Differences in antimicrobial susceptibility among hospitals in an integrated health system

Pediatric bloodstream infections in metropolitan Australia

BACKGROUND

Bloodstream infections (BSIs) cause significant morbidity and mortality of children worldwide. The aim of this study was to investigate BSI in children and determine the identity of causative organism and their susceptibility patterns in a metropolitan public hospital in Australia.

METHODS

We retrospectively reviewed children aged 0-16 years admitted to a public hospital from January 1, 2010 to August 31, 2014 inclusive, and whose blood cultures revealed bacteraemia. Data were collected regarding patient demographics, species of bacteria isolated, antimicrobial susceptibility of these isolates, and clinical outcomes.

RESULTS

Out of 96 patients with BSI, 55 (57.3%) were males. The median age was 3.35 years (IQR 0.44-7.46), and there were 2 mortalities. Common sites of infection were the respiratory tract (16.6%, n = 16), bone and joints (15.6%, n = 15) and the urinary tract (11.5%, n = 11). The most frequent isolates were Staphylococcus aureus (27.0%), Escherichia coli (14.0%) and Streptococcus pneumoniae (12.0%). Whilst most bacterial isolates displayed susceptibility (> 90%) to common antimicrobial agents, only 57.1% (8/14) of Escherichia coli isolates were susceptible to ampicillin and 58.3% (7/12) were susceptible to co-trimoxazole.

CONCLUSIONS

Gram-positive bacteria accounted for the majority of pediatric BSIs, of which invasive pneumococcal disease remains a noteworthy cause. The majority of isolates, except Escherichia coli, were susceptible to commonly used antimicrobials. This study confirms the knowledge of high rates of resistance of Escherichia coli to ampicillin. Therefore, empirical treatment should still include gentamicin. Monitoring of resistance patterns is warranted to ensure that antibiotic therapy remains appropriate.

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.

Pediatric-specific antimicrobial susceptibility data and empiric antibiotic selection

OBJECTIVE

Duke University Health System (DUHS) generates annual antibiograms combining adult and pediatric data. We hypothesized significant susceptibility differences exist for pediatric isolates and that distributing these results would alter antibiotic choices.

METHODS

Susceptibility rates for Escherichia coli isolates from patients aged ≤12 years between July 2009 and September 2010 were compared with the 2009 DUHS antibiogram. Pediatric attending and resident physicians answered case-based vignettes about children aged 3 months and 12 years with urinary tract infections. Each vignette contained 3 identical scenarios with no antibiogram, the 2009 DUHS antibiogram, and a pediatric-specific antibiogram provided. Effective antibiotics exhibited >80% in vitro susceptibility. Frequency of antibiotic selection was analyzed by using descriptive statistics.

RESULTS

Three hundred seventy-five pediatric isolates were identified. Pediatric isolates were more resistant to ampicillin and trimethoprim-sulfamethoxazole (TMP-SMX) and less resistant to amoxicillin-clavulanate and ciprofloxacin (P < .0005 for all). Seventy-five resident and attending physicians completed surveys. In infant vignettes, physicians selected amoxicillin-clavulanate (P < .05) and nitrofurantoin (P < .01) more often and TMP-SMX (P < .01) less often with pediatric-specific data. Effective antibiotic choices increased from 68.6% to 82.2% (P = .06) to 92.5% (P < .01) across scenarios. In adolescent vignettes, providers reduced TMP-SMX use from 66.2% to 42.6% to 19.0% (P < .01 for both). Effective antibiotic choices increased from 32.4% to 57.4% to 79.4% (P < .01 and P = .01).

CONCLUSIONS

Pediatric E. coli isolates differ significantly in antimicrobial susceptibility at our institution, particularly to frequently administered oral antibiotics. Knowledge of pediatric-specific data altered empirical antibiotic choices in case vignettes. Care of pediatric patients could be improved with use of a pediatric-specific antibiogram.

Antibiotic policies and control of resistance

PURPOSE OF THE REVIEW

The current worldwide pandemic of antibiotic resistance shows no signs of abating. It is clear that it is driven mainly by heavy and often inappropriate antibiotic use. Although control measures are widely practised, it is important that we assess their efficacy critically in order to concentrate expensive control efforts where they will be most effective. The past year has seen much activity in this area, with evidence-based assessments of the literature according to strict guidelines, as well as progress in basic science studies of mechanisms of resistance, and their causes and relations to pathogenicity and adaptability.

RECENT FINDINGS

The present review summarizes current developments in the causes of antibiotic resistance, the classification of antibiotic stewardship and control measures, the evidence base for their efficacy, current problems in hospital practice, the adaptability of bacteria, the content of antibiotic policies and anticipated activities.

SUMMARY

The conclusions from the published literature are that much of it that pertains to changing prescribing practices does not stand up to modern evidence-based analysis concepts. Nevertheless, we can learn from experience in changing other areas of medical practice. We must be pragmatic and must not expect to change the world, but rather take it step by step, recognizing barriers and measuring outcomes and quality indicators. Studies into the molecular basis of resistance confirm the superb genetic adaptability of micro-organisms. They will always be several steps ahead of us. Nevertheless, we are learning how to modify our prescribing habits to minimize resistance, not only by using antibiotics less frequently but also by altering dosing schedules in various ways.