Antimicrobial resistance prevalence rates in hospital antibiograms reflect prevalence rates among pathogens associated with hospital-acquired infections

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.

Initial empirical antibiotics of non-carbapenems for ESBL-producing E. coli and K. pneumoniae bacteremia in children: a retrospective medical record review

BACKGROUND

The efficacy of non-carbapenems as an empirical antibiotic for extended-spectrum β-lactamases (ESBL)-producing Escherichia coli and Klebsiella pneumoniae bacteremia in children remains controversial. We compared clinical and microbial outcomes according to the types of empirical antibiotics for treating pediatric patients with ESBL-producing E. coli and K. pneumoniae bacteremia.

METHODS

Data from pediatric patients aged ≤ 18 years who were hospitalized with monomicrobial ESBL-producing E. coli or K. pneumoniae bacteremia at Asan Medical Center Children's Hospital, Seoul, Korea between January 2014 and May 2019 were analyzed retrospectively. The impact of empirical therapy was assessed as 30-day all-cause mortality and 2-day microbiological outcomes evaluated by the sterility of blood cultures collected on day 2 after empirical antibiotic administration. Logistic regression analysis was used to control for the effects of confounding variables.

RESULTS

A total of 53 patients with bacteremia caused by ESBL-producing E. coli (n = 29) and K. pneumoniae (n = 24) were included in this study; the median age was 3.6 years, and all had underlying comorbidities. As empirical antibiotics, 27 patients were treated with meropenem, and non-carbapenem agents were administered to 26 patients; 84.6% (22/26) were converted to carbapenem antibiotics as the definitive antibiotic by day 2 after empirical antibiotic administration. Overall, the 30-day all-cause mortality of ESBL-producing E. coli and K. pneumoniae bacteremia was 17.0% (9/53). After adjustment, there was no statistically significant association of use of a non-carbapenem agent as an empirical antibiotic with microbiological failure on day 2 and 30-day all-cause mortality [adjusted odds ratio (OR) 1.0; 95% confidence interval (CI) 0.22-4.88, and adjusted OR 0.1; 95% CI 0.01-1.56].

CONCLUSIONS

The empirical use of non-carbapenems might not be a risk factor for mortality and early microbiological outcomes in pediatric patients with ESBL-producing E. coli and K. pneumoniae BSI if early transition to appropriate antimicrobial therapy was possible.

Utilising cumulative antibiogram data to enhance antibiotic stewardship capacity in the Cape Coast Teaching Hospital, Ghana

BACKGROUND

Antimicrobial resistance (AMR) is a major public health challenge with its impact felt disproportionately in Western Sub-Saharan Africa. Routine microbiology investigations serve as a rich source of AMR monitoring and surveillance data. Geographical variations in susceptibility patterns necessitate regional and institutional tracking of resistance patterns to aid in tailored Antimicrobial Stewardship (AMS) interventions to improve antibiotic use in such settings. This study focused on developing a cumulative antibiogram of bacterial isolates from clinical samples at the Cape Coast Teaching Hospital (CCTH). This was ultimately to improve AMS by guiding empiric therapy.

METHODS

A hospital-based longitudinal study involving standard microbiological procedures was conducted from 1st January to 31st December 2020. Isolates from routine diagnostic aerobic cultures were identified by colony morphology, Gram staining, and conventional biochemical tests. Isolates were subjected to antibiotic susceptibility testing using Kirby-Bauer disc diffusion. Inhibitory zone diameters were interpreted per the Clinical and Laboratory Standards Institute guidelines and were entered and analysed on the WHONET software using the "first isolate only" principle.

RESULTS

Overall, low to moderate susceptibility was observed in most pathogen-antibiotic combinations analysed in the study. Amikacin showed the highest susceptibility (86%, n = 537/626) against all Gram-negatives with ampicillin exhibiting the lowest (6%, n = 27/480). Among the Gram-positives, the highest susceptibilities were exhibited by gentamicin (78%, n = 124/159), with clindamycin having the lowest susceptibility (27%, n = 41/154). Among the Gram-negatives, 66% (n = 426/648) of the isolates were identified phenotypically as potential extended-spectrum beta-lactamase producers. Multiple multidrug-resistant isolates were also identified among both Gram-positive and Gram-negative isolates. Low to moderate susceptibility was found against first- and second-line antibiotics recommended in the National standard treatment guidelines (NSTG). Laboratory quality management deficiencies and a turnaround time of 3.4 days were the major AMS barriers identified.

CONCLUSIONS

Low to moderate susceptibilities coupled with high rates of phenotypic resistance warrant tailoring NSTGs to fit local contexts within CCTH even after considering the biases in these results. The cumulative antibiogram proved a key AMS programme component after its communication to clinicians and subsequent monitoring of its influence on prescribing indicators. This should be adopted to enhance such programmes across the country.

Utilization of cumulative antibiograms for public health surveillance: Trends in Escherichia coli and Klebsiella pneumoniae susceptibility, Massachusetts, 2008-2018

BACKGROUND

Antimicrobial resistance is an urgent public health threat. Identifying trends in antimicrobial susceptibility can inform public health policy at the state and local levels.

OBJECTIVE

To determine the ability of statewide antibiogram aggregation for public health surveillance to identify changes in antimicrobial resistance trends.

DESIGN

Facility-level trend analysis.

METHODS

Crude and adjusted trend analyses of the susceptibility of Escherichia coli and Klebsiella pneumoniae to particular antibiotics, as reported by aggregated antibiograms, were examined from 2008 through 2018. Multivariable regression analyses via generalized linear mixed models were used to examine associations between hospital characteristics and trends of E. coli and K. pneumoniae susceptibility to ciprofloxacin and ceftriaxone.

RESULTS

E. coli and K. pneumoniae showed inverse trends in drug susceptibility over time. K. pneumoniae susceptibility to fluoroquinolones increased by 5% between 2008 and 2018 (P < .05). In contrast, E. coli susceptibility declined during the same period to ceftriaxone (6%), gentamicin (4%), and fluoroquinolones (4%) (P < .05). When compared to Boston hospitals, E. coli isolates from hospitals in other regions had a >4% higher proportion of susceptibility to ciprofloxacin and a >3% higher proportion of susceptibility to ceftriaxone (P < .05). Isolates of K. pneumoniae had higher susceptibility to ciprofloxacin (>3%) and ceftriaxone (>1.5%) in all regions when compared to Boston hospitals (P < .05).

CONCLUSIONS

Cumulative antibiograms can be used to monitor antimicrobial resistance, to discern regional and facility differences, and to detect changes in trends. Furthermore, because the number of years that hospitals contributed reports to the state-level aggregate had no significant influence on susceptibility trends, other states should not be discouraged by incomplete hospital compliance.

Recommendations for the surveillance of multidrug-resistant bacteria in Italian long-term care facilities by the GLISTer working group of the Italian Association of Clinical Microbiologists (AMCLI)

Long-term care facilities (LTCFs) are an important reservoir of multidrug-resistant organisms (MDROs). Colonization of LTCF residents by MDROs is generally higher in Italy compared to other European countries. The present review by the working group for the study of infections in LTCFs (GLISTer) of the Italian Association of Clinical Microbiologists (AMCLI) aims to propose criteria for a laboratory-based surveillance of MDROs in Italian LTCFs.

We recommend the adhesion to three levels of laboratory-based MDROs surveillance in LTCFs: i) mandatory MDRO surveillance by cumulative retrospective analysis of antimicrobial susceptibility data, obtained as part of routine care of clinical specimens. ii) strongly recommended surveillance by active rectal swab cultures or molecular screening to determine colonization with carbapenemase-producing Enterobacterales, should a resident be proven infected. iii) voluntary surveillance by prospective MDRO surveys, mainly based on point prevalence colonization studies, allowing to determine the MDROs baseline prevalence in the facility.

Laboratory-based surveillance of MDROs in LTCFs is aimed at providing useful epidemiological information to healthcare providers operating in the facility, but it is only effective if the collected data are used for infection prevention and control purposes, targeting the peculiar aspects of LTCFs.

Antimicrobial-resistant pathogens associated with adult healthcare-associated infections: Summary of data reported to the National Healthcare Safety Network, 2015-2017

OBJECTIVE

Describe common pathogens and antimicrobial resistance patterns for healthcare-associated infections (HAIs) that occurred during 2015-2017 and were reported to the Centers for Disease Control and Prevention's (CDC's) National Healthcare Safety Network (NHSN).

METHODS

Data from central line-associated bloodstream infections (CLABSIs), catheter-associated urinary tract infections (CAUTIs), ventilator-associated events (VAEs), and surgical site infections (SSIs) were reported from acute-care hospitals, long-term acute-care hospitals, and inpatient rehabilitation facilities. This analysis included device-associated HAIs reported from adult location types, and SSIs among patients ≥18 years old. Percentages of pathogens with nonsusceptibility (%NS) to selected antimicrobials were calculated for each HAI type, location type, surgical category, and surgical wound closure technique.

RESULTS

Overall, 5,626 facilities performed adult HAI surveillance during this period, most of which were general acute-care hospitals with <200 beds. Escherichia coli (18%), Staphylococcus aureus (12%), and Klebsiella spp (9%) were the 3 most frequently reported pathogens. Pathogens varied by HAI and location type, with oncology units having a distinct pathogen distribution compared to other settings. The %NS for most pathogens was significantly higher among device-associated HAIs than SSIs. In addition, pathogens from long-term acute-care hospitals had a significantly higher %NS than those from general hospital wards.

CONCLUSIONS

This report provides an updated national summary of pathogen distributions and antimicrobial resistance among select HAIs and pathogens, stratified by several factors. These data underscore the importance of tracking antimicrobial resistance, particularly in vulnerable populations such as long-term acute-care hospitals and intensive care units.

Antibiotic Prescribing in Response to Bacterial Isolates in the Intensive Care Unit

This study aimed to identify potential knowledge-performance gaps in antibiotic prescribing for bacterial isolates in the Intensive Care Unit (ICU) in order to guide the development of interventions such as antibiotic policies, decision support, and improved systems for communication between the laboratory and the bedside. A prospective observational cohort study of all patients admitted to a mixed medical/surgical ICU was undertaken over a six-month period in an Australian adult tertiary hospital. From a cohort of 524 patients, 108 had 303 isolates that were eligible for inclusion. Overall, 14.3% and 30.8% of sterile and non-sterile isolates respectively were associated with inadequate initial antibiotic therapy after identification of the bacteria. After sensitivity results were available inadequate directed therapy was observed in 4.0% and 21.3% of sterile and non-sterile isolates respectively. Problems were most commonly associated with isolates of Pseudomonas spp., Stenotrophomonas spp., Acinetobacter spp., S. aureus, enterococci and group III Enterobacteriaceae. Inadequate antibiotic therapy was found to be independently associated with prolonged length of ICU stay. Narrower spectrum antibiotic therapy was potentially available for 30% of isolates after sensitivity results were known. We conclude that there is scope to improve antibiotic prescribing in the ICU by providing clinicians with access to information regarding local susceptibility patterns and intrinsic resistance of bacteria, and spectra of antibiotic cover. Timely notification of laboratory results at the point of care may also facilitate improved prescribing performance.

Antimicrobial Resistance of Escherichia coli Urinary Isolates in the Veterans Affairs Health Care System

We reviewed data for almost 300,000 clinical Escherichia coli urinary isolates (collected in 2009 through 2013) from 127 inpatient and outpatient facilities, to assess antibiotic resistance among Veterans Affairs health care system patients using Clinical and Laboratory Standards Institute and Centers for Disease Control and Prevention National Healthcare Safety Network definitions or guidance. Rates of resistance to amoxicillin or ampicillin/β-lactamase inhibitors were approximately 40% and rates of resistance to fluoroquinolones and trimethoprim-sulfamethoxazole approached 30%. Rates of resistance to nitrofurantoin, antipseudomonal penicillin/β-lactamase inhibitors, and carbapenems remained less than 10%. The percentage of isolates that were considered multidrug resistant varied (4% to 37%), depending on the definitions used.

Clindamycin-susceptibility Rates of Methicillin-resistant Staphylococcus aureus Varies by Infection Type in Pediatric Patients

Hospital-wide antibiograms provide general susceptibility patterns. Specific antibiograms were created for methicillin-resistant Staphylococcus aureus isolates based on infection process and epidemiology. Using clinical microbiology laboratory data and patient profiles, high clindamycin resistance rates were seen for nonskin and soft tissue infections and noncommunity-associated methicillin-resistant S. aureus isolates.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Analysis and Presentation of Cumulative Antimicrobial Susceptibility Data (Antibiograms): Substantial Variability Across Medical Centers in the United States

We found substantial variability in approaches to constructing antibiograms at 65 United States medical centers. Laboratories in teaching hospitals and those with more personnel were significantly more likely to offer sophisticated antibiogram approaches, including the compiling of unit-specific susceptibility data and the reporting of temporal trends in susceptibility data.

Use of Local Community Hospital Data for Surveillance of Antimicrobial Resistance

We sought to determine whether antimicrobial susceptibility data from a nonteaching community hospital could be used to detect statistically significant local increases in resistance among Streptococcus pneumoniae over a 5-year period. Minimum inhibitory concentrations (MICs) of penicillin and ceftriaxone from 1997-1998 were compared with those from 2000-2001. MICs of penicillin and ceftriaxone for organisms collected in a nonteaching community hospital in central Illinois were used for analysis. The hospital has 224 beds and a catchment area of approximately 40 miles. There were significant increases in MICs of penicillin and ceftriaxone between 1997-1998 and 2000-2001. The MIC of penicillin increased from 0.042 to 0.121 μg/mL (P = .001; 95% confidence interval, -1.713 to -0.388), and the MIC of ceftriaxone increased from 0.028 to 0.071μg/mL (P = .005; 95% confidence interval, -1.353 to -0.188). There were no significant changes in the percentage of S. pneumoniae isolates that were resistant, intermediate, or susceptible to penicillin and ceftriaxone. MIC data from a community hospital can be used to detect local increases in the rate of resistance before antibiogram data show significant changes. This information is important for demonstrating to physicians the need to review local antibiotic use in the attempt to slow the development of resistant organisms in the community.

Relationship of various infection control interventions to the prevalence of multidrug-resistant Pseudomonas aeruginosa among U.S. hospitals

BACKGROUND

Health care-associated infections caused by antibiotic-resistant gram-negative bacteria, such as Pseudomonas aeruginosa, are an emerging and increasingly important public health threat. However, there are very few studies that examine the relationships between antimicrobial resistance strategies and interventions and the prevalence of antibiotic-resistant and multidrug-resistant strains of Pseudomonas.

METHODS

The membership of the Association for Professionals in Infection Control and Epidemiology was invited to participate in a Web-based survey of U.S. acute care hospital infection preventionists.

RESULTS

A final sample of 225 completed responses was analyzed using correlational techniques. Resistance to gentamicin (r = 0.17, P = .01), imipenem (r = 0.18, P = .02), ceftazidime (r = 0.20, P = .03), and ciprofloxacin (r = 0.15, P = .03) all showed significant direct associations with epidemiologic investigation using molecular testing. A significant inverse relationship was found between resistance to ceftazidime and effective efforts in the identification and isolation of infected patients (r = -0.18, P = .02).

CONCLUSIONS

The finding of significant direct relationships between antimicrobial resistance and epidemiologic investigations using molecular testing suggests that the increased burden of resistance is associated with molecular testing rather than the intervention driving down rates. Effective identification and isolation of infected patients appeared to be associated with lower resistance rates. Further research is needed to uncover causal relationships.

Analysis and Presentation of Cumulative Antimicrobial Susceptibility Test Data--The Influence of Different Parameters in a Routine Clinical Microbiology Laboratory

Introduction

Many clinical microbiology laboratories report on cumulative antimicrobial susceptibility testing (cAST) data on a regular basis. Criteria for generation of cAST reports, however, are often obscure and inconsistent. Whereas the CLSI has published a guideline for analysis and presentation of cAST data, national guidelines directed at clinical microbiology laboratories are not available in Europe. Thus, we sought to describe the influence of different parameters in the process of cAST data analysis in the setting of a German routine clinical microbiology laboratory during 2 consecutive years.

Material and Methods

We developed various program scripts to assess the consequences ensuing from different algorithms for calculation of cumulative antibiograms from the data collected in our clinical microbiology laboratory in 2013 and 2014.

Results

One of the most pronounced effects was caused by exclusion of screening cultures for multi-drug resistant organisms which decreased the MRSA rate in some cases to one third. Dependent on the handling of duplicate isolates, i.e. isolates of the same species recovered from successive cultures on the same patient during the time period analyzed, we recorded differences in resistance rates of up to 5 percentage points for S. aureus, E. coli and K. pneumoniae and up to 10 percentage points for P. aeruginosa. Stratification by site of care and specimen type, testing of antimicrobials selectively on resistant isolates, change of interpretation rules and analysis at genus level instead of species level resulted in further changes of calculated antimicrobial resistance rates.

Conclusion

The choice of parameters for cAST data analysis may have a substantial influence on calculated antimicrobial resistance rates. Consequently, comparability of cAST reports from different clinical microbiology laboratories may be limited. We suggest that laboratories communicate the strategy used for cAST data analysis as long as national guidelines for standardized cAST data analysis and reporting do not exist in Europe.

Making a Case for Pediatric Antimicrobial Stewardship Programs

Although antimicrobials are commonly used in children, it is important to remember that they can have a profound impact on this unique patient population. Inadvertent consequences of antiinfective use in children include antimicrobial resistance, infection caused by Clostridium difficile, increased risk of obesity, and adverse drug events. In addition, compared with adults, children have different dosing requirements, antimicrobial formulation needs, pharmacokinetics, and antimicrobial susceptibility profiles. Therefore, pediatric-specific antimicrobial stewardship efforts are needed to promote appropriate use of antimicrobials in children. The primary purposes of this review article are to provide a rationale behind pediatric-focused antimicrobial stewardship and to describe currently available evidence regarding the initiatives of pediatric antimicrobial stewardship programs (ASPs). A literature search of the Medline database was performed (from inception through March 2015). The studies included in this review focus on antimicrobial stewardship interventions in inpatient pediatric settings. Ten inpatient studies involving pediatric-focused antimicrobial stewardship interventions were identified from the published literature. Four studies used the core strategy of prospective audit with feedback; two used prior approval. The remaining four used supplemental antimicrobial stewardship strategies (guidelines, clinical pathways, and computerized decision support tools). In general, the interventions resulted in decreased antimicrobial use, reduced antimicrobial costs, and fewer prescribing errors. Children have unique medical needs related to antimicrobials and deserve focused ASP efforts. The literature regarding pediatric antimicrobial stewardship interventions is limited, but published interventions may serve as paradigms for developing pediatric ASPs as demonstrated by the general success of these interventions.

Pediatric Antimicrobial Susceptibility Trends across the United States

Objective.

Antimicrobial susceptibility patterns across US pediatric healthcare institutions are unknown. A national pooled pediatric antibiogram (1) identifies nationwide trends in antimicrobial resistance, (2) allows across-hospital benchmarking, and (3) provides guidance for empirical antimicrobial regimens for institutions unable to generate pediatric antibiograms.

Methods.

In January 2012, a request for submission of pediatric antibiograms between 2005 and 2011 was sent to 233 US hospitals. A summary antibiogram was compiled from participating institutions to generate proportions of antimicrobial susceptibility. Temporal and regional comparisons were evaluated using χ² tests and logistic regression, respectively.

Results.

Of 200 institutions (85%) responding to our survey, 78 (39%) reported generating pediatric antibiograms, and 55 (71%) submitted antibiograms. Carbapenems had the highest activity against the majority of gram-negative organisms tested, but no antibiotic had more than 90% activity against Pseudomonas aeruginosa. Approximately 50% of all Staphylococcus aureus isolates were methicillin resistant. Western hospitals had significantly lower proportions of S. aureus that were methicillin resistant compared with all other regions tested. Overall, 21% of S. aureus isolates had resistance to clindamycin. Among Enterococcus faecium isolates, the prevalence of susceptibility to ampicillin (25%) and vancomycin (45%) was low but improved over time (P < .01), and 8% of E. faecium isolates were resistant to linezolid. Southern hospitals reported significantly higher prevalence of E. faecium with susceptibilities to ampicillin, vancomycin, and linezolid compared with the other 3 regions (P < .01).

Conclusions.

A pooled, pediatric antibiogram can identify nationwide antimicrobial resistance patterns for common pathogens and might serve as a useful tool for benchmarking resistance and informing national prescribing guidelines for children.

Recommendations For Metrics For Multidrug-Resistant Organisms In Healthcare Settings: SHEA/HICPAC Position Paper

Monitoring multidrug-resistant organisms (MDROs) and the infections they cause in a healthcare setting is important to detect newly emerging antimicrobial resistance profiles, to identify vulnerable patient populations, and to assess the need for and effectiveness of interventions; however, it is unclear which metrics are the best, because most of the metrics are not standardized. This document describes useful and practical metrics and surveillance considerations for measuring MDROs and the infections they cause in the practice of infection prevention and control in healthcare settings. These metrics are designed to aid healthcare workers in documenting trends over time within their facility and should not be used for interfacility comparison.

Prevalence and antibiogram profiling of Escherichia coli pathotypes isolated from the Kat River and the Fort Beaufort abstraction water

Escherichia coli is a widespread bacterium encompassing a variety of strains, ranging from highly pathogenic strains, causing worldwide outbreaks of severe diseases to avirulent, well characterized safe laboratory strains. This study evaluated the prevalence and antibiogram profiles of E. coli pathotypes isolated from the Kat River and Fort Beaufort abstraction water. A total of 171 out of 278 confirmed E. coli isolates were positive for at least one pathogenic determinant and these included enteropathogenic E. coli (6%), enterotoxigenic E. coli (47%), uropathogenic E. coli (2%), neonatal meningitis E. coli (5%), diffusely adherent E. coli (1%) and enterohaemorrhagic E. coli (1%). Interestingly, enteroinvasive and enteroaggregative E. coli were not detected. The phenotypic antibiogram profiles of the isolates revealed that all were resistant to penicillin G, while 98% and 38% of the pathotypes were resistant to ampicillin and trimethoprim-sulphamethoxazole, respectively. About 8% of the isolates were resistant to streptomycin. More than half of the isolates exhibited multiple antibiotic resistance with 44% being resistant to three antibiotics and 8% resistant to four antibiotics. We conclude that the Kat River is a reservoir of potentially virulent antibiotic resistant E. coli strains that can cause serious health risks to humans who drink raw water from this river, or in the case that consumption of treated drinking water coincides with failed drinking water processes.

Comparison of Hospitalwide and Custom Antibiograms for Clinical Isolates of Pseudomonas aeruginosa

BACKGROUND

Hospital antibiograms, which are commonly used to determine empiric antibiotic therapy and as a tool in stewardship in a given institution, are open to bias when combining susceptibility results from various sources, hospital locations, and patient groups.

METHODS

We assessed such differences, using Pseudomonas aeruginosa as a test case, with susceptibility data from 2008 through 2010 in our institution. Each year's data were analyzed separately. A variety of specific or subcategorical antibiograms were compared with each other as well as with versions including all tested isolates and those with results from inpatients and outpatients only. Statistical significance was determined at the .01 level using either chi-square or Fisher exact test, and clinical significance was defined as ≥10 percentage points.

RESULTS

A variety of clinically significant differences were found that illustrated important differences within the intensive care unit environment and based on population, specifically adult versus pediatric. Concordance between statistically significant and clinically significant differences was poor.

CONCLUSION

These results corroborate and extend previous similar observations and point to the potential importance of subanalyses in preparing the annual hospital antibiogram.

Comparison of Hospitalwide and Custom Antibiograms for Clinical Isolates of Pseudomonas aeruginosa

BACKGROUND

Hospital antibiograms, which are commonly used to determine empiric antibiotic therapy and as a tool in stewardship in a given institution, are open to bias when combining susceptibility results from various sources, hospital locations, and patient groups.

METHODS

We assessed such differences, using Pseudomonas aeruginosa as a test case, with susceptibility data from 2008 through 2010 in our institution. Each year's data were analyzed separately. A variety of specific or subcategorical antibiograms were compared with each other as well as with versions including all tested isolates and those with results from inpatients and outpatients only. Statistical significance was determined at the .01 level using either chi-square or Fisher exact test, and clinical significance was defined as ≥10 percentage points.

RESULTS

A variety of clinically significant differences were found that illustrated important differences within the intensive care unit environment and based on population, specifically adult versus pediatric. Concordance between statistically significant and clinically significant differences was poor.

CONCLUSION

These results corroborate and extend previous similar observations and point to the potential importance of subanalyses in preparing the annual hospital antibiogram.

Incidence of methicillin-resistant Staphylococcus aureus infection in a children's hospital in the Washington metropolitan area of the United States, 2003 - 2010

Methicillin-resistant Staphylococcus aureus (MRSA) has emerged as a major public health threat. In this retrospective cohort study, we included patients with laboratory-confirmed MRSA infections treated at Children's National Medical Center in Washington, District of Columbia between July 2003 and December 2010. The secular trends in the incidence rates of skin/soft tissue and invasive MRSA infections were assessed. Molecular analyses were performed on a subset of patients with invasive infections whose MRSA isolates were available for genotyping. The study identified 3750 patients with MRSA infections. The incidence of MRSA infections peaked in 2007 (incidence rate: 5.34 per 1000 patient-visits) and subsequently declined at a rate of 5% per year. By December 2010, the MRSA incidence rate reached 3.77 per 1000 patient-visits. Seventeen (14.7%) patients with invasive MRSA infections died, and the mortality risk significantly increased if the MRSA infections were healthcare-associated (HA) or if an isolate was resistant to clindamycin and/or trimethoprim/sulfamethoxazole. In conclusion, this study described a descending trend in MRSA infections in children since 2007. Although invasive MRSA infections only accounted for a small portion of the total MRSA infections, they were associated with a high mortality risk. The prevention and control of the spread of MRSA remains a crucial and challenging task.

Resistance trends in gram-negative bacteria: surveillance results from two Mexican hospitals, 2005-2010

BACKGROUND

Hospital-acquired infections caused by multiresistant gram-negative bacteria are difficult to treat and cause high rates of morbidity and mortality. The analysis of antimicrobial resistance trends of gram-negative pathogens isolated from hospital-acquired infections is important for the development of antimicrobial stewardship programs. The information obtained from antimicrobial resistant programs from two hospitals from Mexico will be helpful in the selection of empiric therapy for hospital-acquired gram-negative infections.

FINDINGS

Two thousand one hundred thirty two gram-negative bacteria collected between January 2005 and December 2010 from hospital-acquired infections occurring in two teaching hospitals in Mexico were evaluated. Escherichia coli was the most frequently isolated gram-negative bacteria, with >50% of strains resistant to ciprofloxacin and levofloxacin. Klebsiella spp. showed resistance rates similar to Escherichia coli for ceftazidime (33.1% vs 33.2%), but exhibited lower rates for levofloxacin (18.2% vs 56%). Of the samples collected for the third most common gram-negative bacteria, Pseudomonas aeruginosa, >12.8% were resistant to the carbapenems, imipenem and meropenem. The highest overall resistance was found in Acinetobacter spp. Enterobacter spp. showed high susceptibility to carbapenems.

CONCLUSIONS

E. coli was the most common nosocomial gram-negative bacilli isolated in this study and was found to have the second-highest resistance to fluoroquinolones (>57.9%, after Acinetobacter spp. 81.2%). This finding represents a disturbing development in a common nosocomial and community pathogen.

Trends in aminoglycoside use and gentamicin-resistant gram-negative clinical isolates in US academic medical centers: implications for antimicrobial stewardship

OBJECTIVE

To measure trends in aminoglycoside antibiotic use and gentamicin-resistant clinical isolates across a network of hospitals and compare network-level relationships with those of individual hospitals.

DESIGN

Longitudinal observational investigation.

SETTING

US academic medical centers.

PARTICIPANTS

Adult inpatients.

METHODS

Adult aminoglycoside use was measured from 2002 or 2003 through 2009 in 29 hospitals. Hospital-wide antibiograms assessed gentamicin resistance by proportions and incidence rates for Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. Mixed-effects analysis of variance was used to assess the significance of changes in aminoglycoside use and changes in resistance rates and proportions. Generalized estimating equations were used to assess the relationship between aminoglycoside use and resistance.

RESULTS

Mean aminoglycoside use declined by 41%, reflecting reduced gentamicin (P < .0001) and tobramycin (P < .005) use; amikacin use did not change. The rate and proportion of gentamicin-resistant P. aeruginosa decreased by 48% (P < .0001) and 31% (P < .0001), respectively. The rate and proportion of gentamicin-resistant E. coli increased by 166% and 124%, respectively (P < .0001), and they were related to increasing quinolone resistance in E. coli. Resistance among K. pneumoniae and A. baumannii did not change. Relationships between aminoglycoside use and resistance at the network level were highly variable at the individual hospital level.

CONCLUSIONS

Mean aminoglycoside use declined in this network of US hospitals and was associated with significant and opposite changes in rates of resistance for some organisms and no change for others. At the individual hospital level, antibiograms appear to be an unreliable reflection of antibiotic use, at least for aminoglycosides.

Increasing role of Staphylococcus aureus and community-acquired methicillin-resistant Staphylococcus aureus infections in the United States: a 10-year trend of replacement and expansion

BACKGROUND

There is the need to properly characterize the temporal trend of U.S. Staphylococcus aureus infections, including methicillin-resistant S. aureus (MRSA) and community-acquired (CA) MRSA in inpatient and outpatient settings.

METHODS

The study used the Surveillance Network(®) surveillance database (Eurofins Medinet) and the National Hospitalization Discharge Survey for the period 1998-2007. CA-MRSA phenotype was defined by a resistance profile that includes susceptibility to gentamicin and cotrimoxazole, and coresistance to ciprofloxacin/clindamycin. Adjusted rates, rate ratios, and 95% confidence intervals (CIs) were computed using multivariate logistic regression.

RESULTS

The study consisted of 1,761,991 S. aureus isolates. Annual MRSA prevalence continuously increased over the 10-year period from 32.7% in 1998 to 53.8% in 2007 (odds ratio 2.4, 95% CI 2.3-2.5). CA-MRSA replaced competing strains by increasing its share of MRSA from 22.3% in 1998 to 66.1% in 2007 (odds ratio 6.7, 95% CI 6.5-6.9). MRSA-related hospitalization rate per 1,000 discharges doubled from 3.5 ± 0.9 in 1998 to 7.6 ± 1.5 in 2007 (RR 2.2, 95% CI 1.8-3.1), whereas CA-MRSA increased from 0.4 ± 0.14 hospitalizations per 1,000 discharges in 1998 to 3.1 ± 0.5 in 2007 (RR 8.1, 95% CI 5.2-14.1), By 2007, 81.5% of all MRSA isolates were categorized as CA-MRSA among children, whereas CA-MRSA represented 48.9% of MRSA isolates from the elderly.

CONCLUSION

MRSA not only replaced methicillin susceptible S. aureus (MSSA) isolates as a percentage of all S. aureus isolates, but its hospitalization rates increased over and above the replacement process. This trend also applies to CA-MRSA over hospital-acquired (HA) MRSA.

Prevalence of antimicrobial-resistant pathogens in Canadian hospitals: results of the Canadian Ward Surveillance Study (CANWARD 2008)

A total of 5,282 bacterial isolates obtained between 1 January and 31 December 31 2008, inclusive, from patients in 10 hospitals across Canada as part of the Canadian Ward Surveillance Study (CANWARD 2008) underwent susceptibility testing. The 10 most common organisms, representing 78.8% of all clinical specimens, were as follows: Escherichia coli (21.4%), methicillin-susceptible Staphylococcus aureus (MSSA; 13.9%), Streptococcus pneumoniae (10.3%), Pseudomonas aeruginosa (7.1%), Klebsiella pneumoniae (6.0%), coagulase-negative staphylococci/Staphylococcus epidermidis (5.4%), methicillin-resistant S. aureus (MRSA; 5.1%), Haemophilus influenzae (4.1%), Enterococcus spp. (3.3%), Enterobacter cloacae (2.2%). MRSA comprised 27.0% (272/1,007) of all S. aureus isolates (genotypically, 68.8% of MRSA were health care associated [HA-MRSA] and 27.6% were community associated [CA-MRSA]). Extended-spectrum β-lactamase (ESBL)-producing E. coli occurred in 4.9% of E. coli isolates. The CTX-M type was the predominant ESBL, with CTX-M-15 the most prevalent genotype. MRSA demonstrated no resistance to ceftobiprole, daptomycin, linezolid, telavancin, tigecycline, or vancomycin (0.4% intermediate intermediate resistance). E. coli demonstrated no resistance to ertapenem, meropenem, or tigecycline. Resistance rates with P. aeruginosa were as follows: colistin (polymyxin E), 0.8%; amikacin, 3.5%; cefepime, 7.2%; gentamicin, 12.3%; fluoroquinolones, 19.0 to 24.1%; meropenem, 5.6%; piperacillin-tazobactam, 8.0%. A multidrug-resistant (MDR) phenotype occurred frequently in P. aeruginosa (5.9%) but uncommonly in E. coli (1.2%) and K. pneumoniae (0.9%). In conclusion, E. coli, S. aureus (MSSA and MRSA), P. aeruginosa, S. pneumoniae, K. pneumoniae, H. influenzae, and Enterococcus spp. are the most common isolates recovered from clinical specimens in Canadian hospitals. The prevalence of MRSA was 27.0% (of which genotypically 27.6% were CA-MRSA), while ESBL-producing E. coli occurred in 4.9% of isolates. An MDR phenotype was common in P. aeruginosa.

Real-time validation and presentation of the cumulative antibiogram and implications of presenting a standard format using a novel in-house software: ABSOFT

BACKGROUND

Antibiograms must use a standard format to present microbiologic data.

OBJECTIVE

When antibacterials are selected for the treatment of infections, knowledge of the locally most likely causative organisms and the prevalence of resistant pathogens to antibacterial agents are essential. This involves generating a cumulative antibiogram. We designed an in-house novel software to prepare our antibiogram, validate data, and analyze results and assessed the performance of this technology. It should be noted that analysis of specific antibiotic resistance patterns were not a focus of this study.

SETTING

The study was conducted at Al Khor Hospital, Hamad Medical Corporation, a 110-bed acute care hospital that serves patients in the northern area of Qatar. Positive microbiology cultures excluding surveillance samples, isolated in the microbiology laboratory from January 2008 to December 2008, were entered into an in-house software, ABSOFT, designed by one of the authors.

RESULTS

The software produced the antibiogram in a fixed format. Epidemiologic data and comparison of our data to the National Nosocomial Infection Surveillance benchmark for multidrug-resistant organism distribution were also presented real time. Automatic color-coded results in tabular format were printed instantaneously without errors, thus eliminating the need to be reviewed.

CONCLUSION

The paper highlights real-time validation and presentation of the cumulative antibiogram, additionally suggesting the format for reporting using a novel in-house software ABSOFT. This technology provided us an accurate, simple, cost-effective solution to present validated data real-time in a transparent and consistent manner. To our knowledge to date, no uniform format has been recommended for the presentation of cumulative antibiograms.

Antimicrobial susceptibility testing using high surface-to-volume ratio microchannels

This study reports the use of microfluidics, which intrinsically has a large surface-to-volume ratio, toward rapid antimicrobial susceptibility testing at the point of care. By observing the growth of uropathogenic Escherichia coli in gas permeable polymeric microchannels with different dimensions, we demonstrate that the large surface-to-volume ratio of microfluidic systems facilitates rapid growth of bacteria. For microchannels with 250 microm or less in depth, the effective oxygenation can sustain the growth of E. coli to over 10(9) cfu/mL without external agitation or oxygenation, which eliminates the requirement of bulky instrumentation and facilitates rapid bacterial growth for antimicrobial susceptibility testing at the point of care. The applicability of microfluidic rapid antimicrobial susceptibility testing is demonstrated in culture media and in urine with clinical bacterial isolates that have different antimicrobial resistance profiles. The antimicrobial resistance pattern can be determined as rapidly as 2 h compared to days in standard clinical procedures facilitating diagnostics at the point of care.

Rapid universal identification of bacterial pathogens from clinical cultures by using a novel sloppy molecular beacon melting temperature signature technique

A real-time PCR assay with the ability to rapidly identify all pathogenic bacteria would have widespread medical utility. Current real-time PCR technologies cannot accomplish this task due to severe limitations in multiplexing ability. To this end, we developed a new assay system which supports very high degrees of multiplexing. We developed a new class of mismatch-tolerant "sloppy" molecular beacons, modified them to provide an extended hybridization range, and developed a multiprobe, multimelting temperature (T(m)) signature approach to bacterial species identification. Sloppy molecular beacons were exceptionally versatile, and they were able to generate specific T(m) values for DNA sequences that differed by as little as one nucleotide to as many as 23 polymorphisms. Combining the T(m) values generated by several probe-target hybrids resulted in T(m) signatures that served as highly accurate sequence identifiers. Using this method, PCR assays with as few as six sloppy molecular beacons targeting bacterial 16S rRNA gene segments could reproducibly classify 119 different sequence types of pathogenic and commensal bacteria, representing 64 genera, into 111 T(m) signature types. Blinded studies using the assay to identify the bacteria present in 270 patient-derived clinical cultures including 106 patient blood cultures showed a 95 to 97% concordance with conventional methods. Importantly, no bacteria were misidentified; rather, the few species that could not be identified were classified as "indeterminate," resulting in an assay specificity of 100%. This approach enables highly multiplexed target detection using a simple PCR format that can transform infectious disease diagnostics and improve patient outcomes.

Impact of an antimicrobial utilization program on antimicrobial use at a large teaching hospital: a randomized controlled trial

BACKGROUND

Multidisciplinary antimicrobial utilization teams (AUTs) have been proposed as a mechanism for improving antimicrobial use, but data on their efficacy remain limited.

OBJECTIVE

To determine the impact of an AUT on antimicrobial use at a teaching hospital.

DESIGN

Randomized controlled intervention trial.

SETTING

A 953-bed, public, university-affiliated, urban teaching hospital.

PATIENTS

Patients who were given selected antimicrobial agents (piperacillin-tazobactam, levofloxacin, or vancomycin) by internal medicine ward teams.

INTERVENTION

Twelve internal medicine teams were randomly assigned monthly: 6 teams to an intervention group (academic detailing by the AUT) and 6 teams to a control group that was given indication-based guidelines for prescription of broad-spectrum antimicrobials (standard of care), during a 10-month study period.

MEASUREMENTS

Proportion of appropriate empirical, definitive (therapeutic), and end (overall) antimicrobial usage.

RESULTS

A total of 784 new prescriptions of piperacillin-tazobactam, levofloxacin, and vancomycin were reviewed. The proportion of antimicrobial prescriptions written by the intervention teams that was considered to be appropriate was significantly higher than the proportion of antimicrobial prescriptions written by the control teams that was considered to be appropriate: 82% versus 73% for empirical (risk ratio [RR], 1.14; 95% confidence interval [CI], 1.04-1.24), 82% versus 43% for definitive (RR, 1.89; 95% CI, 1.53-2.33), and 94% versus 70% for end antimicrobial usage (RR, 1.34; 95% CI, 1.25-1.43). In multivariate analysis, teams that received feedback from the AUT alone (adjusted RR, 1.37; 95% CI, 1.27-1.48) or from both the AUT and the infectious diseases consultation service (adjusted RR, 2.28; 95% CI, 1.64-3.19) were significantly more likely to prescribe end antimicrobial usage appropriately, compared with control teams.

CONCLUSIONS

A multidisciplinary AUT that provides feedback to prescribing physicians was an effective method in improving antimicrobial use. Trial registration. ClinicalTrials.gov identifier: NCT00552838.

The evolution of drug-resistant microorganisms in patients with prolonged mechanical ventilation

BACKGROUND

Patients requiring prolonged mechanical ventilation (PMV) tend to become reservoirs of antimicrobial resistance. We assessed antimicrobial-resistant microorganisms in the respiratory tracts of patients receiving PMV.

METHODS

Over a 6-month period, the microorganisms from tracheal aspirates of PMV patients with lower airway infection were analyzed.

RESULTS

Antimicrobial use was greatest during the acute critical stage of respiratory failure. Antimicrobial resistance in Pseudomonas aeruginosa and Klebsiella pneumoniae peaked during the fourth to 15th weeks of PMV. Methicillin-resistant Staphylococcus aureus (MRSA) developed rapidly during the first 3 weeks of PMV. The acquisition of multidrug-resistant P aeruginosa and MRSA were significantly correlated with previous exposure to ceftazidime (odds ratio [OR] = 121.3 and 72.5; P = .01 and .01, respectively). The rise of multidrug-resistant Acinetobacter baumannii was significantly correlated with previous exposure to piperacillin/tazobactam (OR = 26.81; P = .02) and imipenem (OR = 16.91; P = .03). Using univariate and multivariate logistic regression models, the lower respiratory tract infections with multidrug-resistant microorganisms were independently associated with increased 6-month mortality (OR = 3.41; P < .01).

CONCLUSION

In patients receiving PMV, lower respiratory tract infection with multidrug-resistant microorganisms is common and is associated with higher mortality.

Detecting bacteria and determining their susceptibility to antibiotics by stochastic confinement in nanoliter droplets using plug-based microfluidics

This article describes plug-based microfluidic technology that enables rapid detection and drug susceptibility screening of bacteria in samples, including complex biological matrices, without pre-incubation. Unlike conventional bacterial culture and detection methods, which rely on incubation of a sample to increase the concentration of bacteria to detectable levels, this method confines individual bacteria into droplets nanoliters in volume. When single cells are confined into plugs of small volume such that the loading is less than one bacterium per plug, the detection time is proportional to plug volume. Confinement increases cell density and allows released molecules to accumulate around the cell, eliminating the pre-incubation step and reducing the time required to detect the bacteria. We refer to this approach as 'stochastic confinement'. Using the microfluidic hybrid method, this technology was used to determine the antibiogram - or chart of antibiotic sensitivity - of methicillin-resistant Staphylococcus aureus (MRSA) to many antibiotics in a single experiment and to measure the minimal inhibitory concentration (MIC) of the drug cefoxitin (CFX) against this strain. In addition, this technology was used to distinguish between sensitive and resistant strains of S. aureus in samples of human blood plasma. High-throughput microfluidic techniques combined with single-cell measurements also enable multiple tests to be performed simultaneously on a single sample containing bacteria. This technology may provide a method of rapid and effective patient-specific treatment of bacterial infections and could be extended to a variety of applications that require multiple functional tests of bacterial samples on reduced timescales.

Antimicrobial-resistant pathogens in intensive care units in Canada: results of the Canadian National Intensive Care Unit (CAN-ICU) study, 2005-2006

Between 1 September 2005 and 30 June 2006, 19 medical centers collected 4,180 isolates recovered from clinical specimens from patients in intensive care units (ICUs) in Canada. The 4,180 isolates were collected from 2,292 respiratory specimens (54.8%), 738 blood specimens (17.7%), 581 wound/tissue specimens (13.9%), and 569 urinary specimens (13.6%). The 10 most common organisms isolated from 79.5% of all clinical specimens were methicillin-susceptible Staphylococcus aureus (MSSA) (16.4%), Escherichia coli (12.8%), Pseudomonas aeruginosa (10.0%), Haemophilus influenzae (7.9%), coagulase-negative staphylococci/Staphylococcus epidermidis (6.5%), Enterococcus spp. (6.1%), Streptococcus pneumoniae (5.8%), Klebsiella pneumoniae (5.8%), methicillin-resistant Staphylococcus aureus (MRSA) (4.7%), and Enterobacter cloacae (3.9%). MRSA made up 22.3% (197/884) of all S. aureus isolates (90.9% of MRSA were health care-associated MRSA, and 9.1% were community-associated MRSA), while vancomycin-resistant enterococci (VRE) made up 6.7% (11/255) of all enterococcal isolates (88.2% of VRE had the vanA genotype). Extended-spectrum beta-lactamase (ESBL)-producing E. coli and K. pneumoniae occurred in 3.5% (19/536) and 1.8% (4/224) of isolates, respectively. All 19 ESBL-producing E. coli isolates were PCR positive for CTX-M, with bla CTX-M-15 occurring in 74% (14/19) of isolates. For MRSA, no resistance against daptomycin, linezolid, tigecycline, and vancomycin was observed, while the resistance rates to other agents were as follows: clarithromycin, 89.9%; clindamycin, 76.1%; fluoroquinolones, 90.1 to 91.8%; and trimethoprim-sulfamethoxazole, 11.7%. For E. coli, no resistance to amikacin, meropenem, and tigecycline was observed, while resistance rates to other agents were as follows: cefazolin, 20.1%; cefepime, 0.7%; ceftriaxone, 3.7%; gentamicin, 3.0%; fluoroquinolones, 21.1%; piperacillin-tazobactam, 1.9%; and trimethoprim-sulfamethoxazole, 24.8%. Resistance rates for P. aeruginosa were as follows: amikacin, 2.6%; cefepime, 10.2%; gentamicin, 15.2%; fluoroquinolones, 23.8 to 25.5%; meropenem, 13.6%; and piperacillin-tazobactam, 9.3%. A multidrug-resistant (MDR) phenotype (resistance to three or more of the following drugs: cefepime, piperacillin-tazobactam, meropenem, amikacin or gentamicin, and ciprofloxacin) occurred frequently in P. aeruginosa (12.6%) but uncommonly in E. coli (0.2%), E. cloacae (0.6%), or K. pneumoniae (0%). In conclusion, S. aureus (MSSA and MRSA), E. coli, P. aeruginosa, H. influenzae, Enterococcus spp., S. pneumoniae, and K. pneumoniae are the most common isolates recovered from clinical specimens in Canadian ICUs. A MDR phenotype is common for P. aeruginosa isolates in Canadian ICUs.

Increased fluoroquinolone resistance with time in Escherichia coli from >17,000 patients at a large county hospital as a function of culture site, age, sex, and location

Background

Escherichia coli infections are common and often treated with fluoroquinolones. Fluoroquinolone resistance is of worldwide importance and is monitored by national and international surveillance networks. In this study, we analyzed the effects of time, culture site, and patient age, sex, and location on fluoroquinolone resistance in E. coli clinical isolates.

Methods

To understand how patient factors and time influenced fluoroquinolone resistance and to determine how well data from surveillance networks predict trends at Ben Taub General Hospital in Houston, TX, we used Perl to parse and MySQL to house data from antibiograms (n ≅ 21,000) for E. coli isolated between 1999 to 2004 using Chi Square, Bonferroni, and Multiple Linear Regression methods.

Results

Fluoroquinolone resistance (i) increased with time; (ii) exceeded national averages by 2- to 4-fold; (iii) was higher in males than females, largely because of urinary isolates from male outpatients; (iv) increased with patient age; (v) was 3% in pediatric patients; (vi) was higher in hospitalized patients than outpatients; (vii) was higher in sputum samples, particularly from inpatients, than all other culture sites, including blood and urine, regardless of patient location; and (viii) was lowest in genital isolates than all other culture sites. Additionally, the data suggest that, with regard to susceptibility or resistance by the Dade Behring MicroScan system, a single fluoroquinolone suffices as a "surrogate marker" for all of the fluoroquinolone tested.

Conclusion

Large surveillance programs often did not predict E. coli fluoroquinolone resistance trends at a large, urban hospital with a largely indigent, ethnically diverse patient population or its affiliated community clinics.

The utility of hospital antibiograms as tools for guiding empiric therapy and tracking resistance. Insights from the Society of Infectious Diseases Pharmacists

Hospital antibiograms are commonly used to help guide empiric antimicrobial treatment and are an important component of detecting and monitoring trends in antimicrobial resistance. To serve these purposes, antibiograms must be constructed using standardized methods that allow inter- and intrahospital comparisons. Antibiograms that include surveillance cultures and duplicate bacterial isolates can overestimate rates of resistance. In 2002, the National Committee for Clinical Laboratory Standards (now known as the Clinical and Laboratory Standards Institute [CLSI]) published standards for constructing antibiograms. According to national surveys, many of the recommended elements of the CLSI document have not been fully adopted. In lieu of full compliance with CLSI standards, it is necessary that the methods used to construct antibiograms are clearly delineated. Antibiograms have several limitations, such as their inability to track emergence of resistance during therapy. The antibiogram can serve as a valuable tool in guiding antimicrobial therapy, but other patient factors, such as previous infection history and antibiotic use, also need to be considered. Additional data are needed for specialized applications of resistance analyses.

Activity of meropenem as serine carbapenemases evolve in US Medical Centers: monitoring report from the MYSTIC Program (2006)

The Meropenem Yearly Susceptibility Test Information Collection (MYSTIC) Surveillance Program was designed to monitor the antimicrobial potency and spectrum of meropenem, and selected broad-spectrum comparison agents against pathogens from hospitalized patients. In the 2006 (year 8 of the study) United States sample, a total of 2841 isolates (94.7% compliance) including 641 Escherichia coli, 619 Klebsiella spp., 606 Pseudomonas aeruginosa, 456 oxacillin-susceptible Staphylococcus aureus, 300 streptococci, 149 Enterococcus faecalis, and 70 Gram-positive anaerobic organisms were tested by reference broth microdilution or agar dilution susceptibility methods. The carbapenems, especially meropenem, consistently demonstrated the lowest resistance rates against Enterobacteriaceae strains, and the fluoroquinolones had the highest and increasing resistance rates. The presence of qnr-mediated fluoroquinolone resistance was investigated using polymerase chain reaction methods but was only observed at very low levels (2.1%) and was not clonally associated. Confirmed extended-spectrum beta-lactamase rates for E. coli and Klebsiella spp. were only 4.8% and 5.0%, respectively, with mobile AmpC (CMY-2 and FOX-5) enzymes shown in 13 additional Enterobacteriaceae isolates. Clonally related KPC-type serine carbapenemase production (57 strains, 9.5%) was observed at a rate 2-fold greater than the prior year among Klebsiella spp. isolates, primarily from 1 geographic region (Middle Atlantic States). These MYSTIC Program (2006) results demonstrate the continued need to monitor the carbapenem class potency and spectrum of activity against Enterobacteriaceae as well as P. aeruginosa because of the documented presence of serine carbapenemases and rare incidence of metallo-beta-lactamases that may further compromise their activity and that of other beta-lactam agents.

Development and validation of measures to assess prevention and control of AMR in hospitals

BACKGROUND

The rapid spread of antimicrobial resistance (AMR) in the US hospitals poses serious quality and safety problems. Expert panels, identifying strategies for optimizing antibiotic use and preventing AMR spread, have recommended hospitals undertake efforts to implement specific evidence-based practices.

OBJECTIVE

To develop and validate a measurement scale for assessing hospitals' efforts to implement recommended AMR prevention and control measures.

STUDY DESIGN

Surveys were mailed to infection control professionals in a national sample of 670 US hospitals stratified by geographic region, bedsize, teaching status, and VA affiliation.

SUBJECTS

: Four hundred forty-eight infection control professionals participated (67% response rate).

METHODS

Survey items measured implementation of guideline recommendations, practices for AMR monitoring and feedback, AMR-related outcomes (methicillin-resistant Staphylococcus aureus prevalence and outbreaks [MRSA]), and organizational features. "Derivation" and "validation" samples were randomly selected. Exploratory factor analysis was performed to identify factors underlying AMR prevention and control efforts. Multiple methods were used for validation.

RESULTS

We identified 4 empirically distinct factors in AMR prevention and control: (1) practices for antimicrobial prescription/use, (2) information/resources for AMR control, (3) practices for isolating infected patients, and (4) organizational support for infection control policies. The Prevention and Control of Antimicrobial Resistance scale was reliable and had content and construct validity. MRSA prevalence was significantly lower in hospitals with higher resource/information availability and broader organizational support.

CONCLUSIONS

The Prevention and Control of Antimicrobial Resistance scale offers a simple yet discriminating assessment of AMR prevention and control efforts. Use should complement assessment methods based exclusively on AMR outcomes.

Emergence and resurgence of meticillin-resistant Staphylococcus aureus as a public-health threat

Staphylococcus aureus is a gram-positive bacterium that colonises the skin and is present in the anterior nares in about 25-30% of healthy people. Dependent on its intrinsic virulence or the ability of the host to contain its opportunistic behaviour, S aureus can cause a range of diseases in man. The bacterium readily acquires resistance against all classes of antibiotics by one of two distinct mechanisms: mutation of an existing bacterial gene or horizontal transfer of a resistance gene from another bacterium. Several mobile genetic elements carrying exogenous antibiotic resistance genes might mediate resistance acquisition. Of all the resistance traits S aureus has acquired since the introduction of antimicrobial chemotherapy in the 1930s, meticillin resistance is clinically the most important, since a single genetic element confers resistance to the most commonly prescribed class of antimicrobials--the beta-lactam antibiotics, which include penicillins, cephalosporins, and carbapenems.