Antimicrobial use and antimicrobial resistance: a population perspective

Escherichia coli antimicrobial resistance increased faster among geriatric outpatients compared with adult outpatients in the USA, 2000-10

OBJECTIVES

Few studies have examined Escherichia coli antimicrobial resistance across age groups over time. The objective of this study was to compare urinary E. coli antimicrobial resistance trends among adult and geriatric outpatients from 2000 to 2010.

METHODS

Antimicrobial susceptibility results for E. coli urine isolates from adult (aged 16-64 years) and geriatric (aged ≥65 years) outpatients were analysed using data from The Surveillance Network Database-USA.

RESULTS

Susceptibility test results from adult (n = 6 412 025) and geriatric (n = 3 395 297) outpatients showed that E. coli antimicrobial resistance increased faster among geriatric outpatients for all agents studied. The greatest increases in resistance over the study time period were for ciprofloxacin (9.4% and 23.5% increases among adult and geriatric individuals, respectively), trimethoprim/sulfamethoxazole (4.3% and 10.5%) and ampicillin (2.0% and 13.6%).

CONCLUSIONS

Urinary E. coli antimicrobial resistance increased faster among geriatric outpatients than adult outpatients in the USA. Rising antimicrobial resistance disproportionately affects geriatric populations and presents a threat to public health.

Evaluation of programmatic changes to an antimicrobial stewardship program with house officer feedback

RATIONALE, AIMS AND OBJECTIVES

A collegial relationship between prescribers and antimicrobial stewards, along with an appreciation of the importance of antimicrobial stewardship, is essential for optimal functioning of an antimicrobial stewardship program (ASP). Programmatic adjustments based on feedback may be beneficial to the success of ASPs. The objective of this study is to assess the experience of house officers with the ASP and the effect of programmatic improvements.

METHODS

A survey of house officers at an academic medical centre was conducted assessing their experience with the ASP before (2008) and after (2010) programmatic interventions were instituted.

RESULTS

Of 225 house officer surveys sent, we received 97 responses (88% from medical doctors). The majority indicated that ASP was either very or somewhat important in fighting antibiotic resistance (100%), improving patient care (97%), preventing medication errors (91%) and containing health care costs (89%). Ninety-one per cent indicated either a very good or good educational experience with the ASP. The ASP often reminded respondents of a patient's allergy (31%), to adjust for renal function (78%), and 38% were prevented from making a medication error. Comparing 2008 and 2010, a higher proportion of respondents in 2010 said they had a very good or good educational experience with ASP [84% versus 98%, odds ratio (OR) = 8.40, P = 0.022] and a lower proportion of respondents reported confusion about ASP procedures (59% versus 39%, OR = 0.43, P = 0.048).

CONCLUSIONS

House officer feedback resulted in ASP policy changes which improved the ASP experience.

Effects of clinical pathways for common outpatient infections on antibiotic prescribing

BACKGROUND

Antibiotic overuse in the primary care setting is common. Our objective was to evaluate the effect of a clinical pathway-based intervention on antibiotic use.

METHODS

Eight primary care clinics were randomized to receive clinical pathways for upper respiratory infection, acute bronchitis, acute rhinosinusitis, pharyngitis, acute otitis media, urinary tract infection, skin infections, and pneumonia and patient education materials (study group) versus no intervention (control group). Generalized linear mixed effects models were used to assess trends in antibiotic prescriptions for non-pneumonia acute respiratory infections and broad-spectrum antibiotic use for all 8 conditions during a 2-year baseline and 1-year intervention period.

RESULTS

In the study group, antibiotic prescriptions for non-pneumonia acute respiratory infections decreased from 42.7% of cases at baseline to 37.9% during the intervention period (11.2% relative reduction) (P<.0001) and from 39.8% to 38.7%, respectively, in the control group (2.8% relative reduction) (P=.25). Overall use of broad-spectrum antibiotics in the study group decreased from 26.4% to 22.6% of cases, respectively (14.4% relative reduction) (P<.0001) and from 20.0% to 19.4%, respectively, in the control group (3.0% relative reduction) (P=.35). There were significant differences in the trends of prescriptions for acute respiratory infections (P<.0001) and broad-spectrum antibiotic use (P=.001) between the study and control groups during the intervention period, with greater declines in the study group.

CONCLUSIONS

This intervention was associated with declining antibiotic prescriptions for non-pneumonia acute respiratory infections and use of broad-spectrum antibiotics over the first year. Evaluation of the impact over a longer study period is warranted.

Risks of population antimicrobial resistance associated with chronic macrolide use for inflammatory airway diseases

Macrolide antibiotics have established efficacy in the management of cystic fibrosis and diffuse panbronchiolitis-uncommon lung diseases with substantial morbidity and the potential for rapid progression to death. Emerging evidence suggests benefits of maintenance macrolide treatment in more indolent respiratory diseases including chronic obstructive pulmonary disease and non-cystic fibrosis bronchiectasis. In view of the greater patient population affected by these disorders (and potential for macrolide use to spread to disorders such as chronic cough), widespread use of macrolides, particularly azithromycin, has the potential to substantially influence antimicrobial resistance rates of a range of respiratory microbes. In this Personal View, I explore theories around population (rather than patient) macrolide resistance, appraise evidence linking macrolide use with development of resistance, and highlight the risks posed by injudicious broadening of their use, particularly of azithromycin. These risks are weighed against the potential benefits of macrolides in less aggressive inflammatory airway disorders. A far-sighted approach to maintenance macrolide use in non-cystic fibrosis inflammatory airway diseases is needed, which minimises risks of adversely affecting community macrolide resistance: combining preferential use of erythromycin and restriction of macrolide use to those patients at greatest risk represents an appropriately cautious management approach.

Effects of infection control measures on acquisition of five antimicrobial drug-resistant microorganisms in a tetanus intensive care unit in Vietnam

Purpose

To quantify the effects of barrier precautions and antibiotic mixing on prevalence and acquisition of five drug-resistant microorganisms within a single tetanus intensive care unit at a tertiary referral hospital in Ho Chi Minh City, Vietnam.

Methods

All patients admitted within the study period were included. After a 1-year baseline period, barrier precautions were implemented and the single empirical treatment ceftazidime was changed to mixing (per consecutive patient) of three different regimens (ceftazidime, ciprofloxacin, piperacillin–tazobactam). Markov chain modeling and genotyping were used to determine the effects of interventions on prevalence levels and the relative importance of cross-transmission and antibiotic-associated selection.

Results

A total of 190 patients were included in year 1 (2,708 patient days, 17,260 cultures) and 167 patients in year 2 (3,384 patient days, 20,580 cultures). In year 1, average daily prevalence rates for methicillin-resistant Staphylococcus aureus (MRSA), extended spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae (excluding Klebsiella pneumoniae), Pseudomonas aeruginosa, gentamicin-resistant K. pneumoniae, and amikacin-resistant Acinetobacter species were 34.0, 61.3, 53.4, 65.7 and 57.1 %. After intervention, ceftazidime usage decreased by 53 %; the use of piperacillin–tazobactam and ciprofloxacin increased 7.2-fold and 4.5-fold, respectively. Adherence to hand hygiene after patient contact was 54 %. These measures were associated with a reduction of MRSA prevalence by 69.8 % (to 10.3 %), mainly because of less cross-transmission (88 % reduction), and of ESBL-producing Enterobacteriaceae prevalence by 10.3 % (non-significantly). In contrast, prevalence levels of the other three pathogens remained unaffected.

Conclusion

The combination of simple infection control measures and antibiotic mixing was highly effective in reducing the prevalence of MRSA, but not of Gram-negative microorganisms.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-012-2771-1) contains supplementary material.

Antimicrobial agent exposure and the emergence and spread of resistant microorganisms: issues associated with study design

Antibiotics are essential agents that have greatly reduced human mortality due to infectious diseases. Their use, and sometimes overuse, have increased over the past several decades in humans, veterinary medicine and agriculture. However, the emergence of resistant pathogens is becoming an increasing problem that could result in the re-emergence of infectious diseases. Antibiotic prescription in human medicine plays a key role in this phenomenon. Under selection pressure, resistance can emerge in the commensal flora of treated individuals and disseminate to others. However, even if the effects of antimicrobial use on resistance is intuitively accepted, scientific rationales are required to convince physicians, legislators and public opinion to adopt appropriate behaviours and policies. With this review, we aim to provide an overview of different epidemiological study designs that are used to study the relationship between antibiotic use and the emergence and spread of resistance, as well as highlight their main strengths and weaknesses.

When does overuse of antibiotics become a tragedy of the commons?

BACKGROUND

Over-prescribing of antibiotics is considered to result in increased morbidity and mortality from drug-resistant organisms. A resulting common wisdom is that it would be better for society if physicians would restrain their prescription of antibiotics. In this view, self-interest and societal interest are at odds, making antibiotic use a classic "tragedy of the commons".

METHODS AND FINDINGS

We developed two mathematical models of transmission of antibiotic resistance, featuring de novo development of resistance and transmission of resistant organisms. We analyzed the decision to prescribe antibiotics as a mathematical game, by analyzing individual incentives and community outcomes.

CONCLUSIONS

A conflict of interest may indeed result, though not in all cases. Increased use of antibiotics by individuals benefits society under certain circumstances, despite the amplification of drug-resistant strains or organisms. In situations where increased use of antibiotics leads to less favorable outcomes for society, antibiotics may be harmful for the individual as well. For other scenarios, where a conflict between self-interest and society exists, restricting antibody use would benefit society. Thus, a case-by-case assessment of appropriate use of antibiotics may be warranted.

High discordance of chest x-ray and computed tomography for detection of pulmonary opacities in ED patients: implications for diagnosing pneumonia

OBJECTIVE

To evaluate the diagnostic performance of chest x-ray (CXR) compared to computed tomography (CT) for detection of pulmonary opacities in adult emergency department (ED) patients.

METHODS

We conducted an observational cross-sectional study of adult patients presenting to 12 EDs in the United States from July 1, 2003, through November 30, 2006, who underwent both CXR and chest CT for routine clinical care. CXRs and CT scans performed on the same patient were matched. CXRs and CT scans were interpreted by attending radiologists and classified as containing pulmonary opacities if the final radiologist report noted opacity, infiltrate, consolidation, pneumonia, or bronchopneumonia. Using CT as a criterion standard, the diagnostic test characteristics of CXR to detect pulmonary opacities were calculated.

RESULTS

The study cohort included 3423 patients. Shortness of breath, chest pain and cough were the most common complaints, with 96.1% of subjects reporting at least one of these symptoms. Pulmonary opacities were visualized on 309 (9.0%) CXRs and 191 (5.6 %) CT scans. CXR test characteristics for detection of pulmonary opacities included: sensitivity 43.5% (95% CI, 36.4%-50.8%); specificity 93.0% (95% CI, 92.1%-93.9%); positive predictive value 26.9% (95% CI, 22.1%-32.2%); and negative predictive value 96.5% (95% CI, 95.8%-97.1%).

CONCLUSION

In this multicenter cohort of adult ED patients with acute cardiopulmonary symptoms, CXR demonstrated poor sensitivity and positive predictive value for detecting pulmonary opacities. Reliance on CXR to identify pneumonia may lead to significant rates of misdiagnosis.

Antibiotic resistance: from Darwin to Lederberg to Keynes

The emergence and spread of antibiotic-resistant bacteria reflects both, a gradual, completely Darwinian evolution, which mostly yields slight decreases in antibiotic susceptibility, along with phenotypes that are not precisely characterized as "resistance"; and sudden changes, from full susceptibility to full resistance, which are driven by a vast array of horizontal gene transfer mechanisms. Antibiotics select for more than just antibiotic resistance (i.e., increased virulence and enhanced gene exchange abilities); and many non-antibiotic agents or conditions select for or maintain antibiotic resistance traits as a result of a complex network of underlying and often overlapping mechanisms. Thus, the development of new antibiotics and thoughtful, integrated anti-infective strategies is needed to address the immediate and long-term threat of antibiotic resistance. Since the biology of resistance is complex, these new drugs and strategies will not come from free-market forces, or from "incentives" for pharmaceutical companies.

Antimicrobial resistance and pharmacodynamics of canine and feline pathogenic E. coli in the United States

Percent resistance and minimum inhibitory concentrations (MIC) were described for canine (n = 301) and feline (n = 75) pathogenic Escherichia coli (E. coli) isolates solicited during May 2005 to Sep 2005 from the Clinical Pharmacology Laboratory at Auburn University (n = 165) or commercial diagnostic laboratories ([CDL]; n = 211) from four regions in the USA. Drugs tested were amoxicillin (AMX), amoxicillin trihydrate/clavulanate potassium (AMXC), cefpodoxime (CFP), doxycycline (DXY), enrofloxacin (ENR), gentamicin (GM) and trimethoprim-sulfamethoxazole (TMS). Urinary isolates were most common (n = 174). Percent resistance was greatest for isolates from the respiratory tract, urine, and skin compared with the ear. Resistance was also greatest for samples sent from the south and central states compared with the western states (P ≤ 0.001). Percent resistance by drug was AMX (46 ± 2.6%) > AMXC (37 ± 2.5%) > CFP (21.8 ± 2%) = DXY (22 ± 2.1%) = ENR (20 ± 2.1%) = TMS (19 ± 2%) > GM (12 ± 1.7%). There was a significant difference in resistance between the different antibiotic drugs (P ≤ 0.001). Population MIC distributions were bimodal, and MICs were highest in samples from the southern states (P ≤ 0.001). E. coli resistance may limit its empirical treatment. For susceptible isolates, AMX and AMXC may be least effective and TMS most effective.

Quantitative measurement of blaCMY-2 in a longitudinal observational study of dairy cattle treated with ceftiofur

There is concern that a relationship exists between antibiotic use in livestock production and the emergence, spread, and persistence of antibiotic resistance. It is important to understand the impact that therapeutic doses of antibiotics for treatment of disease have on resistance because disease treatment typically involves higher doses of antibiotic over short time spans. Absolute quantities of the antibiotic resistance gene bla(CMY-2) were measured by real-time quantitative polymerase chain reaction (qPCR) in the bacterial community DNA of fecal samples from dairy cattle that were given a 5-day course of ceftiofur and untreated cattle during a longitudinal, observational study. A hierarchical linear model that accounts for left-censored data and repeated measures was used to estimate group means of bla(CMY-2) from the qPCR data. Ceftiofur-treated animals had significantly higher mean quantities of bla(CMY-2) than untreated animals during treatment. On the first day post-treatment, mean quantities of bla(CMY-2) returned to pre-treatment levels and remained low in both groups for the remainder of the study. The use of qPCR to measure bla(CMY-2) quantities provided evidence that the burden of resistance in treated animals may have increased temporarily, a result that was not evident when using only cultivation-based methods of testing for resistance.

Modeling the effects of introducing a new antibiotic in a hospital setting: A case study

The increase in antibiotic resistance continues to pose a public health risk as very few new antibiotics are being produced, and bacteria resistant to currently prescribed antibiotics is growing. Within a typical hospital setting, one may find patients colonized with bacteria resistant to a single antibiotic, or, of a more emergent threat, patients may be colonized with bacteria resistant to multiple antibiotics. Precautions have been implemented to try to prevent the growth and spread of antimicrobial resistance such as a reduction in the distribution of antibiotics and increased hand washing and barrier preventions; however, the rise of this resistance is still evident. As a result, there is a new movement to try to re-examine the need for the development of new antibiotics. In this paper, we use mathematical models to study the possible benefits of implementing a new antibiotic in this setting; through these models, we examine the use of a new antibiotic that is distributed in various ways and how this could reduce total resistance in the hospital. We compare several different models in which patients colonized with both single and dual-resistant bacteria are present, including a model with no additional treatment protocols for the population colonized with dual-resistant bacteria as well as models including isolation and/or treatment with a new antibiotic. We examine the benefits and limitations of each scenario in the simulations presented.

Increase of carbapenem-resistant Acinetobacter baumannii infection in acute care hospitals in Taiwan: association with hospital antimicrobial usage

Objective

Carbapenem-resistant Acinetobacter baumannii (CRAB) has emerged as an important pathogen causing healthcare-associated infections (HAIs) in Taiwan. The present study is aimed to investigate the epidemiology of HAIs caused by CRAB and the association of CRAB infection and hospital usage of different antimicrobials.

Methods

Two nationwide databases in the period 2003 to 2008, the Taiwan Nosocomial Infection Surveillance System and National Health Insurance claim data, were used for analysis. A total of 13,811 healthcare-associated A. baumannii infections and antimicrobial usage data from 121 hospitals were analyzed.

Results

There was a significant increase in the proportion of number of HAIs caused by CRAB over that by all A. baumannii (CRABpAB), from 14% in 2003 to 46% in 2008 (P<0.0001). The greatest increase was in central Taiwan, from 4% in 2003 to 62% in 2008 (P<0.0001). Use of anti-pseudomonal carbapenems, but not other classes of antibiotics, was significantly correlated with the increase of CRABpAB (r = 0.86, P<0.0001).

Conclusions

We suggested that dedicated use of anti-pseudomonal carbapenems would be an important intervention to control the increase of CRABpAB.

A challenge to appropriate antibiotic use in children with respiratory infections: a 5-year single-institution experience

BACKGROUND

We have studied the rate of emergence of antibiotic-resistant Streptococcus pneumoniae (S. pneumoniae) and Haemophilus influenzae (H. influenzae) and the subsequent antibiotic use in host patients of those isolates at the Department of Pediatrics, Soma General Hospital, Fukushima. Moreover, we carried out several studies investigating the risks and benefits of antibiotic-free treatment for children with respiratory infections. In this report, we summarize our research and suggest better treatment options for pediatric patients with respiratory infections.

METHODS

We investigated the necessity of antibiotic use in the treatment of pediatric inpatients with respiratory syncytial virus (RSV) infection, and tested our hypothesis that antibiotic-free treatment for common cold will reduce the number of resistant S. pneumoniae strains in the pediatric nasopharynx. Therefore, we restricted prescribing antibiotics for pediatric patients with respiratory infections. The rates of resistant S. pneumoniae and H. influenzae and the medication history of the host patients before and after the intervention were compared.

RESULTS

We found that most of the RSV-infected patients recovered without antibiotic treatment, and that the antibiotic-free treatment inhibited the emergence of antibiotic-resistant strains. The rate of penicillin-resistant S. pneumoniae decreased but the rate of ampicillin-resistant H. influenzae did not change significantly during the study.

CONCLUSION

We concluded that patients with respiratory infections can be treated without antibiotics, under careful examination and observation. Continued monitoring of such new interventions as well as recommending their use to other caregivers and physicians will help inhibit the spread of resistant strains.

Efficacy of infection control interventions in reducing the spread of multidrug-resistant organisms in the hospital setting

Multidrug-resistant organisms (MDRO) continue to spread in hospitals globally, but the population-level impact of recommended preventive strategies and the relative benefit of individual strategies targeting all MDRO in the hospital setting are unclear. To explore the dynamics of MDRO transmission in the hospital, we develop a model extending data from clinical individual-level studies to quantify the impact of hand hygiene, contact precautions, reducing antimicrobial exposure and screening surveillance cultures in decreasing the prevalence of MDRO colonization and infection. The effect of an ongoing increase in the influx of patients colonized with MDRO into the hospital setting is also quantified. We find that most recommended strategies have substantial effect in decreasing the prevalence of MDRO over time. However, screening for asymptomatic MDRO colonization among patients who are not receiving antimicrobials is of minimal value in reducing the spread of MDRO.

Genetic Determinants of Methicillin Resistance and Virulence among Staphylococcus aureus Isolates Recovered from Clinical and Surveillance Cultures in a Brazilian Teaching Hospital

Aims. To quantify the presence of SCCmec types and virulence genes among Staphylococcus aureus colonizing and infecting patients from a teaching hospital. Methods. We analyzed 225 and 84 S. aureus isolates recovered from surveillance and clinical cultures, respectively. Strains were studied for the presence and type of SCCmec, as well as for several virulence genes. Univariate and multivariable analysis were performed in order to identify predictors of invasiveness (defined as isolation from clinical cultures). Results. The presence of SCCmec types III (OR, 2.19, 95% CI, 1.08–4.45) and IV (OR, 5.28 95% CI, 1.35–20.63) and of genes coding for exfoliative toxin B (etb, OR, 6.38, 95% CI, 1.48–27.46) and Panton-Valentine leukocidin (pvl, OR, 2.38, 95% CI, 1.16–4.86) was independently associated with invasiveness. Conclusions. SCCmec types III and IV and virulence genes are associated with greater invasiveness of S. aureus. Patients colonized with methicillin-resistant S. aureus, as well as with strains harboring etb or pvl, may be prone to develop invasive disease. Infection-preventing strategies should be more intensively applied to this group.

[Programs for optimizing the use of antibiotics (PROA) in Spanish hospitals: GEIH-SEIMC, SEFH and SEMPSPH consensus document]

The antimicrobial agents are unique drugs for several reasons. First, their efficacy is higher than other drugs in terms of reduction of morbidity and mortality. Also, antibiotics are the only group of drugs associated with ecological effects, because their administration may contribute to the emergence and spread of microbial resistance. Finally, they are used by almost all medical specialties. Appropriate use of antimicrobials is very complex because of the important advances in the management of infectious diseases and the spread of antibiotic resistance. Thus, the implementation of programs for optimizing the use of antibiotics in hospitals (called PROA in this document) is necessary. This consensus document defines the objectives of the PROA (namely, to improve the clinical results of patients with infections, to minimise the adverse events associated to the use of antimicrobials including the emergence and spread of antibiotic resistance, and to ensure the use of the most cost-efficacious treatments), and provides recommendations for the implementation of these programs in Spanish hospitals. The key aspects of the recommendations are as follows. Multidisciplinary antibiotic teams should be formed, under the auspices of the Infection Committees. The PROA need to be considered as part of institutional programs and the strategic objectives of the hospital. The PROA should include specific objectives based on measurable indicators, and activities aimed at improving the use of antimicrobials, mainly through educational activities and interventions based more on training activities directed to prescribers than just on restrictive measures.

Antimicrobial prescribing in the USA for adult acute pharyngitis in relation to treatment guidelines

RATIONALE, AIMS AND OBJECTIVES

American College of Physicians (ACP) published guidelines for the diagnosis and treatment of acute pharyngitis in adults in 2001. The objective of this study is to characterize antibiotic prescribing patterns in the USA for acute pharyngitis and evaluate concordance with the 2001 ACP pharyngitis treatment guidelines.

METHODS

Patients aged ≥18 years identified with acute pharyngitis via diagnosis codes (ICD-9 CM) were identified from data collected annually (1996-2006) by the National Center for Health Statistics and Centers for Disease Control and Prevention from the National Ambulatory Medical Care Survey and the National Hospital Ambulatory Medical Care Survey. Total US office visits for acute pharyngitis were estimated. Logistic regression was performed to determine whether antibiotic prescribing was associated with the publishing of the ACP guidelines.

RESULTS

A total of 3791 office visits met study criteria. We extrapolated 78.0 million visits for acute pharyngitis from 1996 to 2006. Antibiotics were prescribed in 62.6% of cases and 7.5% of cases received ACP-recommended antibiotics. There was a significant decrease in the rate of antibiotic prescriptions from 66.5% to 59.1% after publication of ACP guidelines. Univariate analysis showed that antibiotic prescribing decreased by 27% (OR = 0.73, 95% CI 0.55-0.95, P = 0.021). Multivariate analyses confirmed this finding (OR = 0.72, 95% CI 0.56-0.94, P = 0.014). The prescribing of ACP-recommended antibiotics did not significantly change (8.5% to 6.6%, P = 0.519).

CONCLUSIONS

Publishing of ACP guidelines for the diagnosis and treatment of pharyngitis was associated with a decrease in the overall prescribing of antibiotics but not the prescribing of ACP-recommended antibiotics.

Reduction in antibiotic use following a cluster randomized controlled multifaceted intervention: the Israeli judicious antibiotic prescription study

BACKGROUND

Antibiotic overuse is of great public health concern. This study assessed whether intervention among physicians and their treated population could achieve a sustained reduction in antibiotic use, specifically in classes known to promote antibiotic resistance among children in a community setting.

METHODS

We performed a cluster randomized controlled multifaceted trial among 52 primary care pediatricians and the 88,000 children registered in their practices. The intervention was led by local leaders and engaged the participating physicians. It included physician focus group meetings, workshops, seminars, and practice campaigns. These activities focused on self-developed guidelines, improving parent and physician knowledge, diagnostic skills, and parent-physician communication skills that promoted awareness of antibiotic resistance. The main outcome measure was the change in annual antibiotic prescription rates (APRs) of children treated by the intervention group physicians as compared with rates among those treated by control group physicians. The study comprised a 2-year pre-intervention period, a 3-year intervention period, and a 1-year follow-up period. Mixed-effect models were used to assess risk ratios to account for the clustered study design.

RESULTS

A decrease in the total APR among children treated by the intervention physicians compared with those treated by the control physicians was observed in the first intervention year (APR decrease among control physicians, 40%; APR decrease among intervention physicians, 22%; relative risk [RR], .76; 95% confidence interval [CI], .75-.78). This reduction crossed over all antibiotic classes but was most prominent for macrolides (macrolide prescription rate among control physicians, 58%; macrolide prescription rate among intervention physicians, 27%; RR, .58; 95% CI, .55-.62). The effect was sustained during the 4 following years. CONCLUSIONS. Multifaceted intervention that engages the physicians in an educational process is effective in reducing APRs and can be sustained.

CLINICAL TRIALS REGISTRATION

NCT01187758.

Antimicrobial use and incidence of multidrug-resistant Pseudomonas aeruginosa in a teaching hospital: an ecological approach

INTRODUCTION

Multidrug-resistant Pseudomonas aeruginosa is a major threat in healthcare settings. The use of antimicrobials can influence the incidence of resistant strains by direct and indirect mechanisms. The latter can be addressed by ecological studies.

METHODS

Our group attempted to analyze the relation between the use of antipseudomonal drugs and the incidence of MDR-PA among 18 units from a 400-bed teaching hospital. The study had a retrospective, ecological design, comprising data from 2004 and 2005. Data on the use of four antimicrobials (amikacin, ciprofloxacin, ceftazidime and imipenem) were tested for correlation with the incidence of MDR-PA (defined as isolates resistant to the four antimicrobials of interest) in clinical cultures. Univariate and multivariate linear regression analyses were performed.

RESULTS

Significant correlations were determined between use and resistance for all antimicrobials in the univariate analysis: amikacin (standardized correlation coefficient = 0.73, p = 0.001); ciprofloxacin (0.71, p = 0.001); ceftazidime (0.61, p = 0.007) and imipenem (0.87, p < 0.001). In multivariate analysis, only imipenem (0.67, p = 0.01) was independently related to the incidence of multidrug-resistant strains.

CONCLUSIONS

These findings share similarities with those reported in individual-based observational studies, with possible implications for infection control.

Improving antimicrobial stewardship: the evolution of programmatic strategies and barriers

OBJECTIVE

To describe the prevalence and characteristics of antimicrobial stewardship programs (ASPs) in hospitals across the United States and to describe financial support provided for these programs.

DESIGN

Electronic and paper 14-question survey of infectious diseases physician members of the Infectious Diseases Society of America Emerging Infections Network (IDSA EIN).

PARTICIPANTS

All 1,044 IDSA EIN members who care for adult patients were invited to participate.

RESULTS

Five hundred twenty-two (50%) members responded. Seventy-three percent of respondents reported that their institutions had or were planning an ASP, compared with 50% reporting the same thing in an EIN survey 10 years before. A shift was noted from formulary restriction alone to use of a set of tailored strategies designed to provide information and feedback to prescribers, particularly in community hospitals. Lack of funding and lack of personnel were reported as major barriers to implementing a program. Fifty-two percent of respondents with an ASP reported that infectious diseases physicians do not receive direct compensation for their participation in the ASP, compared with 18% 10 years ago.

CONCLUSIONS

The percentage of institutions reporting ASPs has increased over the last decade, although small community hospitals were least likely to have these programs. In addition, ASP strategies have shifted dramatically. Lack of funding remains a key barrier for ASPs, and administrators need additional cost savings data in order to support ASPs. Interestingly, while guidelines and editorials regard compensated participation by an infectious diseases physician in these programs as critical, we found that more than half of the respondents reported no direct compensation for ASP activities.

Epidemiology and characteristics of antimicrobial resistance in China

A comprehensive surveillance system for bacterial resistance in tertiary hospitals has been established in China that involves tertiary hospitals in distinct regions nationwide, enabling the collection of a large amount of antimicrobial surveillance data. Antimicrobial resistance in China has become a serious healthcare problem, with high resistance rates of most common bacteria to clinically important antimicrobial agents. Methicillin-resistant S. aureus, ESBL-producing Enterobacteriaceae and carbapenem-resistant Acinetobacter baumannii represent more than 50% of microbial isolates. Additionally, bacterial resistance to fluoroquinolones, macrolides and third-generation cephalosporins is of serious concern. The molecular epidemiology and resistance mechanisms of the antimicrobial strains in China exhibited regional specificity, as well as the influence of dissemination of international clonal complexes. The molecular characteristics of MRSA, ESBL- and carbapenemase-producing Enterobacteriaceae, and macrolide-resistant gram-positive Streptococci in China were significantly different from those in other countries and regions, while S. pneumoniae serotypes appear to have been affected by the global spread of prevalent clones in other parts of the world. Moreover, important antimicrobial resistant bacteria such as community-acquired-MRSA, multidrug-resistant P. aeruginosa and extensive-resistant A. baumannii, and the antimicrobial resistance in primary healthcare and outpatient setting should be intensely monitored and investigated in the future.

Identification of bacterial plasmids based on mobility and plasmid population biology

Plasmids contain a backbone of core genes that remains relatively stable for long evolutionary periods, making sense to speak about plasmid species. The identification and characterization of the core genes of a plasmid species has a special relevance in the study of its epidemiology and modes of transmission. Besides, this knowledge will help to unveil the main routes that genes, for example antibiotic resistance (AbR) genes, use to travel from environmental reservoirs to human pathogens. Global dissemination of multiple antibiotic resistances and virulence traits by plasmids is an increasing threat for the treatment of many bacterial infectious diseases. To follow the dissemination of virulence and AbR genes, we need to identify the causative plasmids and follow their path from reservoirs to pathogens. In this review, we discuss how the existing diversity in plasmid genetic structures gives rise to a large diversity in propagation strategies. We would like to propose that, using an identification methodology based on plasmid mobility types, we can follow the propagation routes of most plasmids in Gammaproteobacteria, as well as their cargo genes, in complex ecosystems. Once the dissemination routes are known, designing antidissemination drugs and testing their efficacy will become feasible. We discuss in this review how the existing diversity in plasmid genetic structures gives rise to a large diversity in propagation strategies. We would like to propose that, by using an identification methodology based on plasmid mobility types, we can follow the propagation routes of most plasmids in ?-proteobacteria, as well as their cargo genes, in complex ecosystems.

At least it won't hurt: the personal risks of antibiotic exposure

This review presents recent evidence regarding the adverse effects of antibiotic therapy mediated by collateral damage to commensal flora. Two major drivers have characterized recent research in this field: new perspectives into human microbiota afforded by next-generation DNA sequencing techniques and ongoing attention to antimicrobial resistance. New molecular techniques have illustrated that antibiotic therapy can disturb human microbiota, and that these changes are associated with infection. Concurrently, epidemiologic studies using patient-level data offer new insights into the role of antibiotics in the emergence, selection and spread of antimicrobial resistance, and Clostridium difficile infection (CDI).

The evolution of drug resistance and the curious orthodoxy of aggressive chemotherapy

The evolution of drug-resistant pathogens is a major challenge for 21st century medicine. Drug use practices vigorously advocated as resistance management tools by professional bodies, public health agencies, and medical schools represent some of humankind's largest attempts to manage evolution. It is our contention that these practices have poor theoretical and empirical justification for a broad spectrum of diseases. For instance, rapid elimination of pathogens can reduce the probability that de novo resistance mutations occur. This idea often motivates the medical orthodoxy that patients should complete drug courses even when they no longer feel sick. Yet "radical pathogen cure" maximizes the evolutionary advantage of any resistant pathogens that are present. It could promote the very evolution it is intended to retard. The guiding principle should be to impose no more selection than is absolutely necessary. We illustrate these arguments in the context of malaria; they likely apply to a wide range of infections as well as cancer and public health insecticides. Intuition is unreliable even in simple evolutionary contexts; in a social milieu where in-host competition can radically alter the fitness costs and benefits of resistance, expert opinion will be insufficient. An evidence-based approach to resistance management is required.

Dynamics of antibiotic resistant Mycobacterium tuberculosis during long-term infection and antibiotic treatment

For an infecting bacterium the human body provides several potential ecological niches with both internally (e.g. host immunity) and externally (e.g. antibiotic use) imposed growth restrictions that are expected to drive adaptive evolution in the bacterium, including the development of antibiotic resistance. To determine the extent and pattern of heterogeneity generated in a bacterial population during long-term antibiotic treatment, we examined in a monoclonal Mycobacterium tuberculosis infection antibiotic resistant mutants isolated from one patient during a 9-years period. There was a progressive accumulation of resistance mutations in the infecting clone. Furthermore, apparent clonal sweeps as well as co-existence of different resistant mutants were observed during this time, demonstrating that during treatment there is a high degree of dynamics in the bacterial population. These findings have important implications for diagnostics and treatment of drug resistant tuberculosis infections.

Topical fluoroquinolone use as a risk factor for in vitro fluoroquinolone resistance in ocular cultures

OBJECTIVE

To determine whether recent use of topical fluoroquinolones is a risk factor for in vitro fluoroquinolone resistance in Staphylococcus aureus ocular isolates.

METHODS

Disk diffusion susceptibility testing for ciprofloxacin, moxifloxacin, and gatifloxacin was performed for all ocular isolates of S aureus at the Francis I. Proctor Foundation microbiology laboratory from January 1, 2005, to December 31, 2008. The medical records of patients with positive S aureus cultures were reviewed to determine topical or systemic fluoroquinolone use within the 3 months prior to culture. The Fisher exact test was used to compare the proportion of patients who used topical fluoroquinolones in the past 3 months among fluoroquinolone-sensitive and -resistant cases. Logistic regression was used to determine risk factors for fluoroquinolone resistance.

RESULTS

Of 200 S aureus cultures, 41 were resistant to ciprofloxacin, moxifloxacin, and gatifloxacin (20.5%). Fluoroquinolone-resistant S aureus isolates were from older patients (mean [SD] age, 65.5 [25.0] years) compared with fluoroquinolone-susceptible isolates (mean [SD] patient age, 52.1 [22.1] years) (P = .003). Use of fluoroquinolones within the 3 months before testing was more frequent in resistant isolates (29%) than in susceptible isolates (11%) (P = .005), as was recent hospitalization (22% of resistant isolates, 0% of susceptible isolates) (P < .001). In the multivariate regression analysis, topical fluoroquinolone use within 3 months was a significant predictor of fluoroquinolone resistance (P = .046), along with age, systemic immunosuppression, and topical fluoroquinolone use between 3 and 6 months before testing.

CONCLUSION

Recent topical fluoroquinolone use is significantly associated with fluoroquinolone resistance in S aureus isolates from ocular cultures.

The evolution of plasmid-carried antibiotic resistance

Background

Antibiotic resistance represents a significant public health problem. When resistance genes are mobile, being carried on plasmids or phages, their spread can be greatly accelerated. Plasmids in particular have been implicated in the spread of antibiotic resistance genes. However, the selective pressures which favour plasmid-carried resistance genes have not been fully established. Here we address this issue with mathematical models of plasmid dynamics in response to different antibiotic treatment regimes.

Results

We show that transmission of plasmids is a key factor influencing plasmid-borne antibiotic resistance, but the dosage and interval between treatments is also important. Our results also hold when plasmids carrying the resistance gene are in competition with other plasmids that do not carry the resistance gene. By altering the interval between antibiotic treatments, and the dosage of antibiotic, we show that different treatment regimes can select for either plasmid-carried, or chromosome-carried, resistance.

Conclusions

Our research addresses the effect of environmental variation on the evolution of plasmid-carried antibiotic resistance.

Population biological principles of drug-resistance evolution in infectious diseases

The emergence of resistant pathogens in response to selection pressure by drugs and their possible disappearance when drug use is discontinued are evolutionary processes common to many pathogens. Population biological models have been used to study the dynamics of resistance in viruses, bacteria, and eukaryotic microparasites both at the level of the individual treated host and of the treated host population. Despite the existence of generic features that underlie such evolutionary dynamics, different conclusions have been reached about the key factors affecting the rate of resistance evolution and how to best use drugs to minimise the risk of generating high levels of resistance. Improved understanding of generic versus specific population biological aspects will help to translate results between different studies, and allow development of a more rational basis for sustainable drug use than exists at present.

Estimation of transmission parameters of a fluoroquinolone-resistant Escherichia coli strain between pigs in experimental conditions

Antimicrobial resistance is of primary importance regarding public and animal health issues. Persistence and spread of resistant strains within a population contribute to the maintenance of a reservoir and lead to treatment failure. An experimental trial was carried out to study the horizontal transmission of a fluoroquinolone-resistant Escherichia coli strain from inoculated to naïve pigs. All naïve contact pigs had positive counts of fluoroquinolone-resistant E. coli after only two days of contact. Moreover, re-infections of inoculated pigs caused by newly contaminated animals were suspected. A maximum likelihood method, based on a susceptible-infectious-susceptible (SIS) model, was used to determine the transmission parameters. Two transmission levels were identified depending on the quantity of bacteria shed by infected individuals: (i) low-shedders with bacterial counts of resistant E. coli in the faeces between 5*10³ and 10⁶ CFU/g (β_L = 0.41 [0.27; 0.62]), (ii) high shedders with bacterial counts above 10⁶ CFU/g (β_H = 0.98 [0.59; 1.62]). Hence, transmission between animals could be pivotal in explaining the persistence of resistant bacteria within pig herds.

A spatial approach for the epidemiology of antibiotic use and resistance in community-based studies: the emergence of urban clusters of Escherichia coli quinolone resistance in Sao Paulo, Brasil

BACKGROUND

Population antimicrobial use may influence resistance emergence. Resistance is an ecological phenomenon due to potential transmissibility. We investigated spatial and temporal patterns of ciprofloxacin (CIP) population consumption related to E. coli resistance emergence and dissemination in a major Brazilian city. A total of 4,372 urinary tract infection E. coli cases, with 723 CIP resistant, were identified in 2002 from two outpatient centres. Cases were address geocoded in a digital map. Raw CIP consumption data was transformed into usage density in DDDs by CIP selling points influence zones determination. A stochastic model coupled with a Geographical Information System was applied for relating resistance and usage density and for detecting city areas of high/low resistance risk.

RESULTS

E. coli CIP resistant cluster emergence was detected and significantly related to usage density at a level of 5 to 9 CIP DDDs. There were clustered hot-spots and a significant global spatial variation in the residual resistance risk after allowing for usage density.

CONCLUSIONS

There were clustered hot-spots and a significant global spatial variation in the residual resistance risk after allowing for usage density. The usage density of 5-9 CIP DDDs per 1,000 inhabitants within the same influence zone was the resistance triggering level. This level led to E. coli resistance clustering, proving that individual resistance emergence and dissemination was affected by antimicrobial population consumption.

Are physicians with better clinical skills on licensing examinations less likely to prescribe antibiotics for viral respiratory infections in ambulatory care settings?

BACKGROUND

Viral respiratory infections (VRIs) are a common reason for ambulatory visits, and 35% are treated with an antibiotic. Antibiotic use for VRIs is not recommended, and it promotes antibiotic resistance. Effective patient-physician communication is critical to address this problem. Recognizing the importance of physician communication skills, licensure examinations were reformed in the United States and Canada to evaluate these skills.

OBJECTIVE

To assess whether physician clinical and communication skills, as measured by the Canadian clinical skills examination (CSE), predict antibiotic prescribing for VRI in ambulatory care.

RESEARCH DESIGN AND SUBJECTS

A total of 442 Quebec general practitioners and pediatricians who wrote the CSE in 1993-1996 were followed from 1993 to 2007, and their 159,456 VRI visits were identified from physician claims.

MEASURES

The outcome was an antibiotic prescription from a study physician dispensed within 7 days of the VRI visit. Multivariate logistic regression analyses were used to estimate the association between antibiotic prescribing for VRI and CSE score, adjusting for physician, patient, and encounter characteristics.

RESULTS

Better clinical and communication skills were associated with a reduction in the risk of antibiotic prescribing, but only for female physicians. Every 1-standard deviation increase in CSE score was associated with a 19% reduction in the risk of antibiotic prescribing (risk ratio, 0.81; 95% confidence interval, 0.68-0.97). Better clinical skills were associated with an even greater reduction in risk among female physicians with higher workloads (risk ratio, 0.48; 95% confidence interval, 0.29-0.79).

CONCLUSION

Physician clinical and communication skills are important determinants of antibiotic prescribing for VRI and should be targeted by future interventions.

Escaping an evolutionary lobster trap: drug resistance and compensatory mutation in a fluctuating environment

The fitness landscape concept aids intuition on adaptive evolution through low fitness genotypes. Evolutionary processes become complex when environments and therefore fitnesses fluctuate. Antibiotic resistance evolution in bacteria is an important example of such dynamics. Resistance bears a cost in the drug-free environment, but compensatory mutation can lower this cost, creating a fitness valley. With the drug present, the valley becomes a hill that is easily climbed. Once a population is dominated by resistant-compensated genotypes, reversion to sensitivity is difficult: this phenomenon has been described as an evolutionary lobster trap. With increasing frequencies of drug resistance among pathogenic bacteria, it is critical to understand how this trap can be escaped. Here, we develop stochastic models to investigate these dynamics. The residual fitness cost (the cost remaining after compensatory mutation has occurred) is a key parameter. Reversion to sensitivity is favored when the time spent in the absence of the drug relative to its presence is high compared to the residual fitness cost. Population sizes are also important: in large populations, resistant-compensated mutants appear in resistant-uncompensated or sensitive-compensated genotypes without fixation of these intermediates. This stochastic tunneling effect occurs when sufficient time is allowed by the rates of environmental fluctuation.

Probabilistic network modelling of the impact of penicillin consumption on spread of pneumococci

The worldwide increase of resistant S. pneumoniae is a growing clinical problem. In several countries, a more restrictive use of penicillin has been promoted in hope of slowing the rates of resistant pneumococci. However, the consequences of such an action on pneumococcal population dynamics are not fully understood. Thus, a network model was constructed to assess the impacts of penicillin consumption and between-strain competition on the spread of penicillin non-susceptible pneumococci. Model simulations suggest that the age distribution for carriage of penicillin non-susceptible pneumococci, in contrast to susceptible pneumococci, is affected by penicillin consumption. Furthermore, it appears extremely difficult to reduce the incidence of penicillin non-susceptible pneumococci by simply controlling penicillin consumption, assuming that reduced penicillin susceptibility does not confer a fitness cost for the organism. A more judicious use of penicillin together with control measures are in that case required to manage penicillin resistance in pneumococci.

Antibiotic selection pressure and macrolide resistance in nasopharyngeal Streptococcus pneumoniae: a cluster-randomized clinical trial

BACKGROUND

It is widely thought that widespread antibiotic use selects for community antibiotic resistance, though this has been difficult to prove in the setting of a community-randomized clinical trial. In this study, we used a randomized clinical trial design to assess whether macrolide resistance was higher in communities treated with mass azithromycin for trachoma, compared to untreated control communities.

METHODS AND FINDINGS

In a cluster-randomized trial for trachoma control in Ethiopia, 12 communities were randomized to receive mass azithromycin treatment of children aged 1-10 years at months 0, 3, 6, and 9. Twelve control communities were randomized to receive no antibiotic treatments until the conclusion of the study. Nasopharyngeal swabs were collected from randomly selected children in the treated group at baseline and month 12, and in the control group at month 12. Antibiotic susceptibility testing was performed on Streptococcus pneumoniae isolated from the swabs using Etest strips. In the treated group, the mean prevalence of azithromycin resistance among all monitored children increased from 3.6% (95% confidence interval [CI] 0.8%-8.9%) at baseline, to 46.9% (37.5%-57.5%) at month 12 (p = 0.003). In control communities, azithromycin resistance was 9.2% (95% CI 6.7%-13.3%) at month 12, significantly lower than the treated group (p < 0.0001). Penicillin resistance was identified in 0.8% (95% CI 0%-4.2%) of isolates in the control group at 1 year, and in no isolates in the children-treated group at baseline or 1 year.

CONCLUSIONS

This cluster-randomized clinical trial demonstrated that compared to untreated control communities, nasopharyngeal pneumococcal resistance to macrolides was significantly higher in communities randomized to intensive azithromycin treatment. Mass azithromycin distributions were given more frequently than currently recommended by the World Health Organization's trachoma program. Azithromycin use in this setting did not select for resistance to penicillins, which remain the drug of choice for pneumococcal infections.

TRIAL REGISTRATION

www.ClinicalTrials.gov NCT00322972. Please see later in the article for the Editors' Summary.

Antimicrobial use and indication-based prescribing among general practitioners in Eastern Croatia: comparison with data from the European Surveillance of Antimicrobial Consumption project

AIM

To investigate antibiotic consumption in a sample of physicians from Osijek-Baranja county in Eastern Croatia and to determine the volume of prescribed antimicrobials and assess the appropriateness of prescribing practices.

METHODS

Analysis of routine prescribing data was carried out in 30 primary care practices in both urban and rural communities of eastern Croatia, corresponding to a total population of 48000 patients. Prescribing practices were studied over a period of 3 years, from 2003 to 2005. Both the quantity of antimicrobials and differences and similarities between individual practitioners were analyzed.

RESULTS

Urban and rural practices did not significantly differ in regard to the volume of antimicrobials prescribed. However, significant differences were found between individual physicians. Total consumption was 17.73 defined daily doses per 1000 inhabitants per day or 6456.85 defined daily doses per 1000 inhabitants per year. The 10 most frequently used antimicrobials (93.70% of the total quantity) were amoxicillin, co-amoxiclav, co-trimoxazole, cephalexin, norfloxacin, penicillin V, azithromycin, cefuroxime, doxycycline, and nitrofurantoin. Sore throat was the most frequent reason for prescribing antibiotics.

CONCLUSION

Prescription of medicines in Osijek-Baranja county was characterized by high consumption of broad-spectrum penicillins, combined penicillins, combined sulfonamides and long-acting macrolides (azithromycin), together with disproportionately low use of doxycycline and erythromycin. The use of combined sulfonamides and azithromycin in this part of Croatia was among the highest in Europe. Great differences between prescribers in regard to indication-based prescribing have been found, and future studies should examine the factors behind these heterogeneous practices.

Impact of outpatient antibiotic use on carriage of ampicillin-resistant Escherichia coli

Studies about the relationship between antibiotic consumption and carriage of antibiotic-resistant Escherichia coli in individual patients have yielded conflicting results. The goal of this study was to identify individual- and household-level factors associated with carriage of ampicillin (AMP)-resistant E. coli during consumption of a course of oral antibiotics. We enrolled outpatients and their families in a prospective household study of AMP-resistant or AMP-susceptible E. coli carriage. Two kinds of index patients were identified. Group 1 consisted of outpatients who were being initiated on a new antibiotic course at the time of a clinic visit, and group 2 consisted of outpatients not starting antibiotics. Each participant was asked to submit three stool swab samples (at baseline, week 1, and week 4) and to complete a questionnaire. Antimicrobial susceptibility testing was performed on each phenotypically distinct E. coli colony. The study included 149 group 1 households (total, 570 participants) and 38 group 2 households (total, 131 participants). AMP-resistant E. coli was recovered from 29% of stool samples. Observed associations with antibiotic exposure varied by drug class. Penicillins, which were the most frequently prescribed drug class, were associated with a modest increase in AMP-resistant E. coli carriage and a modest decrease in AMP-susceptible E. coli carriage. Neither change by itself was statistically significant. Macrolides were associated with reduced carriage of both AMP-resistant E. coli and AMP-susceptible E. coli (P < 0.05). Both AMP-resistant and AMP-susceptible E. coli demonstrated household clustering (P < 0.001). In summary, the overall effect of antibiotics on individual risk of carriage of AMP-resistant E. coli was small. However, even a modest alteration of the competitive balance between AMP-resistant and AMP-susceptible E. coli may promote population spread of resistant E. coli. Examining changes in both resistant and susceptible organisms in antibiotic-treated individuals and their close contacts improves understanding of antibiotic selection pressure.

Prophylactic antibiotics in aesthetic surgery

Improvements in infection prevention practices over the past several decades have enhanced outcomes following aesthetic surgery. However, surgical site infections (SSI) continue to result in increased morbidity, mortality, and cost of care. The true incidence rate of SSI in aesthetic surgery is unknown due to the lack of a national surveillance system, but studies of SSI across surgical specialties have suggested that many of these infections are preventable. Patient-related factors-including obesity, glycemic control, and tobacco use-may contribute to the development of SSI following aesthetic surgery. In terms of SSI prevention, proper handwashing and surgical skin preparation are integral. Furthermore, the administration of prophylactic antibiotics has been shown to reduce SSI following many types of surgical procedures. Unfortunately, there are few large, randomized studies examining the role of prophylactic antibiotics in aesthetic surgery. The authors review the medical literature, discuss the risks of antibiotic overutilization, and detail nonpharmacological methods for reducing the risk of SSI.

Improving quinolone use in hospitals by using a bundle of interventions in an interrupted time series analysis

The objectives of the present study were to determine the effects of multiple targeted interventions on the level of use of quinolones and the observed rates of resistance to quinolones in Escherichia coli isolates from hospitalized patients. A bundle consisting of four interventions to improve the use of quinolones was implemented. The outcome was measured from the monthly levels of use of intravenous (i.v.) and oral quinolones and the susceptibility patterns for E. coli isolates from hospitalized patients. Statistical analyses were performed using segmented regression analysis and segmented Poisson regression models. Before the bundle was implemented, the annual use of quinolones was 2.7 defined daily doses (DDDs)/100 patient days. After the interventions, in 2007, this was reduced to 1.7 DDDs/100 patient days. The first intervention, a switch from i.v. to oral medication, was associated with a stepwise reduction in i.v. quinolone use of 71 prescribed daily doses (PDDs) per month (95% confidence interval [CI] = 47 to 95 PDDs/month, P < 0.001). Intervention 2, introduction of a new antibiotic guideline and education program, was associated with a stepwise reduction in the overall use of quinolones (reduction, 107 PDDs/month [95% CI = 58 to 156 PDDs/month). Before the interventions the quinolone resistance rate was increasing, on average, by 4.6% (95% CI = 2.6 to 6.1%) per year. This increase leveled off, which was associated with intervention 2 and intervention 4, active monitoring of prescriptions and feedback. Trends in resistance to other antimicrobial agents did not change. This study showed that the hospital-wide use of quinolones can be significantly reduced by an active policy consisting of multiple interventions. There was also a stepwise reduction in the rate of quinolone resistance associated with the bundle of interventions.

High prevalence of fecal carriage of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric unit in Madagascar

Background

Extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae have spread worldwide but there are few reports on carriage in hospitals in low-income countries. ESBL-producing Enterobacteriaceae (ESBL-PE) have been increasingly isolated from nosocomial infections in Antananarivo, Madagascar.

Methods

we conducted a prevalence survey in a pediatric unit from March to April 2008 Patient rectal swabs were sampled on the first and the last day of hospitalization. Medical staff and environment were also sampled. Rectal and environmental swabs were immediately plated onto Drigalski agar supplemented with 3 mg/liter of ceftriaxon.

Results

Fecal carriage was detected in 21.2% of 244 infants on admission and 57.1% of 154 on discharge, after more than 48 hours of hospitalization (p < 0.001). The species most frequently detected on admission were Escherichia coli and Klebsiella pneumoniae (36.9%), whereas, on discharge, K. pneumoniae was the species most frequently detected (52.7%). ESBL-associated resistances were related to trimethoprim-sulfamethoxazole (91.3%), gentamicin (76.1%), ciprofloxacin (50.0%), but not to amikacin and imipenem. The increased prevalence of carriage during hospitalization was related to standard antimicrobial therapy.

Conclusion

The significant emergence of multidrug-resistant enteric pathogens in Malagasy hospitals poses a serious health threat requiring the implementation of surveillance and control measures for nosocomial infections.

An engineered riboswitch as a potential gene-regulatory platform for reducing antibacterial drug resistance

Synthetic riboswitch containing aptamer is constructed in E. coli to regulate the expression of β-lactamase through small molecule-aptamer interactions, which sharply reduces the antibiotic resistance of the engineered bacteria.

Nanomedicine for respiratory diseases

Treatment of respiratory diseases and infections has proved to be a challenging task, with the incidence of these ailments increasing worldwide. Nanotechnology-based drug and gene delivery systems offer a possible solution to some of the shortfalls of the current treatment regimen. Nanobased drug delivery systems have revolutionised the field of pharmacotherapy by presenting the ability to alter the pharmacokinetics of the conventional drugs to extend the drug retention time, reduce the toxicity and increase the half-life of the drugs. Delivery of exogenous genes to the airway epithelium in vivo has been limited by several physiological barriers, resulting in the low success rate of these systems. With the advent of nanotechnology, DNA compacted with cationic polymers to produce nanoparticles has exhibited a significant increase in the transfection efficiencies. With nanoparticulate drug/gene delivery systems, specific cells can be targeted by functionalising the polymeric nanoparticles with ligands that allow the particles to dock at a specific site of the cell. In addition, polymeric systems allow for the cargo to be released in a controlled and stimuli-responsive manner. The advantages that nanoparticulate delivery systems present in the treatment of respiratory diseases and infections are summarised in this review.

Pre-dispensing of antivirals to high-risk individuals in an influenza pandemic

We consider the net benefits of pre-dispensing antivirals to high-risk individuals during an influenza pandemic, where the measure of the benefit is the number of severe outcomes (such as deaths or hospitalizations) prevented by antivirals in the whole population. One potential benefit of pre-dispensing is that individuals to whom antivirals have been pre-dispensed may be able to initiate treatment earlier than if they had to wait to obtain and fill a prescription, reducing their risk of progression to severe disease. If this benefit exceeds the side effects of misuse for the category of individuals to whom antivirals were pre-dispensed, and if antiviral supply exceeds overall population demand (which appears relevant for several countries including US in the 2009 H1N1 pandemic), pre-dispensing a quantity of antivirals not exceeding the difference between supply and demand is always beneficial. In this study, we consider the net benefits of pre-dispensing antivirals under various scenarios, including demand exceeding supply, and derive mathematical conditions under which antiviral pre-dispensing is advantageous on balance. For individuals whose relative risk of severe outcome is high enough, such as immunosuppressed individuals (particularly children) and possibly individuals with neurological disorders, pre-dispensing is always beneficial at a given level of antiviral stockpile with modest assumptions on the relative benefit of early treatment by a pre-dispensed course, regardless of the overall population demand for antivirals during the course of an epidemic. Making additional assumptions on either the overall population demand for antivirals (which appear relevant for the 2009 H1N1 pandemic) or on the relative benefit of pre-dispensing would make pre-dispensing net beneficial with inclusion of a larger number of persons such as pregnant women and morbidly obese adults.