The effect of changes in the consumption of macrolide antibiotics on erythromycin resistance in group A streptococci in Finland. Finnish Study Group for Antimicrobial Resistance

Bacterial resistance: origins, epidemiology, and impact

The basic mechanisms of antibacterial resistance are well known, but critical new aspects continue to be discovered. Recently discovered factors with major implications for the emergence, dissemination, and maintenance of resistance include multidrug efflux, hypermutability, integrons, and plasmid addiction. Some resistances are widespread and others local, with prevalence rates often worst in newly prosperous countries and in those specialist units where antibacterial use is heaviest. Multidrug-resistant epidemic strains are critical to the total accumulation of resistance (e.g., among Streptococcus pneumoniae, methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae), but it remains unclear why some bacterial lineages achieve epidemic spread whereas others that are equally resistant do not. The correlation between in vitro resistance and treatment failure is imperfect, but resistance undoubtedly increases mortality, morbidity, and costs in many settings. Recent concern has led to a plethora of governmental and agency reports advocating less antibacterial use, better antibacterial use, better infection control, and the development of new antibacterials. The evidence that better prescribing can reduce resistance rates is mixed, and although changes to hospital regimens may reduce one resistance problem, other opportunistic bacteria may fill the vacant niche. Overall, the best that can reasonably be anticipated is an improved balance between the accumulation of resistance and new antibacterial development.

Antibiotic use and Escherichia coli resistance trends for quinolones and cotrimoxazole in Sweden

Resistance rates among Escherichia coli isolates for quinolones and cotrimoxazole were analysed at 12 Swedish hospitals, and compared with antibiotic use. Resistance figures for E. coli were retrieved from the diagnostic microbiology service databases for the period 1989-99, and antibiotic sales figures were obtained from the National Corporation of Swedish Pharmacies. At the 2 university teaching hospitals included, norfloxacin resistance of E. coli increased significantly (p < 0.001) from 0% to 2.7% and 2.5%, respectively. Ciprofloxacin resistance increased (p < 0.001) in parallel. Quinolone use increased until 1992; subsequently, sales have remained at a stable level. The increase in norfloxacin and ciprofloxacin resistance started relatively simultaneously in all hospitals, around 1991. Cotrimoxazole resistance has also been increasing significantly in most hospitals, in spite of decreasing sales of cotrimoxazole and trimethoprim. Similar trends could be seen in blood isolates from the same hospitals for the period 1991-98. Clinical laboratory data are subject to bias but surveillance over longer periods of time provides a useful method for detecting trends in increasing resistance and therefore functions as a resistance warning system.

Agreement between patient self-report and a Veterans Affairs national pharmacy database for identifying recent exposures to antibiotics

PURPOSE

The dramatic rise in antibiotic drug resistance among community pathogens has stimulated interest in the epidemiological relationship between antibiotic exposure and drug resistance. In assessing the strength of this relationship, studies are hampered by the lack of data on the accuracy of subject self-report of antibiotic exposure. The authors compared self-report with pharmacy dispensing data to determine the accuracy of self-reported antibiotic exposure.

METHODS

The study design was a cross-sectional survey of veterans seen at the Philadelphia Veterans Affairs (VA) Medical Center in 1999 and 2000. Subjects reported exposures to antibiotics, antihypertensive drugs and nonsteroidal anti-inflammatory drugs through a structured telephone interview. The instrument included open-ended questions, condition-specific prompts and drug-specific prompts. Subject responses were linked to a national VA pharmacy database that served as the reference standard for evaluating self-reported exposures.

RESULTS

The authors found that the sensitivity of self-report of antibiotic exposure increased with increasing use of prompts. A comprehensive assessment of antibiotic exposure identified 73% of antibiotic exposures, compared to 73% of antihypertensive drug exposures and 92% of nonsteroidal anti-inflammatory drug exposures.

CONCLUSIONS

Assessment of antibiotic exposure appears to be comparable to assessment of other chronic and episodic drugs. Multistep assessment of exposure improves the sensitivity of assessment.

Moving from recommendation to implementation and audit: part 1. Current recommendations and programs: a critical commentary

Growing concern over the spread of resistance to antibiotics and other antimicrobials has prompted a plethora of recommendations for its control. Strategic programs for resistance containment have been initiated in various countries, particularly in Western Europe and North America. The World Health Organization and the European Union have responded to the need for international action by publishing guidance and encouraging collaboration. These recommendations rightly focus on controlling resistance in the community. They agree on the importance of surveillance of resistance patterns and antibiotic usage and the need to encourage judicious antibiotic usage (especially through education of prescribers and the public). Yet there remains a pressing need for the implementation of effective actions to address these issues. Important considerations given less attention include infection prevention (e.g. through immunization), the use of rapid diagnostic tests to reduce antibiotic usage, audit of implemented actions, and the provision of feedback. Furthermore, research is necessary to fill the substantial gaps in our knowledge. Notably, the reversibility or containment of resistance with the optimization of antibiotic usage has yet to be definitely established. For now, antimicrobial management programs should focus on ensuring the most appropriate use of antimicrobials rather than simply on limiting choices. Finally, developed countries must recognize that a truly global approach to resistance containment will require greater support for developing countries.

A critical assessment of published guidelines and other decision-support systems for the antibiotic treatment of community-acquired respiratory tract infections

Guidelines are an important means by which professional associations and governments have sought to improve the quality and cost-effectiveness of disease management for infectious diseases. Prescribing of initial antibiotic therapy for community-acquired respiratory tract infections (RTIs) is primarily empiric and physicians may often have a limited appreciation of bacterial resistance. Recent guidelines for managing RTIs have adopted a more evidence-based approach. This process has highlighted important gaps in the existing knowledge base, e.g. concerning the impact of resistance on the effectiveness of oral antibiotics for outpatient community-acquired pneumonia and the level of resistance that should prompt a change in empiric prescribing. In upper RTIs, the challenge is to identify patients in whom antibiotic therapy is warranted. Concentrated, sustained efforts are needed to secure physicians' use of guidelines. The information should be distilled into a simple format available at the point of prescribing and supported by other behavioral change techniques (e.g. educational outreach visits). Advances in information technology offer the promise of more dynamic, computer-assisted forms of guidance. Thus, RTI prescribing guidelines and other prescribing support systems should help control bacterial resistance in the community. However, their effect on resistance patterns is largely unknown and there is an urgent need for collaborative research in this area. Rapid, cost-effective diagnostic techniques are also required and new antibiotics will continue to have a role in disease management.

Surveillance of resistance in bacteria causing community-acquired respiratory tract infections

Bacterial resistance to antibiotics in community-acquired respiratory tract infections is a serious problem and is increasing in prevalence world-wide at an alarming rate. Streptococcus pneumoniae, one of the main organisms implicated in respiratory tract infections, has developed multiple resistance mechanisms to combat the effects of most commonly used classes of antibiotics, particularly the beta-lactams (penicillin, aminopenicillins and cephalosporins) and macrolides. Furthermore, multidrug-resistant strains of S. pneumoniae have spread to all regions of the world, often via resistant genetic clones. A similar spread of resistance has been reported for other major respiratory tract pathogens, including Haemophilus influenzae, Moraxella catarrhalis and Streptococcus pyogenes. To develop and support resistance control strategies it is imperative to obtain accurate data on the prevalence, geographic distribution and antibiotic susceptibility of respiratory tract pathogens and how this relates to antibiotic prescribing patterns. In recent years, significant progress has been made in developing longitudinal national and international surveillance programs to monitor antibiotic resistance, such that the prevalence of resistance and underlying trends over time are now well documented for most parts of Europe, and many parts of Asia and the Americas. However, resistance surveillance data from parts of the developing world (regions of Central America, Africa, Asia and Central/Eastern Europe) remain poor. The quantity and quality of surveillance data is very heterogeneous; thus there is a clear need to standardize or validate the data collection, analysis and interpretative criteria used across studies. If disseminated effectively these data can be used to guide empiric antibiotic therapy, and to support-and monitor the impact of-interventions on antibiotic resistance.

Investigation of risk factors for tonsillopharyngitis with macrolide resistant Streptococcus pyogenes in Turkish children

BACKGROUND

Streptococcus pyogenes is the most important causative agent of tonsillopharyngitis. Although penicillin is the drug of choice in streptococcal tonsillopharyngitis, macrolides are recommended drugs in patients who have an allergy to penicillin. However, resistance to macrolides is an important problem in some regions of the world. Risk factors for resistance development have not been investigated sufficiently.

OBJECTIVES

To investigate the risk factors for the development of tonsillopharyngitis with macrolide resistant S. pyogenes.

METHODS

Three hundred and forty-five children with tonsillopharyngitis caused by S. pyogenes were investigated for various risk factors. Streptococcus pyogenes isolated from children's throat culture were examined for erythromycin, clarithromycin and azithromycin susceptibility.

RESULTS

Two hundred and sixty-three children were found eligible for the analysis of risk factors. Resistances to erythromycin, clarithromycin and azithromycin were detected as 3.8, 4.2 and 4.2%, respectively. Macrolide use of the family members in the last 3 months (odds ratio = 7.04, P = 0.005) has been determined to be a risk factor for the development of tonsillopharyngitis with macrolide resistant S. pyogenes.

CONCLUSION

Restriction of macrolide antibiotic use appears to be the most important measure to prevent the development of tonsillopharyngitis with resistant S. pyogenes.

Impact of an antibiotic policy on antibiotic use in a paediatric department. Individual based follow-up shows that antibiotics were chosen according to diagnoses and bacterial findings

Guidelines and clinical Cupertino for rational antibiotic use were implemented in a Norwegian paediatric department in 1994. From 1994 to 1998 the use of antibiotics and expenditures was reduced by 50%. There was an 80% decrease in the use of cloxacillin, a 74% decrease of aminoglycosides and a 59% decrease of cephalosporins. The use of penicillin V and G increased by 14% and ampicillins by 8%. Eight point prevalence studies showed that on average 23% (range 21-38%) of the patients were treated with antibiotics. Penicillins were used in 44% of courses, aminoglycosides in 35% of courses and cephalosporins in 9% of courses. Treatment was mostly adjusted to bacteriological findings. Compliance with guidelines was >90%. Guidelines for rational antibiotic policy and multidisciplinary co-operation lead to reduction in the use and expenses of antibiotics in a paediatric department.

Formulations of antibiotics for children in primary care: effects on compliance and efficacy

This review article is designed for pediatricians as well as primary care physicians in the outpatient setting as a clinical guide to antibiotic selection. It emphasizes variables related to compliance as well as efficacy. The aim is to give recommendations as to the choice of antibiotics, depending on factors such as taste, cost, efficacy, and compliance. Common bacterial pathogens causing infections in children are reviewed, along with their susceptibility patterns to antimicrobial agents. Emerging mechanisms of resistance, particularly the increasing resistance of pneumococci to beta-lactam antibiotics, are discussed because of their importance to antibiotic selection. Previously published studies that have examined the treatment of common outpatient infections in children, such as otitis media, streptococcal tonsillopharyngitis, and sinusitis, are summarized. Adverse reactions associated with antibiotics, second in importance only to efficacy, are reviewed. Finally, compliance issues, which include palatability, cost, duration of therapy, and administration frequency, are analyzed using recently published information related to each of these issues. The efficacy of the commonly used antibiotics for urinary tract infections, pneumonia, and streptococcal pharyngitis does not vary significantly; however, for otitis media and sinusitis, some studies have shown that treatment efficacy with the antibiotic does not vary significantly from that with placebo. Likewise, adverse reactions rarely provide a basis for antibiotic selection, since virtually all antibiotics are generally well tolerated. The final factor, compliance, is a major issue in determining both first- and second-line therapy of common outpatient infections in children. Although cost is not a factor in compliance in countries such as the UK where no copayment is required for pediatric drugs, it is of major importance in the US. This is followed by palatability, administration duration and finally administration frequency. As a group, cephalosporins are generally the best tasting but are relatively more expensive than macrolides. Antibiotics that can be given for 5 days, and just once or twice daily, are preferred by most parents and physicians. Since final assessment of antibiotic choice is likely to vary considerably among healthcare personnel, decisions must be made on an individual basis.

Decreased number of antibiotic prescriptions in office-based settings from 1993 to 1999 in children less than five years of age

OBJECTIVE

Increasing rates of antibiotic resistance have stimulated efforts to decrease antibiotic use. To assess the success of these efforts, we analyzed antibiotic prescribing trends in children younger than 5 years old, the group with the highest use, from 1993 to 1999.

METHODS

Data from the National Ambulatory Medical Care Survey were analyzed to determine antibiotic prescribing patterns for office-based visits from 1993 to 1999 for children <5 years old. Data were stratified by US regions, patient's race and gender. Antibiotic prescription rates per 1,000 population were calculated with population data from the US Census Bureau as the denominator. Specific prescribing of penicillins, cephalosporins, macrolides and sulfas was also assessed.

RESULTS

Overall antibiotic prescribing in the office-based setting peaked in 1995 at 1,191 antibiotic courses per 1,000 children, then declined to 698 per 1,000 in 1999, a decrease of 41%. Antibiotic prescribing was consistently higher in whites than blacks; however, declines in prescribing over time were observed in both groups. Although there was wide regional variation in antibiotic prescribing in the early 1990's, by the late 1990's prescribing rates were similar in all regions. Prescriptions for penicillins and cephalosporins combined comprised 77 and 70% of total prescriptions during 1993 to 1997 and 1998 to 1999, respectively. Macrolide prescriptions reached a nadir during 1993 to 1997, accounting for 9% of the total, but increased to 16% during 1998 to 1999.

CONCLUSION

Since 1995 the rates of antibiotic prescriptions in children <5 years of age have declined substantially. At the same time changes have occurred in the types of antibiotics prescribed. It appears that efforts to reduce antibiotic use have been successful. Whether this decrease in use will be accompanied by lower rates of antibiotic resistance will need to be determined.

Biological cost of rifampin resistance from the perspective of Staphylococcus aureus

Resistance determinants that interfere with normal physiological processes in the bacterial cell usually cause a reduction in biological fitness. Fitness assays revealed that 17 of 18 in vitro-selected chromosomal mutations within the rpoB gene accounting for rifampin resistance in Staphylococcus aureus were associated with a reduction in the level of fitness. There was no obvious correlation between the level of resistance to rifampin and the level of fitness loss caused by rpoB mutations. Among 23 clinical rifampin-resistant S. aureus isolates from six countries, only seven different rpoB genotypes could be identified, whereby the mutation 481His-->Asn was present in 21 (91%) of these 23 isolates. The mutation 481His-->Asn, in turn, which confers low-level rifampin resistance on its own, was not shown to be associated with a cost of resistance in vitro. The restriction to distinct mutations that confer rifampin resistance in vivo, as demonstrated here, appears to be determined by the Darwinian fitness of the organisms.

Over-the-counter acquisition of antibiotics in the Maltese general population

Few studies have studied the frequency of over-the-counter acquisition of antibiotics in western countries. In order to provide an insight into these practices in Malta, attitudes towards antibiotic use in the general public were researched through a structured interview. Nineteen percent admitted that they took antibiotics without prescription and 11% of parents replied that they had given antibiotics to their children without prescription. These antibiotics were mainly self-administered for upper respiratory tract symptoms, particularly sore throat, with community pharmacies being the major source in more than 85% of cases. The study indicates the need for an educational campaign on proper antibiotic use amongst the Maltese general public.

Impact of drug policy on the use of parenteral cephalosporins in Italy

OBJECTIVE

To evaluate the effects of the 1998 revision of CUF Note 55 on doctors' prescribing behaviour and drug costs with regard to intramuscularly administered cephalosporins.

METHOD

National data on drug use between January 1998 and June 2000 were provided by the Drug Utilisation Monitoring Centre of the Ministry of Health. The Anatomic Therapeutic Chemical classification and the Defined Daily Dose methodology, as well as population estimates obtained from the Italian National Statistics Institute were used to define consumption as the number of defined daily doses per 1000 inhabitants per day. The cost of these antibiotic medications was determined using the wholesale price reported in Informatore Farmaceutico. Italian inflation rates were used to annuitize the expenditure. "STATA 6.0" software was used for all statistical analyses.

RESULTS

The use of cefonicid rose dramatically after the revision (+ 136.3%), whereas the utilisation of the other active ingredients decreased. A decrease of 5.6% in the expenditure for all parenteral cephalosporins was observed in this period while the same figure increased by 2.3% after one year.

CONCLUSION

The exclusion of cefonicid from a restricted list appears to have significantly affected doctors' prescribing practices, while the effect on drug expenditure was contradictory.

Cross-cultural differences in lay attitudes and utilisation of antibiotics in a Belgian and a Dutch city

Cultural differences are probably an important factor in the considerable variation in antibiotic use between countries. The objective of this study was to explore local cultural differences in the lay perspective on coping with URTD and using antibiotics. We interviewed 30 persons in a Dutch and a Belgian city. Twenty-one were interviewed a second time after 3 months. Between the first and second interview, they noted in a diary all URTD episodes experienced by themselves and their family members (N=69) and how they coped with them. The Dutch participants labelled most URTD episodes as "common cold" or "flu". The Flemish participants labelled most of their URTD episodes as "bronchitis" and used more antibiotics. Four categories of antibiotic users could be distinguished. Participants with a Protestant background were more sceptical about medicines than those with a Catholic background. A thorough understanding of the cultural context is necessary to design effective campaigns to promote rational antibiotic use.

Narrow versus broad spectrum antibacterials: factors in the selection of pneumococcal resistance to beta-lactams

Streptococus pneumoniae represents an interesting model to discuss the relative impact of broad versus narrow spectrum antibacterials as potential selectors for resistance. Indeed, this pathogen is responsible for potentially severe infections in the community, and has a great capacity for acquisition of resistance to antibacterial agents. It has been the focus of many studies to elucidate some unique aspects of molecular biology, including the adaptive mechanisms responsible for emergence and spread of multiresistance. In the past, the use of narrow spectrum agents was recommended in order to try to reduce the risk of selection of resistance. This concept is nowadays somewhat obsolete for several reasons. S. pneumoniae is able to acquire resistance to antibacterials belonging to different families of drugs through different molecular mechanisms. Thus, selection of multiresistant pneumococci can result from exposure to very different agents, including narrow spectrum as well as broad spectrum agents. In vitro studies have shown a different potential for selection of resistance among the beta-lactam agents. Furthermore, several studies have more or less directly established a close relationship between the level of antibacterial use and the rate of selection of resistance. In addition to the overall amount of antibacterials prescribed in the community, several other factors have been shown to influence the rate of selection of resistance, including the use of doses that are too low, the length of therapy and the duration of bacterial exposure to long-acting agents compared to drugs with short half-lives. Therefore, there are three main ways to control selection and spread of resistant strains: by (i) reducing the amount of antibacterials used; (ii) using optimal dosages (avoiding underdosing) and treatments of short duration; and (iii) reducing the risk of transmission among young children attending daycare centres or kindergartens. In order to help physicians reduce the number of unnecessary prescriptions, it is important to develop rapid tests to recognise the bacterial origin of a febrile illness and even more important to detect resistance to antibacterials. However, apart from rapid diagnostic tests for streptococcal pharyngitis, those tests are not currently available. As a consequence, currently, the debate around narrow versus broad spectrum antibacterials remains a false debate. Physicians should use broad spectrum agents in many instances of upper or lower respiratory tract infection, taking into consideration the probable pathogens and the risk of (multi)resistance to antibacterials. Once rapid diagnostic are available in community practice, allowing a precise diagnosis of the offending agent and its susceptibility profile, physicians will be able to add to their current criteria the selective potential for resistance of the antibacterials that appear to be active in vitro.

Adverse and beneficial secondary effects of mass treatment with azithromycin to eliminate blindness due to trachoma in Nepal

Mass administration of azithromycin to eliminate blindness due to trachoma has raised concerns regarding the emergence of antimicrobial resistance. During 2000, we compared the antimicrobial resistance of nasopharyngeal pneumococcal isolates recovered from and the prevalence of impetigo, respiratory symptoms, and diarrhea among 458 children in Nepal before and after mass administration of azithromycin. No azithromycin-resistant pneumococci were isolated except from 4.3% of children who had received azithromycin during 2 previous mass treatments (P<.001). There were decreases in the prevalence of impetigo (from 14% to 6% of subjects; adjusted odds ratio [OR], 0.41; 95% confidence interval [CI], 0.21-0.80) and diarrhea (from 32% to 11%; adjusted OR, 0.26; 95% CI, 0.14-0.43) 10 days after azithromycin treatment. The absence of macrolide-resistant isolates after 1 mass treatment with azithromycin is encouraging, although the recovery of azithromycin-resistant isolates after 2 mass treatments suggests the need for resistance monitoring when multiple rounds of antimicrobial treatment are given.

Pharmacoepidemiological analysis of provincial differences between consumption of macrolides and rates of erythromycin resistance among Streptococcus pyogenes isolates in Spain

The M phenotype is by far the most common mechanism of erythromycin resistance among Streptococcus pyogenes isolates in Spain. A geographic analysis of the relationship between within-country differences in the prevalence of M-type resistance to erythromycin in S. pyogenes and the level of consumption of 14- and 15-membered macrolides within different provinces was carried out. From 1998 to 1999, a nationwide multicenter surveillance study yielded 2,039 consecutive pharyngeal isolates of S. pyogenes. Data on antibiotic consumption for the same period were gathered from IMS Health, and the corresponding daily defined doses per 1,000 inhabitants per day were calculated according to the Anatomic Therapeutic Classification index. Macrolide use was subdivided into dosages given three times a day (TID), twice a day (BID), or once a day (OD). Spearman nonparametric correlation coefficients (R) were calculated, and variables proving to be significantly associated (P < 0.1) were introduced into a linear regression model. The total consumption of macrolides presented a significant correlation with the prevalence of resistance (R = 0.527; P = 0.032). Neither TID nor BID macrolide consumption showed significant correlations. Only OD consumption had a significance below 0.1. These data are consistent with the hypothesis that only the total consumption of macrolides influences the local rates of M-type erythromycin resistance in S. pyogenes, and subgroups of macrolides seem to have an additive rather than a selective effect by contributing to increasing the final amount of macrolides used. Local variations in total consumption were associated only with BID consumption (R = 0.849; P = 0.004). The simple linear regression with total macrolide consumption showed a considerable determination coefficient (R(2) = 0.678; P = 0.006). The model explains up to 68% of the measured variation and is clearly better as a predictor of the prevalence of resistance than the mere mean is. By solving the regression equation, the resultant value of 2.2 defined doses per 1,000 inhabitants per day fits with the existence of a critical threshold of selective pressure.

One-week triple vs. quadruple therapy for Helicobacter pylori infection - a randomized trial

BACKGROUND

Seven-day triple therapy including omeprazole, clarithromycin and amoxicillin has become the treatment of choice for Helicobacter pylori infection. However, 7 days of classical quadruple therapy combining omeprazole, tetracycline, metronidazole and bismuth may be an alternative to triple therapy.

AIM

To compare triple vs. quadruple therapy for H.pylori eradication.

METHODS

Three hundred and thirty-nine patients with peptic ulcer and H. pylori infection were included in the study. Patients were randomized to receive omeprazole, 20 mg, amoxicillin, 1 g, and clarithromycin, 500 mg, all b.d., or omeprazole, 20 mg b.d., tetracycline chloride, 500 mg, metronidazole, 500 mg, and bismuth subcitrate, 120 mg, all t.d.s. Cure was defined as a negative urea breath test at least 2 months after treatment.

RESULTS

Per protocol and intention-to-treat cure rates were 86%[95% confidence interval (CI), 80-91%] and 77% (95% CI, 70-83%) for triple therapy, and 89% (95% CI, 82-93%) and 83% (95% CI, 76-88%) for quadruple therapy. No significant differences between the groups were found in the cure rates, compliance or side-effects.

CONCLUSION

One-week triple and quadruple therapy show similar results when used as first-line eradication treatment.

Gastrointestinal promotility drugs in the critical care setting: a systematic review of the evidence

CONTEXT

Gastrointestinal promotility agents may improve tolerance to enteral nutrition, reduce gastroesophageal reflux and pulmonary aspiration, and therefore have the potential to improve outcomes of critically ill patients.

OBJECTIVE

To systematically review and critically appraise studies of promotility agents in the critical care setting.

DATA SOURCES

Computerized bibliographic search of published research (1980-2001), citation review of relevant articles, and contact with primary investigators.

STUDY SELECTION

Randomized trials of critically ill adult patients that evaluated the effect of promotility agents on measures of gastrointestinal motility were included.

DATA EXTRACTION

Relevant methods and outcome data were abstracted in duplicate by independent investigators.

DATA SYNTHESIS

We reviewed 60 citations; 18 articles met the inclusion criteria (six studies of feeding tube placement, 11 studies evaluating gastrointestinal function, and one study of clinical outcomes). The heterogeneity of study methods and outcomes measured precluded a quantitative synthesis of the data. Although there are conflicting studies, the larger and more methodologically robust studies suggest that metoclopramide has no effect on feeding tube placement. Erythromycin has been shown to increase success rates with small-bowel tube placement in two studies. Eight of ten studies evaluating the effect of cisapride, metoclopramide, or erythromycin on measures of gastrointestinal transit demonstrated positive effects; the two studies that did not were relatively small (n = 27 and 10) and likely had inadequate power to detect a difference in treatment effect. No study demonstrated a positive effect on clinical outcomes.

CONCLUSIONS

As a class of drugs, promotility agents appear to have a beneficial effect on gastrointestinal motility in critically ill patients. A one-time dose of erythromycin may facilitate small-bowel feeding tube insertion. Administration of metoclopramide appears to increase physiologic indexes of gastrointestinal transit and feeding tolerance. Concerns about safety and lack of effect on clinically important outcomes preclude strong treatment recommendations.

Resistance determinants and clonal diversity in group A streptococci collected during a period of increasing macrolide resistance

Susceptibility to macrolides and lincosamides was investigated with 299 consecutive nonduplicate Streptococcus pyogenes clinical isolates collected over a 6-year period (1992 to 1997) from an area of central Italy. During this period, macrolide resistance rates steadily increased (from 9% in 1992 to 53% in 1997; P < 0.001). The increase was caused by isolates with a macrolide-lincosamide-streptogramin B resistance phenotype, carrying mostly erm(B) but also erm(TR) genes, that were not detected in the first 2 years and were detected with increasing prevalence (8, 5, 26, and 37%, respectively) during the following 4 years. During the same period, the prevalence of isolates with a macrolide resistance phenotype, carrying mef(A) determinants, did not vary significantly; on average it was 13%, with modest rate fluctuations in different years and no definite trend. Molecular typing revealed a remarkable clonal diversity among susceptible and resistant isolates and a notable heterogeneity of the genetic environment of the resistance genes. The analysis of clonal diversity in relation with resistance phenotypes and genotypes revealed that increased macrolide resistance rates were due to a complex interplay of different mechanisms, with a relevant contribution played by an "epidemic" spread of genetic elements carrying the erm(B) gene among the circulating streptococcal population.

Human diseases caused by foodborne pathogens of animal origin

Many lines of evidence link antimicrobial-resistant human infections to foodborne pathogens of animal origin. Types of evidence reviewed include: (1) direct epidemiologic studies; (2) temporal evidence; (3) additional circumstantial evidence; (4) trends in antimicrobial resistance among Salmonella isolates; and (5) trends in antimicrobial resistance among other pathogens, such as Campylobacter jejuni. Commensal microorganisms in animals and humans may contribute to antimicrobial resistance among pathogens that cause disease among humans. For instance, enterococci of food-animal origin, particularly strains that are vancomycin resistant, have been linked to strains found in the human gastrointestinal tract. The latent period between the introduction of a given antimicrobial and emergence of resistance varies considerably, but once the prevalence in a population reaches a certain level, control becomes extremely difficult.

Emergence of group A streptococcus strains with different mechanisms of macrolide resistance

The mechanisms of resistance to macrolides in seven group A streptococcal (Streptococcus pyogenes) isolates that were the cause of pharyngitis in children who were unsuccessfully treated with azithromycin (10 mg/kg of body weight/day for 3 days) were evaluated. All posttreatment strains were found to be genetically related to the pretreatment isolates by random amplified polymorphism DNA analysis and pulsed-field gel electrophoresis. Two isolates had acquired either a mef(A) or an erm(B) gene, responsible for macrolide efflux and ribosomal modification, respectively. Three isolates displayed mutations in the gene encoding the L4 ribosomal protein that is part of the exit tunnel within the 50S subunit of the bacterial ribosome. In the two remaining posttreatment strains, the mechanisms of macrolide resistance could not be elucidated.

Exploring the variability in antibiotic prescribing profiles among paediatricians from two different areas of Italy

We carried out a multicentre community-based study in order to describe the antibiotic therapeutic approach of paediatricians from two different areas of Italy in the treatment of respiratory tract infection (RTIs), and to assess which factors are involved in a possible variability of prescribing habits. Forty paediatricians participated in the study between October 1998 and April 1999. They had to complete a questionnaire for each therapeutic intervention resulting in an antibiotic prescription. A logistic regression model was used to identify possible predictors in choosing parenteral antibiotics for the treatment of RTIs. In 2 975 questionnaires of antibiotic treatment, RTIs represented 90.2% of the total antibiotics used. Upper respiratory tract infections were the most commonly treated diagnostic group (59.6%), followed by lower respiratory tract infections (20.4%), and middle ear infections (19.8%). Statistically significant differences between northern and southern Italy were reported in the antibiotic prescription profile and the duration of the therapy. Another marked difference was reported in the frequency of laboratory analysis requests. The logistic regression model indicated that the use of parenteral antibiotics appears significantly related to the type of infections [lower RTIs: (OR: 3.99; 95% CI: 2.49-6.37)], the geographic location [northern Italy: (OR: 0.20; 95% CI: 0.20-0.39)], and the presence of concurrent diseases (OR: 3.21; 95% CI: 1.46-7.02). The lack of adherence to clinical guidelines and the marked variability of antibiotic prescription rates between different areas of the country appear to be related to factors other than bacterial resistance, and highlight the importance of carrying out educational programmes targeted at the national level for improving the antibiotic prescription habits for the treatment of RTIs.

Mechanisms of antimicrobial resistance: their clinical relevance in the new millennium

Antimicrobials show selective toxicity. Suitable targets for antimicrobials to act at include the bacterial cell wall, bacterial protein and folic acid synthesis, nucleic acid metabolism in bacteria and the bacterial cell membrane. Acquired antimicrobial resistance generally can be ascribed to one of five mechanisms. These are production of drug-inactivating enzymes, modification of an existing target, acquisition of a target by-pass system, reduced cell permeability and drug removal from the cell. Introduction of a new antimicrobial into clinical practice is usually followed by the rapid emergence of resistant strains of bacteria in some species that were initially susceptible. This has reduced the long-term therapeutic value of many antimicrobials. It used to be thought that antibacterial resistance was mainly a hospital problem but now it is also a major problem in the community. Organisms in which resistance is a particular problem in the community include members of the Enterobacteriaceae, including Salmonella spp. and Shigella spp., Mycobacterium tuberculosis, Streptococcus pneumoniae, Haemophilus influenzae and Neisseria gonorrhoeae. Multi-resistant Gram-negative rods, methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci are major causes of concern in the hospital setting. Prevalence of antibacterial resistance depends both on acquisition and spread. Decreasing inappropriate usage of antimicrobials should lessen the rate of acquisition, and spread can be minimised by sensible infection control measures.

Macrolide resistance mechanisms in Gram-positive cocci

Two principal mechanisms of resistance to macrolides have been identified in Gram-positive bacteria. Erythromycin-resistant methylase is encoded by erm genes. Resultant structural changes to rRNA prevent macrolide binding and allow synthesis of bacterial proteins to continue. Presence of the erm gene results in high-level resistance. Modification of the mechanism whereby antibiotics are eliminated from the bacteria also brings about resistance. Bacteria carrying the gene encoding macrolide efflux (i.e. the mefE gene) display relatively low-level resistance. Azithromycin, because of its ability to achieve concentrations at sites of infections, is capable of eradicating mefE-carrying strains. Other resistance mechanisms, involving stimulation of enzymatic degradation, appear not to be clinically significant.

Erythromycin-resistant group A streptococci in schoolchildren in Pittsburgh

BACKGROUND

Resistance to erythromycin has been very uncommon among group A streptococci in the United States.

METHODS

As part of a longitudinal study, we obtained surveillance throat cultures twice monthly and with each new respiratory tract illness from children in kindergarten through grade 8 at one school in Pittsburgh. Screening for resistance to erythromycin and clindamycin was initially accomplished with use of the Kirby-Bauer disk-diffusion test. The minimal inhibitory concentration of resistant isolates was determined by the E test. A double disk-diffusion test was used to characterize the resistance phenotype, and the polymerase-chain-reaction assay was used to identify the resistance gene. The molecular relatedness of strains was determined by field-inversion gel electrophoresis.

RESULTS

A total of 1794 throat cultures were obtained from 100 children between October 2000 and May 2001, of which 318 cultures (18 percent) from 60 of the children were positive for group A streptococci. Forty-eight percent of these isolates (153 of 318) were resistant to erythromycin. None were resistant to clindamycin. Results of the double disk-diffusion test indicated the presence of the M phenotype of erythromycin resistance. Molecular typing indicated that the outbreak was due to a single strain of group A streptococci. Of 100 randomly selected isolates of group A streptococci obtained from the community between April and June 2001, 38 were resistant to erythromycin.

CONCLUSIONS

In January 2001, during a longitudinal study of schoolchildren, we detected the emergence of erythromycin resistance in pharyngeal isolates of group A streptococci. This clonal outbreak also affected the wider community.

Comparison of two dosages of azithromycin for three days versus penicillin V for ten days in acute group A streptococcal tonsillopharyngitis

BACKGROUND

Three-day, 10 mg/kg/day azithromycin (AZM) studies in pediatric acute group A streptococcal tonsillopharyngitis have shown contradictory bacteriologic results. This study investigates the efficacy and tolerability of two dosages of 3-day azithromycin (20 mg/kg/day and 10 mg/kg/day) compared with 10-day penicillin V.

METHODS

This was a prospective, comparative, randomized, multicenter trial. Children were scheduled to return for visits at 14 days (main end point) and 1 month after the onset of treatment for clinical and bacteriologic assessment. Molecular tools were used to compare pre- and posttreatment group A beta-hemolytic Streptococcus (GABHS) isolates.

RESULTS

Between November, 1997, and July, 1998, 501 patients (169 AZM 10 mg, 165 AZM 20 mg, 167 penicillin V) between 2 and 12 years old were enrolled; 500 were assessable for safety, 469 for intent to treat analysis and 420 for efficacy in the per protocol analysis. Before treatment 25 (7.9%) of 315 GABHS stains isolated from patients receiving AZM were resistant to this compound. On Day 14 pretreatment GABHS were eradicated from 78 (57.8%) of the 135 children receiving the AZM 10 mg regimen, 131 (94.2%) of the 139 receiving AZM 20 mg and 123 (84.2%) of the 146 taking penicillin. One month after the outset of treatment, bacteriologic relapses were observed in 40.5% (n = 30) of the children receiving AZM 10 mg, 14.8% (n = 18) of children taking AZM 20 mg and 13.2% (n = 15) of those treated with penicillin V. AZM 20 mg/kg/day was statistically superior to AZM 10 mg/kg/day microbiologically on Day 14 (P = 0.0001) and Day 30 (P = 0.0001) and clinically on Day 14 (P = 0.0035). AZM 20 mg/kg/day was statistically equivalent both microbiologically and clinically to standard therapy with penicillin V at all endpoints. The incidence of treatment-related adverse events was similar in the two azithromycin groups [AZM 10 mg, 31 of 169 (18.3%); AZM 20 mg, 37 of 164 (23%)] but significantly higher than those observed in the penicillin V group [5 of 166 (3%); P < 0.0001]. Most treatment-related adverse events were gastrointestinal and of mild-to-moderate severity. Fourteen patients withdrew from the trial because of adverse events (1 in the penicillin V group, 7 in the AZM 10 mg group and 6 in the AZM 20 mg group).

CONCLUSION

This is the first study to demonstrate a daily dose-dependent difference in microbiologic efficacy of a regimen; 3-day AZM 20 mg/kg/day is a more effective regimen than 3-day AZM 10 mg/kg/day for pediatric GABHS tonsillopharyngitis.

Emerging resistance to antibiotics against respiratory bacteria: impact on therapy of community-acquired pneumonia in children

Perhaps because of its etiologic complexity, community-acquired pneumonia (CAP) in infants and children remains a significant problem worldwide. Over the last few years, difficulties related to CAP treatment in children have greatly increased because of the emergence of resistance to the most widely used antibiotics against some of the bacterial pathogens involved in the development of the disease. There are few data describing the impact of antibiotic resistance on clinical outcomes in CAP, but many experts believe that the clinical impact is limited. We here discuss the prevalence of different etiologic agents in CAP of children, the diagnostic criteria, problems related to antibiotic resistance, therapeutic strategies, and future implications.

Rokitamycin: bacterial resistance to a 16-membered ring macrolide differs from that to 14- and 15-membered ring macrolides

Rokitamycin is the latest semi-synthetic 16-membered ring macrolide introduced into clinical practice. It is characterized by greater hydrophobicity, better bacterial uptake and a slower release, more cohesive ribosomal binding, and a longer post-antibiotic-effect (PAE) than can be observed with other available 14-, 15- and 16-membered ring macrolides. Rokitamycin exerts its activity on strains that harbor inducible erm genes or the efflux gene, mef(A). It has also been reported to be more active in vitro than other 16-membered ring macrolides. However, these recognized features are not fully exploited yet because current automated test procedures used in many microbiological laboratories determine susceptibility only to erythromycin or clarithromycin. Resistance to 16-membered ring macrolides cannot be predicted solely on the basis of known resistance to erythromycin or clarithromycin as revealed by an automated susceptibility assay. At least equally important is the knowledge of the bacterial resistance phenotype. This is underlined by the existence of Gram-positive coccal strains resistant to erythromycin and other 14-,15-membered ring macrolides but susceptible to 16-membered ring macrolides. Since the local prevalence of erythromycin phenotypes is generally unknown but might determine the outcome of treatment, the procedure for identifying the phenotypes in erythromycin-resistant strains (which can be easily and cheaply performed using the two- or three-disk assay) should become routine, at least in the countries in which 16-membered ring macrolides are used. This approach should help to optimize the use of macrolides, improve our knowledge of the local prevalence of phenotypes resistant to erythromycin, and offer the possibility of treating infections caused by certain types of erythromycin-resistant pathogens.

Ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) continues to complicate the course of 8 to 28% of patients receiving mechanical ventilation (MV). In contrast to infections of more frequently involved organs (e.g., urinary tract and skin), for which mortality is low, ranging from 1 to 4%, the mortality rate for VAP ranges from 24 to 50% and can reach 76% in some specific settings or when lung infection is caused by high-risk pathogens. The predominant organisms responsible for infection are Staphylococcus aureus, Pseudomonas aeruginosa, and Enterobacteriaceae, but etiologic agents widely differ according to the population of patients in an intensive care unit, duration of hospital stay, and prior antimicrobial therapy. Because appropriate antimicrobial treatment of patients with VAP significantly improves outcome, more rapid identification of infected patients and accurate selection of antimicrobial agents represent important clinical goals. Our personal bias is that using bronchoscopic techniques to obtain protected brush and bronchoalveolar lavage specimens from the affected area in the lung permits physicians to devise a therapeutic strategy that is superior to one based only on clinical evaluation. When fiberoptic bronchoscopy is not available to physicians treating patients clinically suspected of having VAP, we recommend using either a simplified nonbronchoscopic diagnostic procedure or following a strategy in which decisions regarding antibiotic therapy are based on a clinical score constructed from seven variables. Selection of the initial antimicrobial therapy should be based on predominant flora responsible for VAP at each institution, clinical setting, information provided by direct examination of pulmonary secretions, and intrinsic antibacterial activities of antimicrobial agents and their pharmacokinetic characteristics. Further trials will be needed to clarify the optimal duration of treatment and the circumstances in which monotherapy can be safely used.

Prescribing practices that promote antibiotic resistance: strategies for change

Approximately 90% of all upper respiratory infections are caused by viruses, yet antibiotics are prescribed for 50% to 70% of patients who seek medical care for these conditions (Neiderman, Skerrett, & Yamauchi, 1998). Prescribing antibiotics for conditions for which there is no proven benefit is not a harmless practice; it contributes to the development of antibiotic resistance (Ware, 2000). This article will discuss the magnitude of the problem of antibiotic resistance as it relates to pediatric outpatient upper respiratory tract infection and otitis media, analyze practitioner prescribing practices that contribute to widespread antibiotic use, and suggest provider and patient intervention to improve the rational use of antibiotics.

Appropriate use of antibiotics for respiratory infections: review of recent statements and position papers

Respiratory infections are among the most common reasons for prescribing antibiotics. The excessive use of antibiotics in ambulatory practice has contributed to the emergence and spread of antibiotic resistance. The appropriate use of antimicrobial agents for respiratory infections could potentially reduce the emergence of antibiotic resistance. This article reviews recent guidelines and position papers on the appropriate antibiotic treatment for respiratory infections. There is a wide consensus that antibiotics are not appropriate for the treatment of most cases of acute bronchitis, pharyngitis, and rhinosinusitis. The recently published community-acquired pneumonia guidelines emphasized the importance of selecting antibiotic regimens active against both typical and atypical pathogens. However, there is disagreement regarding the routine use of the new quinolones.

Regulation of antimicrobial prescribing practices--a strategy for controlling nosocomial antimicrobial resistance

Approximately 10% of hospital in-patients in the UK acquire nosocomial infection, with an increasing number of these infections caused by multiresistant organisms. It is essential to halt the development and spread of antibiotic resistance among hospital pathogens. The relationship between antibiotic use and the development of antibiotic resistance in microorganisms is a subject of ongoing controversy and research. However, there is a general acceptance that control of antibiotic prescribing within hospitals is fundamental to controlling the development of nosocomial antibiotic resistance. In order to achieve this, there is a need to design and successfully implement targeted antibiotic policies based on local patterns of resistance. Traditional educational methods used alone for executing such policies have not been shown to be effective. Computer-based technology shows great promise but will require considerable resource allocation for its installation. Of equal importance, the Infection Control Team must be given a high profile. Robust surveillance systems to gather epidemiological data on local prescribing practices, hospital infection control policy compliance, antibiotic resistance and hospital infection rates need to be set up within individual hospitals. The appointment of an anti-infective pharmacist should be considered. Delivery of an integrated antibiotic and infection control service requires a co-ordinated, multidisciplinary team approach with clear leadership. Finally, in order for any strategy to be successful, the full support of hospital management is essential.

Symptoms and clinical and radiological signs predicting the presence of pathogenic bacteria in acute rhinosinusitis

A minority of patients with upper respiratory tract infections (URTI) have a bacterial infection and may benefit from antibiotherapy. In previous investigations we showed that in patients suffering from acute rhinosinusitis associated with the presence of Streptococcus pneumoniae, Haemophilus influenzae or Moraxella catarrhalis in their nasopharygeal secretions, resolution of symptoms was significantly improved by antibiotic treatment. The present analysis was performed to determine whether specific clinical symptoms or signs observed during careful endoscopic examination of the nasal cavities could help the clinician to identify a subset of patients with moderate forms of acute rhinosinusitis infected with pathogenic bacteria. Detailed clinical histories were obtained and medical examinations performed in 265 patients (138 females, 127 males; mean age 35 years) presenting with a < 4-week history of URTI symptoms but who did not require immediate antibiotic therapy for severe rhinosinusitis. The presence of three pathogenic bacteria (S. pneumoniae, H. influenzae and M. catarrhalis) was determined in all patients by culture of nasopharyngeal secretions. Azithromycin (500 mg/day for 3 days; n = 133) or placebo (n = 132) were randomly given to all patients in a double-blind manner. Pathogenic bacteria were found in 77 patients (29%). The clinical signs and symptoms significantly associated in a multivariate model with the presence of bacteria included colored nasal discharge (p < 0.003), facial pain (p < 0.032) and radiologically determined maxillary sinusitis (complete opacity, air-fluid level or mucosal thickening > 10 mm) (p < 0.001). This best predictive model had a sensitivity of 69% and a specificity of 64% and therefore could not be used either as a screening tool or as a diagnostic criterion for bacterial rhinosinusitis. In the group of patients with positive bacterial cultures, resolution of symptoms at Day 7 was observed in 73% of patients treated with azithromycin and in 47% of patients in the placebo group (p < 0.007). We conclude that signs and symptoms of acute rhinosinusitis in patients with mild-to-moderate clinical presentations are poor predictors of the presence of bacteria.

Clinical relevance of macrolide-resistant Streptococcus pneumoniae for community-acquired pneumonia

Macrolides are often the first choice for empirical treatment of community-acquired pneumonia. However, macrolide resistance among Streptococcus pneumoniae has escalated at alarming rates in North America and worldwide. Macrolide resistance among pneumococci is primarily due to genetic mutations affecting the ribosomal target site (ermAM) or active drug efflux (mefE). Prior antibiotic exposure is the major risk factor for amplification and perpetuation of resistance. Clonal spread facilitates dissemination of drug-resistant strains. Data assessing the impact of macrolide resistance on clinical outcomes are spare. Many experts believe that the clinical impact is limited. Ribosomal mutations confer high-grade resistance, whereas efflux mutations can likely be overridden in vivo. Favorable pharmacokinetics and pharmacodynamics, high concentrations at sites of infections, and additional properties of macrolides may enhance their efficacy. In this article, we discuss the prevalence of macrolide resistance among S. pneumoniae, risk factors and mechanisms responsible for resistance, therapeutic strategies, and implications for the future.

The continuing challenge of lower respiratory tract infections

Lower respiratory tract infections have been a major cause of morbidity and mortality among humans since the dawn of history. The initial hope that the era of antibiotics would remove this scourge has been replaced by the more realistic view that although antimicrobial agents represent a major therapeutic advance, they have not yet solved all of the problems of lower respiratory tract infections. The pneumococcus, for example, causes mortality in a certain number of patients despite antimicrobial therapy. An even greater challenge is being imposed by the emergence of antimicrobial resistance among important bacterial pathogens, especially Streptococcus pneumoniae.

A European study on the relationship between antimicrobial use and antimicrobial resistance

In Europe, antimicrobial resistance has been monitored since 1998 by the European Antimicrobial Resistance Surveillance System (EARSS). We examined the relationship between penicillin nonsusceptibility of invasive isolates of Streptococcus pneumoniae and antibiotic sales. Information was collected on 1998-99 resistance data for invasive isolates of S. pneumoniae to penicillin, based on surveillance data from EARSS and on outpatient sales during 1997 for beta-lactam antibiotics and macrolides. Our results show that in Europe antimicrobial resistance of S. pneumoniae to penicillin is correlated with use of beta-lactam antibiotics and macrolides.

Mechanisms of resistance to macrolides and lincosamides: nature of the resistance elements and their clinical implications

Resistance to macrolides and lincosamides is increasingly reported in clinical isolates of gram-positive bacteria. The multiplicity of mechanisms of resistance, which include ribosomal modification, efflux of the antibiotic, and drug inactivation, results in a variety of phenotypes of resistance. There is controversy concerning the clinical relevance of in vitro macrolide resistance. Recent data, however, have shown that eradication of bacteria correlates with clinical outcome of acute otitis media in children and that macrolide therapy results in delayed eradication of macrolide-resistant pneumococci. These results support the need for in vitro detection of macrolide resistance and correct interpretation of susceptibility tests to guide therapy.