Oral antibiotics for infective endocarditis: a clinical review

Current guidelines for management of infective endocarditis (IE) advise 4-6 weeks of IV antibiotics. This is based on historical data from animal models, which set a precedent for high peak serum antimicrobial levels, thought to be only achievable with IV therapy. However, there has been increasing recent interest in oral antibiotics as an alternative to prolonged parenteral therapy, not limited to treatment of IE. This review examines the theory behind parenteral antibiotic administration with reference to the MICs of relevant pathogens. By comparing published serum antimicrobial levels after oral and IV administration we suggest that safe levels of commonly used antibiotics can be achieved orally. We have then reviewed the literature to date on oral antibiotics for IE. The largest randomized controlled trial (RCT) in this area, the POET trial, concluded that oral therapy was non-inferior to prolonged IV therapy in stable patients with left-sided IE. Additionally, there have been two smaller RCTs published, as well as a number of observational studies over the last 50 years, utilizing a variety of different patient groups, methods and treatment strategies. This body of evidence gives weight to a potential shift in practice towards oral therapy, primarily as a step-down treatment. We conclude that pharmacological data offer theoretical reassurance for the safety of oral therapy. This is coupled with a growing evidence base for non-inferiority of oral antimicrobials compared with prolonged parenteral therapy in practice.

Modifiable healthcare factors affecting 28-day survival in bloodstream infection: a prospective cohort study

BACKGROUND

Bloodstream infection is common in the UK and has significant mortality depending on the pathogen involved, site of infection and other patient factors. Healthcare staffing and ward activity may also impact on outcomes in a range of conditions, however there is little specific National Health Service (NHS) data on the impact for patients with bloodstream infection. Bloodstream Infections - Focus on Outcomes is a multicentre cohort study with the primary aim of identifying modifiable risk factors for 28-day mortality in patients with bloodstream infection due to one of six key pathogens.

METHODS

Adults under the care of five NHS Trusts in England and Wales between November 2010 and May 2012 were included. Multivariable Cox regression was used to quantify the association between modifiable risk factors, including staffing levels and timing of appropriate therapy, and 28-day mortality, after adjusting for non-modifiable risk factors such as patient demographics and long-term comorbidities.

RESULTS

A total of 1676 patients were included in the analysis population. Overall, 348/1676 (20.8%) died within 28 days. Modifiable factors associated with 28-day mortality were ward speciality, ward activity (admissions and discharges), movement within ward speciality, movement from critical care, and time to receipt of appropriate antimicrobial therapy in the first 7 days. For each additional admission or discharge per 10 beds, the hazard increased by 4% (95% CI 1 to 6%) in medical wards and 11% (95% CI 4 to 19%) in critical care. Patients who had moved wards within speciality or who had moved out of a critical care ward had a reduction in hazard of mortality. In the first 7 days, hazard of death increased with increasing time to receipt of appropriate antimicrobial therapy.

CONCLUSION

This study underlines the importance of appropriate antimicrobials within the first 7 days, and the potential for ward activity and ward movements to impact on survival in bloodstream infection.

Impact of rapid microbial identification on clinical outcomes in bloodstream infection: the RAPIDO randomized trial

OBJECTIVES

Bloodstream infection has a high mortality rate. It is not clear whether laboratory-based rapid identification of the organisms involved would improve outcome.

METHODS

The RAPIDO trial was an open parallel-group multicentre randomized controlled trial. We tested all positive blood cultures from hospitalized adults by conventional methods of microbial identification and those from patients randomized (1:1) to rapid diagnosis in addition to matrix-assisted desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) performed directly on positive blood cultures. The only primary outcome was 28-day mortality. Clinical advice on patient management was provided to members of both groups by infection specialists.

RESULTS

First positive blood culture samples from 8628 patients were randomized, 4312 into rapid diagnosis and 4136 into conventional diagnosis. After prespecified postrandomization exclusions, 2740 in the rapid diagnosis arm and 2810 in the conventional arm were included in the mortality analysis. There was no significant difference in 28-day survival (81.5% 2233/2740 rapid vs. 82.3% 2313/2810 conventional; hazard ratio 1.05, 95% confidence interval 0.93-1.19, p 0.42). Microbial identification was quicker in the rapid diagnosis group (median (interquartile range) 38.5 (26.7-50.3) hours after blood sampling vs. 50.3 (47.1-72.9) hours after blood sampling, p < 0.01), but times to effective antimicrobial therapy were no shorter (respectively median (interquartile range) 24 (2-78) hours vs. 13 (2-69) hours). There were no significant differences in 7-day mortality or total antibiotic consumption; times to resolution of fever, discharge from hospital or de-escalation of broad-spectrum therapy or 28-day Clostridioides difficile incidence.

CONCLUSIONS

Rapid identification of bloodstream pathogens by MALDI-TOF MS in this trial did not reduce patient mortality despite delivering laboratory data to clinicians sooner.

In vitro effects of combined iron chelation, antibiotics and matrix disruption on clinical isolates of Pseudomonas aeruginosa

Objectives

Pseudomonas aeruginosa is an important pathogen in chronic suppurative respiratory diseases, with adverse effects on severity, healthcare utilization and quality of life. Aerosolized combined biofilm disruption and iron chelators offer novel proof-of-concept for improving airway antimicrobial efficacy. Our aim was to assess the activity of desferrioxamine, Dornase alfa (DNase) and antibiotics on biofilm formation and against mature preformed biofilms of P. aeruginosa.

Methods

Fifty-six isolates of P. aeruginosa were screened for biofilm production and seven isolates with varying capacity to form biofilms were referred for further study. Three antibiotics (colistin, tobramycin and ciprofloxacin) as well as desferrioxamine and DNase were assessed for their ability to prevent biofilm formation using the crystal violet assay. The same method was used to assess their impact on mature biofilms. Each agent, as well as combinations of these agents, was also assessed for its effect on the metabolic activity and viability of preformed P. aeruginosa biofilm by the resazurin reduction assay and by performing viable counts.

Results

Antibiotics alone prevented the development of biofilms and partly reduced the viability of mature biofilms. Desferrioxamine and DNase did not reduce biofilm formation. For most isolates, desferrioxamine and DNase did not offer any clear advantage over the use of antibiotics alone with respect to reducing the viability of Pseudomonas biofilms.

Conclusions

Colistin, tobramycin and ciprofloxacin prevented biofilm formation by P. aeruginosa and reduced the viability of mature biofilms. For most isolates, there was no clear advantage of combining these antimicrobials with desferrioxamine or DNase.

Outcomes of lung transplantation in adults with bronchiectasis

Background

Lung transplantation is a well-established treatment for end-stage non-cystic fibrosis bronchiectasis (BR), though information regarding outcomes of transplantation remains limited. Our results of lung transplantation for Br are reported here.

Methods

A retrospective review of case notes and transplantation databases was conducted for patients that had underwent lung transplantation for bronchiectasis at the Freeman Hospital between 1990 and 2013.

Results

Fourty two BR patients underwent lung transplantation, the majority (39) having bilateral sequential lung transplantation. Mean age at transplantation was 47.1 years. Pre-transplantation osteoporosis was a significant non-pulmonary morbidity (48%). Polymicrobial infection was common, with Pseudomonas aeruginosa infection frequently but not universally observed (67%). Forced expiratory volume in 1 second (% predicted) improved from a pre-transplantation mean of 0.71 L (22% predicted) to 2.56 L (79 % predicted) at 1-year post-transplantation. Our survival results were 74% at 1 year, 64% at 3 years, 61% at 5 years and 48% at 10 years. Sepsis was a common cause of early post-transplantation deaths.

Conclusions

Lung transplantation for end-stage BR is a useful therapeutic option, with good survival and lung function outcomes. Survival values were similar to other bilateral lung transplants at our centre. Pre-transplantation Pseudomonas infection is common.

Successful outcome following pneumonectomy in a teenage boy with cystic fibrosis: a case report

BACKGROUND

Cystic fibrosis lung disease is generally a diffuse process however rarely one lung may become particularly damaged through chronic collapse and consolidation resulting in end-stage bronchiectasis with relative sparing of the contralateral lung. This clinical situation is sometimes referred to as "destroyed lung". Lung resection surgery is seldom indicated in cystic fibrosis and the associated medical literature is relatively sparse.

CASE PRESENTATION

A 14 year old boy was referred to our centre for lung transplantation assessment. He had a chronic history of complete collapse and consolidation of his entire right lung. This was causing severe morbidity in terms of a continuous requirement for intravenous antibiotics over the last year, poor exercise tolerance with forced expiratory volume in 1 s of 35-40% predicted and need for home tuition. He also had significant nutritional problems and gastrointestinal symptoms following a Nissen's fundoplication operation a year earlier. His nutritional status was firstly improved by the institution of jejunal feeding, which also greatly improved his distressing symptoms of nausea and wretching. After thorough multidisciplinary assessment the therapeutic option of performing a right pneumonectomy was considered due to relative sparing of the left lung, which demonstrated only mild bronchiectasis on computed tomography scan. This was performed uneventfully with a smooth peri-operative course. Targeted antimicrobials were used to treat the multiresistant organisms colonising his airways. Subsequently his quality of life, nutritional status and lung function all improved significantly and requirement for lung transplantation has been delayed.

CONCLUSIONS

We report a successful outcome following pneumonectomy in a teenage boy with cystic fibrosis referred to our centre for lung transplantation assessment with chronic unilateral collapse and consolidation of his right lung. We believe that improvement of nutritional status pre-operatively and targeted antimicrobial therapy, all contributed to the smooth peri-operative course. Pneumonectomy can be a feasible option in this clinical situation in cystic fibrosis but the associated risks must be considered carefully on a case-by-case basis.

Cytomegalovirus as a cause of immunosuppression following aortic valve replacement

The postperfusion syndrome, haemolytic anaemia and thrombocytopenic purpura following open heart surgery have all been attributed to acute cytomegalovirus (CMV) infection,'-3 usually acquired from perioperative transfusions of whole blood. Increased susceptibility of bacterial infections has been described,4 but only in patients who have undergone cardiac transplantation and consequently received immunosuppressive therapy. Studies have shown that CMV can suppress cell-mediated immunity in vivo and in vitro5 and impairment of neutrophil migration has been demonstrated in CMV infected mice.6 We describe a patient with impaired polymorph function associated with an acute CMV infection following aortic valve replacement.

Comparison of two selective media for the recovery of Clostridium difficile from environmental surfaces

Two culture media were compared for their ability to isolate Clostridium difficile from environmental sites within a UK hospital. The media were cefoxitin-cycloserine-egg yolk agar plus lysozyme (CCEY/L) and chromID C. difficile. A wide range of environmental surfaces was sampled using sterile sponges (Polywipes) and these were inoculated on to both media. C. difficile was recovered from 105 of 496 sites (21%) using a combination of both media. The sensitivity of chromID C. difficile was 87.6% compared with 26.6% for CCEY/L (P < 0.0001). chromID C. difficile performed significantly better than CCEY/L for the recovery of C. difficile from the environment.

Epidemiological survey of Clostridium difficile ribotypes in the North East of England during an 18-month period

During an 18-month period, 1606 stool specimens from laboratory-confirmed cases of Clostridium difficile infection in the North East of England were ribotyped using unrestricted polymerase chain reaction. Of these, 87.6% grew C. difficile on culture; 70% had one of 10 recognizable ribotypes of which 001, 106 and 027 were the most prevalent. The proportions of ribotypes 002 and 015 declined during the study period, whereas ribotypes 016 and 023 increased. Ribotype 005 was significantly more numerous in males and ribotype 027 was associated with significantly higher mean age. Our findings differ from national data derived from more selective testing.

Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: a report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC guidelines on treatment of infectious endocarditis (IE) were last published in 2004. The guidelines presented here have been updated and extended to reflect developments in diagnostics, new trial data and the availability of new antibiotics. The aim of these guidelines, which cover both native valve and prosthetic valve endocarditis, is to standardize the initial investigation and treatment of IE. An extensive review of the literature using a number of different search criteria has been carried out and cited publications used to support any changes we have made to the existing guidelines. Publications referring to in vitro or animal models have only been cited if appropriate clinical data are not available. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking and therefore a consensus approach has again been adopted for most recommendations; however, we have attempted to grade the evidence, where possible. The guidelines have also been extended by the inclusion of sections on clinical diagnosis, echocardiography and surgery.

Guidelines for the diagnosis and antibiotic treatment of endocarditis in adults: a report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC guidelines on treatment of infectious endocarditis (IE) were last published in 2004. The guidelines presented here have been updated and extended to reflect developments in diagnostics, new trial data and the availability of new antibiotics. The aim of these guidelines, which cover both native valve and prosthetic valve endocarditis, is to standardize the initial investigation and treatment of IE. An extensive review of the literature using a number of different search criteria has been carried out and cited publications used to support any changes we have made to the existing guidelines. Publications referring to in vitro or animal models have only been cited if appropriate clinical data are not available. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking and therefore a consensus approach has again been adopted for most recommendations; however, we have attempted to grade the evidence, where possible. The guidelines have also been extended by the inclusion of sections on clinical diagnosis, echocardiography and surgery.

Linezolid: safety and efficacy in special populations

Linezolid has been in general use in the UK since 2000. Although toxicity, particularly haematological and neurological, has been an issue, linezolid has proved to be an effective alternative to glycopeptides in the treatment of Gram-positive infections. Since its original licence for the treatment of skin and soft tissue infections and pneumonia, there have been reports of its successful use in the treatment of bone and joint infections, endocarditis, and other difficult-to-treat infections.

Review of a three-year meticillin-resistant Staphylococcus aureus screening programme

The Newcastle upon Tyne Hospitals NHS Foundation Trust (NuTH) implemented a seek and destroy (S&D) programme in 2006 to minimise meticillin-resistant Staphylococcus aureus (MRSA) colonisation and/or infection of patients. Using a phased introduction, all patient specialties were included in the scheme by September 2008, well in advance of the mandatory Department of Health, England (DoH) requirement for all patients to be screened. NuTH screens nose, throat and perineum samples from approximately 15,000 patients per month using a chromogenic culture method, showing a mean MRSA prevalence of 2.4%. Provision of seven-day microbiology and infection control services ensured that the turnaround time to prescribing decolonisation therapy was <24 h. Analysis of 168,073 results identified the necessity for inclusion of all three screening sites to maximise recovery of MRSA. Appraisal of the S&D policy demonstrated that MRSA detection rates did not increase despite an exponential increase in workload owing to mandatory inclusion of low risk areas in the screening programme. Review of data during a typical one-month period indicated that only seven day-case patients would not have been identified as MRSA carriers using our targeted S&D approach compared with the DoH universal screening. Detection of these additional patients incurred total laboratory costs of £20,000 and generated a further 4200 associated negative screens in one month alone. Our study indicates that a screening strategy based upon clinical risk is more pragmatic and more cost-effective than the universal programme currently required in England.

Pseudomembranous colitis in four patients with cystic fibrosis following lung transplantation

In the present study, 4 patients with cystic fibrosis undergoing lung transplantation (from a total of 137) who developed fulminant pseudomembranous colitis are described. Initial presentation was variable and the mortality rate was 50% despite urgent colectomy. In one case the presenting abdominal distension was thought to be due to meconium ileus equivalent. It is concluded that Clostridium difficile colitis may be a difficult diagnosis in patients with cystic fibrosis and follows a fulminant course after lung transplantation.

Evaluation of chromogenic media for the isolation of vancomycin-resistant enterococci from stool samples

AIMS

This study sought to evaluate the performance of two chromogenic media designed for the isolation of vancomycin-resistant enterococci (VRE) and compare them with a traditional bile-esculin medium for the isolation of VRE from stool samples.

METHODS AND RESULTS

A total of 285 stool samples were inoculated onto Chromogenic VRE Agar (AES VRE agar; AES Chemunex), chromID VRE (bioMérieux) and VRE Agar (Oxoid) both directly and also following broth enrichment. In total 18 strains of vancomycin-resistant Enterococcus faecium were recovered, including 17 harbouring the vanA gene and one with vanB. On direct culture, the sensitivity of the three media was 66.7%, 77.8% and 44.4% and after broth enrichment 66.7%, 83.3% and 77.8% using AES VRE Agar, chromID VRE and Oxoid VRE Agar respectively.

CONCLUSIONS

All three media are useful tools for the isolation of VRE from stool samples. AES VRE Agar and bioMérieux chromID VRE are easier to use than Oxoid VRE Agar due to diffusion of black coloration from the latter.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to evaluate the performance of AES VRE Agar and the first to compare two media containing synthetic chromogens for the isolation of VRE.

Dental treatment and prosthetic joints: antibiotics are not the answer!

The routine administration of prophylactic antibiotics for dental interventions to prevent haematogenous spread of infections to prosthetic joints is a contentious issue. In this editorial we discuss the potentially harmful effects of this practice and propose an alternative solution.

Comparison of BD GeneOhm real-time polymerase chain reaction with chromogenic and conventional culture methods for detection of group B Streptococcus in clinical samples

A total of 200 antenatal high vaginal swabs were screened for the presence of group B Streptococcus (GBS) using a conventional culture method (recommended by Centers for Disease Control and Prevention). Screening was also performed by using a new chromogenic agar, chromID Strepto B, and by using the BD GeneOhm StrepB real-time polymerase chain reaction (PCR), which was performed directly on swabs without enrichment. Using a combination of all methods, we detected GBS in 101 samples. A total of 82 samples (81.2%) were positive using PCR, and 83 samples (82.2%) were confirmed as positive by culture (any method). PCR was more sensitive for detection of GBS than direct culture using any method (P < 0.0005). PCR was also more sensitive than any single enrichment method, but this difference was not statistically significant. With culture as a "gold standard", the PCR method showed a sensitivity of 77.1% and a positive predictive value of 79.3%. Of the culture-positive samples, significantly, more GBSs were detected by direct plating on chromID Strepto B than on selective sheep blood agar (67.5% versus 57% respectively, P < 0.02). After selective enrichment, 92.8% of GBS were isolated on chromID Strepto B compared with 89.2% isolated on sheep blood agar.

Revision of the 1996 working formulation for the standardization of nomenclature in the diagnosis of lung rejection

In 1990, an international grading scheme for the grading of pulmonary allograft rejection was adopted by the International Society for Heart and Lung Transplantation (ISHLT) and was modified in 1995 by an expanded group of pathologists. The original and revised classifications have served the lung transplant community well, facilitating communication between transplant centers with regard to both patient management and research. In 2006, under the direction of the ISHLT, a multi-disciplinary review of the biopsy grading system was undertaken to update the scheme, address inconsistencies of use, and consider the current knowledge of antibody-mediated rejection in the lung. This article summarizes the revised consensus classification of lung allograft rejection. In brief, acute rejection is based on perivascular and interstitial mononuclear infiltrates, Grade A0 (none), Grade A1 (minimal), Grade A2 (mild), Grade A3 (moderate) and Grade A4 (severe), as previously. The revised (R) categories of small airways inflammation, lymphocytic bronchiolitis, are as follows: Grade B0 (none), Grade B1R (low grade, 1996, B1 and B2), Grade B2R (high grade, 1996, B3 and B4) and BX (ungradeable). Chronic rejection, obliterative bronchiolitis (Grade C), is described as present (C1) or absent (C0), without reference to presence of inflammatory activity. Chronic vascular rejection is unchanged as Grade D. Recommendations are made for the evaluation of antibody-mediated rejection, recognizing that this is a controversial entity in the lung, less well developed and understood than in other solid-organ grafts, and with no consensus reached on diagnostic features. Differential diagnoses of acute rejection, airway inflammation and chronic rejection are described and technical considerations revisited. This consensus revision of the working formulation was approved by the ISHLT board of directors in April 2007.

Evaluation of novel chromogenic substrates for the detection of bacterial beta-glucosidase

AIMS

To evaluate three previously unreported substrates for the detection of beta-glucosidase activity in clinically relevant bacteria and to compare their performance with a range of known substrates in an agar medium.

METHODS AND RESULTS

The performance of 11 chromogenic beta-glucosidase substrates was compared using 109 Enterobacteriaceae strains, 40 enterococci and 20 strains of Listeria spp. Three previously unreported beta-glucosides were tested including derivatives of alizarin, 3',4'-dihydroxyflavone and 3-hydroxyflavone. These were compared with esculin and beta-glucoside derivatives of 3,4-cyclohexenoesculetin, 8-hydroxyquinoline and five indoxylics. All substrates yielded coloured precipitates upon hydrolysis in agar. Alizarin-beta-D-glucoside was the most sensitive substrate tested and detected beta-glucosidase activity in 72% of Enterobacteriaceae strains and all enterococci and Listeria spp. The two flavone derivatives showed poor sensitivity with Gram-negative bacteria but excellent sensitivity with enterococci and Listeria spp.

CONCLUSIONS

Alizarin-beta-d-glucoside is a highly sensitive substrate for detection of bacterial beta-glucosidase and compares favourably with existing substrates. beta-glucosides of 3',4'-dihydroxyflavone and 3-hydroxyflavone are effective substrates for the detection of beta-glucosidase in enterococci and Listeria spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data presented allow for informed decisions to be made regarding the optimal choice of beta-glucosidase substrate for detection of pathogenic and/or indicator bacteria.

Evaluation of a new chromogenic agar medium for isolation and identification of Group B streptococci

AIMS

To evaluate a new chromogenic agar as a screening medium for the isolation of Group B streptococci from high vaginal swabs from pregnant women.

METHODS AND RESULTS

The medium was evaluated with 195 high vaginal swabs referred for antenatal screening and compared with blood agar and Granada medium. The new chromogenic medium showed 100% sensitivity for the detection of Group B streptococci, and also showed a positive predictive value of 100%. Granada medium also showed excellent sensitivity and specificity and both media were superior to blood agar.

CONCLUSIONS

The new chromogenic medium showed excellent performance for the detection of Group B streptococci from clinical samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first chromogenic medium described for the detection of Group B streptococci. The medium offers an effective and convenient alternative to conventional media, currently used in clinical laboratories.

Evaluation of novel fluorogenic substrates for the detection of glycosidases in Escherichia coli and enterococci

AIMS

Enzyme substrates based on 4-methylumbelliferone are widely used for the detection of Escherichia coli and enterococci in water, by detection of beta-glucuronidase and beta-glucosidase activity respectively. This study aimed to synthesize and evaluate novel umbelliferone-based substrates with improved sensitivity for these two enzymes.

METHODS AND RESULTS

A novel beta-glucuronide derivative based on 6-chloro-4-methylumbelliferone (CMUG) was synthesized and compared with 4-methylumbelliferyl-beta-D-glucuronide (MUG) using 42 strains of E. coli in a modified membrane lauryl sulfate broth. Over 7 h of incubation, the fluorescence generated from the hydrolysis of CMUG by E. coli was over twice that from MUG, and all of the 38 glucuronidase-positive strains generated a higher fluorescence with CMUG compared with MUG. Neither substrate caused inhibition of bacterial growth in any of the tested strains. Four beta-glucosidase substrates were also synthesized and evaluated in comparison with 4-methylumbelliferyl-beta-D-glucoside (MU-GLU) using 42 strains of enterococci in glucose azide broth. The four substrates comprised beta-glucoside derivatives of umbelliferone-3-carboxylic acid and its methyl, ethyl and benzyl esters. Glucosides of the methyl, ethyl and benzyl esters of umbelliferone-3-carboxylic acid, were found to be superior to MU-GLU for the detection of enterococci, especially after 18 h of incubation, while umbelliferone-3-carboxylic acid-beta-D-glucoside was inferior. However, the variability in detectable beta-glucosidase activity among the different strains of enterococci in short-term assays using the three carboxylate esters (7 h incubation) may compromise their use for rapid detection and enumeration of these faecal indicator bacteria.

CONCLUSIONS

The beta-glucuronidase substrate CMUG appears to be a more promising detection system than the various beta-glucosidase substrates tested.

SIGNIFICANCE AND IMPACT OF THE STUDY

The novel substrate CMUG showed enhanced sensitivity for the detection of beta-glucuronidase-producing bacteria such as E. coli, with a clear potential for application in rapid assays for the detection of this indicator organism in natural water and other environmental samples.

Guidelines for the prevention of endocarditis: report of the Working Party of the British Society for Antimicrobial Chemotherapy

These guidelines have been produced following a literature review of the requirement for prophylaxis to prevent bacterial endocarditis following dental and surgical interventions. Recommendations are made based on the quality of available evidence and the consequent risk of morbidity and mortality for "at risk" patients.

Primary airway epithelial cell culture from lung transplant recipients

Long-term survival in lung transplantation is limited by the development of obliterative bronchiolitis, a condition characterised by inflammation, epithelial injury, fibroproliferation and obliteration of bronchioles leading to airflow obstruction. To investigate the role of the bronchial epithelium in the pathogenesis of obliterative bronchiolitis the current study aimed to establish primary bronchial epithelial cell cultures (PBEC) from lung allografts. Four to six bronchial brushings were obtained from sub-segmental bronchi of lung allografts. Cells were seeded onto collagen-coated plates and grown to confluence in bronchial epithelial growth medium. Bronchial brushings (n=33) were obtained from 27 patients. PBECs were grown to confluence from 12 out of 33 (39%) brushings. Failure to reach confluence was due to early innate infection. Bacteria were usually isolated from both bronchoalveolar lavage and culture media, but a separate population was identified in culture media only. Primary culture of bronchial epithelial cells from lung transplant recipients is feasible, despite a high rate of early, patient-derived infection. Latent infection of the allograft, identified only by bronchial brushings, may itself be a persistent stimulus for epithelial injury. This technique facilitates future mechanistic studies of airway epithelial responses in the pathogenesis of obliterative bronchiolitis.

Pseudomembranous colitis in four patients with cystic fibrosis following lung transplantation

Pseudomembranous colitis is an uncommon complication in patients with cystic fibrosis, despite the use of multiple high-dose antibiotic regimens and the frequency of hospital admissions. Four patients from a total of 137 patients with cystic fibrosis undergoing lung transplantation are described who developed fulminant pseudomembranous colitis. Initial presentation was variable and the mortality rate was 50% despite urgent colectomy. In one case the presenting abdominal distension was thought to be due to meconium ileus equivalent. It is concluded that Clostridium difficile colitis may be a difficult diagnosis in patients with cystic fibrosis and follows a fulminant course after lung transplantation.

Guidelines for the prophylaxis and treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections in the UK

These evidence-based guidelines have been produced after a literature review of the treatment and prophylaxis of methicillin-resistant Staphylococcus aureus (MRSA) infection. The guidelines were further informed by antibiotic susceptibility data on MRSA from the UK. Recommendations are given for the treatment of common infections caused by MRSA, elimination of MRSA from carriage sites and prophylaxis of surgical site infection. There are several antibiotics currently available that are suitable for use in the management of this problem and potentially useful new agents are continuing to emerge.

Germline mutational dynamics in myotonic dystrophy type 1 males: allele length and age effects

BACKGROUND

The CTG repeat expansion causing myotonic dystrophy type 1 is unstable in the germline, and frequent intergenerational length changes are observed, giving rise to the unusual genetics of the disorder. The repeat is also somatically unstable, and expanded alleles accumulate throughout life, thus compromising simple measures of intergenerational stability.

OBJECTIVE

To gain a better understanding of the intergenerational dynamics of the DM1 repeat in the male germline.

METHODS

We used sensitive small pool PCR procedures to analyze sperm and somatic DNA from 22 DM1 men of different ages, CTG repeat length, and clinical form.

RESULTS

High levels of repeat length variation heavily biased toward further expansions were observed in the sperm of all DM1 men. Progenitor allele length was revealed as a major modifier of interindividual variation, with the largest length changes observed for premutation and protomutation alleles and the highest frequency of contractions in full mutation alleles. However, despite clear increases in the degree of somatic mosaicism, no differences were observed in replicate sperm samples obtained from two men during a 4-year period.

CONCLUSIONS

Progenitor allele length is a major modifier of the mutational dynamics of the DM1 repeat in the male germline, but surprisingly age is not. Therefore, other as yet unidentified modifiers must be responsible for the considerable residual interindividual variation that cannot be accounted for by these factors.

Development and evaluation of a chromogenic agar medium for methicillin-resistant Staphylococcus aureus

We describe here the development and evaluation of MRSA ID, a new chromogenic agar medium for the specific isolation and identification of methicillin-resistant Staphylococcus aureus (MRSA). We used S. aureus ID (bioMerieux, La Balme Les Grottes, France) and supplemented it with various antimicrobials, including cefoxitin, ciprofloxacin, oxacillin, and methicillin. Cefoxitin proved to be superior to the other antimicrobials for the selection of MRSA from other strains of S. aureus. MRSA ID (consisting of S. aureus ID supplemented with 4 mg of cefoxitin/liter) was evaluated by the use of 747 swabs from various clinical sites. All specimens were also cultured on CHROMagar MRSA and oxacillin resistance screening agar base (ORSAB) and in selective mannitol broth (SMB). A total of 85 MRSA strains were isolated by a combination of all methods. After 22 to 24 h of incubation, 80% of the MRSA strains were isolated as green colonies on MRSA ID, compared with 59 and 62% of the strains that were isolated as colored colonies on CHROMagar MRSA and ORSAB, respectively. After 48 h of incubation, 89, 72, and 78% of the MRSA strains were isolated on MRSA ID, CHROMagar MRSA, and ORSAB, respectively. Sixty-five percent of the strains were isolated by growth in SMB. The specificities of MRSA ID, CHROMagar MRSA, ORSAB, and SMB were 99.5, 99.3, 97.9, and 92.8%, respectively, after 22 to 24 h of incubation. We conclude that MRSA ID is a sensitive and specific medium for the isolation and identification of MRSA.

Dynamic EBV gene loads in renal, hepatic, and cardiothoracic transplant recipients as determined by real-time PCR light cycler

BACKGROUND

Epstein-Barr virus (EBV) is recognised as one of the causative agents for most cases of post-transplant lymphoproliferative disease (PTLD). Elevated levels of EBV DNA are known to be associated with the onset of PTLD, but little information is available regarding how EBV loads change with time in asymptomatic transplant recipients following transplantation. Our aims were to study the trend of EBV loads in renal (RTx), hepatic, and cardiothoracic transplant recipients and to compare their EBV loads with other healthy and patient controls.

METHODS

A prospective study was performed using a real-time TaqMan polymerase chain reaction technique to measure EBV DNA loads from three types of organ transplant recipients and haemodialysis patients (HD). Their results were then compared with those from the healthy controls (HC); monospot test negative (MN-) and infectious mononucleosis positive (IM+) patients; patients who were previously treated for PTLD (pPTLD); those who were currently diagnosed to have PTLD (PTLD+); and patients who had a stable renal, hepatic, or cardiothoracic graft for more than a year.

RESULTS

Post-transplant EBV loads were significantly higher than the pre-transplant levels. Asymptomatic transplant recipients were differentiated from the PTLD+group at 600 genome copies of EBV/mug DNA, and from IM+group at 100 genome copies. Both HC and MN- groups had significantly lower EBV loads than the three transplant groups. The dynamic change of EBV loads in RTx was greater in the first post-transplant month when compared with the HD group. All transplant recipients had transient rises of EBV loads whereas EBV load continued to rise in one suspected PTLD patient.

CONCLUSIONS

Asymptomatic transplant recipients had higher baseline post-transplant EBV levels than the non-transplant and MN- groups. The rising post-transplant EBV load in these transplant recipients did not seem to be sustained for longer than 2 weeks. However, in a PTLD+patient the rising EBV load continued over a period of 4 weeks. Hence, the dynamic pattern of EBV loads is more important than absolute EBV DNA measurements alone in identifying those who might go on to develop PTLD.

Guidelines for the antibiotic treatment of endocarditis in adults: report of the Working Party of the British Society for Antimicrobial Chemotherapy

The BSAC Guidelines on Endocarditis were last published in 1998. The Guidelines presented here have been updated and extended to reflect changes in both the antibiotic resistance characteristics of causative organisms and the availability of new antibiotics. Randomized, controlled trials suitable for the development of evidenced-based guidelines in this area are still lacking, and therefore a consensus approach has again been adopted. The Guidelines cover diagnosis and laboratory testing, suitable antibiotic regimens and causative organisms. Special emphasis is placed on common causes of endocarditis, such as streptococci and staphylococci, however, other bacterial causes (such as enterococci, HACEK organisms, Coxiella and Bartonella) and fungi are considered. The special circumstances of prosthetic endocarditis are discussed.

Developing countries have their own characteristic problems with infection control

Infection control in developing countries differs markedly from that in the developed countries. It is important that both local and international authorities take these differences into account when formulating policies for use in developing countries. This review examines these issues and sets out some suggestions for improvements. The advantages of involving local experts in the development of such policies are emphasized.

Evaluation of novel beta-ribosidase substrates for the differentiation of Gram-negative bacteria

AIMS

To synthesize novel substrates for the detection of beta-ribosidase and assess their potential for the differentiation of Gram-negative bacteria.

METHODS AND RESULTS

Two novel chromogenic substrates, 3',4'-dihydroxyflavone-4'-beta-D-ribofuranoside (DHF-riboside) and 5-bromo-4-chloro-3-indolyl-beta-D-ribofuranoside (X-riboside) were evaluated along with a known fluorogenic substrate, 4-methylumbelliferyl-beta-D-ribofuranoside (4MU-riboside). A total of 543 Gram-negative bacilli were cultured on media containing either DHF-riboside or X-riboside. Hydrolysis of DHF-riboside or X-riboside resulted in the formation of clearly distinguishable black or blue-green colonies, respectively. Hydrolysis of 4MU-riboside was evaluated in a liquid medium in microtiter trays and yielded blue fluorescence on hydrolysis which was measured using fluorimetry. beta-Ribosidase activity was widespread with 75% of strains, including 85.6% of Enterobacteriaceae, showing activity with at least one substrate. Genera that demonstrated beta-ribosidase activity included Aeromonas, Citrobacter, Enterobacter, Escherichia, Hafnia, Klebsiella, Morganella, Providencia, Pseudomonas, Salmonella and Shigella. In contrast, strains of Proteus spp., Acinetobacter spp., Yersinia enterocolitica, Vibrio cholerae and Vibrio parahaemolyticus generally failed to demonstrate beta-ribosidase activity.

CONCLUSIONS

The novel substrates DHF-riboside and X-riboside are effective for the detection of beta-ribosidase in agar-based media and may be useful for the differentiation and identification of Gram-negative bacteria.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report describing the application and utility of chromogenic substrates for beta-ribosidase. These substrates could be applied in chromogenic media for differentiation of Gram-negative bacteria.

Evaluation of S. aureus ID, a new chromogenic agar medium for detection of Staphylococcus aureus

S. aureus ID (bioMérieux, La Balme Les Grottes, France) is a new chromogenic agar medium designed to enable the isolation of staphylococci and the specific identification of Staphylococcus aureus. S. aureus produces green colonies on this medium due to production of alpha-glucosidase. To evaluate this medium, a total of 350 wound swabs were cultured onto S. aureus ID, CHROMagar Staph. aureus, and conventional media routinely used in our laboratory. After 18 to 20 h of incubation, 96.8% of strains formed green colonies on S. aureus ID compared with 91.1% of strains forming mauve colonies on CHROMagar Staph. aureus. A total of 94.3% of strains were recovered within 18 to 20 h with conventional media. The sensitivity was increased after 48 h of incubation to 98.7, 96.2, and 95.6% with S. aureus ID, CHROMagar Staph. aureus, and conventional media, respectively. A total of 97.4% of green colonies on S. aureus ID were confirmed as S. aureus compared with 94.4% of mauve colonies on CHROMagar Staph. aureus. We conclude that S. aureus ID is a highly sensitive and specific medium for the isolation and identification of S. aureus from wound swabs.

Bacterial colonization of the donor lower airways is a predictor of poor outcome in lung transplantation☆

OBJECTIVE

At the time of lung transplant, we routinely perform bronchoalveolar lavage (BAL) of the donor lungs on the recipient operating table immediately before implantation, for bacterial and fungal cultures. We sought to determine whether the results correlate with the outcome.

METHODS

We retrospectively analysed 115 consecutive cadaveric lung transplants (single lung: 42; bilateral lung: 63; heart-lung: 10) performed over 4 years.

RESULTS

Fifty-three (46%) grafts had positive BAL (bacteria: 33; fungus: 10; mixed: 10) and 62 (54%) were negative. Recipients with donor BAL culture positive for bacteria had lower mean oxygenation index in the first 6 h compared with those with negative bacterial culture (36.5+/-14.73 vs. 44.1+/-16.79 kPa) (P=0.019). They also had longer median intensive treatment unit stay (2.5 vs. 1.5 days) (P=0.035), and median time of mechanical ventilation (37.5 vs. 23.0 h) (P=0.008), as well as inferior 6-month, 1-year, 2-year and 4-year cumulative survival (79, 77, 74, 60% vs. 93, 92, 88, 79% respectively) (P=0.04). There was no difference in the above parameters between recipients with Gram-negative (n=18) and recipients with Gram-positive bacteria (n=19) in the donor BAL. Incidence of acute rejection within the first 2 weeks and time of onset of bronchiolitis obliterans syndrome (BOS) were similar in the bacteria-positive and bacteria-negative groups. Recipients with donor BAL positive for fungi alone had similar outcome with the negatives. There was no difference in the donor oxygenation index and age, recipient age, transplant type and ischaemic time between compared groups. There was a significant difference in the median length of donor mechanical ventilation between donors with Gram-positive and donors with Gram-negative bacteria in the BAL (24 vs. 48 h) (P=0.01), as well as between donors with fungi alone in the BAL and donors with negative BAL (67 vs. 48 h) (P=0.04).

CONCLUSIONS

Donor lungs with lower airways colonized with bacteria result in inferior recipient outcome. Bacterial colonization of the donor lower airways could therefore be used as a marker of donor lung injury, but evidence from a prospective study is necessary.

Comparison of lung deposition of colomycin using the HaloLite and the Pari LC Plus nebulisers in patients with cystic fibrosis

AIM

To examine the effectiveness of delivery of nebulised colistin by the HaloLite nebuliser compared to the Pari LC Plus in patients with cystic fibrosis.

METHODS

Randomised crossover trial of 15 patients aged >6 years. Inhalation of one mega unit of colistin in 3 ml diluent, labelled with technetium-99m DTPA, was used to assess lung deposition. The Pari was nebulised to dryness and one button press of the HaloLite was completed. Following a seven day washout period, patients inhaled colistin twice daily for seven days through the first device. Sputum specimens were analysed for colistin levels and pseudomonas load. This procedure was repeated with the alternative device.

RESULTS

Lung uptake of radiolabelled colistin was significantly higher with the Pari. However, lung uptake calculated as a percentage of the amount of drug used was significantly higher for the HaloLite. Time to nebulise was significantly shorter with the HaloLite. Sputum levels of colistin were higher following use of the Pari; this was close to significance.

CONCLUSION

The manufacturer's recommended dosages for nebulising antibiotics with a HaloLite result in a lower delivery than patients receive when using a Pari nebuliser. The concept of adaptive aerosol delivery has several theoretical advantages but the recommended doses for the HaloLite need to be modified in order to improve effectiveness.

Use of real-time PCR to measure Epstein-Barr virus genomes in whole blood

The measurement of the Epstein-Barr viral load in peripheral blood has been recognised as an important way of monitoring the response to treatment in patients with Epstein-Barr virus (EBV)-related malignancies. In particular, EBV load in transplant recipients can be used as a predictive parameter for Post-transplant Lymphoproliferative Disorder (PTLD). The aim was to develop a rapid and reliable PCR protocol for the quantification of the cell-associated EBV genome. Real-time PCR using TaqMan methodology was established. This technique was applied to determine the EBV load in various study groups including healthy controls, transplant recipients, patients on haemodialysis, and patients with infectious mononucleosis. The baseline level of EBV genomes in the immunosuppressed renal transplant recipients was significantly different from that in the healthy controls.

Alafosfalin as a selective agent for isolation of salmonella from clinical samples

The selectivity of a range of culture media for the detection of Salmonella was assessed using 435 strains of gram-negative bacteria. These media showed limited ability to inhibit non-Salmonella strains found in stool samples. We report the evaluation of alafosfalin as a selective agent for isolation of Salmonella from stool samples. Susceptibility studies with this agent showed that non-typhi Salmonella strains were relatively resistant (mean MIC, 10.2 mg/liter) compared to many coliforms including Escherichia coli (mean MIC, 0.7 mg/liter). A chromogenic medium, ABC medium, was modified to incorporate alafosfalin and was compared with standard ABC medium and Hektoen enteric agar for the isolation of Salmonella from 1,000 stool samples. On direct culture, modified ABC medium showed higher recovery of Salmonella (53.6%) compared with either ABC medium (35.7%) or Hektoen enteric agar (48.2%). We conclude that alafosfalin is a useful selective agent for the isolation of Salmonella from stool samples.

Activity of disinfectants against Gram-negative bacilli isolated from patients undergoing lung transplantation for cystic fibrosis

Lung transplant recipients with cystic fibrosis are frequently colonized with antibiotic-resistant bacteria. We evaluated the in vitro activity of 5 disinfectants frequently used in cardiac surgery against strains of Burkholderia cepacia and Pseudomonas aeruginosa isolated from patients undergoing sequential single lung transplantation. Our results suggest that the activity of Taurolin and Noxyflex is superior to conventional disinfectants.

Role of aminoglycosides in the treatment of bacterial endocarditis

Aminoglycosides are often used in combination with glycopeptides and beta-lactams for the treatment of bacterial endocarditis caused by alpha-haemolytic streptococci, staphylococci and enterococci. Recommendations on dosing and duration of aminoglycoside therapy vary; we detail the laboratory and clinical evidence base for the treatment regimens advised. A number of deficiencies in the published guidelines are highlighted, as is the limited evidence base upon which many of the regimens are recommended. With the increasing use of outpatient treatment of severe infections and once daily administration of aminoglycosides the opportunity should be taken for larger, multicentre clinical trials to evaluate formally both old and new regimens.

Fluorogenic substrates for the detection of microbial nitroreductases

AIMS

To synthesize and evaluate fluorogenic substrates for the detection of microbial nitroreductases. These substrates, all based on 7-nitrocoumarin, may be reduced to form fluorescent aminocoumarins.

METHODS AND RESULTS

Thirty pathogenic microbial strains, including both bacteria and yeasts, were examined for nitroreductase activity in a whole-cell assay. All strains readily reduced each of the seven substrates to generate fluorescence, suggesting the widespread presence of nitroreductase activity in pathogenic bacteria.

CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY

These novel substrates facilitate the direct detection of nitroreductase activity and have potential as sensitive indicators of microbial growth.

Tuberculosis transmitted through transplantation

Tuberculosis in solid organ transplant recipients is associated with relatively high morbidity and mortality and is often extra-pulmonary. Reactivation of dormant infection is the usual mode of acquisition with donor and nosocomial transmission occurring infrequently. We report two cases of probable donor transmitted extra-pulmonary infection where both isolates of Mycobacterium tuberculosis proved to be indistinguishable using hemi-nested inverse PCR of the IS 6110 region.

Use of antibiotic locks to treat colonized central venous catheters

Infections that result from bacterial colonization of central venous catheters are a significant problem in modern healthcare. The most effective means of eradication of such infections is the removal of colonized lines, but line removal carries drawbacks of its own and in many cases the balance of risks favours treatment in situ. Systemic antibiotics are usually administered but these frequently fail to achieve sterilization, and accordingly attention has turned to intraluminal therapy using antibiotic locks, in which 1-2 mL of a concentrated antibiotic solution is instilled to fill the lumen, left for a predetermined period, and removed. The evidence in favour of this technique is anecdotal and should not be allowed to influence any decision about line removal, but is sufficiently encouraging to justify the use of locks when in situ treatment is deemed acceptable. Indications, agents and appropriate administration regimes are discussed.