Comparative efficacy and safety of treatment options for MDR and XDR Acinetobacter baumannii infections: a systematic review and network meta-analysis

Sulbactam for carbapenem-resistant Acinetobacter baumannii infections: a literature review

Carbapenem-resistant Acinetobacter baumannii (CRAB) is characterized as a critical priority pathogen with restricted therapeutic options. To date, the most effective antimicrobial treatment against this difficult-to-treat bacterial strain has not been established. Sulbactam is a β-lactamase inhibitor with intrinsic activity against this pathogen, however, as a β-lactam, it can be hydrolysed by β-lactamases produced by A. baumannii. High-dose, extended-infusion treatment with sulbactam can overcome this hydrolysis by β-lactamases and is considered an effective therapeutic strategy against CRAB. The aim of this review is to analyse primary and secondary research studies that compare sulbactam-based with other regimens, such as polymyxin-containing regimens, tigecycline-containing regimens and other antimicrobial combinations against CRAB infections, especially ventilator-associated pneumonia (VAP), hospital-acquired pneumonia (HAP) and bacteraemia. Our findings suggest that results are conflicting, mostly because of high heterogeneity among studies. However, in most studies, sulbactam-based regimens have demonstrated comparable, and in several studies more favourable results in contrast to other antimicrobial treatments with respect to clinical cure and mortality in CRAB-associated pneumonia, yet without reaching statistical significance in most cases. The auspicious novel β-lactam/β-lactamase inhibitor combination sulbactam/durlobactam is also discussed, although real-world clinical data regarding its efficacy in CRAB infections are still scarce. More randomized controlled trials comparing sulbactam-based with other regimens are warranted to determine the most effective antimicrobial combination against CRAB infections. Nevertheless, current data suggest that sulbactam could play a major role in this combination treatment.

Mortality and clinical outcomes of colistin versus colistin-based combination therapy for infections caused by Multidrug-resistant Acinetobacter baumannii in critically ill patients

BACKGROUND

Multidrug-resistant Acinetobacter baumannii emerged as a threatening "superbug" with significant morbidity and mortality and limited antimicrobial therapy options. The results of different antibiotic combination studies are heterogeneous and controversial. Further comparative studies are crucial to overcome such difficult-to-treat infections and to improve patient outcomes. This study investigates the mortality and outcomes of colistin versus colistin-based combination therapy for infections caused by Multidrug-resistant Acinetobacter baumannii in critically ill patients.

METHODS

A retrospective observational study was conducted at an academic tertiary hospital in Khobar City, Eastern Province, Saudi Arabia. Patients who fulfilled the inclusion criteria and were admitted from January 1, 2017, to December 31, 2022, were included. The investigated primary outcome was 30-day mortality, while secondary outcomes were one-year all-cause mortality, clinical cure, microbiologic eradication, and recurrence of Acinetobacter infections. Statistical comparisons were employed, and a P-value of ≤ .05 was considered significant.

RESULTS

Of the 178 patients who fulfilled the inclusion criteria, 47 received colistin only, and 131 received colistin in combinations (55 with carbapenems, 53 with tigecycline, and 23 with both). The estimated 30-day mortality rate of the study population was 22.5%, with statistically insignificant differences in 30-day mortality rates when the colistin group compared to cumulative colistin-based combination (23.4% vs. 22.1%; difference, 1.3 percentage points; 95% confidence interval [CI], 0.487-2.371; P = 0.858) or subgroups. However, colistin-based combination groups showed better secondary outcomes, with significantly less all-cause mortality and better clinical cure in colistin combination with carbapenems or tigecycline and less Acinetobacter infection recurrence in combination with carbapenems.

CONCLUSIONS

The study findings demonstrate the benefits of investigated colistin combination options that result in less one-year all-cause mortality, better clinical cure, higher microbiologic response, and less infection recurrence. However, no significant differences were observed regarding 30-day mortality. In addition, the study highlights the limitations of the available antimicrobial options and the crucial need for new effective antimicrobials and more successful combinations.

Natural peptides and their synthetic congeners acting against Acinetobacter baumannii through the membrane and cell wall: latest progress

Acinetobacter baumannii is one of the deadliest Gram-negative bacteria (GNB), responsible for 2-10% of hospital-acquired infections. Several antibiotics are used to control the growth of A. baumannii. However, in recent decades, the abuse and misuse of antibiotics to treat non-microbial diseases have led to the emergence of multidrug-resistant A. baumannii strains. A. baumannii possesses a complex cell wall structure. Cell wall-targeting agents remain the center of antibiotic drug discovery. Notably, the antibacterial drug discovery intends to target the membrane of the bacteria, offering several advantages over antibiotics targeting intracellular systems, as membrane-targeting agents do not have to travel through the plasma membrane to reach the cytoplasmic targets. Microorganisms, insects, and mammals produce antimicrobial peptides as their first line of defense to protect themselves from pathogens and predators. Importantly, antimicrobial peptides are considered potential alternatives to antibiotics. This communication summarises the recently identified peptides of natural origin and their synthetic congeners acting against the A. baumannii membrane by cell wall disruption.

Efficiency of combination therapy versus monotherapy for the treatment of infections due to carbapenem-resistant Gram-negative bacteria: a systematic review and meta-analysis

BACKGROUND

For resistant Gram-positive bacteria, evidence suggests that combination therapy is more effective. However, for resistant Gram-negative bacteria, no consensus has been reached. This study aims to comprehensively summarize the evidence and evaluate the impact of combination versus monotherapy on infections caused by carbapenem-resistant Gram-negative bacteria (CRGNB).

METHODS

A systematic search was conducted in PubMed, Cochrane library, Web of Science, and Embase up to June 15, 2024, to identify relevant studies. This study included comparisons of monotherapy and combination therapy for treating infections caused by CRGNB. Topical antibiotics (i.e., inhalational or intratracheal administration) and monotherapy with sulbactam/relebactam was excluded. The primary outcome was mortality, and the secondary outcomes were clinical success and microbiological eradication. Pooled odds ratios (OR) and 95% confidence intervals (CI) were calculated in order to systematically assess effect of treatment on mortality, clinical success and microbiological eradication. Subgroup analyses, publication bias tests, and sensitivity analyses were also performed.

RESULTS

A total of 62 studies, including 8342 participants, were analyzed, comprising 7 randomized controlled trials and 55 non-randomized studies. Monotherapy was associated with higher mortality (OR = 1.29, 95%CI: 1.11-1.51), lower clinical success (OR = 0.74, 95%CI: 0.56-0.98), and lower microbiological eradication (OR = 0.71, 95%CI: 0.55-0.91) compared to combination therapy for CRGNB infections. Specifically, patients with carbapenem-resistant Enterobacteriaceae (CRE) infections receiving monotherapy had higher mortality (OR = 1.50, 95%CI: 1.15-1.95), comparable clinical success (OR = 0.57,95%CI: 0.28-1.16), and lower microbiological eradication (OR = 0.48,95%CI:0.25-0.91) than those receiving combination therapy. For carbapenem-resistant Acinetobacter baumannii (CRAB) infections, no significant differences were observed in mortality (OR = 1.15.95%CI: 0.90-1.47), clinical success (OR = 0.95,95%CI: 0.74-1.24) and microbiological eradication (OR = 0.78,95%CI: 0.54-1.12).

CONCLUSIONS

Monotherapy or combination therapy is controversial. The systematic review and meta-analysis suggested that monotherapy is associated with higher mortality, lower clinical success, and lower microbiological eradication for treating infection caused by CRGNB. The available evidence suggests that treatment should be selected based on the specific bacteria and antibiotic used. Monotherapy for CRE infections may lead to adverse outcomes. For CRAB infections, no significant differences were found between combination therapy and monotherapy.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022331861.

Effect of colistin combined with sulbactam: 9 g versus 12 g per day on mortality in the treatment of carbapenems resistant Acinetobacter baumannii pneumonia: A randomized controlled trial

BACKGROUND

The current treatment recommendation involves administering a high dose of sulbactam alongside at least one additional agent. However, there remains a lack of data regarding the optimal dosage of sulbactam. We investigated whether administering sulbactam at a dosage of 12 g/day decreases the mortality rate among patients with CRAB pneumonia compared to 9 g/day.

METHODS

The study was an open-label, superiority, randomized controlled trial conducted at Phramongkutklao Hospital between September 2019 and September 2023 in patients diagnosed with CRAB. Participants were randomly assigned to receive a combination of colistin with either 9 or 12 g/day of sulbactam. The primary endpoint was the all-cause mortality rate at 28 days postrandomization.

RESULTS

Among the 138 participants, there was a trend towards a lower mortality rate in the 12 g/day group (59.4% vs. 47.8%; P = 0.158). After adjusting for factors associated with mortality, a lower mortality was observed in the 12 g/day group (adjusted HR 0.54 [95% CI 0.33-0.87]; P = 0.0110). The microbiological cure rate at day 7 was higher in the 12 g/day group (73.2% vs. 89.4%; P = 0.02).

CONCLUSIONS

Colistin in combination with sulbactam at a dosage of 12 g/day may improve mortality compared to 9 g/day.

Isolation, characterization, and potential application of Acinetobacter baumannii phages against extensively drug-resistant strains

One of the significant issues in treating bacterial infections is the increasing prevalence of extensively drug-resistant (XDR) strains of Acinetobacter baumannii. In the face of limited or no viable treatment options for extensively drug-resistant (XDR) bacteria, there is a renewed interest in utilizing bacteriophages as a treatment option. Three Acinetobacter phages (vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln) were identified from hospital sewage and analyzed for their morphology, host ranges, and their genome sequences were determined and annotated. These phages and vB_AbaS_SA1 were combined to form a phage cocktail. The antibacterial effects of this cocktail and its combinations with selected antimicrobial agents were evaluated against the XDR A. baumannii strains. The phages exhibited siphovirus morphology. Out of a total of 30 XDR A. baumannii isolates, 33% were sensitive to vB_AbaS_Ftm, 30% to vB_AbaS_Gln, and 16.66% to vB_AbaS_Eva. When these phages were combined with antibiotics, they demonstrated a synergistic effect. The genome sizes of vB_AbaS_Ftm, vB_AbaS_Eva, and vB_AbaS_Gln were 48487, 50174, and 50043 base pairs (bp), respectively, and showed high similarity. Phage cocktail, when combined with antibiotics, showed synergistic effects on extensively drug-resistant (XDR) strains of A. baumannii. However, the need for further study to fully understand the mechanisms of action and potential limitations of using these phages is highlighted.

Transcriptomic investigations of polymyxins and colistin/sulbactam combination against carbapenem-resistant Acinetobacter baumannii

Carbapenem-resistant Acinetobacter baumannii (CRAB) is a Priority 1 (Critical) pathogen urgently requiring new antibiotics. Polymyxins are a last-line option against CRAB-associated infections. This transcriptomic study utilized a CRAB strain to investigate mechanisms of bacterial killing with polymyxin B, colistin, colistin B, and colistin/sulbactam combination therapy. After 4 h of 2 mg/L polymyxin monotherapy, all polymyxins exhibited common transcriptomic responses which primarily involved disruption to amino acid and fatty acid metabolism. Of the three monotherapies, polymyxin B induced the greatest number of differentially expressed genes (DEGs), including for genes involved with fatty acid metabolism. Gene disturbances with colistin and colistin B were highly similar (89 % common genes for colistin B), though effects on gene expression were generally lower (0-1.5-fold in most cases) with colistin B. Colistin alone (2 mg/L) or combined with sulbactam (64 mg/L) resulted in rapid membrane disruption as early as 1 h. Transcriptomic analysis of this combination revealed that the effects were driven by colistin, which included disturbances in fatty acid synthesis and catabolism, and inhibition of nutrient uptake. Combination therapy produced substantially higher fold changes in 72 % of DEGs shared with monotherapy, leading to substantially greater reductions in fatty acid biosynthesis and increases in biofilm, cell wall, and phospholipid synthesis. This indicates synergistic bacterial killing with the colistin/sulbactam combination results from a systematic increase in perturbation of many genes associated with bacterial metabolism. These mechanistic insights enhance our understanding of bacterial responses to polymyxin mono- and combination therapy and will assist to optimize polymyxin use in patients.

Antibacterial Therapy Options for Infections Caused by Carbapenem-Resistant Acinetobacter baumannii

The review presents current treatment regimens for infections associated with carbapenem-resistant Acinetobacter baumannii, which are leading nosocomial pathogens exhibiting multidrug resistance to available antibacterial drugs. To date, widely used beta-lactam antibiotics, including carbapenems, have lost their effectiveness in combating acinetobacter infections, while new antibiotics remain poorly available to patients. Therefore, the only measure to combat the antibiotic resistance of carbapenem-resistant A. baumannii is to evaluate the efficiency of combination therapy in vitro and in vivo, which is of particular interest to Russian and foreign researchers.

Combination Versus Monotherapy for Carbapenem-Resistant Acinetobacter Species Serious Infections: A Prospective IPTW Adjusted Cohort Study

INTRODUCTION

International guidelines recommend definitive combination antibiotic therapy for the management of serious infections involving carbapenem-resistant Acinetobacter (CRAB) species. The commonly available combination options include high-dose sulbactam, polymyxins, tetracyclines, and cefiderocol. Scanty prospective data exist to support this approach.

METHODS

Patients with CRAB bacteraemia, ventilator-associated pneumonia (VAP), or both were categorized based on whether they received combination therapy or monotherapy. The 30-day mortality was compared between the two groups. Inverse probability treatment weighting (IPTW) was done using propensity score (PS) for a balanced comparison between groups.

RESULTS

Between January 2021 and May 2023, of the 161 patients with CRAB bacteraemia (n = 55, 34.2%), VAP (n = 46, 28.6%), or both (n = 60, 37.3%) who received appropriate intravenous antibiotic therapy, 70% (112/161) received monotherapy, and the rest received combination therapy. The overall 30-day mortality was 62% (99/161) and not different (p = 0.76) between the combination therapy (31/49, 63.3%) and monotherapy (68/112, 60.7%) groups. The propensity score matching using IPTW did not show a statistical difference (p = 0.47) in 30-day mortality for receiving combination therapy with an adjusted odds ratio (OR) P of 1.29 (0.64, 2.58).

CONCLUSION

Combination therapy for CRAB infections needs further study in a randomised controlled trial, as this observational study showed no difference in 30-day mortality between monotherapy and combination therapy.

Acinetobacter calcoaceticus-baumannii complex prevalence, spatial-temporal distribution, and contamination sources in Canadian aquatic environments

Acinetobacter calcoaceticus-baumannii (ACB) complex has been identified as a group of emerging opportunistic pathogens that cause nosocomial infections. The current study investigates the prevalence, distribution, and diversity of pathogenic ACB complex in various aquatic systems with different uses. Of the total 157 agricultural, raw drinking water intake, recreational beach, and wastewater treatment plant (WWTP) effluent samples, acinetobacters were isolated, quantified, and confirmed by genus- and ACB complex-specific PCR assays. Of all agricultural surface water samples, A. calcoaceticus (65%) was more frequently detected than A. pittii (14%), A. nosocomialis (9%), and A. baumannii (3%). In WWTP effluent samples, A. baumannii was more prevalent in de-chlorinated (60%) samples compared to both A. pittii and A. nosocomialis (40%). Interestingly, A. nosocomialis (43%), A. calcoaceticus (29%), and A. baumannii (14%) were detected in raw drinking water intake samples, whereas A. pittii (50%) and A. nosocomialis (25%) were detected in beach samples. Although no sampling location-specific differences were recorded, significant (P < 0.05) seasonal differences were observed when agricultural surface water samples collected in spring were compared with the summer and fall. Whereas effluent chlorination significantly impacted the degree of prevalence of Acinetobacter in WWTP effluent samples, overall, the prevalence of ACB complex in all sampling locations and seasons indicates that these water sources, containing human-associated ACB complex, may pose potential health risks as community-acquired opportunistic infections.IMPORTANCEAcinetobacter calcoaceticus-baumannii (ACB) complex is a group of organisms known to cause problematic nosocomial opportunistic infections. A member of the species complex, A. baumannii, is becoming a global threat to infection treatment as strains are increasingly develop resistance to antibiotics. The prevalence and distribution of potentially pathogenic Acinetobacter calcoaceticus-baumannii complex species remain poorly understood, and there is a need to better understand the occurrence of A. baumannii in non-nosocomial environments. Our research details the spatial-temporal distribution of ACB complex species in a regional watershed and highlights the presence of ACB complex in wastewater effluent that is discharged into a river. These findings deepen our understanding of this group of species in non-nosocomial environments and encourage the development of monitoring programs for these species in regional waters.

Prevalence, Risk Factors, and Outcome of Carbapenem-resistant Acinetobacter Infections in a Community Hospital in Madinah, Saudi Arabia

Background

Acinetobacter is a Gram-negative bacterium that causes nosocomial infections, increasing healthcare costs, patient morbidity, and mortality. The rate of carbapenem resistance among Acinetobacter species is rising in several countries, including Saudi Arabia.

Objective

To determine the risk factors and compare the predictors of mortality in patients infected with carbapenem-susceptible and carbapenem-resistant Acinetobacter strains.

Materials and Methods

This retrospective study included patients with Acinetobacter infection who were admitted to a community hospital in Madinah, Saudi Arabia, between January 2017 and June 2021. A logistic regression analysis was conducted to assess the risks of acquiring carbapenem-resistant Acinetobacter infections and the mortality risk associated with these infections.

Results

This study included 138 Acinetobacter-infected cases, of which 114 (82%) were carbapenem-resistant infections. Between 2017 and 2020, resistance rates increased from 75% to 87%. Patients with carbapenem-resistant Acinetobacter infections had higher 90-day mortality than those with carbapenem-susceptible infection (62% vs. 29%, P = 0.006). The risk factors for carbapenem-resistant Acinetobacter infections were prior antimicrobial therapy (aOR: 8.36 [1.69-41.29]; P = 0.009) and mechanical ventilation (aOR: 6.07 [1.82-20.20]; P = 0.003). Among all patients with Acinetobacter infections, significant predictors of 90-day mortality were carbapenem resistance (aOR: 3.26 [1.19-8.90]; P = 0.021) and Charlson comorbidity score (aOR: 1.19 [1.06-1.34]; P = 0.004).

Conclusion

The increase in carbapenem-resistant Acinetobacter cases in this study was consistent with the findings of other studies from Saudi Arabia. This, together with the high associated mortality rates, indicates the urgent need for effective antimicrobials and infection prevention strategies to combat carbapenem-resistant Acinetobacter infections in hospitals.

Comparison of cefiderocol and colistin-based regimens for the treatment of severe infections caused by carbapenem-resistant Acinetobacter baumannii: a systematic review with meta-analysis and trial sequential analysis

BACKGROUND

There are multiple antibiotic regimens for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) in clinical practice. We conducted this meta-analysis to compare the efficacy and safety of cefiderocol-based regimens and colistin-based regimens in the treatment of CRAB infections.

METHODS

Two authors independently searched the PubMed, Web of Science, Embase, and Cochrane databases from their establishment to April 15, 2024, to search for randomized controlled trials (RCTs) or cohort studies, and compared the clinical efficacy and safety of cefiderocol-based regimens and colistin-based regimens in the treatment of CRAB infections. The Newcastle Ottawa Scale (NOS) checklist was used to evaluate the quality of the included studies. The primary outcome was all-cause mortality, and subgroup analysis was conducted on the basis of the site of infection and the risk of bias in the studies. Trial sequential analysis (TSA) was then conducted.

RESULTS

Six observational studies were included, with 251 cases in the cefiderocol-based group and 372 cases in the colistin-based group. Compared to the colistin-based group, the cefiderocol-based group had lower all-cause mortality (RR = 0.71, 95% CI: 0.54-0.92, P = 0.01) and 30-day mortality (RR = 0.64, 95% CI: 0.43-0.95, P = 0.03). However, for the 14-day and 28-day mortality rates, there was no statistically significant difference between two groups. According to the subgroup analysis, among patients with bloodstream infection (BSI), the cefiderocol-based group had lower all-cause mortality, but it did not reduce the mortality of ventilator-associated pneumonia (VAP) patients. The result of TSA showed that our conclusions are reliable. There was no significant statistical difference in the microbiological cure rate, clinical cure rate, or duration of hospitalization. In addition, the cefiderocol-based group did not have an increased incidence of acute kidney injury (AKI).

CONCLUSIONS

Compared with the colistin-based regimens, the cefiderocol-based regimens were significantly associated with a lower risk of mortality in CRAB-infected patients, especially for patients with BSI. However, they did not show any advantages in terms of the clinical cure rate or microbiological cure rate, nor did they reduce the incidence of AKI.

PROSPERO REGISTRATION NUMBER

CRD42023487213.

Prognostic Factors That Affect Mortality Patients with Acinetobacter baumannii Bloodstream Infection

Background

To evaluate the clinical features of patients with Acinetobacter baumannii bloodstream infection (BSI).

Methods

Totally 200 inpatients with Acinetobacter baumannii BSI were included, clinical features of Acinetobacter baumannii BSI inpatients between 90-day survival and 90-day mortality groups, between 30-day survival and 30-day mortality groups, between patients infected with multidrug-resistant (MDR group) and sensitive Acinetobacter baumannii (sensitive group) were analyzed. The prognostic factors of 90-day mortality were analyzed by univariate logistic regression and multivariate logistic regression. The survival curve in bloodstream infectious patients with multidrug-resistant (MDR group) and sensitive Acinetobacter baumannii (sensitive group) was analyzed by Kaplan-Meier analysis.

Results

The 90-day mortality patients had significantly higher carbapenem-resistant bacterial infection and critical care unit (ICU) admission. The 90-day and 30-day mortality groups showed higher C-reactive protein (CRP) and serum creatinine (Scr) levels and lower red blood cells (RBC) and albumin (ALB) levels than their survival counterparts, respectively. Critical surgery, ICU admission and delayed antibiotic treatment were independently prognostic risk predictors for 90-day mortality in Acinetobacter baumannii BSI patients, while critical surgery and diabetes were independently prognostic risk predictors for 90-day mortality in carbapenem-resistant Acinetobacter baumannii BSI patients. Compared with sensitive group, MDR group showed significantly longer ICU and whole hospital stay, lower levels of lymphocytes, RBC, hemoglobin, lactate dehydrogenase and ALB, higher frequency of infection originating from the skin and skin structure. Moreover, patients in the MDR group had a significantly worse overall survival than the sensitive group.

Conclusion

We identified the prognostic factors of Acinetobacter baumannii BSI and carbapenem-resistant Acinetobacter baumannii BSI patients. Critical surgery, ICU admission, delayed antibiotic treatment or diabetes were significantly associated with the mortality of those patients. Moreover, aggressive measures to control MDR Acinetobacter baumannii could lead to improved outcomes.

Deciphering the impact of Acinetobacter baumannii on human health, and exploration of natural compounds as efflux pump inhibitors to treat multidrug resistance

Acinetobacter baumannii is an ESKAPE pathogen and threatens human health by generating infections with high fatality rates. A. baumannii leads to a spectrum of infections such as skin and wound infections, endocarditis, meningitis pneumonia, septicaemia and urinary tract infections. Recently, strains of A. baumannii have emerged as multidrug-resistant (MDR), meaning they are resistant to at least three different classes of antibiotics. MDR development is primarily intensified by widespread antibiotic misuse and inadequate stewardship. The World Health Organization (WHO) declared A. baumannii a precarious MDR species. A. baumannii maintains the MDR phenotype via a diverse array of antimicrobial metabolite-hydrolysing enzymes, efflux of antibiotics, impermeability and antibiotic target modification, thereby complicating treatment. Hence, a deeper understanding of the resistance mechanisms employed by MDR A. baumannii can give possible approaches to treat antimicrobial resistance. Resistance-nodulation-cell division (RND) efflux pumps have been identified as the key contributors to MDR determinants, owing to their capacity to force a broad spectrum of chemical substances out of the bacterial cell. Though synthetic inhibitors have been reported previously, their efficacy and safety are of debate. As resistance-modifying agents, phytochemicals are ideal choices. These natural compounds could eliminate the bacteria or interact with pathogenicity events and reduce the bacteria's ability to evolve resistance. This review aims to highlight the mechanism behind the multidrug resistance in A. baumannii and elucidate the utility of natural compounds as efflux pump inhibitors to deal with the infections caused by A. baumannii.

Treatment of infections caused by carbapenem-resistant Acinetobacter baumannii

Patients with severe carbapenem-resistant Acinetobacter baumannii (CRAB) infections currently face significant treatment challenges. When patients display signs of infection and the clinical suspicion of CRAB infections is high, appropriate treatment should be immediately provided. However, current treatment plans and clinical data for CRAB are limited. Inherent and acquired resistance mechanisms, as well as host factors, significantly restrict options for empirical medication. Moreover, inappropriate drug coverage can have detrimental effects on patients. Most existing studies have limitations, such as a restricted sample size, and are predominantly observational or non-randomized, which report significant variability in patient infection severity and comorbidities. Therefore, a gold-standard therapy remains lacking. Current and future treatment options of infections due to CRAB were described in this review. The dose and considerable side effects restrict treatment options for polymyxins, and high doses of ampicillin-sulbactam or tigecycline appear to be the best option at the time of initial treatment. Moreover, new drugs such as durlobactam and cefiderocol have substantial therapeutic capabilities and may be effective salvage treatments. Bacteriophages and antimicrobial peptides may serve as alternative treatment options in the near future. The advantages of a combination antimicrobial regimen appear to predominate those of a single regimen. Despite its significant nephrotoxicity, colistin is considered a primary treatment and is often used in combination with antimicrobials, such as tigecycline, ampicillin-sulbactam, meropenem, or fosfomycin. The Infectious Diseases Society of America (IDSA) has deemed high-dose ampicillin-sulbactam, which is typically combined with high-dose tigecycline, polymyxin, and other antibacterial agents, the best option for treating serious CRAB infections. A rational combination of drug use and the exploration of new therapeutic drugs can alleviate or prevent the effects of CRAB infections, shorten hospital stays, and reduce patient mortality.

Clinical effectiveness of cefiderocol for the treatment of bloodstream infections due to carbapenem-resistant Acinetobacter baumannii during the COVID-19 era: a single center, observational study

BACKGROUND

We assessed the clinical effectiveness of cefiderocol (CFDC) in comparison with colistin (COL) for the treatment of carbapenem-resistant Acinetobacter baumannii (CRAB) bloodstream infections (BSI).

MATERIALS/METHODS

Retrospective cohort study including adults with CRAB-BSI. Outcomes were mortality, clinical cure and adverse events during therapy. The average treatment effect of CFDC compared to COL was weighted with the inverse-probability treatment weight (IPTW).

RESULTS

Overall, 104 patients were included (50 CFDC, 54 COL), median age 66.5 years, median Charlson Comorbidity Index 5, septic shock in 33.6% of patients. Primary BSI accounted for 43.3% of cases, followed by ventilator-associated pneumonia (VAP) (26%), catheter-related BSI (20.2%) and hospital-acquired pneumonia (HAP) (9.6%). Although not significantly, mortality at all time points was lower for CFDC than COL, while clinical cure was higher in CFDC than COL (66% vs. 44.4%, p = 0.027). Adverse events were more frequent in COL than CFDC-group (38.8% vs. 10%, p < 0.0001), primarily attributed to acute kidney injury (AKI) in the COL group. Patients with bacteremic HAP/VAP treated with CFDC had a significant lower 30-d mortality and higher clinical cure than COL (p = 0.008 and p = 0.0008, respectively). Increment of CCI (p = 0.005), ICU (p = 0.025), SARS-CoV2 (p = 0.006) and ECMO (p < 0.0001) were independently associated with 30-d mortality, while receiving CFDC was not associated with survival.

CONCLUSIONS

CFDC could represent an effective and safe treatment option for CRAB BSI, especially in patients with bacteremic HAP/VAP and frail patients where the risk of acute renal failure during therapy should be avoided.

Optimizing Treatment for Carbapenem-Resistant Acinetobacter baumannii Complex Infections: A Review of Current Evidence

Carbapenem-resistant Acinetobacter baumannii complex (CRAB) poses a significant global health challenge owing to its resistance to multiple antibiotics and limited treatment options. Polymyxin-based therapies have been widely used to treat CRAB infections; however, they are associated with high mortality rates and common adverse events such as nephrotoxicity. Recent developments include numerous observational studies and randomized clinical trials investigating antibiotic combinations, repurposing existing antibiotics, and the development of novel agents. Consequently, recommendations for treating CRAB are undergoing significant changes. The importance of colistin is decreasing, and the role of sulbactam, which exhibits direct antibacterial activity against A. baumannii complex, is being reassessed. High-dose ampicillin-sulbactam-based combination therapies, as well as combinations of sulbactam and durlobactam, which prevent the hydrolysis of sulbactam and binds to penicillin-binding protein 2, have shown promising results. This review introduces recent advancements in CRAB infection treatment based on clinical trial data, highlighting the need for optimized treatment protocols and comprehensive clinical trials to combat the evolving threat of CRAB effectively.

A novel multivariate logistic model for predicting risk factors of failed treatment with carbapenem-resistant Acinetobacter baumannii ventilator-associated pneumonia

Background

This study aimed to explore the risk factors for failed treatment of carbapenem-resistant Acinetobacter baumannii ventilator-associated pneumonia (CRAB-VAP) with tigecycline and to establish a predictive model to predict the incidence of failed treatment and the prognosis of CRAB-VAP.

Methods

A total of 189 CRAB-VAP patients were included in the safety analysis set from two Grade 3 A national-level hospitals between 1 January 2022 and 31 December 2022. The risk factors for failed treatment with CRAB-VAP were identified using univariate analysis, multivariate logistic analysis, and an independent nomogram to show the results.

Results

Of the 189 patients, 106 (56.1%) patients were in the successful treatment group, and 83 (43.9%) patients were in the failed treatment group. The multivariate logistic model analysis showed that age (OR = 1.04, 95% CI: 1.02, 1.07, p = 0.001), yes. of hypoproteinemia (OR = 2.43, 95% CI: 1.20, 4.90, p = 0.013), the daily dose of 200 mg (OR = 2.31, 95% CI: 1.07, 5.00, p = 0.034), yes. of medication within 14 days prior to surgical intervention (OR = 2.98, 95% CI: 1.19, 7.44, p = 0.019), and no. of microbial clearance (OR = 0.31, 95% CI: 0.14, 0.70, p = 0.005) were risk factors for the failure of tigecycline treatment. Receiver operating characteristic (ROC) analysis showed that the AUC area of the prediction model was 0.745 (0.675-0.815), and the decision curve analysis (DCA) showed that the model was effective in clinical practice.

Conclusion

Age, hypoproteinemia, daily dose, medication within 14 days prior to surgical intervention, and microbial clearance are all significant risk factors for failed treatment with CRAB-VAP, with the nomogram model indicating that high age was the most important factor. Because the failure rate of CRAB-VAP treatment with tigecycline was high, this prediction model can help doctors correct or avoid risk factors during clinical treatment.

Treatment Strategies of Colistin Resistance Acinetobacter baumannii Infections

Acinetobacter baumannii has emerged as a pressing challenge in clinical practice, mainly due to the development of resistance to multiple antibiotics, including colistin, one of the last-resort treatments. This review highlights all the possible mechanisms of colistin resistance and the genetic basis contributing to this resistance, such as modifications to lipopolysaccharide or lipid A structures, alterations in outer membrane permeability via porins and heteroresistance. In light of this escalating threat, the review also evaluates available treatment options. The development of new antibiotics (cefiderocol, sulbactam/durlobactam) although not available everywhere, and the use of various combinations and synergistic drug combinations (including two or more of the following: a polymyxin, ampicillin/sulbactam, carbapenems, fosfomycin, tigecycline/minocycline, a rifamycin, and aminoglycosides) are discussed in the context of overcoming colistin resistance of A. baumannii infections. Although most studied combinations are polymyxin-based combinations, non-polymyxin-based combinations have been emerging as promising options. However, clinical data remain limited and continued investigation is essential to determine optimal therapeutic strategies against colistin-resistant A. baumannii.

Carbapenem-resistant Acinetobacter baumannii and Ventilator-associated Pneumonia; Epidemiology, Risk Factors, and Current Therapeutic Approaches

Acinetobacter baumannii is one of the primary pathogens responsible for healthcare-associated infections. It is related to high rates of morbidity and mortality globally, mainly because of its high capacity to develop resistance to antimicrobials. Nowadays, carbapenem-resistant A. baumannii (CRAB) has increased and represents a significant concern among carbapenem-resistant organisms. It is also a key pathogen associated with ventilator-associated pneumonia. CRAB was placed on the critical group of the universal priority list of the World Health Organization for antibiotic-resistant bacteria, to mention the importance of research development and the urgency of new antibiotics. Patients with severe CRAB infections currently face significant treatment challenges. Some approaches have been taken to deal with CRAB, such as combination therapy and the synergistic effect of certain antibiotics, but the best antibiotic regimen is still unknown. In this narrative review, we attempt to clarify the issues, including epidemiology, risk factors, and current treatment options for CRAB.

Sulbactam-durlobactam: a β-lactam/β-lactamase inhibitor combination targeting Acinetobacter baumannii

Sulbactam-durlobactam is a pathogen-targeted β-lactam/β-lactamase inhibitor combination that has been approved by the US FDA for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia caused by susceptible isolates of Acinetobacter baumannii-calcoaceticus complex (ABC) in patients 18 years of age and older. Sulbactam is a penicillin derivative with antibacterial activity against Acinetobacter but is prone to hydrolysis by β-lactamases encoded by contemporary isolates. Durlobactam is a diazabicyclooctane β-lactamase inhibitor with activity against Ambler classes A, C and D serine β-lactamases that restores sulbactam activity both in vitro and in vivo against multidrug-resistant ABC. Sulbactam-durlobactam is a promising alternative therapy for the treatment of serious Acinetobacter infections, which can have high rates of mortality.

Characterization of bacteriophage vB_AbaS_SA1 and its synergistic effects with antibiotics against clinical multidrug-resistant Acinetobacter baumannii isolates

Acinetobacter baumannii is a major cause of nosocomial infections globally. The increasing prevalence of multidrug-resistant (MDR) A. baumannii has become an important public health concern. To combat drug resistance, alternative methods such as phage therapy have been suggested. In total, 30 MDR A. baumannii strains were isolated from clinical specimens, and their antibiotic susceptibilities were determined. The Acinetobacter phage vB_AbaS_SA1, isolated from hospital sewage, was characterized. In addition to its plaque size, particle morphology, and host range, its genome sequence was determined and annotated. Finally, the antibacterial effects of phage alone, antibiotics alone, and phage/antibiotic combinations were assessed against the A. baumannii strains. Phage vB_AbaS_SA1 had siphovirus morphology, showed a latent period of 20 min, and a 250 PFU/cell (plaque forming unit/cell) burst size. When combined with antibiotics, vB_AbaS_SA1 (SA1) showed a significant phage-antibiotic synergy effect and reduced the overall effective concentration of antibiotics in time-kill assessments. The genome of SA1 is a linear double-stranded DNA of 50 108 bp in size with a guanine-cytosine (GC) content of 39.15%. Despite the potent antibacterial effect of SA1, it is necessary to perform additional research to completely elucidate the mechanisms of action and potential constraints associated with utilizing this bacteriophage.

Epidemiology and antimicrobial resistance trends of Acinetobacter species in the United Arab Emirates: a retrospective analysis of 12 years of national AMR surveillance data

Introduction

Acinetobacter spp., in particular A. baumannii, are opportunistic pathogens linked to nosocomial pneumonia (particularly ventilator-associated pneumonia), central-line catheter-associated blood stream infections, meningitis, urinary tract infections, surgical-site infections, and other types of wound infections. A. baumannii is able to acquire or upregulate various resistance determinants, making it frequently multidrug-resistant, and contributing to increased mortality and morbidity. Data on the epidemiology, levels, and trends of antimicrobial resistance of Acinetobacter spp. in clinical settings is scarce in the Gulf Cooperation Council (GCC) and Middle East and North Africa (MENA) regions.

Methods

A retrospective 12-year analysis of 17,564 non-duplicate diagnostic Acinetobacter spp. isolates from the United Arab Emirates (UAE) was conducted. Data was generated at 317 surveillance sites by routine patient care during 2010-2021, collected by trained personnel and reported by participating surveillance sites to the UAE National AMR Surveillance program. Data analysis was conducted with WHONET.

Results

Species belonging to the A. calcoaceticus-baumannii complex were mostly reported (86.7%). They were most commonly isolated from urine (32.9%), sputum (29.0%), and soft tissue (25.1%). Resistance trends to antibiotics from different classes during the surveillance period showed a decreasing trend. Specifically, there was a significant decrease in resistance to imipenem, meropenem, and amikacin. Resistance was lowest among Acinetobacter species to both colistin and tigecycline. The percentages of multidrug-resistant (MDR) and possibly extensively drug-resistant (XDR) isolates was reduced by almost half between the beginning of the study in 2010 and its culmination in 2021. Carbapenem-resistant Acinetobacter spp. (CRAB) was associated with a higher mortality (RR: 5.7), a higher admission to ICU (RR 3.3), and an increased length of stay (LOS; 13 excess inpatient days per CRAB case), as compared to Carbapenem-susceptible Acinetobacter spp.

Conclusion

Carbapenem-resistant Acinetobacter spp. are associated with poorer clinical outcomes, and higher associated costs, as compared to carbapenem-susceptible Acinetobacter spp. A decreasing trend of MDR Acinetobacter spp., as well as resistance to all antibiotic classes under surveillance was observed during 2010 to 2021. Further studies are needed to explore the reasons and underlying factors leading to this remarkable decrease of resistance over time.

Investigation of EpsA, OmpA, and Bap Genes among MDR and XDR Acinetobacter baumannii Isolates in Khorramabad, Iran

BACKGROUND

Acinetobacter baumannii is an opportunistic hospital pathogen with high antibiotic resistance, and the ability to produce biofilm. This study aimed to investigate epsA, ompA, and bap genes involved in biofilm formation in MDR and XDR clinical isolates of Acinetobacter baumannii in Khorramabad, Iran.

METHODS

In this study, 79 A. baumannii isolates were collected from various samples of the patients admitted to tertiary hospitals in Khorramabad city, Iran, between January and August 2019. After performing the semi-quantitative evaluation of biofilm production by microtiter plate assay, screening of isolates carrying epsA, ompA, and bap genes was done by PCR method. Finally, statistical analyses were conducted using SPSS 22.

RESULTS

Among 79 A. baumannii isolates, 52% XDR, 40% MDR, and 16% non-XDRMDR isolates were found to be biofilm producers. All XDR and 94% MDR isolates had ompA and epsA genes, and bap genes were detected among > 80% of these isolates. Moreover, the presence of biofilm-related genes and biofilm production among non-XDRMDR isolates were less than among resistant isolates (p≤ 0.01).

CONCLUSION

Based on the results, biofilm production and simultaneous presence of epsA, ompA, and bap genes among MDR, and XDR A. baumannii isolates have been found to be significantly more than non-XDR-MDR isolates.

Efficacy of combination therapy with standard-dose carbapenem for treating nosocomial pneumonia caused by carbapenem-resistant Acinetobacter baumannii in intensive care units: A multicentre retrospective propensity score-matched study

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection is common worldwide. Despite carbapenem resistance, standard-dose carbapenems are still used in clinical practice. Hence in this study, we aimed to compare the efficacy and outcomes of a regimen containing standard-dose carbapenems with those of a regimen lacking carbapenems during the treatment of critically ill patients with CRAB nosocomial pneumonia in the intensive care unit (ICU). Initially, 735 patients were recruited for this multicentre retrospective cohort study. After exclusion, time-window bias adjustment, and propensity score matching, multiple clinical outcomes were compared between the carbapenem-containing (CC) (n = 166) and no carbapenem-containing (NCC) (n = 166) groups. The CC group showed a higher risk of clinical failure on day 7 than the NCC group (44.6% vs. 33.1%, P = 0.043). The lengths of ICU stay (21 and 16 days, P = 0.024) and hospital stay (61 and 44 days, P = 0.003) were longer in the CC group than in the NCC group. Multivariate analysis showed that the CC regimen was associated with higher clinical failure (adjusted odds ratio (aOR) = 1.64, 95% CI = 1.05-2.56, P = 0.031) and lower microbiological eradication (aOR = 0.48, 95% CI = 0.23-1.00, P = 0.049) at day 7 than the NCC group. Thus, a regimen containing a standard dose of carbapenem should be prescribed with caution for treating CRAB nosocomial pneumonia in the ICU.

Longitudinal study across SARS-CoV-2 variants identifies transcriptionally active microbes (TAMs) associated with Delta severity

Emergence of new SARS-CoV-2 VOCs jeopardize global vaccine and herd immunity safeguards. VOCs interactions with host microbiota might affect clinical course and outcome. This longitudinal investigation involving Pre-VOC and VOCs (Delta & Omicron) holo-transcriptome based nasopharyngeal microbiome at taxonomic levels followed by metabolic pathway analysis and integrative host-microbiome interaction. VOCs showed enrichment of Proteobacteria with dominance of Pseudomonas. Interestingly, Proteobacteria with superiority of Pseudomonas and Acinetobacter, were highlights of Delta VOC rather than Omicron. Common species comprising the core microbiome across all variants, reiterated the significance of Klebsiella pneumoniae in Delta, and its association with metabolic pathways enhancing inflammation in patients. Microbe-host gene correlation network revealed Acinetobacter baumannii, Pseudomonas stutzeri, and Pseudomonas aeuroginosa modulating immune pathways, which might augment clinical severity in Delta. Importantly, opportunistic species of Acinetobacter, Enterococcus, Prevotella, and Streptococcus were abundant in Delta-mortality. The study establishes a functional association between elevated nasal pathobionts and dysregulated host response, particularly for Delta.

Enzyme Patterns and Factors Associated with Mortality among Patients with Carbapenem Resistant AcinetobacterBaumannii (CRAB) Bacteremia: Real World Evidence from a Tertiary Center in India

Introduction

In the Indian setting, antimicrobial resistance in A. baumannii is a considerable problem, especially in intensive care units (ICUs). Due to the limited data, clinicians are left with very few choices except polymyxins for treating serious infections caused by A. baumannii. There is sparse data regarding the local mechanisms of resistance. Given the current therapeutic challenges, it is critical to know the local enzymatic patterns and antibiograms.

Materials and methods

A retrospective analysis of 50 episodes of bacteremia caused by CRAB. We analyzed the enzyme patterns and the susceptibility rates to various antibiotics.

Results

The resistance rates for amikacin, tigecycline, minocycline, and fluoroquinolones were 88, 82, 50, and 88% respectively. OXA-23 was the most commonly isolated enzyme (86% of the isolates produced OXA-23) followed by OXA-51 and NDM. The overall mortality was high (58%). On univariate analysis, pneumonia, and higher Pitt's bacteremia score were significantly associated with mortality (p = 0.04 and p = 0.001 respectively). Of the total patients who received combination therapy, a majority (58%) received polymyxin plus meropenem. Combination therapy using polymyxins as a backbone was not associated with reduced mortality (p = 0.1).

Conclusion

A. baumannii is associated with significant morbidity and mortality, as shown in our study. The rates of resistance for aminoglycosides were very high, and minocycline showed better susceptibility rates in comparison with tigecycline. In our study, OXA-23 and NDM remained the most important enzymes. The routine use of the combination of polymyxin and meropenem may not offer a significant advantage over monotherapy.

How to cite this article

Prayag PS, Patwardhan SA, Joshi RS, Panchakshari SP, Rane T, Prayag AP. Enzyme Patterns and Factors Associated with Mortality among Patients with Carbapenem Resistant Acinetobacter Baumannii (CRAB) Bacteremia: Real World Evidence from a Tertiary Center in India. Indian J Crit Care Med 2023;27(9):663-668.

Guidelines for the diagnosis, treatment, prevention and control of infections caused by carbapenem-resistant gram-negative bacilli

The dissemination of carbapenem-resistant Gram-negative bacilli (CRGNB) is a global public health issue. CRGNB isolates are usually extensively drug-resistant or pandrug-resistant, resulting in limited antimicrobial treatment options and high mortality. A multidisciplinary guideline development group covering clinical infectious diseases, clinical microbiology, clinical pharmacology, infection control, and guideline methodology experts jointly developed the present clinical practice guidelines based on best available scientific evidence to address the clinical issues regarding laboratory testing, antimicrobial therapy, and prevention of CRGNB infections. This guideline focuses on carbapenem-resistant Enterobacteriales (CRE), carbapenem-resistant Acinetobacter baumannii (CRAB), and carbapenem-resistant Pseudomonas aeruginosa (CRPA). Sixteen clinical questions were proposed from the perspective of current clinical practice and translated into research questions using PICO (population, intervention, comparator, and outcomes) format to collect and synthesize relevant evidence to inform corresponding recommendations. The grading of recommendations, assessment, development and evaluation (GRADE) approach was used to evaluate the quality of evidence, benefit and risk profile of corresponding interventions and formulate recommendations or suggestions. Evidence extracted from systematic reviews and randomized controlled trials (RCTs) was considered preferentially for treatment-related clinical questions. Observational studies, non-controlled studies, and expert opinions were considered as supplementary evidence in the absence of RCTs. The strength of recommendations was classified as strong or conditional (weak). The evidence informing recommendations derives from studies worldwide, while the implementation suggestions combined the Chinese experience. The target audience of this guideline is clinician and related professionals involved in management of infectious diseases.

Genome-wide identification and oxacillinase OXA distribution characteristics of Acinetobacter spp. based on a global database

Objective

To use genomic analysis to identify Acinetobacter spp. and to explore the distribution characteristics of ß-lactamase oxallicinases (blaOXA) among Acinetobacter species globally.

Methods

Genomes of global Acinetobacter spp. were downloaded from GenBank using Aspera batch. After quality check using CheckM and QUAST software, the genomes were annotated using Prokka software to investigate the distribution of blaOXAs across Acinetobacter spp.; a phylogenetic tree was constructed to explore the evolutionary relationship among the blaOXA genes in Acinetobacter spp. Average-nucleotide identification (ANI) was performed to re-type the Acinetobacter spp. BLASTN comparison analysis was implemented to determine the sequence type (ST) of Acinetobacter baumannii strain.

Results

A total of 7,853 genomes were downloaded, of which only 6,639 were left for further analysis after quality check. Among them, 282 blaOXA variants were identified from the genomes of 5,893 Acinetobacter spp.; blaOXA-23 (n = 3,168, 53.8%) and blaOXA-66 (2,630, 44.6%) were the most frequent blaOXAs, accounting for 52.6% (3,489/6639), and the co-carriage of blaOXA-23 and blaOXA-66 was seen in 2223 (37.7%) strains. The 282 blaOXA variants were divided into 27 clusters according to the phylogenetic tree. The biggest clade was blaOXA-51-family carbapenem-hydrolyzing enzymes composed of 108 blaOXA variants. Overall, 4,923 A. baumannii were identified out of the 6,639 Acinetobacter spp. strains and 291 distinct STs were identified among the 4,904 blaOXA-carrying A. baumannii. The most prevalent ST was ST2 (n = 3,023, 61.6%) followed by ST1 (n = 228, 4.6%).

Conclusion

OXA-like carbapenemases were the main blaOXA-type β-lactamase spread widely across Acinetobacter spp. Both blaOXA-23 and blaOXA-66 were the predominant blaOXAs, among all A. baumannii strains, with ST2 (belonging to CC2) being the main clone disseminated globally.

Tigecycline-Containing Regimens and Multi Drug-Resistant Acinetobacter baumannii: A Systematic Review and Meta-Analysis

Introduction: The use of tigecycline (TG) for the treatment of Acinetobacter baumannii is controversial. In this systematic review and meta-analysis, we aimed to better explore the safety and efficacy of TG for the treatment of multi drug-resistant (MDR) Acinetobacter. Methods: We searched PubMed/MEDLINE, Scopus, Cochrane Central, and Web of Science to identify studies reporting the clinical and microbiological efficacy and safety of regimens containing TG in patients with drug susceptibility testing (DST)-confirmed MDR A. baumannii, published until December 30, 2022. Observational studies were included if they reported clinical and microbiological efficacy of TG-based regimens. The Newcastle-Ottawa Scale (NOS) and Joana Briggs Institute (JBI) critical appraisal tool were used to assess the quality of included studies. Results: There were 30 observational studies, of which 19 studies were cohort and 11 studies were single group studies. Pooled clinical response and failure rates in the TG-containing regimens group were 58.1 (95% confidence interval [CI] 49.2-66.6) and 40.2 (95% CI 31.1-50.0), respectively. The pooled microbiological response rate was 32.1 (95% CI 19.8-47.5), and the pooled all-cause mortality rate was 41.1 (95% CI 34.1-48.4). Pooled clinical response and failure rates in the colistin-based regimens group were 52.7 (42.7-62.5) and 43.1 (33.1-53.8), respectively. The pooled microbiological response rate was 42.9 (16.2-74.5), and the pooled all-cause mortality rate was 34.3 (26.1-43.5). Conclusions: According to our results, the efficacy of the TG-based regimen is the same as other antibiotics. However, our study showed a high mortality rate and a lower rate of microbiological eradication for TG compared with colistin-based regimen. Therefore, our study does not recommend it for the treatment of MDR A. baumannii. However, this was a prevalence meta-analysis of observational studies, and for better conclusion experimental studies are required.

Comprehensive Assessment of Colistin Induced Nephrotoxicity: Incidence, Risk Factors and Time Course

Purpose

In recent years, the emergence of multidrug-resistant (MDR) microorganisms had caused the resurgence of colistin use after it was previously abandoned due to its side effects, nephrotoxicity in particular. However, the specific incidence of colistin-induced nephrotoxicity varies in reports with different populations. This study aims to assess the incidence of colistin-associated nephrotoxicity and the associated risk factors.

Patients and Methods

This study was on 178 patients who received colistin for more than 48 hours during the years 2019-2022, who were followed up for 14 days after the initiation of colistin, and demographic and clinical data were gained from medical reports. Logistic regression was used to assess the relationship between nephrotoxicity and study variables.

Results

The incidence of nephrotoxicity was 44.9% (95% confidence interval (CI); 37% to 53%), and the overall mortality was 33%, with a significantly higher level among patients with nephrotoxicity. The significant risk factors for nephrotoxicity after adjustment were; higher weights (OR = 1.1, 95% CI; 0.03-1.2), P-value: 0.006, and the combination with carbapenem showed a significant protective effect (OR = 0.09, 95% CI; 0.01-0.8), P-value: 0.03. The severity, according to KDIGO classification, was stage 1 (47%), stage 2 (21%), and stage 3 (31%). Higher stages had earlier onset acute kidney injury, a lower percentage of returning to baseline, and exposure to a higher colistin dose.

Conclusion

Colistin-induced nephrotoxicity was a frequent issue associated with higher weights, mitigated by the combination with carbapenems. While higher colistin dosages, and earlier onset AKI, were linked to the progression to higher AKI stages and the need for dialysis.

Navigating Available Treatment Options for Carbapenem-Resistant Acinetobacter baumannii-calcoaceticus Complex Infections

Carbapenem-resistant Acinetobacter baumannii-calcoaceticus complex (CRAB) is one of the top-priority pathogens for new antibiotic development. Unlike other antibiotic-resistant threats, none of the available therapies have been shown to consistently reduce mortality or improve patient outcomes in clinical trials. Antibiotic combination therapy is routinely used in clinical practice; however, the preferred combination has not been defined. This narrative review focuses on evidence-based solutions for the treatment of invasive CRAB infections. We dissect the promise and perils of traditional agents used in combination, such as colistin, sulbactam, and the tetracyclines, and offer clinical pearls based on our interpretation of the available data. Next, we investigate the merits of newly developed β-lactam agents like cefiderocol and sulbactam-durlobactam, which have demonstrated contrasting results in recent randomized clinical trials. The review concludes with the authors' perspective on the evolving treatment landscape for CRAB infections, which is complicated by limited clinical data, imperfect treatment options, and a need for future clinical trials. We propose that effective treatment for CRAB infections requires a personalized approach that incorporates host factors, the site of infection, pharmacokinetic-pharmacodynamic principles, local molecular epidemiology of CRAB isolates, and careful interpretation of antibiotic susceptibility testing results. In most clinical scenarios, a dose-optimized, sulbactam-based regimen is recommended with the addition of at least one other in vitro active agent. Should sulbactam-durlobactam receive regulatory approval, recommendations will need to be re-evaluated with the most recent evidence.

Evaluating the efficiency of a nomogram based on the data of neurosurgical intensive care unit patients to predict pulmonary infection of multidrug-resistant Acinetobacter baumannii

Background

Pulmonary infection caused by multidrug-resistant Acinetobacter baumannii (MDR-AB) is a common and serious complication after brain injury. There are no definitive methods for its prediction and it is usually accompanied by a poor prognosis. This study aimed to construct and evaluate a nomogram based on patient data from the neurosurgical intensive care unit (NSICU) to predict the probability of MDR-AB pulmonary infection.

Methods

In this study, we retrospectively collected patient clinical profiles, early laboratory test results, and doctors' prescriptions (66 variables). Univariate and backward stepwise regression analyses were used to screen the variables to identify predictors, and a nomogram was built in the primary cohort based on the results of a logistic regression model. Discriminatory validity, calibration validity, and clinical utility were evaluated using validation cohort 1 based on receiver operating characteristic curves, calibration curves, and decision curve analysis (DCA). For external validation based on predictors, we prospectively collected information from patients as validation cohort 2.

Results

Among 2115 patients admitted to the NSICU between December 1, 2019, and December 31, 2021, 217 were eligible for the study, including 102 patients with MDR-AB infections (102 cases) and 115 patients with other bacterial infections (115 cases). We randomly categorized the patients into the primary cohort (70%, N=152) and validation cohort 1 (30%, N=65). Validation cohort 2 consisted of 24 patients admitted to the NSICU between January 1, 2022, and March 31, 2022, whose clinical information was prospectively collected according to predictors. The nomogram, consisting of only six predictors (age, NSICU stay, Glasgow Coma Scale, meropenem, neutrophil to lymphocyte ratio, platelet to lymphocyte ratio), had significantly high sensitivity and specificity (primary cohort AUC=0.913, validation cohort 1 AUC=0.830, validation cohort 2 AUC=0.889) for early identification of infection and had great calibration (validation cohort 1,2 P=0.3801, 0.6274). DCA confirmed that the nomogram is clinically useful.

Conclusion

Our nomogram could help clinicians make early predictions regarding the onset of pulmonary infection caused by MDR-AB and implement targeted interventions.

The RND Efflux Pump Gene Expression in the Biofilm Formation of Acinetobacter baumannii

Multidrug resistant (MDR) Acinetobacter baumannii is a critical opportunistic pathogen in healthcare-associated infections (HAI). This is attributed to several factors, including its ability to develop biofilms that can enhance antimicrobial resistance (AMR) in addition to creating an environment for horizontal transfer of antibiotic resistance genes. The role of the efflux pump in biofilm formation is important for studies on alternative treatments for biofilms. One of the significant efflux pump families is the RND efflux pump family, which is common in Gram negative bacteria. The aim is to study the role of the RND efflux pump in biofilm formation by A. baumannii. The biofilm formation potential of thirty-four MDR A. baumannii isolates was evaluated by crystal violet assays. The effect of efflux pump inhibition and activation was studied using the efflux pump inhibitor carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and the RND efflux pump substrate levofloxacin (at sub-MIC), respectively. The isolates were genotypically grouped by enterobacterial repetitive intergenic consensus (ERIC) typing and the expression of adeABC, adeFGH, and adeIJK efflux pump genes was measured by qPCR. Overall, 88.2% (30/34) of isolates were biofilm producers (the phenotype was variable including strong and weak producers). Efflux pump inhibition by CCCP reduced the biofilm formation significantly (p < 0.05) in 17.6% (6/34) of some isolates, whereas sub-MICs of the substrate levofloxacin increased biofilm formation in 20.5% (7/34) of other isolates. Overexpression of the three RND efflux pump genes was detected in five out of eleven selected isolates for qPCR with remarkable overexpression in the adeJ gene. No correlation was detected between the biofilm phenotype pattern and the RND efflux pump gene expression in biofilm cells relative to planktonic cells. In conclusion, the role of the RND efflux pumps AdeABC, AdeFGH, and AdeIJK in biofilm formation does not appear to be pivotal and the expression differs according to the genetic background of each strain. Thus, these pumps may not be a promising target for biofilm inhibition.

In Vitro Synergistic Activity of Antimicrobial Combinations against Carbapenem- and Colistin-Resistant Acinetobacter baumannii and Klebsiella pneumoniae

Polymyxins are commonly used as the last resort for the treatment of MDR Acinetobacter baumannii and Klebsiella pneumoniae nosocomial infections; however, apart from the already known toxicity issues, resistance to these agents is emerging. In the present study, we assessed the in vitro synergistic activity of antimicrobial combinations against carbapenem-resistant and colistin-resistant A. baumannii and K. pneumoniae in an effort to provide more options for their treatment. Two hundred A. baumannii and one hundred and six K. pneumoniae single clinical isolates with resistance to carbapenems and colistin, recovered between 1 January 2021 and 31 July 2022,were included. A. baumannii were tested by the MIC test strip fixed-ratio method for combinations of colistin with either meropenem or rifampicin or daptomycin. K. pneumoniae were tested for the combinations of colistin with meropenem and ceftazidime/avibactam with aztreonam. Synergy was observed at: 98.99% for colistin and meropenem against A. baumannii; 91.52% for colistin and rifampicin; and 100% for colistin and daptomycin. Synergy was also observed at: 73.56% for colistin and meropenem against K. pneumoniae and; and 93% for ceftazidime/avibactam with aztreonam. The tested antimicrobial combinations presented high synergy rates, rendering them valuable options against A. baumannii and K. pneumoniae infections.

Clinical evidence supporting cefiderol for serious Acinetobacter baumannii infections

PURPOSE OF REVIEW

Nosocomial infections caused by Acinetobacter baumannii currently represent a serious challenge for clinicians because treatment options are limited and frequently associated with significant toxicity. Cefiderocol is a first-in-class siderophore cephalosporin that has a proven efficacy for the treatment of multidrug-resistant Gram-negative infections, including carbapenem-resistant A. baumannii. The aim of this review is to evaluate the current evidence for the role of cefiderocol in the management of A. baumannii infections.

RECENT FINDINGS

In this review, we briefly summarize the available data on the efficacy (from randomized controlled trials) and on effectiveness and cure rates (from observational studies), pertaining to the use of cefiderocol for treatment of serious A. baumannii infections.

SUMMARY

Cefiderocol represents a promising and safe antibiotic option for treating patients with carbapenem-resistant A. baumannii infections. Due to conflicting mortality data from available experience, well-designed future randomized controlled trials and real-life studies are needed.

The combination effect of meropenem/sulbactam/polymyxin-B on the pharmacodynamic parameters for mutant selection windows against carbapenem-resistant Acinetobacter baumannii

The objective of this study was to evaluate whether combinations of sulbactam, meropenem, and polymyxin-B could reduce or close the gap of mutant selection window (MSW) of individual antibiotics against Acinetobacter baumannii harboring OXA-23. MICs of three antimicrobials used alone and in combination (meropenem/polymyxin-B or meropenem/polymyxin-B/sulbactam) were obtained in 11 clinical isolates and mutant prevention concentrations were determined in 4 of the 11 isolates. All isolates were resistant to meropenem or polymyxin-B. Combining meropenem and polymyxin-B with or without sulbactam resulted in synergistic bactericidal activities. Pharmacokinetic (PK) simulations of drug concentrations in the blood and epithelial lining fluid coupled with pharmacodynamic (PD) evaluations revealed that the fractions of time over the 24-h in terms of free drug concentration within the MSW (fT_MSW) and above the MPC (fT_>MPC) were optimized by combination therapy. The resultant clinical regimens of meropenem, polymyxin-B, and sulbactam evaluated in the PK-PD analysis were 2 g q8h, 2.5 mg/kg loading dose followed by 1.5 mg/kg q12h, and 3 g q8h, respectively, in patients with normal renal function. Subsequent corresponding equivalent exposure regimens would depend on the extent of renal failure. The overall results indicate that combination antibiotics consisting of sulbactam/meropenem/polymyxin-B can confer potential efficacy against A. baumannii harboring OXA-23, and reduce the opportunity for bacteria to develop further resistance. This study provides a framework for pharmacodynamic evaluation of drug-resistant mutant suppression in an antimicrobial co-administration setting. The results thereby lay the groundwork for additional studies and future clinical confirmation is warranted.

Efficacy and Safety of Colistin versus Tigecycline for Multi-Drug-Resistant and Extensively Drug-Resistant Gram-Negative Pathogens-A Meta-Analysis

Background: We intended to compare the efficacy and safety outcomes of colistin versus tigecycline as monotherapy or combination therapy against multi-drug resistant (MDR) and extensively drug-resistant (XDR) pathogens. Methods: A search was conducted in PubMed, Cochrane CENTRAL, EMBASE, and in the grey literature (i.e., ClinicalTrials.gov and Google Scholar) up to May 2021. Outcomes were clinical response, mortality, infection recurrence, and renal and hepatic toxicity. We pooled odd ratios (OR) using heterogeneity-guided random or fixed models at a statistical significance of p < 0.05. Results: Fourteen observational studies involving 1163 MDR/XDR pathogens, receiving tigecycline versus colistin monotherapy or combination, were included. Base-case analyses revealed insignificant differences in the clinical response, reinfection, and hepatic impairment. The 30-day mortality was significantly relatively reduced with tigecycline monotherapy (OR = 0.35, 95% CI 0.16−0.75, p = 0.007). The colistin monotherapy significantly relatively reduced in-hospital mortality (OR = 2.27, 95%CI 1.24−4.16, p = 0.008). Renal impairment rates were lower with tigecycline monotherapy or in combination, and were lower with monotherapy versus colistin-tigecycline combination. Low-risk of bias and moderate/high evidence quality were associated with all studies. Conclusions: Within the limitations of this study, it can be concluded that there were no statistically significant differences in main efficacy outcomes between colistin and tigecycline monotherapies or combinations against MDR/XDR infections, except for lower rates of 30-day mortality with tigecycline and in-hospital mortality with colistin. Tigecycline was associated with favourable renal toxicity outcomes.

Incidence and Risk Factors of Colistin-Induced Nephrotoxicity Associated with The International Consensus Guidelines for the Optimal Use of the Polymyxins: A Retrospective Study in a Tertiary Care Hospital, Saudi Arabia

Background: Colistin is an effective therapy against multidrug-resistant gram-negative bacteria. However, nephrotoxicity is a major issue with its use. Objective: We aimed to evaluate the incidence and the potential risk factors of nephrotoxicity in colistin-treated patients. Methods: A retrospective cohort study was conducted. All adult patients aged 18 years and older who received colistin for ≥72 h were included in the study, while end-stage kidney disease patients requiring dialysis or had renal transplants were excluded. The incidence and severity of acute kidney injury (AKI) were assessed based on the Kidney Disease Improving Global Outcomes (KDIGO). Result: Out of 128 patients who received colistin, 51.56% of them have experienced AKI. The incidence was increased among oldest patients (above 80) and those who did not receive the appropriate dose (p-value = 0.0003). In addition, the median time until the AKI occurred was 10 days after receiving the colistin treatment. Rates of AKI in patients with previous AKI (71.7%) were three times higher than patients who did not previously experience AKI (HR = 2.97, 95% CI [1.8-4.8]). Conclusions: Nephrotoxicity is a significant issue among patients who receive colistin in the hospital, especially among older patients and those who did not receive the appropriate dose. As a result, healthcare providers should play a major role in colistin dosing, especially among the older adult population.

Prevalence of polymyxin-induced nephrotoxicity and its predictors in critically ill adult patients: A meta-analysis

BACKGROUND

Polymyxin-induced nephrotoxicity is a major safety concern in clinical practice due to long-term adverse outcomes and high mortality.

AIM

To conducted a systematic review and meta-analysis of the prevalence and potential predictors of polymyxin-induced nephrotoxicity in adult intensive care unit (ICU) patients.

METHODS

PubMed, EMBASE, the Cochrane Library and Reference Citation Analysis database were searched for relevant studies from inception through May 30, 2022. The pooled prevalence of polymyxin-induced nephrotoxicity and pooled risk ratios of associated factors were analysed using a random-effects or fixed-effects model by Stata SE ver. 12.1. Additionally, subgroup analyses and meta-regression were conducted to assess heterogeneity.

RESULTS

A total of 89 studies involving 12234 critically ill adult patients were included in the meta-analysis. The overall pooled incidence of polymyxin-induced nephrotoxicity was 34.8%. The pooled prevalence of colistin-induced nephrotoxicity was not higher than that of polymyxin B (PMB)-induced nephrotoxicity. The subgroup analyses showed that nephrotoxicity was significantly associated with dosing interval, nephrotoxicity criteria, age, publication year, study quality and sample size, which were confirmed in the univariable meta-regression analysis. Nephrotoxicity was significantly increased when the total daily dose was divided into 2 doses but not 3 or 4 doses. Furthermore, older age, the presence of sepsis or septic shock, hypoalbuminemia, and concomitant vancomycin or vasopressor use were independent risk factors for polymyxin-induced nephrotoxicity, while an elevated baseline glomerular filtration rate was a protective factor against colistin-induced nephrotoxicity.

CONCLUSION

Our findings indicated that the incidence of polymyxin-induced nephrotoxicity among ICU patients was high. It emphasizes the importance of additional efforts to manage ICU patients receiving polymyxins to decrease the risk of adverse outcomes.

Development and evaluation of a rapid and sensitive multienzyme isothermal rapid amplification with a lateral flow dipstick assay for detection of Acinetobacter baumannii in spiked blood specimens

Purpose

This study aimed to establish the multienzyme isothermal rapid amplification with a lateral flow dipstick (MIRA-LFD) assay and evaluate its performance in detection of A. baumannii in spiked blood specimens.

Methods

The study was divided into two stages: a pilot study to establish the methodology and a clinical validation study to evaluate its performance. In the first step, we designed primers specific to detect A. baumannii, optimized the MIRA-LFD assay and analyzed its performance regarding limits of detection, reproducibility, specificity, and efficiency of detection using real-time PCR method. In the second step, we obtained 50 spiked blood isolates and detected these pathogens by MIRA-LFD assay. The MIRA-LFD time was 15 min from DNA sample amplification to complete pathogen detection.

Results

The developed MIRA-LFD assay displayed a detection limit of 6 CFU/mL for detecting A. baumannii, which was significantly better than that of real-time PCR method, and no cross-reactivity was observed in other non-A. baumannii studied. The results obtained with 50 spiked blood isolates suggested that the developed MIRA-LFD assay had high specificity and sensitivity for identifying A. baumannii.

Conclusions

This study demonstrates that the established MIRA-LFD assay is time-saving, more effective and sensitive, which may become a powerful tool for rapid and reliable diagnosis of bloodstream infection caused by A. baumannii in primary hospitals.

Epidemiology, Mechanisms of Resistance and Treatment Algorithm for Infections Due to Carbapenem-Resistant Gram-Negative Bacteria: An Expert Panel Opinion

Antimicrobial resistance represents a serious threat for global health, causing an unacceptable burden in terms of morbidity, mortality and healthcare costs. In particular, in 2017, carbapenem-resistant organisms were listed by the WHO among the group of pathogens for which novel treatment strategies are urgently needed. Fortunately, several drugs and combinations have been introduced in recent years to treat multi-drug-resistant (MDR) bacteria. However, a correct use of these molecules is needed to preserve their efficacy. In the present paper, we will provide an overview on the epidemiology and mechanisms of resistance of the most common MDR Gram-negative bacteria, proposing a treatment algorithm for the management of infections due to carbapenem-resistant bacteria based on the most recent clinical evidence.

Efficacy of Fosfomycin against Planktonic and Biofilm-Associated MDR Uropathogenic Escherichia coli Clinical Isolates

Urinary tract infections (UTI) are a severe public health problem and are caused mainly by the uropathogenic Escherichia coli (UPEC). Antimicrobial resistance and limited development of new antimicrobials have led to the reuse of old antibiotics such as fosfomycin. The aim of this study was to evaluate the in vitro efficacy of fosfomycin on a collection of multidrug-resistant (MDR) UPEC and the degradative activity on biofilm producers. A total of 100 MDR UPEC clinical isolates were collected from patients at Mexican second- and third-level hospitals. Microorganism identification was performed using an automated system, the evaluation of the susceptibility of clinical isolates to fosfomycin was performed using the resazurin microtiter assay, and the identification of biofilm producers and the effect of fosfomycin in biofilms were evaluated using the crystal violet method. Among planktonic MDR UPEC, 93% were susceptible to fosfomycin. Eighty-three MDR UPEC were categorized as weak (39.8%), moderate (45.2%), and strong (14.5%) biofilm producers. Fosfomycin exhibited degradative activity ranging from 164.4 µg/mL to 1045 µg/mL. Weak producers required statistically lower concentrations of fosfomycin to destroy the biofilm, contrary to moderate and strong producers. In conclusion, fosfomycin could be an option for the treatment of infections caused by MDR UPEC, for which the antimicrobial treatment is more often becoming limited.

Resistance to beta-lactams in Gram-negative bacilli: relevance and potential therapeutic alternatives

The indiscriminate and massive antibiotic use in the clinical practice and in agriculture or cattle during the past few decades has produced a serious world health problem that entails high morbidity and mortality: the antibiotic multi-drug resistance. In 2017 and 2019, the World Health Organization published a list of urgent threats and priorities in the context of drug resistance, which only included Gram-negative bacteria and specially focused on carbapenem-resistant Acinetobacter baumannii and Pseudomonas aeruginosa, as well as carbapenem and third generation cephalosporin-resistant Enterobacteriaceae. This scenario emphasizes the need of developing and testing new antibiotics from different families, such as new beta-lactams, highlighting cefiderocol and its original mechanism of action; new beta-lactamase inhibitors, with vaborbactam or relebactam among others; new quinolones such as delafloxacin, and also omadacycline or eravacycline, as members of the tetracycline family. The present work reviews the importance and impact of Gram-negative bacterial infections and their resistance mechanisms, and analyzes the current therapeutic paradigm as well as the role of new antibiotics with a promising future in the era of multi and pan-drug resistance.

Pharmacokinetics and Pharmacodynamics of Colistin Methanesulfonate in Healthy Chinese Subjects after Multi-Dose Regimen

Colistin methanesulfonate (CMS) is an important treatment option for infections caused by carbapenem-resistant Gram-negative organisms (CROs). This study evaluated the pharmacokinetic/pharmacodynamic (PK/PD) profiles and safety of CMS in Chinese subjects following a recommended dosage. A total of 12 healthy Chinese subjects received CMS injections at 2.5 mg/kg once every 12 h for 7 consecutive days. The PK/PD profiles of the active form of CMS, colistin, against CROs were analyzed with the Monte Carlo simulation method. No serious adverse events were observed. The average steady-state plasma concentrations of CMS and colistin were 4.41 ± 0.75 μg/mL and 1.27 ± 0.27 μg/mL, and the steady-state exposures (AUC0−12,ss) were 52.93 ± 9.05 h·μg/mL and 15.28 ± 3.29 h·μg/mL, respectively. Colistin, at its minimum inhibitory concentration (MIC) of 0.5 μg/mL, has >90% probability to reduce CROs by ≥1 log. The PK/PD breakpoints for the ≥1 log kill were ≥MIC90 for carbapenem-resistant Klebsiella pneumoniae and Pseudomonas aeruginosa, but were ≤MIC50 for carbapenem-resistant Acinetobacter baumannii. The recommended dose regimen of CMS for 7 consecutive days was safe in Chinese subjects. The systemic exposure of colistin showed a high probability of being sufficient for most CROs, but was not sufficient for some carbapenem-resistant A. baumannii.

Diagnosis and management of infections caused by multidrug-resistant bacteria: guideline endorsed by the Italian Society of Infection and Tropical Diseases (SIMIT), the Italian Society of Anti-Infective Therapy (SITA), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Association of Clinical Microbiologists (AMCLI) and the Italian Society of Microbiology (SIM)

Management of patients with infections caused by multidrug-resistant organisms is challenging and requires a multidisciplinary approach to achieve successful clinical outcomes. The aim of this paper is to provide recommendations for the diagnosis and optimal management of these infections, with a focus on targeted antibiotic therapy. The document was produced by a panel of experts nominated by the five endorsing Italian societies, namely the Italian Association of Clinical Microbiologists (AMCLI), the Italian Group for Antimicrobial Stewardship (GISA), the Italian Society of Microbiology (SIM), the Italian Society of Infectious and Tropical Diseases (SIMIT) and the Italian Society of Anti-Infective Therapy (SITA). Population, Intervention, Comparison and Outcomes (PICO) questions about microbiological diagnosis, pharmacological strategies and targeted antibiotic therapy were addressed for the following pathogens: carbapenem-resistant Enterobacterales; carbapenem-resistant Pseudomonas aeruginosa; carbapenem-resistant Acinetobacter baumannii; and methicillin-resistant Staphylococcus aureus. A systematic review of the literature published from January 2011 to November 2020 was guided by the PICO strategy. As data from randomised controlled trials (RCTs) were expected to be limited, observational studies were also reviewed. The certainty of evidence was classified using the GRADE approach. Recommendations were classified as strong or conditional. Detailed recommendations were formulated for each pathogen. The majority of available RCTs have serious risk of bias, and many observational studies have several limitations, including small sample size, retrospective design and presence of confounders. Thus, some recommendations are based on low or very-low certainty of evidence. Importantly, these recommendations should be continually updated to reflect emerging evidence from clinical studies and real-world experience.

Colistin Monotherapy versus Colistin plus Meropenem Combination Therapy for the Treatment of Multidrug-Resistant Acinetobacter baumannii Infection: A Meta-Analysis

(1) Introduction: Colistin combination therapy with other antibiotics is a way to enhance colistin activity. The purpose of this meta-analysis was to compare the efficacy and safety of treatment with colistin monotherapy versus colistin plus meropenem combination therapy in patients with drug-resistant Acinetobacter baumannii infection. (2) Methods: All studies were included if they reported one or more of the following outcomes: clinical improvement, complete microbiological response, 14-day mortality, hospital mortality, or nephrotoxicity. (3) Results: Three randomized controlled trials and seven retrospective studies were included in the meta-analysis. Colistin monotherapy has similar rates of clinical improvement, 14-day mortality, hospital mortality, and nephrotoxicity as colistin plus meropenem combination therapy. Regarding complete microbiological response, the colistin plus meropenem combination was better than colistin monotherapy. (4) Discussion: Previous meta-analyses demonstrated heterogeneity in study quality and a lack of evidence supporting the use of colistin-based combination therapy. Our meta-analysis clearly showed that colistin combined with meropenem was not superior to colistin monotherapy for the treatment of Acinetobacter baumannii infection. (5) Conclusions: The efficacy and safety of treatment with colistin monotherapy and that of colistin plus meropenem combination therapy in patients with drug-resistant Acinetobacter baumannii infection were comparable. The majority of the evidence was obtained from nonrandomized studies, and high-quality randomized controlled trials are needed to confirm the role of colistin plus meropenem combination therapy in the treatment of multidrug-resistant Acinetobacter baumannii infection.

Recommendations and guidelines for the treatment of infections due to multidrug resistant organisms

Antimicrobial drug resistance is one of the major threats to global health. It has made common infections increasingly difficult or impossible to treat, and leads to higher medical costs, prolonged hospital stays and increased mortality. Infection rates due to multidrug-resistant organisms (MDRO) are increasing globally. Active agents against MDRO are limited despite an increased in the availability of novel antibiotics in recent years. This guideline aims to assist clinicians in the management of infections due to MDRO. The 2019 Guidelines Recommendations for Evidence-based Antimicrobial agents use in Taiwan (GREAT) working group, comprising of infectious disease specialists from 14 medical centers in Taiwan, reviewed current evidences and drafted recommendations for the treatment of infections due to MDRO. A nationwide expert panel reviewed the recommendations during a consensus meeting in Aug 2020, and the guideline was endorsed by the Infectious Diseases Society of Taiwan (IDST). This guideline includes recommendations for selecting antimicrobial therapy for infections caused by carbapenem-resistant Acinetobacter baumannii, carbapenem-resistant Pseudomonas aeruginosa, carbapenem-resistant Enterobacterales, and vancomycin-resistant Enterococcus. The guideline takes into consideration the local epidemiology, and includes antimicrobial agents that may not yet be available in Taiwan. It is intended to serve as a clinical guide and not to supersede the clinical judgment of physicians in the management of individual patients.