The resistance ratchet: theoretical implications of cyclic selection pressure

Drivers of Irrational Use of Antibiotics in Europe

The unnecessary use of antibiotics and concomitant rapid growth of antibiotic resistance (ABR) is a widely acknowledged threat to global health, development, and sustainability. While the underlying cause of ABR is undoubtedly the overall volume of antibiotic use in general, irrational antibiotic use, which is influenced by several interrelated factors, is a major contributory factor. Here, we aimed to present and describe selected main drivers of irrational use of antibiotics in Europe. We performed a broad search of the current literature in databases such as PubMed, Google Scholar, Cochrane, as well as various institutional websites (World Health Organization, European Observatory, European Commission) to provide a new perspective on selected drivers of irrational antibiotic use in Europe. We also searched for relevant literature using snowballing, i.e., using reference lists of papers to identify additional papers. In this narrative review, we present that major factors among the general public driving antibiotic resistance are lack of public knowledge and awareness, access to antibiotics without prescription and leftover antibiotics, and knowledge attitude and perception of prescribers and dispensers, inadequate medical training, pharmaceutical promotion, lack of rapid and sufficient diagnostic tests, and patient⁻doctor interaction as major factors among healthcare providers. We further discuss initiatives that, if taken and implemented, can have an impact on and improve the current situation in Europe.

Evaluation of a Mixing versus a Cycling Strategy of Antibiotic Use in Critically-Ill Medical Patients: Impact on Acquisition of Resistant Microorganisms and Clinical Outcomes

Objective

To compare the effect of two strategies of antibiotic use (mixing vs. cycling) on the acquisition of resistant microorganisms, infections and other clinical outcomes.

Methods

Prospective cohort study in an 8-bed intensive care unit during 35- months in which a mixing-cycling policy of antipseudomonal beta-lactams (meropenem, ceftazidime/piperacillin-tazobactam) and fluoroquinolones was operative. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48h of admission and thrice weekly thereafter. Target microorganisms included methicillin-resistant S. aureus, vancomycin-resistant enterococci, third-generation cephalosporin-resistant Enterobacteriaceae and non-fermenters.

Results

A total of 409 (42%) patients were included in mixing and 560 (58%) in cycling. Exposure to ceftazidime/piperacillin-tazobactam and fluoroquinolones was significantly higher in mixing while exposure to meropenem was higher in cycling, although overall use of antipseudomonals was not significantly different (37.5/100 patient-days vs. 38.1/100 patient-days). There was a barely higher acquisition rate of microorganisms during mixing, but this difference lost its significance when the cases due to an exogenous Burkholderia cepacia outbreak were excluded (19.3% vs. 15.4%, OR 0.8, CI 0.5–1.1). Acquisition of Pseudomonas aeruginosa resistant to the intervention antibiotics or with multiple-drug resistance was similar. There were no significant differences between mixing and cycling in the proportion of patients acquiring any infection (16.6% vs. 14.5%, OR 0.9, CI 0.6–1.2), any infection due to target microorganisms (5.9% vs. 5.2%, OR 0.9, CI 0.5–1.5), length of stay (median 5 d for both groups) or mortality (13.9 vs. 14.3%, OR 1.03, CI 0.7–1.3).

Conclusions

A cycling strategy of antibiotic use with a 6-week cycle duration is similar to mixing in terms of acquisition of resistant microorganisms, infections, length of stay and mortality.

Antibiotic rotation strategies to reduce antimicrobial resistance in Gram-negative bacteria in European intensive care units: study protocol for a cluster-randomized crossover controlled trial

Background

Intensive care units (ICU) are epicenters for the emergence of antibiotic-resistant Gram-negative bacteria (ARGNB) because of high rates of antibiotic usage, rapid patient turnover, immunological susceptibility of acutely ill patients, and frequent contact between healthcare workers and patients, facilitating cross-transmission.

Antibiotic stewardship programs are considered important to reduce antibiotic resistance, but the effectiveness of strategies such as, for instance, antibiotic rotation, have not been determined rigorously. Interpretation of available studies on antibiotic rotation is hampered by heterogeneity in implemented strategies and suboptimal study designs. In this cluster-randomized, crossover trial the effects of two antibiotic rotation strategies, antibiotic mixing and cycling, on the prevalence of ARGNB in ICUs are determined. Antibiotic mixing aims to create maximum antibiotic heterogeneity, and cycling aims to create maximum antibiotic homogeneity during consecutive periods.

Methods/Design

This is an open cluster-randomized crossover study of mixing and cycling of antibiotics in eight ICUs in five European countries. During cycling (9 months) third- or fourth-generation cephalosporins, piperacillin-tazobactam and carbapenems will be rotated during consecutive 6-week periods as the primary empiric treatment in patients suspected of infection caused by Gram-negative bacteria. During mixing (9 months), the same antibiotics will be rotated for each consecutive antibiotic course. Both intervention periods will be preceded by a baseline period of 4 months. ICUs will be randomized to consecutively implement either the mixing and then cycling strategy, or vice versa. The primary outcome is the ICU prevalence of ARGNB, determined through monthly point-prevalence screening of oropharynx and perineum. Secondary outcomes are rates of acquisition of ARGNB, bacteremia and appropriateness of therapy, length of stay in the ICU and ICU mortality. Results will be adjusted for intracluster correlation, and patient- and ICU-level variables of case-mix and infection-prevention measures using advanced regression modeling.

Discussion

This trial will determine the effects of antibiotic mixing and cycling on the unit-wide prevalence of ARGNB in ICUs.

Trial registration

ClinicalTrials.gov NCT01293071 December 2010.

In-home Drug Storage and Self-medication with Antimicrobial Drugs in Basrah, Iraq

OBJECTIVES

To estimate the prevalence of self-medication with antimicrobial drugs and to record the stored medicine at home.

METHODS

This is a descriptive study involving a questionnaire survey to determine the extent of drug storage and self-medication. A total of 300 household units in Basrah, Iraq were including in this study. A survey was conducted in 300 households in Basrah, southern Iraq to determine the availability, source, and storage conditions of medicinal drugs and the prevalence of self medication with antimicrobials.

RESULTS

The majority of households (94%) stored drugs at home. A total of 4279 of different types of drug preparations were encountered, the mean being 14.26 products/household. The results also showed that a minority of these drugs (31%) were rationally prescribed. Hence only 31% of the total drugs were for current use, while 45% were leftovers and 23% of the drugs were kept for future use. A large proportion of the stored drugs (66%) was obtained from private pharmacies. Only 42% of all the drugs were stored appropriately. Antibiotics, as a group was the most common drug stored and used at home (26%). The results indicated that the level of education has influence over dose compliance, storage of expired drugs and drugs exchange. Furthermore, a majority of the families (78%) admitted to practicing self-medication. The most common reasons for self-medication with antimicrobial drugs were associated with influenza, upper respiratory tract infections, diarrhea and tonsillitis.

CONCLUSION

There are numerous indications of inappropriate storage, self- medication, poor compliance and use of drugs that have been kept beyond their expiry date in Basrah, Iraq.

“Future” Threat of Gram-negative Resistance in Singapore

The emergence of multidrug-resistant gram-negative bacteria is challenging the treatment of serious nosocomial infections. This is an international trend that is mirrored in Singapore too. Reports of strains resistant to all currently available agents have surfaced here and possibly have taken root here as well. The direst situation is among the non-fermenters, Pseudomonas aeruginosa and Acinetobacter baumannii. This is followed closely by the Enterobacteriaceae family with their array of extended-spectrum β-lactamases, AmpC β-lactamases and carbapenemases. There are also resistance mechanisms such as efflux pumps and porins downregulation that effect resistance against multiple classes of agents. Potentiating these developments is the dwindling “pipeline” of new agents. Hence, there is a real concern that we are running out of options for our patients. Novel antibiotic combinations, enhanced infection control, antibiotic cycling, computer-assisted programmes, and maybe in the distant future, non-antimicrobial agents is all that we have. Key words: Outcomes, Predictors, Stenotrophomonas maltophilia

Principles of antimicrobial therapy: what should we be using?

Although the use of antimicrobials has had an insurmountable impact on preventing patient morbidity and mortality, problems with antimicrobial resistance and antimicrobial-induced diarrhea are becoming more apparent in human and veterinary medicine. The mortality associated with nosocomial infection with antimicrobial-resistant bacteria in human patients is alarming. Similarly, in veterinary medicine, the morbidity and high cost of treatment of patients with postoperative infection, for example, are concerns. Specifically in equine medicine, the high morbidity and mortality associated with antimicrobial-induced diarrhea have been devastating in many equine practices. Misuse of antimicrobials is extremely common in human and veterinary medicine. All clinicians have the responsibility to consider the appropriateness of their antimicrobial use carefully and, whenever possible, to minimize antimicrobial administration to patients.

The rising impact of mathematical modelling in epidemiology: antibiotic resistance research as a case study

Mathematical modelling of infectious diseases has gradually become part of public health decision-making in recent years. However, the developing status of modelling in epidemiology and its relationship with other relevant scientific approaches have never been assessed quantitatively. Herein, using antibiotic resistance as a case study, 60 published models were analysed. Their interactions with other scientific fields are reported and their citation impact evaluated, as well as temporal trends. The yearly number of antibiotic resistance modelling publications increased significantly between 1990 and 2006. This rise cannot be explained by the surge of interest in resistance phenomena alone. Moreover, modelling articles are, on average, among the most frequently cited third of articles from the journal in which they were published. The results of this analysis, which might be applicable to other emerging public health problems, demonstrate the growing interest in mathematical modelling approaches to evaluate antibiotic resistance.

Antimicrobial drugs in the home, United Kingdom

Persons more knowledgeable about these drugs are more likely to keep them.

A total of 6% of 6,983 households in the United Kingdom had leftover antimicrobial drugs, and 4% had standby antimicrobial drugs. Respondents with leftover drugs were more educated, more knowledgeable about antimicrobial drugs, younger, and female. Of respondents with leftover drugs, 44% kept them in case of future need, and 18% had taken these drugs without medical advice.

Antimicrobial stewardship

Antimicrobial stewardship is a key component of a multifaceted approach to preventing emergence of antimicrobial resistance. Good antimicrobial stewardship involves selecting an appropriate drug and optimizing its dose and duration to cure an infection while minimizing toxicity and conditions for selection of resistant bacterial strains. Studies conducted over the years indicate that antibiotic use is unnecessary or inappropriate in as many as 50% of cases in the United States, and this creates unnecessary pressure for the selection of resistant species. Because the pharmaceutical industry pipeline for new antibiotics has been curtailed in recent years, and it may be > or = 10 years before important new antibiotics to treat certain resistant bacteria find their way to market, a premium has been set on maintaining the effectiveness of currently available agents. Several strategies, including prescriber education, formulary restriction, prior approval, streamlining, antibiotic cycling, and computer-assisted programs have been proposed to improve antibiotic use. Although rigorous clinical data in support of these strategies are lacking, the most effective means of improving antimicrobial stewardship will most likely involve a comprehensive program that incorporates multiple strategies and collaboration among various specialties within a given healthcare institution. Computer-assisted software programs may be especially useful in implementing these comprehensive programs. The antimicrobial stewardship program at the Hospital of the University of Pennsylvania, which has been shown to improve appropriateness of antibiotic use and cure rates, decrease failure rates, and reduce healthcare-related costs, is used as an example in support of this multifaceted, multidisciplinary approach. At this time, data from well-controlled studies examining the effect of antibacterial stewardship on emergence of resistance are limited, but available data suggest that good antibiotic stewardship reduces rates of Clostridium difficile-associated diarrhea, resistant gram-negative bacilli, and vancomycin-resistant enterococci.

Antimicrobial stewardship

Antimicrobial stewardship is a key component of a multifaceted approach to preventing emergence of antimicrobial resistance. Good antimicrobial stewardship involves selecting an appropriate drug and optimizing its dose and duration to cure an infection while minimizing toxicity and conditions for selection of resistant bacterial strains. Studies conducted over the years indicate that antibiotic use is unnecessary or inappropriate in as many as 50% of cases in the United States, and this creates unnecessary pressure for the selection of resistant species. Because the pharmaceutical industry pipeline for new antibiotics has been curtailed in recent years, and it may be >/=10 years before important new antibiotics to treat certain resistant bacteria find their way to market, a premium has been set on maintaining the effectiveness of currently available agents. Several strategies, including prescriber education, formulary restriction, prior approval, streamlining, antibiotic cycling, and computer-assisted programs have been proposed to improve antibiotic use. Although rigorous clinical data in support of these strategies are lacking, the most effective means of improving antimicrobial stewardship will most likely involve a comprehensive program that incorporates multiple strategies and collaboration among various specialties within a given healthcare institution. Computer-assisted software programs may be especially useful in implementing these comprehensive programs. The antimicrobial stewardship program at the Hospital of the University of Pennsylvania, which has been shown to improve appropriateness of antibiotic use and cure rates, decrease failure rates, and reduce healthcare-related costs, is used as an example in support of this multifaceted, multidisciplinary approach. At this time, data from well-controlled studies examining the effect of antibacterial stewardship on emergence of resistance are limited, but available data suggest that good antibiotic stewardship reduces rates of Clostridium difficile-associated diarrhea, resistant gram-negative bacilli, and vancomycin-resistant enterococci.

Mathematical model--tell us the future!

Studying bacterial resistance has direct importance for the antimicrobial treatment of individual patients. In addition, surveillance data pooled from individual diagnostic reports help physicians to choose the most effective drug for empirical therapy. However, this is not the limit of what can be done with the resistance data. There is an increasing need to synthesize the available strands of data in order to construct mathematical models that can be used as tools to predict the likely outcomes of various antibiotic policy options.