Secular trends in the appropriateness of empirical antibiotic treatment in patients with bacteremia: a comparison between three prospective cohorts

An eleven-year cohort of bloodstream infections in 552 febrile neutropenic patients: resistance profiles of Gram-negative bacteria as a predictor of mortality

Antimicrobial stewardship is of major importance in patients with febrile neutropenia (FN). In this study, we aimed to investigate the trends in resistance and the relationship with mortality rates in patients with FN. The single-center surveillance data of inpatients with FN and diagnosed as microbiologically confirmed bloodstream infections (BSIs) between 2006 and 2016 were reviewed retrospectively. A total of 950 episodes in 552 patients with BSIs were analyzed. Of whom, 55.9% were male, the median age was 43 years, and 35.6% had acute myeloid leukemia. In total, 1016 microorganisms were isolated from blood cultures. Gram-negatives accounted for 42.4% (n = 403) of the episodes. Among Gram-negatives, Enterobacteriaceae accounted for 346 (86%) (E. coli, n = 197; 34% extended-spectrum β-lactamases (ESBL) producers, and Klebsiella spp., n = 120; 48.3% ESBL producers). Also, 24 (20.0%) of Klebsiella spp. had carbapenemase activity. There were 6 (5.0%) colistin-resistant Klebsiella spp. Thirteen (26.5%) of Pseudomonas spp. and 17 (60.7%) of Acinetobacter spp. had carbapenemase activity. There were 2 (5.6%) colistin-resistant Acinetobacter spp. The 30-day mortality rates were 12.0%, 21.5%, 34.6%, and 29.0% in BSIs due to Gram-positive, Gram-negative bacterial, fungal, and polymicrobial etiology respectively (p = 0.001). BSIs with ESBL-producing (p = 0.001) isolates, carbapenem (p < 0.001), and colistin-resistant isolates (p < 0.001) were associated with increased mortality risk. The tremendous rise in resistance rates among Gram-negatives is dreadfully related to increasing mortality and leads to sharp shifts toward extreme restrictions of unnecessary antibiotic uses. Antimicrobial stewardship in patients with FN requires vigilance and tailoring of treatment upon local surveillance data.

Early Intravenous Colistin Therapy as a Favorable Prognostic Factor for 28-day Mortality in Patients with CRAB Bacteremia: a Multicenter Propensity Score-Matching Analysis

BACKGROUND

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is associated with high mortality. One of the strategies to reduce the mortality in patients with CRAB infections is to use intravenous colistin early but the effect of this strategy has not been proven. Therefore, we investigated the association of early colistin therapy with 28-day mortality in patients with CRAB bacteremia.

METHODS

This retrospective multicenter propensity score-matching analysis was conducted in the Korea by reviewing the medical records of adult patients with CRAB bacteremia between January 2012 and March 2015. Early colistin therapy was defined as intravenous colistin administration for > 48 hours within five days after the blood culture collection. To identify the risk factors associated with the 28-day mortality in CRAB bacteremia, the clinical variables of the surviving patients were compared to those of the deceased patients.

RESULTS

Of 303 enrolled patients, seventy-six (25.1%) patients received early colistin therapy. The 28-day mortality was 61.4% (186/303). Fatal or rapidly-fatal McCabe classifications, intensive care unit admission, Sequential Organ Failure Assessment scores ≥ 8, vasopressor use, and acute kidney injury were statistically independent poor prognostic factors. Catheter-related infection and early colistin therapy (adjusted odds ratio [aOR], 0.45; 95% confidence interval [CI], 0.21-0.94) were independent favorable prognostic factors associated with 28-day mortality in patients with CRAB bacteremia. Early colistin therapy was still significantly associated with lower 28-day mortality in the propensity score-matching analysis (aOR, 0.31; 95% CI, 0.11-0.88).

CONCLUSION

This study suggests that early colistin therapy might help reduce the mortality of patients with CRAB bacteremia.

Multidrug- and Extensively Drug-Resistant Acinetobacter baumannii in a Tertiary Hospital from Brazil: The Importance of Carbapenemase Encoding Genes and Epidemic Clonal Complexes in a 10-Year Study

This study aimed to characterize the main mechanisms of acquired antimicrobial resistance of 103 multidrug-resistant Acinetobacter baumannii isolated from bloodstream from 2006 to 2016 from a hospital in Londrina, Brazil. All 103 isolates were identified as A. baumannii by amplification of the bla_OXA-51-like and rpoB genes. Mortality was observed in the majority (81.6%) of the patients. High non-susceptibility rates (100.0-10.7%) were obtained for the evaluated antimicrobials, including colistin, polymyxin B, and tigecycline, and most isolates were classified as extensively drug-resistant (78.6%). Carbapenemase production was observed in 92.2% of the isolates. All carbapenem-resistant isolates showed a carbapenem-hydrolyzing class D β-lactamase being either bla_OXA-23-like (97.9%) or bla_OXA-143-like (2.1%). None of the isolates had the genes bla_OXA-24-like, bla_OXA-58-like, bla_OXA-48, bla_KPC, bla_NDM, bla_SPM-1, bla_SIM-1, bla_VIM, bla_IMP, bla_GIM, bla_GES, mcr-1, qnrA, qnrB, qnrC, qnrS, and qnrVc. As a genetic context of the bla_OXA-23-like gene, Tn2006 was predominated (86.0%), and Tn2008 was less frequent (12.9%). Isolates harboring the bla_OXA-143-like gene showed the bla_OXA-253-like variant. A polyclonal profile was observed among the A. baumannii isolates. The presence of the international clonal complexes CC113/79, CC109/1, CC110/25, and CC103/15 was detected, with prevalence of CC113/79 (38.8%). This study provides essential information to understand the antimicrobial resistance patterns of A. baumannii and can be used to strengthen infection control measures in our hospital. Also, the study reinforces the urgent need to develop stewardship programs to avoid the spread and potential outbreaks by this pathogen.

Influence of GeneXpert MRSA/SA test implementation on clinical outcomes of Staphylococcus aureus bacteremia - a before-after retrospective study

Use of GeneXpert MRSA/SA in diagnostic algorithms of Staphylococcus aureus bacteremia may influence both patients' clinical outcomes and antibiotic stewardship. We evaluated these outcomes in a retrospective cohort before (1/6/2015-31/5/2016) and after (1/6/2016-31/8/2017) the introduction of the test in adult patients with Gram-positive cocci in clusters in blood cultures. We included 254 patients (125 preintervention, 129 postintervention). No significant difference in 30-day mortality or clinical success was demonstrated between periods. Appropriate antibiotic therapy rates were significantly higher in the postintervention group, and vancomycin use was significantly reduced (80.6% vs 53.6%, P < 0.01; 2.3±0.38 vs 2.98±1.02 defined daily doses/100 patient days, P = 0.026, respectively). Appropriate beta-lactam use was also significantly higher (56.7% postintervention vs 23.1% preintervention, P < 0.01). Use of GeneXpert MRSA/SA test has a positive effect on antibiotic stewardship measures, though it has no significant effect on clinical outcomes including mortality in this fatal infection.

Chromosomally encoded and plasmid-mediated polymyxins resistance in Acinetobacter baumannii: a huge public health threat

Acinetobacter baumannii is an opportunistic pathogen associated with nosocomial and community infections of great clinical relevance. Its ability to rapidly develop resistance to antimicrobials, especially carbapenems, has re-boosted the prescription and use of polymyxins. However, the emergence of strains resistant to these antimicrobials is becoming a critical issue in several regions of the world because very few of currently available antibiotics are effective in these cases. This review summarizes the most up-to-date knowledge about chromosomally encoded and plasmid-mediated polymyxins resistance in A. baumannii. Different mechanisms are employed by A. baumannii to overcome the antibacterial effects of polymyxins. Modification of the outer membrane through phosphoethanolamine addition, loss of lipopolysaccharide, symmetric rupture, metabolic changes affecting osmoprotective amino acids, and overexpression of efflux pumps are involved in this process. Several genetic elements modulate these mechanisms, but only three of them have been described so far in A. baumannii clinical isolates such as mutations in pmrCAB, lpxACD, and lpsB. Elucidation of genotypic profiles and resistance mechanisms are necessary for control and fight against resistance to polymyxins in A. baumannii, thereby protecting this class for future treatment.