Determinants of Mortality in Patients with Nosocomial Acinetobacter baumannii Bacteremia in Southwest China: A Five-Year Case-Control Study

Co-regulation of biofilm formation and antimicrobial resistance in Acinetobacter baumannii: from mechanisms to therapeutic strategies

In recent years, multidrug-resistant Acinetobacter baumannii has emerged globally as a major threat to the healthcare system. It is now listed by the World Health Organization as a priority one for the need of new therapeutic agents. A. baumannii has the capacity to develop robust biofilms on biotic and abiotic surfaces. Biofilm development allows these bacteria to resist various environmental stressors, including antibiotics and lack of nutrients or water, which in turn allows the persistence of A. baumannii in the hospital environment and further outbreaks. Investigation into therapeutic alternatives that will act on both biofilm formation and antimicrobial resistance (AMR) is sorely needed. The aim of the present review is to critically discuss the various mechanisms by which AMR and biofilm formation may be co-regulated in A. baumannii in an attempt to shed light on paths towards novel therapeutic opportunities. After discussing the clinical importance of A. baumannii, this critical review highlights biofilm-formation genes that may be associated with the co-regulation of AMR. Particularly worthy of consideration are genes regulating the quorum sensing system AbaI/AbaR, AbOmpA (OmpA protein), Bap (biofilm-associated protein), the two-component regulatory system BfmRS, the PER-1 β-lactamase, EpsA, and PTK. Finally, this review discusses ongoing experimental therapeutic strategies to fight A. baumannii infections, namely vaccine development, quorum sensing interference, nanoparticles, metal ions, natural products, antimicrobial peptides, and phage therapy. A better understanding of the mechanisms that co-regulate biofilm formation and AMR will help identify new therapeutic targets, as combined approaches may confer synergistic benefits for effective and safer treatments.

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.

Prevalent Dominant Acinetobacter baumannii ST191/195/208 Strains in Bloodstream Infections Have High Drug Resistance and Mortality

Background

Different sequence types of Acinetobacter baumannii (AB) have their own epidemiological characteristics, drug resistance, and toxicity.

Methods

AB bloodstream infection (BSI) in the First Affiliated Hospital of Medical College of Zhejiang University from January 2012 to December 2017 were classified by multilocus sequence typing. Clinical data of patients were retrospectively analyzed, drug resistance and toxicity were respectively studied by drug sensitivity and complement killing tests.

Results

247 unduplicated AB strains were collected, and ST191/195/208, the main epidemic dominant strain, accounted for 70.9%. Patients with ST191/195/208 on infection had higher white blood cell (10.8 vs 8.9, p = 0.004), neutrophil% (89.5 vs 86.9, p = 0.005), neutrophil count (9.5 vs 7.1, p = 0.021), D-dimer (6.7 vs 3.8, p = 0.000), total bilirubin (27.0 vs 21.5, p = 0.038), pronatriuretic peptide (324 vs 164, p = 0.042), C-reactive protein (82.5 vs 56.3, p = 0.048), clinical pulmonary infection score (CPIS; 7.33 ± 2.30 vs 6.50 ± 2.72, p = 0.045), and acute physiology and chronic health evaluation-II (APACHE-II; 19.620 ± 5.1850 vs 17.648 ± 6.1251, p = 0.011). Patients with ST191/195/208 had more complications, including pulmonary infection (p = 0.041), septic shock (p = 0.009), and multiple organ failure (p = 0.019). Patients with ST191/195/208 had higher 3 day mortality (24.6% vs 13.9%, p = 0.043), 14 day mortality (46.8% vs 26.8%, p = 0.003), and 28 day mortality (55.0% vs 32.4%, p = 0.001). ST191/195/208 strains had higher drug resistance to most antibiotics, and higher survival rate at 90% normal serum concentration (p < 0.001).

Conclusion

ST191/195/208 strains predominate in the hospital and prevails in patients with severe infections with increased multidrug antimicrobial resistance and excessive mortality compared to any other AB stains.

Routine laboratory biomarkers used to predict Gram-positive or Gram-negative bacteria involved in bloodstream infections

This study evaluated routine laboratory biomarkers (RLB) to predict the infectious bacterial group, Gram-positive (GP) or Gram-negative (GN) associated with bloodstream infection (BSI) before the result of blood culture (BC). A total of 13,574 BC of 6787 patients (217 BSI-GP and 238 BSI-GN) and 68 different RLB from these were analyzed. The logistic regression model was built considering BSI-GP or BSI-GN as response variable and RLB as covariates. After four filters applied total of 320 patients and 16 RLB remained in the Complete-Model-CM, and 4 RLB in the Reduced-Model-RM (RLB p > 0.05 excluded). In the RM, only platelets, creatinine, mean corpuscular hemoglobin and erythrocytes were used. The reproductivity of both models were applied to a test bank of 2019. The new model presented values to predict BSI-GN of the area under the curve (AUC) of 0.72 and 0.69 for CM and RM, respectively; with sensitivity of 0.62 and 0.61 (CM and RM) and specificity of 0.67 for both. These data confirm the discriminatory capacity of the new models for BSI-GN (p = 0.64). AUC of 0.69 using only 4 RLB, associated with the patient's clinical data could be useful for better targeted antimicrobial therapy in BSI.

Multidrug-Resistant Bacteria: Their Mechanism of Action and Prophylaxis

In the present scenario, resistance to antibiotics is one of the crucial issues related to public health. Earlier, such resistance to antibiotics was limited to nosocomial infections, but it has now become a common phenomenon. Several factors, like extensive development, overexploitation of antibiotics, excessive application of broad-spectrum drugs, and a shortage of target-oriented antimicrobial drugs, could be attributed to this condition. Nowadays, there is a rise in the occurrence of these drug-resistant pathogens due to the availability of a small number of effective antimicrobial agents. It has been estimated that if new novel drugs are not discovered or formulated, there would be no effective antibiotic available to treat these deadly resistant pathogens by 2050. For this reason, we have to look for the formulation of some new novel drugs or other options or substitutes to treat such multidrug-resistant microorganisms (MDR). The current review focuses on the evolution of the most common multidrug-resistant bacteria and discusses how these bacteria escape the effects of targeted antibiotics and become multidrug resistant. In addition, we also discuss some alternative mechanisms to prevent their infection as well.

Isolation and Characterization of a Novel Siphoviridae Phage, vB_AbaS_TCUP2199, Infecting Multidrug-Resistant Acinetobacter baumannii

Multidrug-resistant Acinetobacter baumannii (MDRAB) is a pathogen recognized as antimicrobial-resistant bacteria involved in healthcare-associated infections. Resistance to antibiotics has made alternative therapies necessary. Bacteriophage therapy is considered a potential solution to treat MDRAB. In this study, we isolated and characterized the phage vB_AbaS_TCUP2199 (TCUP2199), which can infect MDRAB. Morphological analysis revealed that TCUP2199 belongs to the Siphoviridae family. TCUP2199 has a wide host range, can adsorb rapidly (68.28% in 2 min), and has a burst size of 196 PFU/cell. At least 16 distinct structural proteins were visualized by SDS polyacrylamide gel electrophoresis. A stability test showed that TCUP2199 was stable at 37 °C and pH 7. Genome analysis of TCUP2199 showed that it consists of a double-stranded DNA genome of 79,572 bp with a G+C content of 40.39%, which contains 98 putative open reading frames, none of which is closely related to the bacteriophage genome sequence that was found in the public database. TCUP2199 shows similarity in genomic organization and putative packaging mechanism with Achromobacter phage JWF and Pseudoalteromonas phage KB12-38 based on protein BLAST and phylogenetic analysis. Because of those unique characteristics, we consider TCUP2199 to be a novel phage that is suitable for inclusion in a phage cocktail to treat A. baumannii infection.

A Short Peptide of Autotransporter Ata Is a Promising Protective Antigen for Vaccination Against Acinetobacter baumannii

With the emergence of multidrug-resistant strains, Acinetobacter baumannii infection is becoming a thorny health problem in hospitals. However, there are no licensed vaccines against A. baumannii. Acinetobacter trimeric autotransporter (Ata) is an important known virulence factor located on the outer membrane of bacteria. Herein, we carried out a series of experiments to test the immunogenicity of a short C-terminal extracellular region of Ata (Ataα, only containing 39 amino acids) in a murine model. The short peptide Ataα was fused with the cholera toxin B subunit (CTB), which has been reported to have immunoadjuvant activity. The fusion protein showed no inflammation and organ damages, and have the ability to elicit both Th1 and Th2 immune responses in mice. The bactericidal activities against A. baumannii and prophylactic effects of the fusion protein were further evidenced by a significant reduction in the bacterial load in the organs and blood. In addition, the candidate vaccine could provide broad protection against lethal challenges with a variety of A. baumannii strains. Moreover, when CpG was added on the basis of aluminum adjuvant, the immune response, especially cellular immunity, could be further strengthened. Overall, these results revealed that the Ataα is a promising vaccine target against A. baumannii infection.

Treatment, clinical outcomes, and predictors of mortality among a national cohort of admitted patients with Acinetobacter baumannii infection

Objectives: To analyze treatment, clinical outcomes, and predictors of mortality in hospitalized patients with Acinetobacter baumannii infection.

Methods: Retrospective cohort study of inpatients with A. baumannii cultures and treatment from 2010-2019. Patients who died during admission were compared to those who survived to identify predictors of inpatient mortality, using multivariable unconditional logistic regression models.

Results: We identified 4,599 inpatients with A. baumannii infection; 13.6% died during admission. Fluoroquinolones (26.8%), piperacillin/tazobactam (24%) and carbapenems (15.6%) were used for treatment. Tigecycline (3%) and polymyxins (3.7%) were not used often. Predictors of inpatient mortality included current acute respiratory failure (adjusted odds ratio [aOR] 3.94), shock (aOR 3.05), and acute renal failure (aOR 2.01); blood (aOR 1.94) and respiratory (aOR 1.64) infectious source; multidrug-resistant A. baumannii (MDRAB) infection (aOR 1.66); liver disease (aOR 2.15); and inadequate initial treatment (aOR 1.30). Inpatient mortality was higher in those with MDRAB vs. non-MDRAB (aOR 1.61) and in those with CRAB vs. non-CRAB infection (aOR 1.68). Length of stay >10 days was higher among those with MDRAB vs. non-MDRAB (aOR 1.25) and in those with CRAB vs. non-CRAB infection (aOR 1.31).

Conclusions: In our national cohort of inpatients with A. baumannii infection, clinical outcomes were worse among those with MDRAB and/or CRAB infection. Predictors of inpatient mortality included several current conditions associated with severity, infectious source, underlying illness, and inappropriate treatment. Our study may assist healthcare providers in the early identification of admitted patients with A. baumannii infection who are at higher risk of death.

Deciphering Multidrug-Resistant Acinetobacter baumannii from a Pediatric Cancer Hospital in Egypt

Infection by multidrug-resistant (MDR) Acinetobacter baumannii is one of the major causes of hospital-acquired infections worldwide. The ability of A. baumannii to survive in adverse conditions as well as its extensive antimicrobial resistance make it one of the most difficult to treat pathogens associated with high mortality rates. The aim of this study was to investigate MDR A. baumannii that has spread among pediatric cancer patients in the Children’s Cancer Hospital Egypt 57357. Whole-genome sequencing was used to characterize 31 MDR A. baumannii clinical isolates. Phenotypically, the isolates were MDR, with four isolates showing resistance to the last-resort antibiotic colistin. Multilocus sequence typing showed the presence of eight clonal groups, two of which were previously reported to cause outbreaks in Egypt, and one novel sequence type (ST), Oxf-ST2246. Identification of the circulating plasmids showed the presence of two plasmid lineages in the isolates, strongly governed by sequence type. A large number of antimicrobial genes with a range of resistance mechanisms were detected in the isolates, including β-lactamases and antibiotic efflux pumps. Analysis of insertion sequences (ISs) revealed the presence of ISAba1 and ISAba125 in all the samples, which amplify β-lactamase expression, causing extensive carbapenem resistance. Mutation analysis was used to decipher underlying mutations responsible for colistin resistance and revealed novel mutations in several outer membrane proteins, in addition to previously reported mutations in pmrB. Altogether, understanding the transmissibility of A. baumannii as well as its resistance and virulence mechanisms will help develop novel treatment options for better management of hospital-acquired infections.

IMPORTANCEAcinetobacter baumannii represents a major health threat, in particular among immunocompromised cancer patients. The rise in carbapenem-resistant A. baumannii, and the development of resistance to the last-resort antimicrobial agent colistin, complicates the management of A. baumannii outbreaks and increases mortality rates. Here, we investigate 31 multidrug resistant A. baumannii isolates from pediatric cancer patients in Children’s Cancer Hospital Egypt (CCHE) 57357 via whole-genome sequencing. Multilocus sequence typing (MLST) showed the presence of eight clonal groups including a novel sequence type. In silico detection of antimicrobial-resistant genes and virulence factors revealed a strong correlation between certain virulence genes and mortality as well as several point mutations in outer membrane proteins contributing to colistin resistance. Detection of CRISPR/Cas sequences in the majority of the samples was strongly correlated with the presence of prophage sequences and associated with failure of bacteriophage therapy. Altogether, understanding the genetic makeup of circulating A. baumannii is essential for better management of outbreaks.

Adverse clinical outcomes associated with carbapenem-resistant Acinetobacter (CRA) infections: a systematic review and meta-analysis

Background

Carbapenem-resistant Acinetobacter (CRA) infections have been associated with increased morbidity and mortality in hospitalized patients. This systematic review and meta-analysis aimed to quantify the association between CRA infections and adverse clinical outcomes.

Methods

Three databases (i.e. PubMed, EMBASE and Scopus) were searched for epidemiological studies that compared mortality, severe sepsis or shock, or bacteraemia among adult inpatients with CRA infections and those with carbapenem-susceptible Acinetobacter (CSA) infections. The pooled ORs for the three outcomes were estimated using the inverse variance heterogeneity model.

Results

Thirty-four studies were included. Patients with CRA infections had higher odds of mortality (31 studies, OR = 2.10, 95% CI: 1.58–2.79, I²=60.6%) and severe sepsis or septic shock (7 studies, OR = 1.51, 95% CI: 1.09–2.09, I²=0%) compared with CSA-infected patients. There was no difference in the odds of bacteraemia (four studies, OR = 1.39, 95% CI: 0.79–2.46, I²=38.1%). CRA-infected patients presented with worse comorbidity at admission (e.g. APACHE score) (eight studies, standardized mean difference = 0.25, 95% CI: −0.01 to 0.52) and had lower frequency of appropriate antibiotic therapy. Results were consistent when pooling 16 study-adjusted risk estimates for mortality. There was no difference in risk of mortality from CRA infection when compared across geographical regions, country income, median year of enrolment and day of mortality from infection onset.

Conclusions

CRA-infected patients had worse clinical outcomes. This might be due to delay in appropriate antibiotic therapy, patients being sicker at admission and CRA strains potentially being more virulent than CSA strains. Improving appropriateness of antibiotic therapy in CRA-infected patients could reduce adverse clinical outcomes.

Prospective multi-center evaluation on risk factors, clinical characteristics and outcomes due to carbapenem resistance in Acinetobacter baumannii complex bacteraemia: experience from the Chinese Antimicrobial Resistance Surveillance of Nosocomial Infections (CARES) Network

Introduction. Increasing evidence demonstrates unfavourable outcomes in bloodstream infections (BSI) due to the carbapenem-resistant Acinetobacter baumannii complex (CRAB).Aim. To investigate the differences in risk factors, clinical characteristics and outcomes in patients with A. baumannii complex BSI stratified by carbapenem resistance, a prospective multi-center study was conducted.Methodology. Information was collected in a predefined form. A total of 317 cases was included for comparison between CRAB BSI vs. carbapenem-susceptible A. baumannii complex (CSAB) BSI. Among these cases, 229 cases were defined as CRAB BSI and 88 cases as CSAB BSI.Results. Univariable analysis showed that male gender, underlying neurologic disease, prior carbapenems exposure, intensive care unit (ICU) stay, presence of central venous catheter, endotracheal intubation, tracheotomy, Foley catheter, nasogastric intubation, lower respiratory tract infections and catheter-related infections were more prevalent in CRAB BSI. Only male gender, prior carbapenems exposure and presence of endotracheal intubation persisted as independent risk factors for acquiring CRAB BSI. Patients with CRAB BSI displayed unfavourable outcomes characterized by failure of pathogen clearance, continuous fever, disease aggravation and higher incidence of 30-day all-cause mortality. Multivariate analysis demonstrated carbapenem resistance as an independent risk factor for 30-day all-cause mortality.Conclusion. Our findings reveal the epidemiological differences between CRAB BSI and CSAB BSI in a Chinese cohort. Our data suggest that carbapenem resistance has a significant impact on mortality for patients with A. baumannii complex BSI, further strengthening the importance of active prevention and control strategies for the spread of CRAB in Chinese hospitals.

Clinical and Economic Burden of Carbapenem-Resistant Infection or Colonization Caused by Klebsiella pneumoniae, Pseudomonas aeruginosa, Acinetobacter baumannii: A Multicenter Study in China

Background: Carbapenem resistant Klebsiella pneumoniae (CRKP), Pseudomonas aeruginosa (CRPA), and Acinetobacter baumannii (CRAB) pose significant threats to public health. However, the clinical and economic impacts of CRKP, CRPA, and CRAB remain largely uninvestigated in China. This study aimed to examine the clinical and economic burden of CRKP, CRPA, and CRAB compared with carbapenem susceptible cases in China. Method: We conducted a retrospective and multicenter study among inpatients hospitalized at four tertiary hospitals between 2013 and 2015 who had K. pneumoniae, P. aeruginosa, and A. baumannii positive clinical samples. Propensity score matching (PSM) was used to balance the impact of potential confounding variables, including age, sex, insurance, number of diagnosis, comorbidities (disease diagnosis, and Charlson comorbidity index), admission to intensive care unit, and surgeries. The main indicators included economic costs, length of stay (LOS), and mortality rate. Results: We included 12,022 inpatients infected or colonized with K. pneumoniae, P. aeruginosa, and A. baumannii between 2013 and 2015, including 831 with CRKP and 4328 with carbapenem susceptible K. pneumoniae (CSKP), 1244 with CRPA and 2674 with carbapenem susceptible P. aeruginosa (CSPA), 1665 with CRAB and 1280 with carbapenem susceptible A. baumannii (CSAB). After PSM, 822 pairs, 1155 pairs, and 682 pairs, respectively were generated. Compared with carbapenem-susceptible cases, those with CRKP, CRPA, and CRAB were associated with statistically significantly increased total hospital cost ($14,252, p < 0.0001; $4605, p < 0.0001; $7277, p < 0.0001) and excess LOS (13.2 days, p < 0.0001; 5.4 days, p = 0.0003; 15.8 days, p = 0.0004). In addition, there were statistically significantly differences in hospital mortality rate between CRKP and CSKP, and CRAB and CSAB group (2.94%, p = 0.024; 4.03%, p = 0.03); however, the difference between CRPA and CSPA group was marginal significant (2.03%, p = 0.052). Conclusion: It highlights the clinical and economic impact of CRKP, CRPA, and CRAB to justify more resources for implementing antibiotic stewardship practices to improve clinical outcomes and to reduce economic costs.

Multidrug resistant and extensively drug resistant Acinetobacter baumannii hospital infection associated with high mortality: a retrospective study in the pediatric intensive care unit

Background

Multidrug resistant (MDR) and extensively drug resistant (XDR) Acinetobacter baumannii presents challenges for clinical treatment and causes high mortality in children. We aimed to assess the risk factors and overall mortality for MDR/XDR Acinetobacter baumannii infected pediatric patients.

Methods

This retrospective study included 102 pediatric patients who developed MDR/XDR Acinetobacter baumannii infection in the pediatric intensive care unit (PICU) of Shanghai Children’s Hospital in China from December 2014 to May 2018.

Acinetobacter baumannii clinical isolates were recovered from different specimens including blood, sputum, bronchoalveolar lavage fluid, cerebrospinal fluid, ascites, hydrothorax, and urine. Antibiotic susceptibility test was determined according to the Clinical and Laboratory Standards Institute interpretive criteria. Clinical and biological data were obtained from the patients’ medical records.

Results

102 patients with Acinetobacter baumannii infection were enrolled. The median age was 36 (9.6, 98.8) months, and there were 63 male in the case group. The overall mortality rate was 29.4%, while the Acinetobacter baumannii-associated mortality rate was 16.7% (17/102, 12 bloodstream infections, 4 meningitis and 1 intra-abdominal infection). Bloodstream infections occurred in 28 patients (27.5%), and 10 patients (9.8%) among them had central line-associated bloodstream infections (6 central venous catheters, 2 PICCs, 1 venous infusion port and 1 arterial catheter). Cerebrospinal fluid (CSF) cultures were positive in 4(3.9%) patients. 14(13.7%) patients got positive cultures in ascites and hydrothorax. Lower respiratory isolates (56/102) accounted for 54.9% of all patients. Non-survival patients appeared to have a lower NK cell activity (6.2% ± 3.61% vs. 9.15% ± 6.21%, P = 0.029), higher CD4+ T cell ratio (39.67% ± 12.18% vs. 32.66% ± 11.44%, P = 0.039),and a higher serum level of interlukin-8 (IL-8, 15.25 (1.62, 47.22)pg/mL vs. 0.1 (0.1, 22.99)pg/mL, P = 0.01) when Acinetobacter baumannii infection developed. Multivariate logistic analysis indicated that high serum level of Cr (RR, 0.934, 95%CI, 0.890–0.981; P = 0.007) and high BUN/ALB level (RR, 107.893, 95%CI, 1.425–870.574; p = 0.005) were associated with high risk of mortality in MDR/XDR Acinetobacter baumannii infected patients.

Conclusion

MDR/XDR Acinetobacter baumannii infection is a serious concern in pediatric patients with high mortality. Bloodstream and central nervous system infection accounted for high risk of death. Acute kidney injury is associated with high risk of mortality.

Development and Validation of a Model for Predicting the Risk of Death in Patients with Acinetobacter baumannii Infection: A Retrospective Study

Purpose

This study aimed to develop and validate a personalized prediction model of death risk in patients with Acinetobacter baumannii (A. baumannii) infection and thus guide clinical research and support clinical decision-making.

Patients and Methods

The development group is comprised of 350 patients with A. baumannii infection admitted between January 2013 and December 2015 in The First Affiliated Hospital of Anhui Medical University. Further, 272 patients in the validation group were admitted between January 2016 and December 2018. The univariate and multivariate logistic regression analyses were used to determine the independent risk factors for death with A. baumannii infection. The nomogram prediction model was established based on the regression coefficients. The discrimination of the proposed prediction model was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curves and decision curve analysis (DCA). The calibration diagram was used to evaluate the calibration degree of this model.

Results

The infectious source, carbapenem-resistant A. baumannii (CRAB), hypoalbuminemia, Charlson comorbidity index (CCI), and mechanical ventilation (MV) were independent risk factors for death. The AUC of the ROC curve of the two groups was 0.768 and 0.792, respectively. The net income was higher when the probability was between 30% and 80%, showing a strong discrimination capacity of the proposed model. The calibration curve swung around the 45° oblique line, indicating a high degree of calibration.

Conclusion

The proposed model helped predict the risk of death from A. baumannii infection, improve the early identification of patients with a higher risk of death, and guide clinical treatment.

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Prevalence of multi-drug resistant (MDR) and extensively drug-resistant (XDR) phenotypes of Pseudomonas aeruginosa and Acinetobacter baumannii isolated in clinical samples from Northeast of Iran

OBJECTIVE

Multi and extensively drug-resistant (MDR and XDR), Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii) are two main causative agents of nosocomial infections leading to increased morbidity and mortality. We aim to study the prevalence of MDR and XDR-A. baumannii and P. aeruginosa phenotypes in clinical specimens. We conducted this for 1 year (2017-2018) and isolated bacteria from the clinical samples. Then, XDR and MDR strains were determined by susceptibility testing (disc diffusion).

RESULTS

Out of 3248 clinical samples, A. baumannii and P. aeruginosa strains were detected in 309(9.51%) of them. Susceptibility testing indicated that (16.50%) and (15.53%) of the P. aeruginosa and (74.75%) and (73.13%) of the A. baumannii isolates were screened as the MDR and XDR strains. The frequency of MDR isolates was higher in wound samples 222 (71.8%). This rate in behavioral intensive care unit (BICU) and restoration ward, were 187 (60.5%) and 63 (20.4%). The frequency of XDR isolates in BICU 187 (59.54%), restoration 58(18.77%), and burns 30 (9.70%) were assessed as well. Considering high isolation rates of MDR and XDR of mentioned strains, it is necessary to apply prevention criteria for eradication of the mentioned bacteria from hospital wards.

High mortality in an outbreak of multidrug resistant Acinetobacter baumannii infection introduced to an oncological hospital by a patient transferred from a general hospital

OBJECTIVE

To describe the clinical features, outcomes, and molecular epidemiology of an outbreak of multidrug resistant (MDR) A. baumannii.

METHODS

We performed a retrospective analysis of all MDR A. baumannii isolates recovered during an outbreak from 2011 to 2015 in a tertiary care cancer hospital. Cases were classified as colonized or infected. We determined sequence types following the Bartual scheme and plasmid profiles.

RESULTS

There were 106 strains of A. baumannii isolated during the study period. Sixty-six (62.3%) were considered as infection and 40 (37.7%) as colonization. The index case, identified by molecular epidemiology, was a patient with a drain transferred from a hospital outside Mexico City. Ninety-eight additional cases had the same MultiLocus Sequence Typing (MLST) 758, of which 94 also had the same plasmid profile, two had an extra plasmid, and two had a different plasmid. The remaining seven isolates belonged to different MLSTs. Fifty-three patients (50%) died within 30 days of A. baumanniii isolation: 28 (20%) in colonized and 45 (68.2%) in those classified as infection (p<0.001). In multivariate regression analysis, clinical infection and patients with hematologic neoplasm, predicted 30-day mortality. The molecular epidemiology of this outbreak showed the threat posed by the introduction of MDR strains from other institutions in a hospital of immunosuppressed patients and highlights the importance of adhering to preventive measures, including contact isolation, when admitting patients with draining wounds who have been hospitalized in other institutions.

A fluorometric assay for rapid enrichment and determination of bacteria by using zirconium-metal organic frameworks as both capture surface and signal amplification tag

A fluorometric assay was introduced to determine Acinetobacter baumannii (A. baumannii) in blood samples by utilizing Zr-MOFs both as functional coating for magnetic Fe₃O₄ nanoparticles to provide modification surface (Zr-mMOF) and as fluorescein carrier to produce fluorescence signals (F@UIO-66-NH₂). Through strong Zr-O-P bonding, two distinct terminal phosphate-labeled A. baumannii and lipopolysaccharide (LPS) specific aptamers were attached onto Zr-MOFs to fabricate the magnetic core-shell capture probe (denoted as Zr-mMOF-p-Ab-Apt) and signal probe (denoted as F@UIO-66-NH₂-p-LPS-Apt), respectively. After successive incubation with A. baumannii in blood samples and magnetic separation, the sandwich-type composite of capture probe/A. baumannii cells/signal probe was treated with high concentration of anionic phosphate ions to destroy the nano-structure of UIO-66-NH₂ in the signal probe and fast release of fluorescein to produce amplified fluorescence signals. Due to the high aptamer modification efficiency of Zr-mMOF-p-Ab-Apt (up to 93%) and its strong affinity to A. baumannii, the enrichment efficiency of this capture probe has reached to 96.7%. Further, due to the high fluorescein loading efficiency of UIO-66-NH₂ and our novel amplification strategy to destroy F@UIO-66-NH₂-p-LPS-Apt to release and amplify fluorescein signals at 512 nm in the presence of high concentration of anionic phosphate ions, the sensitivity of this method has reached 10 cfu mL^-1. This method allows enrichment and determination of A. baumannii within ~2.5 h. The limit of detection of A. baumannii in blood samples is 10 cfu mL^-1 with a linear range of 10¹-10⁵ cfu mL^-1. This indicates the potential of this assay for diagnosis of bloodstream infection in early stage. Graphical abstractSchematic representation of sandwich-type fluorometric assay for Acinetobacter baumannii in blood samples with the capture probe (Zr-mMOF-p-Ab-Apt) and signal probe (F@UIO-66-NH2-p-LPS-Apt). The limit of detection is down to 10 cfu mL^-1 with a linear range of 10¹-10⁵ cfu mL^-1.

Designing A Pathogen-Focused Study To Address The High Unmet Medical Need Represented By Carbapenem-Resistant Gram-Negative Pathogens - The International, Multicenter, Randomized, Open-Label, Phase 3 CREDIBLE-CR Study

Carbapenem-resistant (CR) Gram-negative infections, including those caused by Enterobacteriaceae and the non-fermenters, represent the greatest unmet need for new effective treatments. The clinical development of new antibiotics for the treatment of CR infections is challenging and should focus on the individual pathogens irrespective of the infection site. However, the drug approval pathway is generally infection-site specific and rarely includes such drug-resistant pathogens. To overcome this limitation, a streamlined clinical development program may include a pathogen-focused clinical study, such as the CREDIBLE-CR study, to meet the expectations of some health authorities (ie, the European Medicines Agency [EMA]) and the medical community. Cefiderocol is a novel siderophore cephalosporin designed to target CR pathogens, including CR strains of Enterobacteriaceae (CRE), Pseudomonas aeruginosa, Acinetobacter baumannii, and also Stenotrophomonas maltophilia, which is intrinsically CR. The CREDIBLE-CR study was planned to evaluate cefiderocol in patients with CR Gram-negative infections regardless of species or infection-site source. Rapid diagnostic testing and/or selective media were provided to facilitate detection of CR pathogens to rapidly enroll patients with nosocomial pneumonia, bloodstream infection/sepsis, or complicated urinary tract infection. Patients were randomized 2:1 to receive cefiderocol or best available therapy. There were no pre-specified statistical hypotheses for this study, as the sample size was driven by enrollment feasibility and not based on statistical power calculations. The objective of the CREDIBLE-CR study was to provide descriptive evidence of the efficacy and safety of cefiderocol for the target population of patients with CR infections, including the non-fermenters. The CREDIBLE-CR study is currently the largest pathogen-focused, randomized, open-label, prospective, Phase 3 clinical study to investigate a new antibiotic in patients with CR Gram-negative infections. Here we describe the design of this pathogen-focused study and steps taken to aid patient enrollment into the study within an evolving regulatory environment.

Carbapenemase Genes and Multidrug Resistance of Acinetobacter Baumannii: A Cross Sectional Study of Patients with Pneumonia in Southern Vietnam

Background: Acinetobacter baumannii (Ab) is an opportunistic bacterial pathogen found in hospital-acquired infections including nosocomial pneumonia, especially multidrug-resistant Ab. This study aims to survey the drug resistance profiles of Ab isolated from patients in Thong Nhat Dong Nai General Hospital and assess the relationship between genotypes and antibiotic resistance; Methods: Ninety-seven Ab strains isolated from 340 lower respiratory tract specimens among pneumonia patients were used to screen the most common local carbapenemase genes. Antimicrobial susceptibility testing results and demographic data were collected and minimum inhibitory concentrations (MIC) of colistin were also determined; Results: Over 80% and 90% of Ab strains were determined as carbapenem-resistant and multidrug-resistant (MDR), respectively. Most of the strains carried carbapenemase genes, including blaOXA-51, blaOXA-23-like, blaOXA-58-like, and blaNDM-1, with proportions of 97 (100%), 76 (78.4%), 10 (10.3%), 6 (6.2%), respectively. Amongst these genes, blaOXA-23-like was the only gene which significantly influenced the resistance (p < 0.0001); and Conclusions: The severity of Ab antibiotic resistance is urgent and specifically related to carbapenemase encoding genes. Therefore, screening of MDR Ab and carbapenemase for better treatment options is necessary.

The Clinical and Economic Impact of Antibiotic Resistance in China: A Systematic Review and Meta-Analysis

Antibiotic resistance (ABR) is one of the biggest threats to global health, especially in China. This study aims to analyze the published literature on the clinical and economic impact of ABR or multi-drug resistant (MDR) bacteria compared to susceptible bacteria or non-infection, in mainland China. English and Chinese databases were searched to identify relevant studies evaluating mortality, hospital stay, and hospital costs of ABR. A meta-analysis of mortality was performed using a random effects model. The costs were converted into 2015 United States (US) dollars. Of 13,693 studies identified, 44 eligible studies were included. Twenty-nine investigated the impact of ABR on hospital mortality, 37 were focused on hospital stay, and 21 on hospital costs. Patients with ABR were associated with a greater risk of overall mortality compared to those with susceptibility or those without infection (odds ratio: 2.67 and 3.29, 95% confidence interval: 2.18–3.26 and 1.71–6.33, p < 0.001 and p < 0.001, respectively). The extra mean total hospital stay and total hospital cost were reported, ranging from 3 to 46 days, and from US$238 to US$16,496, respectively. Our study indicates that ABR is associated with significantly higher mortality. Moreover, ABR is not always, but usually, associated with significantly longer hospital stay and higher hospital costs.

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.

Shifting trends and age distribution of ESKAPEEc resistance in bloodstream infection, Southwest China, 2012-2017

Background

ESKAPEEc contribute to a majority of bloodstream infections (BSIs) and their antibiogram have changed overtime, while data concerning about these alterations are lacking in China. Added that a paucity of studies referred to ESKAPEEc in pediatric BSIs, our study aimed to demonstrate the longitudinal alterations of ESKAPEEc distribution and antibiogram in adult and pediatric BSIs in Southwest China.

Methods

A multicenter retrospective surveillance study was launched from 2012 to 2017. Data of China Antimicrobial Resistance Surveillance System (CARSS) was analyzed by Whonet 5.6 and Graphpad Prism 6 Software. Chi-square test or Fisher’s exact test was used to examine and compare temporal changes.

Results

A total of 32,259 strains was isolated, with 17.4% from pediatric BSIs. ESKAPEEc contributed to 58.67% (18,924/32,259) of BSIs, with 65.3% of adult BSIs and 27.2% of pediatric BSIs. Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) were the two predominant species. Carbapenem resistance was prevalent in 0.76, 4.60, 9.47,13.66, 59.47% of E. coli, K. pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa (P. aeruginosa) and Acinetobacter baumannii (A. baumannii), respectively. The proportions of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecium (VREFM) were 28.91% and 2.20%, respectively. Between 2012-2014 and 2015–2017, E. coli and K. pneumonia showed significantly increased resistance rates to imipenem but decreased to ceftriaxone and ceftazidime, while A. baumannii exhibited reduced resistances to almost all the beta-lactams tested. The prevalence of antimicrobial resistance to most of agents against Gram-positive ESKAPEEc did not significantly varied during the same timeframe. In comparison with those from adult BSIs, K. pneumoniae from pediatric BSIs exhibited high resistance rates to all the beta-lactams tested, especially to carbapenems (12.79% vs 3.87%), while A. baumannii showed low resistance rates to all the agents.

Conclusions

Ongoing burden of ESKAPEEc in BSIs and increasing trend of imipenem resistance in E. coli and K. pneumoniae call for continued surveillance. Carbapenems are still active against Gram-negative ESKAPEEc, except for A. baumannii and vancomycin or linezolid is still effective against Gram-positive ESKAPEEc. Carbapenem-resistant K. pneumoniae in children and carbapenem-resistant A. baumannii in adults necessitate effective antimicrobial strategies in consideration of age stratification.