Assessing the potential for improved predictive capacity of antimicrobial resistance in outpatient Staphylococcus aureus isolates using seasonal and spatial antibiograms

BACKGROUND

While the use of cumulative susceptibility reports, antibiograms, is recommended for improved empiric therapy and antibiotic stewardship, the predictive ability of antibiograms has not been well-studied. While enhanced antibiograms have been shown to better capture variation in susceptibility profiles by characteristics such as infection site or patient age, the potential for seasonal or spatial variation in susceptibility has not been assessed as important in predicting likelihood of susceptibility.

METHODS

Utilizing Staphylococcus aureus isolates obtained in outpatient settings from a nationwide provider of care, the Veterans Health Administration, and a local provider of care, the University of Iowa Hospitals and Clinics, standard, seasonal and spatial antibiograms were created for five commonly used antibiotic classes: cephalosporins, clindamycin, macrolides, tetracycline, trimethoprim/sulfamethoxazole.

RESULTS

A total of 338,681 S. aureus isolates obtained in VHA outpatient settings from 2010 to 2019 and 6,817 isolates obtained in UIHC outpatient settings from 2014 to 2019 were used to generate and test antibiograms. Logistic regression modeling determined the capacity of these antibiograms to predict isolate resistance to each antibiotic class. All models had low predictive capacity, with areas under the curve of < 0.7.

CONCLUSIONS

Standard antibiograms are poor in predicting S. aureus susceptibility to antibiotics often chosen by clinicians, and seasonal and spatial antibiograms do not provide an improved tool in anticipating non-susceptibility. These findings suggest that further refinements to antibiograms may be necessary to improve their utility in informing choice of effective antibiotic therapy.

Secondary bacterial infections & extensively drug-resistant bacteria among COVID-19 hospitalized patients at the University Hospital in Kraków

INTRODUCTION

Healthcare-associated infections (HAI) and bacterial antimicrobial resistance posed a therapeutic risk during the coronavirus disease 2019 (COVID-19) pandemic. The aim of this study was to analyze the HAIs in COVID-19 patients in the Intensive Care Unit (ICU) and non-ICU at the University Hospital in Krakow (UHK) with an emphasis on the susceptibility of the most frequently isolated pathogens and the prevalence of extensively drug resistant (XDR) microorganisms.

METHODS

This laboratory-based study was carried out at the University Hospital in Krakow in the ICU and non-ICUs dedicated to COVID-19 patients between May 2021 and January 2022. All isolates of Klebsiella pneumoniae were analyzed using PFGE protocol.

RESULTS

292 independent HAI cases were identified, with the predominance of urinary tract infections (UTI), especially in the non-ICU setting. The most common ICU syndrome was pneumonia (PNA). The prevalence of XDR organisms was 22.6% in the ICU and 14.8% in non-ICUs among all isolates. The incidence of carbapenem-resistant Enterobacteriaceae infection was 24.8 cases per 10,000 hospitalizations and the carbapenem-resistant A. baumannii infection incidence was 208.8 cases per 10,000 hospitalizations. The prevalence of XDR strains was highest in Acinetobacter spp, in PNA cases. The PFGE typing demonstrated that almost all XDR strains varied widely from each other.

CONCLUSIONS

In this study, there was a high incidence of HAI in COVID-19 patients, especially when compared to Western Europe and the United States. Similarly, the prevalence of XDR microorganisms, especially XDR-A.baumannii, was also high. PFGE did not confirm the horizontal spread of any organism strains.

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.

Enhancing the empiric antibiotic selection by introducing an antibiogram toolkit in a tertiary care hospital in Southern India - A prospective study

WHAT IS KNOWN AND OBJECTIVE

Antibiograms gives an overview of the cumulative susceptibility of formal antibiotics to bacterial isolates, which reflects the portion of each bacterium susceptible to a given antibiotic formulation by using antimicrobial susceptibility testing. The objective of this study is to gather and analyse data from drug utilization evaluation (DUE) studies and antimicrobial susceptibility tests in order to create an antibiogram toolkit that will help clinicians to select appropriate antimicrobial agents for initial empirical antibiotic therapy at point of care settings and avoid irrational use of antibiotics.

METHODS

A prospective interventional study was conducted at tertiary care hospital, biological samples of infectious patients were collected from various wards as per Clinical & Laboratory Standards Institute CLSI M39-A4 guidelines. Antimicrobial susceptibility results were analysed using WHONET software. Antibiotic stewardship committee was formed and involved in monitoring the usage of antibiotics, measuring outcomes, collecting feedback and finding the scope for improving the application of antibiogram toolkit in the hospital. Antibiotic usage tracking method was followed to know the level of adherence to the prescribing guidelines by the health care professionals.

RESULTS AND DISCUSSION

A total of 157 samples were obtained from various wards of the hospital. In that, Escherichia coli, Staphylococcus aureus and Klebsiella Pneumoniae were isolated in significant numbers. Antibacterial susceptibility results were collected, an initial antibiogram was developed for 18 antibacterial agents with respect to 3 gram-positive (+) and 1 gram-negative (-) organisms. 90% of prescribers mentioned that the antibiogram was useful, and 76% of them adhered to the guidelines. 26% were not adhered due to the patient-related factors.

WHAT IS NEW AND CONCLUSION

In our study, we have used qualitative and quantitative evaluation of drug utilization (DUE) reports to understand the existing prescribing pattern of antibiotics and setting target organisms and antibacterials to develop the hospital antibiogram. Combining DUE studies and antibiogram development was helpful in implementing effective antibiotic policies for the hospital. Further, this study pattern will be continued on a yearly basis and focused on developing cumulative antibiograms to understand the changes in resistance pattern of antimicrobials and utilization of antibiotics in the hospital.

The antibiogram: key considerations for its development and utilization

The antibiogram is an essential resource for institutions to track changes in antimicrobial resistance and to guide empirical antimicrobial therapy. In this Viewpoint, data and examples from literature are presented that suggest institutions have not completely adopted the standardized approach in developing antibiograms, as variations in the development methodologies of antibiograms exist despite consensus guidelines (M39) published by CLSI. We emphasize developing antibiograms in line with the M39 recommendations will help ensure that they are accurate, reliable and valid, and highlight that understanding the limitations of antibiogram data is critical to ensuring appropriate interpretation and application to clinical decision-making. We also stress the importance of easy accessibility and education on antibiogram use, to allow for prescribers to select the most optimal empirical treatment regimens and propose the creation of an abbreviated antibiogram for frontline users. Multidisciplinary antimicrobial stewardship programmes are vital to accomplishing these goals.

Antimicrobial stewardship and antibiograms: importance of moving beyond traditional antibiograms

The rapid evolution of resistance, particularly among Gram-negative bacteria, requires appropriate identification of patients at risk followed by administration of appropriate empiric antibiotic therapy. A primary tenet of antimicrobial stewardship programs (ASPs) is the establishment of empiric antibiotic recommendations for commonly encountered infections. An important tool in providing empiric antibiotic therapy recommendations is the use of an antibiogram. While the majority of institutions use a traditional antibiogram, ASPs have an opportunity to enhance antibiogram data. The authors provide the rationale for why ASPs should implement alternative antibiograms, and the importance of incorporating an antibiogram into clinical decision support systems with the goal of providing effective empiric antibiotic therapy.

A Combination Antibiogram Evaluation for Pseudomonas aeruginosa in Respiratory and Blood Sources from Intensive Care Unit (ICU) and Non-ICU Settings in U.S. Hospitals

Pseudomonas aeruginosa is an important pathogen associated with significant morbidity and mortality. U.S. guidelines for the treatment of hospital-acquired and ventilator-associated pneumonia recommend the use of two antipseudomonal drugs for high-risk patients to ensure that ≥95% of patients receive active empirical therapy. We evaluated the utility of combination antibiograms in identifying optimal anti-P. aeruginosa drug regimens. We conducted a retrospective cross-sectional analysis of the antimicrobial susceptibility of all nonduplicate P. aeruginosa blood and respiratory isolates collected between 1 October 2016 and 30 September 2017 from 304 U.S. hospitals in the BD Insights Research Database. Combination antibiograms were used to determine in vitro rates of susceptibility to potential anti-P. aeruginosa combination regimens consisting of a backbone antibiotic (an extended-spectrum cephalosporin, carbapenem, or piperacillin-tazobactam) plus an aminoglycoside or fluoroquinolone. Single-agent susceptibility rates for the 11,701 nonduplicate P. aeruginosa isolates ranged from 72.7% for fluoroquinolones to 85.0% for piperacillin-tazobactam. Susceptibility rates were higher for blood isolates than for respiratory isolates (P < 0.05). Antibiotic combinations resulted in increased susceptibility rates but did not achieve the goal of 95% antibiotic coverage. Adding an aminoglycoside resulted in higher susceptibility rates than adding a fluoroquinolone; piperacillin-tazobactam plus an aminoglycoside resulted in the highest susceptibility rate (93.3%). Intensive care unit (ICU) isolates generally had lower susceptibility rates than non-ICU isolates. Commonly used antipseudomonal drugs, either alone or in combination, did not achieve 95% coverage against U.S. hospital P. aeruginosa isolates, suggesting that new drugs are needed to attain this goal. Local institutional use of combination antibiograms has the potential to optimize empirical therapy of infections caused by difficult-to-treat pathogens.

An antibiotic stewardship exercise in the ICU: building a treatment algorithm for the management of ventilator-associated pneumonia based on local epidemiology and the 2016 Infectious Diseases Society of America/American Thoracic Society guidelines

Introduction

Management of ventilator-associated pneumonia (VAP), the most common infection in patients on mechanical ventilation, should be tailored to local microbiological data. The aim of this study was to determine susceptibility patterns of organisms causing VAP to develop a treatment algorithm based on these findings and evidence from the literature.

Materials and methods

This is a retrospective analysis of the microbiological etiology of VAP in the intensive care unit (ICU) of a Lebanese tertiary care hospital from July 2015 to July 2016. We reviewed the latest clinical practice guidelines on VAP and tried to adapt these recommendations to our setting.

Results

In all, 43 patients with 61 VAP episodes were identified, and 75 bacterial isolates caused VAP. Extensively drug-resistant (XDR) Acinetobacter baumannii was the most common organism (37%), and it had occurred endemically throughout the year. Pseudomonas aeruginosa was the next most common organism (31%), and 13% were XDR. Enterobacteriaceae (15%) and Stenotrophomonas maltophilia (12%) shared similar incidences. Our algorithm was based on guidelines, in addition to trials, systematic reviews, and meta-analyses that studied the effectiveness of available antibiotics in treating VAP.

Conclusion

Knowing that resistance can rapidly develop within a practice environment, more research is needed to identify the best strategy for the management of VAP.

Antimicrobial susceptibilities of respiratory pathogens in the surgical/trauma intensive care unit compared with the hospital-wide respiratory antibiogram in a level I trauma center

BACKGROUND

Unit-specific antibiograms have developed to guide clinicians to appropriate antibiotic choices for subsets of patients. The additional level of a unit- and respiratory-specific antibiogram for surgical and trauma patients defines key differences in susceptibility information for treating hospital-acquired pneumonia.

METHODS

This was a three-year, retrospective single-center study. A total of 729 positive respiratory specimens from 612 patients were analyzed using Quality Compass Pathfinder(®), the antibiotic-reporting software. Culture and susceptibility reports were compared for the surgical/trauma intensive care unit (S/TICU) and the general hospital (excluding the S/TICU but including the medical ICU [MICU]). Data were filtered to include those genera and organisms with a high association with hospital-acquired pneumonia: Acinetobacter, Citrobacter, Enterobacter, Escherichia coli, Haemophilus, Klebsiella, Neisseria, Pseudomonas, Staphylococcus, Stenotrophomonas, Streptococcus, and Serratia.

RESULTS

For gram-negative organisms, susceptibility differences were noted for Acinetobacter and Pseudomonas between the S/TICU and the rest of the hospital. In particular, Acinetobacter was significantly more susceptible to ciprofloxacin (86% vs. 43%; p<0.001), gentamicin (86% vs. 54%; p=0.001), imipenem-cilastatin (93% vs. 55%; p<0.001), trimethoprim-sulfamethoxazole (88% vs. 54%; p=0.001), and tobramycin (50% vs. 0; p=0.012). Pseudomonas isolates from the S/TICU were significantly more susceptible to aztreonam (83% vs. 68%; p=0.037), ciprofloxacin (86% vs. 69%; p=0.019), and imipenem-cilastatin (94% vs. 79%; p=0.01). For gram-positive organisms, Staphylococcus isolates from the S/TICU were significantly more susceptible to erythromycin (81% vs. 57%; p=0.007) and trimethoprim-sulfamethoxazole (98% vs. 91%; p=0.034) than were the hospital isolates.

CONCLUSIONS

For key respiratory pathogens, such as Pseudomonas, Acinetobacter, and Staphylococcus, surgical and trauma patients present greater susceptibility to several antibiotics. Although this information cannot be extrapolated to other institutions, it does provide a basis for comparable institutions to consider developing unit- and collection-site-specific antibiograms for infections that affect surgical/trauma patients commonly.

The Use of a Combination Antibiogram to Assist with the Selection of Appropriate Antimicrobial Therapy for Carbapenemase-Producing Enterobacteriaceae Infections

Combination antibiograms can be used to evaluate organism cross-resistance among multiple antibiotics. As combination therapy is generally favored for the treatment of carbapenemase-producing Enterobacteriaceae (CPE), combination antibiograms provide valuable information about the combination of antibiotics that achieve the highest likelihood of adequate antibiotic coverage against CPE.

Management of Infections with Drug-Resistant Organisms in Critical Care: An Ongoing Battle

Infections with multidrug-resistant organisms (MDROs) are common in critically ill patients and are challenging to manage appropriately. Strategies that can be used in the treatment of MDRO infections in the intensive care unit (ICU) include combination therapy, adjunctive aerosolized therapy, and optimization of pharmacokinetics with higher doses or extended-infusion therapy as appropriate. Rapid diagnostic tests could assist in improving timely appropriate antimicrobial therapy for MDRO infections in the ICU.

[Antimicrobial susceptibility cumulative reports]

Cumulative reports on antimicrobial susceptibility tests data are important for selecting empirical treatments, as an educational tool in programs on antimicrobial use, and for establishing breakpoints defining clinical categories. These reports should be based on data validated by clinical microbiologists using diagnostic samples (not surveillance samples). In order to avoid a bias derived from including several isolates obtained from the same patient, it is recommended that, for a defined period, only the first isolate is counted. A minimal number of isolates per species should be presented: a figure of >=30 isolates is statistically acceptable. The report is usually presented in a table format where, for each cell, information on clinically relevant microorganisms-antimicrobial agents is presented. Depending on particular needs, multiple tables showing data related to patients, samples, services or special pathogens can be prepared.

The role of the microbiology laboratory in antimicrobial stewardship programs

One of the impediments to the success of antimicrobial stewardship is the lack of availability of rapid and sensitive laboratory tests. The last decade has seen an explosion in new technologies that permit, in less than 4 hours, the identification of organisms and their resistance markers. In addition, the use of biomarkers has been explored in algorithms to distinguish infections that require antimicrobial agents. Clinical microbiology laboratories also contribute to the success of stewardship programs through compilation of aggregate antimicrobial susceptibility data. This article reviews rapid diagnostics, the use of biomarkers, and antibiogram development to antimicrobial stewardship activities and the subsequent impact on patient outcomes.

Variation in antibiotic susceptibility of uropathogens by age among ambulatory pediatric patients

We compared uropathogen antibiotic susceptibility across age groups of ambulatory pediatric patients. For Escherichia coli (n=5,099) and other Gram-negative rods (n=626), significant differences (p<0.05) existed across age groups for ampicillin, cefazolin, and trimethoprim/sulfamethoxazole susceptibility. In E. coli, differences in trimethoprim/sulfamethoxazole susceptibility varied from 79% in children under 2 to 88% in ages 16-18 (p<0.001), while ampicillin susceptibility varied from 30% in children under 2 to 53% in ages 2-5 (p=0.015). Uropathogen susceptibility to common urinary anti-infectives may be lower in the youngest children. Further investigation into these differences is needed to facilitate appropriate and prudent treatment of urinary tract infections.

Variability in pediatric infectious disease consultants' recommendations for management of community-acquired pneumonia

Background

Community-acquired pneumonia (CAP) is a common childhood infection. CAP complications, such as parapneumonic empyema (PPE), are increasing and are frequently caused by antibiotic-resistant organisms. No clinical guidelines currently exist for management of pediatric CAP and no published data exist about variations in antibiotic prescribing patterns. Our objectives were to describe variation in CAP clinical management for hospitalized children by pediatric infectious disease consultants and to examine associations between recommended antibiotic regimens and local antibiotic resistance levels.

Methods

We surveyed pediatric members of the Emerging Infections Network, which consists of 259 pediatric infectious disease physicians. Participants responded regarding their recommended empiric antibiotic regimens for hospitalized children with CAP with and without PPE and their recommendations for duration of therapy. Participants also provided information about the prevalence of penicillin non-susceptible S. pneumoniae and methicillin-resistant S. aureus (MRSA) in their community.

Results

We received 148 responses (57%). For uncomplicated CAP, respondents were divided between recommending beta-lactams alone (55%) versus beta-lactams in combination with another class (40%). For PPE, most recommended a combination of a beta-lactam plus an anti-MRSA agent, however, they were divided between clindamycin (44%) and vancomycin (57%). The relationship between reported antibiotic resistance and empiric regimen was mixed. We found no relationship between aminopenicillin use and prevalence of penicillin non-suscepetible S. pneumoniae or clindamycin use and clindamycin resistance, however, respondents were more likely to recommend an anti-MRSA agent when MRSA prevalence increased.

Conclusions

Substantial variability exists in recommendations for CAP management. Development of clinical guidelines via antimicrobial stewardship programs and dissemination of data about local antibiotic resistance patterns represent opportunities to improve care.