Effect of antimicrobial use and other risk factors on antimicrobial resistance in pneumococci

Encouraging rational antibiotic prescribing behaviour in primary care - prescribing practice among children aged 0-4 years 2016-2018: an observational study

OBJECTIVE

To study antibiotic prescriptions among 0- to 4-year-old children before and after implementing a quality project on prudent prescribing of antibiotics in primary healthcare in the capital region of Iceland.

DESIGN

An observational, descriptive, retrospective study using quantitative methodology.

SETTING

Primary healthcare in the Reykjavik area with a total population of approximately 220,000.

SUBJECTS

A total of 6420 children 0-4 years of age presenting at the primary healthcare centres in the metropolitan area over three years from 2016 to 2018.

MAIN OUTCOME MEASURES

Reduction of antibiotic prescriptions and change in antibiotic profile. Data on antibiotic prescriptions for children 0-4 years of age was obtained from the medical records. Out-of-hours prescriptions were not included in the database.

RESULTS

The number of prescriptions during the study period ranged from 263.6 to 289.6 prescriptions/1000 inhabitants/year. A reduction of 9% in the total number of prescriptions between 2017-2018 was observed. More than half of all prescriptions were for otitis media, followed by pneumonia and skin infections. Amoxicillin accounted for over half of all prescriptions, increasing between 2016 and 2018 by 51.3%. During this period, the prescribing of co-amoxiclav and macrolides decreased by 52.3% and 40.7%, respectively. These changes were significant in all cases, p < 0.0001.

CONCLUSION

The results show an overall decrease in antibiotic prescribing concurrent with a change in the choice of antibiotics prescribed and in line with the recommendations presented in the prescribing guidelines implemented by the Primary Healthcare of the Capital Area, and consistent with the project's goals.Key pointsA substantial proportion of antibiotic prescribing can be considered inappropriate and the antibiotic prescription rate is highest in Iceland of the Nordic countries.After implementing guidance on the treatment of common infections together with feedback on antibiotic prescribing, a decrease in the total number of prescriptions accompanied by a shift in the antibiotic profile was observed.

Clinical and socio-environmental determinants of multidrug-resistant vibrio cholerae 01 in older children and adults in Bangladesh

Objectives:

Few studies have evaluated determinants of multidrug-resistant (MDR) Vibrio cholerae O1 in older children and adults. This study aimed to characterize the prevalence of MDR V. cholerae O1 and associated risk factors among patients over five years of age in Bangladesh.

Methods:

Stool culture and antimicrobial susceptibility testing were performed as a part of a larger study at Dhaka Hospital in Bangladesh from March 2019–March 2020. Univariate statistics and multiple logistic regression were used to assess the association between a range of variables and MDR V. cholerae O1.

Results:

MDR was found in 175 of 623 (28.1%) V. cholerae O1 isolates. High levels of resistance were found to erythromycin (99.2%), trimethoprim-sulfamethoxazole (99.7%), and ampicillin (88.9%), while susceptibility was high to tetracyclines (99.7%), azithromycin (99.2%), ciprofloxacin (99.8%), and cephalosporins (98.6%). MDR was associated with prior antibiotic use, longer transport time to hospital, higher income, non-flush toilet use, greater stool frequency, lower blood pressure, lower mid-upper arm circumference, and lower percent dehydration.

Conclusions:

MDR V. cholerae O1 was common among patients over five in an urban hospital in Bangladesh. Significant factors associated with MDR may be actionable in identifying patients with a high likelihood of MDR.

Antimicrobial stewardship programs; a two-part narrative review of step-wise design and issues of controversy. Part II: Ten questions reflecting knowledge gaps and issues of controversy in the field of antimicrobial stewardship

Regardless of one's opinion on antimicrobial stewardship programs (ASPs), it is hardly possible to work in hospital care and not be exposed to the term or its practical effects. Despite the term being relatively new, the number of publications in the field is vast, including several excellent reviews of general and specific aspects. Work in antimicrobial stewardship is complex, and include aspects not only of infectious disease and microbiology, but also of epidemiology, genetics, behavioural psychology, systems science, economics and ethics, to name but a few. This review aims to take several of these aspects and the scientific evidence from antimicrobial stewardship studies and merge them into two questions: How should we design ASPs based on what we know today? and Which are the most essential unanswered questions regarding antimicrobial stewardship on a broader scale? This narrative review is written in two separate parts aiming to provide answers to the two questions. The first part, published separately, is written as a step-wise approach to designing a stewardship intervention based on the pillars of unmet need, feasibility, scientific evidence and necessary core elements. It is written mainly as a guide to someone new to the field. It is sorted into five distinct steps; (a) focusing on designing aims; (b) assessing performance and local barriers to rational antimicrobial use; (c) deciding on intervention technique; (d) practical, tailored design including core element inclusion; and (e) evaluation and sustainability. This second part formulates 10 critical questions on controversies in the field of antimicrobial stewardship. It is aimed at clinicians and researchers with stewardship experience and strives to promote discussion, not to provide answers.

Rapid decline of bacterial drug-resistance in an antibiotic-free environment through phenotypic reversion

Antibiotic resistance typically induces a fitness cost that shapes the fate of antibiotic-resistant bacterial populations. However, the cost of resistance can be mitigated by compensatory mutations elsewhere in the genome, and therefore the loss of resistance may proceed too slowly to be of practical importance. We present our study on the efficacy and phenotypic impact of compensatory evolution in Escherichia coli strains carrying multiple resistance mutations. We have demonstrated that drug-resistance frequently declines within 480 generations during exposure to an antibiotic-free environment. The extent of resistance loss was found to be generally antibiotic-specific, driven by mutations that reduce both resistance level and fitness costs of antibiotic-resistance mutations. We conclude that phenotypic reversion to the antibiotic-sensitive state can be mediated by the acquisition of additional mutations, while maintaining the original resistance mutations. Our study indicates that restricting antimicrobial usage could be a useful policy, but for certain antibiotics only.

Should fast breathing pneumonia cases be treated with antibiotics? The scientific rationale for revisiting management in Low and Middle income countries

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World Health Organization (WHO) recommends oral antibiotic treatment for all children with fast breathing pneumonia.

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However evidence for the guidance is weak and infections are often viral and self-limiting.

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Further information regarding the true rationale for conducting non-inferiority trials to test the hypothesis that antibiotics may not be necessary for children with fast breathing as the sole symptomatology.

Background

Pneumonia is the largest single contributor to child mortality and the problem is more acute in low and middle income countries. The World Health Organization (WHO) currently recommends oral antibiotic treatment for all children with fast breathing pneumonia without danger signs. It is, however, widely acknowledged that most such infections are viral and self-limiting and that the evidence for the guidance is weak.

Rationale

Overuse of antibiotics exposes children to adverse events, increases cost for families, burdens already stretched health care resources and may contribute to development of antibiotic resistance.

Conclusion

There is equipoise regarding utility of antibiotic in case of fast breathing pneumonia and no high quality trial evidence exists. This paper provides further information behind the rationale for conducting non-inferiority trials to test the hypothesis that antibiotics may not be necessary for children with fast breathing as the sole symptomatology.

Carriage of penicillin-non-susceptible pneumococci among children in northern Tanzania in the 13-valent pneumococcal vaccine era

OBJECTIVES

To determine the antibiotic susceptibility and serotype distribution of colonizing Streptococcus pneumoniae in Tanzanian children. Serial cross-sectional surveys were performed following the national introduction of the 13-valent pneumococcal conjugate vaccine (PCV13) in December 2012.

METHODS

A total of 775 children less than 2 years of age were recruited at primary health centres in Moshi, Tanzania between 2013 and 2015, and samples were obtained from the nasopharynx. S. pneumoniae were isolated by culture and tested for antibiotic susceptibility by disc diffusion and E-test methods; molecular testing was used to determine serotype/group.

RESULTS

Penicillin non-susceptibility in the isolated pneumococci increased significantly from 31% (36/116) in 2013, to 47% (30/64) in 2014 and 53% (32/60) in 2015. Non-susceptibility to amoxicillin/ampicillin and ceftriaxone was low (n=8 and n=9, respectively), while 97% (236/244) of the isolates were non-susceptible to trimethoprim-sulfamethoxazole. The majority of the children (54%, n=418) had been treated with antibiotics in the past 3 months, and amoxicillin/ampicillin were overall the most commonly used antibiotics. Carriage of penicillin-non-susceptible pneumococci was more common in children with many siblings. The prevalence of PCV13 serotypes among the detected serotypes/groups decreased from 56% (40/71) in 2013 to 23% (13/56) in 2015.

CONCLUSIONS

Penicillin non-susceptibility in S. pneumoniae colonizing Tanzanian children increased during an observation period shortly after the introduction of PCV13. Measures to ensure rational use of antibiotics and more effective systems for surveillance of antibiotic resistance and serotype distribution are needed to assure continued effective treatment of pneumococcal disease.

Pneumococcal vaccination: Direct and herd effect on carriage of vaccine types and antibiotic resistance in Icelandic children

BACKGROUND

Since the introduction of pneumococcal conjugate vaccines, vaccine type pneumococcal carriage and disease has decreased world-wide. The aim was to monitor changes in the nasopharyngeal carriage of pneumococci, the distribution of serotypes and antimicrobial resistance in children before and after initiation of the 10-valent pneumococcal vaccination in 2011, in a previously unvaccinated population.

METHODS

Repeated cross-sectional study at 15day-care centres in greater Reykjavik area. Nasopharyngeal swabs were collected yearly in March from 2009 to 2015. The swabs were selectively cultured for pneumococci, which were serotyped using latex agglutination and/or PCR and antimicrobial susceptibility determined. Two independent studies were conducted. In study 1, on total impact, isolates from children aged <4years were included. The vaccine-eligible-cohort (birth-years: 2011-2013, sampled in 2013-2015) was compared with children at the same age born in 2005-2010 and sampled in 2009-2012. In study 2 on herd effect, isolates from older non-vaccine-eligible children (3.5-6.3years) were compared for the periods before and after the vaccination (2009-2011 vs 2013-2015. Vaccine impact was determined using 1-odds-ratio.

RESULTS

Following vaccination, the vaccine impact on vaccine type acquisition was 94% (95% CI: 91-96%) in study 1 and 56% (95% CI: 44-65%) in study 2. The impact on serotype 6A was 33% (95% CI: -9%; 59%) in study 1 and 42% (95% CI: 10-63%) in study 2 with minimal effect on 19A. The non-vaccine serotypes/groups 6C, 11, 15 and 23B were the most common serotypes/groups after vaccination. Isolates from the vaccine-eligible-cohort had lower penicillin MICs, less resistance to erythromycin and co-trimoxazole and less multi resistance than isolates from the control-group.

CONCLUSIONS

The efficacy of the vaccination on vaccine serotypes was high, and a milder effect on vaccine-associated-serotype 6A was observed for the vaccine-eligible-cohort. There was a significant herd effect on vaccine types in older non-vaccine-eligible children. Overall antimicrobial non-susceptibility was reduced.

Discrepant serological assays for Pneumococcus in renal transplant recipients - a prospective study

Vaccine immunoprotection for Streptococcus pneumoniae is mediated by opsonizing antibodies targeting serotype-specific capsular polysaccharides. Quantitative antibody levels enzyme-linked immunosorbent assay (ELISA) and antibody-mediated opsonophagocytic assays (OPA) measure vaccine-induced protection; correlation of these assays in transplantation requires investigation. This study examines the laboratory assessment of antibody titers in vaccinated renal recipients. Streptococcus pneumoniae 19A is common in immunocompromised hosts and is represented in protein-conjugate vaccines (PCV) and polysaccharide vaccines (PSV). Antibodies to 19A in serial sera from 30 vaccinated renal transplant recipients were compared using ELISA and OPA assays. Subject titers were classified as protected or not by ELISA (>0.35 μg/ml) and OPA titer (>1:8). Antibody titers analyzed using McNemar's test indicate that protection measured by the two assays are not the same (P = 0.0078); simple linear regression of within-subject geometric means of 19A enzyme-linked immunosorbent assay (ELISA) antibody levels versus 19A opsonophagocytic assays (OPA) titers demonstrates significant correlation between the two assays (P < 0.001). Vaccination is increasingly important given increasing antimicrobial resistance worldwide. OPA and ELISA antibody assays do not correlate well using current values for protective immunity against the Pneumococcus in immunosuppressed transplant recipients. Future studies of vaccination in transplant recipients should evaluate protective antibody levels using both functional antibody assays and standard ELISA antibody titers. (ClinicalTrials.gov: NCT00307125).

A double blind community-based randomized trial of amoxicillin versus placebo for fast breathing pneumonia in children aged 2-59 months in Karachi, Pakistan (RETAPP)

BACKGROUND

Fast breathing pneumonia is characterized by tachypnoea in the absence of danger signs and is mostly viral in etiology. Current guidelines recommend antibiotic therapy for all children with fast breathing pneumonia in resource limited settings, presuming that most pneumonia is bacterial. High quality clinical trial evidence to challenge or support the continued use of antibiotics, as recommended by the World Health Organization is lacking.

METHODS/DESIGN

This is a randomized double blinded placebo-controlled non-inferiority trial using parallel assignment with 1:1 allocation ratio, to be conducted in low income squatter settlements of urban Karachi, Pakistan. Children 2-59 months old with fast breathing, without any WHO-defined danger signs and seeking care at the primary health care center are randomized to receive either three days of placebo or amoxicillin. From prior studies, a sample size of 2430 children is required over a period of 28 months. Primary outcome is the difference in cumulative treatment failure between the two groups, defined as a new clinical sign based on preset definitions indicating illness progression or mortality and confirmed by two independent primary health care physicians on day 0, 1, 2 or 3 of therapy. Secondary outcomes include relapse measured between days 5-14. Modified per protocol analysis comparing hazards of treatment failure with 95% confidence intervals in the placebo arm with hazards in the amoxicillin arm will be done.

DISCUSSION

This study will provide evidence to support or refute the use of antibiotics for fast breathing pneumonia paving a way for guideline change.

TRIAL REGISTRATION

Clinical Trials (NIH) Register NCT02372461.

Antibiotic Exposure and Other Risk Factors for Antimicrobial Resistance in Nasal Commensal Staphylococcus aureus: An Ecological Study in 8 European Countries

Objectives

Antimicrobial resistance (AMR) has become a global public health concern which threatens the effective treatment of bacterial infections. Resistant Staphylococcus aureus (including MRSA) increasingly appears in individuals with no healthcare associated risks. Our study assessed risk factors for nasal carriage of resistant S. aureus in a multinational, healthy, community-based population, including ecological exposure to antibiotics.

Methods

Data were collected in eight European countries (Austria, Belgium, Croatia, France, Hungary, the Netherlands, Spain and Sweden). Commensal AMR patterns were assessed by collecting 28,929 nasal swabs from healthy persons (aged 4+). Ecological exposure to antibiotics was operationalized as systemic antibiotic treatment patterns, extracted from electronic medical records of primary care practices in which the participants were listed (10–27 per country). A multilevel analysis related AMR in nasal commensal S. aureus to antibiotic exposure and other risk factors (e.g. age and profession).

Results

Of the 6,093 S. aureus isolates, 77% showed resistance to at least one antibiotic. 7.1% exhibited multidrug resistance (defined as resistance to 3 or more antibiotic classes), and we found 78 cases MRSA (1.3%). A large variation in antibiotic exposure was found between and within countries. Younger age and a higher proportion of penicillin prescriptions in a practice were associated with higher odds for carriage of a resistant S. aureus. Also, we found higher multidrug resistance rates in participants working in healthcare or nurseries.

Conclusions

This study indicates that in a population with no recent antibiotic use, the prescription behavior of the general practitioner affects the odds for carriage of a resistant S. aureus, highlighting the need for cautious prescribing in primary care. Finally, since variation in AMR could partly be explained on a national level, policy initiatives to decrease AMR should be encouraged at the national level within Europe.

Variable recombination dynamics during the emergence, transmission and 'disarming' of a multidrug-resistant pneumococcal clone

BACKGROUND

Pneumococcal β-lactam resistance was first detected in Iceland in the late 1980s, and subsequently peaked at almost 25% of clinical isolates in the mid-1990s largely due to the spread of the internationally-disseminated multidrug-resistant PMEN2 (or Spain6B-2) clone of Streptococcus pneumoniae.

RESULTS

Whole genome sequencing of an international collection of 189 isolates estimated that PMEN2 emerged around the late 1960s, developing resistance through multiple homologous recombinations and the acquisition of a Tn5253-type integrative and conjugative element (ICE). Two distinct clades entered Iceland in the 1980s, one of which had acquired a macrolide resistance cassette and was estimated to have risen sharply in its prevalence by coalescent analysis. Transmission within the island appeared to mainly emanate from Reykjavík and the Southern Peninsular, with evolution of the bacteria effectively clonal, mainly due to a prophage disrupting a gene necessary for genetic transformation in many isolates. A subsequent decline in PMEN2's prevalence in Iceland coincided with a nationwide campaign that reduced dispensing of antibiotics to children in an attempt to limit its spread. Specific mutations causing inactivation or loss of ICE-borne resistance genes were identified from the genome sequences of isolates that reverted to drug susceptible phenotypes around this time. Phylogenetic analysis revealed some of these occurred on multiple occasions in parallel, suggesting they may have been at least temporarily advantageous. However, alteration of 'core' sequences associated with resistance was precluded by the absence of any substantial homologous recombination events.

CONCLUSIONS

PMEN2's clonal evolution was successful over the short-term in a limited geographical region, but its inability to alter major antigens or 'core' gene sequences associated with resistance may have prevented persistence over longer timespans.

Selection and evolution of resistance to antimicrobial drugs

The overuse and misuse of antibiotics over many years has selected a high frequency of resistance among medically important bacterial pathogens. The evolution of resistance is complex, frequently involving multiple genetic alterations that minimize biological fitness costs and/or increase the resistance level. Resistance is selected at very low drug concentrations, such as found widely distributed in the environment, and this selects for resistant mutants with a high fitness. Once resistance with high fitness is established in a community it is very difficult to reduce its frequency. Addressing the problem of resistance is essential if we are to ensure a future where we can continue to enjoy effective medical control of bacterial infections. This will require several actions including the discovery and development of novel antibiotics, the creation of a continuous pipeline of drug discovery, and the implementation of effective global antibiotic stewardship to reduce the misuse of antibiotics and their release into the environment.

Reversibility of antibiotic resistance

Although theoretically attractive, the reversibility of resistance has proven difficult in practice, even though antibiotic resistance mechanisms induce a fitness cost to the bacterium. Associated resistance to other antibiotics and compensatory mutations seem to ameliorate the effect of antibiotic interventions in the community. In this paper the current understanding of the concepts of reversibility of antibiotic resistance and the interventions performed in hospitals and in the community are reviewed.

Epidemiology of penicillin-non-susceptible pneumococci in Iceland, 1995-2010

OBJECTIVES

The first penicillin-non-susceptible pneumococci (PNSP) were identified in Iceland in 1988. A rapid increase followed, associated with expansion of a single multiresistant clone, Spain(6B)-2, peaking at 19.8% in 1993. After interventions led to reduced antimicrobial use in children, the prevalence of PNSP decreased until 1995. The aim of this study was to follow the evolution of PNSP from 1995 to 2010, the period preceding the introduction of conjugated pneumococcal vaccines into the vaccination programme.

METHODS

The laboratory at the Landspitali University Hospital serves ∼ 85% of the Icelandic population. All pneumococci isolated from 1995 to 2010 (n = 13,937) were stored (-80 °C). Oxacillin-resistant isolates were serotyped and penicillin MICs were determined. Selected strains were genotyped by PFGE and multilocus sequence typing.

RESULTS

In 1995, the rate of PNSP was 24.2%, declining to 13.6% in 2001, and then increasing to 38.6% in 2010. Similar changes were observed for resistance to erythromycin and tetracycline. In 1995, 60.7% of PNSP were serotype 6B, mainly the Spain(6B)-2 clone, declining to 5.7% in 2010. PNSP of serotype 19F rapidly increased after 2004 to comprise 85.8% of all serogrouped PNSP in 2010, with most isolates belonging to a single multiresistant PFGE clone identified as sequence type (ST) 271 and ST1968, representing single- and double-locus variants of the international clone Taiwan(19F)-14, respectively. PNSP were most common among young children, from the nasopharynx, middle ear and lower respiratory tract.

CONCLUSIONS

The epidemiology of PNSP was dominated by two multiresistant clones. The second expanded rapidly when the first one was disappearing, causing higher antibiotic resistance rates among pneumococci than seen before in Iceland.

Low rate of pneumococci non-susceptible to penicillin in healthy Swedish toddlers

BACKGROUND

Infection caused by Streptococcus pneumoniae is the leading cause of mortality in children worldwide. The aim of this study was to determine if a noted increase in non-susceptibility to penicillin among pneumococcal clinical isolates from young children reflected a similar increase in healthy children.

METHODS

During 2004-2005, before the conjugate pneumococcal vaccine was introduced in Sweden, 663 healthy children (13-24 months of age) attending 17 child health centres in Gothenburg, Sweden, were cultured for bacteria in the nasopharynx. Social factors were identified through a parental questionnaire. Pneumococcal serotypes and antibiotic resistance rates were determined. Antibiotic resistance was also monitored in 162 simultaneously obtained nasopharyngeal pneumococci isolated from clinical samples.

RESULTS

The healthy children frequently carried pneumococci (45%), Moraxella catarrhalis (54%), and Haemophilus influenzae (22%). The carriage rates for all these pathogens were higher in children attending day care centres compared to children staying at home (p < 0.001). The dominating pneumococcal serotypes were 6B, 19F, 23F, and 6A. Non-susceptibility to penicillin was low (4.0%) and only exceeded by that to trimethoprim-sulfamethoxazole (9.8%). Both rates were higher in the clinical isolates (9.3% and 16.7%, respectively; p < 0.05). No relationships to geographic area, day care attendance, recent antibiotic use, or travel abroad were shown for any specific serotype or for the presence of penicillin-non-susceptible pneumococci in the healthy children.

CONCLUSIONS

Pneumococcal resistance rates in the healthy child population were low and did not reflect the higher rates noted at the laboratory in clinical samples obtained before and during the study.

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.

The fitness cost of antibiotic resistance in Streptococcus pneumoniae: insight from the field

Background

Laboratory studies have suggested that antibiotic resistance may result in decreased fitness in the bacteria that harbor it. Observational studies have supported this, but due to ethical and practical considerations, it is rare to have experimental control over antibiotic prescription rates.

Methods and Findings

We analyze data from a 54-month longitudinal trial that monitored pneumococcal drug resistance during and after biannual mass distribution of azithromycin for the elimination of the blinding eye disease, trachoma. Prescription of azithromycin and antibiotics that can create cross-resistance to it is rare in this part of the world. As a result, we were able to follow trends in resistance with minimal influence from unmeasured antibiotic use. Using these data, we fit a probabilistic disease transmission model that included two resistant strains, corresponding to the two dominant modes of resistance to macrolide antibiotics. We estimated the relative fitness of these two strains to be 0.86 (95% CI 0.80 to 0.90), and 0.88 (95% CI 0.82 to 0.93), relative to antibiotic-sensitive strains. We then used these estimates to predict that, within 5 years of the last antibiotic treatment, there would be a 95% chance of elimination of macrolide resistance by intra-species competition alone.

Conclusions

Although it is quite possible that the fitness cost of macrolide resistance is sufficient to ensure its eventual elimination in the absence of antibiotic selection, this process takes time, and prevention is likely the best policy in the fight against resistance.

Resource use and costs of treating acute cough/lower respiratory tract infections in 13 European countries: results and challenges

The objectives of this study were to estimate the resource use and cost of treating acute cough/lower respiratory tract infection (acute cough/LRTI) in 13 European countries, to explore reasons for differences in cost and to document the challenges that researchers face when collecting information on cost alongside multinational studies. Data on resource use and cost were collected alongside an observational study in 14 primary care networks across 13 European countries and a mean cost was generated for each network. The results show that the mean cost (standard deviation) of treating acute cough/LRTI in Europe ranged from euro23.88 (34.67) in Balatonfüred (Hungary) to euro116.47 (34.29) in Jonkoping (Sweden). The observed differences in costs were statistically significant (P < 0.01). Major cost drivers include general practitioner visits and drug costs in all networks, whilst differences in health systems and regional factors could account for differences in cost between networks. The major barrier to conducting multinational cost studies are barriers associated with identifying cost information.

Non-antibiotic treatment for pediatric outpatients with common cold inhibits the emergence of drug resistant pneumococci

The occurrence of drug resistant Streptococcus pneurmoniae (S. pneumoniae) is very high in Japan. Unnecessary use of antibiotics had been thought to cause this problem but previous studies had not clearly showed that the decreasing rate of antibiotic use had been related to the reduction of the prevalence of resistant strains. In this study, we tried to prove that non-antibiotic treatment for common cold would reduce the antibiotic resistant S. pneumoniae in nasopharynx in children. Forty-five children with the common cold were randomly selected from pediatric patients who had taken antibiotics within the past three months. We collected nasopharyngeal swabs from all of the participants and once again after a period of 2 to 3 months without using any antibiotics. Twenty-four of these patients had the S. pneumoniae strains isolated. Then these strains were undergone a susceptibility test and drug-resistant gene detection. The susceptibility test reveled that patients with penicillin-resistant strains decreased from 17 to 7 (p < 0.01). The test also reveled that the decreased number of patients had strains that were resistant to cefditren. The gene detection revealed that none of the patients acquired a higher resistance to penicillin. Our study suggests that the treatment without antibiotics reduces the drug-resistant S. pneumoniae. Controlled antibiotic use in children might prevent children from carrying the antibiotic resistant S. pneumoniae.

The global need for effective antibiotics: challenges and recent advances

The emerging problem of antibiotic resistance is a serious threat to global public health. The situation is aggravated by a substantial decline in the research and development of antibacterial agents. Hence, very few new antibacterial classes are brought to market when older classes lose their efficacy. There has been renewed and growing attention within policy groups to: (i) address the problem; (ii) discuss incentives for the development of urgently needed new treatments; (iii) preserve the efficacy of existing therapeutic options. We briefly review the basic principles of antibiotic resistance, and contrast the increasing resistance to the dwindling antibacterial 'pipeline'. We also highlight some recent policy initiatives aiming to secure the future need of effective antibiotics.

Risk factors for antibiotic-resistant Escherichia coli carriage in young children in Peru: community-based cross-sectional prevalence study

Few studies have examined the influence of individual-, household-, and community-scale risk factors on carriage of resistant commensal bacteria. We determined children's medical, agricultural, and environmental exposures by household, pharmacy, and health facility surveys and Escherichia coli cultures of children, mothers' hands, household animals, and market chickens in Peru. Among 522 children with a positive stool culture, by log-binomial regression, using "any antibiotic" and 1-14 (versus 0) sulfa doses in the past 3 months increased children's risk, respectively, for ampicillin- and sulfamethoxazole-resistant E. coli carriage (P = 0.01-0.02). Each household member taking "any antibiotic" increased children's risk for sulfamethoxazole- and multidrug-resistant E. coli carriage (P < 0.0001). Residence in a zone where a larger proportion of households served home-raised chicken (as contrasted with intensively antibiotic-raised market chicken) protected against carrying E. coli resistant to all drugs (P = 0.0004-0.04). Environmental contamination with drug-resistant bacteria appeared to significantly contribute to children's carriage of antibiotic-resistant E. coli.

Antimicrobial resistance among respiratory pathogens in Spain: latest data and changes over 11 years (1996-1997 to 2006-2007)

A nationwide multicenter susceptibility surveillance study (Susceptibility to the Antimicrobials Used in the Community in España [SAUCE] project), SAUCE-4, including 2,559 Streptococcus pneumoniae, 2,287 Streptococcus pyogenes, and 2,736 Haemophilus influenzae isolates was carried out from May 2006 to June 2007 in 34 Spanish hospitals. Then, the results from SAUCE-4 were compared to those from all three previous SAUCE studies carried out in 1996-1997, 1998-1999, and 2001-2002 to assess the temporal trends in resistance and the phenotypes of resistance over the 11-year period. In SAUCE-4, on the basis of the CLSI breakpoints, penicillin (parenteral, nonmeningitis breakpoint) and cefotaxime were the antimicrobials that were the most active against S. pneumoniae (99.8% and 99.6%, respectively). Only 0.9% of isolates had a penicillin MIC of > or = 2 microg/ml. In S. pyogenes, nonsusceptibility to erythromycin was observed in 19.4% of isolates. Among the H. influenzae isolates, a beta-lactamase-positive prevalence of 15.7% was found. A statistically significant temporal decreasing trend over the 11-year period was observed for nonsusceptibility (from 60.0% to 22.9%) and resistance (from 36.5% to 0.9%) to penicillin and for the proportion of erythromycin-resistant isolates of S. pneumoniae of the macrolide-lincosamide-streptogramin B (MLS(B)) phenotype (from 98.4% to 81.3%). A similar trend was observed for the prevalence of ampicillin resistance (from 37.6% to 16.1%), beta-lactamase production (from 25.7% to 15.7%), and beta-lactamase-negative ampicillin resistance (BLNAR) in H. influenzae (from 13.5% to 0.7%). Among erythromycin-resistant isolates of S. pyogenes, a significant increasing trend in the prevalence of MLS(B) was observed (from 7.0% to 35.5%). SAUCE-4 confirms a generalized decline in the resistance of the main respiratory pathogens to the antimicrobials as well as a shift in their resistance phenotypes.

Antibiotic resistance and its cost: is it possible to reverse resistance?

Most antibiotic resistance mechanisms are associated with a fitness cost that is typically observed as a reduced bacterial growth rate. The magnitude of this cost is the main biological parameter that influences the rate of development of resistance, the stability of the resistance and the rate at which the resistance might decrease if antibiotic use were reduced. These findings suggest that the fitness costs of resistance will allow susceptible bacteria to outcompete resistant bacteria if the selective pressure from antibiotics is reduced. Unfortunately, the available data suggest that the rate of reversibility will be slow at the community level. Here, we review the factors that influence the fitness costs of antibiotic resistance, the ways by which bacteria can reduce these costs and the possibility of exploiting them.

Crystallization and preliminary X-ray diffraction studies of the carbohydrate-recognition domain of SIGN-R1, a receptor for microbial polysaccharides and sialylated antibody on splenic marginal zone macrophages

SIGN-R1, or CD209b, is a mouse C-type lectin receptor that is expressed at high levels on macrophages in lymphoid tissues, especially within the marginal zone of the spleen. SIGN-R1 can bind and mediate the uptake of various microbial polysaccharides, including dextrans, lipopolysaccharides and pneumococcal capsular polysaccharides. It has been shown that SIGN-R1 mediates the clearance of encapsulated pneumococcus, complement fixation via binding C1q independent of antibody and innate resistance to pneumococcal infection. Recently, SIGN-R1 has also been demonstrated to bind sialylated antibody and mediate its activity to suppress autoimmunity. The carbohydrate-recognition domain (CRD) of SIGN-R1 has been cloned and overexpressed in a soluble secretory form in mammalian Chinese hamster ovary (CHO) cells. The CRD protein of SIGN-R1 was purified from CHO cell-culture supernatant and concentrated for crystallization using the hanging-drop vapour-diffusion method at 291 K. Crystals grew from a mixture of 2 M ammonium sulfate in 0.1 M bis-tris pH 5.5. Single crystals, which belonged to the monoclinic space group C2 with unit-cell parameters a = 146.72, b = 92.77, c = 77.06 A, beta = 121.66 degrees , allowed the collection of a full X-ray data set to a maximum resolution of 1.87 A.

Little evidence for reversibility of trimethoprim resistance after a drastic reduction in trimethoprim use

OBJECTIVES

The worldwide rapid increase in antibiotic-resistant bacteria has made efforts to prolong the lifespan of existing antibiotics very important. Antibiotic resistance often confers a fitness cost in the bacterium. Resistance may thus be reversible if antibiotic use is discontinued or reduced. To examine this concept, we performed a 24 month voluntary restriction on the use of trimethoprim-containing drugs in Kronoberg County, Sweden.

METHODS

The intervention was performed on a 14 year baseline of monthly data on trimethoprim resistance and consumption. A three-parameter mathematical model was used to analyse the intervention effect. The prerequisites for reversion of resistance (i.e. fitness cost, associated resistance and clonal composition) were studied on subsets of consecutively collected Escherichia coli from urinary tract infections.

RESULTS

The use of trimethoprim-containing drugs decreased by 85% during the intervention. A marginal but statistically significant effect on the increase in trimethoprim resistance was registered. There was no change in the clonal composition of E. coli and there was no measurable fitness cost associated with trimethoprim resistance in clinical isolates. The frequency of associated antibiotic resistances in trimethoprim-resistant isolates was high.

CONCLUSIONS

A lack of detectable fitness cost of trimethoprim resistance in vitro together with a strong co-selection of other antibiotics could explain the rather disappointing effect of the intervention. The result emphasizes the low possibility of reverting antibiotic resistance once established and the urgent need for the development of new antibacterial agents.

Acute bacterial meningitis caused by Streptococcus pneumoniae resistant to the antimicrobian agents and their serotypes

The main objectives of this study are to evaluate the resistance rates of Streptococcus pneumonia to penicillin G, ceftriaxone and vancomycin in patients with meningitis; to analyze possible risk factors to the antimicrobian resistance; to describe the serotypes detected and to suggest an initial empirical treatment for meningitis. The sensitiveness and serotypes of all isolated S. pneumoniae of patients with acute bacterial meningitis received by the Paraná State Central Laboratory from April 2001 to august 2002 have been evaluated. One hundred S. pneumoniae have been isolated, of which 15% were resistant to penicillin, 1% to cephalosporin and 0% to vancomycin. The serotypes most found were 14 (19%), 3 and 23F (10% each). When only the resistant serotypes were analyzed, the most prevalent was the 14 with 44%. The risk factors found in relation to the S. pneumoniae resistance were: age under one year old (p=0.01) and previous use of antibiotic (p=0.046). The resistance rates found, which were moderate to penicillin, low to cephalosporin and neutral to vancomycin, suggest the isolated use of a 3rd generation cephalosporin as an initial empirical therapy for the treatment of acute bacterial meningitis with a communitarian background.

Economic burden of adult pharyngitis: the payer's perspective

OBJECTIVES

Although not recommended by practice guidelines, physicians frequently prescribe an antibiotic for adults with viral pharyngitis. The financial burden of this practice, from the payer's perspective, has not been previously evaluated. The purpose of this study was to estimate those expenditures.

METHODS

A cost-of-illness study was performed to estimate annual expenditures of pharyngitis management from the payer's perspective. National Ambulatory Care Survey data were used to represent current patterns of ambulatory care visits and antibiotic prescriptions for adult pharyngitis. Direct and antibiotic resistance costs were summed to estimate total expenditures for pharyngitis management. Resistance costs were calculated using a model linking the effect of antibiotic consumption to the cost consequences of resistant Streptococcus pneumoniae infection. Sensitivity analyses compared cost outcomes of current practice, adherence to pharyngitis management guidelines from the Infectious Diseases Society of America (IDSA), and nonantibiotic treatment.

RESULTS

In the base-case analysis, reflecting current practice patterns, total expenditures were $1.2 billion with antibiotic resistance contributing 36% ($426 million). IDSA guideline adherence decreased costs to $559 million with resistance accounting for 6.8% ($37.9 million). Guideline adherence plus reducing office visits by 30% decreased costs to $372 million, with only 1.4% ($5.3 million) due to resistance. Additional cost-savings of $88 million were realized by using a nonantibiotic treatment strategy.

CONCLUSIONS

Current practice imposed a substantial economic burden on the payer, while guideline adherence resulted in cost reductions, especially in terms of resistance, emphasizing that antibiotic prescribing habits have broad economic consequences. Relevant stakeholders, payers, physicians, and other health-care providers should revisit efforts to encourage adherence to pharyngitis guidelines to reduce health-care costs.

Elucidation of the molecular recognition of bacterial cell wall by modular pneumococcal phage endolysin CPL-1

Pneumococcal bacteriophage-encoded lysins are modular proteins that have been shown to act as enzymatic antimicrobial agents (enzybiotics) in treatment of streptococcal infections. The first x-ray crystal structures of the Cpl-1 lysin, encoded by the pneumococcal phage Cp-1, in complex with three bacterial cell wall peptidoglycan (PG) analogues are reported herein. The Cpl-1 structure is folded in two well defined modules, one responsible for anchoring to the pneumococcal cell wall and the other, a catalytic module, that hydrolyzes the PG. Conformational rearrangement of Tyr-127 is a critical event in molecular recognition of a stretch of five saccharide rings of the polymeric peptidoglycan (cell wall). The PG is bound at a stretch of the surface that is defined as the peptidoglycan-binding sites 1 and 2, the juncture of which catalysis takes place. The peptidoglycan-binding site 1 binds to a stretch of three saccharides of the peptidoglycan in a conformation essentially identical to that of the peptidoglycan in solution. In contrast, binding of two peptidoglycan saccharides at the peptidoglycan-binding site 2 introduces a kink into the solution structure of the peptidoglycan, en route to catalytic turnover. These findings provide the first structural evidence on recognition of the peptidoglycan and shed light on the discrete events of cell wall degradation by Cpl-1.

Macrolide and ketolide resistance with Streptococcus pneumoniae

Antimicrobial agents in the macrolide family have long been considered drugs of potential utility in the management of infections caused by Streptococcus pneumoniae. However, with the emergence of macrolide resistance, the clinical value of macrolides in pneumococcal infections is threatened. In part, as a consequence of the development of macrolide resistance, recently the first agent in the ketolide antimicrobial class, telithromycin, was developed and introduced into clinical practice. The ketolides are macrolide antimicrobials whose chemistry has been modified so as avoid the effects of the most common mechanisms of macrolide resistance with S pneumoniae. This discussion reviews the current state of resistance to macrolides and ketolides with S pneumoniae in North America.

Otitis media today: a challenge for physicians and the community

Acute otitis media is one of the most common causes of medical consultation worldwide, and has a high economic impact. In this review, a clear definition between acute otitis media and otitis media with effusion is presented. The microbiology and characterization of the main bacterial isolates in acute otitis media and the susceptibility patterns are reviewed, and the latest concepts in antimicrobial treatment are discussed. The need for courses that improve the capability of primary care physicians to diagnose acute otitis media using pneumatic otoscopy, and for parental education is also discussed.

Antibiotic consumption and generation of resistance in Streptococcus pneumoniae: the paradoxical impact of quinolones in a complex selective landscape

The development of resistance to the different antibiotics by the majority of bacterial species of clinical importance seems unavoidable. However, not all drugs have the same efficiency to select for resistance. Large differences in the qualitative and quantitative consumption of antibiotics among countries are known to exist and several authors have consistently reported the direct relationship between consumption and selection of resistance for Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae and Escherichia coli and beta-lactams and macrolides use. In Spain, extensive surveillance started in 1996, and the Willow (SAUCE) Project, to monitor and update resistance in respiratory pathogens and to couple those data with data concerning national antibiotic consumption (IMS) from both a temporal and geographical approach. Temporally, despite a continuous increase of 16% in quinolone consumption from 1997 to 2001, basically due to the arrival of respiratory quinolones, levofloxacin and moxifloxacin, a continuous linear increase in the resistance rates to ciprofloxacin in S. pneumoniae was not observed. There also was an inverse correlation between provincial consumption of quinolones and resistance to ciprofloxacin. Several hypotheses are proposed and discussed to explain these apparent paradoxical observations, such as the replacement of ciprofloxacin by more potent antipneumococcal quinolones, the possibility of an antibiotic pressure threshold, the influence of other nonquinolone drugs on the expression of ciprofloxacin-resistance biological costs, and the influence of changes in temporal or spatial prevalence of particular clones.

Surveillance of antibiotic resistance in non invasive clinical isolates of Streptococcus pneumoniae collected in Belgium during winters 2003 and 2004

A total of 391 and 424 non-invasive isolates of Streptococcus pneumoniae collected by 15 laboratories during the 2003 and 2004 survey were tested for their susceptibility by a microdilution technique following NCCLS recommendations. Insusceptibility rates (IR) in the two surveys (2003/2004) were as follows: penicillin 15.0/14.7% [8.4/6.4% Resistance (R)], ampicillin 17.4/14.6% (R 9.0/7.1%), amoxicillin +/- clavulanic acid 2.6/1.2 % (R 0/0%), cefaclor 14.3/14.1% (R 11.5/13.4%), cefuroxime 13.6/12.7% (R 10.5/11.8%), cefuroxime-axetil 10.5/11.8% (R 10.0/9.2%) (breakpoints based on 250 mg), cefotaxime 4.9/6.2% (R 1.3/2.4%), ceftazidime NotTested (NT)/6.4 (R NT/2.6%), cefepime NT/6.4 (R NT/2.6%), imipenem 7.7/8.9 % (R 1.8/1.4%), ertapenem 0.8/NT% (R O/NT%), ciprofloxacin 13.8/9.0% (R 4.3/2.4%), levofloxacin 3.3/2.8% (R 1.5/0.2%), moxifloxacin 0.6/0.2% (R 0.3/0%), ofloxacin 13.5/9.0% (R 4.3/2.4%), erythromycin 26.1/24.7% (R 25.3/24.5%), azithromycin 25.4/24.7% (R 24.6/24.5%), telithromycin 0.8/0.2% (R 0.5/0%), clindamycin 21.2/18.4% (R 19.2/17.7%) and tetracycline 32.3/22.1% (R 29.2/19.3%). There were only minor differences in resistance rates according to age, sample site, admission type (i.e. ambulatory, hospitalized or long-term care facility patients), gender and geographic origin. Overall, telithromycin (MIC50, MIC90 in 2003/2004: 0.015 microg/ml, 0.12 microg/ml/ 0.008,0.06 respectively), ertapenem (0.03; 0.25/NT), moxifloxacin (0.06; 0.25/0.06, 0.12), and amoxicillin +/- clavulanic acid (0.03; 0.25/0.015, 0.5) were the most active compounds in both surveys. In 2003, the most common resistance phenotype was isolated insusceptibility to tetracycline (10.5%) followed by combined insusceptibility to erythromycin and tetracycline (9.3%). Erythromycin-tetracycline resistance (10.4%) was the most common in 2004. Isolates showing resistance to an antibiotic were significantly more present in 2003 than in 2004 (50.4% versus 40.8%). In penicillin-insusceptible isolates, MICs of all beta-lactams were increased but cross-resistance between penicillin and other beta-lactams in the penicillin-insusceptible isolates was not complete. In the 2003 survey, most of these isolates remained fully susceptible to ertapenem (94.9%) and amoxicillin +/- clavulanic acid (83.1%). In the 2004 survey, 91.9% of the penicillin insusceptible isolates remained susceptible to amoxicillin +/- clavulanic acid. In both surveys, the most common serotypes in penicillin insusceptible isolates were 14, 23,19 and 9 (20.0%, 20.0%, 16.4% and 10.9% respectively in 2003; 41.6%, 11.7%, 15.0% and 18.3% respectively in 2004).

Comparison of genetic backgrounds of methicillin-resistant and -susceptible Staphylococcus aureus isolates from Portuguese hospitals and the community

In order to understand the origins of the dominant methicillin-resistant Staphylococcus aureus (MRSA) clones in Portuguese hospitals, we compared the genetic backgrounds of nosocomial MRSA with methicillin-susceptible S. aureus (MSSA) isolates from the same hospitals (n=155) and from the community (n=157) where they were located. Pulsed-field gel electrophoresis, spa typing, multilocus sequence typing, and agr type analysis revealed that the genetic backgrounds correspondent to the dominant MRSA clones in Portuguese hospitals during the last 15 years (Iberian ST 247, Brazilian ST 239, and EMRSA-15 ST 22) were scarcely or not found among the present MSSA collection. The four major MSSA clones encountered (A-ST 30, B-ST 34, C-ST 5, and H-ST 45) correspond, or are very similar, to the background of other international MRSA pandemic clones, i.e., EMRSA-16, New York/Japan, Pediatric, and Berlin clones. However, with the exception of the Pediatric clone, none of these MRSA clones has been detected in Portugal. Our findings suggest the three major MRSA clones identified in Portuguese hospitals have not originated from the introduction of SCCmec into dominant MSSA backgrounds present in the Portuguese nosocomial or community environment but were probably imported from abroad. In contrast, the MRSA Pediatric clone might have originated in our country by the acquisition of SCCmec type IV into MSSA clone C. Furthermore, we provide evidence that the introduction of SCCmec into sensitive clones is most likely a relatively infrequent event that seems to depend not exclusively on the presence of a successful MSSA lineage.

Helicobacter pylori eradication has the potential to prevent gastric cancer: a state-of-the-art critique

Helicobacter pylori infection continues to play a key role in gastric diseases. Colonization of the gastric mucosa with the bacterium invariably results in the development of chronic gastritis and subsets of patients have a progression of the chronic gastritis to either ulcer or cancer. Epidemiological evidence indicates that the proportion of all gastric cancers attributable to H. pylori infection, and hence potentially preventable upon elimination of this risk factor, is somewhere in the range of 60% to 90%. This portends significant benefit in terms of morbidity and mortality, not least in populations with high prevalence of H. pylori infection coupled with high incidence of gastric cancer. The effect of prophylactic H. pylori eradication on gastric cancer incidence in humans remains unknown, however. Results from randomized trials are eagerly awaited, but availability of strong conclusive results may take many years. A growing number of studies show considerable variation in risk for gastric cancer development, depending on H. pylori strain type and the genetic predisposition of the host. There is also a remote possibility that elimination of the infection may have adverse health implications (e.g., antibiotic resistance), and therefore "simple" risk stratification and targeted chemoprevention is required. Based on "in depth" evidence presented at this workshop, the majority of the scientific task force favored a search-and-treat strategy in first-degree relatives of gastric cancer patients and an overwhelming majority felt that a more general screen-and-treat strategy should be focused in the first instance on a population with a high incidence of H. pylori-associated diseases.

Compensatory adaptation to the loss of biological fitness associated with acquisition of fusidic acid resistance in Staphylococcus aureus

Recent studies have shown that individual amino acid exchanges within elongation factor G (EF-G) cause fusidic acid resistance in Staphylococcus aureus. The data from the present study illustrate that the fusidic acid resistance-mediating amino acid substitutions P406L and H457Y are associated with a marked impairment of the biological fitness of S. aureus. In particular, strains producing EF-G derivatives with these mutations showed reduced growth, decreased plasma coagulase activity, and an impaired capability to compete with the isogenic wild-type strain. Second-site mutations within EF-G, such as A67T and S416F, that have been encountered in clinical fusidic acid-resistant isolates containing the amino acid exchanges P406L and H457Y, respectively, were shown not to contribute to resistance. Furthermore, the substitution A67T had no impact on the biological fitness in vitro. The exchange S416F, however, was found to function as a fitness-compensating mutation in S. aureus carrying the substitution H457Y in EF-G. In conclusion, the data presented in this report provide evidence at the molecular level that the deleterious effects of fusidic acid resistance-mediating exchanges within EF-G of S. aureus can be reduced considerably by specific compensating mutations in this target protein. This compensatory adaptation most likely plays a significant role in the stabilization of resistant bacteria within a given population.

Effect of the seven-valent conjugate pneumococcal vaccine on carriage and drug resistance of Streptococcus pneumoniae in healthy children attending day-care centers in Lisbon

AIMS

Prospective study to evaluate the impact of the 7-valent pneumococcal conjugate vaccine (Prevenar) on the nasopharyngeal (NP) carriage of drug-resistant Streptococcus pneumoniae (DRPn), by healthy children attending day-care centers (ages 6 months-6 years).

METHODS

Vaccinees (238 children) who received vaccine and controls (457 children) were followed for carriage of total S. pneumoniae and DRPn and for the serotypes and genetic backgrounds of DRPn during 6 consecutive sampling periods between May 2001 and February 2003.

RESULTS

We detected no significant differences between vaccinees and the control group in the total carriage rate of Pn (average, 68%) or in the frequency of carriage of DRPn (average, 38%), including the frequency of penicillin-nonsusceptible strains (average, 24%). In contrast, there was a decline in the carriage of DRPn with vaccine serotypes which was compensated by the appearance and gradual increase in the frequency of DRPn expressing unusual serotypes (6A, 10A, 15A and 15C, 19A, 23A, 33F) which were not present in the vaccine as well as an increase in nontypable strains. The majority of the DRPn with unusual serotypes showed different pulsed field gel electrophoresis patterns indicating replacement of the original resistant flora by other clonal types of drug-resistant bacteria. Antibiotic consumption and the frequency of respiratory tract infections were similar among the vaccinees and controls.

CONCLUSIONS

Pneumococcal vaccination did not change the frequency of carriage of drug-resistant strains being the initially dominant vaccine serotypes replaced by others expressing nonvaccine serotypes. Reduction in the carriage of DRPn may require a combination of the conjugate vaccine and a decrease in antibiotic pressure.

Short-Course Therapy for Community-Acquired Pneumonia in Paediatric Patients

Studies conducted over the past few years for the treatment of pneumonia have provided data on the basis of which therapeutic decisions concerning the duration of therapy can be taken. Results from a majority of the studies conducted in hospitalised patients using the conventional methods for diagnosing pneumonia have methodological problems, which make it difficult to draw definite conclusions. Despite these limitations, the overall trend of these descriptive studies show a therapy of < or =5 days being as effective as the longer course of 7-14 days for children up to the age of 12 years. Data for duration of antibacterial therapy for infants <2 months of age hardly exists. Evidence suggests that a shorter course of antibacterial therapy of 3 days is effective for treatment of community-acquired, non-severe ambulatory pneumonia in immunocompetent children aged 2-59 months old. Shorter duration of therapy offers several potential advantages that include prevention of the emergence of antimicrobial resistance, lower healthcare costs, improved adherence to therapy and fewer adverse effects. There is a need to improve the evidence base for the optimum duration of therapy for children hospitalised with severe pneumonia.

Characteristics of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis isolated from the nasopharynges of asymptomatic children and molecular analysis of S. pneumoniae and H. influenzae strain replacement in the nasopharynx

Nasopharyngeal carriage of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in 226 children in different settings (in a crèche [day care center], in an orphanage, and at home) during two seasons (winter and spring) was studied. The rates of carriage of S. pneumoniae and H. influenzae were markedly higher in the crèche and in the orphanage than in the home setting (e.g., 56.5, 63.3, and 25.9%, respectively, for S. pneumoniae in winter). Approximately 80% of the S. pneumoniae isolates identified in the crèche and in the orphanage belonged to the serotypes represented in the seven-valent pneumococcal vaccine, and 4.4% of the children were colonized by H. influenzae type b. Almost all H. influenzae isolates were fully susceptible to the antimicrobial agents tested, and only five (3.6%) produced beta-lactamase; in contrast, 100% of the M. catarrhalis isolates were beta-lactamase positive. Among S. pneumoniae isolates, 36.2% were nonsusceptible to penicillin (PNSP) and 11.8% were fully resistant to penicillin (PRP). All PNSP isolates were obtained from children at the crèche and at the orphanage but not among children brought up at home, and all PRP isolates showed a multiresistant phenotype. Colonization by PRP isolates correlated well with prior treatment with beta-lactams. For the majority of children colonized at both sampling times, strain replacement of S. pneumoniae and H. influenzae was observed; long-term colonization by a single strain was rare.

Beta-lactamase-producing nontypeable Haemophilus influenzae fails to protect Streptococcus pneumoniae from amoxicillin during experimental acute otitis media

Acute otitis media (AOM) is the most common reason for outpatient antimicrobial therapy. Mixed infections pose a potential problem, since the first-line drug used for the treatment of AOM, amoxicillin, can be neutralized by beta-lactamase-producing pathogens of the upper respiratory tract. To study the effects of a 5-day course of amoxicillin on a mixed middle ear infection, rats were challenged with Streptococcus pneumoniae alone or in combination with beta-lactamase-producing nontypeable Haemophilus influenzae. Amoxicillin was introduced at the clinical peak of the infection. Local and systemic changes were monitored by otomicroscopy, bacterial culture, and analysis of histological changes and the expression of the transforming growth factor beta (TGF-beta) gene. beta-Lactamase-producing H. influenzae did not demonstrate an ability to protect S. pneumoniae. Amoxicillin eradicated the pneumococci in all treated animals but increased to some degree the ability of H. influenzae to persist at the site of infection. Thus, only an insignificant acceleration of the resolution of the AOM caused by a mixture of pathogens was observed during treatment. Moderate to major morphological changes could not be avoided by treatment of the mixed infections, but a slight downregulation of TGF-beta expression was observed. In contrast to infections caused by a single pathogen, the mixed infections induced white plaques in the tympanic membrane at a remarkably high frequency independent of treatment. These experimental findings constitute support for further studies of antimicrobial drugs and AOM caused by bacteria with and without mechanisms of antibiotic resistance.

Structural and thermodynamic characterization of Pal, a phage natural chimeric lysin active against pneumococci

Pal amidase, encoded by pneumococcal bacteriophage Dp-1, represents one step beyond in the modular evolution of pneumococcal murein hydrolases. It exhibits the choline-binding module attaching pneumococcal lysins to the cell wall, but the catalytic module is different from those present in the amidases coded by the host or other pneumococcal phages. Pal is also an effective antimicrobial agent against Streptococcus pneumoniae that may constitute an alternative to antibiotic prophylaxis. The structural implications of Pal singular structure and their effect on the choline-amidase interactions have been examined by means of several techniques. Pal stability is maximum around pH 8.0 (Tm approximately 50.2 degrees C; DeltaHt = 183 +/- 4 kcal mol(-1)), and its constituting modules fold as two tight interacting cooperative units whose denaturation merges into a single process in the free amidase but may proceed as two well resolved events in the choline-bound state. Choline titration curves reflect low energy ligand-protein interactions and are compatible with two sets of sites. Choline binding strongly stabilizes the cell wall binding module, and the conformational stabilization is transmitted to the catalytic region. Moreover, the high proportion of aggregates formed by the unbound amidase together with choline preferential interaction with Pal dimers suggest the existence of marginally stable regions that would become stabilized through choline-protein interactions without significantly modifying Pal secondary structure. This structural rearrangement may underlie in vitro "conversion" of Pal from the low to the full activity form triggered by choline. The Pal catalytic module secondary structure could denote folding conservation within pneumococcal lytic amidases, but the number of functional choline binding sites is reduced (2-3 sites per monomer) when compared with pneumococcal LytA amidase (4-5 sites per monomer) and displays different intermodular interactions.

High‐Level Penicillin‐NonsusceptibleStreptococcus pneumoniaeBacteremia: Identification of a Low‐Risk Subgroup

High-level penicillin resistance has been associated with treatment failure in patients with Streptococcus pneumoniae infections. To identify a subgroup of patients at low risk for high-level penicillin-nonsusceptible S. pneumoniae bacteremia, a cross-sectional study of 303 patients was performed. For the total study population, penicillin resistance was observed in 98 (32%) of 303 patients; high-level resistance was seen in 33 (11%). A predictive model was created by using 3 baseline variables that were independently associated with high-level penicillin resistance: previous beta -lactam antibiotic use, previous stay in a risk area (defined as stay in day care facilities, prisons, homeless shelters, nursing homes, or other long-term care facilities), and previous respiratory tract infection. The model was used to identify patients at low and high risk for high-level penicillin-resistant pneumococcal bacteremia. None of the isolates of patients in the low-risk subgroup had ceftriaxone resistance. Patients in the low-risk subgroup could be empirically treated with fluoroquinolone-sparing regimens.

Mass antibiotic treatment for group A streptococcus outbreaks in two long-term care facilities

Outbreaks of invasive infections caused by group A β-hemolytic streptococcus (GAS) may occur in long-term care settings and are associated with a high case-fatality rate in debilitated adults. Targeted antibiotic treatment only to residents and staff known to be at specific risk of GAS may be an ineffective outbreak control measure. We describe two institutional outbreaks in which mass antibiotic treatment was used as a control measure. In the first instance, mass treatment was used after targeted antibiotic treatment was not successful. In the second instance, mass treatment was used to control a rapidly evolving outbreak with a high case-fatality rate. Although no further clinical cases were seen after the introduction of mass antibiotic treatment, persistence of the outbreak strain was documented in one institution >1 year after cases had ceased. Strain persistence was associated with the presence of a chronically colonized resident and poor infection control practices.

Structural Basis for Selective Recognition of Pneumococcal Cell Wall by Modular Endolysin from Phage Cp-1

Pneumococcal bacteriophage-encoded lysins are modular choline binding proteins that have been shown to act as enzymatic antimicrobial agents (enzybiotics) against streptococcal infections. Here we present the crystal structures of the free and choline bound states of the Cpl-1 lysin, encoded by the pneumococcal phage Cp-1. While the catalytic module displays an irregular (beta/alpha)(5)beta(3) barrel, the cell wall-anchoring module is formed by six similar choline binding repeats (ChBrs), arranged into two different structural regions: a left-handed superhelical domain configuring two choline binding sites, and a beta sheet domain that contributes in bringing together the whole structure. Crystallographic and site-directed mutagenesis studies allow us to propose a general catalytic mechanism for the whole glycoside hydrolase family 25. Our work provides the first complete structure of a member of the large family of choline binding proteins and reveals that ChBrs are versatile elements able to tune the evolution and specificity of the pneumococcal surface proteins.