Nosocomial multi-drug resistant Acinetobacter baumannii bloodstream infection: risk factors and outcome with ampicillin-sulbactam treatment

Current Therapeutic Approaches for Multidrug-Resistant and Extensively Drug-Resistant Acinetobacter baumannii Infections

The treatment of Acinetobacter baumannii infections remains a challenge for physicians worldwide in the 21st century. The bacterium possesses a multitude of mechanisms to escape the human immune system. The consequences of A. baumannii infections on morbidity and mortality, as well on financial resources, remain dire. Furthermore, A. baumannii superinfections have also occurred during the COVID-19 pandemic. While prevention is important, the antibiotic armamentarium remains the most essential factor for the treatment of these infections. The main problem is the notorious resistance profile (including resistance to carbapenems and colistin) that this bacterium exhibits. While newer beta lactam/beta-lactamase inhibitors have entered clinical practice, with excellent results against various infections due to Enterobacteriaceae, their contribution against A. baumannii infections is almost absent. Hence, we have to resort to at least one of the following, sulbactam, polymyxins E or B, tigecycline or aminoglycosides, against multidrug-resistant (MDR) and extensively drug-resistant (XDR) A. baumannii infections. Furthermore, the notable addition of cefiderocol in the fight against A. baumannii infections represents a useful addition. We present herein the existing information from the last decade regarding therapeutic advances against MDR/XDR A. baumannii infections.

A systematic review on the excess health risk of antibiotic-resistant bloodstream infections for six key pathogens in Europe

BACKGROUND

Antimicrobial resistance is a global threat, which requires novel intervention strategies, for which priority pathogens and settings need to be determined.

OBJECTIVES

We evaluated pathogen-specific excess health burden of drug-resistant bloodstream infections (BSIs) in Europe.

METHODS

A systematic review and meta-analysis.

DATA SOURCES

MEDLINE, Embase, and grey literature for the period January 1990 to May 2022.

STUDY ELIGIBILITY CRITERIA

Studies that reported burden data for six key drug-resistant pathogens: carbapenem-resistant (CR) Pseudomonas aeruginosa and Acinetobacter baumannii, third-generation cephalosporin or CR Escherichia coli and Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium. Excess health outcomes compared with drug-susceptible BSIs or uninfected patients. For MRSA and third-generation cephalosporin E. coli and K. pneumoniae BSIs, five or more European studies were identified. For all others, the search was extended to high-income countries.

PARTICIPANTS

Paediatric and adult patients diagnosed with drug-resistant BSI.

INTERVENTIONS

Not applicable.

ASSESSMENT OF RISK OF BIAS

An adapted version of the Joanna-Briggs Institute assessment tool.

METHODS OF DATA SYNTHESIS

Random-effect models were used to pool pathogen-specific burden estimates.

RESULTS

We screened 7154 titles, 1078 full-texts and found 56 studies on BSIs. Most studies compared outcomes of drug-resistant to drug-susceptible BSIs (46/56, 82.1%), and reported mortality (55/56 studies, 98.6%). The pooled crude estimate for excess all-cause mortality of drug-resistant versus drug-susceptible BSIs ranged from OR 1.31 (95% CI 1.03-1.68) for CR P. aeruginosa to OR 3.44 (95% CI 1.62-7.32) for CR K. pneumoniae. Pooled crude estimates comparing mortality to uninfected patients were available for vancomycin-resistant Enterococcus and MRSA BSIs (OR of 11.19 [95% CI 6.92-18.09] and OR 6.18 [95% CI 2.10-18.17], respectively).

CONCLUSIONS

Drug-resistant BSIs are associated with increased mortality, with the magnitude of the effect influenced by pathogen type and comparator. Future research should address crucial knowledge gaps in pathogen- and infection-specific burdens to guide development of novel interventions.

Risk factors for bacteremia and mortality due to multidrug-resistant Acinetobacter baumannii: a retrospective study

This research aimed to determine the relationships between the risk factors for nosocomial multidrug-resistant Acinetobacter baumannii (MDRAB) bacteremia and associated mortality. We analyzed 144 patients treated for A. baumannii bacteremia, including 120 patients with MDRAB bacteremia, from March 2015 to March 2020, in this retrospective study. The overall bacteremia-related mortality rate was 48.6%. The mortality rates were 25.0% and 53.3% for non-MDRAB and MDRAB bacteremia, respectively. Risk factors for the development of MDRAB bacteremia were prior use of cephalosporins [odds ratio (OR): 8.62; P < .001], carbapenems (OR: 15.04; P < .001), or quinolones (OR: 5.02; P = .040); indwelling urinary catheters (OR: 21.38; P < .001); and respiratory tract as the source of bacteremia (OR: 75.33; P < .001). Patients with elective surgeries were inclined to develop non-MDRAB bacteremia (OR: 0.45; P = .029). High scores in the Acute Physiology and Chronic Health Evaluation II (OR: 1.321; P < .001) and Sequential Organ Failure Assessment (OR: 1.326; P < .001) were risk factors for mortality from MDRAB infection. In summary, higher mortality rates occur in patients with MDRAB bacteremia, and risk factors include prior use of cephalosporins, carbapenems, or quinolones. Urinary catheters and the respiratory tract as sources of the infection increase the risk of MDRAB bacteremia.

Shift in risk factors for mortality by period of the bloodstream infection timeline

BACKGROUND

This study was designed to determine changes in risk factors on the prognosis of patients during each period of the bloodstream infection (BSI) timeline.

METHODS

Through an integrated study of multivariable regressions with machine learning techniques, the risk factors for mortality during each period of BSI were analyzed.

RESULTS

A total of 302,303 inpatients who underwent blood cultures during 2011-2021 were enrolled. More than 8 % of BSI cases progressed to subsequent BSI, and risk factors were identified as gut colonization with vancomycin-resistant enterococci (aOR 1.82; 95 % CI 1.47-2.24), intensive care unit admission (aOR 3.37; 95 % CI 3.35-4.28), and current cancer chemotherapy (aOR 1.54; 95 % CI 1.36-1.74). The mean SOFA score of the deceased patients during the first 7 days was 10.6 (SD 4.3), which was significantly higher than those on days 8-30 (7.0 ± 4.2) and after Day 30 (4.0 ± 3.5). BSIs caused by Acinetobacter baumannii and Candida albicans were more likely to result in deaths of patients for all time periods (all, P < 0.001). BSIs caused by Enterococcus faecalis and Enterococcus faecium were associated with a poor outcome in the period after Day 30 (both, P < 0.001). Nonsusceptible phenotypes to β-lactam/β-lactamase inhibitors of Escherichia coli and Klebsiella pneumoniae influenced the prognoses of patients with BSI in terms of high mortality rates during both days 8-30 and after Day 30.

CONCLUSION

Influence of microbiological factors on mortality, including BSI-causative microorganisms and their major antimicrobial resistance, was emphasized in both periods of days 8-30 and after Day 30.

Impact of antibiotic exposure on antibiotic-resistant Acinetobacter baumannii isolation in intensive care unit patients: a systematic review and meta-analysis

BACKGROUND

Acinetobacter baumannii (AB) poses a significant threat to critically ill patients in intensive care units (ICUs). Although an association between antibiotic exposure and resistant AB is reported in the literature, a synthesis of evidence in ICU patients is still lacking.

AIM

To summarize the evidence on the association between prior antibiotic exposure and the occurrence of resistant AB in ICU patients.

METHODS

Online databases were searched for cohort and case-control studies providing data on the association of interest. Carbapenem/multidrug-resistant AB isolation was compared with non-isolation; carbapenem/multidrug-resistant AB was compared with carbapenem/antibiotic-susceptible AB; and extensively drug-resistant AB isolation was compared with non-isolation. Each comparison was subjected to a restricted maximum likelihood random-effects meta-analysis per antibiotic class, estimating pooled ORs. Stratified meta-analyses were performed by study design, outcome type and association-measure adjustment.

FINDINGS

Overall, 25 high-quality studies were retrieved. Meta-analyses showed that carbapenem/multidrug-resistant AB isolation was associated with previous exposure to aminoglycosides, carbapenems, third-generation cephalosporines, glycylcyclines, and nitroimidazoles. Increased risk of isolation of carbapenem/multidrug-resistant AB isolation vs carbapenem/antibiotic-susceptible AB was shown for prior exposure to aminoglycosides, antipseudomonal penicillins, carbapenems, fluoroquinolones, glycopeptides, and penicillins. Third-generation cephalosporin exposure increased the risk of extensively drug-resistant AB isolation vs non-isolation.

CONCLUSION

This systematic review clarifies the role of antibiotic use in antibiotic-resistant AB spread in ICUs, although for some antibiotic classes the evidence is still uncertain due to the small number of adjusted analyses, methodological and reporting issues, and limited number of studies. Future studies need to be carried out with standardized methods and appropriate reporting of multivariable models.

How to treat severe Acinetobacter baumannii infections

PURPOSE OF REVIEW

To update the management of severe Acinetobacter baumannii infections (ABI), particularly those caused by multi-resistant isolates.

RECENT FINDINGS

The in vitro activity of the various antimicrobial agents potentially helpful in treating ABI is highly variable and has progressively decreased for many of them, limiting current therapeutic options. The combination of more than one drug is still advisable in most circumstances. Ideally, two active first-line drugs should be used. Alternatively, a first-line and a second-line drug and, if this is not possible, two or more second-line drugs in combination. The emergence of new agents such as Cefiderocol, the combination of Sulbactam and Durlobactam, and the new Tetracyclines offer therapeutic options that need to be supported by clinical evidence.

SUMMARY

The apparent limitations in treating infections caused by this bacterium, the rapid development of resistance, and the serious underlying situation in most cases invite the search for alternatives to antibiotic treatment, the most promising of which seems to be bacteriophage therapy.

Insights into the epidemiology, risk factors, and clinical outcomes of carbapenem-resistant Acinetobacter baumannii infections in critically ill children

Background and aims

Carbapenem-resistant Acinetobacter baumannii (CRAB) has become a leading cause of nosocomial infections with an increasing impact on critically ill patients, yet there is limited data on contributing factors. This study was aim to evaluate the prevalence and risk factors, and clinical outcomes of CRAB infections among critically ill children in a tertiary university teaching hospital in China.

Methods

From January 2016 to December 2021, all children diagnosed with nosocomial Acinetobacter baumannii (A. baumannii) infections in the pediatric intensive care unit (PICU) were identified through the computerized microbiology laboratory databases. Among them, children suffering from CRAB infection were designated as a case group, while children with carbapenem susceptible A. baumannii (CSAB) infection were assigned to a control group. This retrospective case-control study was based on two groups of patients to determine potential clinical factors contributing to CRAB infection and death among critically ill children via univariate and multivariate analyses.

Results

During the 6-year study period, a total of 372 episodes of nosocomial A. baumannii infection in the PICU were eligible and included in the study. These isolates displayed moderate or high rates of resistance to all tested antimicrobials except colistin. The overall prevalence of CRAB and MDRAB (multidrug-resistant A. baumannii) was 78.0% and 80.9%, respectively. Several risk factors found to significantly increase CRAB infection included receiving invasive operation (OR = 9.412, p = 0.001), gastric intubation (OR = 2.478, p = 0.026), prior carbapenems exposure (OR = 2.543, p = 0.003), severe pneumonia (OR = 3.235, p = 0.001), and hemoglobin <110g/L (OR = 3.049, p = 0.005). Of 372 patients with CRAB infection, the mortality rate was 30.9% (115/372) and mortality did not differ between children with CRAB and CSAB infections. Septic shock (OR = 2.992, p = 0.001), AST > 46U/L (OR = 2.015, p = 0.005), bone marrow aspiration (OR = 2.704, p = 0.008), lymphocyte <20 % (OR = 1.992, p = 0.006) and age (OR = 1.094, p = 0.002) were independent risk factors for the death of A. baumanni infection.

Conclusions

This study highlights considerable incidence rate and remarkable mortality of children with A. baumanni (especially CRAB) infections, and identifies age-specific risk factors for CRAB infection and mortality in critically ill children. These risk factors should be taken into account in pediatric hospitals in order to establish early intervention and rational treatment to improve clinical outcomes.

Genomic Determinants of Pathogenicity and Antimicrobial Resistance of Nosocomial Acinetobacter baumannii Clinical Isolates of Hospitalized Patients (2019-2021) from a Sentinel Hospital in Hangzhou, China

Purpose

Acinetobacter baumannii (A. baumannii or AB) is one of the most opportunistic, nosocomial pathogens threatening public healthcare across countries. A. baumannii has become a primary growing concern due to its exceptional ability to acquire antimicrobial resistance (AMR) to multiple antimicrobial agents which is increasingly reported and more prevalent every year. Therefore, there is an urgent need to evaluate the AMR knowledge of A. baumannii for effective clinical treatment of nosocomial infections. This study aimed to investigate the clinical distribution AMR phenotypes and genotypes, and genomic characteristics of A. baumannii isolates recovered from hospitalized patients of different clinical departments of a sentinel hospital to improve clinical practices.

Methods

A total of 123 clinical isolates were recovered from hospitalized patients of different clinical departments during 2019-2021 to analyze AMR patterns, and further subjected to whole-genome sequencing (WGS) investigations. Multi-locus sequence typing (MLST), as well as the presence of antimicrobial-resistant genes (ARGs), virulence factor genes (VFGs) and insertion sequences (ISs) were also investigated from WGS data.

Results

The results highlighted that A. baumannii clinical isolates had shown a high AMR rate, particularly from the intensive care unit (ICU), towards routinely used antimicrobials, ie, β-lactams and fluoroquinolones. ST2 was the most prevalent ST in the clinical isolates, it was strongly associated to the resistance of cephalosporins and carbapenems, with bla_OXA-23 and bla_OXA-66 being the most frequent determinants; moreover, high carrier rate of VFGs was also observed such as all strains containing the ompA, adeF, pgaC, lpsB, and bfmR genes.

Conclusion

Acinetobacter baumannii clinical isolates are mostly ST2 with high rates of drug resistance and carrier of virulence factors. Therefore, it requires measurements to control its transmission and infection.

Development of Antimicrobial Peptide-Antibiotic Conjugates to Improve the Outer Membrane Permeability of Antibiotics Against Gram-Negative Bacteria

Antibiotics have been widely used in the medical field as a treatment for infectious diseases, but they are not effective against all Gram-negative bacteria because of their low permeability to the outer membrane. One of the strategies to improve the antibacterial activity of antibiotics is the coadministration of antibiotics and membrane-perturbing antimicrobial peptides for their synergistic effects. However, because of their different pharmacokinetics, their coadministration may not exert expected effects in the clinical stage. Here, we designed various antimicrobial peptide-antibiotic conjugates as a novel approach to improve the antimicrobial activity of antibiotics. Ampicillin was chosen as a model antibiotic with poor outer membrane permeability, and the effects of the chemistry and position of conjugation and the choice of antimicrobial peptides were examined. One of the ampicillin conjugates exhibited significantly improved antimicrobial activity against ampicillin-resistant Gram-negative bacteria without exerting cytotoxicity against human cultured cells, demonstrating that our novel approach is an effective strategy to improve the antimicrobial activity of antibiotics with low outer membrane permeability.

Multicenter Study of the Risk Factors and Outcomes of Bloodstream Infections Caused by Carbapenem-Non-Susceptible Acinetobacter baumannii in Indonesia

The prevalence of bacteremia caused by carbapenem-non-susceptible Acinetobacter baumannii (CNSAB) continues to increase, and it is associated with a high mortality rate. Early recognition of infection and mortality determinants risk factors is necessary for adequate antibiotic administration. We aimed to determine the risk factors and outcomes of CNSAB bacteremia in Indonesia. A multicenter case-control study was conducted in three referral hospitals in Indonesia. Data were collected retrospectively from January 2019 to December 2021. Cases were defined as patients with bacteremia where CNSAB was isolated from the blood, while the controls were patients with bacteremia caused by carbapenem-susceptible A. baumannii (CSAB). Risk factors for bacteremia and mortality associated with CNSAB bacteremia were determined using univariates analysis (chi-squared and Student's t-test or Mann-Whitney test) and multivariate logistic regression analysis. A total of 144 bacteremia patients were included, of whom 72 patients were for each case and control group. The final model of multivariate regression analysis revealed that bacteremia source from the lower respiratory tract (adjusted odds ratio (aOR): 3.24; 95% CI: 1.58-6.63, p = 0.001) and the use of central venous catheter (aOR: 2.56; 95% CI: 1.27-5.18; p = 0.009) were independent risk factors for CNSAB bacteremia. Charlson Comorbidity Index ≥ 4 (aOR: 28.56; 95% CI: 3.06-265.90, p = 0.003) and Pitt Bacteremia Score ≥ 4 (aOR: 6.44; 95% CI: 1.17-35.38; p = 0.032) were independent risk factors for mortality due to CNSAB bacteremia. Only high Pitt Bacteremia Score was an independent risk factor for mortality of CSAB bacteremia. In conclusion, we identified the risk factors for CNSAB-associated bacteremia and the risk factors for death, which are relevant for empiric therapy and infection control prevention, as well as prognosis evaluation of patients with bloodstream infections.

Systematic review and meta-analysis of the proportion and associated mortality of polymicrobial (vs monomicrobial) pulmonary and bloodstream infections by Acinetobacter baumannii complex

BACKGROUND

Differentiating Acinetobacter baumannii complex (ABC) infection from colonization remains difficult and further complicated in polymicrobial infections.

PURPOSE

To assess the frequency of polymicrobial ABC infections and associated mortality. We hypothesized a lower mortality in polymicrobial infections if ABC isolation reflects colonization in some polymicrobial infections.

METHODS

A systematic review was conducted in PubMed, Scopus and CENTRAL for studies reporting ABC pulmonary and bloodstream infections. The proportion of infections that were polymicrobial and the magnitude of the association between polymicrobial (vs monomicrobial) infection and mortality were estimated with meta-analyses.

RESULTS

Based on 80 studies (9759 infections) from 23 countries, the pooled proportion of polymicrobial infection was 27% (95% CI 22-31%) and was similarly high for bloodstream and pulmonary infections. Polymicrobial infection was variably and insufficiently defined in most (95%) studies. Considerable heterogeneity (I² = 95%) was observed that persisted in subgroup analyses and meta-regressions. Based on 17 studies (2675 infections), polymicrobial infection was associated with lower 28-day mortality (OR = 0.75, 95% CI 0.58-0.98, I² = 36%). However, polymicrobial infection was not associated with in-hospital mortality (OR = 0.97, 95% CI 0.69-1.35, I² = 0%) based on 14 studies (953 infections). The quality of evidence (GRADE) for the association of polymicrobial (vs monomicrobial) infection with mortality was low and at high risk of bias.

CONCLUSION

Polymicrobial ABC infections are common and may be associated with lower 28-day mortality. Considering the heterogeneity of polymicrobial infections and limitations of the available literature, more research is required to clarify the clinical impact of polymicrobial (vs monomicrobial) ABC infection.

Acinetobacter baumannii Infections in Hospitalized Patients, Treatment Outcomes

Background Acinetobacter baumannii (AB), an opportunistic pathogen, could develop into serious infections with high mortality and financial burden. The debate surrounding the selection of effective antibiotic treatment necessitates studies to define the optimal approach. This study aims to compare the clinical outcomes of commonly used treatment regimens in hospitalized patients with AB infections to guide stewardship efforts. Material and methods: Ethical approval was obtained, 320 adult patients with confirmed AB infections admitted to our tertiary care facility within two years were enrolled. The treatment outcomes were statistically analyzed to study the relation between antibiotic regimens and 14, 28, and 90-day mortality as the primary outcomes using binary logistic regression—using R software—in addition to the length of hospitalization, adverse events due to antibiotic treatment, and 90-day recurrence as secondary outcomes. Results: Among 320 patients, 142 (44%) had respiratory tract, 105 (33%) soft tissue, 42 (13%) urinary tract, 22 (7%) bacte iemia, and other infections 9 (3%). Nosocomial infections were 190 (59%) versus community-acquired. Monotherapy was significantly associated with lower 28-day (p < 0.05, OR:0.6] and 90-day (p < 0.05, OR:0.4) mortality rates, shorter length of stay LOS (p < 0.05, Median: −12 days] and limited development of adverse events (p < 0.05, OR:0.4). Subgroup analysis revealed similar results ranging from lower odds of mortality, adverse events, and shorter LOS to statistically significant correlation to monotherapy. Meropenem (MEM) and piperacillin/tazobactam (PIP/TAZ) monotherapies showed non-significant high odd ratios of mortalities, adverse events, and disparate LOS. There was a statistical correlation between most combined therapies and adverse events, and longer LOS. Colistin based and colistin/meropenem (CST/MEM) combinations were superior in terms of 14-day mortality (p = 0.05, OR:0.4) and (p < 0.05, OR:0.4) respectively. Pip/Taz and MEM-based combined therapies were associated with statistically non-significant high odd ratios of mortalities. Tigecycline (TGC)-based combinations showed a significant correlation to mortalities (p < 0.05, OR:2.5). Conclusion: Monotherapy was associated with lower mortality rates, shorter LOS, and limited development of adverse events compared to combined therapies. Colistin monotherapy, colistin/meropenem, and other colistin combinations showed almost equivalent mortality outcomes. Patients on combined therapy were more susceptible to adverse events and comparable LOS. The possible adverse outcomes of PIP/TAZ and MEM-based therapies in the treatment of MDRAB infections and the association of TGC with a higher mortality rate raise doubts about their treatment role.

Oxacillinase Gene Distribution, Antibiotic Resistance, and Their Correlation with Biofilm Formation in Acinetobacter baumannii Bloodstream Isolates

Objectives: The limitations of treatment options in bloodstream infections caused by multidrug-resistant Acinetobacter baumannii (MDRAB) have been related to high morbidity and mortality. The aim of our present study was to determine antimicrobial susceptibility profiles, molecular resistance patterns, and biofilm properties of A. baumannii isolated from bloodstream infections. Materials and Methods: In the present study, a total of 44 A. baumannii bloodstream isolates were included. Antimicrobial susceptibility profiles and biofilm formation ability were assessed. The distribution of class D carbapenemases, ISAba1, ISAba1/blaOXA-23, blaNDM-1, mcr-1, and ompA was investigated by polymerase chain reaction (PCR). Arbitrarily primed-PCR (AP-PCR) was performed to evaluate clonal relationships. Results: A total of 32 isolates were MDRAB, whereas 6 isolates were also resistant to colistin without mcr-1 positivity. All isolates were harboring blaOXA-51 gene, whereas blaOXA-23 positivity was 63.6%. Fifty percent of the isolates had ISAba1. ISAba1 upstream of blaOXA-23 was determined in 18 isolates. None of the isolates were positive for blaNDM-1 gene. Majority of the strains were strong biofilm producers (86.8%). A total of 56.8% of the isolates were positive for ompA gene with no direct association with strong biofilm formation. However, blaOXA-51 + 23 genotype and trimethoprim-sulfamethoxazole resistance showed a significant relationship with biofilm formation. AP-PCR analysis revealed six distinct clusters of A. baumannii. Conclusions: Herein, majority of the A. baumannii blood isolates were characterized as blaOXA-51+OXA-23 carbapenemase genotype and were strong biofilm formers. None of the isolates were positive for blaNDM-1, which was promising. Resistant isolates were tended to form strong biofilms. Our results highlight the emergence of oxacillinase-producing MDRAB isolated from bloodstream with high biofilm formation ability.

Analytical study of biosynthesised silver nanoparticles against multi-drug resistant biofilm-forming pathogens

The emergence of the huge number of multi-drug resistant (MDR) bacteria requires an alternative to the drugs. Silver nanoparticles (AgNPs) are a strong candidate for this due to their bactericidal properties, which can be better concluded by understanding their morphology and chemistry. The study hypothesised that AgNPs synthesised using leaves of Syzygium cumini can be used to treat locally emerging MDRs forming biofilms on indwelling medical devices. Synthesised particles were characterised by methods like UV-visible spectroscopy, X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and Zetasizer. Fourier transform infrared spectroscopy, and high-performance liquid chromatography were used to predict phytochemicals present in the leaves. The shape of particles is revealed to be relatively spherical, with average size to be around 10-100 nm. Phenolic compounds are attributed to the formation of nanoparticles, stability analysis shows particles to be stable, and zeta potential determined the surface charge to be -20.1 mV. Biosynthesised particles are found to possess efficient antibacterial activity MDR bacteria developing biofilms in medical devices; hence, it is concluded that S. cumini based NPs can be used to develop a layer on implant-related medical devices. Toxicity evaluation against A594 cancer cells portrays AgNPs to be potential tumour reduction agents in a concentration-dependent manner.

Acinetobacter baumannii Resistance: A Real Challenge for Clinicians

Acinetobacter baumannii (named in honor of the American bacteriologists Paul and Linda Baumann) is a Gram-negative, multidrug-resistant (MDR) pathogen that causes nosocomial infections, especially in intensive care units (ICUs) and immunocompromised patients with central venous catheters. A. baumannii has developed a broad spectrum of antimicrobial resistance, associated with a higher mortality rate among infected patients compared with other non-baumannii species. In terms of clinical impact, resistant strains are associated with increases in both in-hospital length of stay and mortality. A. baumannii can cause a variety of infections; most involve the respiratory tract, especially ventilator-associated pneumonia, but bacteremia and skin wound infections have also been reported, the latter of which has been prominently observed in the context of war-related trauma. Cases of meningitis associated with A. baumannii have been documented. The most common risk factor for the acquisition of MDR A baumannii is previous antibiotic use, following by mechanical ventilation, length of ICU/hospital stay, severity of illness, and use of medical devices. Current efforts focus on addressing all the antimicrobial resistance mechanisms described in A. baumannii, with the objective of identifying the most promising therapeutic scheme. Bacteriophage- and artilysin-based therapeutic approaches have been described as effective, but further research into their clinical use is required.

Acinetobacter baumannii orofacial cellulitis: report of 2 cases

Acinetobacter baumannii infection of skin and soft tissues is uncommon and usually associated with trauma. The present report describes 2 pediatric cases of cellulitis in the orofacial region, caused by A. baumannii infection with a fatal outcome. A 12-year-old male patient, diagnosed with acute promyelocytic leukemia, presented with an ulcerated lesion on the lip suggestive of local trauma. The condition progressed to cellulitis, epithelial necrosis, and nonspecific vesicles and blisters. The second case occurred in a 10-year-old male patient with a diagnosis of Burkitt lymphoma. The patient's condition progressed to World Health Organization Grade IV mucositis and cellulitis. In both cases, hemoculture was positive for multidrug-resistant A. baumannii. In conclusion, A. baumannii should be considered a potentially multidrug-resistant pathogen in the presence of skin and soft tissue cellulitis. Ulcerated oral lesions may place hospitalized pediatric patients at risk for A. baumannii infection.

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.

Diabetic status and the relationship of blood glucose to mortality in adults with carbapenem-resistant Acinetobacter baumannii complex bacteremia

BACKGROUND/PURPOSE

Diabetes is associated with increased mortality in Acinetobacter baumannii (AB) complex infection. This study investigated the risk factors and relationship of diabetic status and glycemic indices to mortality in patients with carbapenem-resistant (CR) AB complex bacteremia.

METHODS

Relationship of glycemic indices to mortality were compared in adult diabetes (DM) and nondiabetes (non-DM) patients with CRAB complex bacteremia hospitalized from January 2010 to December 2015 in MacKay Memorial Hospital, Taiwan.

RESULTS

Of 317 patients with CRAB complex bacteremia, 146 (46.06%) had diabetes. DM patients were elderly (mean age of 69.23 years) and the mortality rate was higher (64.38% vs. 52.05%, p = 0.036) than in non-DM patients. By multivariate analysis, septic shock was associated with increased mortality in DM patients. Hypoglycemia was associated with increased mortality in non-DM patients only (100% vs. 50.33%, p = 0.006). The lowest mortality was for the blood glucose range 70-100 mg/dL in non-DM patients (43.24%) and 100-140 mg/dL for DM patients (56.52%). Increased glycemic variability (coefficient of variation (CV) > 40% compared to < 20%) was associated with increased mortality in non-DM patients (86.36% vs. 47.12%, p = 0.003).

CONCLUSION

Effects of dysglycemia on mortality due to CRAB complex bacteremia differ according to diabetic status. Mortality was higher in DM patients. In non-DM patients, hypoglycemia and increased CV were associated with increased mortality. The lowest mortality was for the blood glucose range 70-100 mg/dL in non-DM patients and 100-140 mg/dL for DM patients.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Antimicrobial susceptibility, plasmid profiles, and RAPD-PCR typing of Acinetobacter bacteria

Background: Multiple-drug resistant Acinetobacter have widely spread in the last decades imposing a serious nosocomial source of infection. Nevertheless, little knowledge was gaimed on tracing the development of antibiotic resistance in Acinetobacter species. Objectives: Explore Acinetobacter spp. via antimicrobial susceptibility, plasmid profiles, and random amplified polymorphism DNA polymerase chain reaction (RAPD-PCR) typing. Methods: One hundred twelve Acinetobacter isolates (including 66 A. baumannii and 46 non-Acinetobacter baumannii strains) were obtained from three university hospitals. The source of infection of these isolates included blood, urine, wound, and respiratory tract. Their susceptibilities to 17 antibiotics were tested and then all Acinetobacter isolates were typed by plasmid analysis and RAPD-PCR method. Results: A. baumannii isolates revealed nine different patterns of antibiotic resistance. Of those, non- A. baumannii, were associated with plasmid and RAPD-PCR typings (p <0.05). A. baumannii was more resistant to multiple antibiotics than non-A. baumannii (p <0.05). Seven different plasmid profiles were observed among 112 Acinetobacter isolates. Plasmids were found in 107 (95.5%) of the 112 isolates. Unlike in RAPD-PCR typing, there was no difference between the type of Acinetobacter, A. or non-A. baumannii strains and plasmid profiles (p >0.05). By RAPD-PCR, six profiles were found for each A. and non-A. baumannii strains. The pattern 6 was the most common pattern among the isolates. Both plasmid and RAPD-PCR typing showed no association between plasmid profiling and site of infection (p >0.05). Conclusion: There is a wide spread of multi-drug resistant Acinetobacter spp., particularly A. baumannii, in the Middle East region that can be traced efficiently by plasmid and genotyping typing of Acinetobacter. More care should be taken for tracing the development of antimicrobial resistance of Acinetobacter using precise molecular typing techniques.

ERIC-PCR Genotyping of Acinetobacter baumannii Isolated from Different Clinical Specimens

Background:

Acinetobacter baumannii is a major cause of hospital care-acquired infections, and this bacterium poses a significant challenge to health care worldwide. At King Fahd Hospital of the University (KFHU), Al Khobar, Saudi Arabia, there had been a significant increase in the number of cases of A. baumannii infections.

Objective:

The objective of this study was to determine the clonal relationship between A. baumannii collected from different specimens of patients admitted to KFHU using the enterobacterial repetitive intergenic consensus–polymerase chain reaction (ERIC-PCR) fingerprinting method.

Materials and Methods:

A. baumannii strains were isolated from a total of 59 specimens from inpatients admitted to KFHU between January and September 2014. These specimens were mainly collected from wound, rectal and throat swabs and transtracheal aspiration. ERIC-PCR fingerprinting was used to determine the clonal relationship between the different isolated strains.

Results:

Using ERIC-PCR fingerprinting genotype analysis, 51 strains of A. baumannii were clustered into seven groups, while the remaining 8 were single strains. The genetic relatedness of A. baumannii isolated from admitted patients was high, indicating cross-transmission within the hospitalized patients.

Conclusion:

This study found that the increase in the incidence of A. baumannii in patients at KFHU was likely due to the spread of seven epidemic clones, thereby highlighting the need for intensifying the infection control measures to prevent nosocomial transmission of A. baumannii. These results also demonstrate that ERIC-PCR is a reliable and rapid method for studying the clonal similarity between A. baumannii isolated from different clinical specimens.

Biology of Acinetobacter baumannii: Pathogenesis, Antibiotic Resistance Mechanisms, and Prospective Treatment Options

Acinetobacter baumannii is undoubtedly one of the most successful pathogens responsible for hospital-acquired nosocomial infections in the modern healthcare system. Due to the prevalence of infections and outbreaks caused by multi-drug resistant A. baumannii, few antibiotics are effective for treating infections caused by this pathogen. To overcome this problem, knowledge of the pathogenesis and antibiotic resistance mechanisms of A. baumannii is important. In this review, we summarize current studies on the virulence factors that contribute to A. baumannii pathogenesis, including porins, capsular polysaccharides, lipopolysaccharides, phospholipases, outer membrane vesicles, metal acquisition systems, and protein secretion systems. Mechanisms of antibiotic resistance of this organism, including acquirement of β-lactamases, up-regulation of multidrug efflux pumps, modification of aminoglycosides, permeability defects, and alteration of target sites, are also discussed. Lastly, novel prospective treatment options for infections caused by multi-drug resistant A. baumannii are summarized.

Anticipating the Unpredictable: A Review of Antimicrobial Stewardship and Acinetobacter Infections

Acinetobacter remains one of the most challenging pathogens in the field of infectious diseases owing primarily to the uniqueness and multiplicity of its resistance mechanisms. This resistance often leads to devastatingly long delays in time to appropriate therapy and increased mortality for patients afflicted with Acinetobacter infections. Selecting appropriate empiric and definitive antibacterial therapy for Acinetobacter is further complicated by the lack of reliability in commercial antimicrobial susceptibility testing devices and limited breakpoint interpretations for available agents. Existing treatment options for infections due to Acinetobacter are limited by a lack of robust efficacy and safety data along with concerns regarding appropriate dosing, pharmacokinetic/pharmacodynamic targets, and toxicity. Antimicrobial stewardship programs are essential to combat this unpredictable pathogen through use of infection prevention, rapid diagnostics, antibiogram-optimized treatment regimens, and avoidance of overuse of antimicrobials. The drug development pipeline includes several agents with encouraging in vitro activity against Acinetobacter, but their place in therapy and contribution to the armamentarium against this pathogen remain to be defined. The objective of this review is to highlight the unique challenge of treating infections due to Acinetobacter and summarize recent literature regarding optimal antimicrobial treatment for this pathogen. The drug development pipeline is also explored for future potentially effective treatment options.

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

AIM

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

METHODS & RESULTS

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

CONCLUSION

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

Antibiotic Resistance Profiles and Genetic Similarities Within a New Generation of Carbapenem-Resistant Acinetobacter calcoaceticus-A. baumannii Complex Resistotypes in Bosnia and Herzegovina

Acinetobacter calcoaceticus-A. baumannii complex (ACB complex) is a nosocomial pathogen. Due to its high ability to develop antibiotic resistance, it has become a problematic challenge in the modern healthcare system. The molecular and genetic mechanisms of gaining multidrug resistance in ACB complex are well known. This study focuses on providing an overview of the antibiotic resistance profiles, genetic similarities and resistotypes, and general characteristics of carbapenem-resistant ACB complex (CRACB) in Bosnia and Herzegovina (BiH). In light of the data collected in this study, together with the already known information concerning antibiotic resistance of ACB complex, we intend to further elucidate the antibiotic therapy for CRACB strain resistotypes in BiH.

Risk factors and outcomes of hospitalized patients with blood infections caused by multidrug-resistant Acinetobacter baumannii complex in a hospital of Northern China

The purpose of this study was to determine the risk factors and outcomes of bloodstream infections caused by multidrug-resistant (MDR) Acinetobacter baumannii complex in a hospital of Northern China. Risk factors associated with MDR A baumannii complex included older age, pneumonia, using drainage catheters, and intensive care unit stay. Multivariate analysis showed that multidrug resistance and mechanical ventilation were identified as independent risk factors for 30-day mortality in patients with A baumannii complex bacteremia.

Clonal evolution multi-drug resistant Acinetobacter baumannii by pulsed-field gel electrophoresis

BACKGROUND

Acinetobacter baumannii is usually multi-drug resistant (MDR), including third generation cephalosporins, amino glycosides and fluoroquinolone. Resistance to these antibiotics is mediated by multiple factors such as: lactamases, efflux pumps and other mechanisms of resistance. Pulsed-field gel electrophoresis (PFGE) was then used to investigate the genetic relationships among the MDR isolates.

AIM

The aim of this study was to determine MDR isolates and the existence of OXAs genes among MDR isolates of A. baumannii collected from Kermanshah hospitals in west of Iran.

MATERIALS AND METHODS

Forty-two MDR A. baumannii were collected from patients at Kermanshah hospitals. The isolates were identified by biochemical tests and API 20NE kit. The susceptibility to different antibiotics by disk diffusion method was determined. Polymerase chain reaction (PCR) was performed for detection of blaOXA-23-like , blaOXA-24-like , blaOXA-51-like and blaOXA-58-like betalactamase genes in isolates and clonal relatedness was done by PFGE (with the restriction enzyme ApaI) and patterns analyzed by Bionumeric software.

RESULTS

This study showed high resistant to ciprofloxacin, piperacillin, ceftazidime and also resistant to other anti-microbial agents and more spread blaOXA-23-like gene (93%) in MDR isolate. The PFGE method obtained six clones: A (10), B (9), C (5), D (4), E (11) and F (3) that clone E was outbreak and dominant in different wards of hospitals studied.

CONCLUSION

An isolate from the emergency ward of these hospitals had indistinguishable isolates PFGE profile and similar resistance profile to isolates from intensive care unit (ICU), suggesting likely transmission from ICU to emergency via patient or hospital staff contact.

Antibiotic regimens for treatment of infections due to multidrug-resistant Gram-negative pathogens: An evidence-based literature review

Evidences regarding the efficacy of different antibiotic regimens proposed for treatment of multidrug-resistant (MDR) Gram-negative pathogens have been reviewed. Available data in Scopus, Medline, EMBASE, the Cochrane central register of controlled trials, and Cochrane database of systematic reviews have been collected. Several antibiotic regimens are proposed for treatment of MDR Gram-negative infections (defined as nonsusceptibility to at least one agent in three or more antimicrobial categories). The most challenging issue is the treatment of carbapenem-resistant (CR) Gram-negative pathogens. A carbapenem plus either colistin or tigecycline was the most effective regimen for treatment of CR Gram-negative pathogens with low-level resistance (minimal inhibitory concentration [MIC] ≤ 8 mg/L). However, in high-level resistance (MIC > 8 mg/L), combination of colistin and tigecycline showed promising effect.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Trimethoprim/sulfamethoxazole for Acinetobacter spp.: A review of current microbiological and clinical evidence

Clinicians nowadays are confronted with an epidemic of multidrug-resistant (MDR) Acinetobacter infections and are forced to consider every treatment alternative, including older antibiotic agents, not conventionally used. This review aimed to evaluate the published evidence on the antimicrobial activity and clinical effectiveness of trimethoprim/sulfamethoxazole (TMP-SMX) against Acinetobacter spp. Selected in vitro studies included antimicrobial surveillance reports, microbiological studies regarding the activity of TMP-SMX against MDR Acinetobacter isolates, and clinical studies published after the year 2000. Non-susceptibility rates for Acinetobacter spp. in surveillance studies ranged from 4% to 98.2%; in 23 of 28 studies, non-susceptibility to TMP-SMX was >50% and in a subset of 15 studies non-susceptibility was >70%. In studies regarding MDR Acinetobacter spp., non-susceptibility rates ranged from 5.9% to 100%; however, 19 of 21 studies reported >70% non-susceptibility. Extensively drug-resistant Acinetobacter baumannii complex had total (100%) resistance in five of six studies. Carbapenem-resistant Acinetobacter spp. had non-susceptibility rates to TMP-SMX of >80% in 22 of 26 studies. One study on polymyxin-resistant A. baumannii showed a susceptibility rate of 54.2% (13/24). Only seven case reports evaluated TMP-SMX for Acinetobacter spp. infections, mainly in combination with other agents; all cases were deemed therapeutic successes. Although TMP-SMX is not usually active against Acinetobacter spp., it might be considered in cases where there are no other options.

Appropriateness of Antibiotic Prophylaxis for Major Surgery in Korea

Objective.

To determine the appropriateness of antibiotic prophylaxis regimens for major surgery in Korea.

Design.

Retrospective study using a written survey for each patient who underwent arthroplasty, colon surgery, or hysterectomy.

Setting.

Six tertiary hospitals in Seoul and Gyeonggi Province.

Patients.

From each hospital, a maximum of 150 patients who underwent each type of surgery were randomly chosen for the study.

Results.

Of 2,644 eligible patients, 1,914 patients were included in the analysis; 677 of these patients underwent arthroplasty, 578 underwent colon surgery, and 659 underwent hysterectomy. Nineteen patients were excluded from the analyses of the class and number of antibiotics used for prophylaxis because they underwent multiple surgeries at different sites. For each of the 1,895 remaining patients, antibiotic prophylaxis involved a mean ( ± SD) of 2.8 ± 0.9 classes of antibiotics. The most commonly prescribed agents were cephalosporins (prescribed for 1,875 [98.9%] of the patients) and aminoglycosides (1,404 [74.1%]). A total of 1,574 (83.1%) of patients received at least 2 classes of antibiotics simultaneously. Only 15 (0.8%) of 1,895 patients received antibiotic prophylaxis in accordance with published guidelines. Of 506 patients for whom the initial dose of antibiotics was evaluated, 374 (73.9%) received an appropriate initial dose. Of the 1,676 patients whose medical records included information about antibiotic administration relative to the time of surgery, only 188 (11.2%) received antibiotic prophylaxis an hour or less before the surgical incision was made. Of the 1,748 patients whose medical records included information about duration of surgery, antibiotic prophylaxis was discontinued 24 hours or less after surgery for only 3 (0.2%) of the patients.

Conclusion.

Most patients who had major surgery in Korea received inappropriate antibiotic prophylaxis. Measures to improve the appropriateness of antibiotic prophylaxis are urgently required.

Antimicrobial resistance in Acinetobacter baumannii: From bench to bedside

Acinetobacter baumannii (A. baumannii) is undoubtedly one of the most successful pathogens in the modern healthcare system. With invasive procedures, antibiotic use and immunocompromised hosts increasing in recent years, A. baumannii has become endemic in hospitals due to its versatile genetic machinery, which allows it to quickly evolve resistance factors, and to its remarkable ability to tolerate harsh environments. Infections and outbreaks caused by multidrug-resistant A. baumannii (MDRAB) are prevalent and have been reported worldwide over the past twenty or more years. To address this problem effectively, knowledge of species identification, typing methods, clinical manifestations, risk factors, and virulence factors is essential. The global epidemiology of MDRAB is monitored by persistent surveillance programs. Because few effective antibiotics are available, clinicians often face serious challenges when treating patients with MDRAB. Therefore, a deep understanding of the resistance mechanisms used by MDRAB can shed light on two possible strategies to combat the dissemination of antimicrobial resistance: stringent infection control and antibiotic treatments, of which colistin-based combination therapy is the mainstream strategy. However, due to the current unsatisfying therapeutic outcomes, there is a great need to develop and evaluate the efficacy of new antibiotics and to understand the role of other potential alternatives, such as antimicrobial peptides, in the treatment of MDRAB infections.

Risk factors for nosocomial burn wound infection caused by multidrug resistant Acinetobacter baumannii

Acinetobacter baumannii infections in burn patients may lead to delays in wound healing, graft losses, and development of sepsis. Determining the risk factors for multidrug resistant A. baumannii (MDR-AB) infections is essential for infection control. In the present study, the authors aimed to evaluate risk factors for wound infections caused by A. baumannii in burn patients. The study was conducted at Dicle University Hospital Burn Center, from April 2011 to July 2012, to investigate the risk factors for MDR-AB infections. The data of both the case and control group patients and the result of wound cultures were recorded on a daily basis, on individual forms given for each patient, and analyzed. A total of 30 cases infected with MDR-AB, and 60 uninfected control patients, were included in the study. The mean age (±SD) was 7.7 ± 15.4 years in infected patients and 11.4 ± 16.5 years in uninfected patients. The mean total burn surface area was 13.5 ± 10.9% in uninfected patients and 34.7 ± 16.2% in infected patients. The mean total burn surface area, the abbreviated burn severity index, acute physiological and chronic health evaluation II score, day of admission to hospital, length of hospital stay, first excision day, prior usage of third-generation cephalosporins, and stay in intensive care unit of the infected patients were significantly higher (P < .001) than those of patients without infection. Univariate analysis found that high acute physiological and chronic health evaluation II score, first excision time of wound, invasive device usage, admission day to hospital, and prior usage of broad-spectrum antibiotics were risk factors for nosocomial infections. This study showed that multiple factors contribute to multidrug resistance in A. baumannii. A combination of an early diagnosis of wound infections, appropriate antimicrobial treatments, surgical debridement, and early wound closure may be effective in the management.

Update on the Epidemiology, Treatment, and Outcomes of Carbapenem-resistant Acinetobacter infections

Carbapenem-resistant Acinetobacter species are increasingly recognized as major nosocomial pathogens, especially in patients with critical illnesses or in intensive care. The ability of these organisms to accumulate diverse mechanisms of resistance limits the available therapeutic agents, makes the infection difficult to treat, and is associated with a greater risk of death. In this review, we provide an update on the epidemiology, resistance mechanisms, infection control measures, treatment, and outcomes of carbapenem-resistant Acinetobacter infections.

Risk factors and clinical outcome of sulbactam nonsusceptibility in monomicrobial Acinetobacter nosocomialis bacteremia

BACKGROUND

Sulbactam is an effective antimicrobial agent against multidrug-resistant Acinetobacter spp. This retrospective study evaluated the risk factors of sulbactam nonsusceptibility (SNS) in monomicrobial Acinetobacter nosocomialis bacteremia and its related outcome.

METHODS

This 9-year retrospective study included 267 patients who were admitted to a large teaching hospital in Taiwan with monomicrobial A. nosocomialis bacteremia. A. nosocomialis was identified to the species level using molecular methods. Antimicrobial susceptibilities were determined by the agar dilution method. To identify the risk factors of acquiring resistant strains, significant clinical variables derived from univariate analysis were entered into multivariate analysis. Polymerase chain reaction was used to identify blaTEM. Clonality was determined by pulsed-field gel electrophoresis.

RESULTS

A total of 41 of the 267 patients (15.4%) had SNS A. nosocomialis bacteremia. Compared to those with susceptible strains, these patients had higher 14-day mortality (17.1% vs. 7.5%, p = 0.049), were more likely to have higher Acute Physiology and Chronic Health Evaluation (APACHE) II score, were more frequently admitted to the intensive care unit, and had previously received broad-spectrum antibiotics and underwent invasive procedures. In multivariate analysis, the independent risk factors were high APACHE II score and prior use of arterial line [odds ratio (OR), 1.048; 95% confidence interval (CI), 1.007-1.091; p = 0.022 and OR, 2.936; 95% CI, 1.339-6.441; p = 0.007, respectively]. No outbreak was identified and SNS isolates did not harbor blaTEM.

CONCLUSION

For monomicrobial A. nosocomialis bacteremia, the mortality of patients with SNS strains was higher. The SNS strains are more commonly recovered from patients with higher APACHE score and receiving more invasive procedures, especially arterial line.

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

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

Effectiveness and cost of implementing an active surveillance screening policy for Acinetobacter baumannii: a Monte Carlo simulation model

BACKGROUND

Acinetobacter baumannii infections are common and associated with high mortality and costs. Early identification of asymptomatic carriers can reduce patient-to-patient transmission, but the sensitivity of A baumannii surveillance tools is poor, and thus active surveillance is not routine practice. This study examined whether an active surveillance screening policy can reduce the transmission, mortality, and costs associated with A baumannii.

METHODS

A simulation model was developed to determine the impact of active screening on patient outcomes. Model parameters included A baumannii prevalence, screening sensitivity and specificity, probability of transmission, progression from colonization to infection, mortality, and cost of screening, contact precautions, and infection. A scenario analysis was performed to evaluate the robustness of the results when varying the sensitivity of the screening test and the prevalence rate of A baumannii.

RESULTS

Assuming a screening sensitivity of 55%, active screening reduced A baumannii transmissions, infections, and deaths by 48%. As the screening sensitivity approached 90%, the reduction in transmissions, infections, and deaths reached 78%. For all scenarios tested, active surveillance was cost saving (19%-53% reduction in mean hospital cost per patient) except at a carrier prevalence of ≤2% and screening test sensitivity of ≤55%.

CONCLUSIONS

In institutions where A baumannii is endemic or during epidemics, implementing a surveillance program is cost-saving and can greatly reduce transmissions and deaths. Methodologies to improve the sensitivity of surveillance testing will help optimize the clinical impact of active screening programs on preventing the spread of A baumannii in health care facilities.

Clinico-epidemiological nature and antibiotic susceptibility profile of Acinetobacter species

Objectives:Acinetobacter spp. has emerged as an important opportunistic pathogen responsible for nosocomial infections in many health-care settings worldwide. The study describes the clinico-epidemiology and antimicrobial susceptibility of Acinetobacter spp. in a tertiary health-care institution.

Methodology: Acinetobacter spp. were isolated from 141 specimens of the patients who reported to Universiti Kebangsaan Medical Centre (UKMMC). The sources of specimens were wound, skin and soft tissue, respiratory and urinary tract from patients in various wards. Clinio-epidemiological features of patients infected with Acinetobacter spp. were recorded. Standard bacteriological techniques with API 20NE kits and disk diffusion method were followed for identification and antibiotic sensitivity of the organisms.

Results: One hundred and forty one patients with positive culture for Acinetobacter spp. were identified. Soft tissue/wound and respiratory tract were among the commonest sites of Acinetobacter spp. isolation. The isolates were most frequently obtained from ICU. All isolates were multi-drug resistant and had a resistance rate of more than 70% to most antibiotics, except polymyxin B.

Conclusion: High prevalence of multi-drug resistance Acinetobacter spp. provides essential information on judicious antibiotic selection for empirical therapy in our health-care institution.

The role of antimicrobial stewardship in curbing carbapenem resistance

Antimicrobial resistance is a continuing, growing, worldwide iatrogenic complication of modern medical care. Carbapenem resistance among certain pathogens poses a significant challenge. In order to reduce the spread of these nearly untreatable pathogens, preventative efforts should be directed at reducing patient-to-patient transmission and preventing the emergence of resistance among susceptible strains. One theoretical intervention to reduce the emergence of resistance is establishing and strictly adhering to an antimicrobial stewardship program. However, data pertaining to the direct effect of stewardship in curtailing carbapenem resistance among epidemiologically significant organisms are scarce. In this report, we review the potential biases associated with data interpretation in this research field, and we review the data pertaining to the impact of stewardship in curbing carbapenem resistance in three significant groups of pathogens: Pseudomonas aeruginosa, Enterobacteriaceae and Acinetobacter baumannii.

Anti-inflammatory and anti-superbacterial activity of polyphenols isolated from black raspberry

The fruit of the black raspberry (Rubus coreanus Miquel) has been employed in traditional medicine, and recent studies have demonstrated its measureable biological activities. However, the root of the black raspberry has not been studied. Therefore, in this study, we evaluated the anti-inflammatory and antibacterial properties of the root and unripe fruit polyphenols of the black raspberry. Both polyphenols proved to have anti-inflammatory activity as evidenced by the decreased nitric oxide (NO), cytokines (IL-1β , IL-6, and IL-10) and prostaglandin E2 (PGE₂) levels in lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophages. However, root polyphenols showed stronger anti-inflammatory activity than fruit polyphenols. LPS-induced mRNA and protein expressions of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2 levels were also decreased, confirming the anti-inflammatory activity. Root polyphenols showed lethal activity against methicillin-resistant Staphylococcus aureus (MRSA), carbapenem-resistant Acinetobacter baumannii (CRAB), and Bacillus anthracis. In contrast, the black raspberry fruit did not demonstrate these properties. These data provide the first demonstration that black raspberry root has potential anti-inflammatory and anti-superbacterial properties that can be exploited as alternatives for use in the food and cosmetic industries and/or as pharmaceuticals.

Increase of carbapenem-resistant Acinetobacter baumannii infection in acute care hospitals in Taiwan: association with hospital antimicrobial usage

Objective

Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as an important pathogen causing healthcare-associated infections (HAIs) in Taiwan. The present study is aimed to investigate the epidemiology of HAIs caused by CRAB and the association of CRAB infection and hospital usage of different antimicrobials.

Methods

Two nationwide databases in the period 2003 to 2008, the Taiwan Nosocomial Infection Surveillance System and National Health Insurance claim data, were used for analysis. A total of 13,811 healthcare-associated A. baumannii infections and antimicrobial usage data from 121 hospitals were analyzed.

Results

There was a significant increase in the proportion of number of HAIs caused by CRAB over that by all A. baumannii (CRABpAB), from 14% in 2003 to 46% in 2008 (P<0.0001). The greatest increase was in central Taiwan, from 4% in 2003 to 62% in 2008 (P<0.0001). Use of anti-pseudomonal carbapenems, but not other classes of antibiotics, was significantly correlated with the increase of CRABpAB (r = 0.86, P<0.0001).

Conclusions

We suggested that dedicated use of anti-pseudomonal carbapenems would be an important intervention to control the increase of CRABpAB.

Emergence of resistance to carbapenems in Acinetobacter baumannii in Europe: clinical impact and therapeutic options

Despite having a reputation of low virulence, Acinetobacter baumannii is an emerging multidrug-resistant (MDR) pathogen responsible for community- and hospital-acquired infections that are difficult to control and treat. Interest in this pathogen emerged about one decade ago because of its natural MDR phenotype, its capability of acquiring new mechanisms of resistance and the existence of nosocomial outbreaks. Recent advances in molecular biology, including full genome sequencing of several A. baumannii isolates, has led to the discovery of the extraordinary plasticity of their genomes, which is linked to their great propensity to adapt to any environment, including hospitals. In this context, as well as the increasing antimicrobial resistance amongst A. baumannii isolates to the last-line antibiotics carbapenems and colistin, therapeutic options are very limited or absent in some cases of infections with pandrug-resistant bacteria. However, a large proportion of patients may be colonised by such MDR bacteria without any sign of infection, leading to a recurrent question for clinicians as to whether antibiotic treatment should be given and will be effective in the presence of resistance mechanisms. The worldwide emergence of A. baumannii strains resistant to colistin is worrying and the increasing use of colistin to treat infections caused by MDR bacteria will inevitably increase the recovery rate of colistin-resistant isolates in the future. Current knowledge about A. baumannii, including biological and epidemiological aspects as well as resistance to antibiotics and antibiotic therapy, are reviewed in this article, in addition to therapeutic recommendations.

Laboratory evaluation of the ESwab transport system for the recovery of carbapenem-resistant Acinetobacter baumannii

Microbiological surveillance for detection of carbapenem-resistant A. baumannii is important, but recovery of A. baumannii is inadequate. We studied A. baumannii recovery by a particular transport system that is possibly superior over standard swabs, using reference and clinical strains. First, the recovery rates relating to the various swabs were compared with regard to various combinations of transport times (0 h, 1 h, 24 h, 48 h), storage times (0 weeks, 1 week, 2 weeks, 4 weeks) and storage temperatures (4°c,-80°c) using live counts. Second, the recovery of different inocula of strains mixed with fecal microbiota was evaluated by plating on selective medium. The new transport system exhibited a decline of <3log10 under almost all conditions studied and performed better than standard swabs under several conditions. If plated on selective media, the new transport system performed well, even after prolonged transport or with a low inoculum, and its processing could be delayed by up to 2 weeks, especially if refrigerated. The new transport system may thus enhance A. baumannii surveillance.

The probability of the Acinetobacter baumannii strain clonal spreading in donor-recipient systems, as confirmed by the molecular analysis of randomly amplified polymorphic DNA

Acinetobacter baumannii is an important pathogen widely distributed in the hospital environment and responsible for a variety of nosocomial infections. This micro-organism especially affects patients with impaired host defenses in the intensive care unit. It has been implicated in severe nosocomial infections including bloodstream infections, pneumonia, and meningitides. Those infections are often outbreaks caused by a single clone spreading. The aim of our study was an epidemiological analysis of Acinetobacter baumannii strains isolated from hospitalized liver/kidney transplant donors and recipients. The analyzed material for epidemiological test included 13 A. baumannii strains isolated in 2010 from eight liver/kidney donors and 5 organ recipients. The epidemiological analysis of the isolates was performed by the use of the random amplified polymorphic DNA (RAPD)-polymerase chain reaction method to determine their genetic relatedness. We isolated 9 A. baumannii strains from 8 organ donors. Among this group of isolates, four strains showed the same fingerprints that were classified as one RAPD type 1. The remaining donor isolates revealed differentiated patterns. All strains isolated from recipients formed distinct RAPD types, one of which was identical to the group of four donor strains (RAPD type 1). The clonal spreading of A. baumannii strains was not observed among recipients but we noted a single case of probable transmission of the pathogen from the donor to the recipient.

Incidence and outcome of healthcare-associated Acinetobacter baumannii in chronically ventilated patients in a tertiary care hospital in Taiwan

INTRODUCTION

Most studies related to healthcare-associated infection with Acinetobacter baumannii (HAIA) are on acutely ventilated patients. Little is known regarding the incidence and outcomes of HAIA in chronically ventilated patients.

METHODS

A retrospective study of chronically ventilated patients covering the period May 2002 to May 2008 was conducted to determine the incidence of patients with HAIA. The Cox proportional hazard model was used to estimate differences in the 30-day mortality between those with and those without HAIA by case-control study after controlling for confounders.

RESULTS

Of 240 patients who were chronically ventilated for 49,207 days, 78 (32.5%) acquired HAIA at a rate of 1.59/1,000 patient day. The central venous catheter-related bloodstream infections rate was 8.78 per 1,000 catheter days; the ventilator-associated pneumonia rate was 1.26 per 1,000 ventilator days; and the catheter-associated urinary tract infections rate was 0.17 per 1,000 catheter days. Fifty (64.1%) HAIA and 58 (64.4%) non-HAIA patients were treated well and survived without ICU admission. After univariate and multivariate analyses, prolonged ventilation days (odds ratio: 3.4; 95% confidence interval: 1.7-6.1; P = 0.01] and inappropriate empiric antibiotics within 48 hours (odds ratio: 7.9; 95% confidence interval: 3.9-9.8; P = 0.02) were independent factors that predicted the 30-day mortality of HAIA among chronically ventilated patients.

CONCLUSIONS

Although chronically ventilated patients with HAIA have longer ventilator days, higher antibiotics resistance, and high rate per 100 patients of ventilator-associated pneumonia, most patients are treated well. Compared with patients without HAIA, prolonged ventilation days and inappropriate empiric antibiotics within 48 hours are independent factors of the 30-day mortality.