Prevalence of antibiotic resistance and serotypes in pneumococci in England and Wales: results of observational surveys in 1990 and 1995

Surveillance of antibiotic resistance

Surveillance involves the collection and analysis of data for the detection and monitoring of threats to public health. Surveillance should also inform as to the epidemiology of the threat and its burden in the population. A further key component of surveillance is the timely feedback of data to stakeholders with a view to generating action aimed at reducing or preventing the public health threat being monitored. Surveillance of antibiotic resistance involves the collection of antibiotic susceptibility test results undertaken by microbiology laboratories on bacteria isolated from clinical samples sent for investigation. Correlation of these data with demographic and clinical data for the patient populations from whom the pathogens were isolated gives insight into the underlying epidemiology and facilitates the formulation of rational interventions aimed at reducing the burden of resistance. This article describes a range of surveillance activities that have been undertaken in the UK over a number of years, together with current interventions being implemented. These activities are not only of national importance but form part of the international response to the global threat posed by antibiotic resistance.

Once or twice daily versus three times daily amoxicillin with or without clavulanate for the treatment of acute otitis media

BACKGROUND

Acute otitis media (AOM) is a common problem in children, for which amoxicillin, with or without clavulanate, is frequently prescribed as a treatment of choice. The conventional recommendation is either three or four daily doses. However, nowadays it is frequently prescribed as once or twice daily doses. If once or twice daily amoxicillin, with or without clavulanate, is as effective for acute otitis media as three or four times a day, it may be more convenient to give the medication once or twice a day to children and hence improve compliance.

OBJECTIVES

To compare the effectiveness of one or two daily doses with three or four daily doses of amoxicillin, with or without clavulanate, for the treatment of AOM in children; and to compare complication rates and adverse reactions.

SEARCH METHODS

We searched CENTRAL 2013, Issue 2, MEDLINE (January 1950 to March week 1, 2013), EMBASE (1974 to March 2013) and the Science Citation Index (2001 to March 2013).

SELECTION CRITERIA

We included randomised controlled trials (RCTs) of children aged 12 years or younger with AOM, diagnosed by acute ear pain (otalgia) and inflamed ear drum (confirmed by positive tympanocentesis or tympanogram of type B or C).

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on treatment outcomes from individual trials and assessed trial quality based on selection bias, performance bias and detection bias, attrition bias, reporting bias and other biases. We defined the quality grading as low risk of bias, high risk of bias or unclear risk of bias. We summarised the results as risk ratio (RR) with 95% confidence intervals (CI).

MAIN RESULTS

We included five studies with 1601 children in the review. Pooled analysis demonstrated that the following outcomes were comparable between the two groups: clinical cure at the end of therapy (RR 1.03, 95% CI 0.99 to 1.07); during therapy (RR 1.06, 95% CI 0.85 to 1.33) and at follow-up (RR 1.02, 95% CI 0.95 to 1.09); recurrent AOM (RR 1.21, 95% CI 0.52 to 2.81); compliance rate (RR 1.04, 95% CI 0.98 to 1.10) and overall adverse events (RR 0.92, 95% CI 0.52 to 1.63). When we performed subgroup analysis separately for trials with amoxicillin only and amoxicillin/clavulanate only, it showed that all important outcomes were comparable between once or twice daily groups and the three times daily group. The risk of bias amongst the five included studies was as follows: for random sequence generation we graded two studies as low and three unclear risk of bias; for allocation concealment all studies were at unclear risk of bias; for blinding (performance and detection bias) we graded four as high and one as unclear risk of bias; for incomplete outcome data (attrition bias) we graded two low, two high and one as unclear risk of bias; for reporting bias four were at low and one at high risk; and for 'other' bias four were at low and one at unclear risk of bias.

AUTHORS' CONCLUSIONS

This review showed that the results of using once or twice daily doses of amoxicillin, with or without clavulanate, were comparable with three doses for the treatment of AOM.

The British Society for Antimicrobial Chemotherapy Resistance Surveillance Project: a successful collaborative model

The British Society for Antimicrobial Chemotherapy (BSAC) Resistance Surveillance Project was initiated in light of the need for UK-wide surveillance of antibacterial resistance in key clinical pathogens. The Project comprises two defined-protocol programmes that cover a range of important pathogens and antibacterials related to community-acquired respiratory tract infection and bloodstream infection, respectively. The Respiratory Programme has reported quantitative susceptibility data for Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis collected from across the UK and Ireland since 1999. The Bacteraemia Programme has reported the susceptibility of a wide range of Gram-positive and -negative organisms since 2001. The sustainability of the Programmes relies on a unique collaborative funding model: sponsorship is provided by a number of pharmaceutical companies in return for the inclusion of their investigational or marketed agents in the study alongside a core panel of established antibacterials. The sponsors have changed over time according to their interest in participating. Results for marketed agents are communicated in a timely manner through the BSAC web site and by presentation and publication, and for investigational agents with the agreement of their sponsors. The Project satisfies the requirement for sustainable defined-protocol high-quality resistance surveillance across the UK and Ireland.

Once or twice daily versus three times daily amoxicillin with or without clavulanate for the treatment of acute otitis media

BACKGROUND

Acute otitis media (AOM) is a common problem in children, for which the antibiotic amoxicillin, with or without clavulanate, is frequently prescribed.

OBJECTIVES

To compare the effectiveness of one or two daily doses with three or four daily doses of amoxicillin, with or without clavulanate, for the treatment of AOM in children.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2008, issue 1), which contains the Acute Respiratory Infections (ARI) Group's Specialized Register; MEDLINE (January 1950 to March 2008); EMBASE (1974 to March 2008); the Science Citation Index (2001 to March 2008); and NLM Gateway (HSRProj) (March 2008).

SELECTION CRITERIA

We included studies if they met the following criteria: randomized controlled trials (RCTs) of children aged 12 years or younger with AOM, diagnosed by the following explicit criteria: acute ear pain (otalgia) and inflamed ear drum (confirmed by positive tympanocentesis or tympanogram of type B or C).

DATA COLLECTION AND ANALYSIS

We extracted data on treatment outcomes from individual trials. We assessed quality based on selection bias, performance bias, attrition bias and sample size calculation. The quality grading was defined as low risk of bias, moderate risk of bias or high risk of bias. The results were summarized as risk ratio (RR) and 95% confidence intervals (CI).

MAIN RESULTS

We included six studies with 1601 children in the review. Although the clinical cure rates at the end of therapy and at the follow-up periods of each study were shown to be comparable between the two groups, we did not perform pooled data analysis because of moderate to high risk of biases in the included studies. Most of the children were aged 2 months to 12 years. None of the studies had any consistently significant results either for benefit or harm. The outcomes were assessed at the end of therapy (often 10 days) and this may have been too late to measure any differences.

AUTHORS' CONCLUSIONS

This review showed insufficient evidence to judge whether once or twice daily doses of amoxicillin, with or without clavulanate, were comparable with three or four daily doses for the treatment of AOM. The evidence appears to be biased and therefore no firm conclusions can be drawn.

Factors associated with the presence of drug-resistant bacteria and recurrent acute otitis media in children--a study in a private clinic

CONCLUSIONS

The proportion of drug-resistant bacteria was lower than previous reports. In children with acute otitis media (AOM), lower age, presence of multiple bacteria, and otitis media with effusion (OME) represented significant factors for recurrent AOM and the presence of drug-resistant bacteria.

OBJECTIVE

Recently, the proportion of drug-resistant bacteria has been increasing in children with AOM. We studied the proportion of drug-resistant bacteria and background factors for detection of drug-resistant bacteria and recurrent AOM in a private clinic.

SUBJECTS AND METHODS

Subjects comprised 170 patients <12 years old with AOM. Middle ear fluid was collected and pathogenic bacteria were identified. The following factors were considered: age, sex, use of antibiotics in the past 1 month, past history of recurrent AOM, presence of OME, and multiple bacteria of the three main strains (Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis).

RESULTS

A total of 169 strains were detected in 77% of children with AOM. Drug-resistant bacteria comprised 44 of the 169 strains (26%). Lower age (p=0.001) and presence of multiple bacteria (p<0.001) represented significant factors for the presence of drug-resistant bacteria. OME was a significant factor for recurrent AOM (p<0.001).

Antimicrobial susceptibility of invasive isolates of Streptococcus pneumoniae in Ireland

Between January 1999 and June 2002, 646 invasive isolates of Streptococcus pneumoniae were collected in Ireland. MICs of penicillin, ciprofloxacin, cefotaxime, moxifloxacin and linezolid were determined by Etest methodology. Eighty-seven (13.5%) isolates showed intermediate resistance to penicillin, while seven (1.1%) showed high-level resistance. Eighty-seven (13.5%) isolates were resistant to erythromycin, but all isolates were susceptible to cefotaxime, moxifloxacin and linezolid. The prevalence of pneumococcal isolates non-susceptible to penicillin in Ireland is worryingly high, but currently there are alternative agents available to treat invasive infection.

Public knowledge, attitudes and behaviour regarding antibiotics--a survey of patients in general practice

OBJECTIVE

To assess public knowledge, attitudes and behaviour regarding antibiotics to provide information for a local health education policy.

DESIGN

Postal survey to 605 patients registered with two general medical practices in Grampian, North-East Scotland (351 respondents, 59.3%) in February/ March 2000. Questionnaire topics covered attitudes, knowledge and behaviour towards antibiotic use.

RESULTS

326 (93%) had experience of antibiotic use and 319 (81%) were happy to take antibiotics when necessary. 158 (45%) were concerned about antibiotic resistance. Few would expect antibiotics to treat a slight cold or heavy cold, but around half would expect antibiotics for very sore throats and influenza. 262 (75%) indicated they would ask a pharmacist for advice about the treatment of RTI. Most respondents experienced at least one episode of RTI during the review period. 280 (80%) provided details of their most recent episode; most self-treated, 57 consulted a doctor of whom 43 (75%) were prescribed antibiotics.

CONCLUSIONS

Antibiotic resistance is a matter of concern for the public. Mixed opinions about the use of antibiotics for common respiratory tract infections were heard. Encouragingly the majority of people suffering an RTI during the review period treated themselves with paracetamol-based products for symptom relief. Those who consulted a doctor were in the minority but were likely to be prescribed antibiotics. Future local health education initiatives should target antibiotic use for sore throats as well as colds and 'flu.

Presence of human herpesviruses in young children with acute otitis media

Some herpesviruses have been detected in middle ear fluid (MEF) of patients with acute otitis media (AOM), but their role in middle ear disease is unknown. We examined 73 middle ear fluid samples from 73 children with acute otitis media for the presence of four major herpesviral DNA, respiratory viral genomes, and bacterial DNA by multiplex polymerase chain reaction (PCR). Herpesviruses were detected in 16 specimens (22%), with 18 viral infections were identified overall. Respiratory viruses were detected in 35 specimens (48%), 39 viral infections overall. Bacterial DNA was detected in 51 specimens (70%), 60 bacterial infections overall. Clinical outcome was compared in patients with and without herpesvirus DNA, respiratory viral genomes, or bacterial DNA. Progression to otitis media with effusion (OME) was more common when herpesviral DNA was present. Presence of herpesvirus DNA may reflect an immunocompromised state that may make it difficult to eliminate bacteria from the middle ear after infection.

Effect of botulinum toxin type A on nasal symptoms in patients with allergic rhinitis: a double-blind, placebo-controlled clinical trial

OBJECTIVE

To investigate the possible beneficial effects of botulinum toxin type A (BTX-A) on nasal symptoms in patients with allergic rhinitis (AR).

MATERIAL AND METHODS

Thirty-four patients (21 females, 13 males; mean age 28 years) were included in the study. AR was diagnosed by means of history, clinical examination and skin prick test. Patients were randomly divided into 3 subgroups a follows: in Group A, 20 units of BTX-A was injected into each nasal cavity (total 40 units); in Group B, 30 units of BTX-A was injected into each nasal cavity (total 60 units); and in Group C, 2 ml of isotonic saline was injected as placebo. The symptoms of AR (rhinorrhea, nasal obstruction, sneezing, itching) were scored by the patient on a six-point scale (from 0 to 5). All of the patients were followed up at Weeks 1, 2, 4, 6 and 8; at each visit an anterior rhinoscopic examination was done and symptom scores were recorded.

RESULTS

There was no statistically significant difference between Groups A and B in terms of average symptom scores. Rhinorrhea, nasal obstruction and sneezing scores in Groups A and B were significantly better than those in Group C at all time points. Although itching scores were significantly lower at Weeks 1 and 2, there was no difference in the Week 4, 6 and 8 scores in Groups A and B. When total symptom scores were evaluated, the results for Groups A and B were similar but significantly better than those for Group C.

CONCLUSION

In selected cases, injection of 40 units of BTX-A into the turbinates, as a single agent, may help the symptomatic control of AR for up to 8 weeks.

Proteomics of bacterial pathogens

The rapid growth of proteomics that has been built upon the available bacterial genome sequences has opened provided new approaches to the analysis of bacterial functional genomics. In the study of pathogenic bacteria the combined technologies of genomics, proteomics and bioinformatics has provided valuable tools for the study of complex phenomena determined by the action of multiple gene sets. The review considers some of the recent developments in the establishment of proteomic databases as well as attempts to define pathogenic determinants at the level of the proteome for some of the major human pathogens. Proteomics can also provide practical applications through the identification of immunogenic proteins that may be potential vaccine targets as well as in extending our understanding of antibiotic action. There is little doubt that proteomics has provided us with new and valuable information on bacterial pathogens and will continue to be an important source of information in the coming years.

A common clone of erythromycin-resistant Streptococcus pneumoniae in Greece and the UK

OBJECTIVE

To investigate the possible genetic relationship among erythromycin-resistant Streptococcus pneumoniae strains isolated in Greece and the UK.

METHODS

During 1995-97, 140 S. pneumoniae strains were isolated from clinical specimens submitted to the microbiology departments of the two main children's hospital in Athens. All erythromycin-resistant strains were further studied with respect to the presence of genes encoding for the two major mechanisms of macrolide resistance, their serotypes, and pulsed-field gel electrophoresis (PFGE) types, in comparison to a previously characterized UK erythromycin-resistant clone.

RESULTS

Eleven of the 140 isolates (7.9%) were resistant to erythromycin; nine of these were susceptible to penicillin. Serotyping allocated seven, three and one isolates to serotypes 14, 19F and serogroup 6, respectively. The mefA gene was detected in seven isolates (five serotype 14 and two serotype 19F), ermB in two (one serotype 19F and the serogroup 6 isolate), whilst in the remaining two isolates no resistance gene could be detected by polymerase chain reaction (PCR). Pulsed-field gel electrophoresis of genomic DNA showed that five Greek serotype 14 isolates belonged to the same chromosomal type as the serotype 14 erythromycin-resistant UK clone.

CONCLUSIONS

The present study showed that erythromycin resistance among the S. pneumoniae isolates was mostly owing to the efflux mechanism and suggested a possible clonal spread of serotype 14 erythromycin-resistant S. pneumoniae strains between Greece and the UK.

Effect of a nonavalent conjugate vaccine on carriage of antibiotic-resistant Streptococcus pneumoniae in day-care centers

BACKGROUND

In the developed societies, day-care centers (DCCs) play an important role in the spread of antibiotic-resistant pneumococci both within the facility and from the facility to the community. This study was conducted to determine the effect of a nonavalent pneumococcal conjugate vaccine (PCV-9) on the carriage of antibiotic-resistant pneumococci in the DCC.

SUBJECTS AND METHODS

Healthy DCC attendees ages 12 to 35 months were randomized to receive either PCV-9 or a control vaccine (conjugate meningococcus C vaccine) in a double blinded manner. Nasopharyngeal Streptococcus pneumoniae cultures were obtained from each subject before vaccination, monthly during the first year of follow-up and every 2 to 3 months during the second year of follow-up. For each isolate the serotype and antibiotic susceptibility were determined.

RESULTS

A total of 132 and 130 evaluable toddlers received either PCV-9 or the control vaccine, respectively. In total 3748 cultures were obtained, of which 2450 (65%) were positive for S. pneumoniae. The resistance rates to penicillin, trimethoprim-sulfamethoxazole and erythromycin were 36, 35 and 16%, respectively. Resistance rates to > or =1 and > or =3 antibiotic categories were 52 and 9%, respectively. Antibiotic resistance was found mainly in the 5 serotypes included in the pneumococcal conjugate vaccines (6B, 9V, 14, 19F and 23F) and in 2 related serotypes (6A and 19A). In the vaccinated group a clear and significant reduction of the carriage rate of the serotypes included in the vaccine and the related serotype 6A as well as an increase in the carriage rate of the serotypes not included in the vaccine were observed. In parallel a significant decrease in carriage rate of antibiotic-resistant pneumococci was observed. The reduction of carriage of antibiotic-resistant pneumococci was seen in all age windows but was greater in the age window <36 months.

CONCLUSIONS

The carriage rate of antibiotic-resistant S. pneumoniae, including multiply resistant S. pneumoniae, in DCC attendees is high. Pneumococcal conjugate vaccines seem to be an important tool for reducing the carriage rate of antibiotic-resistant pneumonia in DCCs.

Molecular epidemiology of erythromycin resistance in Streptococcus pneumoniae isolates from blood and noninvasive sites

Erythromycin-resistant isolates of Streptococcus pneumoniae from blood cultures and noninvasive sites were studied over a 3-year period. The prevalence of erythromycin resistance was 11.9% (19 of 160) in blood culture isolates but 4.2% (60 of 1,435) in noninvasive-site isolates. Sixty-two of the 79 resistant isolates were available for study. The M phenotype was responsible for 76% (47 of 62) of resistance, largely due to a serotype 14 clone, characterized by multilocus sequence typing as ST9, which accounted for 79% (37 of 47) of M phenotype resistance. The ST9 clone was 4.8 times more common in blood than in noninvasive sites. All M phenotype isolates were PCR positive for mef(A), but sequencing revealed that the ST9 clone possessed the mef(A) sequence commonly associated with Streptococcus pyogenes. All M phenotype isolates with this mef(A) sequence also had sequences consistent with the presence of the Tn1207.1 genetic element inserted in the celB gene. In contrast, isolates with the mef(E) sequence normally associated with S. pneumoniae contained sequences consistent with the presence of the mega insertion element. All MLS(B) isolates carried erm(B), and two isolates carried both erm(B) and mef(E). Fourteen of the 15 MLS(B) isolates were tetracycline resistant and contained tet(M). However, six M phenotype isolates of serotypes 19 (two isolates) and 23 (four isolates) were also tetracycline resistant and contained tet(M). MICs for isolates with the mef(A) sequence were significantly higher than MICs for isolates with the mef(E) sequence (P < 0.001). Thus, the ST9 clone of S. pneumoniae is a significant cause of invasive pneumococcal disease in northeast Scotland and is the single most important contributor to M phenotype erythromycin resistance.

Antimicrobial susceptibility of Gram-positive bacteria: what's current, what's anticipated?

Changing patterns of pathogens and antibiotic susceptibility present clinicians with difficult choices for antimicrobial prescribing. In particular, multiresistant staphylococci, enterococci and pneumococci present problems in many settings. The number of predictably active antimicrobials is decreasing in many centres, with significant consequences for both patients and society as a whole. New antimicrobial options have been few in recent years and several promising quinolones have been compromised by formulation and/or toxicity issues. Nevertheless, the recent introduction of linezolid and quinupristin/dalfopristin provides clinicians with valuable new options against Gram-positive cocci. These options should further increase with the likely introduction of daptomycin, oritavancin and tigilcycline. A range of surveillance programmes helps monitor the ever-changing patterns of resistance and thus guides clinicians in their empirical prescribing. Empirical use of powerful newer agents may be justifiable in seriously ill patients in those settings, units and countries where there is a substantial background rate of resistance.

Activity of the ketolide telithromycin (HMR-3647) against erythromycin-susceptible and -resistant pneumococci isolated in the UK

The novel ketolide telithromycin (formerly HMR-3647) was tested against a collection of pneumococci of varying sensitivity to erythromycin and clindamycin, isolated in geographically diverse UK hospitals. Telithromycin was highly active against erythromycin-susceptible pneumococci, the MIC(90) being 0.015 mg/l. Erythromycin-resistant pneumococci that contained the ermB gene, either alone or together with the mefE gene, were cross-resistant to other macrolides and to clindamycin, while erythromycin-resistant pneumococci that contained only the mefE gene were cross-resistant to azithromycin, clarithromycin and roxithromycin but remained susceptible to josamycin and clindamycin. Telithromycin was active against erythromycin-resistant pneumococci irrespective of their mechanism of macrolide resistance, although the MIC(90) (0.25 mg/l) was higher than that seen with erythromycin-sensitive isolates. Telithromycin thus appears to be a potentially useful drug in settings where pneumococcal resistance to macrolides is prevalent.

National differences in incidence of acute mastoiditis: relationship to prescribing patterns of antibiotics for acute otitis media?

BACKGROUND

Operating on the principle that most acute otitis media (AOM) episodes resolve without antibiotics, doctors in the Netherlands usually manage AOM in children with initial observation. Prescription of antibiotics is limited to children with a complicated course of AOM and those categorized as high risk. Consequently only 31% of patients with AOM receives antibiotics, compared with >90% in most other countries.

OBJECTIVE

To substantiate the suggestion that this restrictive use of antibiotics leads to a higher incidence of acute mastoiditis.

METHODS

A comparative study across several European countries, Canada, Australia and the United States was performed in the period 1991 to 1998. The incidence rate of acute mastoiditis was defined as the total number of patients age 14 years and younger discharged from all hospitals with the primary diagnosis of acute mastoiditis, during a specified period (usually 5 years), divided by the number of person years (py) in that same age range and period. The latter was calculated by totaling the midyear population estimate of children age 14 years and younger of each year. The 95% confidence intervals and incidence rate ratios were calculated to compare the observed rates.

RESULTS

The incidence rate of acute mastoiditis in the Netherlands, with a low antibiotic prescription rate for AOM, was 3.8/100,000 py; in Norway and Denmark, with high prescription rates, the incidence rate was comparable at 3.5/100,000 py and 4.2/100,000 py, respectively. In all other countries with very high prescription rates, incidence rates were considerably lower, ranging from 1.2 to 2.0/100,000 py. The incidence rate in the Netherlands was about twice that in the United States (rate ratio, 0.5).

CONCLUSION

The incidence rate of acute mastoiditis in the Netherlands is higher than in many countries with higher antibiotic prescription rates. Although the potential benefits of restricted use of antibiotics (i.e. cost reduction, fewer side effects from antibiotics and less antimicrobial resistance) are beyond dispute, such strategy may be associated with a somewhat higher incidence of acute mastoiditis.

Quality measures of antimicrobial drug use

Antimicrobial use is the major determinant in the development of resistance. Many parameters of importance for optimal quality of antimicrobial therapy have already been defined. Maximal efficacy of the treatment should be combined with minimal toxicity at the lowest cost. Quality of antimicrobial drug use is dependent on knowledge of many aspects of infectious diseases. Considering efficacy, many of our indications for antimicrobial use need critical evaluation. Irrational use should be discouraged. Avoidance of the development of resistance is a quality parameter that will need increasing attention. This paper reviews the well-established factors that may influence the appropriateness of pharmacotherapy with antimicrobial drugs. It cites recent evidence supporting principles of prudent prescribing and gives an overview of audits that have addressed these parameters. Measures relating to resistance are discussed.

Antibiotic susceptibility and serotype distribution of Streptococcus pneumoniae causing meningitis in Italy, 1997-1999

Because few data are available in Italy regarding antimicrobial susceptibility and serotype distribution of invasive Streptococcus pneumoniae strains, meningeal isolates collected at Italian hospitals during the years 1997-1999 were studied. The 12 most common serogroups, representing > 85% of the isolates, were 14, 23, 6, 4, 3, 9, 19, 8, 1, 12, 18, and 7 (in order of frequency). The serogroups identified in children < 5 years old were more limited in number: 80% are included in the 7-valent conjugate vaccines. Penicillin resistance was observed in 14 (9.5%) of 148 strains and increased from 5% in the first part of the study to 13% in the last part. Only 2 strains were fully penicillin resistant, and these belonged to serotype 9V. Thirty percent of the strains, mostly belonging to serogroups 14 or 6 and carrying either the ermB or the mef genes, were resistant to erythromycin.

Recurrent penicillin-resistant pneumococcal sepsis after matched unrelated donor (MUD) transplantation for refractory T cell lymphoma

Patients who undergo splenectomy and recipients of allogeneic marrow (alloBMT) or peripheral stem cell transplantation are at increased risk of overwhelming infection from encapsulated organisms such as Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis. As prophylaxis against these pathogens splenectomised patients are immunised and may also receive antibiotics for life. We report relapsing overwhelming sepsis caused by penicillin-resistant pneumococcus in a patient who was immunised and received prophylactic phenoxymethylpenicillin for 8 months following splenectomy and matched unrelated donor (MUD) marrow transplantation for refractory T cell lymphoma. No obvious focus of sepsis was found during any of the three episodes and S. pneumoniae serogroup 6, subtype 6B was isolated from blood cultures on each occasion. He was treated with i.v. cephalosporins, as the organisms were resistant to penicillin with a minimum inhibitory concentration (MIC) of 2.0, and there was complete resolution of symptoms each time. In the light of recurrent sepsis with this penicillin-resistant organism the decision was made to give prophylactic levofloxacin for the next 12 months. This case illustrates that the choice of prophylactic regimen and the treatment of sepsis in immunocompromised patients remain difficult and challenging issues.

Rationalised prescribing for community acquired pneumonia: a closed loop audit

AIMS

To audit the management of community acquired pneumonia before and after the introduction of a protocol. To determine the aetiology of pneumonia using routine investigations and polymerase chain reaction (PCR).

METHODS

Retrospective and prospective audit following the introduction of a management protocol. Prospective cases were investigated routinely and with PCR on blood and nasopharyngeal aspirate.

RESULTS

There was a significant increase in rational prescribing following introduction of the protocol with 75% of children receiving intravenous penicillin or erythromycin compared with 26% beforehand. Of 89 children in the prospective group, 51 microbiological diagnoses were achieved in 48 children. Seven children had Streptococcus pneumoniae infection, 14 had Mycoplasma infection, six had pertussis, and one had Chlamydia pneumoniae infection. Twenty three children had a viral cause of which respiratory syncytial virus was commonest.

CONCLUSIONS

Introduction of the protocol led to improved prescribing. PCR increased the diagnostic yield and the results support the management protocol.

Proteomics in medical microbiology

The techniques of proteomics (high resolution two-dimensional electrophoresis and protein characterisation) are widely used for microbiological research to analyse global protein synthesis as an indicator of gene expression. The rapid progress in microbial proteomics has been achieved through the wide availability of whole genome sequences for a number of bacterial groups. Beyond providing a basic understanding of microbial gene expression, proteomics has also played a role in medical areas of microbiology. Progress has been made in the use of the techniques for investigating the epidemiology and taxonomy of human microbial pathogens, the identification of novel pathogenic mechanisms and the analysis of drug resistance. In each of these areas, proteomics has provided new insights that complement genomic-based investigations. This review describes the current progress in these research fields and highlights some of the technical challenges existing for the application of proteomics in medical microbiology. The latter concern the analysis of genetically heterogeneous bacterial populations and the integration of the proteomic and genomic data for these bacteria. The characterisation of the proteomes of bacterial pathogens growing in their natural hosts remains a future challenge.

Nosocomial antimicrobial resistance surveillance

The global threat of antimicrobial resistance and potentially untreatable infections is a serious matter under review currently by the WHO and many countries throughout the world. I consider the optimal surveillance scheme and point out the various biases in the systems that we have been using in the UK over the last decade. MRSA are used as an example where similar trends have been identified in these systems and the information has, once again, proved to be of value to the MRSA control working party.

Marked differences in pneumococcal carriage and resistance patterns between day care centers located within a small area

Carriage rates of Streptococcus pneumoniae and their antibiotic resistance, capsular types, and genetic patterns were studied among 264 children aged 12-35 months attending 8 day care centers located within a 2.5-mile radius in the same city. Nasopharyngeal cultures were obtained within a 2-month interval from all 264 children. Significant differences in each of the studied characteristics were found between day care centers, and each day care center had a unique pattern of the carried pneumococci. Our findings show that day care centers are independent microenvironments and emphasize their role in the transmission and augmentation of antibiotic-resistant S. pneumoniae in the community.

A 1-year study of antibiotic resistance among paediatric pneumococcal isolates in 1995 from four regions of France

The main object of this study was to describe the features of antibiotic resistance in pneumococci from children in four regions of France in 1995. Despite the high prevalence (40%) of pneumococci with diminished susceptibilty to penicillin (PDSP), resistance to amoxycillin (0.8%) and cefotaxime (0.4%) was rare; 16% of pneumococci were resistant to penicillin G (PRP, MIC > 1 mg/l). PDSP showed the expected resistance to macrolides (67%) and cotrimoxazole (57%) and were predominantly serotypes 23F, 14, 9 and 6. This study by the Regional Pneumococcal Observatories confirms the high prevalence and the main characteristics of antibiotic resistance among pneumococci isolated from children. Nevertheless, the resistance to all antibiotics was lower than that found in French multicentre, nationwide surveys, possibly because of differences in the mode of strain collection and geographic origin.

Patterns of macrolide resistance determinants among community-acquired Streptococcus pneumoniae isolates over a 5-year period of decreased macrolide susceptibility rates

Erythromycin resistance rates were found to be increased, from 7.1 in 1993 to 32.8% in 1997, among community-acquired Streptococcus pneumoniae isolates from the Siena area of central Italy. Most of the erythromycin-resistant isolates carried ermAM determinants and were also resistant to josamycin and clindamycin, whereas a minority (5.8%) carried mefA determinants and remained susceptible to the latter drugs.

A proteomic analysis of erythromycin resistance in Streptococcus pneumoniae

Streptococcus pneumoniae is a significant human pathogen which is an important cause of pneumonia and bacteraemia. Over the past few years the incidence of antibiotic resistance among clinical isolates of S. pneumoniae has increased. Penicillin resistance is now widespread and the frequency of isolates that are resistant to erythromycin has risen. Erythromycin resistance in S. pneumoniae follows two basic patterns. The MLS erythromycin-resistant phenotype is due to the enzymatic methylation of ribosomal RNA that blocks erythromycin binding to the ribosome. Alternatively, in isolates of the M phenotype, a more recently documented mechanism, resistance is associated with an active efflux process that reduces intracellular levels of erythromycin. We used two-dimensional electrophoresis to examine the proteins synthesised by erythromycin-susceptible and -resistant S. pneumoniae. Erythromycin-resistant S. pneumoniae with the M phenotype showed a significantly increased synthesis of a 38,500 Dalton (pI 6.27) protein compared to susceptible isolates. Peptide mass mapping was used to identify the 38,500 Dalton protein as glyceraldehyde-3-phosphate dehydrogenase (GAPDH). It was demonstrated that S. pneumoniae synthesised at least three forms of GAPDH that differed in their isoelectric points. The form of GAPDH possessing the most basic pI showed the increased synthesis in the erythromycin-resistant S. pneumoniae isolates. Alterations in the synthesis of GAPDH were only found for those erythromycin-resistant isolates possessing the M phenotype. S. pneumoniae isolates with the MLS phenotype were indistinguishable from the susceptible strains using the analytical conditions employed for the current study. The possible role of GAPDH in erythromycin resistance of S. pneumoniae is considered.

A possible secondary case of pneumococcal meningitis

Although institutional outbreaks of pneumococcal infection have been reported, secondary cases of pneumococcal meningitis do not seem to have been described. We report two cases of pneumococcal meningitis involving the same serotype occurring in individuals with direct contact.

Molecular epidemiology of penicillin-resistant Streptococcus pneumoniae isolates recovered in Italy from 1993 to 1996

Thirty-nine penicillin-resistant Streptococcus pneumoniae isolates recovered among the approximately 700 pneumococcal strains collected from 1993 to 1996 in central and northern Italy were analyzed for several characteristics, including serotype, antibiotic susceptibility profile, chromosomal relatedness (by using pulsed-field gel electrophoresis [PFGE]), restriction fragment length polymorphism (RFLP) of the penicillin-binding protein (PBP) genes 1A, 2X, and 2B, and the presence of a variety of antibiotic resistance genes (determined by hybridization with appropriate DNA probes). The MICs of penicillin for most of the isolates (30 of 39) were high, in the range of 1 microgram/ml or higher, and these 30 isolates carried additional resistance traits to two or more drugs (erythromycin, chloramphenicol, co-trimoxazole, and tetracycline) and expressed serotypes 9, 19, and 23 and three distinct PFGE patterns. More than half (22 of 30) of the isolates for which MICs were high were identified as representatives of two widespread international epidemic clones of S. pneumoniae. The first one of these clones (seven isolates) expressed serotype 23F and possessed all properties characteristic of the widespread Spanish/USA international clone. Seven additional strains with serotype 19 also had the same PFGE pattern, PBP gene, and RFLP polymorphisms, and other properties typical of the serotype 23 Spanish/USA clone, suggesting that these strains were the products of a capsular transformation event (from serotype 23F to serotype 19) in which the Spanish/USA clone was the recipient. The second international clone was represented by eight serotype 9 isolates which were resistant to penicillin and trimethoprim-sulfamethoxazole and had the molecular properties of the French/Spanish epidemic clone. The remaining eight isolates for which penicillin MICs were high appeared to represent a hitherto-undescribed "Italian" clone; they had a novel PFGE type, unique RFLPs for the PBP genes, and resistance to tetracycline, trimethoprim-sulfamethoxazole, and erythromycin, and the penicillin MICs for these isolates were 2 to 4 microgram/ml.

Antibiotic resistance among clinically important gram-positive bacteria in the UK

The resistance of bacteria to antibiotics, particularly those used for first-line therapy, is an increasing cause for concern. In the UK, the prevalence of resistance to methicillin and mupirocin in Staphylococcus aureus, and to penicillin and macrolides in Streptococcus pneumoniae, appear to be increasing. There has also been an increase in the number of hospitals where glycopeptide-resistant enterococci are known to have been isolated. The increases in methicillin-resistant S. aureus and glycopeptide-resistant enterococci are due, in part, to the inter-hospital spread of epidemic strains. Although new quinolones and streptogramins with activity against Gram-positive bacteria (including strains resistant to currently available agents) are under development, there is no reason to believe that resistance to these agents will not emerge. The control of resistance in Gram-positive bacteria will require a multi-faceted approach, including continued and improved surveillance, a reduction in the unnecessary use of antibiotics, and the application of other strategies such as vaccination.

Evaluation of in vitro activity of quinupristin/dalfopristin and comparator antimicrobial agents against worldwide clinical trial and other laboratory isolates

This report summarizes the activities of quinupristin/dalfopristin (Q/D) and appropriate comparator antibiotics, including ciprofloxacin, erythromycin, gentamicin, rifampin, teicoplanin, and vancomycin, against selected gram-positive pathogens, including Enterococcus faecium, Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus pneumoniae, Streptococcus agalactiae, and Streptococcus pyogenes. The study pathogens were obtained from 2 sources: (1) clinical isolates taken from patients participating in Q/D worldwide Phase III comparative and noncomparative (emergency-use program) clinical trials; and (2) other isolates collected from the laboratories of 45 geographically distinct medical centers around the world. Q/D was highly active, with minimum inhibitory concentrations (MICs) < or = 1.0 microg/mL against most isolates, including those known to be resistant to methicillin, vancomycin, or erythromycin. Q/D was active (MICs < or = 1 microg/mL) against 95% of the vancomycin-resistant E. faecium strains, for example, whereas ciprofloxacin was active against 6%. Q/D was equally active against methicillin-susceptible or -resistant S. aureus strains (MIC90=1 microg/mL), as was vancomycin (MIC90=2 microg/mL), whereas ciprofloxacin was much less active against methicillin-resistant strains than against methicillin-susceptible strains (MIC90=32 vs 1 microg/mL). Given its spectrum of activity, Q/D may provide a viable option for the treatment of severe respiratory and skin and skin-structure infections caused by gram-positive bacteria, especially when strains with known or suspected resistance to other commonly used antibiotics are present.

The population genetics of antibiotic resistance. II: Analytic theory for sustained populations of bacteria in a community of hosts

The phenomenon of antibiotic resistance is of practical importance and theoretical interest. As a foundation for further studies by simulation, experiment, and observation, we here develop a mathematical model for the dynamics of resistance among the bacteria resident in a population of hosts. The model incorporates the effects of natural selection within untreated hosts, colonization by bacteria from the environment, and the rapid increase of resistance in hosts who receive antibiotics. We derive explicit formulas for the distribution of resistance among hosts and for the rise or fall of resistance when the frequency of treatment is changed.

Practical considerations and guidelines for the management of community-acquired pneumonia

Community-acquired pneumonia (CAP) is a common condition which has a significant mortality. The management of a patient with CAP is centred around assessment and correction of gas exchange and fluid balance together with administration of appropriate antibiotics. Up to 10 different pathogens regularly cause CAP, of which Streptococcus pneumoniae is the most important. These different pathogens cannot be distinguished by clinical features or simple laboratory tests. Microbiological tests are slow and insensitive, so empirical therapy is necessary, at least initially. Accurate assessment of illness severity is the most important factor determining initial management, since this assists the decision of whether to admit the patient to hospital in addition to guiding antibiotic choice and route of administration. Two different approaches to severity assessment are outlined. Our antibiotic recommendation for empirical therapy for the patient managed at home and the previously fit patient admitted to hospital is amoxicillin. Amoxicillin/clavulanate plus a macrolide is our choice for the severely ill previously fit patient and a third-generation cephalosporin plus a macrolide is recommended for the severely ill patient with comorbidity. Alternative pathogens and specific treatment regimens are also described. There may be several causes of treatment failure, and in patients who fail to respond to therapy, it is essential to review all the initial clinical and laboratory information, which if necessary must be repeated.