Consequences of revised CLSI and EUCAST guidelines for antibiotic susceptibility patterns of ESBL- and AmpC β-lactamase-producing clinical Enterobacteriaceae isolates

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.

Prevalence of ESBL-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae in treated wastewater: a comparison with nosocomial infection surveillance

The increasing prevalence of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli and carbapenem-resistant Enterobacteriaceae (CRE) is a worldwide health threat. Monitoring of these resistant bacteria in the environment can provide regional prevalence reflecting both healthy and infected populations, although the quantitative monitoring of those resistant bacteria, especially CRE, is difficult due to their low proportion in the total Enterobacteriaceae population and the possible interference by autochthonous species with intrinsic resistance. In this study, these resistant bacteria in treated wastewater were quantified at 12 different treatment plants. The proportions of cefotaxime-resistant and ESBL-producing E. coli in the total E. coli population in the chlorinated effluents in Tokyo were 5.7 and 5.3%, respectively. The estimated proportion of CRE was 0.007% with the constituting species of Klebsiella spp. and Enterobacter spp., although the conditions during the first incubation may have affected the estimation even after the correction by the proportion of resistant population in the isolates. The observed resistant proportions in this study were lower than those in the surveillance on nosocomial infection not only for inpatients but also for outpatients, and higher than those in the veterinary monitoring.

Combined Molecular and Phenotypic Antimicrobial Susceptibility Testing Is Beneficial in Detection of ESBL and AmpC Beta-Lactamase Producing Isolates of Enterobacteriaceae in Pediatric Patients with Bloodstream Infections

Objectives: The aim was to assess the potential advantage of combined genotypic testing with phenotypic antimicrobial susceptibility testing (AST) to detect AmpC β-lactamases (AmpC) and extended-spectrum β-lactamases (ESBL) producing Enterobacteriaceae isolated from blood cultures in a pediatric population. Materials and Methods: All first-time Enterobacteriaceae isolates recovered from blood cultures of pediatric patients at the Cincinnati Children's Hospital Medical Center between January 2017 and December 2018 were evaluated. The Check-MDR CT103XL β-lactamase assay was used to determine the presence of AmpC and ESBL, while AST was performed using the VITEK 2 platform. Phenotypic ESBL resistance was defined by resistance to either ceftriaxone or ceftazidime using Clinical and Laboratory Standards Institute breakpoints, while combined cefoxitin resistance with ceftriaxone or ceftazidime resistance was used to detect AmpCs (as per European Committee on Antimicrobial Susceptibility Testing standards). Results: Overall, there were 170 isolates. Genotypically, 21 (12.4%) had AmpC and 18 (10.6%) had ESBL genes detected. Phenotypically, 11 (6.5%) isolates were AmpC and 26 (15.3%) were ESBL producing organisms. Genotypic testing identified an additional 14 AmpC and two ESBL isolates that failed to meet phenotypic criteria. Conclusions: Using combined genotypic and phenotypic methods to detect AmpC and ESBL producing organisms increased the identification of resistant organism and provided potentially clinical relevant data to guide the treatment of resistant organisms.

From CLSI to EUCAST, a necessary step in Spanish laboratories

The Spanish Antibiogram Committee (Comité Español del Antibiograma, COESANT) presents in this document a simple "roadmap" or decalogue of recommendations, with a view to facilitating the transition from the Clinical and Laboratory Standards Institute (CLSI) to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) antimicrobial susceptibility testing regulations to the Clinical Microbiology Spanish laboratories that still use the CLSI guidelines. The objectives are to adapt the closer European regulations to the Spanish clinical and epidemiological reality and to fully implement the EUCAST recommendations in all microbiology laboratories in Spain.

Management of infections caused by extended-spectrum β-lactamase-producing Enterobacteriaceae: current evidence and future prospects

INTRODUCTION

The spread of extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae has become a major public health threat worldwide. Area covered: A thorough systematic literature review describing the current evidence and future prospects of therapeutic options for infections caused by ESBL-producing Enterobacteriaceae. Expert commentary: The methods of detecting ESBLs have been evolving. The Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing lowered the MIC breakpoints of cephalosporins against ESBL-producing Enterobacteriaceae in 2010. Phenotypic testing for ESBLs is no longer recommended. Instead, the selection of appropriate antimicrobial agents largely depends on the report of minimum inhibitory concentrations (MICs). To date, therapeutic options for these multidrug-resistant organisms remain limited. The clinical efficacy of piperacillin/tazobactam and cefepime on in vitro-susceptible ESBL-producing Enterobacteriaceae remains a concern. Many studies found an in vitro-in vivo discordance based on current breakpoints. Carbapenems are the most reliable antibiotics for severe infections caused by ESBL-producing Enterobacteriaceae. However, their overuse has led to a serious problem of increasing drug resistance. Recently, ceftolozane/tazobactam and ceftazidime/avibactam have been approved for the treatment of complicated urinary tract infections and complicated intra-abdominal infections. The introduction of these new β-lactam/β-lactamase inhibitor combinations offers new carbapenem-sparing options for the treatment of ESBL infections.

Impact of CLSI and EUCAST Cefepime breakpoint changes on the susceptibility reporting for Enterobacteriaceae

OBJECTIVE

We analyzed the effects of different cefepime MIC breakpoints on Enterobacteriaceae cefepime susceptibility and the presence of AmpC and extended-spectrum β-lactamase (ESBL) genes within the cefepime MIC interpretative categories.

METHODS

Using Enterobacteriaceae susceptibility data from 2013 comparisons of MIC breakpoints were performed using Pearson's chi-squared test. Molecular testing on a subset of isolates was done.

RESULTS

Among 3784 non-duplicate clinical isolates, cefepime susceptibility decreased from 97.6% to 96.1% to 93.7% for CLSI 2013, CLSI 2014, and EUCAST 2011, respectively. In ceftriaxone non-susceptible isolates, cefepime susceptibility decreased from 79% to 66% (P<0.0001) using CLSI 2013 and 2014, respectively, which was greater and statistically significant for Escherichia coli and Klebsiella spp. but not for Enterobacter spp. (P=0.06). Isolates with MIC ≤1μg/mL more often harbored AmpC (77%) than ESBL (18%) genes.

CONCLUSIONS

Lower cefepime MIC breakpoints decrease cefepime susceptibility for isolates harboring ESBLs, while sparing the majority of those with AmpCs.

Antibiotic resistance & pathogen profile in ventilator-associated pneumonia in a tertiary care hospital in India

Background & objectives:

Ventilator-associated pneumonia (VAP) is an important hospital-acquired infection with substantial mortality. Only a few studies are available from India addressing the microbiological aspects of VAP, which have been done with small study populations. This study was carried out in the intensive care units (ICUs) of a tertiary care hospital to assess the profile of pathogens and to determine the pattern of antimicrobial resistance.

Methods:

This was a retrospective study of clinically suspected cases of VAP. Over a three year period, a total of 247 cases in 2011, 297 in 2012 and 303 in 2013 admitted in ICUs on mechanical ventilation with clinical evidence of VAP were included in our study. The endotracheal aspirate samples from these suspected cases were subjected to quantitative culture technique, and colony count of ≥10⁵ colony forming units/ml was considered significant. Antimicrobial susceptibility test for the isolates was done.

Results:

VAP rates of 44.1, 43.8 and 26.3 were seen in 2011, 2012 and 2013, respectively. In all the three years, non-fermentative Gram-negative bacilli were the predominant organisms, followed by Pseudomonas spp. and Klebsiella spp. Staphylococcus aureus exhibited a downwards trend in prevalence from 50.0 per cent in 2011 to 34.9 per cent in 2013. An increase in vancomycin-resistant enterococci was seen from 4.3 per cent in 2012 to 8.3 per cent in 2013, while methicillin resistance amongst the S. aureus crossed the 50 per cent mark in 2013. An increasing trend in resistance was shown by Pseudomonas spp. for piperacillin-tazobactam (PTZ), amikacin and imipenem (IPM). For the non-fermenters, resistance frequency remained very high except for IPM (33.1%) and polymyxin-B (2.4%).

Interpretation & conclusions:

Our findings show VAP as an important problem in the ICU setting. The incidence of multidrug-resistant pathogens was on the rise. The resistance pattern of these pathogens can help an institution to formulate effective antimicrobial policy. To have a comprehensive pan-India picture, multicentric studies are needed.

Molecular Characteristics and Antibiotic Resistance Profiles of Klebsiella Isolates in Mthatha, Eastern Cape Province, South Africa

The increase in the incidence of extended-spectrum β-lactamase- (ESBL-) producing Klebsiella species has become a serious problem worldwide, because of their incrimination in antibiotic resistance. The objective of this study is to investigate the resistance genes responsible for ESBL-producing Klebsiella species and carbapenemase-producing Klebsiella (CRE) isolated in Mthatha and to study their epidemiology. A prospective, descriptive study of 202 nonrepetitive samples from patients was obtained from Nelson Mandela Academic Hospital. The cultured Klebsiella isolates were subjected to antimicrobial susceptibility tests and the polymerase chain reaction of bla_CTX-M, bla_TEM, bla_SHV, bla_KPC, and bla_NDM genes. Overall K. pneumoniae were the majority with 169 (83.7%) species isolates, followed by K. oxytoca with 29 (14.4%), while K. ozaenae and Raoultella ornithinolytica were 2 (0.9%) each. The prevalence of ESBL production in all Klebsiella species was 117 (57.9%). ESBL-genotypic resistance is driven in Mthatha by bla_SHV 121 (77.1%) followed by bla_TEM 105 (66.9%) and bla_CTX-M at 89 (56.7%). The most common ESBL genotype combination among the Klebsiella was bla_TEM + bla_SHV + bla_CTX-M at 79 (50.3%). There is a steady increase in the rate of ESBL genes in the last five years.

Towards better antimicrobial susceptibility testing: impact of the Journal of Antimicrobial Chemotherapy

Susceptibility testing of bacteria is one of the most important tests performed in a clinical microbiology laboratory. Improvements in laboratory techniques, especially the move towards standardized susceptibility testing, has provided better consistency and accuracy of testing. When used in conjunction with the most recently developed interpretative criteria, the result is better prediction of the outcome of antimicrobial therapy for infected patients. Throughout the last four decades this Journal has published numerous articles evidencing improvements and new techniques, a valuable source of information for microbiology laboratories.

Commiphora leptophloeos Phytochemical and Antimicrobial Characterization

Commiphora leptophloeos is a plant specie usually known for its medicinal purposes in local communities in Northeast Brazil. In order to evaluate its therapeutic potential, we aimed to determine the phytochemical and antimicrobial properties of C. leptophloeos extracts. Thin Layer Chromatography (TLC) was able to detect the presence of phenolic compounds, flavonoids and reducing sugars. Three phenolic compounds were identified by HPLC and described as Gallic, Chlorogenic and Protocatechuic acids. On the other hand, H1NMR analysis revealed the presence of hinokinin, a bioactive lignan further characterized in the present work. The minimum inhibitory concentration (MIC) values for hinokinin ranged from 0.0485 to 3.125 mg/mL in different S. aureus clinical isolates and showed a bactericidal activity against MRSA isolated from blood (MMC 0.40 mg/mL) and postoperative secretion (MMC = 3.125 mg/mL). C. leptophloeos extracts also showed antimicrobial activity against Mycobacterium species such as M. smegmatis (MIC = 12.5 mg/mL) and M. tuberculosis (MIC = 52 mg/mL). Additionally, we determined the toxicity of C. leptophloeos by in vitro HC50 tests with hemolytic activity detected of 313 ± 0.5 μg/mL. Our results showed that C. leptophloeos possesses inhibitory properties against MRSA as well as several other clinically important microorganisms. Furthermore, the present work is the first report of the presence of hinokinin in Commiphora genus.

A new look at the drug-resistance investigation of uropathogenic E. coli strains

Bacterial drug resistance and uropathogenic tract infections are among the most important issues of current medicine. Uropathogenic Escherichia coli strains are the primary factor of this issue. This article is the continuation of the previous study, where we used Kohonen relations to predict the direction of drug resistance. The characterized collection of uropathogenic E. coli strains was used for microbiological (the disc diffusion method for antimicrobial susceptibility testing), chemical (ATR/FT-IR) and mathematical (artificial neural networks, Ward's hierarchical clustering method, the analysis of distributions of inhibition zone diameters for antibiotics, Cohen's kappa measure of agreement) analysis. This study presents other potential tools for the epidemiological differentiation of E. coli strains. It is noteworthy that ATR/FT-IR technique has turned out to be useful for the quick and simple identification of MDR strains. Also, diameter zones of resistance of this E. coli population were compared to the population of E. coli strains published by EUCAST. We observed the bacterial behaviors toward particular antibiotics in comparison to EUCAST bacterial collections. Additionally, we used Cohen's kappa to show which antibiotics from the same class are closely related to each other and which are not. The presented associations between antibiotics may be helpful in selecting the proper therapy directions. Here we present an adaptation of interdisciplinary studies of drug resistance of E. coli strains for epidemiological and clinical investigations. The obtained results may be some indication in deciding on antibiotic therapy.

Markov Networks of Collateral Resistance: National Antimicrobial Resistance Monitoring System Surveillance Results from Escherichia coli Isolates, 2004-2012

Surveillance of antimicrobial resistance (AMR) is an important component of public health. Antimicrobial drug use generates selective pressure that may lead to resistance against to the administered drug, and may also select for collateral resistances to other drugs. Analysis of AMR surveillance data has focused on resistance to individual drugs but joint distributions of resistance in bacterial populations are infrequently analyzed and reported. New methods are needed to characterize and communicate joint resistance distributions. Markov networks are a class of graphical models that define connections, or edges, between pairs of variables with non-zero partial correlations and are used here to describe AMR resistance relationships. The graphical least absolute shrinkage and selection operator is used to estimate sparse Markov networks from AMR surveillance data. The method is demonstrated using a subset of Escherichia coli isolates collected by the National Antimicrobial Resistance Monitoring System between 2004 and 2012 which included AMR results for 16 drugs from 14418 isolates. Of the 119 possible unique edges, 33 unique edges were identified at least once during the study period and graphical density ranged from 16.2% to 24.8%. Two frequent dense subgraphs were noted, one containing the five β-lactam drugs and the other containing both sulfonamides, three aminoglycosides, and tetracycline. Density did not appear to change over time (p = 0.71). Unweighted modularity did not appear to change over time (p = 0.18), but a significant decreasing trend was noted in the modularity of the weighted networks (p < 0.005) indicating relationships between drugs of different classes tended to increase in strength and frequency over time compared to relationships between drugs of the same class. The current method provides a novel method to study the joint resistance distribution, but additional work is required to unite the underlying biological and genetic characteristics of the isolates with the current results derived from phenotypic data.

Monitoring Antimicrobial Resistance in the Food Supply Chain and Its Implications for FDA Policy Initiatives

In response to concerning increases in antimicrobial resistance (AMR), the Food and Drug Administration (FDA) has decided to increase veterinary oversight requirements for antimicrobials and restrict their use in growth promotion. Given the high stakes of this policy for the food supply, economy, and human and veterinary health, it is important to rigorously assess the effects of this policy. We have undertaken a detailed analysis of data provided by the National Antimicrobial Resistance Monitoring System (NARMS). We examined the trends in both AMR proportion and MIC between 2004 and 2012 at slaughter and retail stages. We investigated the makeup of variation in these data and estimated the sample and effect size requirements necessary to distinguish an effect of the policy change. Finally, we applied our approach to take a detailed look at the 2005 withdrawal of approval for the fluoroquinolone enrofloxacin in poultry water. Slaughter and retail showed similar trends. Both AMR proportion and MIC were valuable in assessing AMR, capturing different information. Most variation was within years, not between years, and accounting for geographic location explained little additional variation. At current rates of data collection, a 1-fold change in MIC should be detectable in 5 years and a 6% decrease in percent resistance could be detected in 6 years following establishment of a new resistance rate. Analysis of the enrofloxacin policy change showed the complexities of the AMR policy with no statistically significant change in resistance of both Campylobacter jejuni and Campylobacter coli to ciprofloxacin, another second-generation fluoroquinolone.

Comparison of Clinical Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing guidelines for the interpretation of antibiotic susceptibility at a University teaching hospital in Nairobi, Kenya: a cross-sectional study

Background

The Clinical Laboratory Standards Institute (CLSI) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines are the most popular breakpoint guidelines used in antimicrobial susceptibility testing worldwide. The EUCAST guidelines are freely available to users while CLSI is available for non-members as a package of three documents for US $500 annually. This is prohibitive for clinical microbiology laboratories in resource poor settings. We set out to compare antibiotic susceptibility determined by the two guidelines to determine whether adoption of EUCAST guidelines would significantly affect our susceptibility patterns.

Methods

We reviewed minimum inhibitory concentrations (MIC) of various antibiotics routinely reported for Escherichia coli (E. coli), Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) isolates from an automated microbiology identification system (VITEK-2) at the Aga Khan University Hospital Nairobi’s Pathology department. These MICs were then analyzed using both CLSI 2015 and EUCAST 2015 guidelines and classified as resistant, intermediate or susceptible. We compared the susceptibility and agreement between the CLSI and EUCAST categorizations.

Results

Susceptibility data from a total of 5165 E. coli, 1103 S. aureus and 532 P. aeruginosa isolates were included. The concordance rates of the two guidelines for E. coli, S. aureus and P. aeruginosa ranged from 78.2 to 100 %, 94.6 to 100 % and 89.1 to 95.5 % respectively. The kappa statistics for E. coli MICs revealed perfect agreement between CLSI and EUCAST for cefotaxime, ceftriaxone and trimethoprim–sulfamethoxazole, almost perfect agreement for ampicillin, ciprofloxacin, cefuroxime, gentamicin and ceftazidime, substantial agreement for meropenem, moderate agreement for cefepime and amoxicillin-clavulanate, fair agreement for nitrofurantoin and poor agreement for amikacin. For S. aureus the kappa statistics revealed perfect agreement for penicillin, trimethoprim–sulfamethoxazole, levofloxacin, oxacillin, linezolid and vancomycin, almost perfect agreement for clindamycin, erythromycin and tetracycline and moderate agreement for gentamicin. For P. aeruginosa the kappa analysis revealed moderate to almost perfect agreement for all the anti-pseudomonal antibiotics.

Conclusion

The results show comparable antibiotic susceptibility patterns between CLSI and EUCAST breakpoints. Given that EUCAST guidelines are freely available, it makes it easier for laboratories in resource poor settings to have an updated and readily available reference for interpreting antibiotic susceptibilities.

Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.

Basis for selecting optimum antibiotic regimens for secondary peritonitis

Adequate management of severely ill patients with secondary peritonitis requires supportive therapy of organ dysfunction, source control of infection and antimicrobial therapy. Since secondary peritonitis is polymicrobial, appropriate empiric therapy requires combination therapy in order to achieve the needed coverage for both common and more unusual organisms. This article reviews etiological agents, resistance mechanisms and their prevalence, how and when to cover them and guidelines for treatment in the literature. Local surveillances are the basis for the selection of compounds in antibiotic regimens, which should be further adapted to the increasing number of patients with risk factors for resistance (clinical setting, comorbidities, previous antibiotic treatments, previous colonization, severity…). Inadequate antimicrobial regimens are strongly associated with unfavorable outcomes. Awareness of resistance epidemiology and of clinical consequences of inadequate therapy against resistant bacteria is crucial for clinicians treating secondary peritonitis, with delicate balance between optimization of empirical therapy (improving outcomes) and antimicrobial overuse (increasing resistance emergence).

Recent Updates on the Role of Pharmacokinetics-pharmacodynamics in Antimicrobial Susceptibility Testing as Applied to Clinical Practice

Given current challenges in antimicrobial resistance and drug development, infectious diseases clinicians must rely on their own ingenuity to effectively treat infections while preserving the current antimicrobial armamentarium. An understanding of pharmacokinetics (PK), pharmacodynamics (PD), antimicrobial susceptibility testing (AST), and how these concepts relate, is essential to this task. In this review, we discuss how and why PK-PD impacts AST and the way infectious diseases are being treated, with a particular focus on vancomycin for methicillin-resistant Staphylococcus aureus, penicillin for Streptococcus pneumoniae, and an update on cephalosporins for Enterobacteriaceae. Finally, we address how new ideas to exploit PK-PD can promote innovative study design and bring about more rapid regulatory review of new antimicrobials.

Outbreak of extended-spectrum β-lactamase-producing Escherichia coli transmitted through breast milk sharing in a neonatal intensive care unit

BACKGROUND

Routine surveillance in a neonatal intensive care unit (NICU) showed an increased detection of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (ESBL-E. coli) in August 2012, following nearly a year without detection.

AIM

To describe the investigation and interventions by a hospital infection control team of an outbreak of ESBL-E. coli in a NICU.

METHODS

Six neonates with positive cultures of ESBL-E. coli (five with respiratory colonization, one with a urinary tract infection), control infants who were negative for ESBL-E. coli during the study period, and mothers who donated their breast milk were included. A case-control study was performed to identify possible risk factors for positive ESBL-E. coli cultures and molecular typing of isolated strains by pulsed-field gel electrophoresis.

FINDINGS

The odds ratio for ESBL-E. coli infection after receiving shared unpasteurized breast milk during the study period was 49.17 (95% confidence interval: 6.02-354.68; P < 0.05). The pulsed-field gel electrophoresis pattern showed that all strains were identical, and the same pathogen was detected in freshly expressed milk of a particular donor. After ceasing the breast milk sharing, the outbreak was successfully terminated.

CONCLUSION

This outbreak indicates that contamination of milk packs can result in transmission of a drug-resistant pathogen to newborn infants. Providers of human breast milk need to be aware of the necessity for low-temperature pasteurization and bacterial cultures, which should be conducted before and after freezing, before prescribing to infants.

The contribution of extended-spectrum β-lactamases to multidrug-resistant infections in children

PURPOSE OF REVIEW

The prevalence of multidrug-resistant (MDR) infections caused by Gram-negative rods (GNRs) such as Escherichia coli and Klebsiella pneumoniae is increasing in large part because of the production of extended-spectrum β-lactamases (ESBLs) that confer resistance to third-generation cephalosporins such as ceftriaxone. This review examines the clinical implication of changes in the epidemiology, diagnostic tools, and reporting criteria for ESBL-GNRs.

RECENT FINDINGS

Pediatric ESBL-GNR infections, once associated only with hospitals, are increasing in the community. The most common risk factor for ESBL-GNR infection is previous antibiotic use. Evidence also exists for prolonged fecal carriage after discharge from neonatal ICUs, leading to community transmission with close contact of known carriers. Controversial changes in the laboratory criteria for GNR cephalosporin resistance have also contributed to the increased numbers of reported MDR-GNR infections. Newer diagnostic tools will enable more rapid identification of MDR-GNR infections, leading to earlier implementation of appropriate therapy.

SUMMARY

ESBL-GNR infections are no longer limited to ICUs and are now being identified in children presenting from the community. Appropriate antibiotic prescribing practices are critical to limit the spread of ESBL-GNRs, and pediatricians must prepare to identify and treat these challenging infections.

Prevalence of carbapenem-resistant organisms and other Gram-negative MDRO in German ICUs: first results from the national nosocomial infection surveillance system (KISS)

PURPOSE

Standardized prevalence and incidence data on carbapenem-resistant organisms (CRO) and, as a relevant subgroup, carbapenem-resistant Enterobacteriaceae (CRE) are scarce. CRO-surveillance within the German nosocomial infection surveillance system (KISS) aims to provide epidemiological surveillance data on CRO colonizations and infections.

METHODS

CRO-surveillance is part of a KISS-module for the surveillance of multidrug-resistant organisms (MDRO). MDRO-KISS methods require surveillance of all patients admitted to the ward and standardized documentation of imported and ICU-acquired cases. Data on all MDRO-carriers including colonization and infection with MDRO are collected. All presented data were routine data collected from January 1st 2013 until December 1st 2013 in accordance with the German Protection against Infection Act (IfSG).

RESULTS

341 ICUs submitted data on MDRO during the first year. In total, 5,171 cases of multidrug-resistant Gram-negative bacteria (MRGN) were identified. 848 were CRO (16%). 325 CRO-cases were acquired within the ICU (38%), and 373 CRO-patients had an infection (44%). CRO-prevalence was 0.29 per 100 patients. Acquisition rate of MRGN was 1.32 per 1,000 patient days. This rate is more than doubled the acquisition rates of other MDRO under surveillance within MDRO-KISS (0.57 MRSA, 0.49 VRE). CRO-acquisition rate was 0.3 per 1,000 patient days. Incidence density of MRGN infections bacteria was 0.58 per 1,000 patient days (CRO 0.15/1,000 patient days).

CONCLUSIONS

To date, CRO are common in German ICUs and the relatively large proportions of ICU-acquired CRO and infections emphasize their potential to cause outbreaks. High MRGN infection rates and high ESBL prevalence data from clinical studies suggest a lack of MRGN identification in asymptomatic carriers.

Impact of minimal inhibitory concentration breakpoints on local cumulative bacterial susceptibility data and antibiotic consumption

Background

The phenotypic antimicrobial susceptibility testing (AST) of bacteria depends on minimal inhibitory concentration breakpoints issued by national and international breakpoint committees. The current study was performed in order to test the influence of different AST standards on local cumulative AST data and on antibiotic consumption.

Methods

Automated AST was performed with clinical isolates of Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, and E. faecium. From each species 100 prospectively collected non-duplicate clinical isolates were tested and MIC data were interpreted according to the interpretation standards issued by DIN and EUCAST, respectively. In addition cumulative AST data from clinical isolates and antibiotic consumption were monitored before and after implementation of new EUCAST MIC breakpoints.

Results

The susceptibility rate of P. aeruginosa against piperacillin and gentamicin, and of C. freundii against piperacillin/tazobactam increased significantly, whereas the susceptibility rates of E. cloacae, S. marcescens, and M. morganii against ciprofloxacin decreased significantly after switching from DIN to EUCAST MIC breakpoints. These changes in the cumulative antibiotic resistance pattern were reflected by enhanced consumption of piperacillin/tazobactam after implementation of EUCAST MIC breakpoints.

Conclusions

These data show that changes of AST breakpoints have a significant influence on local cumulative AST data and on antibiotic consumption.

Integrating forecast probabilities in antibiograms: a way to guide antimicrobial prescriptions more reliably?

Antimicrobial susceptibility testing (AST) assigns pathogens to "susceptible" or "resistant" clinical categories based on clinical breakpoints (CBPs) derived from MICs or inhibition zone diameters and indicates the likelihood for therapeutic success. AST reports do not provide quantitative measures for the reliability of such categorization. Thus, it is currently impossible for clinicians to estimate the technical forecast uncertainty of an AST result regarding clinical categorization. AST error rates depend on the localization of pathogen populations in relation to CBPs. Bacterial species are, however, not homogeneous, and subpopulations behave differently with respect to AST results. We addressed how AST reporting errors differ between isolates with and without acquired drug resistance determinants. Using as an example the beta-lactams and their most important resistance mechanisms, we analyzed different pathogen populations for their individual reporting error probabilities. Categorization error rates were significantly higher for bacterial populations harboring resistance mechanisms than for the wild-type population. Reporting errors for amoxicillin-clavulanic acid and piperacillin-tazobactam in Escherichia coli infection cases were almost exclusively due to the presence of broad-spectrum- and extended-spectrum-beta-lactamase (ESBL)-producing microorganisms (79% and 20% of all errors, respectively). Clinicians should be aware of the significantly increased risk of erroneous AST reports for isolates producing beta-lactamases, particularly ESBL and AmpC. Including probability indicators for interpretation would improve AST reports.

Changing epidemiology of infections due to extended spectrum beta-lactamase producing bacteria

Background

Community-associated infections caused by extended-spectrum beta-lactamase (ESBL) producing bacteria are a growing concern.

Methods

Retrospective cohort study of clinical infections due to ESBL-producing bacteria requiring admission from 2006-2011 at a tertiary care academic medical center in Providence, RI.

Results

A total of 321 infections due to ESBL-producing bacteria occurred during the study period. Fifty-eight cases (18%) were community-acquired, 170 (53%) were healthcare–associated, and 93 (29%) were hospital-acquired. The incidence of ESBL infections per 10,000 discharges increased during the study period for both healthcare-associated infections, 1.9 per year (95% CI 1-2.8), and for community-acquired infections, 0.85 per year (95% CI 0.3-1.4) but the rate remained unchanged for hospital-acquired infections. For ESBL-producing E. coli isolates, resistance to both ciprofloxacin and trimethoprim-sulfamethoxazole was 95% and 65%, respectively but 94% of isolates were susceptible to nitrofurantoin.

Conclusions

Community-acquired and healthcare-associated infections due to ESBL-producing bacteria are increasing in our community, particularly urinary tract infections due to ESBL-producing E. coli. Most isolates are resistant to oral antibiotics commonly used to treat urinary tract infections. Thus, our findings have important implications for outpatient management of such infections.

Bugs, hosts and ICU environment: countering pan-resistance in nosocomial microbiota and treating bacterial infections in the critical care setting

ICUs are areas where resistance problems are the largest, and these constitute a major problem for the intensivist's clinical practice. Main resistance phenotypes among nosocomial microbiota are (i) vancomycin-resistance/heteroresistance and tolerance in grampositives (MRSA, enterococci) and (ii) efflux pumps/enzymatic resistance mechanisms (ESBLs, AmpC, metallo-betalactamases) in gramnegatives. These phenotypes are found at different rates in pathogens causing respiratory (nosocomial pneumonia/ventilator-associated pneumonia), bloodstream (primary bacteremia/catheter-associated bacteremia), urinary, intraabdominal and surgical wound infections and endocarditis in the ICU. New antibiotics are available to overcome non-susceptibility in grampositives; however, accumulation of resistance traits in gramnegatives has led to multidrug resistance, a worrisome problem nowadays. This article reviews microorganism/infection risk factors for multidrug resistance, suggesting adequate empirical treatments. Drugs, patient and environmental factors all play a role in the decision to prescribe/recommend antibiotic regimens in the specific ICU patient, implying that intensivists should be familiar with available drugs, environmental epidemiology and patient factors.