Antibiotic resistance in Streptococcus pneumoniae

Antibiotic Prescribing for Patients with Upper Respiratory Tract Infections by Emergency Physicians in a Singapore Tertiary Hospital

Objective

Despite the paucity of supporting evidence, the use of antibiotics in the management of upper respiratory tract infections (URTI) remains a persistent and worrying trend worldwide. This survey study set out to examine the antibiotic prescribing profile of emergency physicians for patients diagnosed with URTI at a local tertiary hospital.

Methods

Patients seeking treatment for URTI at the emergency department in the year 2001 were identified by their ICD-9 code. The electronic medical records of a random sample of these patients were reviewed. Patients with the following documented findings were excluded: (a) a duration of more than 7 days between disease onset and date of consultation, (b) prior antibiotic usage or medical consultation, (c) presentation of purulent sputum and/or purulent nasal discharge, and (d) existing medical conditions requiring antibiotic treatment/prophylaxis. Chi-square and multivariate analyses were performed to assess the association of patient-related factors with antibiotic prescribing.

Results

Of a random sample of 488 cases of URTI, inappropriate antibiotic prescribing was observed in 24% of cases (95% CI 20%, 28%). Significant associations were observed between antibiotic prescribing and month of consultation, patients' temperature and symptom of rhinorrhoea.

Conclusion

A substantial proportion of emergency department patients with URTI received antibiotics despite the lack of evidence supporting the drugs' effectiveness. Appropriate interventions to promote evidence-based prescribing amongst emergency physicians are required to reduce the extent of inappropriate antibiotic prescribing as well as to ensure the longevity of antibiotic effectiveness.

The Queensland experience of participation in a national drug use evaluation project, Community-Acquired Pneumonia Towards Improving Outcomes Nationally (CAPTION)

Background

Multicentre drug use evaluations are described in the literature infrequently and usually publish only the results. The purpose of this paper is to describe the experience of Queensland hospitals participating in the Community-Acquired Pneumonia Towards Improving Outcomes Nationally (CAPTION) project, specifically evaluating the implementation of this project, detailing benefits and drawbacks of involvement in a national drug use evaluation program.

Methods

Emergency departments from nine hospitals in Queensland, Australia, participated in CAPTION, a national quality improvement project, conducted in 37 Australian hospitals. CAPTION was aimed at optimising prescribing in the management of Community-Acquired Pneumonia according to the recommendations of the Australian Therapeutic Guidelines: Antibiotic 12th edition. The project involved data collection, and evaluation, feedback of results and a suite of targeted educational interventions including audit and feedback, group presentations and academic detailing.

A baseline audit and two drug use evaluation cycles were conducted during the 2-year project. The implementation of the project was evaluated using feedback forms after each phase of the project (audit or intervention). At completion a group meeting with the hospital coordinators identified positive and negative elements of the project.

Results

Evaluation by hospitals of their participation in CAPTION demonstrated both benefits and drawbacks. The benefits were grouped into the impact on the hospital dynamic such as; improved interdisciplinary working relationships (e.g. between pharmacist and doctor), recognition of the educational/academic role of the pharmacist, creation of ED Pharmacist positions and enhanced involvement with the National Prescribing Service, and personal benefits. Personal benefits included academic detailing training for participants, improved communication skills and opportunities to present at conferences. The principal drawback of participation was the extra burden on already busy staff members.

Conclusion

A national multicentre drug use evaluation project such as CAPTION allows hospitals which would otherwise not undertake such projects the opportunity to participate. The Queensland arm of CAPTION demonstrated benefits to both the individual participants and their hospitals, highlighting the additional value of participating in a multicentre project of this type.

In vitro antibacterial activity of beta-lactams and non-beta-lactams against Streptococcus pneumoniae isolates from Sydney, Australia

AIMS

This study was undertaken to determine the antimicrobial resistance patterns of strains of Streptococcus pneumoniae from Sydney, Australia, comparing penicillin-susceptible, -intermediate and -resistant isolates.

METHODS

Non-duplicate cultures of S. pneumoniae were collected from 1 January to 31 December 2002 in the three penicillin-susceptibility categories. Minimum inhibitory concentrations (MICs) of 19 antibacterial agents were determined by agar dilution based on the National Committee for Clinical Laboratory Standards (NCCLS) methodology. Overall for 2002, 687 non-duplicate isolates were obtained, of which 190 (28%) were intermediate or resistant to penicillin. From this set, 183 isolates were selected for study: 88 (48%) in the penicillin-susceptible group (MIC <or= 0.06 mg/L), 25 (14%) in the penicillin-intermediate group (MIC 0.125-1.0 mg/L) and 70 (38%) in the penicillin-resistant group (MIC >or= 2.0 mg/L).

RESULTS

Resistance to non-beta-lactams was more common in penicillin-intermediate or -resistant strains. Multidrug resistance (resistance to >or= 2 non-beta-lactams) was found in 3% of penicillin-susceptible, 52% of penicillin-intermediate and 87% of penicillin-resistant isolates. Erythromycin resistance was seen in 22% of the penicillin-susceptible strains but increased significantly to 60% and 89% in the penicillin-intermediate and resistant strains, respectively. Clindamycin, tetracycline and trimethoprim/sulfamethoxazole showed similar diminished activity in penicillin-intermediate and -resistant strains; 64, 84 and 91% of the penicillin-resistant isolates were resistant to clindamycin, tetracycline and to trimethoprim/sulfamethoxazole, respectively. Chloramphenicol resistance was comparatively low level except 19% of the penicillin-resistant strains were resistant. Ciprofloxacin MICs for 14 strains were raised (MICs 4-16 mg/L); three of these were penicillin-susceptible, one penicillin-intermediate and 10 penicillin-resistant. Only one isolate was resistant to moxifloxacin and to gatifloxacin. Resistance to rifampicin, vancomycin, oritavancin, or linezolid was not detected. Twenty-three isolates were intermediate and one resistant to quinupristin/dalfopristin - 22 of these were penicillin resistant.

CONCLUSIONS

Streptococcus pneumoniae isolates from Sydney are commonly resistant to beta-lactams and available non-beta-lactam agents, especially if they are penicillin non-susceptible. Resistance to moxifloxacin and gatifloxacin is still rare, but some isolates were non-susceptible to quinupristin/dalfopristin. It is important to continue to survey resistance patterns to recognise emerging resistances which affect the selection of empirical antimicrobials to treat infections with S. pneumoniae.

Epidemiology of community-acquired and nosocomial bloodstream infections in tropical Australia: a 12-month prospective study

OBJECTIVES

To define the relative incidence of organisms causing blood stream infections in a tropical setting with a very low prevalence of human immunodeficiency virus infection (<1%).

METHODS

A 12-month prospective study of blood stream infections in 2000 at Royal Darwin Hospital in the tropical north of Australia.

RESULTS

Significant isolates were grown from 257 sets of blood cultures. Staphylococcus aureus was the most common isolate overall (28%); 26% of these were methicillin-resistant (MRSA). Escherichia coli was the most common cause of community-acquired bacteraemia. Burkholderia pseudomallei caused 32% of community acquired, bacteraemic pneumonia; 6% of bacteraemias overall. Vancomycin-resistant enterococci were not isolated. Crude mortality rates (13% overall; 9% attributable mortality) were lower than in most comparable studies.

CONCLUSIONS

The major difference between these findings and surveys performed elsewhere is the presence of B. pseudomallei as a significant cause of bacteraemic community-acquired pneumonia. Our results demonstrate the effects of local environmental and patient characteristics on the range of organisms causing blood stream infections, and emphasize the important role of local microbiology laboratories in guiding empiric antibiotic therapy.

Invasive pneumococcal disease in the Australian Capital Territory and Queanbeyan region: do high infant rates reflect more disease or better detection?

OBJECTIVE

To describe the epidemiology of invasive pneumococcal disease in the Australian Capital Territory (ACT) and Queanbeyan region prior to the introduction of conjugate pneumococcal vaccines.

METHODOLOGY

Residents with sterile site isolates of Streptococcus pneumoniae from 1998 to 2000 were identified from a prospective bacteraemia surveillance project involving all ACT public hospitals, supplemented by retrospective laboratory-based detection of other sterile site isolates.

RESULTS

Incidence of invasive pneumococcal disease was 15.2 cases per 105 per year, and 193.4 per 105 per year in infants under 2 years. Primary bacteraemia was significantly more common in infants and young children than in older subjects. Reduced penicillin susceptibility was observed in 9.6% of isolates, and no high-level penicillin resistance was observed.

CONCLUSIONS

Infants in the ACT and Queanbeyan have a higher invasive pneumococcal disease incidence than similar populations worldwide. Better detection is the most likely explanation. This population would be ideal for studies of the 'real life' effectiveness of infant conjugate vaccination.

Antibiotic treatment for bacterial meningitis in children in developing countries

Bacterial meningitis causes 125,000 deaths each year in infants and young children and 96% of these occur in less developed countries where up to 50% of children with this disease die and 25-50% of survivors have neurological sequelae. Although 3rd-generation cephalosporins are optimal empirical therapy for bacterial meningitis, they are unaffordable in many developing countries. The majority of children worldwide are currently treated with cheaper alternatives. This paper reviews the challenges facing clinicians treating bacterial meningitis in developing countries, highlighting the problem of changing patterns of antibiotic resistance. In particular, it details the evidence for the use of chloramphenicol and 3rd-generation cephalosporins.

The cost-effectiveness of pneumococcal conjugate vaccination in Australia

BACKGROUND

Pneumococcal conjugate vaccine, 7 valent (PCV7) is the most costly vaccine yet considered for publicly funded programs. In mid 2001, Australia funded PCV7 for high-risk groups only (indigenous children and children with certain underlying medical conditions). World wide, non-industry-funded studies and studies using cost-utility measures are sparse. We undertook an independent economic analysis of PCV7 compared with no vaccination in the non high-risk Australian childhood population using cost-utility and cost-effectiveness measures.

METHODS

The incidence of invasive pneumococcal disease (IPD), non-bacteraemic pneumonia and otitis media was estimated using representative urban Australian data, or by extrapolation from comparable industrialised countries. A decision-analytic model was developed for a hypothetical birth cohort using the age-specific vaccine coverage from the Californian randomised controlled trial of PCV7. Health outcomes were measured by life-years saved and deaths and disability-adjusted life-years (DALYs) averted. In line with government guidelines, only direct costs were considered in 1997-1998 Australian dollars.

RESULTS

For a birth cohort of 250,000, the gross cost of vaccination is $ 78.6 million. Subtracting treatment cost savings, the net cost (discounted) is $ 61.7 million. In undiscounted terms, vaccination prevents 13.7 deaths, 11.2 (82%) from IPD and the remainder from non-bacteraemic pneumonia. The discounted cost per death avoided is $ 5.0 million, per life-year saved $ 230,130 and per DALY averted $ 121,100, giving a break-even vaccine price of $ 15.40 per dose. These estimates are most sensitive to the unit cost per dose of vaccine, estimates of incidence and vaccine efficacy against non-bacteraemic pneumonia and the discount rate. The cost per DALY reduced to $ 81,000 with a discount rate of 3% rather than 5% and to $ 90,000 with the most favourable assumptions concerning pneumonia reduction.

DISCUSSION

With a vaccine price of $ 90 per dose, mid-range estimates of impact against non-bacteraemic pneumonia, and discount rate of 5%, a PCV7 program for infants not at high risk of IPD is at the upper limit of cost per DALY previously approved under Australian pharmaceutical funding guidelines. The impact of PCV7 against non-bacteraemic pneumonia is poorly defined, but its importance to cost-effectiveness in resource rich and resource poor settings warrants further studies or analysis to give greater precision to this outcome.

Prevention and management of antibacterial resistance for primary care patients with respiratory tract infections

This review examines the problem of increasing antibacterial resistance among the pathogens commonly associated with community-acquired respiratory tract infections, particularly Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. The increases in morbidity, mortality, and treatment cost associated with increased resistance to available antibiotics are challenging prescribers to find more effective therapeutic strategies. A MEDLINE search of the literature from 1966 to the present was performed to seek data relevant to the issue of resistance, especially the negative effects on patient outcomes and costs of therapy. Several observations and conclusions emerged. Data are lacking on local resistance patterns, broad-spectrum agents are overprescribed when narrower-spectrum choices would be more appropriate, a need exists for educational programs to encourage restricting drug use and changing prescribing habits, and there is a need for new antibiotic choices. The best antibiotic options are agents with a tailored spectrum of activity that are targeted at particular respiratory tract pathogens and have low potential to select for resistant organisms.

Implications for antimicrobial prescribing of strategies based on bacterial eradication

Antimicrobial prescribing in respiratory tract infection is generally empirical. Agents that do not eradicate the key bacterial respiratory pathogens (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis) provide suboptimal therapy. A recent paper developed by a multidisciplinary, multinational group presented a consensus on the principles that should underpin appropriate antimicrobial prescribing. In summary, in order to ensure clinical success and minimize the threat of resistance, empirical therapy should avoid unnecessary and inappropriate use of antimicrobials, deliver the right agent at the right dose and duration, and rapidly eradicate the pathogen at the site of infection. Accurate diagnosis is essential to ensure that only bacterial infections are treated with antibacterial agents. The application of pharmacokinetic/pharmacodynamic (PK/PD) principles to both new and existing antimicrobials allows the prediction of bacteriologic efficacy. Applying these principles when prescribing therapy can help in reducing the potential for the selection and spread of resistance. Local resistance patterns and the bacteriologic/clinical impact of resistance should also be considered. The use of antimicrobials with optimal PK/PD characteristics may be more cost-effective than allowing the possibility of resistance-induced failure. Changing prescribing habits without taking all these factors into account may increase the incidence of unfavorable patient outcomes and the cost of treatment, with more referrals and hospitalizations. Changes in prescribing habits should be considered carefully, to avoid unintended negative consequences. It is the responsibility of physicians to ensure that each prescription is necessary and will maximize the potential for clinical cure, but there is also a collective responsibility to sustain the diversity of antimicrobial therapy via appropriate formularies, guidelines and licensing, reduced over-the-counter availability, and continued research and development through academia and industry. To maximize clinical cure and minimize the emergence and spread of resistance, antimicrobial prescribing should maximize bacterial eradication, and clinical drug evaluation needs to be brought into line with this need.

The new pneumococcal vaccine

Pneumococcal disease is now the leading cause of vaccine-preventable bacterial disease in children worldwide. Although a pneumococcal polysaccharide vaccine has been available for over three decades, its use has been limited due to poor immunogenicity in the most vulnerable children, aged less than 2 years. The prevalence of pneumococcal disease worldwide and the alarming global escalation of multiresistant strains of Streptococcus pneumoniae (pneumococcus) during the past decade have provided the impetus for the development and application of a new pneumococcal vaccine. The outstanding success of Haemophilus influenzae type b (Hib) conjugate vaccine in the control of invasive Hib disease is a reason to be optimistic that the pneumococcal conjugate vaccines will achieve similar results for the control of invasive pneumococcal disease. Remarkable efficacy against invasive pneumococcal disease with a seven-valent pneumococcal conjugate vaccine was demonstrated in infants and toddlers in the USA, and in February 2000 the first pneumococcal conjugate vaccine was licensed. Licensure and widespread use is likely to follow in other countries in which there is a need and the means to afford this live-saving vaccine. Active disease surveillance must be sustained globally, while active research, development of other multivalent conjugate formulations and the search for new candidate protein-based vaccines are in progress.

Responsible prescribing for upper respiratory tract infections

Upper respiratory tract infections (URTIs) are responsible for a large amount of community antibacterial use worldwide. Recent systematic reviews have demonstrated that most URTIs resolve naturally, even when bacteria are the cause. The high consumer expectation for antibacterials in URTIs requires intervention by the general practitioner and a number of useful strategies have been developed. Generic strategies, including eliciting patient expectations, avoiding the term 'just a virus', providing a value-for-money consultation, providing verbal and written information, empowering patients, conditional prescribing, directed education campaigns, and emphasis on symptomatic treatments, should be used as well as discussion of alternative medicines when relevant. The various conditions have differing rates of bacterial infection and require different approaches. For acute rhinitis, laryngitis and tracheitis, viruses are the only cause and, therefore, antibacterials are never required. In acute sore throat (pharyngitis) Streptococcus pyogenes is the only important bacterial cause. A scoring system can help to increase the likelihood of distinguishing a streptococcal as opposed to viral infection, or alternatively patients should be given antibacterials only if certain conditions are fulfilled. Strategies for treating acute otitis media vary in different countries. Most favour the strategy of prescribing antibacterials only when certain criteria are fulfilled, delaying antibacterial prescribing for at least 24 hours. In otitis media with effusion, on the other hand, there is no primary role for antibacterials, as the condition resolves naturally in almost all patients aged >3 months. Detailed strategies for acute sinusitis have not been worked out but restricting antibacterial prescribing to certain clinical complexes is currently recommended by several authorities because of the high natural resolution rate.

Efficacy and effectiveness of pneumococcal polysaccharide vaccines and their use in industrialised countries

Use of pneumococcal polysaccharide vaccines remains controversial, even though clinical trials have shown their efficacy in preventing invasive disease caused by vaccine serotypes in immunocompetent adults. Retrospective studies indicate these vaccines have about 50%-80% effectiveness for preventing invasive disease caused by vaccine serotypes, although effectiveness wanes over time and with age. The elderly, people living in institutions and those with chronic cardiac or respiratory disease, alcoholism or diabetes mellitus who are in relatively good health would benefit from vaccination; a polysaccharide vaccine program in the elderly has been shown to be cost-effective. In young children, polysaccharide vaccine should be evaluated as a booster to conjugate pneumococcal vaccines, which are likely to be available soon in industrialised countries. In view of the high rates of hospitalisation and of antimicrobial resistance in pneumococci, every effort should be made to increase coverage by pneumococcal polysaccharide vaccine in Australia, according to guidelines of the National Health and Medical Research Council.