeutics.

Methods and Findings

We established a quantitative real-time PCR assay based on an A. baumannii-specific gene, Oxa-51, and conducted a prospective study to examine A. baumannii loads in 318 sequential blood samples from 51 adults patients (17 survivors, 34 nonsurvivors) with culture-proven A. baumannii bacteremia in the intensive care units. Oxa-51 DNA loads were significantly higher in the nonsurvivors than survivors on day 1, 2 and 3 (P = 0.03, 0.001 and 0.006, respectively). Compared with survivors, nonsurvivors had higher maximum Oxa-51 DNA load and a trend of increase from day 0 to day 3 (P<0.001), which together with Pitt bacteremia score were independent predictors for mortality by multivariate analysis (P = 0.014 and 0.016, for maximum Oxa-51 DNA and change of Oxa-51 DNA, respectively). Kaplan-Meier analysis revealed significantly different survival curves in patients with different maximum Oxa-51 DNA and change of Oxa-51 DNA from day 0 to day 3.

Conclusions

High Oxa-51 DNA load and its initial increase could predict mortality. Moreover, monitoring Oxa-51 DNA load in blood may provide direct parameters for evaluating new regimens against A. baumannii in future clinical studies.

Predictors of mortality of Acinetobacter baumannii infections: A 2-year prospective study in a Greek surgical intensive care unit

BACKGROUND

Nosocomial infections are a frequent and continuously increasing problem worldwide, have a rapidly increasing multidrug resistance to antibiotics, and are associated with significant morbidity and mortality.

OBJECTIVE

Our objectives were to evaluate Acinetobacter baumannii infection incidence in our surgical intensive care unit (SICU), the clinical features and outcome of these patients, and, particularly, to investigate predictors of A baumannii infection-related mortality.

METHODS

Ours was a prospective study of all patients with ICU-acquired A baumannii infection from January 1, 2006, to December 31, 2007.

RESULTS

Among 680 patients, 60 (8.8%) sustained A baumannii infection. Mean age was 68.4 ± 6.2 years, Acute Physiology and Chronic Health Evaluation (APACHE) II score on SICU admission 20.6 ± 8.1 and Sequential Organ Failure Assessment (SOFA) score on infection day 9.5 ± 4.2 (women: 50%). Multidrug resistance, morbidity, and mortality were 45%, 65%, and 46.6% (n = 28), respectively. In multivariate analysis, age (P = .03; odds ratio [OR], 1.13; 95% confidence interval [CI]: 1.018-1.259), acute renal failure (P = .001; OR, 17.9; 95% CI: 6.628-75.565), and thrombocytopenia (P = .03; OR, 26.4; 95% CI: 1.234-56.926) complicating the infection and subsequent Enterococcus faecium bacteremia (P = .01; OR, 3.5; 95% CI: 1.84-6.95) were mortality predictors.

CONCLUSION

A baumannii infections are frequent and associated with high drug multiresistance, morbidity, and mortality. Age, renal failure, thrombocytopenia, and subsequent E faecium bacteremia were predictors of A baumannii infection-associated mortality.

Mortality rate in patients with nosocomial Acinetobacter meningitis from a Brazilian hospital

BACKGROUND

The mortality rate due to Acinetobacter baumannii nosocomial meningitis (ANM) is high.

OBJECTIVE

The aim of this study was to evaluate the factors that have influence over the outcomes in ANM patients.

METHODS

A retrospective analysis of 22 cases of ANM was conducted in a hospital with high incidence of multidrug resistance.

RESULTS

The mean age of patients was 43 years (21 to 91) and 54.5% were male. All ANM cases occurred within 60 days of admission and the mean duration of illness was of 18.2 days. All cases were associated with previous neurosurgical procedures: elective surgery (27.2%), external shunt (54.4%) and emergency surgery due to trauma (18.1%). Imipenem resistance was observed in 40.9% of cases, but ampicillin/sulbactam resistance was lower (27.2%). The mortality rate of ANM patients was of 72.7%. The only risk factor associated with mortality was inappropriate therapy within five days after CSF collection. All patients who survived the meningitis episode had received appropriate therapy, in contrast to only 69.2% of those who did not survive (OR = 5.15; IC = 0.45-54.01).

CONCLUSIONS

The high mortality rate observed in our study suggests the need for aggressive empirical treatment with addition of drugs, including intrathecal therapy, where multi-resistant A. baumannii is endemic.

[Multidrug resistant Acinetobacter baumanii:clinical update and new highlights]

The role of multidrug resistant Acinetobacter baumanii and its clinical relevance have been recently appreciated as a ubiquitous opportunistic nosocomial pathogen. Risk factors associated with A. baumanii infection include severe underlying diseases, previous surgery, invasive procedures, treatment with broad-spectrum antibiotics, length of hospital stay, admission to intensive care units (ICU). Carbapenem-multidrug resistant A. baumanii infections are probably associated to greater severity and more complications; in our cohort mortality was 49.3% and related mortality (within 72 hours) was 10.39%. However, severe underlying diseases probably play an important role in the clinical outcome of patients with MDR-C A. baumanii infection and controversy exists regarding the real mortality attributable to antimicrobial resistance because a high proportion of deaths took place > 7 days after diagnosis. Nevertheless, in our experience, carbapenem resistance, inappropriate therapy and monotherapy are associated to a higher mortality. Special attention should be paid to design well-controlled prospective clinical trials to determine the optimal antimicrobial therapy in critically ill patients suspected of having MDR Acinetobacter infection.

[Risk of hospital death in nosocomial infection with multi-drug resistant A. baumanii or P. aeruginosa]

OBJECTIVE

assessment of the in hospital death among the patients with healthcare associated infection (HA1) provoked by multi drug resistant strains (MDR) ofP. aeruginosa or A. baumanii.

METHODS

enrolled in the study were patients with bloodstream, surgical site and urinary tract HAI infection, reported during 2006-2009 in the ICU for adults and general surgery wards of two large teaching clinics for emergencies in Bucharest municipality. Associations between fatal outcome and relevant demographic and clinical characteristics were analyzed both through cohort and also by case-control studies.

RESULTS

in the cohort analysis both the severity of the underlying disease and also the presence of HAl with MDR strains of P. aeruginosa or A. baumanii were statistical significant (p < 0.05) and independently associated with fatal outcome; the presence of HAI with MDR strains of P. aeruginosa or A. baumanii remained significant associated with fatal outcome even after controlling of the underlying disease's severity by case-control design (Match OR: 5.89; 95% IC: 1.39-40.77; p = 0.011).

CONCLUSIONS

the study's results demonstrate that the precautions to prevent the in hospital transmission of the MDR germs are pertinent because the HAI induced by these bugs is obviously associated with unfavorable clinical outcome of the patient.