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

Evaluation of the efficacy of sulbactam combination therapy for monomicrobial and polymicrobial pulmonary infections caused by multidrug-resistant Acinetobacter baumannii

The efficacy in treatment of monomicrobial versus polymicrobial Acinetobacter baumannii (mono-AB vs poly-AB) pulmonary infections remains unclear. This study mainly investigated the efficacy of sulbactam combination regimens against mono-AB and poly-AB pulmonary infections. A multicenter retrospective study of adult patients who received sulbactam or cefoperazone/sulbactam for multidrug-resistant A. baumannii (MDRAB) between August 2021 and July 2023 was conducted. The outcomes of 7-day microbiological efficacy and 14-day clinical efficacy were measured. A total of 366 patients were enrolled, including 75 mono-AB patients. Among the 291 poly-AB cases, 82 patients were co-infected with Pseudomonas aeruginosa and 76 patients with Klebsiella pneumoniae. All A. baumannii isolates exhibited multidrug resistance. The antibiotics demonstrating the highest sensitivity against these isolates were polymyxins and tigecycline, with sensitivity rates of 91.25% and 71.63%, respectively. In the multivariable analysis, patients receiving sulbactam-based treatment for poly-AB pulmonary infections exhibited significantly higher microbial clearance of A. baumannii compared with those with mono-AB infections. Microbial efficacy analysis of A. baumannii co-infection with K. pneumoniae or P. aeruginosa showed similar results to overall poly-AB infections. Sulbactam doses ≥ 8 g/day showed the best microbiological and clinical efficacy. Sulbactam combined with tigecycline and/or polymyxins demonstrated significantly better microbiological efficacy compared with sulbactam alone. Sulbactam combined with polymyxins resulted in better microbiological and clinical efficacy than when combined with tigecycline. In conclusion, patients with poly-AB lung infections exhibit a higher microbial clearance rate of A. baumannii following treatment compared with those with mono-AB infections. A daily dose ≥8 g sulbactam may be optimal for treating MDRAB pneumonia. The combination of sulbactam and polymyxins demonstrates significant advantages over other sulbactam-containing regimens in terms of microbiological and clinical efficacy.IMPORTANCEThis is the first multicenter retrospective study to investigate the efficacy of sulbactam combination regimens in the treatment of monomicrobial and polymicrobial AB-related pulmonary infections. Our study found that patients receiving sulbactam-based treatment for poly-AB pulmonary infections exhibited significantly higher microbial clearance of A. baumannii compared with those with mono-AB infections. Microbial efficacy analysis of A. baumannii co-infection with K. pneumoniae or P. aeruginosa showed similar results to overall poly-AB infections. These findings are significantly important for further analyzing the potential mechanisms underlying the differences in efficacy between antimicrobial treatments for monomicrobial and polymicrobial infections, as well as for optimizing clinical antimicrobial combination strategies.

The prognostic value of neutrophil-to-lymphocyte ratio in adult carbapenem-resistant Klebsiella pneumoniae infection: a retrospective cohort study

Background

Systemic inflammatory indicators such as neutrophil-to-lymphocyte ratio (NLR) can effectively predict the prognosis of various inflammatory diseases. However, its prognostic effect on patients with carbapenem-resistant Klebsiella pneumoniae (CRKP) infection is little known. The objective of this study was to investigate the risk factors for mortality associated with CRKP infection and the clinical value of NLR in predicting prognosis in these patients.

Methods

A total of 190 inpatients with CRKP infection from 1 January 2023 to 31 December 2023 were enrolled in this study, namely, 73 fatal cases and 117 survival cases in hospital. The medical data and examination results of these patients were collected. A logistic regression analysis was performed to assess the association between the NLR on the day of CRKP infection onset and all-cause mortality in hospital.

Results

The overall mortality rate of patients with CRKP infection was 38.42% (73/190). Of the 190 patients, 91 were co-infected with carbapenem-resistant Acinetobacter baumannii/carbapenem-resistant Pseudomonas aeruginosa (CRAB/CRPA). Multifactor regression analysis confirmed that carbapenem exposure in the past 14 days, central line insertion, and chronic Foley catheter requirement were independent risk factors for carbapenem-resistant bacteria co-infection. The multivariate analysis shows that admission to an ICU, co-infection with CRAB/CRPA, and higher NLR were independent risk factors for the mortality in hospital, while appropriate treatment within 3 days was an independent protective factor. The area under the curve (AUC) of the NLR was 0.696, and the cutoff value of the NLR was 10.73.

Conclusions

The NLR on the day of CRKP infection onset, admission to an ICU, and co-infection with CRAB/CRPA were identified as independent risk factors for all-cause mortality of patients with CRKP infection, while appropriate treatment within 3 days was recognized as an independent protective factor. The NLR serves as a conveniently accessible and independent prognostic biomarker for patients with CRKP infection.

Engineered endolysin of Klebsiella pneumoniae phage is a potent and broad-spectrum bactericidal agent against "ESKAPEE" pathogens

The rise of antimicrobial resistance in ESKAPEE pathogens poses significant clinical challenges, especially in polymicrobial infections. Bacteriophage-derived endolysins offer promise in combating this crisis, but face practical hurdles. Our study focuses on engineering endolysins from a Klebsiella pneumoniae phage, fusing them with ApoE23 and COG133 peptides. We assessed the resulting chimeric proteins' bactericidal activity against ESKAPEE pathogens in vitro. ApoE23-Kp84B (CHU-1) reduced over 3 log units of CFU for A. baumannii, E. faecalis, K. pneumoniae within 1 h, while COG133-Kp84B (CHU-2) showed significant efficacy against S. aureus. COG133-L1-Kp84B, with a GS linker insertion in CHU-2, exhibited outstanding bactericidal activity against E. cloacae and P. aeruginosa. Scanning electron microscopy revealed alterations in bacterial morphology after treatment with engineered endolysins. Notably, CHU-1 demonstrated promising anti-biofilm and anti-persister cell activity against A. baumannii and E. faecalis but had limited efficacy in a bacteremia mouse model of their coinfection. Our findings advance the field of endolysin engineering, facilitating the customization of these proteins to target specific bacterial pathogens. This approach holds promise for the development of personalized therapies tailored to combat ESKAPEE infections effectively.

Antimicrobial Susceptibility Profiles of Acinetobacter baumannii Strains, Isolated from Clinical Cases of Companion Animals in Greece

Acinetobacter baumannii-calcoaceticus (Abc) Complex bacteria are troublesome nosocomial pathogens in human medicine, especially during the last 30 years. Recent research in veterinary medicine also supports its emergence as an animal pathogen. However, relevant data are limited. In this study, we obtained 41 A. baumannii isolates from clinical samples of canine and feline origin collected in veterinary clinics in Greece between 2020 and 2023. Biochemical identification, antimicrobial susceptibility testing, molecular identification and statistical analysis were performed. Most of the samples were of soft tissue and urine origin, while polymicrobial infections were recorded in 29 cases. Minocycline was the most effective in vitro antibiotic, whereas high resistance rates were detected for almost all the agents tested. Notably, 20 isolates were carbapenem resistant and 19 extensively drug resistant (XDR). This is the first report of canine and feline infections caused by Abc in Greece. The results create concerns regarding the capability of the respective bacteria to cause difficult-to-treat infections in pets and persist in veterinary facilities through hospitalized animals, contaminated equipment, and surfaces. Moreover, the prevalence of highly resistant strains in companion animals constitutes a public health issue since they could act as a reservoir, contributing to the spread of epidemic clones in a community.

Novel evidence on sepsis-inducing pathogens: from laboratory to bedside

Sepsis is a life-threatening condition and a significant cause of preventable morbidity and mortality globally. Among the leading causative agents of sepsis are bacterial pathogens Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pyogenes, along with fungal pathogens of the Candida species. Here, we focus on evidence from human studies but also include in vitro and in vivo cellular and molecular evidence, exploring how bacterial and fungal pathogens are associated with bloodstream infection and sepsis. This review presents a narrative update on pathogen epidemiology, virulence factors, host factors of susceptibility, mechanisms of immunomodulation, current therapies, antibiotic resistance, and opportunities for diagnosis, prognosis, and therapeutics, through the perspective of bloodstream infection and sepsis. A list of curated novel host and pathogen factors, diagnostic and prognostic markers, and potential therapeutical targets to tackle sepsis from the research laboratory is presented. Further, we discuss the complex nature of sepsis depending on the sepsis-inducing pathogen and host susceptibility, the more common strains associated with severe pathology and how these aspects may impact in the management of the clinical presentation of sepsis.

Predictors of Occurrence and 30-Day Mortality for Co-Infection of Carbapenem-Resistant Klebsiella pneumoniae and Carbapenem-Resistant Acinetobacter baumannii

Background

The phenomenon of co-infection with multiple carbapenem-resistant bacteria is growing, which pose a great challenge for infection control and treatment. This study aimed to analyze predictors of occurrence and 30-day mortality for carbapenem-resistant Klebsiella pneumoniae and carbapenem-resistant Acinetobacter baumannii co-infection.

Methods

From June 2018 to June 2021, clinical data of 103 patients co-infected with carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-resistant Klebsiella pneumoniae (CRKP) were collected from a tertiary teaching hospital in Anhui Province, China. The clinical characteristics and predictors of mortality were analyzed. Meanwhile, the bacterial isolates were characterized for drug susceptibility, multi-locus sequence typing, and drug resistance genes.

Results

The multivariate analysis revealed that fiberoptic bronchoscopy (p = 0.005, OR=2.72), repeat transfusions (p = 0.008, OR= 2.23) and exposure to tigecycline (p = 0.002, OR = 6.58) were independent risk factors for CRKP and CRAB co-infection. Neutrophil ≥11.9*109 (p = 0.035, adjusted HR = 3.12) and C-reactive protein ≥ 149 mg/L (p = 0.009, adjusted HR = 4.41) were found associated with 30-day mortality. Combined neutrophil with C-reactive protein could predict 30-day mortality, of which AUC value was 0.791 (95%CI: 0.661-0.921). KPC (46/51, 90.2%) was the most common carbapenemase in CRKP. 33 isolates of CRKP belong to ST11 (33/51, 64.7%), and three new ST types ST5882, ST5883, ST5885 were detected.

Conclusions

Invasive operations and antibiotics exposure can lead to CRKP and CRAB co-infection. Combined neutrophil with C-reactive protein could predict 30-day mortality.