Meropenem Versus Piperacillin-Tazobactam for Definitive Treatment of Bloodstream Infections Caused by AmpC β-Lactamase-Producing Enterobacter spp, Citrobacter freundii, Morganella morganii, Providencia spp, or Serratia marcescens: A Pilot Multicenter Randomized Controlled Trial (MERINO-2)

Efficacy of carbapenems and alternative antimicrobials for treating complicated urinary tract infections caused by third-generation cephalosporin-resistant gram-negative bacteria: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Specific data concerning the efficacy of alternative antibiotics for carbapenems against complicated urinary tract infections (cUTIs) attributed to antimicrobial-resistant (AMR) uropathogens are lacking.

OBJECTIVES

This study aimed to assess the efficacy of carbapenems and non-carbapenem antibiotics in the clinical outcomes of cUTIs caused by AMR uropathogens.

METHODS

In this systematic review and meta-analysis, databases, including MEDLINE/PubMed, the Cochrane Library, Embase and ClinicalTrials.gov, were searched. The study eligibility criteria were research articles conducted as randomised controlled trials that evaluated the composite outcomes of cUTIs. Participants were adult patients with cUTIs caused by gram-negative uropathogens resistant to third-generation cephalosporins. The intervention involved a non-carbapenem class of antimicrobial agents with in vitro activities against gram-negative uropathogens resistant to third-generation cephalosporins. Two independent researchers assessed the risk-of-bias using the second version of the Cochrane risk-of-bias tool for randomised trials. The treatment effects on each outcome were estimated as a risk ratio (RR) with a 95 % confidence interval (CI) using the random-effects model. Heterogeneity was assessed using the Cochrane Q-test and I2 statistics.

RESULTS

Through database searches, 955 articles were retrieved. After screening the titles and abstracts, 52 articles were screened in full text. Finally, 12 studies met the inclusion criteria. No significant differences in efficacy were observed between alternative antibiotics and carbapenems (composite outcome, RR, 0.96; 95 % CI, 0.63-1.49; I2 = 21 %; low certainty of evidence).

CONCLUSIONS

Alternative antibiotics had clinical efficacy similar to that of carbapenems for treating patients with cUTI caused by gram-negative uropathogens resistant to third-generation cephalosporins.

Ceftriaxone versus cefepime or carbapenems for definitive treatment of low-risk AmpC-Harboring Enterobacterales bloodstream infections in hospitalized adults: A retrospective cohort study

OBJECTIVE

To compare outcomes of ceftriaxone to AmpC-stable therapies in patients with bacteremia caused by low-risk AmpC harboring Enterobacterales.

METHODS

IRB-approved, retrospective cohort of hospitalized patients ≥18 years old with Serratia marcescens, Morganella morganii, or Providencia spp. bacteremia from 1/1/2017-2/28/2024. Patients were compared by definitive therapy with ceftriaxone vs AmpC-stable therapy (cefepime, carbapenem). The primary endpoint was 30-day all-cause mortality; secondary endpoints were clinical failure and development of ceftriaxone resistance.

RESULTS

163 patients were included; 33.1 % received ceftriaxone, 66.9 % AmpC-stable therapies. 30-day all-cause mortality was 9.3 % ceftriaxone vs 10.1 % AmpC stable patients (P = 0.87); ceftriaxone definitive therapy was not associated with 30-day all-cause mortality (adjOR, 0.79; 95 %CI, 0.23-2.3). There were no differences in clinical failure (9.3 % vs 21.1 %, P = 0.059) or relapsing infection (5.6 % vs 9.3 %, P = 0.55) between ceftriaxone and AmpC-stable treated patients.

CONCLUSIONS

Patients treated with definitive ceftriaxone for low-risk AmpC Enterobacterales bacteremia had similar outcomes to AmpC stable therapies.

Treatment of multidrug-resistant Gram-negative bloodstream infections in critically ill patients: an update

PURPOSE OF REVIEW

This review describes the latest information in the management of bloodstream infections caused by multidrug-resistant Gram-negative bacilli (MDRGNB) in critically ill patients.

RECENT FINDINGS

The prevalence of bloodstream infections due to MDRGNB is high, and they pose a significant risk in critically ill patients. Recently, novel antimicrobial agents, including new β-lactam/β-lactamase inhibitor combinations and cefiderocol, have been introduced for treating these infections. Concurrently, updated guidelines have been issued to aid in treatment decisions. Prompt diagnosis and identification of resistance patterns are crucial for initiating effective antibiotic therapy. Current studies, especially with observational design, and with limited sample sizes and patients with bacteremia, suggest that the use of these new antibiotics is associated with improved outcomes in critically ill patients with MDRGNB bloodstream infections.

SUMMARY

For critically ill patients with bloodstream infections caused by MDRGNB, the use of newly developed antibiotics is recommended based on limited observational evidence. Further randomized clinical trials are necessary to determine the most effective antimicrobial therapies among the available options.

Amikacin treatment in patients with Enterobacterales bacteraemia: impact of MIC on mortality

BACKGROUND

Recently, breakpoints of Enterobacterales to amikacin were changed from MIC ≤ 16 mg/L to MIC ≤ 4 mg/L based mainly on laboratory data with little supporting clinical evidence. Our aim was to investigate the relation between MIC of Enterobacterales to amikacin and mortality among patients with Enterobacterales bacteraemia from a urinary tract source treated with amikacin.

PATIENTS AND METHODS

This retrospective, single-centre study included patients with Enterobacterales urinary source bacteraemia treated with amikacin, with Low (MIC ≤ 4 mg/L) and High (MIC 8 or 16 mg/L) MICs. A cohort of patients treated with ertapenem was used to assess if amikacin MIC is a marker of severity independent of antimicrobial treatment. The primary outcome was 30-day mortality. Multivariate logistic regression analysis was done to assess risk factors for mortality.

RESULTS

We included 85 patients, 46 (54.1%) were male, and mean age was 79.0 years (SD 11.7). Sixty-one patients (71.8%) had Low MIC and 24 (28.2%) had High MIC. Thirty-day mortality was 8.2% and 29.2% in the Low and High MIC groups, respectively (P = 0.031). Risk factors for 30-day mortality were age, infection by Enterobacterales other than Escherichia coli and high amikacin MIC. In a cohort of 88 patients treated with ertapenem, amikacin MIC was not associated with 30-day mortality.

CONCLUSIONS

We demonstrated a relation between higher amikacin MIC levels (8 and 16 mg/L) and increased 30-day mortality in patients treated with amikacin for bacteraemia secondary to a urinary source. These findings support the new CLSI breakpoint change of Enterobacterales to amikacin.

Antibiotic Treatment of Infections Caused by AmpC-Producing Enterobacterales

AmpC enzymes are a class of beta-lactamases produced by Gram-negative bacteria, including several Enterobacterales. When produced in sufficient amounts, AmpCs can hydrolyze third-generation cephalosporins (3GCs) and piperacillin/tazobactam, causing resistance. In Enterobacterales, the AmpC gene can be chromosomal- or plasmid-encoded. Some species, particularly Enterobacter cloacae complex, Klebsiella aerogenes, and Citrobacter freundii, harbor an inducible chromosomal AmpC gene. The expression of this gene can be derepressed during treatment with a beta-lactam, leading to AmpC overproduction and the consequent emergence of resistance to 3GCs and piperacillin/tazobactam during treatment. Because of this phenomenon, the use of carbapenems or cefepime is considered a safer option when treating these pathogens. However, many areas of uncertainty persist, including the risk of derepression related to each beta-lactam; the role of piperacillin/tazobactam compared to cefepime; the best option for severe or difficult-to-treat cases, such as high-inoculum infections (e.g., ventilator-associated pneumonia and undrainable abscesses); the role of de-escalation once clinical stability is obtained; and the best treatment for species with a lower risk of derepression during treatment (e.g., Serratia marcescens and Morganella morganii). The aim of this review is to collate the most relevant information about the microbiological properties of and therapeutic approach to AmpC-producing Enterobacterales in order to inform daily clinical practice.

The impact of meropenem shortage and post-prescription review and feedback on broad-spectrum antimicrobial use: An interrupted time-series analysis

Background

Meropenem (MEPM) holds significance in treating severe infections and drug-resistant bacteria. There are concerns that antimicrobial shortages may lead to the use of alternative antimicrobials that are less effective and safer. We have responded to the MEPM shortage with post-prescription monitoring and feedback (PPRF) with no restrictions on MEPM initiation. We aimed to assess the impact of the MEPM shortage and the PPRF on broad-spectrum antimicrobial use and mortality.

Methods

This retrospective study was conducted in a single hospital in Japan. The period from October 2021 to August 2022 was defined as the period before the MEPM shortage, and the period from September 2022 to March 2023 was defined as the period during the MEPM shortage. To support the appropriate use of antimicrobials during MEPM shortages, the antimicrobial stewardship team (AST) developed a list of alternatives to MEPM. An interrupted time series analysis was used to assess changes in use and mortality among patients receiving broad-spectrum antimicrobials over the study period.

Discussion

The shortage of MEPM and PPRF temporarily increased the use of alternative cefepime; however, the subsequent change in days of therapy and days of coverage of broad-spectrum antimicrobials suggests a decrease in the use of these antimicrobials. Despite these shifts, the mortality rates remained stable, suggesting that the response to the shortage did not adversely affect treatment outcomes.

Conclusion

In the context of antimicrobial shortages, AST support plays an important role in enabling physicians to make optimal use of antimicrobials.

The crucial relationship between vancomycin minimum inhibitory concentration and therapeutic efficacy against methicillin-resistant coagulase-negative staphylococci

The area under the curve (AUC)/minimum inhibitory concentration (MIC) ratio was used as an indicator of the clinical efficacy of vancomycin. However, the target AUC/MIC has not been set for methicillin-resistant coagulase-negative staphylococci (MR-CNS), and the effectiveness of vancomycin in strains with high MIC is unknown. Therefore, we aimed to investigate the relationship between the vancomycin MIC and therapeutic efficacy in patients with MR-CNS bacteremia. The primary outcome was the difference in treatment failure rate when the MR-CNS vancomycin MIC was 1 or 2 µg/mL. The treatment failure rate did not significantly differ between the two groups (MIC 1 vs. MIC 2: 27.0% vs. 31.0%; p = 0.779). As a result of multivariate analysis, AUC/MIC0-24 h ≤230 was extracted as risk factor for treatment failure, suggesting the importance of a sufficient initial loading dose and early blood concentration monitoring to increase AUC/MIC0-24 h for successful treatment.

Addressing the surge of infections by multidrug-resistant Enterobacterales in hematopoietic cell transplantation

Patients undergoing hematopoietic cell transplantation (HCT) have an increased risk of developing severe infections. In recent years, bloodstream infections caused by Gram-negative bacteria have been increasingly reported among HCT recipients, and many of these infections are caused by bacterial strains of the Enterobacterales order. Among these pathogens, particularly concerning are the multidrug-resistant Enterobacterales (MDRE), such as Extended Spectrum β-lactamase-producing Enterobacterales and Carbapenem-resistant Enterobacterales, since infections caused by these pathogens are difficult to treat due to the limited antimicrobial options and are associated with worse transplant outcomes. We summarized the evidence from studies published in PubMed and Scopus on the burden of MDRE infections in HCT recipients, and strategies for the management and prevention of these infections, including strict adherence to recommended infection control practices and multidisciplinary antimicrobial stewardship, the use of probiotics, and fecal microbiota transplantation, are also discussed.

Evolving resistance landscape in gram-negative pathogens: An update on β-lactam and β-lactam-inhibitor treatment combinations for carbapenem-resistant organisms

Antibiotic resistance has become a global threat as it is continuously growing due to the evolution of β-lactamases diminishing the activity of classic β-lactam (BL) antibiotics. Recent antibiotic discovery and development efforts have led to the availability of β-lactamase inhibitors (BLIs) with activity against extended-spectrum β-lactamases as well as Klebsiella pneumoniae carbapenemase (KPC)-producing carbapenem-resistant organisms (CRO). Nevertheless, there is still a lack of drugs that target metallo-β-lactamases (MBL), which hydrolyze carbapenems efficiently, and oxacillinases (OXA) often present in carbapenem-resistant Acinetobacter baumannii. This review aims to provide a snapshot of microbiology, pharmacology, and clinical data for currently available BL/BLI treatment options as well as agents in late stage development for CRO harboring various β-lactamases including MBL and OXA-enzymes.

Clinical Outcomes of Patients with AmpC-Beta-Lactamase-Producing Enterobacterales Bacteremia Treated with Carbapenems versus Non-Carbapenem Regimens: A Single-Center Study

INTRODUCTION

Bloodstream infections caused by AmpC-producing Enterobacterales pose treatment challenges due to the risk of AmpC overproduction and treatment failure. Current guidelines recommend carbapenems or cefepime as optimal therapy. We aimed to evaluate empiric and definitive non-carbapenem regimens for these infections.

METHODS

In a retrospective study from June 2014 to March 2023, adult bacteremic patients with Enterobacter cloacae complex strains and Morganella morganii were evaluated. Demographic, clinical and lab data and outcomes were assessed.

RESULTS

The cohort comprised 120 bacteremic patients, 17 receiving empiric carbapenem and 103 non-carbapenem regimens. Both groups had similar Charlson and Norton scores and previous antimicrobial exposure. The most common sources of bacteremia were urinary, abdominal and central-line-associated sources. Empiric non-carbapenem regimens (primarily piperacillin-tazobactam and cephalosporins) were not associated with recurrent bacteremia or 30-day mortality. Definitive regimens included mainly carbapenems (n = 41) and ciprofloxacin (n = 46). Beta-lactams were administered to 25 patients. Recurrent bacteremia and 30-day mortality rates were similar among treatment groups. Ciprofloxacin showed comparable outcomes to carbapenems, however, severity of illness among these patients was lower.

CONCLUSIONS

Empiric and definitive non-carbapenem regimens for bacteremia with AmpC-producing organisms were not associated with treatment failure or increased 30-day mortality. Ciprofloxacin appears promising for selected, stable patients, potentially enabling early discharge.

Mutation Rate of AmpC β-Lactamase-Producing Enterobacterales and Treatment in Clinical Practice: A Word of Caution

In a retrospective multicenter study of 575 patients with bloodstream infections or pneumonia due to wild-type AmpC β-lactamase-producing Enterobacterales, species with low in vitro mutation rates for AmpC derepression were associated with fewer treatment failures due to AmpC overproduction (adjusted hazard ratio, 0.5 [95% CI, .2-.9]). However, compared to cefepime/carbapenems, using third-generation cephalosporins as definitive therapy remained associated with this adverse outcome (15% vs 1%).

Burden and Management of Multi-Drug Resistant Organism Infections in Solid Organ Transplant Recipients Across the World: A Narrative Review

Solid organ transplant (SOT) recipients are particularly susceptible to infections caused by multidrug-resistant organisms (MDRO) and are often the first to be affected by an emerging resistant pathogen. Unfortunately, their prevalence and impact on morbidity and mortality according to the type of graft is not systematically reported from high-as well as from low and middle-income countries (HIC and LMIC). Thus, epidemiology on MDRO in SOT recipients could be subjected to reporting bias. In addition, screening practices and diagnostic resources may vary between countries, as well as the availability of new drugs. In this review, we aimed to depict the burden of main Gram-negative MDRO in SOT patients across HIC and LMIC and to provide an overview of current diagnostic and therapeutic resources.

Management of intra-abdominal infections: recommendations by the Italian council for the optimization of antimicrobial use

Intra-abdominal infections (IAIs) are common surgical emergencies and are an important cause of morbidity and mortality in hospital settings, particularly if poorly managed. The cornerstones of effective IAIs management include early diagnosis, adequate source control, appropriate antimicrobial therapy, and early physiologic stabilization using intravenous fluids and vasopressor agents in critically ill patients. Adequate empiric antimicrobial therapy in patients with IAIs is of paramount importance because inappropriate antimicrobial therapy is associated with poor outcomes. Optimizing antimicrobial prescriptions improves treatment effectiveness, increases patients' safety, and minimizes the risk of opportunistic infections (such as Clostridioides difficile) and antimicrobial resistance selection. The growing emergence of multi-drug resistant organisms has caused an impending crisis with alarming implications, especially regarding Gram-negative bacteria. The Multidisciplinary and Intersociety Italian Council for the Optimization of Antimicrobial Use promoted a consensus conference on the antimicrobial management of IAIs, including emergency medicine specialists, radiologists, surgeons, intensivists, infectious disease specialists, clinical pharmacologists, hospital pharmacists, microbiologists and public health specialists. Relevant clinical questions were constructed by the Organizational Committee in order to investigate the topic. The expert panel produced recommendation statements based on the best scientific evidence from PubMed and EMBASE Library and experts' opinions. The statements were planned and graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) hierarchy of evidence. On November 10, 2023, the experts met in Mestre (Italy) to debate the statements. After the approval of the statements, the expert panel met via email and virtual meetings to prepare and revise the definitive document. This document represents the executive summary of the consensus conference and comprises three sections. The first section focuses on the general principles of diagnosis and treatment of IAIs. The second section provides twenty-three evidence-based recommendations for the antimicrobial therapy of IAIs. The third section presents eight clinical diagnostic-therapeutic pathways for the most common IAIs. The document has been endorsed by the Italian Society of Surgery.

The EC-COMPASS: Long-term, multi-centre surveillance of Enterobacter cloacae complex - a clinical perspective

BACKGROUND

Enterobacter cloacae complex (ECCO) comprises closely related Enterobacterales, causing a variety of infections ranging from mild urinary tract infections to severe bloodstream infections. ECCO has emerged as a significant cause of healthcare-associated infections, particularly in neonatal and adult intensive care.

AIM

The Enterobacter Cloacae COMplex PASsive Surveillance (EC-COMPASS) aims to provide a detailed multi-centre overview of ECCO epidemiology and resistance patterns detected in routine microbiological diagnostics in four German tertiary-care hospitals.

METHODS

In a sentinel cluster of four German tertiary-care hospitals, all culture-positive ECCO results between 1st January 2020 and 31st December 2022, were analysed based on Hybase® laboratory data.

FINDINGS

Analysis of 31,193 ECCO datasets from 14,311 patients revealed a higher incidence in male patients (P<0.05), although no significant differences were observed in ECCO infection phenotypes. The most common sources of ECCO were swabs (42.7%), urine (17.5%), respiratory secretions (16.1%), blood cultures (8.9%) and tissue samples (5.6%). The annual bacteraemia rate remained steady at approximately 33 cases per hospital. Invasive ECCO infections were predominantly found in oncology and intensive care units. Incidences of nosocomial outbreaks were infrequent and limited in scope. Notably, resistance to carbapenems was consistently low.

CONCLUSION

EC-COMPASS offers a profound clinical perspective on ECCO infections in German tertiary-healthcare settings, highlighting elderly men in oncology and intensive care units as especially vulnerable to ECCO infections. Early detection strategies targeting at-risk patients could improve ECCO infection management.

Enterobacterales carrying chromosomal AmpC β-lactamases in Europe (EuESCPM): Epidemiology and antimicrobial resistance burden from a cohort of 27 hospitals, 2020-2022

INTRODUCTION

The ESCPM group (Enterobacter species including Klebsiella aerogenes - formerly Enterobacter aerogenes, Serratia species, Citrobacter freundii complex, Providencia species and Morganella morganii) has not yet been incorporated into systematic surveillance programs.

METHODS

We conducted a multicentre retrospective observational study analysing all ESCPM strains isolated from blood cultures in 27 European hospitals over a 3-year period (2020-2022). Diagnostic approach, epidemiology, and antimicrobial susceptibility were investigated.

RESULTS

Our study comprised 6,774 ESCPM isolates. MALDI-TOF coupled to mass spectrometry was the predominant technique for bacterial identification. Susceptibility to new β-lactam/β-lactamase inhibitor combinations and confirmation of AmpC overproduction were routinely tested in 33.3% and 29.6% of the centres, respectively. The most prevalent species were E. cloacae complex (44.8%) and S. marcescens (22.7%). Overall, third-generation cephalosporins (3GC), combined third- and fourth-generation cephalosporins (3GC + 4GC) and carbapenems resistance phenotypes were observed in 15.7%, 4.6%, and 9.5% of the isolates, respectively. AmpC overproduction was the most prevalent resistance mechanism detected (15.8%). Among carbapenemase-producers, carbapenemase type was provided in 44.4% of the isolates, VIM- (22.9%) and OXA-48-enzyme (16%) being the most frequently detected. E. cloacae complex, K. aerogenes and Providencia species exhibited the most notable cumulative antimicrobial resistance profiles, with the former displaying 3GC, combined 3GC + 4GC and carbapenems resistance phenotypes in 15.2%, 7.4%, and 12.8% of the isolates, respectively. K. aerogenes showed the highest rate of both 3GC resistant phenotype (29.8%) and AmpC overproduction (32.1%), while Providencia species those of both carbapenems resistance phenotype (42.7%) and carbapenemase production (29.4%). ESCPM isolates exhibiting both 3GC and combined 3GC + 4GC resistance phenotypes displayed high susceptibility to ceftazidime/avibactam (98.2% and 95.7%, respectively) and colistin (90.3% and 90.7%, respectively). Colistin emerged as the most active drug against ESCPM species (except those intrinsically resistant) displaying both carbapenems resistance phenotype (85.8%) and carbapenemase production (97.8%).

CONCLUSIONS

This study presented a current analysis of ESCPM species epidemiology in Europe, providing insights to inform current antibiotic treatments and guide strategies for antimicrobial stewardship and diagnostics.

Molecular epidemiological characteristics of carbapenem-resistant Pseudomonas aeruginosa clinical isolates in southeast Shanxi, China

OBJECTIVES

Infection by carbapenem-resistant Pseudomonas aeruginosa (CRPA) is a serious clinical problem worldwide. However, the molecular epidemiology of the clinical isolates varies depending on the region. This study was conducted to analyse the resistance phenotype and clarify the genetic and epidemiological properties of CRPA clinical isolates from southeast Shanxi, China.

METHODS

Fifty-seven isolates of CRPA were collected from a hospital in this region. These isolates were reidentified by MALDI-TOF and subjected to whole-genome sequencing by next-generation sequencing. Phylogenetic trees were constructed based on single nucleotide polymorphisms (SNPs), after which multilocus sequence typing (MLST) was performed and antimicrobial resistance genes were identified.

RESULTS

All the 57 CRPA isolates carried at least one kind of gene encoding carbapenemase, such as blaIMP-1, blaIMP-10, blaOXA-10, blaOXA-395, blaOXA-396, blaOXA-485, blaOXA-486, blaOXA-488, blaOXA-494, and blaOXA-50. The isolates harboured AIM-1, CMY-51, mecD, and NmcR genes and carried one kind of Pseudomonas-derived cephalosporinase (PDC) β-lactamase-encoding gene, such as blaPCD-1 to blaPCD-3, blaPCD-5, or blaPCD-7 to blaPCD-10. Two isolates were found to harbour the aminoglycoside-modifying enzyme genes aadA1 and aadA7; however, no isolates were found to harbour genes encoding 16S rRNA methylase or quinolone resistance-related genes. These CRPA isolates belonged to various sequence types (STs), two of which, namely, ST235 and ST277, were high-risk types.

CONCLUSIONS

Our findings indicate that CRPA isolates carrying resistance genes with unique regional characteristics are spreading in this region, with a high diversity of STs, especially in high-risk clones. These findings highlight the necessity for further measures to prevent CRPA spread in Shanxi.

Significant Publications on Infectious Diseases Pharmacotherapy in 2021

Purpose: To summarize the most noteworthy infectious diseases (ID) pharmacotherapy articles published in peer-reviewed literature in 2021. Summary: Members of the Houston Infectious Diseases Network (HIDN) nominated articles that were deemed to have significant contributions to ID pharmacotherapy in 2021. These nominations included articles pertaining to both general ID, including coronavirus disease 2019 (COVID-19), and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) pharmacotherapy. A total of 35 articles were nominated by HIDN: 30 articles pertaining to general ID pharmacotherapy and 5 articles with HIV/AIDS focus. To select the most influential articles of 2021, a survey was created and distributed to members of the Society of Infectious Diseases Pharmacists (SIDP). Of the 239 SIDP members who responded to the survey, there were 192 recorded votes for the top 10 general ID pharmacotherapy articles and 47 recorded votes for the top HIV/AIDS article, respectively. The top publications are summarized. Conclusion: Antimicrobial stewardship and the optimal management of infectious disease states continues to be a priority in the midst of the ongoing coronavirus disease 2019 (COVID-19) global pandemic. In light of the sheer volume of ID-related articles published in the past year, this review aims to aid clinicians in remaining up-to-date on key practice-changing ID pharmacotherapy publications from 2021.

Optimized Treatment of Nosocomial Peritonitis

This comprehensive review aims to provide a practical guide for intensivists, focusing on enhancing patient care associated with nosocomial peritonitis (NP). It explores the epidemiology, diagnosis, and management of NP, a significant contributor to the mortality of surgical patients worldwide. NP is, per definition, a hospital-acquired condition and a consequence of gastrointestinal surgery or a complication of other diseases. NP, one of the most prevalent causes of sepsis in surgical Intensive Care Units (ICUs), is often associated with multi-drug resistant (MDR) bacteria and high mortality rates. Early clinical suspicion and the utilization of various diagnostic tools like biomarkers and imaging are of great importance. Microbiology is often complex, with antimicrobial resistance escalating in many parts of the world. Fungal peritonitis and its risk factors, diagnostic hurdles, and effective management approaches are particularly relevant in patients with NP. Contemporary antimicrobial strategies for treating NP are discussed, including drug resistance challenges and empirical antibiotic regimens. The importance of source control in intra-abdominal infection management, including surgical and non-surgical interventions, is also emphasized. A deeper exploration into the role of open abdomen treatment as a potential option for selected patients is proposed, indicating an area for further investigation. This review underscores the need for more research to advance the best treatment strategies for NP.

Cefepime Versus Piperacillin-Tazobactam for the Treatment of Intra-Abdominal Infections Secondary to Potential AmpC Beta-Lactamase-Producing Organisms

Background: Recent studies have established cefepime as an effective treatment option for AmpC beta-lactamase (AmpC) Enterobacterales; however, the efficacy of beta-lactam/beta-lactamase inhibitors is unclear. Objective: The objective of this study was to determine if piperacillintazobactamis an appropriate alternative to cefepime for the treatment of intra-abdominal infections (IAIs) secondary to AmpC-producing organisms. Methods: This multicenter, retrospective cohort study was conducted in hospitalized adults with an IAI caused by an AmpC-producing organism and received either cefepime or piperacillin-tazobactam for definitive treatment after a source control procedure. The primary outcome was a composite of surgical site infections, recurrent IAIs, or in-hospital mortality. Secondary outcomes included the individual components of the composite outcome, hospital length of stay (LOS), microbiologic failure, study antibiotic duration, time to clinical resolution, and incidence of Clostridioides difficile infection (CDI). Results: This study included 119 patients. There was no difference in the primary outcome between the cefepime and piperacillin-tazobactam groups (35% vs 27%, P = 0.14). Microbiological failure was the only secondary outcome with an observed difference between groups (17% vs 0%, P = 0.01): hospital LOS (15 vs 13 days, P = 0.09), days of therapy (7 vs 7 days, P = 0.87), time to clinical resolution (7 vs 4 days, P = 0.30), and CDI (1% vs 2%, P = 0.58) were all similar.

Significant clinical differences but not outcomes between Klebsiella aerogenes and Enterobacter cloacae bloodstream infections: a comparative cohort study

PURPOSE

Although Klebsiella aerogenes (formerly Enterobacter aerogenes) and Enterobacter cloacae share many phenotypic characteristics, controversy exists as to whether they cause clinically distinguishable infections. The objective of this study was to determine the comparative incidence, determinants, and outcomes of K. aerogenes and E. cloacae bloodstream infections (BSI).

METHODS

Population-based surveillance was conducted among residents aged ≥ 15 years of Queensland, Australia during 2000-2019.

RESULTS

Overall 695 and 2879 incident K. aerogenes and E. cloacae BSIs were identified for incidence rates of 1.1 and 4.4 per 100,000 population, respectively. There was a marked increase in incidence associated with older age and with males with both species. Patients with K. aerogenes BSIs were older, were more likely male, to have community-associated disease, and to have a genitourinary source of infection. In contrast, E. cloacae were more likely to have co-morbid diagnoses of liver disease and malignancy and be associated with antimicrobial resistance. Enterobacter cloacae were significantly more likely to have repeat episodes of BSI as compared to K. aerogenes. However, no differences in length of stay or all cause 30-day case-fatality were observed.

CONCLUSION

Although significant demographic and clinical differences exist between K. aerogenes and E. cloacae BSI, they share similar outcomes.

Clinical Outcomes of Third-Generation Cephalosporin Definitive Therapy for Bloodstream Infections Due to Enterobacterales with Potential AmpC Induction: A Single-Center Retrospective Study

The recommended therapy for severe infections caused by AmpC-inducible Enterobacterales (AmpC-E) typically involves cefepime or carbapenems. In an era of emerging resistance to these antimicrobials, we aim to assess the impact of third-generation cephalosporins (3GCs) vs. alternative antibiotics on clinical outcomes in bloodstream infections (BSIs) due to AmpC-E. We retrospectively included hospitalized adult patients with BSIs caused by 3GC-susceptible AmpC-E between 2012 and 2022, comparing the outcomes of 3GC and non-3GC definitive therapies. The primary outcome was overall treatment failure (OTF), encompassing 90-day all-cause mortality, 90-day reinfection, and 90-day readmission. Secondary outcomes comprised components of the OTF, in-hospital all-cause mortality, and length-of-stay. Within a total cohort of 353 patients, OTF occurred in 46.5% and 41.5% in the 3GC- and non-3GC-therapy groups, respectively (p = 0.36). The 3GC-therapy group exhibited a longer length-of-stay (38 vs. 21 days, p = 0.0003) and higher in-hospital mortality (23.3% vs. 13.4%, p = 0.019). However, the 90-day mortality, 90-day reinfection, and 90-day readmission were comparable between the therapy groups. Subgroup analyses involving high-risk AmpC-E and 3GC vs. standard-of-care yielded similar conclusions. Overall, our findings suggest that 3GC definitive therapy may not result in poorer clinical outcomes for the treatment of BSIs caused by AmpC-E.

Enterobacter cloacae infection characteristics and outcomes in battlefield trauma patients

Enterobacter cloacae is a Gram-negative rod with multidrug-resistant potential due to chromosomally-induced AmpC β-lactamase. We evaluated characteristics, antibiotic utilization, and outcomes associated with battlefield-related E. cloacae infections (2009-2014). Single initial and serial E. cloacae isolates (≥24 hours from initial isolate from any site) associated with a clinical infection were examined. Susceptibility profiles of initial isolates in the serial isolation group were contrasted against last isolate recovered. Characteristics of 112 patients with E. cloacae infections (63 [56%] with single initial isolation; 49 [44%] with serial isolation) were compared to 509 patients with bacterial infections not attributed to E. cloacae. E. cloacae patients sustained more blast trauma (78%) compared to non-E. cloacae infections patients (75%; p<0.001); however, injury severity scores were comparable (median of 34.5 and 33, respectively; p = 0.334). Patients with E. cloacae infections had greater shock indices (median 1.07 vs 0.92; p = 0.005) and required more initial blood products (15 vs. 14 units; p = 0.032) compared to patients with non-E. cloacae infections. Although E. cloacae patients had less intensive care unit admissions (80% vs. 90% with non-E. cloacae infection patients; p = 0.007), they did have more operating room visits (5 vs. 4; p = 0.001), longer duration of antibiotic therapy (43.5 vs. 34 days; p<0.001), and lengthier hospitalizations (57 vs. 44 days; p<0.001). Patients with serial E. cloacae had isolation of infecting isolates sooner than patients with single initial E. cloacae (median of 5 vs. 8 days post-injury; p = 0.046); however, outcomes were not significantly different between the groups. Statistically significant resistance to individual antibiotics did not develop between initial and last isolates in the serial isolation group. Despite current combat care and surgical prophylaxis guidelines recommending upfront provision of AmpC-inducing antibiotics, clinical outcomes did not differ nor did significant antibiotic resistance develop in patients who experienced serial isolation of E. cloacae versus single initial isolation.

Carbapenem alternatives for treatment of bloodstream infections due to AmpC producing enterobacterales

INTRODUCTION

Carbapenems (CR) have traditionally been the first line treatment for bacteremia caused by AmpC-producing Enterobacterales. However, CR have a high ecological impact, and carbapenem-resistant strains continue rising. Thus, other treatment alternatives like Piperacillin-Tazobactam (P-T) or Cefepime (CEF) and oral sequential therapy (OST) are being evaluated.

METHODS

We conducted a retrospective, single-centre observational study. All adult patients with AmpC-producing Enterobacterales bacteremia were included. The primary endpoint was clinical success defined as a composite of clinical cure, 14-day survival, and no adverse events. We evaluated the evolution of patients in whom OST was performed.

RESULTS

Seventy-seven patients were included, 22 patients in the CR group and 55 in the P-T/CEF group (37 patients received CEF and 18 P-T). The mean age of the patients was higher in the P-T/CEF group (71 years in CR group vs. 76 years in P-T/CEF group, p = 0.053). In the multivariate analysis, age ≥ 70 years (OR 0.08, 95% CI [0.007-0.966], p = 0.047) and a Charlson index ≥ 3 (OR 0.16, 95% CI [0.026-0.984], p = 0.048), were associated with a lower clinical success. Treatment with P-T/CEF was associated with higher clinical success (OR 7.75, 95% CI [1.273-47.223], p = 0.026). OST was performed in 47% of patients. This was related with a shorter in-hospital stay (OST 14 days [7-22] vs. non-OST 18 days [13-38], p = 0.005) without difference in recurrence (OST 3% vs. non-OST 5%, p = 0.999).

CONCLUSIONS

Targeted treatment with P-T/CEF and OST could be safe and effective treatments for patients with AmpC-producing Enterobacterales bacteremia.

Optimization of Antimicrobial Stewardship Programs Using Therapeutic Drug Monitoring and Pharmacokinetics-Pharmacodynamics Protocols: A Cost-Benefit Review

PURPOSE

Antimicrobial stewardship programs are important for reducing antimicrobial resistance because they can readjust antibiotic prescriptions to local guidelines, switch intravenous to oral administration, and reduce hospitalization times. Pharmacokinetics-pharmacodynamics (PK-PD) empirically based prescriptions and therapeutic drug monitoring (TDM) programs are essential for antimicrobial stewardship, but there is a need to fit protocols according to cost benefits. The cost benefits can be demonstrated by reducing toxicity and hospital stay, decreasing the amount of drug used per day, and preventing relapses in infection. Our aim was to review the data available on whether PK-PD empirically based prescriptions and TDM could improve the cost benefits of an antimicrobial stewardship program to decrease global hospital expenditures.

METHODS

A narrative review based on PubMed search with the relevant studies of vancomycin, aminoglycosides, beta-lactams, and voriconazole.

RESULTS

TDM protocols demonstrated important cost benefit for patients treated with vancomycin, aminoglycosides, and voriconazole mainly due to reduce toxicities and decreasing the hospital length of stay. In addition, PK-PD strategies that used infusion modifications to meropenem, piperacillin-tazobactam, ceftazidime, and cefepime, such as extended or continuous infusion, demonstrated important cost benefits, mainly due to reducing daily drug needs and lengths of hospital stays.

CONCLUSIONS

TDM protocols and PK-PD empirically based prescriptions improve the cost-benefits and decrease the global hospital expenditures.

Risk evaluation of carbapenem-induced liver injury based on machine learning analysis

INTRODUCTION

Information regarding carbapenem-induced liver injury is limited, and the rate of liver injury caused by meropenem (MEPM) and doripenem (DRPM) remains unknown. Decision tree (DT) analysis, a machine learning method, has a flowchart-like model where users can easily predict the risk of liver injury. Thus, we aimed to compare the rate of liver injury between MEPM and DRPM and construct a flowchart that can be used to predict carbapenem-induced liver injury.

METHODS

We investigated patients treated with MEPM (n = 310) or DRPM (n = 320) and confirmed liver injury as the primary outcome. We used a chi-square automatic interaction detection algorithm to construct DT models. The dependent variable was set as liver injury from a carbapenem (MEPM or DRPM), and factors including alanine aminotransferase (ALT), albumin-bilirubin (ALBI) score, and concomitant use of acetaminophen were used as explanatory variables.

RESULTS

The rates of liver injury were 22.9% (71/310) and 17.5% (56/320) in the MEPM and DRPM groups, respectively; no significant differences in the rate were observed (95% confidence interval: 0.710-1.017). Although the DT model of MEPM could not be constructed, DT analysis showed that the incidence of introducing DRPM in patients with ALT >22 IU/L and ALBI scores > -1.87 might be high-risk.

CONCLUSIONS

The risk of developing liver injury did not differ significantly between the MEPM and DRPM groups. Since ALT and ALBI score are evaluated in clinical settings, this DT model is convenient and potentially useful for medical staff in assessing liver injury before DRPM administration.

The threat of multidrug-resistant/extensively drug-resistant Gram-negative respiratory infections: another pandemic

Antibiotic resistance is recognised as a global threat to human health by national healthcare agencies, governments and medical societies, as well as the World Health Organization. Increasing resistance to available antimicrobial agents is of concern for bacterial, fungal, viral and parasitic pathogens. One of the greatest concerns is the continuing escalation of antimicrobial resistance among Gram-negative bacteria resulting in the endemic presence of multidrug-resistant (MDR) and extremely drug-resistant (XDR) pathogens. This concern is heightened by the identification of such MDR/XDR Gram-negative bacteria in water and food sources, as colonisers of the intestine and other locations in both hospitalised patients and individuals in the community, and as agents of all types of infections. Pneumonia and other types of respiratory infections are among the most common infections caused by MDR/XDR Gram-negative bacteria and are associated with high rates of mortality. Future concerns are already heightened due to emergence of resistance to all existing antimicrobial agents developed in the past decade to treat MDR/XDR Gram-negative bacteria and a scarcity of novel agents in the developmental pipeline. This clinical scenario increases the likelihood of a future pandemic caused by MDR/XDR Gram-negative bacteria.

Controversies over the management of infections caused by Amp-C- and ESBL-producing Enterobacterales : what questions remain for future studies?

PURPOSE OF REVIEW

The continuous rise in infections caused by third-generation cephalosporin-resistant Enterobacterales (e.g. extended-spectrum beta-lactamase- or AmpC-producing Enterobacterales ) is a major health concern. Carbapenems are regarded as the antibiotics of choice for the treatment of these infections. However, their indiscriminant use is not without consequences, and has contributed to the emergence of carbapenem-resistant Enterobacterales .In this review, we discuss the available evidence supporting the use of other betalactams, nonbetalactams and the new betalactams/beta-lactamase inhibitors (BLA/BLI) to treat these infections. We also analyze unresolved issues in this field.

RECENT FINDINGS

Piperacillin tazobactam (PTZ) was classically recommended as a carbapenem-sparing agent. However, data have emerged against its use and it is now a controversial recommendation. IDSA, European and British guidelines reject the empirical use of PTZ for these pathogens, reserving its use for rare clinical situations.Other issues that continue to generate debate are the use of extended infusion (3 h) PTZ, the use of older antibiotics, a shortened course of carbapenems and reserving the new BLA/BLI for these infections.

SUMMARY

New treatment strategies should be based on clinical evidence, local epidemiology and the microbiological activity of these drugs.

L-Form Switching in Escherichia coli as a Common β-Lactam Resistance Mechanism

Cell wall deficient bacterial L-forms are induced by exposure to cell wall-targeting antibiotics and immune effectors such as lysozyme. L-forms of different bacteria (including Escherichia coli) have been reported in human infections, but whether this is a normal adaptive strategy or simply an artifact of antibiotic treatment in certain bacterial species remains unclear. Here we show that members of a representative, diverse set of pathogenic E. coli readily proliferate as L-forms in supratherapeutic concentrations of the broad-spectrum antibiotic meropenem. We report that they are completely resistant to antibiotics targeting any penicillin-binding proteins in this state, including PBP1A/1B, PBP2, PBP3, PBP4, and PBP5/6. Importantly, we observed that reversion to the cell-walled state occurs efficiently, less than 20 h after antibiotic cessation, with few or no changes in DNA sequence. We defined for the first time a logarithmic L-form growth phase with a doubling time of 80 to 190 min, followed by a stationary phase in late cultures. We further demonstrated that L-forms are metabolically active and remain normally susceptible to antibiotics that affect DNA torsion and ribosomal function. Our findings provide insights into the biology of L-forms and help us understand the risk of β-lactam failure in persistent infections in which L-forms may be common. IMPORTANCE Bacterial L-forms require specialized culture techniques and are neither widely reported nor well understood in human infections. To date, most of the studies have been conducted on Gram-positive and stable L-form bacteria, which usually require mutagenesis or long-term passages for their generation. Here, using an adapted osmoprotective growth media, we provide evidence that pathogenic E. coli can efficiently switch to L-forms and back to a cell-walled state, proliferating aerobically in supratherapeutic concentrations of antibiotics targeting cell walls with few or no changes in their DNA sequences. Our work demonstrates that L-form switching is an effective adaptive strategy in stressful environments and can be expected to limit the efficacy of β-lactam for many important infections.

Pragmatic Comparison of Piperacillin/Tazobactam versus Carbapenems in Treating Patients with Nosocomial Pneumonia Caused by Extended-Spectrum β-Lactamase-Producing Klebsiella pneumoniae

The effectiveness of piperacillin/tazobactam for managing nosocomial pneumonia caused by extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae is unknown. To answer this question, we conducted a retrospective cohort study in two tertiary teaching hospitals of patients admitted between January 2018 and July 2021 with a diagnosis of nosocomial pneumonia caused by ESBL-producing K. pneumoniae receiving either piperacillin/tazobactam or carbapenems within 24 h from the onset of pneumonia for at least 72 h. Clinical outcomes, including 28-day mortality and 14-day clinical and microbiological cure, were analyzed. Of the 136 total patients, 64 received piperacillin/tazobactam and 72 received carbapenems. The overall 28-day mortality was 19.1% (26/136). In the inverse probability of treatment weighted cohort, piperacillin/tazobactam therapy was not associated with worse clinical outcomes, as the 28-day mortality (OR, 0.82, 95% CI, 0.23–2.87, p = 0.748), clinical cure (OR, 0.94, 95% CI, 0.38–2.35, p = 0.894), and microbiological cure (OR, 1.10, 95% CI, 0.53–2.30, p = 0.798) were comparable to those of carbapenems. Subgroup analyses also did not demonstrate any statistical differences. In conclusion, piperacillin/tazobactam could be an effective alternative to carbapenems for treating nosocomial pneumonia due to ESBL-producing K. pneumoniae when the MICs are ≤8 mg/L.

Research Activities in General Medicine: A Scoping Survey by the Internal Medicine Society of Australia and New Zealand (IMSANZ)

Background

In developing an effective framework for a collaborative research network (RN) that supports members involved in research, the Internal Medicine Society of Australia and New Zealand (IMSANZ) required a better understanding of the current level of research activity and engagement by general physicians, and factors influencing such engagement.

Aims

To explore the current research landscape amongst general physicians in Australia and Aotearoa New Zealand.

Methods

A questionnaire exploring research participation, scope, research enablers and barriers was disseminated to IMSANZ members over a 3‐month period. Core functions of IMSANZ‐RN, research priorities, potential solutions to perceived barriers and required level of support were also evaluated.

Results

A total of 82 members, mostly senior medical staff (74.4%), responded to the survey (11.8% response rate). More than 70% were involved in impactful research across multiple disciplines, encompassing a wide range of research themes and topics. However, there is limited support and resources available to conduct research, with most projects being self‐instigated and self‐funded. There is overwhelming support to increasing the profile of research in general medicine through the establishment of IMSANZ‐RN, whose principal purposes, as identified by respondents, are to foster collaboration, promote research, provide research education and training, and share information among general physicians. Quality improvement studies (56.1%) and clinical trials (41.5%) were also identified as priority research types.

Conclusions

This study has profiled the constraints faced by general physicians in conducting high‐quality collaborative research and provides insights into what is needed to support greater research engagement, through development of a discipline‐specific clinical RN.

Morganella morganii, an Emerging Cause of Bloodstream Infections

Although recent reports of extensively antibiotic-resistant strains have highlighted the importance of Morganella morganii as an emerging pathogen, the epidemiology of serious infections due to this organism is not well defined. The objective of this study was to determine the incidence, determinants, and outcomes of Morganella morganii bloodstream infections (BSIs). Retrospective, population-based surveillance for Morganella morganii BSIs was conducted in Queensland, Australia, in 2000 to 2019; 709 cases were identified, for an annual incidence of 9.2 cases per million population. Most cases were of community onset, with 280 (39.5%) community-associated cases and 226 (31.9%) health care-associated cases. Morganella morganii BSIs were rare in children and young adults, and the incidence increased markedly with advancing age. The most common foci of infection were skin and soft tissue (131 cases [18.5%]), genitourinary (97 cases [13.7%]), and intraabdominal (90 cases [12.7%]). Most patients (580 cases [81.8%]) had at least one comorbid medical illness, with diabetes mellitus (250 cases [35.3%]), renal disease (208 cases [29.3%]), and congestive heart failure (167 cases [23.6%]) being most prevalent. Resistance to one or more of quinolones, co-trimoxazole, aminoglycosides, or carbapenems was observed in 67 cases (9.5%), and this did not change significantly over the study. The 30-day all-cause case fatality rate was 21.2%, and increasing age, nonfocal infection, heart failure, dementia, and cancer were independently associated with increased risk of death. Morganella morganii BSIs are increasing in our population, and elderly male subjects and individuals with comorbidities are at highest risk. Although antibiotic resistance is not a major contributor to the current burden in Queensland, ongoing surveillance is warranted. IMPORTANCE Recent reports of extensively antibiotic-resistant strains have highlighted the importance of Morganella morganii as an emerging pathogen. Despite its present and evolving importance as an agent of human disease, there is a limited body of literature detailing the epidemiology of serious infections due to Morganella morganii. Therefore, the objectives of this study were to examine the incidence and determinants of Morganella morganii BSIs and to examine risk factors for death in a large Australian population in 2000 to 2019.

Occurrence of Serratia marcescens Carrying blaIMP-26 and mcr-9 in Southern China: New Insights in the Evolution of Megaplasmid IMP-26

The spread of multidrug-resistant enterobacteria strains has posed a significant concern in public health, especially when the strain harbors metallo-beta-lactamase (MBL)-encoding and mobilized colistin resistance (mcr) genes as such genetic components potentially mediate multidrug resistance. Here we report an IncHI2/2A plasmid carrying bla_IMP-26 and mcr-9 in multidrug-resistant Serratia marcescens human isolates YL4. Antimicrobial susceptibility testing was performed by the broth microdilution method. According to the results, S. marcescens YL4 was resistant to several antimicrobials, including β-lactams, fluorquinolones, sulfanilamide, glycylcycline, and aminoglycosides, except for amikacin. To investigate the plasmid further, we conducted whole-genome sequencing and sequence analysis. As shown, S. marcescens YL4 possessed a circular chromosome with 5,171,477 bp length and two plasmids, pYL4.1 (321,744 bp) and pYL4.2 (46,771 bp). Importantly, sharing high similarity with plasmids pZHZJ1 and pIMP-26, pYL4.1 has an IncHI2/2A backbone holding a variable region containing bla_IMP-26, mcr-9, and two copies of bla_TEM-1B. After comprehensively comparing relevant plasmids, we proposed an evolutionary pathway originating from ancestor pZHZJ1. Then, via an acquisition of the mcr-9 element and a few recombination events, this plasmid eventually evolved into pYL4.1 and pIMP-26 through two different pathways. In addition, the phage-like plasmid pYL4.2 also carried a bla_TEM-1B gene. Remarkably, this study first identified a multidrug-resistant S. marcescens strain co-harboring bla_IMP-26 and mcr-9 on a megaplasmid pYL4.1 and also included a proposed evolutionary pathway of epidemic megaplasmids carrying bla_IMP-26.

Microbiological and Clinical Characteristics of Bloodstream Infections in General Intensive Care Unit: A Retrospective Study

Background

Bloodstream infections (BSI) are one of the common causes of morbidity and mortality in hospitals; however, the pathogenic spectrum and bacterial antibiotic resistance vary across the world. Therefore, identifying the pathogenic spectrum and changes in bacterial antibiotic resistance is critical in controlling BSI and preventing the irrational use of antibiotics. This study evaluated the microbiological and clinical data of BSI patients in the intensive care unit (ICU) of Tianjin Medical University General Hospital in Tianjin, China, to guide the selection of empirical antibiotic therapy.

Methods

This study retrospectively analyzed the distribution and antibiotic resistance of pathogens based on the clinical data of BSI patients presented in the ICU of a tertiary teaching hospital from 2018 to 2020. Test performance for the prediction of pathogen species was assessed by receiver operating characteristic (ROC) analysis.

Results

The analysis of the data of 382 BSI cases (10.40 cases per thousand patient day) revealed the most frequently isolated microorganisms to be Klebsiella pneumonia (11.52%), followed by Escherichia coli (9.95%), Staphylococcus epidermidis (9.95%), Candida parapsilosis (8.12%), and Enterococcus faecium (8.12%). Out of the isolated E. coli and K. pneumonia strains, 52.63, and 36.36%, respectively, were extended-spectrum β-lactamase (ESBL) positive. The antibiotic-resistance rate of the ESBL-positive strains was 30.56% for piperacillin/tazobactam, 5.56% for imipenem, and 11.11% for tigecycline. In addition, most A. baumannii belonged to the group of multidrug-resistant (MDR) strains, with an antibiotic-resistance rate of 90.48% for meropenem and 16.00% for amikacin. However, polymyxin-resistant A. baumannii strains were not detected. Four strains of methicillin-resistant S. aureus (MRSA) (4/21, 19.05%) and one strain of vancomycin-resistant enterococci (VRE) were detected, with a resistance rate of 4.76 and 2.32%, respectively. Among the isolated 55 fungal strains, C. parapsilosis was the most common one (30/55, 56.36%), with an antibiotic-resistance rate of 5.77% for voriconazole, fluconazole, and itraconazole. The presence of amphotericin B-or flucytosine-resistant strains was not observed. Compared with the patients with Gram-positive and fungal pathogens, patients with Gram-negative bacteria exhibited the highest sequential organ failure assessment (SOFA) score (P < 0.001), lowest Glasgow Coma Scale (GCS) (P = 0.010), lowest platelet (PLT) value (P < 0.001), highest plasma creatinine (Cr) value (P = 0.016), and the highest procalcitonin (PCT) value (P < 0.001). The AUC in the ROC curve was 0.698 for the differentiation of Gram-negative BSI from Gram-positive BSI. A cutoff value of 8.47 ng/mL for PCT indicated a sensitivity of 56.9% and a specificity of 75.5%. The AUC in the ROC curve was 0.612 for the differentiation of bacteremia from fungemia. A cutoff value of 4.19 ng/mL for PCT indicated a sensitivity of 56.8% and a specificity of 62.7%.

Conclusion

Among the bloodstream infection strains in ICU, Gram-negative bacteria have the highest drug resistance rate, and will cause more serious brain damage, renal function damage and thrombocytopenia. So clinician should pay more attention to the treatment of Gram-negative bacteria in patients with bloodstream infection in ICU. The test index of PCT can be used to distinguish Gram-negative bacteremia from Gram-positive and bacteremia from fungemia but not as an effective indicator, thereby indicating the need for further large-scale research.

Is Piperacillin-Tazobactam an Appropriate Empirical Agent for Hospital-Acquired Sepsis and Community-Acquired Septic Shock of Unknown Origin in Australia?

Early appropriate empirical antibiotics are critical for reducing mortality in sepsis. For hospital-acquired sepsis of unknown origin in Australia, piperacillin-tazobactam (TZP) is recommended as an empirical therapy. Anecdotally, some institutions also use TZP for community-acquired septic shock. This narrative review aimed to scrutinise the appropriateness of TZP as an empirical agent for undifferentiated hospital-acquired sepsis and community-acquired septic shock. An online database (Medline) was searched for relevant studies in adults published in the last 10 years. Studies were included if they addressed separately reported clinical outcomes related to a relevant aspect of TZP therapy in sepsis. Of 290 search results, no studies directly addressed the study aim. This review therefore explores several themes that emerged from the contemporary literature, all of which must be considered to fully interrogate the appropriateness of TZP use in this context. This review reveals the paucity and low quality of evidence available for TZP use in sepsis of unclear origin, while demonstrating the urgent need and equipoise for an Australian audit of TZP use in patients with sepsis of unknown origin.

Introducing the Escalation Antibiogram: A Simple Tool to Inform Changes in Empiric Antimicrobials in the Non-Responding Patient

BACKGROUND

Hospital antibiograms guide initial empiric antibiotic treatment selections, but do not directly inform escalation of treatment among non-responding patients.

METHODS

Using Gram-negative bacteremia (GNB) as an exemplar condition, we sought to introduce the concept of an Escalation Antibiogram. Among GNBs between 2017-2020 from six hospitals in the Greater Toronto Area, we generated escalation antibiograms for each of 12 commonly used agents. Among organisms resistant to that antibiotic, we calculated the likelihood of susceptibility to each of the other 11 agents. In subgroup analyses, we examined escalation antibiograms across study years, individual hospitals, community versus hospital onset, and pathogen type.

RESULTS

Among 6577 GNB episodes, the likelihood of coverage was: ampicillin 31.8%, cefazolin 62.7%, ceftriaxone 67.1%, piperacillin-tazobactam 72.5%, ceftazidime 74.1%, trimethoprim-sulfamethoxazole 74.4%, ciprofloxacin 77.1%, tobramycin 88.3%, gentamicin 88.8%, ertapenem 91.0%, amikacin 97.5%, and meropenem 98.2%. The escalation antibiograms revealed marked shifts in likelihood of coverage by the remaining 11 agents. For example, among ceftriaxone-resistant isolates piperacillin-tazobactam susceptibility (21.2%) was significantly lower than trimethoprim-sulfamethoxazole (54.2%, p<0.0001), ciprofloxacin (63.0%, p<0.0001), ertapenem (73.4%, p<0.0001), tobramycin (80.1%, p<0.0001), gentamicin (82.8%, p<0.0001), meropenem (94.3%, p<0.0001), and amikacin (97.1%, p<0.0001). Trimethoprim-sulfamethoxazole was the second ranked agent in the meropenem escalation antibiogram (49.6%), and first in the amikacin escalation antibiogram (86.0%). Escalation antibiograms were consistent across 4 study years and 6 hospitals.

CONCLUSION

Escalation antibiograms can be generated to inform empiric treatment changes in non-responding patients. These tools can yield important insights such as avoiding the common maneuver of escalating from ceftriaxone to piperacillin-tazobactam in suspected GNB.

Antimicrobial Stewardship Programs: A Review of Strategies to Avoid Polymyxins and Carbapenems Misuse in Low Middle-Income Countries

Antibiotics misuse and overuse are concerning issues worldwide, especially in low middle-income countries. These practices contribute to the increasing rates of antimicrobial resistance. One efficient strategy to avoid them is antimicrobial stewardship programs. In this review, we focus on the possible approaches to spare the prescription of polymyxins and carbapenems for the treatment of Acinetobacter baumannii, carbapenem-resistant Enterobacterales, and Pseudomonas aeruginosas infections. Additionally, we highlight how to implement cumulative antibiograms and biomarkers to a sooner de-escalation of antibiotics.

Outcome and failure analysis of 132 episodes of haematogenous periprosthetic joint infections – a cohort study

Background

Outcome of haematogenous periprosthetic joint infection (PJI) and reasons for failure are largely unknown.

Methods

Outcome of consecutive patients with haematogenous PJI treated at our institution between 2010 and 2019 was evaluated. Failure was classified as persistence or relapse of infection or new infection. Failure-free survival was assessed using Kaplan-Meier analysis. Proportions between groups were compared with Fisher's exact test.

Results

132 haematogenous PJI episodes involving knee (n=76), hip (n=54), shoulder (n=1) or elbow (n=1) prostheses experienced by 110 patients were included. Median follow-up was 20.7 months (range, 0.2-89.9 months). Haematogenous PJI were caused by Staphylococcus aureus (n=49), Streptococcus spp. (n=36), Enterococcus faecalis (n=17), Enterobacterales (n=16), coagulase-negative staphylococci (n=9) and others (n=6). Debridement and implant retention were performed in 50 (38%), prosthesis exchange or removal in 79 (60%) and no surgery in 3 episodes (2%). Treatment failed in 42 episodes (32%), including 6 infection-related deaths. Among 36 non-fatal failures, 21 were caused by a new pathogen and 8 by the same pathogen, in 7 episodes no pathogen was isolated. Of all non-fatal failures, 19 (53%) PJI were of haematogenous origin. Identification of the primary focus, causative pathogen and CRIME80-Score did not influence treatment outcome, but failure rate was higher following prosthesis retention compared to multi-stage exchange.

Conclusions

Persistence-/relapse-free survival after treatment of haematogenous PJI was high (84%). New haematogenous PJI due to the same or a new pathogen occurred frequently, reducing the treatment success to 62% after 4 years of follow-up, suggesting an individual predisposition to haematogenous PJI. The outcome was similar for different pathogens, but worse in episodes treated with prosthesis retention compared to multi-stage exchange.

Use of Antimicrobials for Bloodstream Infections in the Intensive Care Unit, a Clinically Oriented Review

Bloodstream infections (BSIs) in critically ill patients are associated with significant mortality. For patients with septic shock, antibiotics should be administered within the hour. Probabilistic treatment should be targeted to the most likely pathogens, considering the source and risk factors for bacterial resistance including local epidemiology. Source control is a critical component of the management. Sending blood cultures (BCs) and other specimens before antibiotic administration, without delaying them, is key to microbiological diagnosis and subsequent opportunities for antimicrobial stewardship. Molecular rapid diagnostic testing may provide faster identification of pathogens and specific resistance patterns from the initial positive BC. Results allow for antibiotic optimisation, targeting the causative pathogen with escalation or de-escalation as required. Through this clinically oriented narrative review, we provide expert commentary for empirical and targeted antibiotic choice, including a review of the evidence and recommendations for the treatments of extended-spectrum β-lactamase-producing, AmpC-hyperproducing and carbapenem-resistant Enterobacterales; carbapenem-resistant Acinetobacter baumannii; and Staphylococcus aureus. In order to improve clinical outcomes, dosing recommendations and pharmacokinetics/pharmacodynamics specific to ICU patients must be followed, alongside therapeutic drug monitoring.

Accuracy of Direct Antimicrobial Susceptibility of Gram-Negative Bacteria from Positive Blood Cultures using MicroScan System and Value of Using Expert Rules for β-Lactam Agents

Direct antimicrobial susceptibility testing (AST) of positive blood cultures with Gram-negative bacteria produces results within 24 h, compared to 48 to 96 h with conventional methods. Positive clinical blood cultures were studied, supplemented with contrived blood cultures inoculated with a spectrum of resistant isolates. Bacterial inocula used for direct AST were quantitated. Direct AST was performed using MicroScan NM43 trays inoculated directly from positive blood cultures (100 μL in 25 mL water) and incubated using a WalkAway instrument, with trays read after 16 h. Reference AST was performed the following day from growth on solid medium using the same trays. Agreement of AST results between direct and reference methods, with and without the use of three expert rules for β-lactams, was evaluated using FDA categorical agreement criteria. Of 86 specimens tested (41 clinical specimens and 45 contrived specimens), the mean bacterial load in positive blood cultures was 8.98 log₁₀ CFU/mL. Fifteen isolates contained extended-spectrum β-lactamases, and 27 contained carbapenemases. Of 1,985 pairs of AST categorical results for 25 antimicrobials, 55.0% were susceptible, 4.7% intermediate, and 40.4% resistant by reference testing. Overall categorical agreement was 92.3%, with 5.3% minor errors, 1.9% major errors, and 0.4% very major errors. Agreement was higher for non-β-lactam agents (95.8%) than for β-lactam agents (90.3%; P < 0.0001). Application of expert rules increased agreement for β-lactam agents to 94.6%. The methods used achieved the study goal of producing accurate, cost-effective AST results directly from positive blood cultures using MicroScan trays with a 16-h incubation time without the need for additional testing. Use of three expert β-lactam rules improved accuracy.

Controversies in the management of ESBL-producing Enterabacterales. Clinical Implications

Extended-spectrum β-lactamases (ESBL)-producing organisms currently represent a major health problem. Although recently published guidelines still consider carbapenems as the treatment of choice for ESBL-producing infections, it is necessary to find non-carbapenem β-lactams as alternatives to reduce the effects associated with their overutilization. In this review we focus on these alternatives to carbepenem use. It is possible that piperacillin-tazobactam may be an alternative in clinical settings with "low inoculum" infections like urinary tract infections. Newer β-lactam-β-lactamase inhibitors (BLBLIs) are potential options too. The current available data support the efficacy of both ceftazidime-avibactam and ceftolozane-tazobactam against susceptible ESBL-producing Enterobacterales (ESBL-E). We are waiting for the results of MERINO-3 study to confirm whether ceftolozane-tazobactam is a good option versus meropenem for treating bloodstream infections caused by ESBL- or AmpC-producing Enterobacterales.

European Society of clinical microbiology and infectious diseases (ESCMID) guidelines for the treatment of infections caused by Multidrug-resistant Gram-negative bacilli (endorsed by ESICM -European Society of intensive care Medicine)

SCOPE

These ESCMID guidelines address the targeted antibiotic treatment of 3^rd generation cephalosporin-resistant Enterobacterales (3GCephRE) and carbapenem-resistant Gram-negative bacteria, focusing on the effectiveness of individual antibiotics and on combination vs. monotherapy.

METHODS

An expert panel was convened by ESCMID. A systematic review was performed including randomized controlled trials and observational studies, examining different antibiotic treatment regimens for the targeted treatment of infections caused by the 3GCephRE, carbapenem-resistant Enterobacterales (CRE), carbapenem-resistant Pseudomonas aeruginosa (CRPA) and carbapenem-resistant Acinetobacter baumanni (CRAB). Treatments were classified as head-to-head comparisons between individual antibiotics and monotherapy vs. combination therapy regimens, including defined monotherapy and combination regimens only. The primary outcome was all-cause mortality, preferably at 30 days and secondary outcomes included clinical failure, microbiological failure, development of resistance, relapse/recurrence, adverse events and length of hospital stay. The last search of all databases was conducted in December 2019, followed by a focused search for relevant studies up until ECCMID 2021. Data were summarized narratively. The certainty of the evidence for each comparison between antibiotics and between monotherapy vs. combination therapy regimens was classified by the GRADE recommendations. The strength of the recommendations for or against treatments was classified as strong or conditional (weak).

RECOMMENDATIONS

The guideline panel reviewed the evidence per pathogen, preferably per site of infection, critically appraising the existing studies. Many of the comparisons were addressed in small observational studies at high risk of bias only. Notably, there was very little evidence on the effects of the new, recently approved, beta-lactam beta-lactamase inhibitors on infections caused by carbapenem-resistant Gram-negative bacteria. Most recommendations are based on very-low and low certainty evidence. A high value was placed on antibiotic stewardship considerations in all recommendations, searching for carbapenem-sparing options for 3GCephRE and limiting the recommendations of the new antibiotics for severe infections, as defined by the sepsis-3 criteria. Research needs are addressed.

Infectious Diseases Society of America Guidance on the Treatment of AmpC β-lactamase-Producing Enterobacterales, Carbapenem-Resistant Acinetobacter baumannii, and Stenotrophomonas maltophilia Infections

BACKGROUND

The Infectious Diseases Society of America (IDSA) is committed to providing up-to-date guidance on the treatment of antimicrobial-resistant infections. A previous guidance document focused on infections caused by extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), carbapenem-resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with difficult-to-treat resistance (DTR-P. aeruginosa). Here, guidance is provided for treating AmpC β-lactamase-producing Enterobacterales (AmpC-E), carbapenem-resistant Acinetobacter baumannii (CRAB), and Stenotrophomonas maltophilia infections.

METHODS

A panel of six infectious diseases specialists with expertise in managing antimicrobial-resistant infections formulated questions about the treatment of AmpC-E, CRAB, and S. maltophilia infections. Answers are presented as suggestions and corresponding rationales. In contrast to guidance in the previous document, published data on optimal treatment of AmpC-E, CRAB, and S. maltophilia infections are limited. As such, guidance in this document is provided as "suggested approaches" based on clinical experience, expert opinion, and a review of the available literature. Because of differences in the epidemiology of resistance and availability of specific anti-infectives internationally, this document focuses on the treatment of infections in the United States.

RESULTS

Preferred and alternative treatment suggestions are provided, assuming the causative organism has been identified and antibiotic susceptibility results are known. Approaches to empiric treatment, duration of therapy, and other management considerations are also discussed briefly. Suggestions apply for both adult and pediatric populations.

CONCLUSIONS

The field of antimicrobial resistance is highly dynamic. Consultation with an infectious diseases specialist is recommended for the treatment of antimicrobial-resistant infections. This document is current as of September 17, 2021 and will be updated annually. The most current versions of IDSA documents, including dates of publication, are available at www.idsociety.org/practice-guideline/amr-guidance-2.0/.