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

Limited Impact of Colistin Resistance on Mortality of Intensive Care Patients with Carbapenem-resistant Bacteraemia

BACKGROUND

Increasing incidence of carbapenem-resistant Gram-negative bacteraemia (CR-GNB) has triggered increased use of polymyxins, likely fuelling the emergence and spread of colistin resistance.

AIM

To estimate the excess clinical burden of colistin resistance in intensive care patients with CR-GNB.

METHODS

A cohort was constructed of patients with CR-GNB during their stay in the intensive care unit (ICU) of a university hospital in Greece, over a 4-year period (2020-2023). Competing risks survival analysis was performed to estimate the burden associated with colistin resistance.

FINDINGS

In 177 ICU patients with CR-GNB, 134 (76%) had colistin-resistant isolates, predominantly Acinetobacter baumannii (79%), identified by broth microdilution. Patients with colistin resistant infection were similar to those with colistin susceptible with respect to age, sex, APACHE II score, Charlson comorbidity index, Pitt bacteraemia score, prior surgery and the occurrence of polymicrobial cultures. However, patients in the colistin resistant group had lower mortality risk compared to the colistin susceptible (31% vs. 44%, P = 0.004 at 14 days; 46% vs. 56% at 28 days, P = 0.173; respectively). Multivariable regression analysis confirmed that colistin resistant CR-GNB was associated with significantly lower hazard of inpatient death compared to colistin susceptible infection at 14 days (cause-specific hazard ratio [csHR], 0.53; 95% CI 0.28 - 1.01) and 28 days (csHR, 0.55; 95% CI 0.31 - 0.95) of infection onset.

CONCLUSION

Limited impact of colistin resistance on mortality was demonstrated in a large contemporary cohort of ICU patients with CR-GNB, possibly reflecting the recent shift away from colistin-based treatment regimens.

Clinical and molecular predictors of mortality in patients with carbapenem-resistant Acinetobacter baumannii bacteremia: A retrospective cohort study

BACKGROUND/PURPOSE

To investigate the virulence profiles and identify clinical and microbiological predictors of mortality in patients with carbapenem-resistant Acinetobacter baumannii (A. baumannii) bacteremia.

METHODS

This retrospective cohort study enrolled adult patients with carbapenem-resistant A. baumannii (CRAB). Multivariate logistic regression was used to identify the predictors of 30-day mortality. All isolates were subjected to real-time polymerase chain reaction for virulence factors and genotyped using multilocus sequence typing.

RESULTS

Among the 153 patients with CRAB bacteremia, 66 % received appropriate definitive antibiotic therapy. The in-hospital and 30-day mortality rates were 58.3 and 23.5 %, respectively. Ultimately, we enrolled 125 patients with CRAB bacteremia in the analysis, excluding early mortality cases. All CRAB isolates carried blaOXA-23 and blaOXA-51. The clinical strains belonged to 10 sequence types (STs), and the major genotypes were ST191, ST195, ST451, and ST784. The distribution of virulence factors included surface adhesion (Ata, 84.8 %; ChoP, 7.2 %), biofilm formation (OmpA, 76.8 %), killing of host cells (AbeD, 99.2 %), toxins (LipA, 99.2 %), and conjugation (BfmR, 90.4 %). In multivariate logistic regression analysis, hemodialysis due to acute kidney injury and moderate to severe thrombocytopenia were significant risk factors associated with 30-day mortality. However, microbiological factors were not significant predictors.

CONCLUSIONS

Clinical factors such as hemodialysis due to acute renal injury and moderate to severe thrombocytopenia have a greater influence on mortality in CRAB bacteremia compared with microbiological factors.

Exploration of sepsis assisting parameters in hospital autopsied-patients: a prospective study

Although Sepsis-3 doesn't require evidence of bacteremia to diagnose sepsis, clinicians often want to identify the causative pathogen at autopsy. In principle, if the blood cultures are the same at ante- and postmortem, the cause of death is obvious. However, interpretations of postmortem blood cultures are often difficult due to discordance, negativity, mixed infection, and contamination, of pathogens occupying ≥ 50% of the tests. To increase specificity identifying agonal phase sepsis in the situations where blood cultures are discordant, multiple or negative at postmortem, we established a scoring system using blood cultures, procalcitonin (PCN) showing highest sensitivity and specificity for postmortem serum, and bone marrow polyhemophagocytosis (PHP). Histological sepsis showed significantly higher levels of culture score (2.3 ± 1.5 vs. 0.4 ± 0.5, p < 0.001), PHP score (2.5 ± 0.8 vs. 1.0 ± 1.1, p < 0.001), and PCN score (1.8 ± 0.8 vs. 0.8 ± 0.6, p < 0.01) than non-septic patients. Receiver operating characteristic curve analysis indicated that estimation of three scores was the most reliable indicator for recognizing agonal phase sepsis. These findings suggest that the combination of these three inspections enables to determine the pathological diagnoses of sepsis even it is not obvious by discordant, mixed or negative blood cultures.

Co-isolates of Acinetobacter baumannii complex in polymicrobial infections: a meta-analysis

Background.Acinetobacter baumannii complex (ABC) infections are commonly polymicrobial. Examining which pathogens are most commonly co-isolated with ABC is an important first step for assessing disease potential due to pathogen-pathogen interactions.

Methods. Based on a systematic search of PubMed, Scopus and CENTRAL, we estimated percent proportions of co-isolates in polymicrobial pulmonary and bloodstream ABC infections using random-effects meta-analysis.

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.