Infection control management and surveillance of carbapenem-resistant Gram-negative bacteria in hematopoietic stem cell recipients

Laboratory detection of carbapenemases among Gram-negative organisms

SUMMARYThe carbapenems remain some of the most effective options available for treating patients with serious infections due to Gram-negative bacteria. Carbapenemases are enzymes that hydrolyze carbapenems and are the primary method driving carbapenem resistance globally. Detection of carbapenemases is required for patient management, the rapid implementation of infection prevention and control (IP&C) protocols, and for epidemiologic purposes. Therefore, clinical and public health microbiology laboratories must be able to detect and report carbapenemases among predominant Gram-negative organisms from both cultured isolates and direct from clinical specimens for treatment and surveillance purposes. There is not a "one size fits all" laboratory approach for the detection of bacteria with carbapenemases, and institutions need to determine what fits best with the goals of their antimicrobial stewardship and IP&C programs. Luckily, there are several options and approaches available for clinical laboratories to choose methods that best suits their individual needs. A laboratory approach to detect carbapenemases among bacterial isolates consists of two steps, namely a screening process (e.g., not susceptible to ertapenem, meropenem, and/or imipenem), followed by a confirmation test (i.e., phenotypic, genotypic or proteomic methods) for the presence of a carbapenemase. Direct from specimen testing for the most common carbapenemases generally involves detection via rapid, molecular approaches. The aim of this article is to provide brief overviews on Gram-negative bacteria carbapenem-resistant definitions, types of carbapenemases, global epidemiology, and then describe in detail the laboratory methods for the detection of carbapenemases among Gram-negative bacteria. We will specifically focus on the Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex.

Risk factors and molecular epidemiology of intestinal colonization by carbapenem-resistant Gram-negative bacteria in patients with hematological diseases: a multicenter case‒control study

Patients with hematological diseases are considered to be at high risk for intestinal colonization by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the epidemiological data regarding risk factors and molecular characteristics of intestinal colonized CR-GNB isolates in this population are insufficient in China. A multicenter case‒control study involving 4,641 adult patients with hematological diseases from 92 hospitals across China was conducted. Following culture of collected rectal swabs, mass spectrometry and antimicrobial susceptibility tests were performed to identify GNB species and CR phenotype. Risk factors were assessed through retrospective clinical information. Whole-genome sequencing was used to analyze the molecular characteristics of CR-GNB isolates. This trial is registered with ClinicalTrials.gov as NCT05002582. Our results demonstrated that among 4,641 adult patients, 10.8% had intestinal colonization by CR-GNB. Of these, 8.1% were colonized by carbapenem-resistant Enterobacterales (CRE), 2.6% were colonized by carbapenem-resistant Pseudomonas aeruginosa (CRPA), and 0.3% were colonized by carbapenem-resistant Acinetobacter baumannii (CRAB). The risk factors for CR-GNB colonization include male gender, acute leukemia, hematopoietic stem cell transplantation, β-lactam antibiotic usage, and the presence of non-perianal infections within 1 week. Compared with CRPA-colonized patients, patients using carbapenems were more likely to be colonized with CRE. NDM was the predominant carbapenemase in colonized CRE. This study revealed a high CR-GNB intestinal colonization rate among adult patients with hematological diseases in China, with CRE being the predominant one. Notably, a significant proportion of CRE exhibited metallo-β-lactamase production, indicating a concerning trend. These findings emphasize the importance of active screening for CR-GNB colonization in patients with hematological diseases.IMPORTANCECarbapenem-resistant Gram-negative bacteria (CR-GNB) has emerged as a significant threat to public health. Patients with hematological diseases are at high risk of CR-GNB infections due to their immunosuppressed state. CR-GNB colonization is an independent risk factor for subsequent infection. Understanding the risk factors and molecular characteristics of CR-GNB associated with intestinal colonization in patients with hematological diseases is crucial for empirical treatment, particularly in patients with febrile neutropenia. However, the epidemiology data are still insufficient, and our study aims to determine the intestinal colonization rate of CR-GNB, identify colonization risk factors, and analyze the molecular characteristics of colonized CR-GNB isolates.

[Key microbial monitoring and clinical analysis of bloodstream infections and CRO colonization after hematopoietic stem cell transplantation in hematological patients]

Objective: To investigate the distribution and clinical characteristics of pathogenic bacteria following hematopoietic stem cell transplantation (HSCT), as well as to provide a preliminary research foundation for key microbial monitoring, and clinical diagnosis and treatment of infections after HSCT in hematological patients. Methods: We retrospectively analyzed the clinical data of 190 patients who tested positive for microbial testing [G-bacteria blood culture and/or carbapenem-resistant organism (CRO) screening of perianal swabs] at our center from January 2018 to December 2022. Patients were divided into blood culture positive, perianal swab positive, and double positive groups based on the testing results. The three patient groups underwent statistical analysis and comparison. Results: The top four pathogenic bacteria isolated from sixty-three patients with G-bacteria bloodstream infection (BSI) were Escherichia coli (28 strains, 43.75% ), Klebsiella pneumonia (26 strains, 40.63% ), Pseudomonas aeruginosa (3 strains, 4.69% ), and Enterobacter cloacae (3 strains, 4.69% ). The top three pathogenic bacteria isolated from 147 patients with CRO perianal colonization were carbapenem-resistant Klebsiella pneumoniae (58 strains, 32.58% ), carbapenem-resistant Escherichia coli (49 strains, 27.53% ), and carbapenem-resistant Enterobacter cloacae (20 strains, 11.24% ). The 3-year disease-free survival (DFS ) and overall survival (OS) of double positive group patients were significantly lower compared to those in the blood culture and perianal swab positive groups (DFS: 35.6% vs 53.7% vs 68.6%, P=0.001; OS: 44.4% vs 62.4% vs 76.9%, P<0.001), while non-relapse mortality (NRM) was significantly higher (50.0% vs 34.9% vs 10.6%, P<0.001). Failed engraftment of platelets and BSI are independent risk factors for NRM (P<0.001). Using polymyxin and/or ceftazidime-avibactam for more than 7 days is an independent protective factor for NRM (P=0.035) . Conclusion: This study suggests that the occurrence of BSI significantly increases the NRM after HSCT in patients with hematological diseases; CRO colonization into the bloodstream has a significant impact on the DFS and OS of HSCT patients.

Prevalence and factors associated with carbapenem-resistant Enterobacterales (CRE) infection among hematological malignancies patients with CRE intestinal colonization

BACKGROUND

Knowledge about the prevalence, factors and mortality associated with subsequent carbapenem-resistant Enterobacterales (CRE) infection among hematological malignancies (HM) patients colonized with CRE is limited.

METHODS

HM patients were screened for rectal CRE. A retrospective case-control study of subsequent CRE infection among HM patients colonized with CRE was conducted between January 1st, 2020 and January 31st, 2022. Cases were defined as CRE colonized patients with subsequent infection and controls were those without infection. Bacterial identification was performed using MALDI Biotyper and antimicrobial susceptibility testing of strains was carried out using the VITEK 2 system or standard broth microdilution method. Logistic analysis was used for analyzing associated factors and Kaplan-Meier method was used for survival estimates.

RESULTS

A total of 953 HM patients were screened for rectal CRE and 98 (10.3%, 98/953) patients were colonized with CRE. Among the 98 colonized patients, 18 (18.4%, 18/98) patients developed subsequent infection. Most of the colonizing CRE isolates were Klebsiella pneumoniae (50.0%, 27/54), followed by Escherichia coli (27.8%, 15/54) and Enterobacter cloacae (9.3%, 5/54). As for the subsequent infecting CRE isolates, the dominated species was K. pneumoniae (55.6%, 10/18), followed by E. coli (33.3%, 6/18) and others (11.2%, 2/18). Receiving proton pump inhibitors and admission to ICU (P < 0.05) were the associated factors. Patients with subsequent CRE infection had significant higher mortality (33.3% vs 2.8%, P = 0.001) and shock was an associated factor (P = 0.008).

CONCLUSIONS

Klebsiella pneumoniae was the dominate colonizing species and subsequent infecting species among HM patients with CRE colonization. Receiving proton pump inhibitors and admission to ICU increased the risk of subsequent CRE infection among CRE colonized HM patients. Implementing strict infection control measures targeting those high- risk patients may prevent subsequent CRE infection.

Prognostic Risk Factors of Carbapenem-Resistant Gram-Negative Bacteria Bloodstream Infection in Immunosuppressed Patients: A 7-Year Retrospective Cohort Study

Purpose

Carbapenem-resistant Gram-negative bacteria bloodstream infection (CRGNB-BSI) has gradually become a major threat worldwide due to its treatment difficulty and high mortality. This study aimed to determine the risk factors for CRGNB-BSI in immunosuppressed patients.

Patients and Methods

A total of 427 immunosuppressed patients with CRGNB-BSI were retrospectively investigated from 2015 to 2021. Both univariate and multivariate logistic regression analyses were applied to evaluate independent risk factors for CRGNB-BSI.

Results

The most common etiology was Klebsiella Pneumoniae (50.59%; 216/427), while the Acinetobacillus baumannii infection was associated with the highest mortality (58.25%) among all etiologies. The 60-day mortality of immunosuppressed patients with CRGNB-BSI was 52.48% (224/427). Procalcitonin (PCT) > 0.5 μg/L (OR = 2.32, 95% CI: 1.28-4.19, P = 0.005) and age > 55 years (OR = 2.06, 95% CI: 1.17-3.64, P = 0.012) were found to be predictors of 60-day mortality of CRGNB-BSI, and tigecycline regimen (OR = 3.20, 95% CI: 1.81-5.67, P < 0.001) was associated with higher mortality. Multivariate analysis also revealed that patients who developed acute kidney injury (AKI) (OR = 2.19, 95% CI: 1.11-4.30, P = 0.023), gastrointestinal bleeding (OR = 3.18, 95% CI: 1.10-9.16, P = 0.032), multiple organ dysfunction syndrome (MODS) (OR = 12.11, 95% CI: 2.61-56.19, P = 0.001), and septic shock (OR = 3.24, 95% CI: 1.77-5.94, P < 0.001) showed worse outcomes. The risk factors were also significantly associated with mortality in the different subgroups.

Conclusion

This study demonstrated that PCT > 0.5 μg/L, age > 55 years, and the tigecycline regimen were significantly associated with higher 60-day mortality among immunosuppressed patients with CRGNB- BSI. Patients developing MODS, septic shock, or AKI had worse clinical outcomes. .

Do weekly surveillance cultures contribute to antibiotic stewardship and correlate with outcome of HSCT in children - a multicentre real-world experience of 5 years from Indian subcontinent?

BACKGROUND

The utility of weekly rectal swab surveillance cultures (RSSC) as a resource to identify gut colonisation with Extended Spectrum Beta-Lactamase (ESBL)-producing E Coli or Klebsiella pneumoniae carbapenemase (KPC) producing organisms, to guide empirical antibiotic therapy in HSCT patients continues to be a subject of interest. There is urgency to assess and justify modifications to empirical antibiotics based upon regional epidemiology and patient groups.

OBJECTIVE

To study the utility of weekly rectal swab surveillance cultures (RSSC) to guide empirical antibiotics therapy and the impact of gut colonisation on transplant outcomes.

STUDY DESIGN

This is a retrospective analysis of 317 successive first transplants done in three pediatric bone marrow transplant centres in Indian sub-continent, mainly for hemoglobinopathies, between April 2016 and April 2021. Transplantation, infection control and febrile neutropenia management protocols are identical among the three centres. First line antibiotics were chosen based on RCCS reports i.e. meropenem and high dose meropenem with colistin for ESBL and carbapenemase resistant colonisation respectively for first half of the study and no adjustment was made in the second half. Clinical response to antibiotics, long term outcomes, antibiotic-resistant bacteraemia and acute GVHD were analysed. Log-rank test, Chi-squared test and Wilcoxon test were used to compare data using R Statistical software.

RESULTS

Of all 871 weekly RSSC done, 162 were positive for ESBL- or KPC-resistant organism. RCCS were ESBL-positive in 106 patients (33%) and KPC-positive in 10 patients (3%). Within 97 ESBL-positive patients for whom antimicrobial susceptibility testing (AST) report was available, only 22 (25%) demonstrated clinical resistance of Pip-Taz. Within the 10 KPC-positive patients' clinical resistance was observed only in 4 (40%) to Pip-Taz and 3 (30%) to meropenem. For ESBL-positive RSSC where 1st line empirical antibiotics were used, 66% of the patients responded clinically. Even within the 15 who were resistant to 1st line empirical antibiotics (Pip-Taz) on RSSC reports, 67% responded to Pip-Taz clinically. Within these patients 27 (56%) never needed any carbapenems. Using Pip-Taz empirically in ESBL-positive patients did not prolong meropenem use within 100 days of transplantation (p=0.18). For KPC-positive RSSC where 1st line empirical antibiotics were used, all patients clinically responded, including 4 who were resistant to Pip-Taz and 3 patients who were meropenem resistant on RCCS. Comparing patients who were ESBL-positive, KPC-positive and neither, no statistically significant difference was seen in overall survival (p=0.95), disease free survival (p=0.45), transplant related mortality (p=0.97), rejection (p=0.68) and rate of acute GVHD grade II-IV (p=0.78). Comparing the ESBL-positive patients who did and did not get higher-level empirical antibiotics, no statistical difference was seen in overall survival (p=0.32), disease free survival (p=0.64), transplant related mortality (p=0.65), rejection (p=0.46), acute GVHD grade II-IV (p=0.26) or antibiotic resistant bacteraemia (p=0.3).

CONCLUSIONS

In context of transplantation for non-malignant HSCTs, empiric antibiotic choice based on rectal swab surveillance cultures is not justified, even in regions with a high prevalence of antimicrobial resistance. Antimicrobial susceptibility testing (AST) reports in surveillance cultures did not correlate with in-vivo clinical response. Colonisation reported on weekly surveillance rectal swab cultures showed no correlation with clinical outcomes.

Effectiveness of surveillance cultures for high priority multidrug-resistant bacteria in hematopoietic stem cell transplant units

Surveillance strategies to detect colonization are an important tool to prevent and control the spread of microorganisms in hematopoietic stem cell transplant (HSCT) units. The aim of this study was to evaluate routine surveillance cultures for screening colonization and infection by carbapenem-resistant Enterobacteriaceae (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPa), and vancomycin-resistant enterococci (VRE). Surveillance cultures were collected (1,323 samples) from 200 patients admitted to an HSCT unit over one year; swabs were taken on admission and then weekly. We compared the positivity of cultures for each site, agent, clinical and epidemiological data according to the colonization status. Infection due to multidrug-resistant organisms (MDROs) occurred in 52 (21.5%) patients, 45 (86.5%) due to blood stream infection; 12 (23%) patients had a positive surveillance culture before the infection. Cultures of 554 (41.8%) samples were performed for CRPa, 413 (31.2%) for VRE and 356 (27%) for CRE. Of these, 179 (13.5%) were positive. Colonization by any MDRO, CRE or CRPa was associated with increased risk of infection (P < 0.05), but not with death. Previous colonization by an MDRO was a significant risk for infection by these pathogens, specially by CRE. Overall, rectal swabs had the highest positivity rate compared with other sites, oropharynx swabs were an option for CRPa, and fecal cultures showed low positivity. Although the impact of the strategy on the mortality of patients undergoing HSCT is not clear, routine VRE surveillance should be questioned with regard to patients undergoing auto-HSCT due to the additional cost and little impact on survival rates.

Is it time to reconsider prophylactic antimicrobial use for hematopoietic stem cell transplantation? a narrative review of antimicrobials in stem cell transplantation

INTRODUCTION

Hematopoietic Stem Cell Transplantation (HSCT) is a life-saving procedure for multiple types of hematological cancer, autoimmune diseases, and genetic-linked metabolic diseases in humans. Recipients of HSCT transplant are at high risk of microbial infections that significantly correlate with the presence of graft-versus-host disease (GVHD) and the degree of immunosuppression. Infection in HSCT patients is a leading cause of life-threatening complications and mortality.

AREAS COVERED

This review covers issues pertinent to infection in the HSCT patient, including bacterial and viral infection; strategies to reduce GVHD; infection patterns; resistance and treatment options; adverse drug reactions to antimicrobials, problems of antimicrobial resistance; perturbation of the microbiome; the role of prebiotics, probiotics, and antimicrobial peptides. We highlight potential strategies to minimize the use of antimicrobials.

EXPERT OPINION

Measures to control infection and its transmission remain significant HSCT management policy and planning issues. Transplant centers need to consider carefully prophylactic use of antimicrobials for neutropenic patients. The judicious use of appropriate antimicrobials remains a crucial part of the treatment protocol. However, antimicrobials' adverse effects cause microbiome diversity and dysbiosis and have been shown to increase morbidity and mortality.