Usefulness of antibiogram surveillance for methicillin-resistant Staphylococcus aureus in outpatient pediatric populations

A comparison of inpatient versus outpatient resistance patterns of pediatric urinary tract infection

PURPOSE

Prior single center studies showed that antibiotic resistance patterns differ between outpatients and inpatients. We compared antibiotic resistance patterns for urinary tract infection between outpatients and inpatients on a national level.

MATERIALS AND METHODS

We examined outpatient and inpatient urinary isolates from children younger than 18 years using The Surveillance Network (Eurofins Scientific, Luxembourg, Luxembourg), a database of antibiotic susceptibility results, as well as patient demographic data from 195 American hospitals. We determined the prevalence and antibiotic resistance patterns of the 6 most common uropathogens, including Escherichia coli, Proteus mirabilis, Klebsiella, Enterobacter, Pseudomonas aeruginosa and Enterococcus. We compared differences in uropathogen prevalence and resistance patterns for outpatient and inpatient isolates using chi-square analysis.

RESULTS

We identified 25,418 outpatient (86% female) and 5,560 inpatient (63% female) urinary isolates. Escherichia coli was the most common uropathogen overall but its prevalence varied by gender and visit setting, that is 79% of uropathogens overall for outpatient isolates, including 83% of females and 50% of males, compared to 54% for overall inpatient isolates, including 64% of females and 37% of males (p <0.001). Uropathogen resistance to many antibiotics was lower in the outpatient vs inpatient setting, including trimethoprim/sulfamethoxazole 24% vs 30% and cephalothin 16% vs 22% for E. coli (each p <0.001), cephalothin 7% vs 14% for Klebsiella (p = 0.03), ceftriaxone 12% vs 24% and ceftazidime 15% vs 33% for Enterobacter (each p <0.001), and ampicillin 3% vs 13% and ciprofloxacin 5% vs 12% for Enterococcus (each p <0.001).

CONCLUSIONS

Uropathogen resistance rates of several antibiotics are higher for urinary specimens obtained from inpatients vs outpatients. Separate outpatient vs inpatient based antibiograms can aid in empirical prescribing for pediatric urinary tract infections.

Comparison of antibiograms developed for inpatients and primary care outpatients

To support antimicrobial stewardship, some healthcare systems have begun creating outpatient antibiograms. We developed inpatient and primary care outpatient antibiograms for a regional health maintenance organization (HMO) and academic healthcare system (AHS). Antimicrobial susceptibilities from 16,428 Enterococcus, Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa cultures from 2010 were summarized and compared. Methicillin susceptibility among S. aureus was similar in inpatients and primary care outpatients (HMO: 61.2% versus 61.9%, P = 0.951; AHS: 62.9% versus 63.3%, P > 0.999). E. coli susceptibility to trimethoprim/sulfamethoxazole was also similar (HMO: 81.8% versus 83.6%, P = 0.328; AHS: 77.2% versus 80.9%, P = 0.192), but ciprofloxacin susceptibility differed (HMO: 88.9% versus 94.6%, P < 0.001; AHS: 81.2% versus 90.6%, P < 0.001). In the HMO, ciprofloxacin-susceptible P. aeruginosa were more frequent in primary care outpatients than in inpatients (91.4% versus 79.0%, P = 0.007). Comparison of cumulative susceptibilities across settings yielded no consistent patterns; therefore, outpatient primary care antibiograms may more accurately inform prudent empiric antibiotic prescribing.

Comparison of hospital-wide and age and location - stratified antibiograms of S. aureus, E. coli, and S. pneumoniae: age- and location-stratified antibiograms

Background

Antibiograms created by aggregating hospital-wide susceptibility data from diverse patients can be misleading. To demonstrate the utility of age- and location-stratified antibiograms, we compared stratified antibiograms for three common bacterial pathogens, E. coli, S. aureus, and S. pneumoniae. We created stratified antibiograms based on patient age (<18 years, 18–64 years, >/=65 years), and inpatient or outpatient location using all 2009 E. coli and S. aureus, and all 2008–2009 S. pneumoniae isolates submitted to our clinical microbiology laboratory. We compared susceptibility rates among cumulative and stratified antibiograms using descriptive statistics.

Findings

For E. coli and S. aureus, the institution-wide antibiogram overestimated resistance in pediatic isolates and underestimated resistance in isolates from the elderly. For E. coli, pediatric isolates were less susceptible to ampicillin and ampicillin-sulbactam and more susceptible to gentamicin and ciprofloxacin compared to adult isolates (p < 0.05 for all), and isolates from patients >65 years were least susceptible to ciprofloxacin (71%). For S. aureus, susceptibility to oxacillin, clindamycin, and levofloxacin was highest among children and decreased with increasing age (p < .001 for all). For S. pneumoniae, pediatric isolates were less susceptible than adult isolates to all agents except penicillin (IV breakpoint). Within children there were significant differences in susceptibility of inpatient and outpatient isolates of E. coli but not of S. aureus or S. pneumoniae.

Conclusions

Stratified antibiograms reveal age - associated differences in susceptibility of E. coli, S. aureus, and S. pneumoniae that are obscured by hospital-wide antibiograms. Age-stratified antibiograms have potential to influence antibiotic selection.

Antibiotic resistance patterns of outpatient pediatric urinary tract infections

PURPOSE

We characterize the current national patterns of antibiotic resistance of outpatient pediatric urinary tract infection.

MATERIALS AND METHODS

We examined outpatient urinary isolates from patients younger than 18 years in 2009 using The Surveillance Network®, a database with antibiotic susceptibility results and patient demographic data from 195 United States hospitals. We determined the prevalence and antibiotic resistance patterns for the 6 most common uropathogens, ie Escherichia coli, Proteus mirabilis, Klebsiella, Enterobacter, Pseudomonas aeruginosa and Enterococcus. We compared differences in uropathogen prevalence between males and females using chi-square analysis.

RESULTS

We identified 25,418 outpatient urinary isolates. E. coli was the most common uropathogen overall but the prevalence of E. coli was higher among females (83%) than males (50%, p <0.001). Other common species among males were Enterococcus (17%), P. mirabilis (11%) and Klebsiella (10%). However, these uropathogens each accounted for 5% or less of female isolates (p <0.001). Resistance among E. coli was highest for trimethoprim-sulfamethoxazole (24%) but lower for nitrofurantoin (less than 1%) and cephalothin (15%). Compared to 2002 Surveillance Network data, E. coli resistance rates increased for trimethoprim-sulfamethoxazole (from 23% to 31% in males and from 20% to 23% in females) and ciprofloxacin (from 1% to 10% and from 0.6% to 4%, respectively).

CONCLUSIONS

E. coli remains the most common pediatric uropathogen. Although widely used, trimethoprim-sulfamethoxazole is a poor empirical choice for pediatric urinary tract infections in many areas due to high resistance rates. First-generation cephalosporins and nitrofurantoin are appropriate narrow-spectrum alternatives given their low resistance rates. Local antibiograms should be used to assist with empirical urinary tract infection treatment.

Clinical Value of an Ambulatory-Based Antibiogram for Uropathogens in Children

Unnecessarily broad-spectrum antibiotic prescribing for ambulatory pediatric urinary tract infection may result from clinicians not having antibiograms specific to this population. Comparing an existing hospital-based with a proposed ambulatory uropathogen antibiogram for children in Utah, Escherichia coli accounted for a larger percentage and was more susceptible to narrower-spectrum antibiotics, demonstrating the potential need for ambulatory pediatric antibiograms.

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.